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over 100,000 metric tons of caffeine are consumed around the world every year . that 's equivalent to the weight of 14 eiffel towers . most of this caffeine is consumed in coffee and tea , but it 's also ingested in some sodas , chocolate , caffeine pills , and even beverages labeled decaf . caffeine helps us feel alert , focused , happy , and energetic , even if we have n't had enough sleep . but it can also raise our blood pressure , and make us feel anxious . it 's the world most widely used drug . so how does it keep us awake ? caffeine evolved in plants where it serves a few purposes . in high doses , as it 's found in the leaves and seeds of certain species , it 's toxic to insects . but when they consume it in lower doses , as it 's found in nectar , it can actually help them remember and revisit flowers . in the human body , caffeine acts as a stimulant for the central nervous system . it keeps us awake by blocking one of the body 's key sleep-inducing molecules , a substance called adenosine . your body needs a constant supply of energy , which it gets by breaking down a high-energy molecule called atp . in the process , it liberates adenosine , atp 's chemical backbone . neurons in your brain have receptors perfectly tailored to this molecule . when adenosine docks to these receptors , it activates a cascade of biochemical reactions that cause neurons to fire more sluggishly and slow the release of important brain-signaling molecules . in other words , you get sleepy . caffeine is what 's called an adenosine receptor antagonist . that means it derails this process of slowing your neurons down by blocking adenosine receptors . caffeine and adenosine have a similar molecular structure , close enough that caffeine can wedge into the adenosine receptors , but not close enough to activate them . to summarize , adenosine inhibits your neurons . caffeine inhibits the inhibitor , so it stimulates you . caffeine can also boost positive feelings . in some neurons , the adenosine receptors are linked to receptors for another molecule called dopamine . one of dopamine 's roles in the brain is to promote feelings of pleasure . when adenosine docks in one of these paired receptors , that can make it harder for dopamine to fit in its own spot , interrupting its mood-lifting work . but when caffeine takes adenosine 's place , it does n't have the same effect , and dopamine can slide in . there 's evidence that caffeine 's effects on adenosine and dopamine receptors can have long-term benefits , too , reducing the risk of diseases like parkinson 's , alzheimer 's , and some types of cancer . caffeine can also ramp up the body 's ability to burn fat . in fact , some sports organizations think that caffeine gives athletes an unfair advantage and have placed limits on its consumption . from 1972 until 2004 , olympic athletes had to stay below a certain blood-caffeine concentration to compete . of course , not all of caffeine 's effects are so helpful . it might make you feel better and more alert , but it can also raise your heart rate and blood pressure , cause increased urination or diarrhea , and contribute to insomnia and anxiety . plus , the foods and beverages caffeine is found in have their own impacts on your body that have to be taken into account . your brain can adapt to regular consumption of caffeine . if your adenosine receptors are perpetually clogged , your body will manufacture extra ones . that way , even with caffeine around , adenosine can still do its job of signaling the brain to power down . that 's why you may find you need to consume more and more caffeine to feel as alert . there are more and more adenosine receptors to block . it 's also why if you suddenly quit caffeine , you may experience an unpleasant withdrawal . with plenty of receptors and no competition , adenosine can work overtime , causing symptoms like headaches , tiredness , and depressed moods . but in a few days , the extra adenosine receptors will disappear , your body will readjust , and you 'll feel just as alert as ever , even without an infusion of the world 's most popular stimulant .
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that 's equivalent to the weight of 14 eiffel towers . most of this caffeine is consumed in coffee and tea , but it 's also ingested in some sodas , chocolate , caffeine pills , and even beverages labeled decaf . caffeine helps us feel alert , focused , happy , and energetic , even if we have n't had enough sleep . but it can also raise our blood pressure , and make us feel anxious .
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many people consume chocolate when they feel down because it helps lift their mood . knowing that chocolate is a source of caffeine , explain how chocolate makes people happier .
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translator : jenny zurawell one of the funny things about owning a brain is that you have no control over the things that it gathers and holds onto , the facts and the stories . and as you get older , it only gets worse . things stick around for years sometimes before you understand why you 're interested in them , before you understand their import to you . here 's three of mine . when richard feynman was a young boy in queens , he went for a walk with his dad and his wagon and a ball . he noticed that when he pulled the wagon , the ball went to the back of the wagon . he asked his dad , `` why does the ball go to the back of the wagon ? '' and his dad said , `` that 's inertia . '' he said , `` what 's inertia ? '' and his dad said , `` ah . inertia is the name that scientists give to the phenomenon of the ball going to the back of the wagon . '' ( laughter ) `` but in truth , nobody really knows . '' feynman went on to earn degrees at mit , princeton , he solved the challenger disaster , he ended up winning the nobel prize in physics for his feynman diagrams , describing the movement of subatomic particles . and he credits that conversation with his father as giving him a sense that the simplest questions could carry you out to the edge of human knowledge , and that that 's where he wanted to play . and play he did . eratosthenes was the third librarian at the great library of alexandria , and he made many contributions to science . but the one he is most remembered for began in a letter that he received as the librarian , from the town of swenet , which was south of alexandria . the letter included this fact that stuck in eratosthenes ' mind , and the fact was that the writer said , at noon on the solstice , when he looked down this deep well , he could see his reflection at the bottom , and he could also see that his head was blocking the sun . i should tell you -- the idea that christopher columbus discovered that the world is spherical is total bull . it 's not true at all . in fact , everyone who was educated understood that the world was spherical since aristotle 's time . aristotle had proved it with a simple observation . he noticed that every time you saw the earth 's shadow on the moon , it was circular , and the only shape that constantly creates a circular shadow is a sphere , q.e.d . the earth is round . but nobody knew how big it was until eratosthenes got this letter with this fact . so he understood that the sun was directly above the city of swenet , because looking down a well , it was a straight line all the way down the well , right past the guy 's head up to the sun . eratosthenes knew another fact . he knew that a stick stuck in the ground in alexandria at the same time and the same day , at noon , the sun 's zenith , on the solstice , the sun cast a shadow that showed that it was 7.2 degrees off-axis . if you know the circumference of a circle , and you have two points on it , all you need to know is the distance between those two points , and you can extrapolate the circumference . 360 degrees divided by 7.2 equals 50 . i know it 's a little bit of a round number , and it makes me suspicious of this story too , but it 's a good story , so we 'll continue with it . he needed to know the distance between swenet and alexandria , which is good because eratosthenes was good at geography . in fact , he invented the word geography . ( laughter ) the road between swenet and alexandria was a road of commerce , and commerce needed to know how long it took to get there . it needed to know the exact distance , so he knew very precisely that the distance between the two cities was 500 miles . multiply that times 50 , you get 25,000 , which is within one percent of the actual diameter of the earth . he did this 2,200 years ago . now , we live in an age where multi-billion-dollar pieces of machinery are looking for the higgs boson . we 're discovering particles that may travel faster than the speed of light , and all of these discoveries are made possible by technology that 's been developed in the last few decades . but for most of human history , we had to discover these things using our eyes and our ears and our minds . armand fizeau was an experimental physicist in paris . his specialty was actually refining and confirming other people 's results , and this might sound like a bit of an also-ran , but in fact , this is the soul of science , because there is no such thing as a fact that can not be independently corroborated . and he was familiar with galileo 's experiments in trying to determine whether or not light had a speed . galileo had worked out this really wonderful experiment where he and his assistant had a lamp , each one of them was holding a lamp . galileo would open his lamp , and his assistant would open his . they got the timing down really good . they just knew their timing . and then they stood at two hilltops , two miles distant , and they did the same thing , on the assumption from galileo that if light had a discernible speed , he 'd notice a delay in the light coming back from his assistant 's lamp . but light was too fast for galileo . he was off by several orders of magnitude when he assumed that light was roughly ten times as fast as the speed of sound . fizeau was aware of this experiment . he lived in paris , and he set up two experimental stations , roughly 5.5 miles distant , in paris . and he solved this problem of galileo 's , and he did it with a really relatively trivial piece of equipment . he did it with one of these . i 'm going to put away the clicker for a second because i want to engage your brains in this . so this is a toothed wheel . it 's got a bunch of notches and it 's got a bunch of teeth . this was fizeau 's solution to sending discrete pulses of light . he put a beam behind one of these notches . if i point a beam through this notch at a mirror , five miles away , that beam is bouncing off the mirror and coming back to me through this notch . but something interesting happens as he spins the wheel faster . he notices that it seems like a door is starting to close on the light beam that 's coming back to his eye . why is that ? it 's because the pulse of light is not coming back through the same notch . it 's actually hitting a tooth . and he spins the wheel fast enough and he fully occludes the light . and then , based on the distance between the two stations and the speed of his wheel and the number of notches in the wheel , he calculates the speed of light to within two percent of its actual value . and he does this in 1849 . this is what really gets me going about science . whenever i 'm having trouble understanding a concept , i go back and i research the people that discovered that concept . i look at the story of how they came to understand it . what happens when you look at what the discoverers were thinking about when they made their discoveries , is you understand that they are not so different from us . we are all bags of meat and water . we all start with the same tools . i love the idea that different branches of science are called fields of study . most people think of science as a closed , black box , when in fact it is an open field . and we are all explorers . the people that made these discoveries just thought a little bit harder about what they were looking at , and they were a little bit more curious . and their curiosity changed the way people thought about the world , and thus it changed the world . they changed the world , and so can you . thank you . ( applause )
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he was off by several orders of magnitude when he assumed that light was roughly ten times as fast as the speed of sound . fizeau was aware of this experiment . he lived in paris , and he set up two experimental stations , roughly 5.5 miles distant , in paris .
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fizeau did this with simple equipment that included
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some superheros can move faster than the wind . the men in apollo 10 reached a record-breaking speed of around 25,000 miles per hour when the shuttle re-entered the earth 's atmosphere in 1969 . would n't we save a lot of time to be able to move that fast ? but what 's the catch ? air is not empty . elements like oxygen and nitrogen , even countless dust particles , make up the air around us . when we move past these things in the air , we 're rubbing against them and creating a lot of friction , which results in heat . just like rubbing your hands together warms them up or rubbing two sticks together makes fire , the faster objects rub together , the more heat is generated . so , if we 're running at 25,000 miles per hour , the heat from friction would burn our faces off . even if we somehow withstood the heat , the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time . ever seen the front bumper or grill of a truck ? what do you think all the birds and bugs would do to your open eyes or exposed skin ? okay , so you 'll wear a mask to avoid destroying your face . but what about people in buildings between you and your destination ? it takes us approximately one-fifth of a second to react to what we see . by the time we see what is ahead of us and react to it - time times velocity equals distance equals one-fifth of a second times 25,000 miles per hour equals 1.4 miles - we would have gone past it or through it by over a mile . we 're either going to kill ourselves by crashing into the nearest wall at super speed or , worse , if we 're indestructible , we 've essentially turned our bodies into missiles that destroy everything in our path . so , long distance travel at 25,000 miles per hour would leave us burning up , covered in bugs , and leaves no time to react . what about short bursts to a location we can see with no obstacles in between ? okay , let 's say a bullet is about to hit a beautiful damsel in distress . so , our hero swoops in at super speed , grabs her , and carries her to safety . that sounds very romantic , but , in reality , that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed . newton 's first law of motion deals with inertia , which is the resistance to a change in its state of motion . so , an object will continue moving or staying at the same place unless something changes it . acceleration is the rate the velocity changes over time . when the girl at rest , velocity equals zero miles per hour , begins accelerating to reach the speed within seconds , velocity increases rapidly to 25,000 miles per hour , her brain would crash into the side of her skull . and , when she stops suddenly , velocity decreases rapidly back to zero miles per hour , her brain would crash into the other side of her skull , turning her brain into mush . the brain is too fragile to handle the sudden movement . so is every part of her body , for that matter . remember , it 's not the speed that causes the damage because the astronauts survived apollo 10 , it 's the acceleration or sudden stop that causes our internal organs to crash into the front of our bodies the way we move forward in a bus when the driver slams on the brakes . what the hero did to the girl is mathematically the same as running her over with a space shuttle at maximum speed . she probably died instantly at the point of impact . he 's going to owe this poor girl 's family an apology and a big fat compensation check . oh , and possibly face jail time . doctors have to carry liability insurance just in case they make a mistake and hurt their patients . i wonder how much superhero insurance policy would cost . now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .
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just like rubbing your hands together warms them up or rubbing two sticks together makes fire , the faster objects rub together , the more heat is generated . so , if we 're running at 25,000 miles per hour , the heat from friction would burn our faces off . even if we somehow withstood the heat , the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time .
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what does friction create ?
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an enduring myth says we use only 10 % of our brain , the other 90 % standing idly by for spare capacity . hucksters promised to unlock that hidden potential with methods `` based on neuroscience , '' but all they really unlock is your wallet . two-thirds of the public and nearly half of science teachers mistakenly believe the 10 % myth . in the 1890s , william james , the father of american psychology , said , `` most of us do not meet our mental potential . '' james meant this as a challenge , not an indictment of scant brain usage . but the misunderstanding stuck . also , scientists could n't figure out for a long time the purpose of our massive frontal lobes or broad areas of the parietal lobe . damage did n't cause motor or sensory deficits , so authorities concluded they did n't do anything . for decades , these parts were called silent areas , their function elusive . we 've since learned that they underscore executive and integrative ability , without which , we would hardly be human . they are crucial to abstract reasoning , planning , weighing decisions and flexibly adapting to circumstances . the idea that 9/10 of your brain sits idly by in your skull looks silly when we calculate how the brain uses energy . rodent and canine brains consume 5 % of total body energy . monkey brains use 10 % . an adult human brain , which accounts for only 2 % of the body 's mass , consumes 20 % of daily glucose burned . in children , that figure is 50 % , and in infants , 60 % . this is far more than expected for their relative brain sizes , which scale in proportion to body size . human ones weigh 1.5 kilograms , elephant brains 5 kg , and whale brains 9 kg , yet on a per weight basis , humans pack in more neurons than any other species . this dense packing is what makes us so smart . there is a trade-off between body size and the number of neurons a primate , including us , can sustain . a 25 kg ape has to eat 8 hours a day to uphold a brain with 53 billion neurons . the invention of cooking , one and half million years ago , gave us a huge advantage . cooked food is rendered soft and predigested outside of the body . our guts more easily absorb its energy . cooking frees up time and provides more energy than if we ate food stuffs raw and so we can sustain brains with 86 billion densely packed neurons . 40 % more than the ape . here 's how it works . half the calories a brain burns go towards simply keeping the structure intact by pumping sodium and potassium ions across membranes to maintain an electrical charge . to do this , the brain has to be an energy hog . it consumes an astounding 3.4 x 10^21 atp molecules per minute , atp being the coal of the body 's furnace . the high cost of maintaining resting potentials in all 86 billion neurons means that little energy is left to propel signals down axons and across synapses , the nerve discharges that actually get things done . even if only a tiny percentage of neurons fired in a given region at any one time , the energy burden of generating spikes over the entire brain would be unsustainable . here 's where energy efficiency comes in . letting just a small proportion of cells signal at any one time , known as sparse coding , uses the least energy , but carries the most information . because the small number of signals have thousands of possible paths by which to distribute themselves . a drawback of sparse coding within a huge number of neurons is its cost . worse , if a big proportion of cells never fire , then they are superfluous and evolution should have jettisoned them long ago . the solution is to find the optimum proportion of cells that the brain can have active at once . for maximum efficiency , between 1 % and 16 % of cells should be active at any given moment . this is the energy limit we have to live with in order to be conscious at all . the need to conserve resources is the reason most of the brain 's operations must happen outside of consciousness . it 's why multitasking is a fool 's errand . we simply lack the energy to do two things at once , let alone three or five . when we try , we do each task less well than if we had given it our full attention . the numbers are against us . your brain is already smart and powerful . so powerful that it needs a lot of power to stay powerful . and so smart that it has built in an energy-efficiency plan . so do n't let a fraudulent myth make you guilty about your supposedly lazy brain . guilt would be a waste of energy . after all this , do n't you realize it 's dumb to waste mental energy ? you have billions of power-hungry neurons to maintain . so hop to it !
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half the calories a brain burns go towards simply keeping the structure intact by pumping sodium and potassium ions across membranes to maintain an electrical charge . to do this , the brain has to be an energy hog . it consumes an astounding 3.4 x 10^21 atp molecules per minute , atp being the coal of the body 's furnace .
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to what is most the brain ’ s energy devoted ?
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it starts with a cough , or a wheeze . soon , your chest feels tight . your breathing speeds up and gets shallower , making you feel short of breath . these are common symptoms of an asthma attack . around the world , more than 300 million people suffer from asthma , and around 250,000 people die from it each year . but why do people get asthma and how can this disease be deadly ? asthma affects the respiratory system , particularly the smaller airways , such as the bronchi and bronchioles . these airways have an inner lining called the mucosa that 's surrounded by a layer of smooth muscle . in people with asthma , the airways are chronically inflamed , which can make them hyper-responsive to certain triggers . some of the many asthma triggers include tobacco smoke , pollen , dust , fragrances , exercise , cold weather , stress , and even the common cold . when people with asthma are exposed to these triggers , an asthma attack , or exacerbation , can occur . but how exactly do such everyday factors lead to an asthma attack ? if an asthmatic is exposed to a trigger , the smooth rings of muscle that circle the small airways in their lungs contract and become narrow . simultaneously , the trigger worsens inflammation , causing the mucosal lining to become more swollen and secrete more mucus . under normal conditions , the body uses this mucus to trap and clear particles , like pollen or dust , but during an asthma attack , it blocks the narrowed airways , making it even harder to breathe . these effects lead to this symptoms of asthma . smooth muscle constriction results in the feeling of chest tightness . excess mucus and increased inflammation can cause coughing . and the wheezing noise ? that happens because as the airways constrict , air whistles as it passes through the narrowed space . these symptoms may make a person feel like they 're running out of air . yet counterintuitively , during an asthma attack , the inflammation can make it harder to exhale than inhale . over time , this leads to an excess of air in the lungs , a phenomenon known as hyperinflation . the trapping of air inside the lungs forces the body to work harder to move air in and out of them . over time , this can lead to reduced oxygen delivery to the body 's organs and tissues . sometimes , in untreated severe asthma attacks , the body ca n't keep up , which can lead to death from lack of oxygen . so how do we prevent these uncomfortable and potentially fatal attacks in people who have asthma ? one way is to reduce the presence of triggers . unfortunately , the world is an unpredictable place and exposure to triggers ca n't always be controlled . this is where inhalers , the primary treatment for asthma , come in . these medications help asthmatics both control and prevent their asthma symptoms . inhalers transport medication along the affected airways using a liquid mist or fine powder to treat the problem at its source . they come in two forms . there are reliever medications , which treat symptoms immediately and contain beta-agonists . beta-agonists relax constricted muslces , allowing the airways to widen so more air can travel into and out of the lungs . the other form of inhalers serve as preventive medications , which treat asthma symptoms over the long term , and contain corticosteroids . corticosteroids reduce airway sensitivity and inflammation , so asthma can be kept under control . they 're also crucial in preventing long-term damage from chronic inflammation , which can cause scarring of the airways . inhalers are known to be very effective , and have helped many people live better lives . although we 've come a long way in improving how we treat and diagnose asthma , we still do n't know its exact causes . we currently believe that a combination of genetic and environmental factors play a role , potentially acting during early childhood . recent research has even linked poverty to asthma incidents . this may be due to reasons ranging from exposure to additional pollutants and environmental irritants to difficulties in obtaining medical care or treatment . as our understanding of asthma improves , we can continue to find better ways to keep people 's airways happy and healthy .
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unfortunately , the world is an unpredictable place and exposure to triggers ca n't always be controlled . this is where inhalers , the primary treatment for asthma , come in . these medications help asthmatics both control and prevent their asthma symptoms . inhalers transport medication along the affected airways using a liquid mist or fine powder to treat the problem at its source .
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how do beta-agonist inhalers help relieve the symptoms of asthma ?
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we have some good reasons to completely switch over to solar power . it 's cheaper in many cases , and definitely more sustainable than our dependance on traditional power plants that use resources like coal , which will eventually run out . so why do n't we replace these traditional plants with solar energy ? because there 's one factor that makes solar power very unpredictable : cloud cover . as the sun 's rays move towards earth , some get absorbed by the earth 's atmosphere , some are reflected back into outer space , but the rest make it to the earth 's surface . the ones that are n't deviated are called direct irradiance . the ones that are deflected by clouds are called diffuse irradiance . and those rays that first get reflected by a surface , like a nearby building , before reaching the solar energy system are called reflected irradiance . but before we can examine how clouds affect the sun 's rays and electricity production , let 's see how these solar energy systems work . first up , we have solar towers . these are made up of a central tower surrounded by a huge field of mirrors that track the sun 's path and focus only the direct rays onto a single point on the tower , kind of like an eager beachgoer . the heat generated by these rays is so immense that it can be used to boil water producing steam that drives a traditional turbine , which makes electricity . but when we say solar energy systems , we 're usually talking about photovoltaics , or solar panels , which are the systems most commonly used to generate solar power . in solar panels , photons from the sun 's rays hit the surface of a panel , and electrons are released to get an electric current going . solar panels can use all types of irradiance , while solar towers can only use direct irradiance , and this is where clouds become important because depending on their type and location relative to the sun , they can either increase or decrease the amount of electricity produced . for instance , even a few cumulus clouds in front of the sun can reduce the electricity production in solar towers to almost zero because of this dependence on direct rays . in solar panels , those clouds would decrease energy output as well , though not as much because solar panels can use all types of irradiance . however , all this depends on the clouds exact positioning . due to reflection , or a particular phenomeon called mie scattering , the sun 's rays can actually be focused forward by clouds to create a more than 50 % increase in the solar irradiance reaching a solar panel . if this potential increase is n't accounted for , it could damage the solar panel . why does this matter ? well , you would n't want this lesson to stop just because a cloud passed over the panel on your roof . in solar towers , huge tanks of molten salt or oil can be used to store any excess heat and use it when needed , so that 's how they manage the problem of fluctuating solar irradiance to smooth out electricity production . but in the case of solar panels , there currently is n't any way to affordably store extra energy . that 's where traditional power plants come in because to correct for any fluctuations in these solar powered plants , extra electricity from traditional sources always needs to be available . but then why are n't these tradtional power plants just used as a backup , instead of us humans depending on them as our main sources of energy ? because it 's impossible for an employee at a coal fired or a nuclear plant to turn a knob to produce more or less electricity depending on how many clouds there are in the sky . the response time would simply be too slow . instead , to accommodate these fluctuations , some extra electricity from traditional power plants is always being produced . on clear sky days , that extra electricity might be wasted , but when cloudy skies prevail , it 's what fills the gap . this is what we currently depend on for a constant supply of energy . for this reason , a lot of researchers are interested in forcasting the motion and formation of clouds through satellite images or cameras that look up at the sky to maximize the energy from solar power plants and minimize energy waste . if we could accomplish that , you 'd be able to enjoy this video powered solely by the sun 's rays , no matter what the weather , although if the sun is shining , you may be tempted to venture outside to go and do a different kind of cloud gazing .
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it 's cheaper in many cases , and definitely more sustainable than our dependance on traditional power plants that use resources like coal , which will eventually run out . so why do n't we replace these traditional plants with solar energy ? because there 's one factor that makes solar power very unpredictable : cloud cover . as the sun 's rays move towards earth , some get absorbed by the earth 's atmosphere , some are reflected back into outer space , but the rest make it to the earth 's surface .
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which one the countries below has the highest solar irradiance potential ?
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translator : andrea mcdonough reviewer : bedirhan cinar deep in the jungles of vietnam , soldiers from both sides battled heat exhaustion and each other for nearly 20 long years . but the key to communist victory was n't weapons or stamina , it was a dirt road . the ho chi minh trail , winding through vietnam , laos , and cambodia , started as a simple network of dirt roads and blossomed into the centerpiece of the winning north vietnamese strategy during the vietnam war , supplying weapons , troops , and psychological support to the south . the trail was a network of tracks , dirt roads , and river crossings that threaded west out of north vietnam and south along the truong son mountain range between vietnam and laos . the journey to the south originally took six months . but , with engineering and ingenuity , the vietnamese expanded and improved the trail . towards the end of war , as the main roads detoured through laos , it only took one week . here is how it happened . in 1959 , as relations deteriorated between the north and the south , a system of trails was constructed in order to infiltrate soldiers , weapons , and supplies into south vietnam . the first troops moved in single-file along routes used by local ethnic groups , and broken tree branches at dusty crossroads were often all that indicated the direction . initially , most of the communist cadres who came down the trail were southerners by birth who had trained in north vietnam . they dressed like civilian peasants in black , silk pajamas with a checkered scarf . they wore ho chi minh sandals on their feet , cut from truck tires , and carried their ration of cooked rice in elephants ' intestines , a linen tube hung around the body . the conditions were harsh and many deaths were caused by exposure , malaria , and amoebic dysentery . getting lost , starving to death , and the possibility of attacks by wild tigers or bears were constant threats . meals were invariably just rice and salt , and it was easy to run out . fear , boredom , and homesickness were the dominant emotions . and soldiers occupied their spare time by writing letters , drawing sketches , and drinking and smoking with local villagers . the first troops down the trail did not engage in much fighting . and after an exhausting six month trip , arriving in the south was a real highlight , often celebrated by bursting into song . by 1965 , the trip down the trail could be made by truck . thousands of trucks supplied by china and russia took up the task amidst ferocious b-52 bombing and truck drivers became known as pilots of the ground . as traffic down the trail increased , so did the u.s. bombing . they drove at night or in the early morning to avoid air strikes , and watchmen were ready to warn drivers of enemy aircraft . villages along the trail organized teams to guarantee traffic flow and to help drivers repair damage caused by air attacks . their catch cries were , `` everything for our southern brothers ! '' and , `` we will not worry about our houses if the vehicles have not yet gotten through . '' some families donated their doors and wooden beds to repair roads . vietnamese forces even used deception to get the u.s. aircraft to bomb mountainsides in order to make gravel for use in building and maintaining roads . the all-pervading red dust seeped into every nook and cranny . the ho chi minh trail had a profound impact on the vietnam war and it was the key to hanoi 's success . north vietnamese victory was not determined by the battlefields , but by the trail , which was the political , strategic , and economic lynchpin . americans recognized its achievement , calling the trail , `` one of the great achievements in military engineering of the 20th century . '' the trail is a testimony to the strength of will of the vietnamese people , and the men and women who used the trail have become folk heros .
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the first troops moved in single-file along routes used by local ethnic groups , and broken tree branches at dusty crossroads were often all that indicated the direction . initially , most of the communist cadres who came down the trail were southerners by birth who had trained in north vietnam . they dressed like civilian peasants in black , silk pajamas with a checkered scarf .
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initially , most of the people that used the trail were southerners by birth that were trained in the north . what would you expect to see them wearing or carrying ?
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as one of the most notorious gangsters in history , al capone presided over a vast and profitable empire of organized crime . when he was finally put on trial , the most he could be convicted of was tax evasion . the nearly $ 100 million a year , that 's 1.4 billion in today 's currency , that capone had earned from illegal gambling , bootlegging , brothels , and extortion , would have served as evidence of his crimes . but the money was nowhere to be found . capone and his associates had hidden it through investments in various businesses whose ultimate ownership could n't be proven , like cash-only laundromats . in fact , those laundromats are part of the reason for the name of this activity , money laundering . money laundering came to be the term for any process that cleans illegally obtained funds of their dirty criminal origins , allowing them to be used within the legal economy . but capone was n't the first to launder money . in fact , this practice is about as old as money itself . merchants hid their riches from tax collecters , and pirates sought to sell their bounty without drawing attention to how they got it . with the recent arrival of virtual currencies , offshore banking , the darknet , and global markets , schemes have become much more complex . although modern money laundering methods vary greatly , most share three basic steps : placement , layering , and integration . placement is where illegally obtained money is converted into assets that seem legitimate . that 's often done by depositing funds into a bank account registered to an anonymous corporation or a professional middleman . this step is where criminals are often most vulnerable to detection since they introduce massive wealth into the financial system seemingly out of nowhere . the second step , layering , involves using multiple transactions to further distance the funds from their origin . this can take the form of transfers between multiple accounts , or the purchase of tradable property , like expensive cars , artwork , and real estate . casinos , where large sums of money change hands every second , are also popular venues for layering . a money launderer may have their gambling balance made available at a casino chain 's locations in other countries , or work with employees to rig games . the last step , integration , allows clean money to re-enter the mainstream economy and to benefit the original criminal . they might invest it into a legal business claiming payment by producing fake invoices , or even start a bogus charity , placing themselves on the board of directors with an exorbitant salary . money laundering itself was n't officially recognized as a federal crime in the united states until 1986 . before that point , the government needed to prosecute a related crime , like tax evasion . from 1986 on , they could confiscate wealth simply by demonstrating that concealment had occurred , which had a positive effect on prosecuting major criminal operations , like drug traffickers . however , a legal shift has raised concerns involving privacy and government surveillance . today , the united nations , national governments , and various nonprofits fight against money laundering , yet the practice continues to play a major role in global crime . and the most high-profile instances of money laundering have involved not just private individuals , but major financial institutions and government officials . no one knows for sure the total amount of money that 's laundered on a yearly basis , but some organizations estimate it to be in the hundreds of billions of dollars .
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capone and his associates had hidden it through investments in various businesses whose ultimate ownership could n't be proven , like cash-only laundromats . in fact , those laundromats are part of the reason for the name of this activity , money laundering . money laundering came to be the term for any process that cleans illegally obtained funds of their dirty criminal origins , allowing them to be used within the legal economy . but capone was n't the first to launder money .
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___________ is the third stage of the money laundering process .
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ok so promethium is actually my least favourite lanthanide because i can ’ t actually work with it . it ’ s highly radioactive and at any one time on the earth ’ s surface there is not an awful lot of it so you can ’ t physically get enough of it to do any chemistry with . so promethium is the only one of the rare earth elements that is radioactive , but because it ’ s radioactive and the atoms decay away it ’ s not found in nature . so it was only after the start of nuclear research that people discovered promethium , even some of the products from the decay from other radioactive elements . and you can see this quite well : this is an old chemistry book that i ’ ve got , written by aston , the famous scientist who discovered isotopes – atoms of the same element that have different weights - and in this book which he published in 1922… hold it a bit more vertical . ok go ahead . …he had a periodic table and if you look down here , here are the rare earths and in this position here there is a space for element 61 , promethium . so element 61 wasn ’ t known in 1922 and it was found much later . but you can see the rest of the elements were , except there ’ s a gap down here under tungsten because , again , the element rhenium was only discovered relatively recently compared to most of the other elements .
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it ’ s highly radioactive and at any one time on the earth ’ s surface there is not an awful lot of it so you can ’ t physically get enough of it to do any chemistry with . so promethium is the only one of the rare earth elements that is radioactive , but because it ’ s radioactive and the atoms decay away it ’ s not found in nature . so it was only after the start of nuclear research that people discovered promethium , even some of the products from the decay from other radioactive elements .
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promethium has been used as a paint to create luminous dials and markings by mixing it with zinc sulfide phosphorescent material . promethium was used to replace the more dangerous radium , but nowadays it has been replaced by a much safer element , a radioactive isotope of hydrogen . which isotope is this ?
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in this short video , we 're going to show you how we constructed and animated a pop-up book to explain earth 's tectonic plates . the supercontinent pangaea broke apart 200,000,000 years ago , but the pieces have n't stopped shifting . although with animation we can show this movement easily with drawings , we thought it 'd be more interesting to depict gigantic sliding slabs of rock using a tangible object that also moves and shifts . and the pop-up book idea was born . ( music ) to make your own pop-up book , you 'll need some basic paper tools , such as scissors , an x-acto knife , glue , double-sided scotch tape , a ruler , a bone folder or other creasing tool , and , of course , some paper . for this lesson , we first determined the visual style by making illustrations and deciding on the overall design , colors , shapes and elements we wanted on each page , or spread . you can have more detailed illustrations , but we wanted to illustrate this lesson simply by playing with shapes and colors . when you visualize your pop-up and choose a visual style , you will want to make a bunch of good old pencil sketches on paper and plan each movement for each spread . plan as much as you can : all the basic shapes and how they connect and how you want them to move , which parts you want to pop-up first . challenge yourself , and explore multiple possibilities of how your main element on the spread can pop up . for the next step , make a mock-up spread and see if your masterful paper engineering ideas translate from a sketch to the actual prototype . instead of using fancy paper , start with the cheap stuff and allow yourself to make mistakes and adjustments . this prototype lets you see how your preliminary sketches will come to life . you will want to first draw all individual parts on a single sheet , including all your main pieces , all the supporting pieces and the folds . you may be surprised that there are only two types of folds that can make your elements pop up the way you want : a step fold and a v-fold . here , you can see how we used a step fold to make each layer of the earth step out . then , cut all your individual elements and assemble using glue or double-sided scotch tape . ( music ) through trial and error , make sure that all the elements , shapes and placements are moving the way you imagined , and that they fold properly when closed and opened . ( music ) once your prototype is tested and complete , you can proceed to making the final product in color . draw or paint on your main pop-up elements as you see fit . for this lesson , we decided to just play with simple shapes in different colors to create the world of shifting continents we imagined . ( music ) when we were planning each spread , we knew we wanted some elements to move independently of the typical pop-up book using slight manipulations and animations . we had to plan well , but also use a few tricks . as always , when you 're making stop-motion , you may have to be creative and use all sorts of unusual tools and props to achieve the effect that you want . in this shot , the birds had to fly across and off the edge of the book , so we used fun-tak to move the clouds across the page . once they left the page , they had to be trimmed to get the illusion they flew off . when the pages of the book close at the end , we had to flip each page , supporting it in each position long enough to be photographed as an individual frame . we used binder clips , wedges , fun-tak , and almost every handy little thing you can think of . once all the individual frames were photographed , we put them all together and composited to make our pop-up book look like it 's moving on its own . so now , think of a special occasion where you can surprise someone with your own unique pop-up card , or an entire story that you want to tell , and start plotting the ins and outs of your pop-up book .
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although with animation we can show this movement easily with drawings , we thought it 'd be more interesting to depict gigantic sliding slabs of rock using a tangible object that also moves and shifts . and the pop-up book idea was born . ( music ) to make your own pop-up book , you 'll need some basic paper tools , such as scissors , an x-acto knife , glue , double-sided scotch tape , a ruler , a bone folder or other creasing tool , and , of course , some paper .
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the two folds you need to know for creating a pop-up book are the :
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it 's often said that despite humanity 's many conflicts , we all bleed the same blood . it 's a nice thought but not quite accurate . in fact , our blood comes in a few different varieties . our red blood cells contain a protein called hemoglobin that binds to oxygen , allowing the cells to transport it throughout the body . but they also have another kind of complex protein on the outside of the cell membrane . these proteins , known as antigens , communicate with white blood cells , immune cells that protect against infection . antigens serve as identifying markers , allowing the immune system to recognize your body 's own cells without attacking them as foreign bodies . the two main kinds of antigens , a and b , determine your blood type . but how do we get four blood types from only two antigens ? well , the antigens are coded for by three different alleles , varieties of a particular gene . while the a and b alleles code for a and b antigens , the o allele codes for neither , and because we inherit one copy of each gene from each parent , every individual has two alleles determining blood type . when these happen to be different , one overrides the other depending on their relative dominance . for blood types , the a and b alleles are both dominant , while o is recessive . so a and a gives you type a blood , while b and b gives you type b . if you inherit one of each , the resulting codominance will produce both a and b antigens , which is type ab . the o allele is recessive , so either of the others will override it when they 're paired , resulting in either type a or type b . but if you happen to inherit two os , instructions will be expressed that make blood cells without the a or the b antigen . because of these interactions , knowing both parents ' blood types lets us predict the relative probability of their children 's blood types . why do blood types matter ? for blood transfusions , finding the correct one is a matter of life and death . if someone with type a blood is given type b blood , or vice versa , their antibodies will reject the foreign antigens and attack them , potentially causing the transfused blood to clot . but because people with type ab blood produce both a and b antigens , they do n't make antibodies against them , so they will recognize either as safe , making them universal recipients . on the other hand , people with blood type o do not produce either antigen , which makes them universal donors , but will cause their immune system to make antibodies that reject any other blood type . unfortunately , matching donors and recipients is a bit more complicated due to additional antigen systems , particular the rh factor , named after the rhesus monkeys in which it was first isolated . rh+ or rh- refers to the presence or absence of the d antigen of the rh blood group system . and in addition to impeding some blood transfusions , it can cause severe complications in pregnancy . if an rh- mother is carrying an rh+ child , her body will produce rh antibodies that may cross the placenta and attack the fetus , a condition known as hemolytic disease of the newborn . some cultures believe blood type to be associated with personality , though this is not supported by science . and though the proportions of different blood types vary between human populations , scientists are n't sure why they evolved ; perhaps as protection against blood born diseases , or due to random genetic drift . finally , different species have different sets of antigens . in fact , the four main blood types shared by us apes seem paltry in comparison to the thirteen types found in dogs .
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but because people with type ab blood produce both a and b antigens , they do n't make antibodies against them , so they will recognize either as safe , making them universal recipients . on the other hand , people with blood type o do not produce either antigen , which makes them universal donors , but will cause their immune system to make antibodies that reject any other blood type . unfortunately , matching donors and recipients is a bit more complicated due to additional antigen systems , particular the rh factor , named after the rhesus monkeys in which it was first isolated .
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type o blood is the universal donor and is in the greatest demand . hospitals rely on the goodwill of type o donors to supply this demand . how could type a , b or ab blood be biochemically modified to not elicit an immune response ?
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it 's midnight and all is still , except for the soft skittering of a gecko hunting a spider . geckos seem to defy gravity , scaling vertical surfaces and walking upside down without claws , adhesive glues or super-powered spiderwebs . instead , they take advantage of a simple principle : that positive and negative charges attract . that attraction binds together compounds , like table salt , which is made of positively charged sodium ions stuck to negatively charged chloride ions . but a gecko 's feet are n't charged and neither are the surfaces they 're walking on . so , what makes them stick ? the answer lies in a clever combination of intermolecular forces and stuctural engineering . all the elements in the periodic table have a different affinity for electrons . elements like oxygen and fluorine really , really want electrons , while elements like hydrogen and lithium do n't attract them as strongly . an atom 's relative greed for electrons is called its electronegativity . electrons are moving around all the time and can easily relocate to wherever they 're wanted most . so when there are atoms with different electronegativities in the same molecule , the molecules cloud of electrons gets pulled towards the more electronegative atom . that creates a thin spot in the electron cloud where positive charge from the atomic nuclei shines through , as well as a negatively charged lump of electrons somewhere else . so the molecule itself is n't charged , but it does have positively and negatively charged patches . these patchy charges can attract neighboring molecules to each other . they 'll line up so that the positive spots on one are next to the negative spots on the other . there does n't even have to be a strongly electronegative atom to create these attractive forces . electrons are always on the move , and sometimes they pile up temporarily in one spot . that flicker of charge is enough to attract molecules to each other . such interactions between uncharged molecules are called van der waals forces . they 're not as strong as the interactions between charged particles , but if you have enough of them , they can really add up . that 's the gecko 's secret . gecko toes are padded with flexible ridges . those ridges are covered in tiny hair-like structures , much thinner than human hair , called setae . and each of the setae is covered in even tinier bristles called spatulae . their tiny spatula-like shape is perfect for what the gecko needs them to do : stick and release on command . when the gecko unfurls its flexible toes onto the ceiling , the spatulae hit at the perfect angle for the van der waals force to engage . the spatulae flatten , creating lots of surface area for their positively and negatively charged patches to find complimentary patches on the ceiling . each spatula only contributes a minuscule amount of that van der waals stickiness . but a gecko has about two billion of them , creating enough combined force to support its weight . in fact , the whole gecko could dangle from a single one of its toes . that super stickiness can be broken , though , by changing the angle just a little bit . so , the gecko can peel its foot back off , scurrying towards a meal or away from a predator . this strategy , using a forest of specially shaped bristles to maximize the van der waals forces between ordinary molecules has inspired man-made materials designed to imitate the gecko 's amazing adhesive ability . artificial versions are n't as strong as gecko toes quite yet , but they 're good enough to allow a full-grown man to climb 25 feet up a glass wall . in fact , our gecko 's prey is also using van der waals forces to stick to the ceiling . so , the gecko peels up its toes and the chase is back on .
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electrons are moving around all the time and can easily relocate to wherever they 're wanted most . so when there are atoms with different electronegativities in the same molecule , the molecules cloud of electrons gets pulled towards the more electronegative atom . that creates a thin spot in the electron cloud where positive charge from the atomic nuclei shines through , as well as a negatively charged lump of electrons somewhere else .
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in a molecule where one atom is more electronegative than the other , the electrons will tend to be _____ .
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how does this music make you feel ? do you find it beautiful ? is it creative ? now , would you change your answers if you learned the composer was this robot ? believe it or not , people have been grappling with the question of artificial creativity , alongside the question of artifcial intelligence , for over 170 years . in 1843 , lady ada lovelace , an english mathematician considered the world 's first computer programmer , wrote that a machine could not have human-like intelligence as long as it only did what humans intentionally programmed it to do . according to lovelace , a machine must be able to create original ideas if it is to be considered intelligent . the lovelace test , formalized in 2001 , proposes a way of scrutinizing this idea . a machine can pass this test if it can produce an outcome that its designers can not explain based on their original code . the lovelace test is , by design , more of a thought experiment than an objective scientific test . but it 's a place to start . at first glance , the idea of a machine creating high quality , original music in this way might seem impossible . we could come up with an extremely complex algorithm using random number generators , chaotic functions , and fuzzy logic to generate a sequence of musical notes in a way that would be impossible to track . but although this would yield countless original melodies never heard before , only a tiny fraction of them would be worth listening to . with the computer having no way to distinguish between those which we would consider beautiful and those which we wo n't . but what if we took a step back and tried to model a natural process that allows creativity to form ? we happen to know of at least one such process that has lead to original , valuable , and even beautiful outcomes : the process of evolution . and evolutionary algorithms , or genetic algorithms that mimic biological evolution , are one promising approach to making machines generate original and valuable artistic outcomes . so how can evolution make a machine musically creative ? well , instead of organisms , we can start with an initial population of musical phrases , and a basic algorithm that mimics reproduction and random mutations by switching some parts , combining others , and replacing random notes . now that we have a new generation of phrases , we can apply selection using an operation called a fitness function . just as biological fitness is determined by external environmental pressures , our fitness function can be determined by an external melody chosen by human musicians , or music fans , to represent the ultimate beautiful melody . the algorithm can then compare between our musical phrases and that beautiful melody , and select only the phrases that are most similar to it . once the least similar sequences are weeded out , the algorithm can reapply mutation and recombination to what 's left , select the most similar , or fitted ones , again from the new generation , and repeat for many generations . the process that got us there has so much randomness and complexity built in that the result might pass the lovelace test . more importantly , thanks to the presence of human aesthetic in the process , we 'll theoretically generate melodies we would consider beautiful . but does this satisfy our intuition for what is truly creative ? is it enough to make something original and beautiful , or does creativity require intention and awareness of what is being created ? perhaps the creativity in this case is really coming from the programmers , even if they do n't understand the process . what is human creativity , anyways ? is it something more than a system of interconnected neurons developed by biological algorithmic processes and the random experiences that shape our lives ? order and chaos , machine and human . these are the dynamos at the heart of machine creativity initiatives that are currently making music , sculptures , paintings , poetry and more . the jury may still be out as to whether it 's fair to call these acts of creation creative . but if a piece of art can make you weep , or blow your mind , or send shivers down your spine , does it really matter who or what created it ?
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in 1843 , lady ada lovelace , an english mathematician considered the world 's first computer programmer , wrote that a machine could not have human-like intelligence as long as it only did what humans intentionally programmed it to do . according to lovelace , a machine must be able to create original ideas if it is to be considered intelligent . the lovelace test , formalized in 2001 , proposes a way of scrutinizing this idea . a machine can pass this test if it can produce an outcome that its designers can not explain based on their original code . the lovelace test is , by design , more of a thought experiment than an objective scientific test . but it 's a place to start .
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to pass the lovelace test a machine should :
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- when you get to space , because you 're in a zero g environment , some really funky things happen to your body . ( upbeat music ) i grew an inch . right now , i 'm 5'11 '' but in space i was six-feet tall . on the ground , gravity compresses your spine , it pulls you down , the force factor going down . in space , without gravity pulling your spine down , every vertebrae has a chance to move up , which gives you your extra inch of height . after my spine elongated , when i went to bed on the first night , i felt some back pain , some lower back pain , and so i actually curled up to kind of alleviate that pain , to kind of stretch it out even more . a few other ways the body can change in space are the heart gets smaller and changes shape because it 's not having to pump as hard to pull the blood up from your feet , 'cause now things are just floating and working inside your body so it 's pumping easier , therefore the muscle walls actually changes the shape and they get smaller . without gravity , your bones , they change shape and they lose calcium , and they become more brittle . so , we run on a treadmill that you strap yourself down to and you run on the treadmill to actually give loads into your bones to keep them from atrophying and losing bone density or calcium . for some people in space , your intracranial pressure changes with pushes on your eyeball and that changes its shape , therefore requiring you to wear glasses in space , so it effects your vision . so , we keep different prescriptions of glasses on board just in case someone 's vision changes . any changes in our bodies and anything that happens in space , it 's worth it for the spirit of exploration .
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so , we run on a treadmill that you strap yourself down to and you run on the treadmill to actually give loads into your bones to keep them from atrophying and losing bone density or calcium . for some people in space , your intracranial pressure changes with pushes on your eyeball and that changes its shape , therefore requiring you to wear glasses in space , so it effects your vision . so , we keep different prescriptions of glasses on board just in case someone 's vision changes .
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5. some people have to wear glasses while in space , but not on earth . why ?
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( music ) ( music ) we live in an interconnected , an increasingly globalized world . thanks to international jet travel , people and the diseases they carry can be in any city on the planet in a matter of hours . and once a virus touches down , sometimes all it takes is one sneeze to spread the infection throughout the community . when humans were hunter-gatherers , roaming the wild savannas , we were never in one place long enough , and settlements were not large enough to sustain the transmission of infectious microbes . but with the advent of the agricultural revolution 10,000 years ago , and the arrival of permanent settlements in the middle east , people began living side-by-side with animals , facilitating the spread of bacteria and viruses between cattle and humans . epidemics and pandemics come in many shapes and forms . in 2010 , for instance , a devastating earthquake struck haiti , forcing thousands of people into temporary refugee camps . within weeks , the camps had become breeding grounds for cholera , a bacteria spread by contaminated water , triggering a country-wide epidemic . but the most common cause of epidemics are viruses , such as measles , influenza and hiv . and when they go global , we call them pandemics . pandemics have occurred throughout human history , some have left scars on the tissue and bone of their victims , while evidence for others comes from preserved dna . for instance , scientists have recovered dna from the bacteria that transmits tuberculosis from the remains of ancient egyptian mummies . and in 2011 , scientists investigating a plague pit in the city of london were able to reconstruct the genome of yersinia pestis , the bacterium responsible for the black death of the 14th century . it is thought the plague originated in china in around 1340 , spreading west along the silk road , the caravan route running from mongolia to the crimea . in 1347 , the plague reached the mediterranean , and by 1400 , it had killed in excess of 34 million europeans , earning it the title , the great mortality . it was later historians who called it the black death . however , by far the greatest pandemic killer is influenza . flu is constantly circulating between the southern and northern hemispheres . in north america and europe , seasonal flus occur every autumn and winter . as the majority of children and adults will have been exposed to the virus in previous seasons , these illnesses are usually mild . however , every 20 to 40 years or so the virus undergoes a dramatic mutation . usually this occurs when a wild flu virus circulating in ducks and farm poultry meets a pig virus , and they exchange genes . this process is known as antigenic shift and has occurred throughout human history . the first recorded pandemic occurred in 1580 . the 18th and 19th centuries saw at least six further pandemics . in terms of mortality , none can compare with the great flu pandemic of 1918 . the first indication of the pandemic came in the spring , when american troops in northern france began complaining of chills , headaches and fever . then , the following september , at a u.s. army barracks near boston , soldiers started collapsing on parade , prompting their removal to the camp infirmary . as a surgeon there recalled , two hours after admission , they had the mahogany spots over the cheekbones and a few hours later you can begin to see the cyanosis extending from their ears and spreading all over the face . it is only a matter of a few hours then until death comes , and it is simply a struggle for air until they suffocate . on the s.s. leviathan , a huge american transport en route to bordeaux , sick men hemorrhaged blood from their noses , turning the decks between their bunks slick with bodily fluids . meanwhile , british soldiers returning from northern france on furlough introduced the flu to dover and other channel ports , from where the virus was carried by rail to london . by the time the pandemic had run its course in april 1919 , an estimated 675,000 americans and 230,000 britons were dead . in india alone , some 10 million were killed , and worldwide the death toll was an astonishing 50 million . but that was then . today , planes can transport viruses to any country on the globe in a fraction of the time it took in 1918 . in february 2003 , for instance , a chinese doctor arrived at the metropole hotel in hong kong feeling unwell . unknown to him , he was harboring a new animal-origin virus called sars , short for severe acute respiratory syndrome . within 24 hours of checking into room 913 , sixteen other guests had been infected , and over the following days five boarded planes to overseas destinations , spreading the virus to vietnam , singapore and canada . flights between hong kong , toronto and other international cities were quickly grounded and thanks to other emergency measures , a pandemic was averted . by the time the outbreak was over four months later , sars had infected 29 countries worldwide and more than 1,000 people were dead . for all that the virus was rapidly contained , however , there was little that could be done about the alarming news reports carried by cable news channels and the internet . as bloggers added to the hysteria by spreading unfounded conspiracy theories , tourism in hong kong and other affected cities ground to a halt , costing businesses more than 10 billion u.s. dollars . one business , however , did very well . above all , sars was a reminder that pandemics have always been associated with panic . if history teaches us anything , it 's that while pandemics may start small , their impacts can be as dramatic as wars and natural disasters . the difference today is that science gives us the ability to detect pandemics right at the very beginning and to take action to mitigate their impacts before they spread too widely . ( music )
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as the majority of children and adults will have been exposed to the virus in previous seasons , these illnesses are usually mild . however , every 20 to 40 years or so the virus undergoes a dramatic mutation . usually this occurs when a wild flu virus circulating in ducks and farm poultry meets a pig virus , and they exchange genes .
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what happens to the influenza virus every 20-40 years , and why ? what are the recent example ( s ) ?
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what do a seventeen-year-old pakistani , a norwegian explorer , a tibetan monk , and an american pastor have in common ? they were all awarded the nobel peace prize . among the top prestigious awards in the world , this prize has honored some of the most celebrated and revered international figures and organizations in history . to understand how it all got started , we have to go back to the 1800s . swedish chemist alfred nobel was then mostly known for the invention of dynamite , a breakthrough which launched his career as a successful inventor and businessman . 30 years later , he had become extremely wealthy , but never married , and had no children . when his will was opened after his death , it came as a surprise that his fortune was to be used for five prizes in physics , chemistry , medicine , literature , and peace . these prizes illustrated his lifelong commitment to sciences and his passion for literature . but what about peace ? because nobel 's name was tied to inventions used in the war industry , many have assumed that he created the peace prize out of regret . however , this is all speculation as he never expressed any such sentiments , and his inventions were also used for constructive purposes . instead , many historians connect alfred nobel 's interest for the peace cause to his decade-long friendship and correspondence with an austrian pacifist named bertha von suttner . von suttner was one of the leaders of the international peace movement , and in 1905 , after nobel 's death , she became the first woman to be awarded the nobel peace prize . nobel 's will outlined three criteria for the peace prize , which unlike the other sweden-based prizes , would be administered in norway . disarmament , peace congresses , and brotherhood between nations . these standards have since been expanded to include other ways of promoting peace , such as human rights and negotiations . and the prize does n't just have to go to one person . about a third of noble peace prizes have been shared by two or three laureates . so how do nominations for the prize work ? according to the nobel foundation , a valid nomination can come from a member of a national assembly , state government , or an international court . eligible nominators also include university rectors , professors of the social sciences , history , philosophy , law , and theology , and previous recipients of the peace prize . but if you want to know more about who was recently nominated , you 'll have to be patient . all information about nominations remains secret for 50 years . take martin luther king jr. we did n't actually know who nominated him until 2014 . his nominators turned out to be the quakers , who had won the prize previously , and eight members of the swedish parliament . there 's no limit to the number of times a person or organization can be nominated . in fact , jane addams , recognized as the founder of social work in the united states , was nominated 91 times before finally being awarded the prize . the absence of a laureate can also be symbolic . the 1948 decision not to award the prize following the death of mahatma gandhi has been interpreted as an attempt to respectfully honor the so-called missing laureate . as with the other nobel prizes , the peace prize ca n't be awarded posthumously . the secret selection process takes almost a year , and is carried out by the five appointed members of the norwegian nobel committee who are forbidden from having any official political function in norway . starting with a large pool of nominations , exceeding 300 in recent years , they access each candidate 's work and create a short list . finally , the chairman of the nobel committee publicly announces the laureate in october . the awards ceremony takes place on december 10th , the anniversary of alfred nobel 's death . the prize itself includes a gold medal inscribed with the latin words , `` pro pace et fraternitate gentium , '' or `` for the peace and brotherhood of men , '' as well as a diploma and a large cash prize . recently , it 's been 8 million swedish kronor , or roughly a million us dollars , which is split in the case of multiple laureates . and while laureates can use the prize money as they choose , in recent years , many have donated it to humanitarian or social causes . for many years , the nobel peace prize was predominately awarded to european and north american men . but in recent years , significant changes have been taking place , making the prize more global than ever . 23 organizations and 103 individuals , that 's 87 men and 16 women , have made up the 126 nobel peace prize laureates in history . they include desmond tutu for his nonviolent campaign against apartheid in south africa , jody williams for her campaign to ban and clear anti-personnel mines , rigoberta menchú tum for her work for social justice and reconciliation based on respect for the rights of indigenous peoples , martti ahtisaari for his efforts to resolve international conflicts in namibia , kosovo , and indonesia , and aung san suu kyi for her nonviolent struggle for democracy and human rights in myanmar . they 're just a few examples of the people who have inspired us , challenged us , and demonstrated through their actions that there are many paths to peace .
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but if you want to know more about who was recently nominated , you 'll have to be patient . all information about nominations remains secret for 50 years . take martin luther king jr. we did n't actually know who nominated him until 2014 .
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how long are nominations kept secret ?
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how and when did our universe begin ? how did it get to look like this ? how will it end ? humans have been discussing these questions for as long as they 've been around without ever reaching much agreement . today , cosmologists are working hard to find the answers . but how can anyone hope to find concrete answers to such profound questions ? and how is it possible to explore and study something as huge as the universe , most of which we 'll never be able to reach ? the answer is light . and although light from distant parts of the universe can take billions of years to reach us , it carries six unique messages that , when put together , can disclose an amazing amount of information to astronomers who know how to look for it . just as sunlight can be split up into the familiar rainbow , splitting the light from distant objects exposes different patterns of colors depending on its source . this distinctive light barcode can reveal not only an object 's composition , but also the temperature and pressure of its constituent parts . there 's even more we can discover from light . if you 've ever stood on a train platform , you might have noticed that the train sounds different depending on its direction with the pitch ascending when it approaches you and descending when it speeds away . but this is n't because the train conductor is practicing for a second career . rather , it 's because of something called the doppler effect where sound waves generated by an approaching object are compressed , while those from a receding object are stretched . but what has this to do with astronomy ? sound does not travel through a vacuum . in space , no one can you hear you scream ! but the same doppler effect applies to light whose source is moving at exceptional speed . if it 's moving towards us , the shorter wavelength will make the light appear to be bluer . while light from a source that 's moving away will have a longer wavelength , shifting towards red . so by analyzing the color pattern in the doppler shift of the light from any object observed with a telescope , we can learn what it 's made of , how hot it is and how much pressure it 's under , as well as whether it 's moving , in what direction and how fast . and these six measurements , like six points of light , reveal the history of the universe . the first person to study the light from distant galaxies was edwin hubble , and the light he observed was redshifted . the distant galaxies were all moving away from us , and the further away the were , the faster they were receding . hubble had discovered our universe is expanding , providing the first evidence for the big bang theory . along with the idea that the visible universe has been constantly expanding from a densely packed single point , one of this theory 's most important predictions is that the early universe consisted of just two gases : hydrogen and helium , in a ratio of three to one . and this prediction can also be tested with light . if we observe the light from a remote , quiet region of the universe and split it , we do indeed find the signatures of the two gases in just those proportions . another triumph for the big bang . however , many puzzles remain . although we know the visible universe is expanding , gravity should be applying the brakes . but recent measurements of light from distant dying stars show us that they 're farther away than predicted . so the expansion of the universe is actually accelerating . something appears to be pushing it , and many scientists believe that something is dark energy , making up over 2/3 of the universe and slowly tearing it apart . our knowledge of the behavior of matter and the precision of our instruments means that simply observing distant stars can tell us more about the universe than we ever thought possible . but there are other mysteries , like the nature of dark energy upon which we have yet to shed light .
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and how is it possible to explore and study something as huge as the universe , most of which we 'll never be able to reach ? the answer is light . and although light from distant parts of the universe can take billions of years to reach us , it carries six unique messages that , when put together , can disclose an amazing amount of information to astronomers who know how to look for it .
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how many pieces of information about the objects in our universe are carried by their light ?
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`` beauty is a curse , '' psyche thought as she looked over the cliff 's edge where she 'd been abandoned by her father . she 'd been born with the physical perfection so complete that she was worshipped as a new incarnation of venus , the goddess of love . but real-life human lovers were too intimidated even to approach her . when her father asked for guidance from the oracle of apollo , the god of light , reason , and prophecy . he was told to abandon his daughter on a rocky crag where she would marry a cruel and savage serpent-like winged evil . alone on the crag , psyche felt zephyr the west wind gently lifting her into the air . it set her down before a palace . `` you are home , '' she heard an unseen voice say . `` your husband awaits you in the bedroom , if you dare to meet him . '' she was brave enough , psyche told herself . the bedroom was so dark that she could n't see her husband . but he did n't feel serpent-like at all . his skin was soft , and his voice and manner were gentle . she asked him who he was , but he told her this was the one question he could never answer . if she loved him , she would not need to know . his visits continued night after night . before long , psyche was pregnant . she rejoiced , but was also conflicted . how could she raise her baby with a man she 'd never seen ? that night , psyche approached her sleeping husband holding an oil lamp . what she found was the god cupid who sent gods and humans lusting after each other with the pinpricks of his arrows . psyche dropped her lamp , burning cupid with hot oil . he said he 'd been in love with psyche ever since his jealous mother , venus , asked him to embarrass the young woman by pricking her with an arrow . but taken with psyche 's beauty , cupid used the arrow on himself . he did n't believe , however , that gods and humans could love as equals . now that she knew his true form , their hopes for happiness were dashed , so he flew away . psyche was left in despair until the unseen voice returned and told her that it was indeed possible for her and cupid to love each other as equals . encouraged , she set out to find him . but venus intercepted psyche and said she and cupid could only wed if she completed a series of impossible tasks . first , psyche was told to sort a huge , messy pile of seeds in a single night . just as she was abandoning hope , an ant colony took pity on her and helped with the work . successfully passing the first trial , psyche next had to bring venus the fleece of the golden sheep , who had a reputation for disemboweling stray adventurers , but a river god showed her how to collect the fleece the sheep had snagged on briars , and she succeeded . finally , psyche had to travel to the underworld and convince proserpina , queen of the dead , to put a drop of her beauty in a box for venus . once again , the unseen voice came to psyche 's aide . it told her to bring barley cakes for cerberus , the guard dog to the underworld and coins to pay the boatman , charon to ferry her across the river styx . with her third and final task complete , psyche returned to the land of the living . just outside venus 's palace , she opened the box of proserpina 's beauty , hoping to keep some for herself . but the box was filled with sleep , not beauty , and psyche collapsed in the road . cupid , now recovered from his wounds , flew to his sleeping bride . he told her he 'd been wrong and foolish . her fearlessness in the face of the unknown proved that she was more than his equal . cupid gave psyche amborsia , the nectar of the gods , making her immortal . shortly after , psyche bore their daughter . they named her pleasure , and she , cupid , and psyche , whose name means soul , have been complicating people 's love lives ever since .
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but venus intercepted psyche and said she and cupid could only wed if she completed a series of impossible tasks . first , psyche was told to sort a huge , messy pile of seeds in a single night . just as she was abandoning hope , an ant colony took pity on her and helped with the work .
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psyche sorts through a giant pile of seeds :
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so comrades , welcome to the lecture . what i am going to do now , we ’ re going to begin with an experiment to illustrate this point that the oxygen molecule , o2 , has unpaired electrons . now we ’ re outside just to show you the reactivity of this lovely stuff here , liquid oxygen . so you can see wonderful liquid oxygen is a nice blue colour . so over here on the table we ’ ve got a tin tray which we ’ re going to use to contain the experiment that i ’ m going to show you next . so we ’ ve got our favourite liquid oxygen . strongly oxidising ; very , very reactive , and here i ’ ve got some cotton wool . so this is the same stuff we use to take make-up off , perhaps our partners or our girlfriends or our wives , and this is the same stuff we use to wipe our babies ’ bums . oxygen is an interesting element because it exists in two forms : the taught form which we breathe all the time is o2 , two oxygen atoms joined together ; and there ’ s another form called ozone , and which has three atoms arranged like the letter v , or letter v this way up . oxygen has unpaired electrons within the molecular orbitals , in the atomic orbitals around the structure , and these unpaired electrons give rise to colour and that colour is blue . so blue is often perceived to be the colour of solvated or unpaired electrons , and you can see here the lovely blue colour . now lots of chemists are really scared when they see the blue of liquid oxygen , because liquid oxygen is very , very reactive . generally you only make liquid oxygen by mistake . not like today when we ’ re making some on purpose . and if you ’ ve made it by mistake in an uncontrolled way , where there might be organic molecules perhaps simple organic chemicals like hydrocarbons , grease or perhaps a highly elaborate compound then , they tend to detonate and they tend to cause very energetic experiments . yeah it ’ s very fluffy it ’ s not very reactive . it doesn ’ t really burn , it cinders , might smoulder . but here we go , we ’ re going to pop it in the tray . so we begin with neil ’ s very high-tech piece of equipment , which is a test-tube on a piece of string . what we ’ re going to do is to put some liquid nitrogen in here . you can see liquid nitrogen – well you may not see – is colourless . ok ? so this is liquid nitrogen , and what i hope you can see is that this magnet , which is a pretty good magnet . let me just show you here with my keys , that they stick pretty strongly to the magnet . the magnet has absolutely no affect at all on the liquid nitrogen . i can pull the magnet and nothing happens . and then we ’ re going to fill up all of the void space , so all of the space in the cotton particles with oxygen . so you might want to stand back after this bit brady . so here we go , here ’ s our liquid oxygen . do you want to come in and zoom in on me ? it ’ s ok , i ’ ve got it zoomed nicely . ok , so here you can see the lovely blue liquid oxygen colour , going into the cotton wool particles . let ’ s try the same thing with liquid oxygen . careful of my shoes… so here we have a match on a stick , and i think you can see its probably alight , so we have our fire , we have our oxygen , and we have our fuel . now let ’ s see what happens when we put them all together . the liquid oxygen is a very nice blue colour today . so now let ’ s try , here ’ s the magnet again , and if i take the liquid oxygen you can see i can pull it right up here . it ’ s not as magnetic as my keys , but you can see there ’ s a really big difference . it sticks to the magnet . so you can see it really is magnetic . you ready ? ok. woohoo and there she blows ! and ozone is much more reactive than oxygen . so near the earth ’ s surface , where you and i are at the moment , ozone is really quite dangerous because if you breathe it in it can start reacting with any sort of molecule that has bonds between carbon . but in the upper atmosphere , ozone is extremely important because it absorbs ultra-violet light that comes from the sun and stops this ultra-violet light attacking the molecules in biological species on the surface . if it wasn ’ t for the ozone in the upper atmosphere all of us would be , if not dead , certainly very much less comfortable than we are at the moment . so neil ’ s now connecting up a piece of tube to oxygen cylinder and he is going to fill up this gas jar with oxygen and we are going to do a really classic experiment : the one that everyone learns at school and tests for oxygen , which is to relight a glowing splint . so we have a traditional gas jar full of oxygen . so here you can see we are burning a splint . ok , so this is the wood burning in excess oxygen around us , ok . so what we are going to do is we are going to take the splint out so it is just glowing . and if i blow on this splint you can see it gets brighter . now we are going to try and relight that splint by putting it into a very oxygen-rich atmosphere . so we ’ ll move over to the jar and we ’ ll put in our glowing splint and you can see the flame comes back to life . so that ’ s a test that everyone learns for an oxygen-rich environment . what happened ? what made that happen ? well the increased oxygen content/concentration reignites and reinitiates that oxidation of the wood or the burning of the wood . so we ’ ll do that again . so there we go : flame again .
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so blue is often perceived to be the colour of solvated or unpaired electrons , and you can see here the lovely blue colour . now lots of chemists are really scared when they see the blue of liquid oxygen , because liquid oxygen is very , very reactive . generally you only make liquid oxygen by mistake .
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what does the professor demonstrate to his university students with a magnet and a test tube full of liquid oxygen ?
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imagine an airplane flying one millimeter above the ground and circling the earth once every 25 seconds while counting every blade of grass . shrink all that down so that it fits in the palm of your hand , and you 'd have something equivalent to a modern hard drive , an object that can likely hold more information than your local library . so how does it store so much information in such a small space ? at the heart of every hard drive is a stack of high-speed spinning discs with a recording head flying over each surface . each disc is coated with a film of microscopic magnetised metal grains , and your data does n't live there in a form you can recognize . instead , it is recorded as a magnetic pattern formed by groups of those tiny grains . in each group , also known as a bit , all of the grains have their magnetization 's aligned in one of two possible states , which correspond to zeroes and ones . data is written onto the disc by converting strings of bits into electrical current fed through an electromagnet . this magnet generates a field strong enough to change the direction of the metal grain 's magnetization . once this information is written onto the disc , the drive uses a magnetic reader to turn it back into a useful form , much like a phonograph needle translates a record 's grooves into music . but how can you get so much information out of just zeroes and ones ? well , by putting lots of them together . for example , a letter is represented in one byte , or eight bits , and your average photo takes up several megabytes , each of which is 8 million bits . because each bit must be written onto a physical area of the disc , we 're always seeking to increase the disc 's areal density , or how many bits can be squeezed into one square inch . the areal density of a modern hard drive is about 600 gigabits per square inch , 300 million times greater than that of ibm 's first hard drive from 1957 . this amazing advance in storage capacity was n't just a matter of making everything smaller , but involved multiple innovations . a technique called the thin film lithography process allowed engineers to shrink the reader and writer . and despite its size , the reader became more sensitive by taking advantage of new discoveries in magnetic and quantum properties of matter . bits could also be packed closer together thanks to mathematical algorithms that filter out noise from magnetic interference , and find the most likely bit sequences from each chunk of read-back signal . and thermal expansion control of the head , enabled by placing a heater under the magnetic writer , allowed it to fly less than five nanometers above the disc 's surface , about the width of two strands of dna . for the past several decades , the exponential growth in computer storage capacity and processing power has followed a pattern known as moore 's law , which , in 1975 , predicted that information density would double every two years . but at around 100 gigabits per square inch , shrinking the magnetic grains further or cramming them closer together posed a new risk called the superparamagnetic effect . when a magnetic grain volume is too small , its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally , leading to data loss . scientists resolved this limitation in a remarkably simple way : by changing the direction of recording from longitudinal to perpendicular , allowing areal density to approach one terabit per square inch . recently , the potential limit has been increased yet again through heat assisted magnetic recording . this uses an even more thermally stable recording medium , whose magnetic resistance is momentarily reduced by heating up a particular spot with a laser and allowing data to be written . and while those drives are currently in the prototype stage , scientists already have the next potential trick up their sleeves : bit-patterned media , where bit locations are arranged in separate , nano-sized structures , potentially allowing for areal densities of twenty terabits per square inch or more . so it 's thanks to the combined efforts of generations of engineers , material scientists , and quantum physicists that this tool of incredible power and precision can spin in the palm of your hand .
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when a magnetic grain volume is too small , its magnetization is easily disturbed by heat energy and can cause bits to switch unintentionally , leading to data loss . scientists resolved this limitation in a remarkably simple way : by changing the direction of recording from longitudinal to perpendicular , allowing areal density to approach one terabit per square inch . recently , the potential limit has been increased yet again through heat assisted magnetic recording .
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it is predicted that perpendicular recording will push the areal density up to :
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so we 're gon na go find some liquid nitrogen . we keep it in a really large dewar tank at the back of the shop , so we 're gon na go find that now . so this is a dewar that we used to keep the liquid nitrogen in within the building so it 's much more convenient for us and our students to get it . so what we 're gon na do now is we 're gon na fill up our small dewar to carry the nitrogen back to the lab . so you can probably hear it hissing and fizzing going into the bottle , and you can see all the nitrogen evaporating off . nitrogen exists as a gas . molecules of n2 . and it is interesting , because the bond between the two nitrogen atoms is the strongest bond that you can get between any two atoms in the periodic table . any two atoms that are the same . sometimes , if you have two atoms that are different , the bond can be slightly stronger , but the nn triple bond is one of the strongest that you can have . so what we 're doing is we 're filling up the dewar with liquid nitrogen so that we can take that back to our lab to do our next experiment . so many explosive compounds , things that you 've heard of , like tnt and other explosives , all contain nitrogen , which are isolated atoms , and when the explosion goes off the atoms come together and release energy . nitrogen is used widely in laboratories , partly because it 's not as reactive as oxygen , so if you do an experiment in an atmosphere of nitrogen you can avoid reactions that might occur with air . you can also use nitrogen when it 's liquified as a coolant . liquid nitrogen boils at -196 degrees centigrade , 77 degrees absolute , and you can just hold it in a normal thermous flask . so this is a dewar of liquid nitrogen , and you can see that the nitrogen is evaporating from the top , coming out and frosting , coming down over the sides because it 's a little bit more dense than the air . you can see it 's heavily laden with ice , and you can see that the ice crystals are starting to grow on the top of the dewar here . it 's very cold though , so we must n't touch it for too long . so if we just tip some out on the floor , we can see that the nitrogen itself will come out like a liquid , like pouring water , but the interesting thing is , water , when i pour it on the floor it forms a puddle . it does nothing useful . in fact , it sort of gets in the way . but liquid nitrogen , when i pour it on the floor , it forms these really quite nice bubbles , and they fly across to the side of the room and take all the dust with them . pretty cool . but if you put materials like rubber or flowers into liquid nitrogen , instead of being soft and bendy they become really rigid , and you can smash them with a hammer . so you can see all of the bubbles forming on this steel tray now , and they 're sweeping away all the dust quite nicely as they evaporate and move further afield . so neil 's got a piece of tubing , and it 's really quite flexible tubing , you can see it 's really floppy , and now he 's gon na put it into the cryogenic liquid nitrogen and freeze it , and see what happens to the rubber . but you see another interesting thing there is that the liquid nitrogen is siphoning out through the tube , and that 's a really good joke , because you can direct that siphon at someones trousers and freeze their legs . so i think that 's enough , neil , let 's see if it 's a bit harder . wow , that shattered . and there 's quite a nice little operation that i 've heard about , in which you can take the lens out of somebody 's eye when they 're suitably anaesthetized , and this lens can be frozen and then put on the lathe and you can change its shape so you get the right shape , and then you let it unfreeze , it goes soft again , and you pop it back into their eye . . . . . . . . . . . . . captions by www.subply.com
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molecules of n2 . and it is interesting , because the bond between the two nitrogen atoms is the strongest bond that you can get between any two atoms in the periodic table . any two atoms that are the same .
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what is the order of the bond between the two nitrogen atoms of molecular nitrogen ?
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so our reaction ’ s ready . now all we need again is a little bit of water just to start it off . so we ’ re here today and we ’ ve come back after hours because we need to use this room for a long period of time because we ’ re going to do something quite exciting . because brady ’ s bought another camera which you can see he ’ s setup over there and we ’ re going to use that second camera to capture one second of film every minute for maybe two or three hours and we ’ re going to do some time lapse . something i ’ ve seen on tv with like flowers opening or plants growing but never with chemistry developing . silver is one of the few metallic elements that occurs naturally as the metal in nature . so that if you ’ re lucky you can wander around and find lumps of silver lying around on the ground . and this is how , in ancient times , silver was discovered so it has been known for thousands if not tens of thousands of years . gold is somewhat similar and also copper . but most other metals combine too easily with oxygen or other elements so you don ’ t find them naturally . so i thought what we ’ d do today is through a competition reaction and that competition reaction is based on something called the reactivity series of metals . so we ’ re going to compare the reactivity of two metals . it ’ s a bit like a game of football . we ’ re going to give one of those metals the football and in this case it ’ s another component or another salt component , nitrate . so the two metals that are going to be competing for the nitrate are silver and copper . and really these are related by something called the reactivity series . one of these metals is going to win , i know that and i hope we ’ ll find it during this video . silver had a particular use in photography and in the old days when people used photographic film the black colour that you saw on developed negatives is in fact silver . a photographic film consists of a layer of silver bromide or sometimes silver iodide and when the light shines on it the light just starts a tiny amount of reaction making silver and then when you put it in the developing solution the catalytic amount of silver that you ’ ve produced causes a big reaction and you make a large amount of silver . and so you get this black colour which then you can print as pictures . so on the bench i ’ ve got a small beaker or an erlenmeyer flask , as we chemists call it , which is full of deionised water . so we ’ ve passed the water through a machine which has taken out all of the other ions so that they can ’ t play around with the competition reaction that we want to start today . firstly , i ’ m going to start off by giving the prize of the competition to silver . so here i ’ ve got a sample of silver nitrate . it ’ s sensitive to light so i can ’ t leave it out on the bench very often . so now what i want to do , i ’ m going to put some into the water to make a silver nitrate solution . so i want to make sure that there ’ s plenty in there so that it ’ s saturated . now we ’ ve got to put in the competitor . so what we ’ re going to do , we ’ re going to take some copper , copper metal . and this is just a sample of wire which i ’ ve rubbed with some wire wool just to make it sort of nice and shiny . and now all i ’ m going to do is dangle it into the silver nitrate . then it ’ s going to start to compete for the nitrate and we ’ ll see what happens . so brady ’ s started the recording and i think the best thing for us to do is to go away and do something a little bit more exciting and come back and have a look in an hour . silver has become quite popular recently as a potential new way of making things anti-bacterial : killing bacteria . so now we ’ re going to make some flash powder and the flash powder we ’ re going to make today is a two component mixture . it ’ s very finely ground magnesium and the second component is ground silver nitrate , solid ok . so we take these two components and we mix the two together very intimately and neil ’ s just weighing the materials out right now . so we ’ re going to put the magnesium and the silver nitrate , the two powders , together into a small plastic container here . we ’ re going to mix them very , very carefully and then we ’ re going to see what happens when we initiate a chemical reaction . for hundreds of years people have used silver spoons . partly , i think , because silver is quite easy to make but also because the silver does have properties that kill bacteria so a silver spoon is less likely to get harmful bacteria on it than if you have one that ’ s made out of wood or horn of a cow or something like that . so we ’ re mixing these very carefully , in the fume hood , just in case the chemistry starts before we want it to . and in recent times people have started making very , very fine particles of silver , so called nanoparticles , which can exist in solutions . so here i ’ ve got a solution of silver nanoparticles . you can see it doesn ’ t look silver it looks a bit yellow actually and you can tell that it ’ s got particles in it because , if i can find a torch… so here we ’ ve got particles and you can see the particles better if we shine a light through it and if you look at the light you can see that there is a cone of light that looks rather like the headlights of a car in fog . and this is an effect that ’ s called the tyndall cone which indicates that there are very , very tiny particles suspended in the solution . so this is not silver dissolved in the water but actually very tiny particles . so let ’ s start the reaction , just with a little bit of water . wow ! i think we should do it again though . yeah ! laughter people are now using the silver nanoparticles for all sorts of purposes . here you can see that they ’ ve been put onto some sort of plastic and you can now buy socks which have silver nanoparticles on them which are claimed to kill the bacteria that make your feet smell . so we ’ re going to repeat the reaction . b-b-b-b… squawcks that ’ s going to come out somewhere isn ’ t it ? silver will conduct electricity , it will also conduct heat . if you ’ ve ever tried stirring tea with a silver spoon it gets very hot , you tend to drop it . it also conducts electricity well . so we ’ re going to repeat the reaction so that you can see it again , because that was really fast . this time we ’ re going to do it on a glass dish so you can see it a bit better . we ’ ll pour out a small amount . laughter so our reaction ’ s ready . now all we need again is a little bit of water just to start it off . did you catch that ? i managed to close my eyes this time ( ! ) during the second world war , when the us government was involved in enriching uranium as part of the manhattan project they needed an enormous amount of wire to make magnets . and so a huge amount of silver was taken from the us treasury where it was stored as silver to give value to the us dollar and was turned into wires to make magnets . and i believe that the silver was never returned or at least it wasn ’ t returned at the end of the war as was promised . well , i ’ ve managed to fill maybe one minute ’ s worth of time by now maybe two because we ’ ve been away about two hours . so we ’ re going to go back and have a look at the flask to see if there are any changes . if you remember when we left it was a nice clear solution of silver nitrate with some copper wire which was just immersed inside . so let ’ s go and have a look . there ’ s been big changes in our flask ! so if you look carefully you can see now that the copper wire itself is covered in very , very sharp crystals of silver which have basically become deposited on the surface . copper has now won this chemical reaction . it ’ s now going into the solution ; it ’ s taking the salt element and precipitating solid silver crystals . so if you look carefully , you can see that the colour of the solution has changed . it was colourless , now it ’ s blue which tells me there is another ion , copper , in the solution .
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we ’ re going to mix them very , very carefully and then we ’ re going to see what happens when we initiate a chemical reaction . for hundreds of years people have used silver spoons . partly , i think , because silver is quite easy to make but also because the silver does have properties that kill bacteria so a silver spoon is less likely to get harmful bacteria on it than if you have one that ’ s made out of wood or horn of a cow or something like that .
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what connects ancient silver spoons with modern socks containing silver nanoparticles ?
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( electronic instrumental music ) ( tape rewinding ) - [ sally ] ever been to disneyland ? that was definitely an e ticket . - [ voiceover ] shuttle control houston . that was mission specialist sally ride comparing her flight to disneyland . - [ sally ] i wish that there had been another woman on my flight . i wish that two of us had gone up together . i think it would have been a lot easier . - [ gloria ] it ’ s tough being the first , but you ’ ve done it with incredible grace . you also have the only job in the world that everybody understands . ( laughing ) - [ sally ] my father , i think , was so grateful when i became an astronaut because he did not understand astrophysicist . he couldn ’ t relate to that at all , but astronaut was something he felt he understood . - [ gloria ] but you could see people all over the world connecting with what you were doing . - [ sally ] roughly half the people in the world would love to be astronauts , would give anything to trade places with you , and the other half just can ’ t understand why in the world you would do something that stupid . ( upbeat instrumental music ) - [ gloria ] you don ’ t have 20-20 vision , can you become an astronaut candidate ? i always thought that was a big disabling factor . - [ sally ] i think it used to be . now as long as it ’ s correctable to 20-20 , it ’ s okay . so you ’ d probably qualify . ( laughing ) ( upbeat instrumental music ) i didn ’ t have any dreams about being an astronaut at all and i don ’ t understand that because as soon as the opportunity was open to me , i jumped at it . and i instantly realized that that was what i really wanted to do . i took all the science classes that i could all the way through junior high school and into high school . i went to a girls ’ school that really didn ’ t have a strong science program at all when i was there . at the time it was a classic school for girls , with a good tennis team and a good english teacher and essentially no math past eleventh grade and no physics and no chemistry . - [ gloria ] i ’ m curious about the reception that you got inside nasa . what kind of thing happened to you ? - [ sally ] really the only bad moments in our training involved the press . the press was an added pressure on the flight for me and whereas nasa appeared to be very enlightened about flying women astronauts , the press didn ’ t appear to be . the things that they were concerned with were not the same things that i was concerned with . - [ gloria ] for instance , the bathroom facilities . - [ sally ] the bathroom facilities . - [ gloria ] how much did you get asked that ? - [ sally ] just about every interview i got asked that . everybody wanted to know about what kind of makeup i was taking up . they didn ’ t care about how well-prepared i was to operate the arm or deploy communications satellites . - [ gloria ] did nasa try to prepare you for the press and the pressure ? - [ sally ] unfortunately , no , they don ’ t . you know , in my case , they took a graduate student in physics who had spent her life in the basement of a physics department with oscilloscopes and suddenly put me in front of the press . ( upbeat instrumental music ) - [ gloria ] what do you suppose are the dumbest kinds of questions you ’ ve been asked to date ? - [ sally ] without a doubt , i think the worst question that i have gotten was whether i cried when we got malfunctions in the simulator . ( laughing ) no . - [ gloria ] that surpassed even the one about whether you ’ re going to wear a bra or not . did somebody really ask you that ? - [ sally ] no . the press , i think , decided that that was a good question for someone to have asked me and for me to have answered but i never got that question . - [ gloria ] and they made you up quite a good response . something about `` in a state of weightlessness `` it doesn ’ t matter , '' or something like that ? - [ sally ] yeah , it was something like that . - [ gloria ] they made up this whole thing ? - [ sally ] yeah , i was never asked that question . ( upbeat instrumental music ) - [ gloria ] what about your feelings during the launch ? was there any time that the enormity of what was going on came over you ? - [ sally ] the moment of the launch , when the engines actually ignited and the solid rockets lit , everyone on the crew was , for a few seconds , just overcome with what was about to happen to us . but a year of training is a long time . a year of sitting in simulators and being told exactly what ’ s going to happen . and you hear the sounds and you feel the vibrations . and they prepare you very well and it worked . we were able to overcome being overcome and do the things that we were supposed to do . - [ gloria ] just watching there at the launch , there were people with tears streaming down their faces , people i never would have expected and yet they were all very moved by , i guess , the human audacity of it . - [ sally ] i think that to imagine , when you see the long trail of flame , and then to imagine that there are really people inside that , that ’ s really something . inside , of course , you don ’ t see the long trail of flame and what you ’ re feeling is really more of an exhilaration . - [ gloria ] well , there are lots of people looking up there feeling proud , not only of you up there but also on the ground . thank you . - [ sally ] thank you . ( inspirational instrumental music ) - [ voiceover ] this special episode of blank on blank is made possible by squarespace . squarespace is a easy way to create a website , blog or online store for you and your ideas . try squarespace at squarespace.com/blankonblank for a special offer . ( upbeat instrumental music ) - [ gloria ] what do you think it might be like in 2001 , in fact ? what ’ s possible for us ? - [ sally ] well , 2001 is a long ways in the future to speculate on , but probably the next step after the space shuttle is gon na be to be a space station . i would foresee a space station as being not just something that is orbiting the earth and used for experimentation or whatever , but would also be used as a launching platform back to the moon or to mars . and i think both of those are inevitable . i ’ m sure we ’ ll go back to the moon and i ’ m sure it ’ s only a matter of time before we send people to mars . - [ gloria ] do you have any speculation about how long it might be perhaps before there are such things as peopled space colonies ? - [ sally ] i ’ d guess that probably by the year 2000 there will be . i think that we ’ ll have a space station by the end of this decade . - [ gloria ] on which it would be possible to live for long periods of time ? - [ sally ] yes . ( upbeat instrumental music ) - [ voiceover ] this episode was also supported by the alfred p. sloan foundation . enhancing public understanding of science , technology and economic performance . more information on sloan at sloan.org . ( upbeat instrumental music ) ( tape rewinding ) subtitles by the amara.org community
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did somebody really ask you that ? - [ sally ] no . the press , i think , decided that that was a good question for someone to have asked me and for me to have answered but i never got that question .
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when sally ride 's space craft finally launched , she says she and the crew were completely overwhelmed . what does she say kept her focused in this high-pressure situation ?
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physicists , air traffic controllers , and video game creators all have at least one thing in common : vectors . what exactly are they , and why do they matter ? to answer , we first need to understand scalars . a scalar is a quantity with magnitude . it tells us how much of something there is . the distance between you and a bench , and the volume and temperature of the beverage in your cup are all described by scalars . vector quantities also have a magnitude plus an extra piece of information , direction . to navigate to your bench , you need to know how far away it is and in what direction , not just the distance , but the displacement . what makes vectors special and useful in all sorts of fields is that they do n't change based on perspective but remain invariant to the coordinate system . what does that mean ? let 's say you and a friend are moving your tent . you stand on opposite sides so you 're facing in opposite directions . your friend moves two steps to the right and three steps forward while you move two steps to the left and three steps back . but even though it seems like you 're moving differently , you both end up moving the same distance in the same direction following the same vector . no matter which way you face , or what coordinate system you place over the camp ground , the vector does n't change . let 's use the familiar cartesian coordinate system with its x and y axes . we call these two directions our coordinate basis because they 're used to describe everything we graph . let 's say the tent starts at the origin and ends up over here at point b . the straight arrow connecting the two points is the vector from the origin to b . when your friend thinks about where he has to move , it can be written mathematically as 2x + 3y , or , like this , which is called an array . since you 're facing the other way , your coordinate basis points in opposite directions , which we can call x prime and y prime , and your movement can be written like this , or with this array . if we look at the two arrays , they 're clearly not the same , but an array alone does n't completely describe a vector . each needs a basis to give it context , and when we properly assign them , we see that they are in fact describing the same vector . you can think of elements in the array as individual letters . just as a sequence of letters only becomes a word in the context of a particular language , an array acquires meaning as a vector when assigned a coordinate basis . and just as different words in two languages can convey the same idea , different representations from two bases can describe the same vector . the vector is the essence of what 's being communicated , regardless of the language used to describe it . it turns out that scalars also share this coordinate invariance property . in fact , all quantities with this property are members of a group called tensors . various types of tensors contain different amounts of information . does that mean there 's something that can convey more information than vectors ? absolutely . say you 're designing a video game , and you want to realistically model how water behaves . even if you have forces acting in the same direction with the same magnitude , depending on how they 're oriented , you might see waves or whirls . when force , a vector , is combined with another vector that provides orientation , we have the physical quantity called stress , which is an example of a second order tensor . these tensors are also used outside of video games for all sorts of purposes , including scientific simulations , car designs , and brain imaging . scalars , vectors , and the tensor family present us with a relatively simple way of making sense of complex ideas and interactions , and as such , they 're a prime example of the elegance , beauty , and fundamental usefulness of mathematics .
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various types of tensors contain different amounts of information . does that mean there 's something that can convey more information than vectors ? absolutely .
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which of the following statements is/are true about vectors ?
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good morning . how are you ? ( laughter ) it 's been great , has n't it ? i 've been blown away by the whole thing . in fact , i 'm leaving . ( laughter ) there have been three themes running through the conference which are relevant to what i want to talk about . one is the extraordinary evidence of human creativity in all of the presentations that we 've had and in all of the people here . just the variety of it and the range of it . the second is that it 's put us in a place where we have no idea what 's going to happen , in terms of the future . no idea how this may play out . i have an interest in education . actually , what i find is everybody has an interest in education . do n't you ? i find this very interesting . if you 're at a dinner party , and you say you work in education -- actually , you 're not often at dinner parties , frankly . ( laughter ) if you work in education , you 're not asked . ( laughter ) and you 're never asked back , curiously . that 's strange to me . but if you are , and you say to somebody , you know , they say , `` what do you do ? '' and you say you work in education , you can see the blood run from their face . they 're like , `` oh my god , '' you know , `` why me ? '' ( laughter ) `` my one night out all week . '' ( laughter ) but if you ask about their education , they pin you to the wall . because it 's one of those things that goes deep with people , am i right ? like religion , and money and other things . so i have a big interest in education , and i think we all do . we have a huge vested interest in it , partly because it 's education that 's meant to take us into this future that we ca n't grasp . if you think of it , children starting school this year will be retiring in 2065 . nobody has a clue , despite all the expertise that 's been on parade for the past four days , what the world will look like in five years ' time . and yet we 're meant to be educating them for it . so the unpredictability , i think , is extraordinary . and the third part of this is that we 've all agreed , nonetheless , on the really extraordinary capacities that children have -- their capacities for innovation . i mean , sirena last night was a marvel , was n't she ? just seeing what she could do . and she 's exceptional , but i think she 's not , so to speak , exceptional in the whole of childhood . what you have there is a person of extraordinary dedication who found a talent . and my contention is , all kids have tremendous talents . and we squander them , pretty ruthlessly . so i want to talk about education and i want to talk about creativity . my contention is that creativity now is as important in education as literacy , and we should treat it with the same status . ( applause ) thank you . ( applause ) that was it , by the way . thank you very much . ( laughter ) so , 15 minutes left . ( laughter ) well , i was born ... no . ( laughter ) i heard a great story recently -- i love telling it -- of a little girl who was in a drawing lesson . she was six , and she was at the back , drawing , and the teacher said this girl hardly ever paid attention , and in this drawing lesson , she did . the teacher was fascinated . she went over to her , and she said , `` what are you drawing ? '' and the girl said , `` i 'm drawing a picture of god . '' and the teacher said , `` but nobody knows what god looks like . '' and the girl said , `` they will , in a minute . '' ( laughter ) when my son was four in england -- actually , he was four everywhere , to be honest . ( laughter ) if we 're being strict about it , wherever he went , he was four that year . he was in the nativity play . do you remember the story ? ( laughter ) no , it was big , it was a big story . mel gibson did the sequel , you may have seen it . ( laughter ) `` nativity ii . '' but james got the part of joseph , which we were thrilled about . we considered this to be one of the lead parts . we had the place crammed full of agents in t-shirts : `` james robinson is joseph ! '' ( laughter ) he did n't have to speak , but you know the bit where the three kings come in ? they come in bearing gifts , gold , frankincense and myrrh . this really happened . we were sitting there and i think they just went out of sequence , because we talked to the little boy afterward and we said , `` you ok with that ? '' and he said , `` yeah , why ? was that wrong ? '' they just switched . the three boys came in , four-year-olds with tea towels on their heads , and they put these boxes down , and the first boy said , `` i bring you gold . '' and the second boy said , `` i bring you myrrh . '' and the third boy said , `` frank sent this . '' ( laughter ) what these things have in common is that kids will take a chance . if they do n't know , they 'll have a go . am i right ? they 're not frightened of being wrong . i do n't mean to say that being wrong is the same thing as being creative . what we do know is , if you 're not prepared to be wrong , you 'll never come up with anything original -- if you 're not prepared to be wrong . and by the time they get to be adults , most kids have lost that capacity . they have become frightened of being wrong . and we run our companies like this . we stigmatize mistakes . and we 're now running national education systems where mistakes are the worst thing you can make . and the result is that we are educating people out of their creative capacities . picasso once said this , he said that all children are born artists . the problem is to remain an artist as we grow up . i believe this passionately , that we do n't grow into creativity , we grow out of it . or rather , we get educated out of it . so why is this ? i lived in stratford-on-avon until about five years ago . in fact , we moved from stratford to los angeles . so you can imagine what a seamless transition that was . ( laughter ) actually , we lived in a place called snitterfield , just outside stratford , which is where shakespeare 's father was born . are you struck by a new thought ? i was . you do n't think of shakespeare having a father , do you ? do you ? because you do n't think of shakespeare being a child , do you ? shakespeare being seven ? i never thought of it . i mean , he was seven at some point . he was in somebody 's english class , was n't he ? ( laughter ) how annoying would that be ? ( laughter ) `` must try harder . '' ( laughter ) being sent to bed by his dad , you know , to shakespeare , `` go to bed , now ! and put the pencil down . '' ( laughter ) `` and stop speaking like that . '' ( laughter ) `` it 's confusing everybody . '' ( laughter ) anyway , we moved from stratford to los angeles , and i just want to say a word about the transition . my son did n't want to come . i 've got two kids ; he 's 21 now , my daughter 's 16 . he did n't want to come to los angeles . he loved it , but he had a girlfriend in england . this was the love of his life , sarah . he 'd known her for a month . ( laughter ) mind you , they 'd had their fourth anniversary , because it 's a long time when you 're 16 . he was really upset on the plane , he said , `` i 'll never find another girl like sarah . '' and we were rather pleased about that , frankly -- ( laughter ) because she was the main reason we were leaving the country . ( laughter ) but something strikes you when you move to america and travel around the world : every education system on earth has the same hierarchy of subjects . every one . does n't matter where you go . you 'd think it would be otherwise , but it is n't . at the top are mathematics and languages , then the humanities , and at the bottom are the arts . everywhere on earth . and in pretty much every system too , there 's a hierarchy within the arts . art and music are normally given a higher status in schools than drama and dance . there is n't an education system on the planet that teaches dance everyday to children the way we teach them mathematics . why ? why not ? i think this is rather important . i think math is very important , but so is dance . children dance all the time if they 're allowed to , we all do . we all have bodies , do n't we ? did i miss a meeting ? ( laughter ) truthfully , what happens is , as children grow up , we start to educate them progressively from the waist up . and then we focus on their heads . and slightly to one side . if you were to visit education , as an alien , and say `` what 's it for , public education ? '' i think you 'd have to conclude , if you look at the output , who really succeeds by this , who does everything that they should , who gets all the brownie points , who are the winners -- i think you 'd have to conclude the whole purpose of public education throughout the world is to produce university professors . is n't it ? they 're the people who come out the top . and i used to be one , so there . ( laughter ) and i like university professors , but you know , we should n't hold them up as the high-water mark of all human achievement . they 're just a form of life , another form of life . but they 're rather curious , and i say this out of affection for them . there 's something curious about professors in my experience -- not all of them , but typically , they live in their heads . they live up there , and slightly to one side . they 're disembodied , you know , in a kind of literal way . they look upon their body as a form of transport for their heads . ( laughter ) do n't they ? it 's a way of getting their head to meetings . ( laughter ) if you want real evidence of out-of-body experiences , get yourself along to a residential conference of senior academics , and pop into the discotheque on the final night . ( laughter ) and there , you will see it . grown men and women writhing uncontrollably , off the beat . ( laughter ) waiting until it ends so they can go home and write a paper about it . ( laughter ) our education system is predicated on the idea of academic ability . and there 's a reason . around the world , there were no public systems of education , really , before the 19th century . they all came into being to meet the needs of industrialism . so the hierarchy is rooted on two ideas . number one , that the most useful subjects for work are at the top . so you were probably steered benignly away from things at school when you were a kid , things you liked , on the grounds that you would never get a job doing that . is that right ? do n't do music , you 're not going to be a musician ; do n't do art , you wo n't be an artist . benign advice -- now , profoundly mistaken . the whole world is engulfed in a revolution . and the second is academic ability , which has really come to dominate our view of intelligence , because the universities designed the system in their image . if you think of it , the whole system of public education around the world is a protracted process of university entrance . and the consequence is that many highly-talented , brilliant , creative people think they 're not , because the thing they were good at at school was n't valued , or was actually stigmatized . and i think we ca n't afford to go on that way . in the next 30 years , according to unesco , more people worldwide will be graduating through education than since the beginning of history . more people , and it 's the combination of all the things we 've talked about -- technology and its transformation effect on work , and demography and the huge explosion in population . suddenly , degrees are n't worth anything . is n't that true ? when i was a student , if you had a degree , you had a job . if you did n't have a job , it 's because you did n't want one . and i did n't want one , frankly . ( laughter ) but now kids with degrees are often heading home to carry on playing video games , because you need an ma where the previous job required a ba , and now you need a phd for the other . it 's a process of academic inflation . and it indicates the whole structure of education is shifting beneath our feet . we need to radically rethink our view of intelligence . we know three things about intelligence . one , it 's diverse . we think about the world in all the ways that we experience it . we think visually , we think in sound , we think kinesthetically . we think in abstract terms , we think in movement . secondly , intelligence is dynamic . if you look at the interactions of a human brain , as we heard yesterday from a number of presentations , intelligence is wonderfully interactive . the brain is n't divided into compartments . in fact , creativity -- which i define as the process of having original ideas that have value -- more often than not comes about through the interaction of different disciplinary ways of seeing things . by the way , there 's a shaft of nerves that joins the two halves of the brain called the corpus callosum . it 's thicker in women . following off from helen yesterday , this is probably why women are better at multi-tasking . because you are , are n't you ? there 's a raft of research , but i know it from my personal life . if my wife is cooking a meal at home -- which is not often , thankfully . ( laughter ) no , she 's good at some things , but if she 's cooking , she 's dealing with people on the phone , she 's talking to the kids , she 's painting the ceiling , she 's doing open-heart surgery over here . if i 'm cooking , the door is shut , the kids are out , the phone 's on the hook , if she comes in i get annoyed . i say , `` terry , please , i 'm trying to fry an egg in here . '' ( laughter ) `` give me a break . '' ( laughter ) actually , do you know that old philosophical thing , if a tree falls in a forest and nobody hears it , did it happen ? remember that old chestnut ? i saw a great t-shirt recently , which said , `` if a man speaks his mind in a forest , and no woman hears him , is he still wrong ? '' ( laughter ) and the third thing about intelligence is , it 's distinct . i 'm doing a new book at the moment called `` epiphany , '' which is based on a series of interviews with people about how they discovered their talent . i 'm fascinated by how people got to be there . it 's really prompted by a conversation i had with a wonderful woman who maybe most people have never heard of , gillian lynne . have you heard of her ? some have . she 's a choreographer , and everybody knows her work . she did `` cats '' and `` phantom of the opera . '' she 's wonderful . i used to be on the board of the royal ballet , as you can see . anyway , gillian and i had lunch one day and i said , `` how did you get to be a dancer ? '' it was interesting . when she was at school , she was really hopeless . and the school , in the '30s , wrote to her parents and said , `` we think gillian has a learning disorder . '' she could n't concentrate ; she was fidgeting . i think now they 'd say she had adhd . would n't you ? but this was the 1930s , and adhd had n't been invented at this point . it was n't an available condition . ( laughter ) people were n't aware they could have that . ( laughter ) anyway , she went to see this specialist . so , this oak-paneled room , and she was there with her mother , and she was led and sat on this chair at the end , and she sat on her hands for 20 minutes while this man talked to her mother about the problems gillian was having at school . because she was disturbing people ; her homework was always late ; and so on , little kid of eight . in the end , the doctor went and sat next to gillian , and said , `` i 've listened to all these things your mother 's told me , i need to speak to her privately . wait here . we 'll be back ; we wo n't be very long , '' and they went and left her . but as they went out of the room , he turned on the radio that was sitting on his desk . and when they got out , he said to her mother , `` just stand and watch her . '' and the minute they left the room , she was on her feet , moving to the music . and they watched for a few minutes and he turned to her mother and said , `` mrs. lynne , gillian is n't sick ; she 's a dancer . take her to a dance school . '' i said , `` what happened ? '' she said , `` she did . i ca n't tell you how wonderful it was . we walked in this room and it was full of people like me . people who could n't sit still . people who had to move to think . '' who had to move to think . they did ballet , they did tap , jazz ; they did modern ; they did contemporary . she was eventually auditioned for the royal ballet school ; she became a soloist ; she had a wonderful career at the royal ballet . she eventually graduated from the royal ballet school , founded the gillian lynne dance company , met andrew lloyd webber . she 's been responsible for some of the most successful musical theater productions in history , she 's given pleasure to millions , and she 's a multi-millionaire . somebody else might have put her on medication and told her to calm down . ( applause ) what i think it comes to is this : al gore spoke the other night about ecology and the revolution that was triggered by rachel carson . i believe our only hope for the future is to adopt a new conception of human ecology , one in which we start to reconstitute our conception of the richness of human capacity . our education system has mined our minds in the way that we strip-mine the earth : for a particular commodity . and for the future , it wo n't serve us . we have to rethink the fundamental principles on which we 're educating our children . there was a wonderful quote by jonas salk , who said , `` if all the insects were to disappear from the earth , within 50 years all life on earth would end . if all human beings disappeared from the earth , within 50 years all forms of life would flourish . '' and he 's right . what ted celebrates is the gift of the human imagination . we have to be careful now that we use this gift wisely and that we avert some of the scenarios that we 've talked about . and the only way we 'll do it is by seeing our creative capacities for the richness they are and seeing our children for the hope that they are . and our task is to educate their whole being , so they can face this future . by the way -- we may not see this future , but they will . and our job is to help them make something of it . thank you very much . ( applause )
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and the second boy said , `` i bring you myrrh . '' and the third boy said , `` frank sent this . '' ( laughter ) what these things have in common is that kids will take a chance .
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what do the stories about the girl who drew a picture of god and the boy who said `` frank sent this '' in the nativity play tell us about children 's creativity ?
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a handful of species on earth share a seemingly mysterious trait : a menstrual cycle . we 're one of the select few . monkeys , apes , bats , humans , and possibly elephant shrews are the only mammals on earth that menstruate . we also do it more than any other animal , even though its a waste of nutrients and can be a physical inconvenience . so where 's the sense in this uncommon biological process ? the answer begins with pregnancy . during this process , the body 's resources are cleverly used to shape a suitable environment for a fetus , creating an internal haven for a mother to nurture her growing child . in this respect , pregnancy is awe-inspiring , but that 's only half the story . the other half reveals that pregnancy places a mother and her child at odds . as for all living creatures , the human body evolved to promote the spread of its genes . for the mother , that means she should try to provide equally for all her offspring . but a mother and her fetus do n't share exactly the same genes . the fetus inherits genes from its father , as well , and those genes can promote their own survival by extracting more than their fair share of resources from the mother . this evolutionary conflict of interests places a woman and her unborn child in a biological tug-of-war that plays out inside the womb . one factor contributing to this internal tussle is the placenta , the fetal organ that connects to the mother 's blood supply and nourishes the fetus while it grows . in most mammals , the placenta is confined behind a barrier of maternal cells . this barrier lets the mother control the supply of nutrients to the fetus . but in humans and a few other species , the placenta actually penetrates right into the mother 's circulatory system to directly access her blood stream . through its placenta , the fetus pumps the mother 's arteries with hormones that keep them open to provide a permanent flow of nutrient-rich blood . a fetus with such unrestricted access can manufacture hormones to increase the mother 's blood sugar , dilate her arteries , and inflate her blood pressure . most mammal mothers can expel or reabsorb embryos if required , but in humans , once the fetus is connected to the blood supply , severing that connection can result in hemorrhage . if the fetus develops poorly or dies , the mother 's health is endangered . as it grows , a fetus 's ongoing need for resources can cause intense fatigue , high blood pressure , and conditions like diabetes and preeclampsia . because of these risks , pregnancy is always a huge , and sometimes dangerous , investment . so it makes sense that the body should screen embryos carefully to find out which ones are worth the challenge . this is where menstruation fits in . pregnancy starts with a process called implantation , where the embryo embeds itself in the endometrium that lines the uterus . the endometrium evolved to make implantation difficult so that only the healthy embryos could survive . but in doing so , it also selected for the most vigorously invasive embryos , creating an evolutionary feedback loop . the embryo engages in a complex , exquisitely timed hormonal dialogue that transforms the endometrium to allow implantation . what happens when an embryo fails the test ? it might still manage to attach , or even get partly through the endometrium . as it slowly dies , it could leave its mother vulnerable to infection , and all the time , it may be emitting hormonal signals that disrupt her tissues . the body avoids this problem by simply removing every possible risk . each time ovulation does n't result in a healthy pregnancy , the womb gets rid of its endometrial lining , along with any unfertilized eggs , sick , dying , or dead embryos . that protective process is known as menstruation , leading to the period . this biological trait , bizarre as it may be , sets us on course for the continuation of the human race .
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this evolutionary conflict of interests places a woman and her unborn child in a biological tug-of-war that plays out inside the womb . one factor contributing to this internal tussle is the placenta , the fetal organ that connects to the mother 's blood supply and nourishes the fetus while it grows . in most mammals , the placenta is confined behind a barrier of maternal cells .
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the fetal organ that connects the mother 's blood supply and nourishes the fetus while it grows is the :
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translator : andrea mcdonough reviewer : bedirhan cinar every human being starts out the same way : two cells , one from each parent , found each other and became one . and that one cell reproduced itself , dividing , dividing and dividing until there were 10 trillion of them . do you realize there 's more cells in one person 's body than there are stars in the milky way ? but those 10 trillion cells are n't just sitting there in a big pile . that would make for a pretty boring human being ! so what is it that says a nose is a nose , and toes is toes ? what is it that says this is bone and this is brain and this is heart and this is that little thing in the back of your throat you can never remember the name of ? everything you are or ever will be made of starts as a tiny book of instructions found in each and every cell . every time your body wants to make something , it goes back to the instruction book , looks it up and puts it together . so how does one cell hold all that information ? let 's get small . i mean , really small -- smaller than the tip of a sewing needle . then we can take a journey inside a single cell to find out what makes up the book of you , your genome . the first thing we see is that the whole genome , all your dna , is contained inside its own tiny compartment , called the nucleus . if we stretched out all the dna in this one cell into a single thread , it would be over 3 feet long ! we have to make it fit in a tiny compartment that 's a million times smaller . we could just bunch it up like christmas lights , but that could get messy . we need some organization . first , the long thread of dna wraps around proteins clustered into little beads called nucleosomes , which end up looking like a long , beaded necklace . and that necklace is wrapped up in its own spiral , like an old telephone cord . and those spirals get layered on top of one another until we get a neat little shape that fits inside the nucleus . voilà ! three feet of dna squeezed into a tiny compartment . if only we could hire dna to pack our suitcases ! each tiny mass of dna is called a chromosome . the book of you would have 46 chapters , one for each chromosome . twenty-three chapters of your book came from your mom , and 23 chapters came from your dad . two of those chapters , called `` x '' and `` y , '' determine if you 're male , `` xy , '' or female , `` xx . '' put them together , and we get two almost identical but slightly different sets of 23 chapters . the tiny variations are what makes each person different . it 's estimated that all the chapters together hold about 20,000 individual instructions , called genes . written out , all those 20,000 instructions are 30 million letters long ! if someone were writing one letter per second , it would take them almost an entire year to write it once . it turns out that our genome book is much , much longer than just those 30 million letters -- almost 100 times longer ! what are all those extra pages for ? well , each page of instructions has a few pages of nonsense inserted that have to be taken out before we end up with something useful . the parts we throw out , we call introns . the instructions we keep , we call exons . we can also have hundreds of pages in between each gene . some of these excess pages were inserted by nasty little infections in our ancestors , but some of them are actually helpful . they protect the ends of each chapter from being damaged , or some help our cells find a particular thing they 're looking for , or give a cell a signal to stop making something . all in all , for every page of instructions , there 's almost 100 pages of filler . in the end , each of our books ' 46 chapters is between 48 and 250 million letters long . that 's 3.2 billion letters total ! to type all that copy , you 'd be at it for over 100 years , and the book would be over 600,000 pages long . every type of cell carries the same book , but each has a set of bookmarks that tell it exactly which pages it needs to look up . so a bone cell reads only the set of instructions it needs to become bone . your brain cells , they read the set that tells them how to become brain . if some cells suddenly decide to start reading other instructions , they can actually change from one type to another . so every little cell in your body is holding on to an amazing book , full of the instructions for life . your nose reads nose pages , your toes read toes pages . and that little thing in the back of your throat ? it 's got its own pages , too . they 're under `` uvula . ''
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every type of cell carries the same book , but each has a set of bookmarks that tell it exactly which pages it needs to look up . so a bone cell reads only the set of instructions it needs to become bone . your brain cells , they read the set that tells them how to become brain .
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explain in your own words how some cells know to be muscle and some know to be bone .
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the city has just opened its one-of-a-kind fabergé egg museum with a single egg displayed on each floor of a 100-story building . and the world 's most notorious jewel thief already has her eyes on the prize . because security is tight and the eggs are so large , she 'll only get the chance to steal one by dropping it out the window into her waiting truck and repelling down before the police can arrive . all eggs are identical in weight and construction , but each floor 's egg is more rare and valuable than the one below it . while the thief would naturally like to take the priceless egg at the top , she suspects it wo n't survive a 100-story drop . being pragmatic , she decides to settle for the most expensive egg she can get . in the museum 's gift shop , she finds two souvenir eggs , perfect replicas that are perfectly worthless . the plan is to test drop them to find the highest floor at which an egg will survive the fall without breaking . of course , the experiment can only be repeated until both replica eggs are smashed . and throwing souvenirs out the window too many times is probably going to draw the guards ' attention . what 's the least number of tries it would take to guarantee that she find the right floor ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 if you 're having trouble getting started on the solution , it might help to start with a simpler scenario . imagine our thief only had one replica egg . she 'd have a single option : to start by dropping it from the first floor and go up one by one until it breaks . then she 'd know that the floor below that is the one she needs to target for the real heist . but this could require as many as 100 tries . having an additional replica egg gives the thief a better option . she can drop the first egg from different floors at larger intervals in order to narrow down the range where the critical floor can be found . and once the first breaks , she can use the second egg to explore that interval floor by floor . large floor intervals do n't work great . in the worst case scenario , they require many tests with the second egg . smaller intervals work much better . for example , if she starts by dropping the first egg from every 10th floor , once it breaks , she 'll only have to test the nine floors below . that means it 'll take at most 19 tries to find the right floor . but can she do even better ? after all , there 's no reason every interval has to be the same size . let 's say there were only ten floors . the thief could test this whole building with just four total throws by dropping the first egg at floors four , seven , and nine . if it broke at floor four , it would take up to three throws of the second egg to find the exact floor . if it broke at seven , it would take up to two throws with the second egg . and if it broke at floor nine , it would take just one more throw of the second egg . intuitively , what we 're trying to do here is divide the building into sections where no matter which floor is correct , it takes up to the same number of throws to find it . we want each interval to be one floor smaller than the last . this equation can help us solve for the first floor we need to start with in the 100 floor building . there are several ways to solve this equation , including trial and error . if we plug in two for n , that equation would look like this . if we plug in three , we get this . so we can find the first n to pass 100 by adding more terms until we get to our answer , which is 14 . and so our thief starts on the 14th floor , moving up to the 27th , the 39th , and so on , for a maximum of 14 drops . like the old saying goes , you ca n't pull a heist without breaking a few eggs .
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and throwing souvenirs out the window too many times is probably going to draw the guards ' attention . what 's the least number of tries it would take to guarantee that she find the right floor ? pause here if you want to figure it out for yourself !
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let ’ s generalize to buildings with different heights . find an equation that relates the number of floors to the least number of tries .
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[ why do n't we eat bugs ? ] for centuries , people have consumed bugs , everything from beetles to caterpillars , locusts , grasshoppers , termites , and dragonflies . the practice even has a name : entomophagy . early hunter-gatherers probably learned from animals that foraged for protein-rich insects and followed suit . as we evolved and bugs became part of our dietary tradition , they fulfilled the role of both staple food and delicacy . in ancient greece , cicadas were considered luxury snacks . and even the romans found beetle larvae to be scrumptious . why have we lost our taste for bugs ? the reason for our rejection is historical , and the story probably begins around 10,000 bc in the fertile crescent , a place in the middle east that was a major birthplace of agriculture . back then , our once-nomadic ancestors began to settle in the crescent . and as they learned to farm crops and domesticate animals there , attitudes changed , rippling outwards towards europe and the rest of the western world . as farming took off , people might have spurned bugs as mere pests that destroyed their crops . populations grew , and the west became urbanized , weakening connections with our foraging past . people simply forgot their bug-rich history . today , for people not accustomed to entomophagy , bugs are just an irritant . they sting and bite and infest our food . we feel an `` ick factor '' associated with them and are disgusted by the prospect of cooking insects . almost 2,000 insect species are turned into food , forming a big part of everyday diets for two billion people around the world . countries in the tropics are the keenest consumers , because culturally , it 's acceptable . species in those regions are also large , diverse , and tend to congregate in groups or swarms that make them easy to harvest . take cambodia in southeast asia where huge tarantulas are gathered , fried , and sold in the marketplace . in southern africa , the juicy mopane worm is a dietary staple , simmered in a spicy sauce or eaten dried and salted . and in mexico , chopped jumiles are toasted with garlic , lemon , and salt . bugs can be eaten whole to make up a meal or ground into flour , powder , and paste to add to food . but it 's not all about taste . they 're also healthy . in fact , scientists say entomophagy could be a cost-effective solution for developing countries that are food insecure . insects can contain up to 80 % protein , the body 's vital building blocks , and are also high in energy-rich fat , fiber , and micronutrients like vitamins and minerals . did you know that most edible insects contain the same amount or even more mineral iron than beef , making them a huge , untapped resource when you consider that iron deficiency is currently the most common nutritional problem in the world ? the mealworm is another nutritious example . the yellow beetle larvae are native to america and easy to farm . they have a high vitamin content , loads of healthy minerals , and can contain up to 50 % protein , almost as much as in an equivalent amount of beef . to cook , simply sauté in butter and salt or roast and drizzle with chocolate for a crunchy snack . what you have to overcome in `` ick factor , '' you gain in nutrition and taste . indeed , bugs can be delicious . mealworms taste like roasted nuts . locusts are similar to shrimp . crickets , some people say , have an aroma of popcorn . farming insects for food also has less environmental impact than livestock farms do because insects emit far less greenhouse gas and use up less space , water , and food . socioeconomically , bug production could uplift people in developing countries since insect farms can be small scale , highly productive , and yet relatively inexpensive to keep . insects can also be turned into more sustainable food for livestock and can be reared on organic waste , like vegetable peelings , that might otherwise just end up rotting in landfills . feeling hungry yet ? faced with a plate of fried crickets , most people today would still recoil , imagining all those legs and feelers getting stuck between their teeth . but think of a lobster . it 's pretty much just a giant insect with legs and feelers galore that was once regarded as an inferior , repulsive food . now , lobster is a delicacy . can the same paradigm shift happen for bugs ? so , give it a try ! pop that insect into your mouth , and savor the crunch .
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we feel an `` ick factor '' associated with them and are disgusted by the prospect of cooking insects . almost 2,000 insect species are turned into food , forming a big part of everyday diets for two billion people around the world . countries in the tropics are the keenest consumers , because culturally , it 's acceptable .
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how many different insect species do people eat around the world ?
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how 's this for a strange idea : a day off from work in honor of work itself ? actually , that is what labor day , celebrated in the united states and canada on the first monday of every september , is all about . the first american labor day was celebrated in new york city on september 5th , 1882 , as thousands of workers and their families came to union square for a day in the park . it was not a national holiday but had been organized by a union to honor workers and their hard efforts with a rare day of rest , halfway between july 4th and thanksgiving . there were picnics and a parade , but there were also protests . the workers had gathered , not just to rest and celebrate , but to demand fair wages , the end of child labor , and the right to organize into unions . during the period known as the industrial revolution , many jobs were difficult , dirty and dangerous . people worked for twelve hours , six days a week , without fringe benefits , such as vacations , health care and pensions , and if you were young , chances are you were doing manual labor instead of your abcs and fractions . children as young as ten worked in some of the most hazardous places , like coal mines or factories filled with boiling vats or dangerous machines . trying to win better pay , shorter hours and safer conditions workers had begun to form labor unions in america and canada , but the companies they worked for often fought hard to keep unions out and to supress strikes . at times , this led to violent battles between workers and business owners with the owners often backed up by the police , or even the military . in the following years , the idea of labor day caught on in america with official celebrations reaching 30 states . but then came the violent haymarket square riot of 1886 , which led to the deaths of several policemen and workers in chicago and the execution of four union leaders . after that , many labor and political groups around the world had begun to mark haymarket square on may 1st , which became known as international workers ' day . in 1894 , president grover cleveland signed the law making labor day a federal holiday in america , only days after he had sent 12,000 soldiers to end a violent railroad strike that resulted in the death of several people . the original september date was kept , partly to avoid the more radical associations of may 1st . canada also created its labor day in 1894 . but , in spite of this new holiday , it would be a long time before the changes that workers wanted became a reality . in 1938 , during the great depression that left millions without jobs , president franklin d. roosevelt signed a law calling for an eight-hour work day , a five-day work week , and an end to child labor , some of the first federal protections for american workers . as america and canada celebrate labor day , most of the two countries ' children enjoy a day off from school . but it is important to remember that there was a time that everyday was a labor day for children in america and canada , and unfortunately , the same fact remains true for millions of children around the world today .
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how 's this for a strange idea : a day off from work in honor of work itself ? actually , that is what labor day , celebrated in the united states and canada on the first monday of every september , is all about . the first american labor day was celebrated in new york city on september 5th , 1882 , as thousands of workers and their families came to union square for a day in the park .
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labor day is celebrated in america and canada on the first monday in :
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translator : andrea mcdonough reviewer : jessica ruby worst case scenario : zombie apocalypse . how will you survive ? you might be surprised to find out how much geography skills can help you fend off doom . by geography , i mean analyzing the world around you . one geographic concept that could really help you out in a zombie apocalypse is movement . so , first , what moves ? people move , animals move , and , while sometimes slowly , zombies move as well . but that 's not all . goods move , too . goods can be resources , such as food supplies and weapons . people or zombies tend to move these . so , if you see a big pile of zombie supplies where there was n't one before , you 're probably on the trail . ideas also move . ideas can include entertainment , zombie movies , news and information about zombie attacks , and architecture , or how to build a safe shelter . and , second , why do people or zombies move ? when people , animals , or zombies move , it 's called migration . two concepts that affect migration are push and pull factors . push factors will make you want to leave somewhere . pull factors make you want to go to a place . a lack of resources , unstable economy , or high crime rate might be push factors making people want to move . nice weather , a good economy , or lots of resources would be pull factors for lots of people , enticing them to move . while zombies are definitely a push factor for humans , a city full of people would be a pull factor for hungry zombies who want to eat humans . there are some things that make movement easier for people or zombies . waterways and highways can make traveling faster . moving across clear , open space is easier than a tough terrain . and just as land forms can create boundaries that affect movement , so can political boundaries , like a border gate , for example . so , how can you analyze these movement factors to help your chance of survival ? there are three basic steps . one - identify the points or locations to analyze . what are your options ? two - find what connects them . are there highways , waterways , or open land ? and three - find the patterns of movement that happen over that connection . do people or goods move across it ? by comparing relationships between different places , you can see what connections they have . for example , pick two cities . look at the highway connecting them . if people use that highway to commute to work , those cities have a strong relationship . but this other city over here does n't have a direct connection to the other cities . there 's even a river in the way . it does n't have as strong of a relationship . if a zombie outbreak started here , which city would you rather start out in ? where would you flee to ? so , how do you decide where to go in a zombie apocalypse ? do you just run in a random direction ? or do you use your geographic skills to lead your camp of survivors to safety ? if you want to stay alive , it helps to understand how and why we move .
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so , if you see a big pile of zombie supplies where there was n't one before , you 're probably on the trail . ideas also move . ideas can include entertainment , zombie movies , news and information about zombie attacks , and architecture , or how to build a safe shelter .
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what are some examples of ideas that move ?
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there is an environmental mystery afoot , and it begins with a seemingly trivial detail that reveals a disaster of global proportions . one day , you notice that the honey you slather on your morning toast is more expensive . instead of switching to jam , you investigate the reason for the price hike . what you find is shocking . the number of domesticated honeybees in the us has been decreasing at an alarming rate . this decline appears too big to be explained by the usual causes of bee death alone : disease , parasites or starvation . a typical crime scene has almost no adult bees left in the hive , except , perhaps , a lonely queen and a few other survivors . it 's full of untouched food stores and a brood of unborn larvae , suggesting that the adults vacated without waiting for them to hatch . but what 's particularly eerie is that there 's no tell-tale mass of dead or dying bees nearby . either they have forgotten their way back to the hive , or they have simply disappeared . these mysterious disappearances are n't new . humans have been collecting honey for centuries . but it was n't until european settlers in the 1600 's introduced the subspecies , apis mellifera , that we domesticated bees . since the 19th century , beekeepers have reported occasional mass disappearances , giving them enigmatic names like disappearing disease , spring dwindle disease and autumn collapse . but when in 2006 such losses were found to affect more than half of all hives in the us , the phenomenon got a new name : colony collapse disorder . the most frightening thing about this mystery is n't that we 'll have to go back to using regular sugar in our tea . we farm bees for their honey , but they also pollinate our crops on an industrial scale , generating over 1/3 of america 's food production this way . so , how can we find the culprit behind this calamity ? here are three of the possible offenders . exhibit a : pests and disease . most infamous is the varroa mite , a minuscule red pest that not only invades colonies and feeds on bees , but also transfers pathogens that stunt bee growth and shortens their life span . exhibit b : genetics . the queen is the core of a healthy hive . but nowadays , the millions of queen bees distributed in commercial hives are bred from just a few original queens , which raises the worry about a lack of genetic diversity which could weaken bees ' defenses against pathogens and pests . exhibit c : chemicals . pesticides used both on commercial beehives and agricultural crops to ward off parasites could be getting into the food and water that honeybees consume . researchers have even found that some pesticides damage the honeybees ' homing abilities . so we have a file full of clues but no clear leads . in reality , scientists , the actual detectives on this case , face disagreement over what causes colony collapse disorder . for now , we assume that several factors are the cause . honeybees are n't necessarily in danger of extinction , but fewer bees overall means less pollination and higher food costs , so it 's crucial that scientists solve the case of the vanishing bees . because while having less honey might be a buzzkill , crop shortages are something that would truly sting .
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these mysterious disappearances are n't new . humans have been collecting honey for centuries . but it was n't until european settlers in the 1600 's introduced the subspecies , apis mellifera , that we domesticated bees . since the 19th century , beekeepers have reported occasional mass disappearances , giving them enigmatic names like disappearing disease , spring dwindle disease and autumn collapse .
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since when have humans domesticated bees ?
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♪♪ when he was nine years old , ron , without my parents or myself knowing his whereabouts , decided to take a mile walk from our home down to the library , which was , of course , a public library , but not so public for black folks when you 're talking about 1959 . so as he was walking in there , all these folks were staring at him because it was white folk only and they were looking at him saying , you know , `` who is this negro ? '' so he politely positioned himself in line to check out his books . well , this old librarian , she says , `` this library 's not for coloreds . '' he said , `` well , i would like to check out these books . '' she says , `` young man , if you do n't leave this library right now , i 'm gon na call the police . '' so he just propped himself up on the counter ... ( laughs ) and sat there and said , `` i 'll wait . '' so , she called the police and subsequently called my mother . the police came down , two burly guys , come in and say , `` well , where 's the disturbance ? '' she pointed to the little nine year old boy sitting up on the counter . he says , `` ma'am , what 's the problem ? '' so my mother , in the meanwhile , she was called and she comes down there praying the whole way there , `` lordy , jesus , please do n't let them put my child in jail . '' and my mother asked the librarian , `` what 's the problem ? '' `` he wanted to check out the book . you know your son should n't be down here . '' and the police officer said , `` why do n't you just give the kid the books ? '' and my mother said , `` he 'll take good care of them . '' and reluctantly , the librarian gave ron the books . and my mother said , `` what do you say ? '' he said , `` thank you , ma'am . '' ( laughs ) later on , as youngsters , a show came on tv called , `` star trek . '' now , star trek showed the future where there were black folk and white folk working together , and i just looked at it as science-fiction , because that was n't gon na happen , really . but ronald saw it as science-possibility , you know . he came up during a time when there was neil armstrong and all of those guys . so how was a colored boy from south carolina , wearing glasses , who never flew a plane , how was he gon na become an astronaut ? but ron was the one who did n't accept societal norms as being his norm . that was for other people . and uh , he got to be aboard his own starship enterprise . ♪♪ closed captions by captionlink www.captionlink.com
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now , star trek showed the future where there were black folk and white folk working together , and i just looked at it as science-fiction , because that was n't gon na happen , really . but ronald saw it as science-possibility , you know . he came up during a time when there was neil armstrong and all of those guys .
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what character traits do you think ronald possessed that helped him achieve success in the face of the challenges he was up against ?
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why is it so difficult to cure cancer ? we 've harnessed electricity , sequenced the human genome , and eradicated small pox . but after billions of dollars in research , we have n't found a solution for a disease that affects more than 14 million people and their families at any given time . cancer arises as normal cells accumulate mutations . most of the time , cells can detect mutations or dna damage and either fix them or self destruct . however , some mutations allow cancerous cells to grow unchecked and invade nearby tissues , or even metastasize to distant organs . cancers become almost incurable once they metastasize . and cancer is incredibly complex . it 's not just one disease . there are more than 100 different types and we do n't have a magic bullet that can cure all of them . for most cancers , treatments usually include a combination of surgery to remove tumors and radiation and chemotherapy to kill any cancerous cells left behind . hormone therapies , immunotherapy , and targeted treatments tailored for a specific type of cancer are sometimes used , too . in many cases , these treatments are effective and the patient becomes cancer-free . but they 're very far from 100 % effective 100 % of the time . so what would we have to do to find cures for all the different forms of cancer ? we 're beginning to understand a few of the problems scientists would have to solve . first of all , we need new , better ways of studying cancer . most cancer treatments are developed using cell lines grown in labs from cultures of human tumors . these cultured cells have given us critical insights about cancer genetics and biology , but they lack much of the complexity of a tumor in an actual living organism . it 's frequently the case that new drugs , which work on these lab-grown cells , will fail in clinical trials with real patients . one of the complexities of aggressive tumors is that they can have multiple populations of slightly different cancerous cells . over time , distinct genetic mutations accumulate in cells in different parts of the tumor , giving rise to unique subclones . for example , aggressive brain tumors called glioblastomas can have as many as six different subclones in a single patient . this is called clonal heterogeneity , and it makes treatment difficult because a drug that works on one subclone may have no effect on another . here 's another challenge . a tumor is a dynamic interconnected ecosystem where cancer cells constantly communicate with each other and with healthy cells nearby . they can induce normal cells to form blood vessels that feed the tumor and remove waste products . they can also interact with the immune system to actually suppress its function , keeping it from recognizing or destroying the cancer . if we could learn how to shut down these lines of communication , we 'd have a better shot at vanquishing a tumor permanently . additionally , mounting evidence suggests we 'll need to figure out how to eradicate cancer stem cells . these are rare but seem to have special properties that make them resistant to chemotherapy and radiation . in theory , even if the rest of the tumor shrinks beyond detection during treatment , a single residual cancer stem cell could seed the growth of a new tumor . figuring out how to target these stubborn cells might help prevent cancers from coming back . even if we solved those problems , we might face new ones . cancer cells are masters of adaptation , adjusting their molecular and cellular characteristics to survive under stress . when they 're bombarded by radiation or chemotherapy , some cancer cells can effectively switch on protective shields against whatever 's attacking them by changing their gene expression . malignant cancers are complex systems that constantly evolve and adapt . to defeat them , we need to find experimental systems that match their complexity , and monitoring and treatment options that can adjust as the cancer changes . but the good news is we 're making progress . even with all we do n't know , the average mortality rate for most kinds of cancer has dropped significantly since the 1970s and is still falling . we 're learning more every day , and each new piece of information gives us one more tool to add to our arsenal .
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why is it so difficult to cure cancer ? we 've harnessed electricity , sequenced the human genome , and eradicated small pox .
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which of the following is a true statement ?
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think back to a really vivid memory . got it ? okay , now try to remember what you had for lunch three weeks ago . that second memory probably is n't as strong , but why not ? why do we remember some things , and not others ? and why do memories eventually fade ? let 's look at how memories form in the first place . when you experience something , like dialing a phone number , the experience is converted into a pulse of electrical energy that zips along a network of neurons . information first lands in short term memory , where it 's available from anywhere from a few seconds to a couple of minutes . it 's then transferred to long-term memory through areas such as the hippocampus , and finally to several storage regions across the brain . neurons throughout the brain communicate at dedicated sites called synapses using specialized neurotransmitters . if two neurons communicate repeatedly , a remarkable thing happens : the efficiency of communication between them increases . this process , called long term potentiation , is considered to be a mechanism by which memories are stored long-term , but how do some memories get lost ? age is one factor . as we get older , synapses begin to falter and weaken , affecting how easily we can retrieve memories . scientists have several theories about what 's behind this deterioration , from actual brain shrinkage , the hippocampus loses 5 % of its neurons every decade for a total loss of 20 % by the time you 're 80 years old to the drop in the production of neurotransmitters , like acetylcholine , which is vital to learning and memory . these changes seem to affect how people retrieve stored information . age also affects our memory-making abilities . memories are encoded most strongly when we 're paying attention , when we 're deeply engaged , and when information is meaningful to us . mental and physical health problems , which tend to increase as we age , interfere with our ability to pay attention , and thus act as memory thieves . another leading cause of memory problems is chronic stress . when we 're constantly overloaded with work and personal responsibilites , our bodies are on hyperalert . this response has evolved from the physiological mechanism designed to make sure we can survive in a crisis . stress chemicals help mobilize energy and increase alertness . however , with chronic stress our bodies become flooded with these chemicals , resulting in a loss of brain cells and an inability to form new ones , which affects our ability to retain new information . depression is another culprit . people who are depressed are 40 % more likely to develop memory problems . low levels of serotonin , a neurotransmitter connected to arousal , may make depressed individuals less attentive to new information . dwelling on sad events in the past , another symptom of depression , makes it difficult to pay attention to the present , affecting the ability to store short-term memories . isolation , which is tied to depression , is another memory thief . a study by the harvard school of public health found that older people with high levels of social integration had a slower rate of memory decline over a six-year period . the exact reason remains unclear , but experts suspect that social interaction gives our brain a mental workout . just like muscle strength , we have to use our brain or risk losing it . but do n't despair . there are several steps you can take to aid your brain in preserving your memories . make sure you keep physically active . increased blood flow to the brain is helpful . and eat well . your brain needs all the right nutrients to keep functioning correctly . and finally , give your brain a workout . exposing your brain to challenges , like learning a new language , is one of the best defenses for keeping your memories intact .
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if two neurons communicate repeatedly , a remarkable thing happens : the efficiency of communication between them increases . this process , called long term potentiation , is considered to be a mechanism by which memories are stored long-term , but how do some memories get lost ? age is one factor .
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long term potentiation is a mechanism by which :
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translator : andrea mcdonough reviewer : bedirhan cinar we all start life as one single cell . then that cell divides and we are two cells , then four , then eight . cells form tissues , tissues form organs , organs form us . these cell divisions , by which we go from a single cell to 100 trillion cells , are called growth . and growth seems like a simple thing because when we think of it , we typically think of someone getting taller or , later in life , wider , but to cells , growth is n't simple . cell division is an intricate chemical dance that 's part individual , part community-driven . and in a neighborhood of 100 trillion cells , some times things go wrong . maybe an individual cell 's set of instructions , or dna , gets a typo , what we call a mutation . most of the time , the cell senses mistakes and shuts itself down , or the system detects a troublemaker and eliminates it . but , enough mutations can bypass the fail-safes , driving the cell to divide recklessly . that one rogue cell becomes two , then four , then eight . at every stage , the incorrect instructions are passed along to the cells ' offspring . weeks , months , or years after that one rogue cell transformed , you might see your doctor about a lump in your breast . difficulty going to the bathroom could reveal a problem in your intestine , prostate , or bladder . or , a routine blood test might count too many white cells or elevated liver enzymes . your doctor delivers the bad news : it 's cancer . from here your strategy will depend on where the cancer is and how far it 's progressed . if the tumor is slow-growing and in one place , surgery might be all you need , if anything . if the tumor is fast-growing or invading nearby tissue , your doctor might recommend radiation or surgery followed by radiation . if the cancer has spread , or if it 's inherently everywhere like a leukemia , your doctor will most likely recommend chemotherapy or a combination of radiation and chemo . radiation and most forms of chemo work by physically shredding the cells ' dna or disrupting the copying machinery . but neither radiation nor chemotherapeutic drugs target only cancer cells . radiation hits whatever you point it at , and your blood stream carries chemo-therapeutics all over your body . so , what happens when different cells get hit ? let 's look at a healthy liver cell , a healthy hair cell , and a cancerous cell . the healthy liver cell divides only when it is stressed ; the healthy hair cell divides frequently ; and the cancer cell divides even more frequently and recklessly . when you take a chemotherapeutic drug , it will hit all of these cells . and remember that the drugs work typically by disrupting cell division . so , every time a cell divides , it opens itself up to attack , and that means the more frequently a cell divides , the more likely the drug is to kill it . so , remember that hair cell ? it divides frequently and is n't a threat . and , there are other frequently dividing cells in your body like skin cells , gut cells , and blood cells . so the list of unpleasant side effects of cancer treatment parallels these tissue types : hair loss , skin rashes , nausea , vomiting , fatigue , weight loss , and pain . that makes sense because these are the cells that get hit the hardest . so , in the end , it is all about growth . cancer hijacks cells ' natural division machinery and forces them to put the pedal to the metal , growing rapidly and recklessly . but , using chemotherapeutic drugs , we take advantage of that aggressiveness , and we turn cancer 's main strength into a weakness .
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it divides frequently and is n't a threat . and , there are other frequently dividing cells in your body like skin cells , gut cells , and blood cells . so the list of unpleasant side effects of cancer treatment parallels these tissue types : hair loss , skin rashes , nausea , vomiting , fatigue , weight loss , and pain .
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about how many cells are in the human body ?
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translator : andrea mcdonough reviewer : bedirhan cinar ever wonder where most of the food you eat every day comes from ? well , about 60 % of the food you eat is carbohydrates . as you can probably tell from its name , carbohydrates contain carbon , hydrogen , and oxygen . but where do these atoms originally come from and how do they join together to make delicious foods like fruits and pasta ? it actually all starts with the air you are exhaling this very minute , specifically the carbon dioxide molecules . plants are going to breath in this very same carbon dioxide through pores in their skin , called stomata . plants drink in water from their roots to get the needed oxygen and hydrogen atoms , and their electrons , in order to build carbohydrates . what is that thing ? well , that 's a special plant organelle inside the leaves of plants called a chloroplast . it 's green beceause of a special light-absorbing pigment called chlorophyll . each leaf has about 44,000 cells and every cell can have anywhere between 20 to 100 chloroplasts . that 's up to 4,400,000 chloroplasts ! by now , you 've probably guessed that we 're talking about the process of photosynthesis and you might be wondering when the sun is going to make its entrance . let 's go back to that original molecule of water . the plant has to split this molecule of water so it can get electrons from it . but , the plant ca n't pull that water apart by itself . it needs help from the high-energy rays of the sun . so now that the chloroplast has all the building blocks - carbon , hydrogen , oxygen , and electrons - it can use them to go through the rest of the steps of photosynthesis to transform that original carbon dioxide gas into a simple carbohydrate called glucose , c-6-h-12-o-6 . that little glucose molecule then helps to build bigger and better carbohydrates like cellulose . cellulose is a type of carbohydrate found in plants that our body can not break down . we call it fiber and we eat it in vegetables like lettuce , broccoli , and celery . plants use cellulose to keep themselves strong . the plant could also turn that glucose into starch , a large molecule that stores energy for the plant . we love eating starch from plants like potatoes , corn , and rice . so you see , when you eat plants , we 're actually benefiting from photosynthesis . the plant makes things like starch , which we eat and then break back down into glucose , the first form the plant made . then , the mitochondria in our cells , powered by the oxygen we breath , can turn glucose into pure energy molecules called atp . atp powers all work done by each and every one of your cells , things like communication , movement , and transport . but why do we have to turn that glucose into atp ? well , think of it like this . you 're excited to start your summer job at the local ice cream stand , but your boss has just told you that she is going to pay you in ice cream cones . what are you going to be able to do with those ice cream cones ? nothing , which is why you kindly asked to be paid in dollars . atp is just like dollars . it is the currency that all cells of life use while glucose is , well , kind of like ice cream . even plants have mitochondria in their cells to break down the glucose they make into atp . so as you can see , humans and plants are intricately connected . the air we breath out is used by plants to make the carbohydrates we enjoy so much . and , in the process , they are releasing the very same oxygen molecules we need to breath in in order that our mitochondria can break down our delicous carbohydrate meal .
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translator : andrea mcdonough reviewer : bedirhan cinar ever wonder where most of the food you eat every day comes from ? well , about 60 % of the food you eat is carbohydrates . as you can probably tell from its name , carbohydrates contain carbon , hydrogen , and oxygen .
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which organelle is ultimately responsible for breaking down carbohydrates into usable energy at the molecular level ?
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translator : andrea mcdonough reviewer : bedirhan cinar tap dance : one of america 's major contributions to the world of percussive dance , born out of the melding of african and european dance traditions . there 's so many variations within tap dance , as many approaches as there have been tap dancers . and there have been a lot ! since its birth , over 125 years ago , tap dance has grown up in the world of american popular entertainment . from minstral shows and vaudeville , to night clubs , musical theater , and movie musicals , tap dance has held a featured role . and your approach depends on when in the history 's lineage you decide to connect . the landscape of american entertainment shifted in the 1950s and 60s . big bands became cost-prohibitive , rock and roll was becoming a popular music , and american musical theater moved towards a format incorporating ballet with narrative rather than the extension of variety shows that it had been in the past . all these factors pushed tap dancing to the fringes of the entertainment world . tap dance still existed ; there were dancers , but it was outside of the popular discourse . there were fewer and fewer places to dance and very little need for new tap dancers , so those who have been dancing in the 20s , 30s , and 40s , really had no one to pass along the art form to . in the 1970s , a multifaceted resurgence began . modern dancers became interested in the older tap dancers , drawing them out of retirement to teach . grassroots-organized tap festivals began to spring up , featuring the older tap dancers teaching the technique and the history of the craft . older dancers also came out of retirement to perform with groups such as the copasetics and the original hoofers , traveling the world . even broadway regained interest in the form , with gregory hines becoming a public figure for tap dance on the stage and in feature films . since then , the resurgence has spawned a more popular interest , with savion glover at the nexus of the crowd . considered the quintessential tap dancer , glover presents the form as a pure musician . since the 1990s , and thanks in a large part to the work of savion glover , we 've seen a rise in young people 's interest in tap dance . i 'm part of that generation . today , as we begin to rediscover the craft , we continue to look back and take examples of what tap dance was from past generations , at the same time , discovering our own unique approaches . there is so much freedom today . we can take what exists and apply past examples within our own unique context - today 's perspective on tap dance . it all really boils down to two pieces of metal on a leather-soled shoe , the wood to dance on , an audience to watch and listen , and something to say . it 's the balancing of these elements that is a tap dancer 's craft work .
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translator : andrea mcdonough reviewer : bedirhan cinar tap dance : one of america 's major contributions to the world of percussive dance , born out of the melding of african and european dance traditions . there 's so many variations within tap dance , as many approaches as there have been tap dancers . and there have been a lot !
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there is only one style of tap dance .
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so , you 're thinking of moving to mars . have you picked out a spot for your new home ? no ? well , i 'm here to help . first things first , here are some of the things you 'll need to bring to the red planet : a high tolerance for cold , loneliness , and radiation ; a lifetime supply of breathable air and food ; a multibillion dollar spaceship ; a desire to just get away from it all ; and water . you 're definitely going to need water . so what sort of real estate are you looking for ? how about a mansion in the maze-like noctis labyrinthus ? a hideaway in the happy face crater ? a fortress on the face mesa ? an oceanview ? uh , bad news on the last one . you 're about 4 billion years late . we 're pretty sure that mars used to have oceans , lakes , rivers , the whole package . but over time , almost all of it froze beneath the surface , or evaporated off into space . there 's probably still some trapped beneath the seasonally expanding and contracting carbon dioxide ice caps , though . so what might mars look like today if it had surface water ? that , of course , depends on how much we 're talking about , but maybe something like this . the relatively flat northern hemisphere is below the average elevation , so it would become one giant ocean , while the crater-ridden southern hemisphere would stay mostly high and dry . that difference between hemispheres is a bit bizarre , and we do n't know why it 's like that . the southern half is probably much older , judging by features like the number of craters , and the evidence of increased volcanic activity in the north . okay , so who knows ? maybe one day mars will have oceans again , but for now , what we 've got is essentially one giant dusty desert . in fact , it 's similar enough to deserts on earth , that we 've been able to learn a great deal about mars on our home planet . for instance , martian sand dunes form and behave similarly to our sand dunes , though the martian versions often grow twice as large thanks to a gravitational pull that 's about a third as strong as ours . and mars has some features you wo n't see on earth , like tars , which are crestless sand dunes up to fifteen meters tall , whose formations we have yet to understand . you 're probably wondering , `` what do you get when you combine a planet-wide desert with an atmosphere that , like ours , is subject to wind-generating pressure differentials , dust storms ? '' these will be your main weather hazards on the red planet . they play a large part in making the planet red by distributing rusted iron particles across the surface and into the air . thanks to the low gravity and lack of moisture , these dust storms can last for months and cover the planet . so , you might want to build your home as high as possible . well , look no further . this is olympus mons , the largest volcano in the solar system . even if mars had a breathable atmosphere , you 'd find the views from the 25 kilometer summit breathtaking . or are volcanos not your thing ? then how about valles marineris , the largest canyon in the solar system ? it 's so wide that from one side , the opposite rim would be below the curve of the horizon . still , you 'll catch some spectacular blue sunsets in the normally red sky , which gets its color from the dust absorbing most of the blue light , and the way sunlight is scattered by the atmosphere . have you got spirit , curiosity , or are you just looking for opportunity ? then stop stalling and make the move to mars today . mars : redder than ever .
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then stop stalling and make the move to mars today . mars : redder than ever .
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what is the major natural hazard on mars ?
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every spring , hundreds of adventure-seekers dream of climbing qomolangma , also known as mount everest . at base camp , they hunker down for months waiting for the chance to scale the mountain 's lofty , lethal peak . but why do people risk life and limb to climb everest ? is it the challenge ? the view ? the chance to touch the sky ? for many , the draw is everest 's status as the highest mountain on earth . there 's an important distinction to make here . mauna kea is actually the tallest from base to summit , but at 8850 meters above sea level , everest has the highest altitude on the planet . to understand how this towering formation was born , we have to peer deep into our planet 's crust , where continental plates collide . the earth 's surface is like an armadillo 's armor . pieces of crust constantly move over , under , and around each other . for such huge continental plates , the motion is relatively quick . they move two to four centimeters per year , about as fast as fingernails grow . when two plates collide , one pushes into or underneath the other , buckling at the margins , and causing what 's known as uplift to accomodate the extra crust . that 's how everest came about . 50 million years ago , the earth 's indian plate drifted north , bumped into the bigger eurasian plate , and the crust crumpled , creating huge uplift . mountain everest lies at the heart of this action , on the edge of the indian-eurasian collision zone . but mountains are shaped by forces other than uplift . as the land is pushed up , air masses are forced to rise as well . rising air cools , causing any water vapor within it to condense and form rain or snow . as that falls , it wears down the landscape , dissolving rocks or breaking them down in a process known as weathering . water moving downhill carries the weathered material and erodes the landscape , carving out deep valleys and jagged peaks . this balance between uplift and erosion gives a mountain its shape . but compare the celestial peaks of the himalayas to the comforting hills of appalachia . clearly , all mountains are not alike . that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast . the peaks grow tall with steep slopes . over time , however , gravity and water wear them down . eventually , erosion overtakes uplift , wearing down peaks faster than they 're pushed up . a third factor shapes mountains : climate . in subzero temperatures , some snowfall does n't completely melt away , instead slowly compacting until it becomes ice . that forms the snowline , which occurs at different heights around the planet depending on climate . at the freezing poles , the snowline is at sea level . near the equator , you have to climb five kilometers before it gets cold enough for ice to form . gathered ice starts flowing under its own immense weight forming a slow-moving frozen river known as a glacier , which grinds the rocks below . the steeper the mountains , the faster ice flows , and the quicker it carves the underlying rock . glaciers can erode landscapes swifter than rain and rivers . where glaciers cling to mountain peaks , they sand them down so fast , they lop the tops off like giant snowy buzzsaws . so then , how did the icy mount everest come to be so tall ? the cataclysmic continental clash from which it arose made it huge to begin with . secondly , the mountain lies near the tropics , so the snowline is high , and the glaciers relatively small , barely big enough to widdle it down . the mountain exists in a perfect storm of conditions that maintain its impressive stature . but that wo n't always be the case . we live in a changing world where the continental plates , earth 's climate , and the planet 's erosive power might one day conspire to cut mount everest down to size . for now , at least , it remains legendary in the minds of hikers , adventurers , and dreamers alike .
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water moving downhill carries the weathered material and erodes the landscape , carving out deep valleys and jagged peaks . this balance between uplift and erosion gives a mountain its shape . but compare the celestial peaks of the himalayas to the comforting hills of appalachia .
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what is the relationship between mountain slope ( or steepness ) and glacial flow ?
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take a look at the water in this glass . refreshing , hydrating , and invaluable to your survival . before you take a sip , though , how do you know that the water inside is free from disease-causing organisms and pollutants ? one out of ten people in the world ca n't actually be sure that their water is clean and safe to drink . why is that ? inadequate sanitation , poor protection of drinking water sources , and improper hygiene often lead to sewage and feces-contaminated water . that 's the ideal breeding ground for dangerous bacteria , viruses , and parasites . and the effects of these pathogens are staggering . diarrheal disease from unsafe water is one of the leading causes of death around the world for children under five . and according to a u.n. report from 2010 , microbial water-borne illnesses killed more people per year than war . proper treatment processes , though , can address these threats . they usually have three parts : sedimentation , filtration , and disinfection . once water has been collected in a treatment facility , it 's ready for cleaning . the first step , sedimentation , just takes time . the water sits undisturbed , allowing heavier particles to sink to the bottom . often , though , particles are just too small to be removed by sedimentation alone and need to be filtered . gravity pulls the water downward through layers of sand that catch leftover particles in their pores , prepping the water for its final treatment , a dose of disinfectant . chemicals , primarily forms of chlorine and ozone , are mixed in to kill off any pathogens and to disinfect pipes and storage systems . chlorine is highly effective in destroying water 's living organisms , but its use remains government-regulated because it has potentially harmful chemical byproducts . and if an imbalance of chlorine occurs during the disinfection process , it can trigger other chemical reactions . for example , levels of chlorine byproducts , like trihalomethanes , could skyrocket , leading to pipe corrosion and the release of iron , copper , and lead into drinking water . water contamination from these and other sources including leaching , chemical spills , and runoffs , has been linked to long-term health effects , like cancer , cardiovascular and neurological diseases , and miscarriage . unfortunately , analyzing the exact risks of chemically contaminated water is difficult . so while it 's clear that disinfectants make us safer by removing disease-causing pathogens , experts have yet to determine the full scope of how the chemical cocktail in our drinking water really impacts human health . so how can you tell whether the water you have access to , whether from a tap or otherwise , is drinkable ? firstly , too much turbidity , trace organic compounds , or high-density heavy metals like arsenic , chromium , or lead , mean that the water is unsuitable for consumption . a lot of contaminants , like lead or arsenic , wo n't be obvious without tests , but some clues , like cloudiness , brown or yellow coloration , a foul odor , or an excessive chlorine smell can indicate the need to investigate further . water testing kits can go a step further and confirm the presence of many different contaminants and chemicals . with many types of contamination , there are ways of treating water where it 's used instead of close to its source . point-of-use treatment has actually been around for thousands of years . ancient egyptians boiled away many organic contaminants with the sun 's heat . and in ancient greece , hippocrates designed a bag that trapped bad tasting sediments from water . today , point-of-use processes usually involve ionization to lower mineral content . they also use adsorption filtration , where a porous material called activated carbon strains the water to remove contaminants and chemical byproducts . while it 's not always an effective long-term solution , point-of-use treatment is portable , easy to install , and adaptable . and in regions where large-scale systems are unavailable , or where water has been contaminated further along its journey , these systems can mean the difference between life and death . clean water remains a precious and often scarce commodity . there are nearly 800 million of us who still do n't have regular access to it . the good news is that continued developments in water treatment , both on a large and small scale , can alleviate a lot of unsafe conditions . implementing proper systems where they 're needed and paying careful attention to the ones already in place will fulfill one of the most basic of our human needs .
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a lot of contaminants , like lead or arsenic , wo n't be obvious without tests , but some clues , like cloudiness , brown or yellow coloration , a foul odor , or an excessive chlorine smell can indicate the need to investigate further . water testing kits can go a step further and confirm the presence of many different contaminants and chemicals . with many types of contamination , there are ways of treating water where it 's used instead of close to its source .
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today , your water seems a bit different than normal . what might be some indicators that there is an issue ?
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living with her family high above the ground in the northern tropical forests of colombia , you will find shakira , a cotton-top tamarin with a penchant for conversation . say , `` hola ! '' though you may not realize it , this one pound monkey communicates in a highly sophisticated language of 38 distinct calls based on variations of chirps and whistles . the response she just gave is known as a `` b chirp '' , a call often directed at humans . to appreciate the complexities of shakira 's language , let 's learn a few chirps and whistles , then examine how their combinations form grammatically structured sequences . the chirp shakira used to greet us comes from a class of calls known as single frequency modulated syllables . this class is made up of short duration calls , or chirps , and long duration calls , like screams and squeals . researchers have determined that there are eight different types of chirps categorized by stem upsweep , duration , peak frequency , and frequency change . in addition , each chirp has its own unique meaning . for example , shakira 's `` c chirp '' is used when she is approaching food , where as her `` d chirp '' is only used when she has the food in hand . single whistles also exhibit a unique intention with each call and just as there are eight different chirps , there are five different whistles . based on frequency modulation , single whistles are subdivided into four categories : squeaks , initially modulated whistles , terminally modulated whistles , and flat whistles . the language 's quality of unique intention is wonderfully exemplified by the category of initially modulated whistles . these whistles change based on the proximity of shakira to other members of her family . if shakira is greater than .6 meters from her family , she 'll sound a large initally modulated whistle . but if she 's less than .6 meters from her family , she 'll sound a small initially modulated whistle . now that we 've learned a few chirps and whistles , shakira wants to show off by taking you through a quick day in her life with these calls . while heading towards a feeding tree for her first meal of the day , she says , ( monkey noise ) , a call most often used in relaxed investigations . however , suddenly she spots the shadow of a hawk . `` e chirp '' for alarm . this call alerts her family to the presence of this predator , and shakira jumps to the safety of an inner branch . the coast seems clear , so shakira makes her way towards her dad . wait , wait . who is that ? ah , it 's her younger brother , carlos . cotton-top tamarins often squeal during play wrestling . uh-oh . he 's playing a little too roughly , and shakira screams , alerting her parents to help her . her dad makes his way towards the ball of rolling fur and her brother stops . shakira shakes herself and scratches herself to get the hair on her head back in place . then shakira spots another group of unfamiliar tamarins and hears their normal long call . she turns to her family . ( monkey noise ) did you catch that ? first there was a chirp , then a whistle . this is what 's known as a combination vocalization , a phrase that contains both a chirp and a whistle . these are two calls strung together to convey a message . the combination of these two elements alerts her family to the presence of another group , the `` f chirp '' , and the distance they are away , the normal long call whistle . in other words , shakira just said a sentence . her simple demonstration is just the tip of the iceberg . she 's got trills , chatters , multiple whistle calls , more combination vocalizations , even twitters . yet sadly enough , we may not get to hear everything she has to say . mixed in with chirping sonatas from high above is the constant thud of a machete chopping trees . shakira 's habitat in colombia is being cut down , piece by piece , and if we do n't work to protect the critically endangered cotton-top tamarin , it will become extinct in our lifetime . if the chirp from one tamarin to the next has proven to be more than just idle chit chat , imagine what else we have left to discover . imagine what else shakira can tell us .
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ah , it 's her younger brother , carlos . cotton-top tamarins often squeal during play wrestling . uh-oh .
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cotton-top tamarins are critically endangered . how can you help insure their survival ?
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in 1997 , a french woman named jeanne calment passed away after 122 years and 164 days on this earth , making her the oldest known person in history . her age was so astounding that a millionaire pledged $ 1 million to anyone who could break her record . but in reality , living to this age or beyond is a feat that very few , maybe even no humans , are likely to accomplish . human bodies just are n't built for extreme aging . our capacity is set at about 90 years . but what does aging really mean and how does it counteract the body 's efforts to stay alive ? we know intuitively what it means to age . for some , it means growing up , while for others , it 's growing old . yet finding a strict scientific definition of aging is a challenge . what we can say is that aging occurs when intrinsic processes and interactions with the environment , like sunlight , and toxins in the air , water , and our diets , cause changes in the structure and function of the body 's molecules and cells . those changes in turn drive their decline , and subsequently , the failure of the whole organism . the exact mechanisms of aging are poorly understood . but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role . firstly , as the years pass , our bodies accumulate genetic damage in the form of dna lesions . these occur naturally when the body 's dna replicates , but also in non-dividing cells . organelles called mitochondria are especially prone to this damage . mitochondria produce adenosine triphosphate , or atp , the main energy source for all cellular processes , plus mitochondria regulate many different cell activities and play an important role in programmed cell death . if mitochondrial function declines , then cells and , later on , whole organs , deteriorate , too . other changes are known to occur in the expression patterns of genes , also known as epigenetic alterations , that affect the body 's tissues and cells . genes silenced or expressed only at low levels in newborns become prominent in older people , leading to the development of degenerative diseases , like alzheimer 's , which accelerate aging . even if we could avoid all these harmful genetic alterations , not even our own cells could save us . the fact remains that cellular regeneration , the very stuff of life , declines as we age . the dna in our cells is packaged within chromosomes , each of which has two protective regions at the extremities called telomeres . those shorten every time cells replicate . when telomeres become too short , cells stop replicating and die , slowing the body 's ability to renew itself . with age , cells increasingly grow senescent , too , a process that halts the cell cycle in times of risk , like when cancer cells are proliferating . but the response also kicks in more as we age , halting cell growth and cutting short their ability to replicate . aging also involves stem cells that reside in many tissues and have the property of dividing without limits to replenish other cells . as we get older , stem cells decrease in number and tend to lose their regenerative potential , affecting tissue renewal and maintenance of our organs original functions . other changes revolve around cells ' ability to function properly . as they age , they stop being able to do quality control on proteins , causing the accumulation of damaged and potentially toxic nutrients , leading to excessive metabolic activity that could be fatal for them . intercellular communication also slows , ultimately undermining the body 's functional ability . there 's a lot we do n't yet understand about aging . ultimately , does longer life as we know it come down to diet , exercise , medicine , or something else ? will future technologies , like cell-repairing nanobots , or gene therapy , artificially extend our years ? and do we want to live longer than we already do ? starting with 122 years as inspiration , there 's no telling where our curiosity might take us .
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those changes in turn drive their decline , and subsequently , the failure of the whole organism . the exact mechanisms of aging are poorly understood . but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role .
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aging can be defined as :
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there 's a common misconception that if you like to meticulously organize your things , keep your hands clean , or plan out your weekend to the last detail , you might have ocd . in fact , ocd , which stands for obsessive compulsive disorder , is a serious psychiatric condition that is frequently misunderstood by society and mental health professionals alike . so let 's start by debunking some myths . myth one : repetitive or ritualistic behaviors are synonymous with ocd . as its name suggests , obsessive compulsive disorder has two aspects : the intrusive thoughts , images , or impulses , known as obsessions , and the behavioral compulsions people engage in to relieve the anxiety the obsessions cause . the kinds of actions that people often associate with ocd , like excessive hand washing , or checking things repeatedly , may be examples of obsessive or compulsive tendencies that many of us exhibit from time to time . but the actual disorder is far more rare and can be quite debilitating . people affected have little or no control over their obsessive thoughts and compulsive behaviors , which tend to be time consuming and interfere with work , school or social life to the point of causing significant distress . this set of diagnostic criteria is what separates people suffering from ocd from those who may just be a bit more meticulous or hygiene obsessed than usual . myth two : the main symptom of ocd is excessive hand washing . although hand washing is the most common image of ocd in popular culture , obsessions and compulsions can take many different forms . obsessions can manifest as fears of contamination and illness , worries about harming others , or preoccupations with numbers , patterns , morality , or sexual identity . and compulsions can range from excessive cleaning or double checking , to the fastidious arrangement of objects , or walking in predetermined patterns . myth three : individuals with ocd do n't understand that they are acting irrationally . many individuals with ocd actually understand the relationship between their obsessions and compulsions quite well . being unable to avoid these thoughts and actions despite being aware of their irrationality is part of the reason why ocd is so distressing . ocd sufferers report feeling crazy for experiencing anxiety based on irrational thoughts and finding it difficult to control their responses . so what exactly causes ocd ? the frustrating answer is we do n't really know . however , we have some important clues . ocd is considered a neurobiological disorder . in other words , research suggests that ocd sufferers brains are actually hardwired to behave in a certain fashion . research has implicated three regions of the brain variously involved in social behavior and complex cognitive planning , voluntary movement , and emotional and motivational responses . the other piece of the puzzle is that ocd is associated with low levels of serotonin , a neurotransmitter that communicates between brain structures and helps regulate vital processes , such as mood , aggression , impulse control , sleep , appetite , body temperature and pain . but are serotonin and activity in these brain regions the sources of ocd or symptoms of an unknown underlying cause of the disorder . we probably wo n't know until we have a much more intimate understanding of the brain . the good news is there are effective treatments for ocd , including medications , which increase serotonin in the brain by limiting its reabsorption by brain cells , behavioral therapy that gradually desensitizes patients to their anxieties , and in some cases , electroconvulsive therapy , or surgery , when ocd does n't respond to other forms of treatment . knowing that your own brain is lying to you while not being able to resist its commands can be agonizing . but with knowledge and understanding comes the power to seek help , and future research into the brain may finally provide the answers we 're looking for .
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ocd sufferers report feeling crazy for experiencing anxiety based on irrational thoughts and finding it difficult to control their responses . so what exactly causes ocd ? the frustrating answer is we do n't really know .
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which of the following chemicals has been the most implicated in ocd ?
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the sight of mistletoe may either send you scurrying , or if you have your eye on someone , awaiting an opportunity beneath its snow white berries , but how did the festive christmas tradition of kissing under mistletoe come about ? the long-lived custom intertwines the mythology and biology of this intriguing plant . there are more than 1,000 species of mistletoe , which grows the world over . in fact , the ancient europeans were so captivated by the plant 's unusual growth habits that they included it in their legends and myths . in ancient rome , pliny the elder described how the druid priesthood in ancient england believed that mistletoe was a plant dropped down from heaven by the gods . that explained its unlikely position amongst the high branches of certain trees . they also believed it had powers of healing and bestowing fertility . meanwhile , scandinavian legend told of the plant 's mystical qualities in the story of the god baldr and his adoring mother frigg , goddess of love , marriage , and fertility . frigg loved her son so much that she commanded every plant , animal , and inanimate object to vow they 'd never harm him . in her fervor , however , she overlooked the mistletoe . the mischievous god loki realized this oversight and pierced baldr 's heart with an arrow carved from a mistletoe branch . frigg cried tears of such sadness that they formed the mistletoe 's pearly berries , making the other gods pity her and agree to resurrect baldr . hearing the news , frigg became so overjoyed that she transformed the mistletoe from a symbol of death into one of peace and love . she mandated a one-day truce for all fights , and that everyone embrace beneath its branches when they passed to spread more love into the world . in the 17th century , british colonists arriving in the new world found a different , but very similar looking , species of mistletoe . they applied it to these tales of magic , fertility , and love , spreading the mistletoe-hanging tradition from europe into america . by the 18th century , people in britain had turned this into a christmas tradition , but this custom comes down to more than just human imagination . all of it was inspired by the plant 's intriguing biology . we see mistletoe as a festive decoration , but draped on tree boughs in the wild , it 's known as a partly parasitic plant . mistletoe relies on modified roots called haustoria that penetrate the tree bark and siphon off the water and minerals trees carry up their trunks to colonize nearby trees with its seeds , mistletoe depends on birds and other creatures to do the dispersing . birds that eat the mistletoe 's sticky white berries sometimes get rid of the gluey seeds by wiping them off onto tree bark . or with a bit of luck , they excrete the indigestible seed onto a tree where it germinates and starts to grow . with its resilience and foliage that stays lush even while the surrounding trees lose their leaves , you can see why mistletoe captivated our superstitious ancestors . they saw these as signs of the plant 's magical qualities and fertility . even today , the mistletoe inspires wonder with the diversity of wildlife it supports . more than just a parasite , it 's also known as a keystone species . it 's eaten by a diversity of animals , including deer , elk , squirrels , chipmunks , porcupines , robins , bluebirds , morning doves , and the butterfly genus delias . some mistletoe species produce dense bushes , which are excellent nesting locations for a variety of birds . and despite their parasitic relationship with trees , mistletoes can also help other plants . for instance , juniper sprouts near mistletoe to benefit from the visiting berry-eating birds . through the many benefits it provides , mistletoe influences diversity , and allows ecosystems to flourish . you might even say that for this iconic plant , life imitates legend . in the wild , mistletoe has the power to bring things together , and in our own traditions , we see that happening , too .
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we see mistletoe as a festive decoration , but draped on tree boughs in the wild , it 's known as a partly parasitic plant . mistletoe relies on modified roots called haustoria that penetrate the tree bark and siphon off the water and minerals trees carry up their trunks to colonize nearby trees with its seeds , mistletoe depends on birds and other creatures to do the dispersing . birds that eat the mistletoe 's sticky white berries sometimes get rid of the gluey seeds by wiping them off onto tree bark .
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the mistletoe ’ s modified roots are called :
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around 1159 a.d. , a mathematician called bhaskara the learned sketched a design for a wheel containing curved reservoirs of mercury . he reasoned that as the wheels spun , the mercury would flow to the bottom of each reservoir , leaving one side of the wheel perpetually heavier than the other . the imbalance would keep the wheel turning forever . bhaskara 's drawing was one of the earliest designs for a perpetual motion machine , a device that can do work indefinitely without any external energy source . imagine a windmill that produced the breeze it needed to keep rotating . or a lightbulb whose glow provided its own electricity . these devices have captured many inventors ' imaginations because they could transform our relationship with energy . for example , if you could build a perpetual motion machine that included humans as part of its perfectly efficient system , it could sustain life indefinitely . there 's just one problem . they do n't work . ideas for perpetual motion machines all violate one or more fundamental laws of thermodynamics , the branch of physics that describes the relationship between different forms of energy . the first law of thermodynamics says that energy ca n't be created or destroyed . you ca n't get out more energy than you put in . that rules out a useful perpetual motion machine right away because a machine could only ever produce as much energy as it consumed . there would n't be any left over to power a car or charge a phone . but what if you just wanted the machine to keep itself moving ? inventors have proposed plenty of ideas . several of these have been variations on bhaskara 's over-balanced wheel with rolling balls or weights on swinging arms . none of them work . the moving parts that make one side of the wheel heavier also shift its center of mass downward below the axle . with a low center of mass , the wheel just swings back and forth like a pendulum , then stops . what about a different approach ? in the 17th century , robert boyle came up with an idea for a self-watering pot . he theorized that capillary action , the attraction between liquids and surfaces that pulls water through thin tubes , might keep the water cycling around the bowl . but if the capillary action is strong enough to overcome gravity and draw the water up , it would also prevent it from falling back into the bowl . then there are versions with magnets , like this set of ramps . the ball is supposed to be pulled upwards by the magnet at the top , fall back down through the hole , and repeat the cycle . this one fails because like the self-watering pot , the magnet would simply hold the ball at the top . even if it somehow did keep moving , the magnet 's strength would degrade over time and eventually stop working . for each of these machines to keep moving , they 'd have to create some extra energy to nudge the system past its stopping point , breaking the first law of thermodynamics . there are ones that seem to keep going , but in reality , they invariably turn out to be drawing energy from some external source . even if engineers could somehow design a machine that did n't violate the first law of thermodynamics , it still would n't work in the real world because of the second law . the second law of thermodynamics tells us that energy tends to spread out through processes like friction . any real machine would have moving parts or interactions with air or liquid molecules that would generate tiny amounts of friction and heat , even in a vacuum . that heat is energy escaping , and it would keep leeching out , reducing the energy available to move the system itself until the machine inevitably stopped . so far , these two laws of thermodynamics have stymied every idea for perpetual motion and the dreams of perfectly efficient energy generation they imply . yet it 's hard to conclusively say we 'll never discover a perpetual motion machine because there 's still so much we do n't understand about the universe . perhaps we 'll find new exotic forms of matter that 'll force us to revisit the laws of thermodynamics . or maybe there 's perpetual motion on tiny quantum scales . what we can be reasonably sure about is that we 'll never stop looking . for now , the one thing that seems truly perpetual is our search .
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you ca n't get out more energy than you put in . that rules out a useful perpetual motion machine right away because a machine could only ever produce as much energy as it consumed . there would n't be any left over to power a car or charge a phone .
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how might you prove a machine is a perpetual motion machine without running it until the end of time ?
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if someone asked you who the richest people in history were , who would you name ? perhaps a billionaire banker or corporate mogul , like bill gates or john d. rockefeller . how about african king musa keita i ? ruling the mali empire in the 14th century ce , mansa musa , or the king of kings , amassed a fortune that possibly made him one of the wealthiest people who ever lived . but his vast wealth was only one piece of his rich legacy . when mansa musa came to power in 1312 , much of europe was racked by famine and civil wars . but many african kingdoms and the islamic world were flourishing , and mansa musa played a great role in bringing the fruits of this flourishing to his own realm . by strategically annexing the city of timbuktu , and reestablishing power over the city of gao , he gained control over important trade routes between the mediterranean and the west african coast , continuing a period of expansion , which dramatically increased mali 's size . the territory of the mali empire was rich in natural resources , such as gold and salt . the world first witnessed the extent of mansa musa 's wealth in 1324 when he took his pilgrimage to mecca . not one to travel on a budget , he brought a caravan stretching as far as the eye could see . accounts of this journey are mostly based on an oral testimony and differing written records , so it 's difficult to determine the exact details . but what most agree on is the extravagant scale of the excursion . chroniclers describe an entourage of tens of thousands of soldiers , civilians , and slaves , 500 heralds bearing gold staffs and dressed in fine silks , and many camels and horses bearing an abundance of gold bars . stopping in cities such as cairo , mansa musa is said to have spent massive quantities of gold , giving to the poor , buying souvenirs , and even having mosques built along the way . in fact , his spending may have destabilized the regional economy , causing mass inflation . this journey reportedly took over a year , and by the time mansa musa returned , tales of his amazing wealth had spread to the ports of the mediterranean . mali and its king were elevated to near legendary status , cemented by their inclusion on the 1375 catalan atlas . one of the most important world maps of medieval europe , it depicted the king holding a scepter and a gleaming gold nugget . mansa musa had literally put his empire and himself on the map . but material riches were n't the king 's only concern . as a devout muslim , he took a particular interest in timbuktu , already a center of religion and learning prior to its annexation . upon returning from his pilgrimage , he had the great djinguereber mosque built there with the help of an andalusian architect . he also established a major university , further elevating the city 's reputation , and attracting scholars and students from all over the islamic world . under mansa musa , the empire became urbanized , with schools and mosques in hundreds of densely populated towns . the king 's rich legacy persisted for generations and to this day , there are mausoleums , libraries and mosques that stand as a testament to this golden age of mali 's history .
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perhaps a billionaire banker or corporate mogul , like bill gates or john d. rockefeller . how about african king musa keita i ? ruling the mali empire in the 14th century ce , mansa musa , or the king of kings , amassed a fortune that possibly made him one of the wealthiest people who ever lived . but his vast wealth was only one piece of his rich legacy . when mansa musa came to power in 1312 , much of europe was racked by famine and civil wars . but many african kingdoms and the islamic world were flourishing , and mansa musa played a great role in bringing the fruits of this flourishing to his own realm . by strategically annexing the city of timbuktu , and reestablishing power over the city of gao , he gained control over important trade routes between the mediterranean and the west african coast , continuing a period of expansion , which dramatically increased mali 's size .
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mansa musa is one of many african monarchs throughout the continent 's rich history . yet , the narratives of only a few kings and queens are featured in television and movies . analyze and evaluate why you think that this is the case , then create two ideas for how we can work to bring more positive awareness of the history of africa 's ancient and contemporary kings and queens to students today .
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in the late 17th century , a medical student named johannes hofer noticed a strange illness affecting swiss mercenaries serving abroad . its symptoms , including fatigue , insomnia , irregular heartbeat , indigestion , and fever were so strong , the soldiers often had to be discharged . as hofer discovered , the cause was not some physical disturbance , but an intense yearning for their mountain homeland . he dubbed the condition nostalgia , from the greek `` nostos '' for homecoming and `` algos '' for pain or longing . at first , nostalgia was considered a particularly swiss affliction . some doctors proposed that the constant sound of cowbells in the alps caused trauma to the ear drums and brain . commanders even forbade their soldiers from singing traditional swiss songs for fear that they 'd lead to desertion or suicide . but as migration increased worldwide , nostalgia was observed in various groups . it turned out that anyone separated from their native place for a long time was vulnerable to nostalgia . and by the early 20th century , professionals no longer viewed it as a neurological disease , but as a mental condition similar to depression . psychologists of the time speculated that it represented difficulties letting go of childhood , or even a longing to return to one 's fetal state . but over the next few decades , the understanding of nostalgia changed in two important ways . its meaning expanded from indicating homesickness to a general longing for the past . and rather than an awful disease , it began to be seen as a poignant and pleasant experience . perhaps the most famous example of this was captured by french author marcel proust . he described how tasting a madeleine cake he had not eaten since childhood triggered a cascade of warm and powerful sensory associations . so what caused such a major reversal in our view of nostalgia ? part of it has to do with science . psychology shifted away from pure theory and towards more careful and systematic empirical observation . so professionals realized that many of the negative symptoms may have been simply correlated with nostalgia rather than caused by it . and , in fact , despite being a complex emotional state that can include feelings of loss and sadness , nostalgia does n't generally put people in a negative mood . instead , by allowing individuals to remember personally meaningful and rewarding experiences they shared with others , nostalgia can boost psychological well-being . studies have shown that inducing nostalgia in people can help increase their feelings of self-esteem and social belonging , encourage psychological growth , and even make them act more charitably . so rather than being a cause of mental distress , nostalgia can be a restorative way of coping with it . for instance , when people experience negative emotional states , they tend to naturally use nostalgia to reduce distress and restore well-being . today , it seems that nostalgia is everywhere , partially because advertisers have discovered how powerful it is as a marketing technique . it 's tempting to think of this as a sign of us being stuck in the past , but that 's not really how nostalgia works . instead , nostalgia helps us remember that our lives can have meaning and value , helping us find the confidence and motivation to face the challenges of the future .
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so rather than being a cause of mental distress , nostalgia can be a restorative way of coping with it . for instance , when people experience negative emotional states , they tend to naturally use nostalgia to reduce distress and restore well-being . today , it seems that nostalgia is everywhere , partially because advertisers have discovered how powerful it is as a marketing technique .
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how might nostalgia serve to increase wellbeing when people experience distressing states such as loneliness ?
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on the night of january 1 , 1801 , giuseppe piazzi , a priest in palermo , italy , was mapping the stars in the sky . over three nights , he 'd look at and draw the same set of stars , carefully measuring their relative positions . that night , he measured the stars . the next night , he measured them again . to his surprise , one had moved . the third night , the peculiar star had moved again . this meant it could n't be a star at all . it was something new , the first asteroid ever discovered , which piazzi eventually named ceres . asteroids are bits of rock and metal that orbit the sun . at over 900 kilometers across , ceres is a very large asteroid . but through a telescope , like piazzi 's , ceres looked like a pinpoint of light similar to a star . in fact , the word asteroid means star-like . you can tell the difference between stars and asteroids by the way they move across the sky . of course , piazzi knew none of that at the time , just that he had discovered something new . to learn about ceres , piazzi needed to track its motion across the sky and then calculate its orbit around the sun . so each clear night , piazzi trained his telescope to the heavens . night after night , he made careful measurements until finally , he could n't . the sun got in the way . when piazzi first spotted ceres , it was here , and the earth was here . as he tracked it each night , the earth and ceres moved like this until ceres was here . and that meant that ceres was only in the sky when it was daytime on earth . during the day , bright sunlight made this small asteroid impossible to see . astronomers needed to calculate ceres 's orbit . this would let them predict where it was going to be in the vast night sky on any given night . but the calculations were grueling and the results imprecise . many astronomers searched for ceres , but not knowing exactly where to look , no one could find it . luckily , a hardworking mathematician named carl friedrich gauss heard about the lost asteroid . he thought it was an exciting puzzle and went to work . when he realized he did n't have the mathematical methods he needed , he invented new ones that we still use today . he derived a new orbit and new predictions of where to look for ceres . hungarian astronomer baron franz xaver von zach searched for ceres with gauss 's predictions . after weeks of frustrating clouds , von zach finally had clear skies on december 31 , 1801 . he looked through his telescope and finally saw ceres . we have n't lost track of it since . today , we 've discovered hundreds of thousands of asteroids . many , including ceres , orbit the sun between mars and jupiter , while near-earth asteroids orbit the sun relatively close to earth . when we recorded this narration , astronomers had discovered 16,407 near-earth asteroids , but since we find new asteroids all the time , that number will have grown by hundreds or thousands by the time you watch this . today , asteroid hunters use modern telescopes , including one in space . computers analyze the images , and humans check the output before reporting the asteroid observations to an archiving center . each discovered asteroid has its unique orbit measured . an orbit lets astronomers predict where asteroids are going to be at any given time . most asteroid trajectories can be predicted for about 80 years though we can calculate where the best studied asteroids will be every day between now and 800 years into the future . we must keep searching for asteroids in case there 's one out there on a collision course with earth . astronomers do n't only search for asteroids , though . they also study them to learn how they formed , what they 're made of , and what they can tell us about our solar system . today , we can do something that piazzi could only dream of : send spacecraft to study asteroids up close . one spacecraft called dawn journeyed billions of kilometers over four years to the main asteroid belt . there , it visited ceres and another asteroid , vesta . dawn 's stunning images transformed piazzi 's dot of light into a spectacular landscape of craters , landslides , and mountains .
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we have n't lost track of it since . today , we 've discovered hundreds of thousands of asteroids . many , including ceres , orbit the sun between mars and jupiter , while near-earth asteroids orbit the sun relatively close to earth . when we recorded this narration , astronomers had discovered 16,407 near-earth asteroids , but since we find new asteroids all the time , that number will have grown by hundreds or thousands by the time you watch this . today , asteroid hunters use modern telescopes , including one in space .
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at the time this narration was recorded , how many near-earth asteroids had been discovered ?
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few individuals have influenced the world and many of today 's thinkers like plato . one 20th century philosopher even went so far as to describe all of western philosophy as a series of footnotes to plato . he created the first western university and was teacher to ancient greece 's greatest minds , including aristotle . but even one of the founders of philosophy was n't perfect . along with his great ideas , plato had a few that have n't exactly stood the test of time . so here are brief rundowns of a few of his best and worst ideas . plato argued that beyond our imperfect world was a perfect unchanging world of forms . forms are the ideal versions of the things and concepts we see around us . they serve as a sort of instruction manual to our own world . floating around the world of forms is the ideal tree , and the ideal youtube channel , and even the ideal justice , or ideal love . our own reality is comprised of imperfect copies of ideal forms . plato argued that philosophers should strive to contemplate and understand these perfect forms so that they may better navigate our misleading reality . while it may seem silly , the disconnect between the world as it appears and the greater truth behind it is one of philosophy 's most vexing problems . it 's been the subject of thousands of pages by theologians , philosophers , and screenwriters alike . it raises questions like should we trust our senses to come to the truth or our own reason ? for plato , the answer is reason . it alone provides us with at least the potential to contemplate the forms . but reason did n't always pan out for plato himself . when he sought to situate humankind amongst the animals , he lumped us in with birds . `` featherless bipeds '' was his official designation . diogenes the cynic , annoyed by this definition , stormed into plato 's class with a plucked chicken , announcing , `` behold . plato 's man . '' but back to a few good ideas . plato is one of the earliest political theorists on record , and with aristotle , is seen as one of the founders of political science . he reasoned that being a ruler was no different than any other craft , whether a potter or doctor , and that only those who had mastered the craft were fit to lead . ruling was the craft of contemplating the forms . in his republic , plato imagined a utopia where justice is the ultimate goal . plato 's ideal city seeks a harmonious balance between its individual parts and should be lead by a philosopher king . millennia before his time , plato also reasoned that women were equally able to rule in this model city . unfortunately , plato was inconsistent with women , elsewhere likening them to children . he also believed that a woman 's womb was a live animal that could wander around in her body and cause illness . this bad idea , also espoused by other contemporaries of plato , was sadly influential for hundreds of years in european medicine . furthermore , he thought that society should be divided into three groups : producers , the military , and the rulers , and that a great noble lie should convince everyone to follow this structure . the noble lie he proposed was that we 're all born with gold , silver , or a mixture of brass and iron in our souls , which determine our roles in life . some thinkers have gone on to credit the idea of the noble lie as a prototype for 20th century propaganda , and the philosopher king as inspiration for the dictators that used them . should a few bad ideas tarnish plato 's status as one of the greatest philosophers in history ? no ! plato gave the leaders and thinkers who came after him a place to start . through the centuries , we 've had the chance to test those ideas through writing and experience , and have accepted some while rejecting others . we are continuing to refine , amend , and edit his ideas which have become foundations of the modern world .
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diogenes the cynic , annoyed by this definition , stormed into plato 's class with a plucked chicken , announcing , `` behold . plato 's man . '' but back to a few good ideas .
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why does plato think rationality is superior to sense experience for achieving knowledge ?
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in 1997 , jk rowling published harry potter and the philosopher 's stone . but most of her audience didn ’ t actually read that book . they read harry potter and the sorcerer ’ s stone . or harry potter a l'ecole des sorciers harry potter va sang-e jadu harry potter y la piedra filosofal [ cool humming of `` hedwig 's theme '' ] the bewitching harry potter books have reached readers in over 200 territories in over 60 languages . the authorized translations came from separate publishing houses with little oversight from the author . so translators were not only tasked with adapting the text from english into their target languages and cultures , but also making assumptions about rowling ’ s intentions and translating the spirit of her approach . their task was particularly challenging because the harry potter series is filled with invented words , alliteration , wordplay , and british cultural references . the main characters first names : harry , hermione , and ron mostly stayed the same across languages , with small changes to accommodate different alphabets and phonetics . that ’ s easy enough for conventional names like harry potter . but many of the other proper names in the book carry loaded meanings — meanings that would be lost if it ’ s not translated . take severus snape . the name invokes severity and sounds like “ snake. ” so the italian translator made the jump and named him severus piton —which is basically python . in french , he ’ s severus rogue which means severus `` arrogance '' . as you can tell , both solutions sacrificed rowling ’ s alliteration . the name “ hogwarts ” combines two english words , but because the name stayed the same in most languages , those connotations were lost for those readers . in an attempt to preserve rowling ’ s approach to the school ’ s name , the french translator used “ poudlard. ” `` pou du lard '' means lice of bacon or fat . the hungarian version went with “ roxfort ” a mix of the british university oxford and roquefort—a well known blue cheese . the house names and founders , also experienced unique adaptations in some of the target languages . in catalan the names became : nícanor griffindor , sírpentin slytherin , mari pau ravenclaw , and horténsia hufflepuff . there ’ s a ton of word play that happens in the harry potter books as well . the famous diagon alley , a play on the word `` diagonally '' and the infamous knockturn alley from `` nocturnally '' . this type of pun is a real puzzle for translators , and most dropped it in favor of literal translations . the spanish translator was able to rhyme at least with “ callejón diagon. ” and translators had several approaches to quidditch , an invented game made from the invented words quaffle , bludger , and snitch— the 3 types of balls used in the game . in spanish , the words were not changed . the french translator kept the word quidditch but changed the names of the balls . and others changed the game ’ s name altogether . in dutch , quidditch is “ zwerkbal. ” in norwegian , it ’ s “ rumpeldunk . '' owls and newts , standardized tests in the wizarding world , weren ’ t always able to retain their animal acronyms . but in swedish their implied meanings remained while the wording was changed . owls became grund examen i trollkonst or g.e.t meaning goat in swedish . and newts were changed to fruktansvärt utmattande trollkarls test or f.u.t.t . derived from `` futtig '' meaning measly or mean . the infamous anagram of tom marvolo riddle ’ s name was altered by many translators to achieve the same revelation of “ i am lord voldemort. ” in danish , tom is named `` romeo g. detlev jr. '' and in french he is “ tom elvis jedusor ” which was extra clever because `` jeu du sort '' means “ fate riddle. ” culturally , the harry potter series is unmistakably british but translating that for a global group of readers wasn ’ t easy . some food items were changed to make them less foreign for the target country . sherbet lemons , a popular candy item in britain , became krembo , a chocolate covered sweet from israel . crisps became chips in the us and in the arabic version , bacon became eggs . sometimes a foreign setting undergoes translation too . for the ukrainian translation , the atmosphere of an english boarding school was swapped out for an orphanage . in the books and films , hagrid has a provincial west country accent . hagrid : `` no ? blimey harry , did n't you ever wonder where your mum and dad learned it all ? '' `` you 're a wizard , harry . '' for the japanese translations , it was replicated by using tōhoku dialect , which is a pastoral accent from northeastern japan . other translators chose to have hagrid simply speak more informally , while others dropped his accent entirely . despite translators ’ best efforts to remain true to the text some things still were lost in translation . in the mainland chinese editions of harry potter there were footnotes to explain puns and cultural references . the spanish translator sometimes used italics to signal an invented word with no translation . but in the end , it doesn ’ t matter if you ’ re reading harry potter and philosopher ’ s stone or the many translations of it . one thing that always seems to translate is the love fans around the world share for tales of `` the boy who lived . ''
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but most of her audience didn ’ t actually read that book . they read harry potter and the sorcerer ’ s stone . or harry potter a l'ecole des sorciers harry potter va sang-e jadu harry potter y la piedra filosofal [ cool humming of `` hedwig 's theme '' ] the bewitching harry potter books have reached readers in over 200 territories in over 60 languages . the authorized translations came from separate publishing houses with little oversight from the author .
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what are some factors that make it challenging to translate harry potter ?
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( music ) the eight traits successful people have in common . number one : passion . successful people love what they do . when i asked russell crowe what led to his academy award for best actor , he said , `` the bottom line is i love the actual job of acting . i have a great passion for it . '' successful people in all fields love what they do , whether it 's astrophysicist jaymie matthews , author j.k. rowling or athlete michael phelps . and not just big names -- margaret macmillan , a history professor , says , `` i spent my life doing what i loved . '' carlos , a bus driver i sit with at starbucks , says , `` i love what i do . i 've only missed three days in four years . '' and believe it or not , even successful dentists love what they do . izzy novak says , `` i love dentistry . i ca n't imagine being anything else . '' but what about business ? many of you are in business , and we tend to think that business is more about cold numbers than hot passion , more about logic than love , so what surprised me was how often successful business people actually use the words `` passion '' or `` love '' when they talk about their work . when jack welch was ceo of general electric , he was asked if he liked his job . he said , `` no , i do n't like this job . i love this job . '' we can have passion for a profession . kathleen lane , chief strategist at workcar , says , `` i 've found a profession i love . '' she also says , `` stress is n't working 15 hours at a job you like , stress is working 15 minutes at a job you dislike . '' we can have a passion for people . nez hallett iii , ceo of smart wireless , says , `` i used to be in sales . now i 'm a ceo . i just love being around people . '' we can have passion for a product . james dyson , the vacuum cleaner guy , says , `` i love vacuum cleaners , and i will love them until the day i die . '' ( laughter ) yup , when he dies , they 're just going to cremate him and suck up those ashes with a dyson vacuum , and place it on the shelf . ( laughter ) we can have passion for a particular field . anita roddick , the great founder of the body shop , once said , `` i love retailing . i love buying and selling and making connections . '' she also said , `` i do n't like systems , financial sheets or plans . '' yes , no matter how much we love what we do , there 's always going to be stuff we do n't love . the trick is to make sure the stuff you do n't love only takes up 20 percent of your time , and the stuff you do love takes up 80 . if it 's the other way around , we 're in the wrong job . passion is sometimes mistaken for ambition . people call donald trump ambitious , but he says , `` i 'm not ambitious . i just love what i do . and if you love what you do , you do a lot of stuff . and then people say , 'oh , you 're ambitious . ' '' the cool thing about passion is it turns underachievers into superachievers . i have a long list of famous underachievers -- like albert einstein -- who people said would go nowhere when they were young . for instance , who said this , besides me ? `` i was sitting in my room being a depressed guy , trying to figure out what i was doing with my life . '' turns out it was bill gates . bill was such an underachiever , his parents actually sent him to counseling . yeah , i can just hear the neighbors back then saying , `` jeez , that gates kid . what a loser . he 's never going to go anywhere . '' and he did n't , until he discovered his passion for software . the big problem is finding your passion . sure , there 's the kid that knows they want to be an accountant or an architect or an astronaut from the time they 're 10 , but i found a much bigger group of successful people who , when they were young , and even when they were older , did n't have a clue what their passion was , and it took them a long time to find it or to fall into it . dawn lepore , chief information officer at charles schwab , said to me , `` i fell into what i do , and i did n't know i loved it until i fell into it . '' and i hear that a lot . so how do people find their passion ? well they just get out there and try a lot of stuff and explore many paths . robert munsch explored many paths . he said to me , `` i studied to be a priest and that turned out to be a disaster . i tried working on a farm . they did n't like me . i worked on a boat . it sank . i tried a lot of things that did n't work , but i kept trying and then i tried something that did work . '' and i 'd say it worked ; as a children 's author , he 's sold over 40 million books . yes , finding a job we love is like finding a person we love . sometimes we 've just got to go on a lot of really bad dates before we find the right one . now , i read a survey of 18- to 25-year-olds , and 81 percent said their first or second life goal was to get rich . and i thought , boy , they 've got it all wrong . because i 've interviewed many millionaires and billionaires , and guess how many of them said their life goal was to get rich ? zero ! they did n't do it for money , they did it for love . they went for the zing , not the ka-ching ka-ching . when bill gates and paul allen started microsoft , they did n't do it for the money . bill says , `` paul and i never thought we 'd make much money . we just loved writing software . '' and with that attitude , he became the richest man in the world . j.k. rowling did n't write harry potter books for the money . she said , `` i love writing these books . i just wanted to make enough money to continue to write . '' and with that attitude , she became a billionaire . i became a millionaire by following my heart , not my wallet , and a number of times i walked away from great-paying jobs to do poor-paying jobs i loved better . once was when i had a great job , traveling the world , making a lot of money , but i was n't doing the one thing i loved at the time , which was photography . so i said , i think i 'll leave and start my own little photo company . my heart said , yeah ! go for it . my wallet , and all my friends , i might add , said , are you crazy ? you ca n't walk away from all the money ! you 'll starve . i did n't listen to them . i walked away , and yeah , at first there was n't much money , but it did n't matter , because i was having fun doing what i loved . and eventually , the money came , and much more than if i 'd stayed in my old job . so i learned it 's true , what they say : if you do what you love , the money comes anyway . so i 'd say if you really want to get rich , put money at the bottom of your goals list and passion at the top . and why does it work that way ? because if you love what you do , you automatically do the other seven things that lead to success and wealth . you will work hard , you will push yourself , you will persist . and what if you 're in a job you do n't love ? well , just follow your passion on the side . remember , albert einstein was a patent clerk . that was his job , but his passion was physics . and he wrote four of his most important papers in his spare time as a hobby , and became one of the world 's greatest scientists . so it 's amazing what you can do if you love what you do . ( applause )
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kathleen lane , chief strategist at workcar , says , `` i 've found a profession i love . '' she also says , `` stress is n't working 15 hours at a job you like , stress is working 15 minutes at a job you dislike . '' we can have a passion for people .
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what ’ s the second part of this quote ? “ stress isn ’ t working 15 hours at a job you like … ”
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this is the bop . the bop is a type of social dance . dance is a language , and social dance is an expression that emerges from a community . a social dance is n't choreographed by any one person . it ca n't be traced to any one moment . each dance has steps that everyone can agree on , but it 's about the individual and their creative identity . because of that , social dances bubble up , they change , and they spread like wildfire . they are as old as our remembered history . in african-american social dances , we see over 200 years of how african and african-american traditions influenced our history . the present always contains the past . and the past shapes who we are and who we will be . ( clapping ) the juba dance was born from enslaved africans ' experience on the plantation . brought to the americas , stripped of a common spoken language , this dance was a way for enslaved africans to remember where they 're from . it may have looked something like this . slapping thighs , shuffling feet and patting hands : this was how they got around the slave owners ' ban on drumming , improvising complex rhythms just like ancestors did with drums in haiti or in the yoruba communities of west africa . it was about keeping cultural traditions alive and retaining a sense of inner freedom under captivity . it was the same subversive spirit that created this dance : the cakewalk , a dance that parodied the mannerisms of southern high society -- a way for the enslaved to throw shade at the masters . the crazy thing about this dance is that the cakewalk was performed for the masters , who never suspected they were being made fun of . now you might recognize this one . 1920s -- the charleston . the charleston was all about improvisation and musicality , making its way into lindy hop , swing dancing and even the kid n play , originally called the funky charleston . started by a tight-knit black community near charleston , south carolina , the charleston permeated dance halls where young women suddenly had the freedom to kick their heels and move their legs . now , social dance is about community and connection ; if you knew the steps , it meant you belonged to a group . but what if it becomes a worldwide craze ? enter the twist . it 's no surprise that the twist can be traced back to the 19th century , brought to america from the congo during slavery . but in the late '50s , right before the civil rights movement , the twist is popularized by chubby checker and dick clark . suddenly , everybody 's doing the twist : white teenagers , kids in latin america , making its way into songs and movies . through social dance , the boundaries between groups become blurred . the story continues in the 1980s and '90s . along with the emergence of hip-hop , african-american social dance took on even more visibility , borrowing from its long past , shaping culture and being shaped by it . today , these dances continue to evolve , grow and spread . why do we dance ? to move , to let loose , to express . why do we dance together ? to heal , to remember , to say : `` we speak a common language . we exist and we are free . ''
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1920s -- the charleston . the charleston was all about improvisation and musicality , making its way into lindy hop , swing dancing and even the kid n play , originally called the funky charleston . started by a tight-knit black community near charleston , south carolina , the charleston permeated dance halls where young women suddenly had the freedom to kick their heels and move their legs .
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what are some sources of linguistic play that could influence the development of rhythm ?
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a toothpaste brand claims their product will destroy more plaque than any product ever made . a politician tells you their plan will create the most jobs . we 're so used to hearing these kinds of exaggerations in advertising and politics that we might not even bat an eye . but what about when the claim is accompanied by a graph ? afterall , a graph is n't an opinion . it represents cold , hard numbers , and who can argue with those ? yet , as it turns out , there are plenty of ways graphs can mislead and outright manipulate . here are some things to look out for . in this 1992 ad , chevy claimed to make the most reliable trucks in america using this graph . not only does it show that 98 % of all chevy trucks sold in the last ten years are still on the road , but it looks like they 're twice as dependable as toyota trucks . that is , until you take a closer look at the numbers on the left and see that the figure for toyota is about 96.5 % . the scale only goes between 95 and 100 % . if it went from 0 to 100 , it would look like this . this is one of the most common ways graphs misrepresent data , by distorting the scale . zooming in on a small portion of the y-axis exaggerates a barely detectable difference between the things being compared . and it 's especially misleading with bar graphs since we assume the difference in the size of the bars is proportional to the values . but the scale can also be distorted along the x-axis , usually in line graphs showing something changing over time . this chart showing the rise in american unemployment from 2008 to 2010 manipulates the x-axis in two ways . first of all , the scale is inconsistent , compressing the 15-month span after march 2009 to look shorter than the preceding six months . using more consistent data points gives a different picture with job losses tapering off by the end of 2009 . and if you wonder why they were increasing in the first place , the timeline starts immediately after the u.s. 's biggest financial collapse since the great depression . these techniques are known as cherry picking . a time range can be carefully chosen to exclude the impact of a major event right outside it . and picking specific data points can hide important changes in between . even when there 's nothing wrong with the graph itself , leaving out relevant data can give a misleading impression . this chart of how many people watch the super bowl each year makes it look like the event 's popularity is exploding . but it 's not accounting for population growth . the ratings have actually held steady because while the number of football fans has increased , their share of overall viewership has not . finally , a graph ca n't tell you much if you do n't know the full significance of what 's being presented . both of the following graphs use the same ocean temperature data from the national centers for environmental information . so why do they seem to give opposite impressions ? the first graph plots the average annual ocean temperature from 1880 to 2016 , making the change look insignificant . but in fact , a rise of even half a degree celsius can cause massive ecological disruption . this is why the second graph , which show the average temperature variation each year , is far more significant . when they 're used well , graphs can help us intuitively grasp complex data . but as visual software has enabled more usage of graphs throughout all media , it 's also made them easier to use in a careless or dishonest way . so the next time you see a graph , do n't be swayed by the lines and curves . look at the labels , the numbers , the scale , and the context , and ask what story the picture is trying to tell .
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and if you wonder why they were increasing in the first place , the timeline starts immediately after the u.s. 's biggest financial collapse since the great depression . these techniques are known as cherry picking . a time range can be carefully chosen to exclude the impact of a major event right outside it .
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list three methods of “ cherry picking data ” and the advantages each provides .
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to many , one of the coolest things about `` game of thrones '' is that the inhabitants of the dothraki sea have their own real language . and dothraki came hot on the heels of the real language that the na'vi speak in `` avatar , '' which , surely , the na'vi needed when the klingons in `` star trek '' have had their own whole language since 1979 . and let 's not forget the elvish languages in j.r.r . tolkien 's `` lord of the rings '' trilogy , especially since that was the official grandfather of the fantasy conlangs . `` conlang '' is short for `` constructed language . '' they 're more than codes like pig latin , and they 're not just collections of fabricated slang like the nadsat lingo that the teen hoodlums in `` a clockwork orange '' speak , where `` droog '' from russian happens to mean `` friend . '' what makes conlangs real languages is n't the number of words they have . it helps , of course , to have a lot of words . dothraki has thousands of words . na'vi started with 1,500 words . fans on websites have steadily created more . but we can see the difference between vocabulary alone and what makes a real language from a look at how tolkien put together grand old elvish , a conlang with several thousands words . after all , you could memorize 5,000 words of russian and still be barely able to construct a sentence . a four-year-old would talk rings around you . that 's because you have to know how to put the words together . that is , a real language has grammar . elvish does . in english , to make a verb past , you add an `` -ed . '' wash , washed . in elvish , `` wash '' is `` allu '' and `` washed '' is `` allune . '' real languages also change over time . there 's no such thing as a language that 's the same today as it was a thousand years ago . as people speak , they drift into new habits , shed old ones , make mistakes , and get creative . today , one says , `` give us today our daily bread . '' in old english , they said , `` urne gedaeghwamlican hlaf syle us todaeg . '' things change in conlangs , too . tolkien charted out ancient and newer versions of elvish . when the first elves awoke at cuiviénen , in their new language , the word for `` people '' was `` kwendi , '' but in the language of one of the groups that moved away , teleri , over time , `` kwendi '' became `` pendi , '' with the `` k '' turning into a `` p. '' and just like real languages , conlangs like elvish split off into many . when the romans transplanted latin across europe , french , spanish , and italian were born . when groups move to different places , over time , their ways of speaking grow apart , just like everything else about them . thus , latin 's word for hand was `` manus , '' but in french , it became `` main , '' while in spain it became `` mano . '' tolkien made sure elvish did the same kind of thing . while that original word `` kwendi '' became `` pendi '' among the teleri , among the avari , who spread throughout middle earth , it became `` kindi '' when the `` w '' dropped out . the elvish varieties tolkien fleshed out the most are quenya and sindarin , and their words are different in the same way french and spanish are . quenya has `` suc '' for `` drink , '' sindarin has `` sog . '' and as you know , real languages are messy . that 's because they change , and change has a way of working against order , just like in a living room or on a bookshelf . real languages are never perfectly logical . that 's why tolkien made sure that elvish had plenty of exceptions . lots of verbs are conjugated in ways you just have to know . take even the word `` know . '' in the past , it 's `` knew , '' which is n't explained by any of the rules in english . oh well . in elvish , `` know '' is `` ista , '' but `` knew '' is `` sinte . '' oh well . the truth is , though , that elvish is more a sketch for a real language than a whole one . for tolkien , elvish was a hobby rather than an attempt to create something people could actually speak . much of the elvish the characters in the `` lord of the rings '' movies speak has been made up since tolkien by dedicated fans of elvish based on guesses as to what tolkien would have constructed . that 's the best we can do for elvish because there are no actual elves around to speak it for us . but the modern conlangs go further . dothraki , na'vi , and klingon are developed enough that you can actually speak them . here 's a translation of `` hamlet '' into klingon , although performing it would mean getting used to pronouncing `` k '' with your uvula , that weird , cartoony thing hanging in the back of your throat . believe it or not , you actually do that in plenty of languages around the world , like eskimo ones . pronouncing elvish is much easier , though . so , let 's take our leave for now from this introduction to conlangs in elvish and the other three conlangs discussed with a heartfelt quad-conlangual valedictory : `` a na marie ! '' `` hajas ! '' na'vi 's `` kiyevame ! '' `` qapla ! '' and `` goodbye ! ''
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elvish does . in english , to make a verb past , you add an `` -ed . '' wash , washed .
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making a present tense verb into a past one , as in walk and walked , is using
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if you ever find yourself gazing at falling snow , why not catch a few snowflakes on your glove and examine their shapes ? you might notice that they look symmetrical , and if you look closely , you 'll see they have six sides . you could say a snowflake is simply frozen water , but compare one with an ice cube from the freezer , and you 'll realize they 're very different things . unlike ice cubes , formed when liquid freezes into a solid , snowflakes form when water vapor turns straight into ice . but that still does n't explain why snowflakes have six sides . to understand that , we need to delve deeper into the physics of water . water is made out of two hydrogen atoms and one oxygen atom . a single water molecule thus has ten protons and ten electrons , eight from oxygen and one from each hydrogen atom . the two electrons from oxygen 's outer shell are shared with two electrons from both hydrogens as they bond together , and the remaining four outer shell electrons from oxygen form two pairs . we call the bonds between these atoms covalent bonds . the pairs of electrons are all negatively charged . similar charges repel , so they tend to stay as far away from each other as possible . the pairs form four electron clouds , two of which are where the hydrogen and oxygen share electrons . the repulsion between the unbonded pairs is even stronger than repulsion between the shared pairs , so the two hydrogens get pushed a little further to an angle of 104.5 degrees . the water molecule as a whole is electrically neutral , but oxygen gets a larger share of electrons , making it slightly negative and the hydrogens slightly positive . due to its negative charge , the oxygen in one molecule is attracted to the positive charge of the hydrogen in another molecule . and so a weak bond between the two molecules , called a hydrogen bond , is formed . when water freezes , this bonding occurs on repeat , ultimately forming a hexagonal structure due to the angle between hydrogens and oxygen within each molecule . this is the seed of a snowflake , and it retains a hexagonal shape as it grows . as the snowflake moves through the air , water vapor molecules stick to the six sharp edges and expand the snowflake outwards , bit by bit . a snowflake 's developing shape depends on atmospheric conditions , like humidity and temperature . as a snowflake falls , changes in weather conditions can affect how it grows , and even small differences in the paths two snowflakes take will differentiate their shapes . however , since conditions at the six sharp edges of one snowflake are similar , a symmetric snowflake can grow . weather conditions affect snow on the ground , as well . warmer ground temperatures produce a wetter snow that is easier to pack because liquid water molecules help snowflakes stick to each other . melted snow also plays a critical role in another wintry activity , skiing . completely dry snow is very difficult to ski on because there 's too much friction between the jagged snowflakes and the ski surface . so what 's happening is that as skis move , they rub the surface of the snow and warm it up , creating a thin layer of water , which helps them slide along . so technically , it 's not really snow skiing , but water skiing . but it is true that no matter how hard you look , you 're almost definitely not going to find two identical snowflakes , and that 's a mystery that scientists are still trying to solve , though we know that it has to do with the many possible branching points in snowflake formation , and the differences in temperature and humidity , and while we wait for the answer , we can enjoy watching these tiny fractals falling from the sky .
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as the snowflake moves through the air , water vapor molecules stick to the six sharp edges and expand the snowflake outwards , bit by bit . a snowflake 's developing shape depends on atmospheric conditions , like humidity and temperature . as a snowflake falls , changes in weather conditions can affect how it grows , and even small differences in the paths two snowflakes take will differentiate their shapes . however , since conditions at the six sharp edges of one snowflake are similar , a symmetric snowflake can grow .
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we say that no two snowflakes are the same because they all form under different conditions . but why do they look so symmetric ?
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translator : tom carter reviewer : bedirhan cinar of all the spectacles mankind has viewed through a telescope , there are few lovelier than a spiral galaxy . majestic whirlpools of stars , they rotate in a stately and predictable dance . the fact that we see many billions of them in our telescopes tells us they are both common and stable . it is perhaps surprising that it is relatively easy to understand the inner workings of these cosmic pinwheels . by combining physical principles worked out by sir isaac newton in the late 17th century , with the observed amount of mass in a galaxy , scientists can calculate the rates at which these galaxies rotate . using these techniques , astronomers predict how fast stars at different distances from the center of the galaxy should move . stars very close to the center move slowly . that 's because there is very little mass between them and the center of the galaxy to pull them along . stars a bit further away move faster , because they are being pulled by all of the stars in between them and the center . as we get really far away , the stars are predicted to move slowly again . their great distance reduces gravity to a gentle tug , so they move leisurely in their orbits . knowing this , scientists looked at the galaxies and measured how fast stars were moving . to their surprise , they found that while the stars closer to the center of the galaxy behaved as predicted , those further away moved far too quickly . this observation was devastating to the tradtional theories of gravity and motion . if the stars were moving as fast as their measurement suggested , galaxies should have torn themselves apart . it was a crisis , and astronomers and physicists scrambled to find a mistake in their calculation . was newton 's theory of gravity wrong ? was his theory of motion wrong ? or was it possible that astronomers had incorrectly measured the galaxy 's mass ? all options were investigated , and all were ruled out . except one . today , scientists believe that the answer lies in a previously unknown kind of matter , called dark matter . this dark matter can be envisioned as a cloud which surrounds most galaxies . this matter is very unusual . it is affected by gravity , but it is invisible to visible light and all other forms of electromagnetic radiation . the name `` dark matter '' originates in this form of matter 's inability to emit or absorb light . dark matter adds to the gravity of the galaxy and explains the orbital speed of stars far from the galactic center . dark matter has not yet been directly observed , but scientists believe that it is likely to be real , mostly because the other options have been ruled out . using dozens of approaches , astronomers and physicists continue to search for direct evidence that would prove that the dark matter hypothesis is true . this question is one of the most important physics research questions of the 21st century .
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except one . today , scientists believe that the answer lies in a previously unknown kind of matter , called dark matter . this dark matter can be envisioned as a cloud which surrounds most galaxies . this matter is very unusual . it is affected by gravity , but it is invisible to visible light and all other forms of electromagnetic radiation .
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which is not true about dark matter ?
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diabetes mellitus has been a scourge of the developed world with an estimated 400,000,000 people worldwide suffering from this disease , and 50 % more predicted within twenty years . its early symptoms , which include increased thirst and large volumes of urine , were recognized as far back as 1500 bce in egypt . while the term diabetes , meaning `` to pass through , '' was first used in 250 bce by the greek physician apollonius of memphis , type 1 and type 2 diabetes , associated respectively with youth and obesity , were identified as separate conditions by indian physicians somewhere in the 5th century ce . but despite the disease being known , a diagnosis of diabetes in a human patient would remain tantamount to a death sentence until the early 20th century , its causes unknown . what changed this dire situation was the help of humanity 's longtime animal partner : canis lupus familiaris , domesticated from grey wolves thousands of years ago . in 1890 , the german scientists von mering and minkowski demonstrated that removing a dog 's pancreas caused it to develop all the signs of diabetes , thus establishing the organ 's central role in the disease . but the exact mechanism by which this occurred remained a mystery until 1920 , when a young canadian surgeon named frederick banting and his student , charles best , advanced the findings of their german colleagues . working under professor macleod at the university of toronto , they confirmed that the pancreas was responsible for regulating blood glucose , successfully treating diabetic dogs by injecting them with an extract they had prepared from pancreas tissue . by 1922 , the researchers working with biochemist james collip were able to develop a similar extract from beef pancreas to first treat a 14-year-old diabetic boy , followed by six additional patients . the manufacturing process for this extract , now known as insulin , was eventually turned over to a pharmaceutical company that makes different types of injectable insulin to this day . banting and macleod received the nobel prize for medicine in 1923 for their discovery . but banting chose to share his portion with charles best , for his help in the initial studies involving dogs . but while medical experimentation on animals remains controversial , in this case at least , it was not just a matter of exploiting dogs for human needs . dogs develop diabetes at the rate of two cases per 1,000 dogs , almost the same as that of humans under 20 . most canine cases are of type 1 diabetes , similar to the type that young children develop following immune system destruction of the pancreas , and genetic studies have shown that the dog disease has many similar hallmarks of the human disease . this has allowed veterinarians to turn the tables , successfully using insulin to treat diabetes in man 's best friend for over 60 years . many dog owners commit to managing their dogs ' diabetes with insulin injected twice daily , regimented feedings , and periodic blood measurements using the same home-testing glucose monitors used by human patients . and if the purified pig insulin commonly used for dogs fails to work for a particular dog , the vet may even turn to a formulation of human insulin , bringing the process full circle . after all that dogs have done for us throughout the ages , including their role in a medical discovery that has saved countless human lives , using that same knowledge to help them is the least we could do .
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many dog owners commit to managing their dogs ' diabetes with insulin injected twice daily , regimented feedings , and periodic blood measurements using the same home-testing glucose monitors used by human patients . and if the purified pig insulin commonly used for dogs fails to work for a particular dog , the vet may even turn to a formulation of human insulin , bringing the process full circle . after all that dogs have done for us throughout the ages , including their role in a medical discovery that has saved countless human lives , using that same knowledge to help them is the least we could do .
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today , when diabetic dogs can not be successfully treated with pig insulin , veterinarians may then treat them with ____ insulin .
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translator : andrea mcdonough reviewer : jessica ruby around 1469 , a wealthy money changer commissioned a young painter named sandro botticelli to paint an altar piece . botticelli would , of course , become known as one of the greatest painters of the high renaissance , producing works like `` la primavera '' and `` the birth of venus . '' but , in 1469 , he had not yet earned this reputation . the scene this young artist set out to paint was well-known : the three wise men , or magi , arriving at the birth place of jesus christ . botticelli would aspire to take this common theme and produce an entirely original work , while asserting himself among the most important citizens of florence . many earlier paintings illustrate the magi arriving at a stable , stately manger , fitting for the son of god . the young botticelli , however , chose to place the scene in the dilapidated roman ruin . at the center of this structure , he placed a sturdy rock for mary and jesus to sit high above their visitors . with this decision , botticelli seemed to say christianity will be built on sturdier stuff than rome . botticelli then populated the space with important men from his city . on the right side , he paints the man who paid for this work , gaspare del lama , looking out at the viewer and confidently pointing at himself so that there is no question who is responsible for this masterpiece . though born the son of a barber , del lama amassed a good sum of money through currency exchange in his lifetime . he earned enough money to buy a burial chapel and decorate it with a pretty painting . the three wise men appear at the center of this painting , kneeling to mary and jesus . as models for these important figures , botticelli used members of the important medici family . del lama 's career as a money changer would not have been possible without the help of the powerful medici family , in particular cosimo de ' medici , who appears prominently at mary 's feet . the other wise men can be identified as piero and giovanni de ' medici , cosimo 's two sons . the business of money exchange had dubious ethical and legal associations , so the friendship of this powerful family was important . and the young heir to medici power , lorenzo , could not be omitted from this painting 's composition . he appears to the left of the manger . this painting seems to say the medici legacy , with its many healthy heirs , will be built on sturdier stuff than rome . botticelli then filled the rest of the space with other friends and powerful figures from florence . and , among the florentine elite , the young , confident artist painted himself looking directly at the viewer . botticelli 's presence in this painting illustrates a radical shift in the perception of artists during this time period . botticelli did not view himself as a common craftsman hired for a simple job . he viewed himself as a friend to the powerful families of florence . paintings like `` the adoration of the magi '' reveal much more than a simple retelling of a biblical story . they can tell the story of , among other things , a modestly-born money changer attempting to spend his money virtuously by making a local chapel more beautiful , or the story of an ambitious young painter , elevating the reputation of his craft to stand among the wealthy elite of his city .
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botticelli did not view himself as a common craftsman hired for a simple job . he viewed himself as a friend to the powerful families of florence . paintings like `` the adoration of the magi '' reveal much more than a simple retelling of a biblical story .
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what is the relationship between art and political power in 15th century florence ?
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remember the time you fell off your bike or bumped your head on a sharp corner ? childhood injuries are things we 'd often like to forget , but our bodies often carry the memories in the form of scars . so what are these unwanted souvenirs and why do we keep them for so long after that unintended vacation to the emergency room ? the most common place we see scars are on our skin , a patch that looks slightly different from the normal skin around it . often , this is considered an unfortunate disfigurement , while other times , deliberate scarification has been used in both traditional and modern cultures , to mark a rite of passage or simply for aesthetic decoration . but the difference is n't only cosmetic . when we look at healthy skin tissue under a microscope , we see the cells that perform various functions connected by an extracellular matrix , or ecm . this is composed of structural proteins , like collagen , secreted by specialized fibroblast cells . well-arranged ecm allows for transportation of nutrients , cell-to-cell communication , and cell adhesion . but when a deep wound occurs , this arrangement is disrupted . during the process of wound healing , collagen is redeposited at the wound site , but instead of the basket-weave formation found in healthy tissue , the new ecm is aligned in a single direction , impeding inter-cell processes , and reducing durability and elasticity . to make matters worse , the healed tissue contains a higher proportion of ecm than before , reducing its overall function . in the skin , the overabundance of collagen interferes with its original functions , like producing sweat , controlling body temperature and even growing hair . the scar tissue is fragile , sensitive to changes in temperature and sensation , and should be kept in moist environments to maximize healing . this presence of excessive fibrous connective tissue in an organ is known as fibrosis , and if that term sounds familiar , it 's because our skin is not the only organ vulnerable to scarring . cystic fibrosis is a genetic disorder that causes scarring of the pancreas , while pulmonary fibrosis is a scarring of the lungs , resulting in shortness of breath . scarring of the heart and the buildup of ecm following a heart attack can inhibit its beating , leading to further heart problems . what 's common to all these conditions is that although it retains some of the original functions , the scar tissue formed after a wound is inferior to the native tissue it replaces . however , there is hope . medical researchers are now studying what causes fibroblast cells to secrete excessive amounts of collagen and how we can recruit the body 's other cells in regenerating and repopulating the damaged tissue . by learning how to better control wound healing and the formation of scar tissue , we can utilize the multi-billion-dollar budgets currently used to address the aftermath of wounding in a much more efficient manner , and help millions of people live better and healthier lives . but until then , at least some of our scars can help us remember to avoid the sorts of things that cause them .
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well-arranged ecm allows for transportation of nutrients , cell-to-cell communication , and cell adhesion . but when a deep wound occurs , this arrangement is disrupted . during the process of wound healing , collagen is redeposited at the wound site , but instead of the basket-weave formation found in healthy tissue , the new ecm is aligned in a single direction , impeding inter-cell processes , and reducing durability and elasticity . to make matters worse , the healed tissue contains a higher proportion of ecm than before , reducing its overall function .
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what happens to the alignment of collagen deposited during the wound healing process ?
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i love astronomy . you may have noticed . but there ’ s one really frustrating aspect of it : everything we study is really far away . nearly everything we understand about the universe comes from light emitted or reflected by objects . it ’ d be nice if we could get actual samples from them ; physical specimens we could examine in the lab . welp , sometimes the universe can be accommodating , and allows us to hold it in our hands . cambot , can we get this up on still store ? if you go outside on a clear , dark , moonless night — and you really should — chances are pretty good that within a few minutes you ’ ll see a shooting star . it ’ ll zip across the sky , a fiery dot leaving a long glowing trail behind it . they ’ re one of the most exciting and fun things you ’ ll see when you look up , and they always get a gasp and a squeal of delight from people someone who ’ s stargazing . what you ’ re actually seeing is a tiny bit of interplanetary debris : rock , ice , or metal ramming through the earth ’ s atmosphere , heated to incandescence . most are faint , but some can be astonishingly bright ; i saw one once that left an afterimage on my eye ! obviously , shooting stars aren ’ t really stars . so what do we call them ? sometimes it seems like astronomers use different names for objects to keep things as confusing as possible . but really , we do that to separate out different things . in this case , the actual bit of solid stuff coming from space is called a meteoroid . the phenomenon of the meteoroid getting hot and blazing across the sky is called a meteor . and finally , if it hits the ground , we call it a meteorite . i think the second best way to tick off an astronomer is to mix up meteor and meteorite . sometimes astronomers can be pretty pedantic about such things . oh , the best way to tick off an astronomer ? ask them , “ hey , what ’ s your sign ? ” amazingly , a typical meteor that you ’ ll see is due to a meteoroid that ’ s tiny , probably smaller than a grain of sand ! how can that be ? it ’ s because they ’ re hauling mass . you heard me . the meteoroid is orbiting the sun , probably at speeds of a few dozen kilometers per second . as it approaches the earth , our planet ’ s gravity accelerates it an additional 11 kilometers per second — earth ’ s escape velocity . and when it enters our atmosphere it ’ s moving incredibly fast , up to 70 km/sec or more . the energy of motion is called kinetic energy . if you want to get something moving , you have to give it energy , and if you want it to stop , you have to take that energy away . this kinetic energy depends on the mass of the object and how fast it ’ s moving . in fact , it depends on the square of the velocity ; double its speed and it ’ ll have four times the kinetic energy . meteoroids may usually be small , but they ’ re screaming fast , and have a huge amount of kinetic energy . as they hit our atmosphere they slow from their ridiculous orbital speed to nearly a standstill , and all that energy has to go somewhere . it gets converted into light and heat , and that ’ s what we see as a meteor . a big misconception about meteors is that they get hot due to friction with air . actually , a far bigger contributor to their heat is compression . one of the most basic laws of physics is that when you compress a gas it heats up . and a meteoroid coming in at hypersonic speeds compresses the air in front of it a lot , heating it hugely . the gas can reach temperatures of thousands of degrees celsius for a few seconds . the air radiates away this heat , in turn heating up the meteoroid . the material on the surface vaporizes and blows away—a process called ablation . that ablated material leaves a glowing trail behind the meteor , which we call a train . sometimes it can glow for several minutes , getting twisted up in high altitude winds , leaving behind an eerie , ghost-like persistent train . this all happens high above your head , about 90 – 100 km above the ground . typically , from any one location , you can see a few meteors per hour . it may not seem like much , but when you add them up all over the planet you find the earth is getting pelted to the tune of about 100 tons of material a day . but again , most of these meteoroids are teeny tiny . those random meteors are called sporadic meteors . they tend to be rocky in composition , and generally come from asteroids . if two asteroids smack into each other , the collision can eject little bits of material that then orbit the sun on their own . if their orbit crosses the earth , then you have a potential meteor . it may take a few million years , but at some point the earth and the meteoroid are at the same place at the same time , and boom . but sometimes meteoroids travel in packs . when that happens , we can get meteor showers , many dozens or even hundreds of meteors per hour . with one exception , those don ’ t come from asteroids : they come from comets . when a comet orbits the sun , the ice on it turns to gas , dislodging dust and gravel mixed in . this material leaves the comet and tends to stay more or less in the same orbit as the comet itself . over time , that material gets scattered all along the orbit , creating a puffy ribbon of tiny pieces of space debris around the sun . when the earth plows through that cloud of debris , we get a meteor shower . from our viewpoint on earth we see meteors shooting across the sky , apparently radiating away from a single point . that ’ s a perspective effect ; it ’ s like driving through a tunnel and seeing the tiles on the wall and ceiling flying past you , all apparently coming from a point ahead of you . the point in the sky where the meteors come from is called the radiant , and the shower is named after the constellation the radiant ’ s in . so we have the perseid meteor shower , the leonids , the camelopardalids . or the camelopardalids . and , since the earth hits a specific comet stream around the same time every year , the showers are annual . the perseids are in august , and the leonids in november . watching a meteor shower is easy : just go outside and look up ! generally , they ’ re better after local midnight . the earth plows into the meteoroids , so facing the direction of earth ’ s orbital motion means more meteors , just like you get more raindrops on the front windshield of your car than than on the back when driving through a storm . after local midnight you ’ re on the part of the earth facing into the orbit , so you see more meteors . by the way , if you happen to be on the international space station , you have to look down to see a meteor . in 2011 , astronaut ron garan photographed a perseid burning up below him ! but don ’ t worry : the odds of the space station getting hit are extremely low . space is big . oh , and that one exception i mentioned before ? that ’ s the annual geminids shower , which occurs in december . that comes from the asteroid 3200 phaethon , which is on an orbit that takes it very close to the sun . it ’ s possible it gets so hot that the rock vaporizes , making it act like a comet . the vast majority of meteoroids are small and tend to burn up in our atmosphere . but they can be bigger . a bolide , or fireball , is an extremely bright meteor , and those can be about the size of a grapefruit . those happen pretty often somewhere over the earth . i ’ ve seen a few myself . very rarely , an incoming meteoroid will survive all the way to the ground and become a meteorite . sometimes , the immense pressure of ramming earth ’ s air causes the incoming meteoroid to crumble or even explode , raining down dozens or hundreds of smaller pieces . typically , they slow rapidly after their blaze of glory , and simply fall the rest of the way to the ground . the air up there is cold , and their interiors are cold from being in space so long . so , despite what you might think , meteorites don ’ t cause fires when they hit the ground . in fact , they can be quite chilly ! meteorites are classified into three broad categories : stony , which are mostly rock ; iron , which are mostly metal ; and stony iron , which are a mixture of the two . the majority of meteorites we find are stony . the stony meteorites are subdivided into two kinds : chondrites , and achondrites . chondrites contain chondrules , small grains of minerals . these are very primitive , and are thought to have condensed out of the original disk of material that formed the solar system . their age can be found by looking at ratios of elements in them formed from radioactive decay . the oldest known meteorite formed 4.568 billion years ago : before the earth itself formed ! achondrites don ’ t have chondrules in them . most likely they came from a bigger asteroid , one that was once molten through , mixing the minerals . a big collision disrupted the parent body , creating the achondritic meteoroids . iron meteorites most likely come from the center of a large asteroid , one big enough that metals fell to the center via gravity . again , a big impact blew the asteroid up , scattering its material around the asteroid belt , and with some on orbits that eventually intersected earth . stony irons are the rarest . some have green or orange crystals of a mineral called olivine embedded in a web of metal . called pallasites , they may be the most beautiful of all meteorites . i actually collect meteorites . it ’ s fun but can be a somewhat pricey hobby . if you ’ re interested , make sure you get ‘ em from a licensed dealer . we have links to some in the dooblydoo . of course , on occasion the meteoroid coming in can be a tad bigger . and when that happens , well , all hell can break loose . on february 15 , 2013 , residents of the russian city of chelyabinsk got a rude awakening . at 9:20 a.m. local time , a rock about 19 meters across came in at a low angle . it got nearly as bright as the sun as it slammed into the atmosphere , and the pressure of its passage broke it up into several chunks , which broke up again . in a moment ’ s time , the sudden energy released was equivalent to the detonation of a half million tons of tnt — as much as a small atomic bomb ! while no one was killed , over a thousand people were injured by flying glass , shattered by the explosion . no doubt they were at their windows gawking at the huge vapor trail in the sky when the shock wave hit . there was no warning for this event ; the asteroid was essentially too small to detect while it was out in space . well , for now at least . telescopes are coming online soon that should be able to find smaller asteroids and give us some warning . astronomers are more worried about ones roughly a hundred meters across or bigger ; these can do serious damage on a city-wide scale or larger , but at the moment aren ’ t easy to spot much in advance . and what do we do if we do see one headed our way ? as of right now , there ’ s not much we can do . studies have been done to determine the best course of action ; maybe lobbing a nuke at it , or simply ramming it with a spaceprobe to change the orbit and make sure it misses earth . these ideas look good on paper , but they haven ’ t been tested yet . we ’ re still a few years from that . the good news is that objects that size hitting the earth are rare ; maybe once every century or three . but if we do nothing , it will happen eventually . as science fiction writer larry niven points out , the dinosaurs went extinct because they didn ’ t have a space program . hopefully , we ’ re smarter than they were . today you learned that meteors are small bits of interplanetary debris sloughed off by asteroids and comets . when the earth plows through the stream emitted by a comet we get a meteor shower . meteors burn up about 100 km above the earth , but some survive to hit the ground . most of these meteorites are rocky , some are metallic , and a few are a mix of the two . very big meteorites can be a very big problem , but there are plans in the works to prevent us from going the way of the dinosaurs . crash course astronomy - hey crash course , meteors ! cool ! crash course astronomy is produced in association with pbs digital studios . head over to their channel for even more awesome videos . this episode was written by me , phil plait . the script was edited by blake de pastino , and our consultant is dr. michelle thaller . it was directed by nicholas jenkins , the script supervisor and editor is nicole sweeney , the sound designer was michael aranda , and the graphics team is thought café .
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meteorites are classified into three broad categories : stony , which are mostly rock ; iron , which are mostly metal ; and stony iron , which are a mixture of the two . the majority of meteorites we find are stony . the stony meteorites are subdivided into two kinds : chondrites , and achondrites .
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meteorites usually fall in one of these categories : stony , iron or stony iron . the majority of meteorites we find are ...
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the largest organ in your body is n't your liver or your brain . it 's your skin , with a surface area of about 20 square feet in adults . though different areas of the skin have different characteristics , much of this surface performs similar functions , such as sweating , feeling heat and cold , and growing hair . but after a deep cut or wound , the newly healed skin will look different from the surrounding area , and may not fully regain all its abilities for a while , or at all . to understand why this happens , we need to look at the structure of the human skin . the top layer , called the epidermis , consists mostly of hardened cells , called keratinocytes , and provides protection . since its outer layer is constantly being shed and renewed , it 's pretty easy to repair . but sometimes a wound penetrates into the dermis , which contains blood vessels and the various glands and nerve endings that enable the skin 's many functions . and when that happens , it triggers the four overlapping stages of the regenerative process . the first stage , hemostasis , is the skin 's response to two immediate threats : that you 're now losing blood and that the physical barrier of the epidermis has been compromised . as the blood vessels tighten to minimize the bleeding , in a process known as vasoconstriction , both threats are averted by forming a blood clot . a special protein known as fibrin forms cross-links on the top of the skin , preventing blood from flowing out and bacteria or pathogens from getting in . after about three hours of this , the skin begins to turn red , signaling the next stage , inflammation . with bleeding under control and the barrier secured , the body sends special cells to fight any pathogens that may have gotten through . among the most important of these are white blood cells , known as macrophages , which devour bacteria and damage tissue through a process known as phagocytosis , in addition to producing growth factors to spur healing . and because these tiny soldiers need to travel through the blood to get to the wound site , the previously constricted blood vessels now expand in a process called vasodilation . about two to three days after the wound , the proliferative stage occurs , when fibroblast cells begin to enter the wound . in the process of collagen deposition , they produce a fibrous protein called collagen in the wound site , forming connective skin tissue to replace the fibrin from before . as epidermal cells divide to reform the outer layer of skin , the dermis contracts to close the wound . finally , in the fourth stage of remodeling , the wound matures as the newly deposited collagen is rearranged and converted into specific types . through this process , which can take over a year , the tensile strength of the new skin is improved , and blood vessels and other connections are strengthened . with time , the new tissue can reach from 50-80 % of some of its original healthy function , depending on the severity of the initial wound and on the function itself . but because the skin does not fully recover , scarring continues to be a major clinical issue for doctors around the world . and even though researchers have made significant strides in understanding the healing process , many fundamental mysteries remain unresolved . for instance , do fibroblast cells arrive from the blood vessels or from skin tissue adjacent to the wound ? and why do some other mammals , such as deer , heal their wounds much more efficiently and completely than humans ? by finding the answers to these questions and others , we may one day be able to heal ourselves so well that scars will be just a memory .
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and because these tiny soldiers need to travel through the blood to get to the wound site , the previously constricted blood vessels now expand in a process called vasodilation . about two to three days after the wound , the proliferative stage occurs , when fibroblast cells begin to enter the wound . in the process of collagen deposition , they produce a fibrous protein called collagen in the wound site , forming connective skin tissue to replace the fibrin from before .
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applying plant extract and herbal medicine has been a long documented approach in alternative/complementary medicine to accelerate wound healing . do you think that these approaches are viable ? how would you scientifically validate their effect on wound healing ?
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what if william shakespeare had a sister who matched his imagination , his wit , and his way with words ? would she have gone to school and set the stage alight ? in her essay `` a room of one 's own , '' virginia woolf argues that this would have been impossible . she concocts a fictional sister who 's stuck at home , snatching time to scribble a few pages before she finds herself betrothed and runs away . while her brother finds fame and fortune , she remains abandoned and anonymous . in this thought experiment , woolf demonstrates the tragedy of genius restricted , and looks back through time for hints of these hidden histories . she wrote , `` when one reads of a witch being ducked , of a woman possessed by devils , of a wise woman selling herbs , or even a very remarkable man who had a mother , then i think we 're on the track of a lost novelist , a suppressed poet , of some mute and inglorious jane austen . '' `` a room of one 's own '' considers a world denied great works of art due to exclusion and inequality . how best can we understand the internal experience of alienation ? in both her essays and fiction , virginia woolf shapes the slippery nature of subjective experience into words . her characters frequently lead inner lives that are deeply at odds with their external existence . to help make sense of these disparities , the next time you read woolf , here are some aspects of her life and work to consider . she was born adeline virginia stephen in 1882 to a large and wealthy family , which enabled her to pursue a life in the arts . the death of her mother in 1895 was followed by that of her half-sister , father , and brother within the next ten years . these losses led to woolf 's first depressive episode and subsequent institutionalization . as a young woman , she purchased a house in the bloomsbury area of london with her siblings . this brought her into contact with a circle of creatives , including e.m. forster , clive bell , roger fry , and leonard woolf . these friends became known as the bloomsbury group , and virginia and leonard married in 1912 . the members of this group were prominent figures in modernism , a cultural movement that sought to push the boundaries of how reality is represented . key features of modernist writing include the use of stream of consciousness , interior monologue , distortions in time , and multiple or shifting perspectives . these appear in the work of ezra pound , gertrude stein , james joyce , and woolf herself . while reading joyce 's `` ulysses , '' woolf began writing `` mrs . dalloway . '' like `` ulysses , '' the text takes place over the course of a single day and opens under seemingly mundane circumstances . `` mrs. dalloway said she would buy the flowers herself . '' but the novel dives deeply into the characters ' traumatic pasts , weaving the inner world of numbed socialite clarissa dalloway , with that of the shell-shocked veteran septimus warren smith . woolf uses interior monologue to contrast the rich world of the mind against her characters ' external existences . in her novel `` to the lighthouse , '' mundane moments , like a dinner party , or losing a necklace trigger psychological revelations in the lives of the ramsay 's , a fictionalized version of woolf 's family growing up . `` to the lighthouse '' also contains one of the most famous examples of woolf 's radical representation of time . in the time passes section , ten years are distilled into about 20 pages . here , the lack of human presence in the ramsays ' beach house allows woolf to reimagine time in flashes and fragments of prose . `` the house was left . the house was deserted . it was left like a shell on a sand hill to fill with dry salt grains now that life had left it . '' in her novel `` the waves , '' there is little distinction between the narratives of the six main characters . woolf experiments with collective consciousness , at times collapsing the six voices into one . `` it is not one life that i look back upon : i am not one person : i am many people : i do not altogether know who i am , jinny , susan , neville , rhoda or louis , or how to distinguish my life from their 's . '' in `` the waves , '' six become one , but in the gender-bending `` orlando , '' a single character inhabits multiple identities . the protagonist is a poet who switches between genders and lives for 300 years . with its fluid language and approach to identity , `` orlando '' is considered a key text in gender studies . the mind can only fly so far from the body before it returns to the constraints of life . like many of her characters , woolf 's life ended in tragedy when she drowned herself at the age of 59 . yet , she expressed hope beyond suffering . through deep thought , woolf 's characters are shown to temporarily transcend their material reality , and in its careful consideration of the complexity of the mind , her work charts the importance of making our inner lives known to each other .
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in her novel `` the waves , '' there is little distinction between the narratives of the six main characters . woolf experiments with collective consciousness , at times collapsing the six voices into one . `` it is not one life that i look back upon : i am not one person : i am many people : i do not altogether know who i am , jinny , susan , neville , rhoda or louis , or how to distinguish my life from their 's . ''
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woolf ’ s use of collective consciousness in `` the waves '' :
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translator : andrea mcdonough reviewer : bedirhan cinar we all start life as one single cell . then that cell divides and we are two cells , then four , then eight . cells form tissues , tissues form organs , organs form us . these cell divisions , by which we go from a single cell to 100 trillion cells , are called growth . and growth seems like a simple thing because when we think of it , we typically think of someone getting taller or , later in life , wider , but to cells , growth is n't simple . cell division is an intricate chemical dance that 's part individual , part community-driven . and in a neighborhood of 100 trillion cells , some times things go wrong . maybe an individual cell 's set of instructions , or dna , gets a typo , what we call a mutation . most of the time , the cell senses mistakes and shuts itself down , or the system detects a troublemaker and eliminates it . but , enough mutations can bypass the fail-safes , driving the cell to divide recklessly . that one rogue cell becomes two , then four , then eight . at every stage , the incorrect instructions are passed along to the cells ' offspring . weeks , months , or years after that one rogue cell transformed , you might see your doctor about a lump in your breast . difficulty going to the bathroom could reveal a problem in your intestine , prostate , or bladder . or , a routine blood test might count too many white cells or elevated liver enzymes . your doctor delivers the bad news : it 's cancer . from here your strategy will depend on where the cancer is and how far it 's progressed . if the tumor is slow-growing and in one place , surgery might be all you need , if anything . if the tumor is fast-growing or invading nearby tissue , your doctor might recommend radiation or surgery followed by radiation . if the cancer has spread , or if it 's inherently everywhere like a leukemia , your doctor will most likely recommend chemotherapy or a combination of radiation and chemo . radiation and most forms of chemo work by physically shredding the cells ' dna or disrupting the copying machinery . but neither radiation nor chemotherapeutic drugs target only cancer cells . radiation hits whatever you point it at , and your blood stream carries chemo-therapeutics all over your body . so , what happens when different cells get hit ? let 's look at a healthy liver cell , a healthy hair cell , and a cancerous cell . the healthy liver cell divides only when it is stressed ; the healthy hair cell divides frequently ; and the cancer cell divides even more frequently and recklessly . when you take a chemotherapeutic drug , it will hit all of these cells . and remember that the drugs work typically by disrupting cell division . so , every time a cell divides , it opens itself up to attack , and that means the more frequently a cell divides , the more likely the drug is to kill it . so , remember that hair cell ? it divides frequently and is n't a threat . and , there are other frequently dividing cells in your body like skin cells , gut cells , and blood cells . so the list of unpleasant side effects of cancer treatment parallels these tissue types : hair loss , skin rashes , nausea , vomiting , fatigue , weight loss , and pain . that makes sense because these are the cells that get hit the hardest . so , in the end , it is all about growth . cancer hijacks cells ' natural division machinery and forces them to put the pedal to the metal , growing rapidly and recklessly . but , using chemotherapeutic drugs , we take advantage of that aggressiveness , and we turn cancer 's main strength into a weakness .
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but , enough mutations can bypass the fail-safes , driving the cell to divide recklessly . that one rogue cell becomes two , then four , then eight . at every stage , the incorrect instructions are passed along to the cells ' offspring .
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why does n't cancer just die off after one rogue division ?
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in the 16th century , the mathematician robert recorde wrote a book called `` the whetstone of witte '' to teach english students algebra . but he was getting tired of writing the words `` is equal to '' over and over . his solution ? he replaced those words with two parallel horizontal line segments because the way he saw it , no two things can be more equal . could he have used four line segments instead of two ? of course . could he have used vertical line segments ? in fact , some people did . there 's no reason why the equals sign had to look the way it does today . at some point , it just caught on , sort of like a meme . more and more mathematicians began to use it , and eventually , it became a standard symbol for equality . math is full of symbols . lines , dots , arrows , english letters , greek letters , superscripts , subscripts . it can look like an illegible jumble . it 's normal to find this wealth of symbols a little intimidating and to wonder where they all came from . sometimes , as recorde himself noted about his equals sign , there 's an apt conformity between the symbol and what it represents . another example of that is the plus sign for addition , which originated from a condensing of the latin word et meaning and . sometimes , however , the choice of symbol is more arbitrary , such as when a mathematician named christian kramp introduced the exclamation mark for factorials just because he needed a shorthand for expressions like this . in fact , all of these symbols were invented or adopted by mathematicians who wanted to avoid repeating themselves or having to use a lot of words to write out mathematical ideas . many of the symbols used in mathematics are letters , usually from the latin alphabet or greek . characters are often found representing quantities that are unknown , and the relationships between variables . they also stand in for specific numbers that show up frequently but would be cumbersome or impossible to fully write out in decimal form . sets of numbers and whole equations can be represented with letters , too . other symbols are used to represent operations . some of these are especially valuable as shorthand because they condense repeated operations into a single expression . the repeated addition of the same number is abbreviated with a multiplication sign so it does n't take up more space than it has to . a number multiplied by itself is indicated with an exponent that tells you how many times to repeat the operation . and a long string of sequential terms added together is collapsed into a capital sigma . these symbols shorten lengthy calculations to smaller terms that are much easier to manipulate . symbols can also provide succinct instructions about how to perform calculations . consider the following set of operations on a number . take some number that you 're thinking of , multiply it by two , subtract one from the result , multiply the result of that by itself , divide the result of that by three , and then add one to get the final output . without our symbols and conventions , we 'd be faced with this block of text . with them , we have a compact , elegant expression . sometimes , as with equals , these symbols communicate meaning through form . many , however , are arbitrary . understanding them is a matter of memorizing what they mean and applying them in different contexts until they stick , as with any language . if we were to encounter an alien civilization , they 'd probably have a totally different set of symbols . but if they think anything like us , they 'd probably have symbols . and their symbols may even correspond directly to ours . they 'd have their own multiplication sign , symbol for pi , and , of course , equals .
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with them , we have a compact , elegant expression . sometimes , as with equals , these symbols communicate meaning through form . many , however , are arbitrary .
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the meaning of mathematical symbols is
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in the summer of 1976 , a mysterious epidemic suddenly struck two central african towns , killing the majority of its victims . medical researchers suspected the deadly marburg virus to be the culprit . but what they saw in microscope images was an entirely new pathogen , which would be named after the nearby ebola river . like yellow fever or dengue , the disease caused by the ebola virus is a severe type of hemorrhagic fever . it begins by attacking the immune system 's cells and neutralizing its responses , allowing the virus to proliferate . starting anywhere from two to twenty days after contraction , initial symptoms like high temperature , aching , and sore throat resemble those of a typical flu , but quickly escalate to vomiting , rashes , and diarrhea . and as the virus spreads , it invades the lymph nodes and vital organs , such as kidneys and liver , causing them to lose function . but the virus itself is not what kills ebola victims . instead , the mounting cell deaths trigger an immune system overload , known as a cytokine storm , an explosion of immune responses that damages blood vessels , causing both internal and external bleeding . the excessive fluid loss and resulting complications can be fatal within six to sixteen days of the first symptoms , though proper care and rehydration therapy can significantly reduce mortality rates in patients . fortunately , while ebola is highly virulent , several factors limit its contagiousness . unlike viruses that proliferate through small , airborne particles , ebola only exists in bodily fluids , such as saliva , blood , mucus , vomit , or feces . in order to spread , these must be transmitted from an infected person into another 's body through passageways such as the eyes , mouth , or nose . and because the disease 's severity increases directly along with the viral load , even an infected person is unlikely to be contagious until they have begun to show symptoms . while ebola has been shown to survive on surfaces for several hours , and transmission through sneezing or coughing is theoretically possible , virtually all known cases of contraction have been through direct contact with the severely ill , with the greatest risk posed to medical workers and friends or relatives of the victims . this is why , despite its horrifying effects , ebola has been far less deadly overall than more common infections , such as measles , malaria , or even influenza . once an outbreak has been contained , the virus does not exist in the human population until the next outbreak begins . but while this is undoubtedly a good thing , it also makes ebola difficult to study . scientists believe fruit bats to be its natural carriers , but just how it is transmitted to humans remains unknown . furthermore , many of the countries where ebola outbreaks occur suffer from poor infrastructure and sanitation , which enables the disease to spread . and the poverty of these regions , combined with the relatively low amount of overall cases means there is little economic incentive for drug companies to invest in research . though some experimental medicines have shown promise , and governments are funding development of a vaccine , as of 2014 , the only widespread and effective solutions to an ebola outbreak remain isolation , sanitation , and information .
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and as the virus spreads , it invades the lymph nodes and vital organs , such as kidneys and liver , causing them to lose function . but the virus itself is not what kills ebola victims . instead , the mounting cell deaths trigger an immune system overload , known as a cytokine storm , an explosion of immune responses that damages blood vessels , causing both internal and external bleeding .
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how does the deadliness of the ebola virus actually make it less dangerous ?
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translator : ido dekkers reviewer : emma gon ( music ) every movie you 've ever seen , every tv show , every magazine , every time you surf the internet , you 're absorbing information , a bit like a sponge absorbs water . the words on the screen , the images , the colors , the sounds , the angle of the camera , every detail is designed to make you think , act or feel a certain way . your brain is subconsciously decoding images and sounds , and just by being alive today , by interacting with and reading all these different types of media , you 're already an expert at decoding and understanding these hidden messages . a set of codes and conventions that work together to make you feel happy , angry , afraid , excited . to make you want to buy a particular product -- a refreshing drink , a new phone . to style your hair a certain way . to cheer for the hero or boo the villain . welcome to the family tree of technical codes . so what constitutes a code ? first of all , it has to be recognized by all who read it . imagine a busy city where motorists do n't know how to read the traffic signals . we all have to know red equals stop , green means go , for the system to work . otherwise it would be chaos . secondly , codes are made meaningful by their context . we ca n't fully interpret or decipher a code until we see how it relates to other signs and symbols . look at these two intersecting lines . without any context , things around the code to help you understand or make meaning from it , it 's hard to know exactly what these lines represent . they could be a cross , symbolizing religion , an add sign , symbolizing a mathematical concept , the letter t from the alphabet , or they could just be two lines intersecting . if we add a crescent moon shape , and a circle with a line on it in front , the two lines now have a context , a relationship to their surroundings , and are magically revealed as the letter t. by adding additional information around the code , we 've changed its context , and therefore given it a concrete meaning . let 's meet the family . technical codes , senior has three sons : symbolic codes , written codes and technical codes , junior . symbolic codes has three sons : symbolic color , symbolic objects and symbolic animals . this branch of the family is all about representation . red represents hot or stop or danger , depending on its context . so if you see a red light above a yellow and a green light on a pole above the road , you know by this context that the light represents stop . written codes has three sons : you and only you , buzzwords and catchphrase . these guys are all about saying a lot with a little , or planting a word in your subconscious that triggers a response whenever you hear or read it . have you noticed how many times i 've said the word `` you ? '' you should feel like it 's directed specifically at you , and only you , that it 's addressing your needs and desire to learn about your world . if i tell you that all the cool , fresh and hip people are buying a new drink or wearing a particular brand , the buzzwords `` new , '' `` fresh '' or `` free '' make the product seem more interesting and appealing . if i wrap that product or idea in a simple phrase that 's easy to remember and becomes part of your everyday speech , then every time you hear or say those few words , your brain connects them to the product . so just do it , think different , and enjoy the power of the catchphrase . and technical codes , junior has three sons : camera angles , framing and lighting . for these boys , it 's all about how the camera is placed , how objects , people and places are shot , and what we see on screen -- or just as importantly , what we do n't see . when the camera is placed high above the subject , it makes you look small , insignificant and powerless . and the reverse is also true , when the camera is below . so is this video trying to manipulate you to buy something ? yes , an idea . the idea that understanding the relationship between technical codes and the role they play in shaping your understanding of the world around us through the media we consume is fun and interesting . is it trying to make you feel a certain way ? absolutely . every image , every word , has been carefully crafted to work together to make you feel positive about the idea that you need to be educated to engage with what you read , watch and listen to in movies , tv shows , magazines and on the internet . by understanding these codes , and how they work together to subconsciously change the way you think , feel and act towards products and ideas , you 'll be aware of these techniques and able to identify their impact on you . one of the most powerful advertising mediums in the world is word of mouth . if you 've ever recommended a product or movie , a service , or even a video online , then you 've played your part in passing the message . so soak all this information up . recognize how the family tree of technical codes works on you , and those around you , to make an impact find excellent examples , and spread the word .
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by understanding these codes , and how they work together to subconsciously change the way you think , feel and act towards products and ideas , you 'll be aware of these techniques and able to identify their impact on you . one of the most powerful advertising mediums in the world is word of mouth . if you 've ever recommended a product or movie , a service , or even a video online , then you 've played your part in passing the message .
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according to beaton , one of the most powerful advertising mediums in the world is :
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thallium , because it is heavier , has two different so-called oxidation states . it can react with one atom of chlorine per thallium , or say three , and the different chemistry between thallium-one and thallium-three . thallium salts are very poisonous , and there was quite a notorious case some years ago when a technician at some company , who turned out to be mad , was discovered to have been poisoning many of his colleagues with thallium and so , but it is not a widely used element , apart from a few materials that are used . there is a rather nice red material that is made of thallium , which has the rather unromantic name of krs-5 , this is mixed bromide and iodine with thallium which is used as windows for many infrared experiments . but because thallium is so poisonous , one has to be quite careful about handling .
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thallium , because it is heavier , has two different so-called oxidation states . it can react with one atom of chlorine per thallium , or say three , and the different chemistry between thallium-one and thallium-three . thallium salts are very poisonous , and there was quite a notorious case some years ago when a technician at some company , who turned out to be mad , was discovered to have been poisoning many of his colleagues with thallium and so , but it is not a widely used element , apart from a few materials that are used .
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only one of these sentences comparing thallium and gold is correct . which one is it ?
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in the early days of organic chemistry , chemists understood that molecules were made of atoms connected through chemical bonds . however , the three-dimensional shapes of molecules were utterly unclear , since they could n't be observed directly . molecules were represented using simple connectivity graphs like the one you see here . it was clear to savvy chemists of the mid-19th century that these flat representations could n't explain many of their observations . but chemical theory had n't provided a satisfactory explanation for the three-dimensional structures of molecules . in 1874 , the chemist va n't hoff published a remarkable hypothesis : the four bonds of a saturated carbon atom point to the corners of a tetrahedron . it would take over 25 years for the quantum revolution to theoretically validate his hypothesis . but va n't hoff supported his theory using optical rotation . va n't hoff noticed that only compounds containing a central carbon bound to four different atoms or groups rotated plane-polarized light . clearly there 's something unique about this class of compounds . take a look at the two molecules you see here . each one is characterized by a central , tetrahedral carbon atom bound to four different atoms : bromine , chlorine , fluorine , and hydrogen . we might be tempted to conclude that the two molecules are the same , if we just concern ourselves with what they 're made of . however , let 's see if we can overlay the two molecules perfectly to really prove that they 're the same . we have free license to rotate and translate both of the molecules as we wish . remarkably though , no matter how we move the molecules , we find that perfect superposition is impossible to achieve . now take a look at your hands . notice that your two hands have all the same parts : a thumb , fingers , a palm , etc . like our two molecules under study , both of your hands are made of the same stuff . furthermore , the distances between stuff in both of your hands are the same . the index finger is next to the middle finger , which is next to the ring finger , etc . the same is true of our hypothetical molecules . all of their internal distances are the same . despite the similarities between them , your hands , and our molecules , are certainly not the same . try superimposing your hands on one another . just like our molecules from before , you 'll find that it ca n't be done perfectly . now , point your palms toward one another . wiggle both of your index fingers . notice that your left hand looks as if it 's looking in a mirror at your right . in other words , your hands are mirror images . the same can be said of our molecules . we can turn them so that one looks at the other as in a mirror . your hands - and our molecules - possess a spatial property in common called chirality , or handedness . chirality means exactly what we 've just described : a chiral object is not the same as its mirror image . chiral objects are very special in both chemistry and everyday life . screws , for example , are also chiral . that 's why we need the terms right-handed and left-handed screws . and believe it or not , certain types of light can behave like chiral screws . packed into every linear , plane-polarized beam of light are right-handed and left-handed parts that rotate together to produce plane polarization . chiral molecules , placed in a beam of such light , interact differently with the two chiral components . as a result , one component of the light gets temporarily slowed down relative to the other . the effect on the light beam is a rotation of its plane from the original one , otherwise known as optical rotation . va n't hoff and later chemists realized that the chiral nature of tetrahedral carbons can explain this fascinating phenomenon . chirality is responsible for all kinds of other fascinating effects in chemistry , and everyday life . humans tend to love symmetry and so if you look around you , you 'll find that chiral objects made by humans are rare . but chiral molecules are absolutely everywhere . phenomena as separate as optical rotation , screwing together furniture , and clapping your hands all involve this intriguing spatial property .
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it would take over 25 years for the quantum revolution to theoretically validate his hypothesis . but va n't hoff supported his theory using optical rotation . va n't hoff noticed that only compounds containing a central carbon bound to four different atoms or groups rotated plane-polarized light . clearly there 's something unique about this class of compounds .
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to support his theory concerning the geometry of saturated carbon atoms , van ’ t hoff used the phenomenon of
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every spring , hundreds of adventure-seekers dream of climbing qomolangma , also known as mount everest . at base camp , they hunker down for months waiting for the chance to scale the mountain 's lofty , lethal peak . but why do people risk life and limb to climb everest ? is it the challenge ? the view ? the chance to touch the sky ? for many , the draw is everest 's status as the highest mountain on earth . there 's an important distinction to make here . mauna kea is actually the tallest from base to summit , but at 8850 meters above sea level , everest has the highest altitude on the planet . to understand how this towering formation was born , we have to peer deep into our planet 's crust , where continental plates collide . the earth 's surface is like an armadillo 's armor . pieces of crust constantly move over , under , and around each other . for such huge continental plates , the motion is relatively quick . they move two to four centimeters per year , about as fast as fingernails grow . when two plates collide , one pushes into or underneath the other , buckling at the margins , and causing what 's known as uplift to accomodate the extra crust . that 's how everest came about . 50 million years ago , the earth 's indian plate drifted north , bumped into the bigger eurasian plate , and the crust crumpled , creating huge uplift . mountain everest lies at the heart of this action , on the edge of the indian-eurasian collision zone . but mountains are shaped by forces other than uplift . as the land is pushed up , air masses are forced to rise as well . rising air cools , causing any water vapor within it to condense and form rain or snow . as that falls , it wears down the landscape , dissolving rocks or breaking them down in a process known as weathering . water moving downhill carries the weathered material and erodes the landscape , carving out deep valleys and jagged peaks . this balance between uplift and erosion gives a mountain its shape . but compare the celestial peaks of the himalayas to the comforting hills of appalachia . clearly , all mountains are not alike . that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast . the peaks grow tall with steep slopes . over time , however , gravity and water wear them down . eventually , erosion overtakes uplift , wearing down peaks faster than they 're pushed up . a third factor shapes mountains : climate . in subzero temperatures , some snowfall does n't completely melt away , instead slowly compacting until it becomes ice . that forms the snowline , which occurs at different heights around the planet depending on climate . at the freezing poles , the snowline is at sea level . near the equator , you have to climb five kilometers before it gets cold enough for ice to form . gathered ice starts flowing under its own immense weight forming a slow-moving frozen river known as a glacier , which grinds the rocks below . the steeper the mountains , the faster ice flows , and the quicker it carves the underlying rock . glaciers can erode landscapes swifter than rain and rivers . where glaciers cling to mountain peaks , they sand them down so fast , they lop the tops off like giant snowy buzzsaws . so then , how did the icy mount everest come to be so tall ? the cataclysmic continental clash from which it arose made it huge to begin with . secondly , the mountain lies near the tropics , so the snowline is high , and the glaciers relatively small , barely big enough to widdle it down . the mountain exists in a perfect storm of conditions that maintain its impressive stature . but that wo n't always be the case . we live in a changing world where the continental plates , earth 's climate , and the planet 's erosive power might one day conspire to cut mount everest down to size . for now , at least , it remains legendary in the minds of hikers , adventurers , and dreamers alike .
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where glaciers cling to mountain peaks , they sand them down so fast , they lop the tops off like giant snowy buzzsaws . so then , how did the icy mount everest come to be so tall ? the cataclysmic continental clash from which it arose made it huge to begin with .
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mount everest is :
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between the first europeans arriving in 1492 and the victorian age , the indigenous population of the new world dropped by at least 90 % . the cause ? not the conquistadors and company -- they killed lots of people but their death count is nothing compared to what they brought with them : small pox , typhus , tuberculosis , influenza , bubonic plague , cholera , mumps , measles and more leapt from those first explorers to the costal tribes , then onward the microscopic invaders spread through a hemisphere of people with no defenses against them . tens of millions died . these germs decided the fate of these battles long before the fighting started . now ask yourself : why did n't the europeans get sick ? if new-worlders were vulnerable to old-world diseases , then surely old-worlders would be vulnerable to new world diseases . yet , there was no americapox spreading eastward infecting europe and cutting the population from 90 million to 9 . had americapox existed it would have rather dampened european ability for transatlantic expansion . to answer why this did n't happen : we need first to distinguish regular diseases -- like the common cold -- from what we 'll call plagues . 1 . spread quickly between people . sneezes spread plagues faster than handshakes which are faster than closeness . plagues use more of this than this . 2 . they kill you quickly or you become immune . catch a plague and you 're dead within seven to thirty days ; survive and you 'll never get it again . your body has learned to fight it . you might still carry it -- the plague lives in you , you can still spread it -- but it ca n't hurt you . the surface answer to this question is n't that europeans had better immune systems to fight off new world plagues -- it 's that the new world did n't have plagues for them to catch . they had regular diseases but there was no americapox to carry . these are history 's biggest killers , and they all come from the old world . but why ? let 's dig deeper , and talk cholera : a plague that spreads if your civilization does a bad job of separating drinking water from pooping water . london was terrible at this , making it the cholera capital of the world . cholera can rip through dense neighborhoods , killing swaths of the population before moving onward . but that 's the key : it has to move on . in a small , isolated group , a plague like cholera can not survive -- it kills all available victims , leaving only the immune and then theres nowhere to go -- it 's a fire that burns through its fuel . but a city -- shining city on the hill -- to which rural migrants flock , where hundreds of babies are born a day : this is sanctuary for the fire of plague ; fresh kindling comes to it . the plague flares and smolders and flares and smolders again -- impossible to extinguish . historically , in city borders , plagues killed faster than people could breed . cities grew because more people moved to them than died inside of them . cities only started growing from their own population in the 1900s when medicine finally left its leaches and bloodletting phase and entered its soap and soup phase , giving humans some tools to slow death . but before that a city was an unintentional playground for plagues and a grim machine to sort the immune from the rest . so the deeper answer is that the new world did n't have plagues because the new world did n't have big , dense , terribly sanitized deeply interconnected cities for plagues to thrive . ok , but the new world was n't completely barren of cities , and tribes were n't completely isolated . otherwise the newly-arrived smallpox in the 1400s could n't have spread . cities are only part of the puzzle : they 're required for plagues , but cities do n't make the germs that start the plagues -- those germs come from the missing piece . now , most germs do n't want to kill you , for the same reason you do n't want to burn down your house ; germs live in you . chronic diseases like leprosy are terrible because they 're very good at living in you and not killing you . plague lethality is an accident , a misunderstanding , because the germs that cause them do n't know they 're in humans ; they think they 're in this . plagues come from animals . whooping cough comes from pigs , as does flu , as well as from birds . our friend the cow alone is responsible for measles , tuberculosis , and smallpox . for the cow these diseases are no big deal -- like colds for us . but when cow germs get in humans , the things they do to make a cow a little sick to spread make humans very sick . deadly sick . now , germs jumping species like this is extraordinarily rare . that 's why generations of humans can spend time around animals just fine . being the patient zero of a new animal-to-human plague is winning a terrible lottery . but a colonial-age city raises the odds : there used to be animals everywhere ; horses , herds of livestock in the streets , open slaughterhouses , meat markets pre-refrigeration , and rivers of human and animal excrement running through it all . a more perfect environment for diseases to jump species could hardly be imagined . so the deeper answer is that plagues come from animals , but so rarely that you have to raise the odds with many chances for infection and even then the new-born plague needs a fertile environment to grow . the old world had the necessary pieces in abundance . but why was a city like london filled with sheep and pigs and cows and tenochtitlan was n't ? this brings us to the final level , for this video anyway . some animals can be put to human use -- this is what domestication means : animals you can breed , not just hunt . forget for a the moment the modern world : go back to 10,000bc when tribes of humans reached just about everywhere . if you were in one of these tribes , what local animals could you capture , alive , and successfully pen to breed ? maybe you 're in north dakota and thinking about catching a buffalo : an unpredictable , violent tank on hooves , that can outrun you across the planes , leap over your head and travels in herds thousands strong . oh , and you have no horses to help you -- because there are no horses on the continent . horses live here -- and wo n't be brought over until too late . it 's just you , a couple buddies , and stone-based tools . american indians did n't fail to domesticate buffalo because they could n't figure it out . they failed because it 's a buffalo . no one could do it -- buffalo would have been amazing creatures to put to human work back in bc , but it 's not going to happen -- humans have only barely domesticated buffalo with all our modern tools . the new world did n't have good animal candidates for domestication . almost everything big enough to be useful is also too dangerous , or too agile . meanwhile the fertile crescent to central europe had cows and pigs and sheep and goats : easy-peasy animals comparatively begging to be domesticated . a wild boar is something to contend with if you only have stone tools but it 's possible to catch and pen and breed and feed to eat -- because pigs ca n't leap to the sky or crush all resistance beneath their hooves . in the new world the only native domestication contestant was : llamas . they 're better than nothing -- which is probably why the biggest cities existed in south america -- but they 're no cow . ever try to manage a heard of llamas in the mountains of peru ? yeah , you can do it , but it 's not fun . nothing but drama , these llamas . these might seem , cherry-picked examples , because are n't there hundreds of thousands of species of animals ? yes , but when you 're stuck at the bottom of the tech tree , almost none of them can be domesticated . from the dawn of man until this fateful meeting , humans domesticated ; maybe a baker 's dozen of unique species the world over . and even to get that high a number you need to stretch it to include honeybees and silkworms ; nice to have , but you ca n't build a civilization on a foundation of honey alone . these early tribes were n't smarter , or better at domestication . the old world had more valuable and easy animals . with dogs , herding sheep and cattle is easier . now humans have a buddy to keep an eye on the clothing factory , and the milk and cheeseburger machine , and the plow-puller . now farming is easier , which means there 's more benefit to staying put , which means more domestication , which means more food which means more people and more density and oh look where we 're going . citiesville : population : lots ; bring your animals ; plagues welcome . that is the full answer : the lack of new world animals to domesticate limited not only exposure to germs sources but also limited food production , which limited population growth , which limited cities , which made plagues in the new world an almost impossibility . in the old [ world ] , exactly the reverse , and thus a continent full of plague and a continent devoid of it . so when ships landed in the new world , there was no americapox to bring back . the game of civilization has nothing to do with the players , and everything to do with the map . access to domesticated animals in numbers and diversity is the key resource to bootstrapping a complex society from nothing -- and that complexity brings with it , unintentionally , a passive biological weaponry devastating to outsiders . start the game again but move the domesticable animals across the sea and history 's arrow of disease and death flows in the opposite direction . this still does leave one last question . just why are some animals domesticable and others not ? why could n't american indians domesticate deer ? why ca n't zebras be domesticated ? they look just like horses . and what does it mean to tame an animal ? to answer that , click here for part 2 . this video has been brought to you by audible.com and was a presentation of diamond 's theory as laid out in his book gun , germs and steel . if you found this video interesting you should go right now to audible.com/grey and get a copy of the book . there is so much more in this than could ever been explained in a short video -- guns , germs and steel is the history book to rule all history books . audible has over 180,000 things for you to listen to . it is an endless source of interestingness . so once again , please to go audible.com/grey get a 30-day free trial and let them know that you came from this channel . audiobooks are a big part of my life and i think they should be a big part of your life . why not get started today ?
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plagues use more of this than this . 2 . they kill you quickly or you become immune .
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name at least 2 of the 3 key ingredients that can create a plague .
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every day of your life , you move through systems of power that other people made . do you sense them ? do you understand power ? do you realize why it matters ? power is something we are often uncomfortable talking about . that 's especially true in civic life , how we live together in community . in a democracy , power is supposed to reside with the people , period . any further talk about power and who really has it seems a little dirty , maybe even evil . but power is no more inherently good or evil than fire or physics . it just is . it governs how any form of government works . it determines who gets to determine the rules of the game . so learning how power operates is key to being effective , being taken seriously , and not being taken advantage of . in this lesson , we 'll look at where power comes from , how it 's exercised and what you can do to become more powerful in public life . let 's start with a basic definition . power is the ability to make others do what you would have them do . of course , this plays out in all arenas of life , from family to the workplace to our relationships . our focus is on the civic arena , where power means getting a community to make the choices and to take the actions that you want . there are six main sources of civic power . first , there 's physical force and a capacity for violence . control of the means of force , whether in the police or a militia , is power at its most primal . a second core source of power is wealth . money creates the ability to buy results and to buy almost any other kind of power . the third form of power is state action , government . this is the use of law and bureaucracy to compel people to do or not do certain things . in a democracy , for example , we the people , theoretically , give government its power through elections . in a dictatorship , state power emerges from the threat of force , not the consent of the governed . the fourth type of power is social norms or what other people think is okay . norms do n't have the centralized machinery of government . they operate in a softer way , peer to peer . they can certainly make people change behavior and even change laws . think about how norms around marriage equality today are evolving . the fifth form of power is ideas . an idea , individual liberties , say , or racial equality , can generate boundless amounts of power if it motivates enough people to change their thinking and actions . and so the sixth source of power is numbers , lots of humans . a vocal mass of people creates power by expressing collective intensity of interest and by asserting legitimacy . think of the arab spring or the rise of the tea party . crowds count . these are the six main sources of power , what power is . so now , let 's think about how power operates . there are three laws of power worth examining . law number one : power is never static . it 's always either accumulating or decaying in a civic arena . so if you are n't taking action , you 're being acted upon . law number two : power is like water . it flows like a current through everyday life . politics is the work of harnessing that flow in a direction you prefer . policymaking is an effort to freeze and perpetuate a particular flow of power . policy is power frozen . law number three : power compounds . power begets more power , and so does powerlessness . the only thing that keeps law number three from leading to a situation where only one person has all the power is how we apply laws one and two . what rules do we set up so that a few people do n't accumulate too much power , and so that they ca n't enshrine their privilege in policy ? that 's the question of democracy , and you can see each of these laws at work in any news story . low wage workers organize to get higher pay . oil companies push to get a big pipeline approved . gay and lesbian couples seek the legal right to marry . urban parents demand school vouchers . you may support these efforts or not . whether you get what you want depends on how adept you are with power , which brings us finally to what you can do to become more powerful in public life . here , it 's useful to think in terms of literacy . your challenge is to learn how to read power and write power . to read power means to pay attention to as many texts of power as you can . i do n't mean books only . i mean seeing society as a set of texts . do n't like how things are in your campus or city or country ? map out who has what kind of power , arrayed in what systems . understand why it turned out this way , who 's made it so , and who wants to keep it so . study the strategies others in such situations used : frontal attack or indirection , coalitions or charismatic authority . read so you may write . to write power requires first that you believe you have the right to write , to be an author of change . you do . as with any kind of writing , you learn to express yourself , speak up in a voice that 's authentic . organize your ideas , then organize other people . practice consensus building . practice conflict . as with writing , it 's all about practice . every day you have a chance to practice , in your neighborhood and beyond . set objectives , then bigger ones . watch the patterns , see what works . adapt , repeat . this is citizenship . in this short lesson , we 've explored where civic power comes from , how it works and what you can do to exercise it . one big question remaining is the `` why '' of power . do you want power to benefit everyone or only you ? are your purposes pro-social or anti-social ? this question is n't about strategy . it 's about character , and that 's another set of lessons . but remember this : power plus character equals a great citizen , and you have the power to be one .
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you do . as with any kind of writing , you learn to express yourself , speak up in a voice that 's authentic . organize your ideas , then organize other people . practice consensus building . practice conflict . as with writing , it 's all about practice .
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speaking up in an authentic voice , organizing your ideas and people , practicing consensus and conflict skills , and adapting are all part of :
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berkelium which , i assume was named after the place of its discovery , which was berkeley and they made 3 billionths of a gram of it , which was just enough to record some spectroscopic data on it and prove that they had actually made it .
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berkelium which , i assume was named after the place of its discovery , which was berkeley and they made 3 billionths of a gram of it , which was just enough to record some spectroscopic data on it and prove that they had actually made it .
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berkelium was named after…
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think about all the things that need to happen for a human settlement to thrive : obtaining food , building shelter , raising children and more . there needs to be a way to divide resources , organize major efforts and distribute labor efficiently . now imagine having to do this without any sort of planning or higher level communication . welcome to the ant colony . ants have some of the most complex social organization in the animal kingdom , living in structured colonies containing different types of members who perform specific roles . but although this may sound similar to some human societies , this organization does n't arise from any higher level decisions , but is part of a biologically programmed cycle . in many species , all the winged males and winged virgin queens from all the nearby colonies in the population each leave from their different nests and meet at a central place to mate , using pheromones to guide each other to a breeding ground . after mating , the males die off , while females try to establish a new colony . the few that are successful settle down in a suitable spot , lose their wings , and begin laying eggs , selectively fertilizing some using stored sperm they 've saved up from mating . fertilized eggs grow into female workers who care for the queen and her eggs . they will then defend the colony and forage for food , while unfertilized eggs grow into males whose only job is to wait until they are ready to leave the nest and reproduce , beginning the cycle again . so how do worker ants decide what to do and when ? well , they do n't really . although they have no methods of intentional communication , individual ants do interact with one another through touch , sound and chemical signals . these stimuli accomplish many things from serving as an alarm to other ants if one is killed , to signaling when a queen is nearing the end of her reproductive life . but one of the most impressive collective capabilities of an ant colony is to thoroughly and efficiently explore large areas without any predetermined plan . most species of ants have little or no sense of sight and can only smell things in their vicinity . combined with their lack of high level coordination , this would seem to make them terrible explorers , but there is an amazingly simple way that ants maximize their searching efficiency ; by changing their movement patterns based on individual interactions . when two ants meet , they sense each other by touching antennae . if there are many ants in a small area this will happen more often causing them to respond by moving in more convoluted , random paths in order to search more thoroughly . but in a larger area , with less ants , where such meetings happen less often , they can walk in straight lines to cover more ground . while exploring their environment in this way , an ant may come across any number of things , from threats or enemies , to alternate nesting sites . and some species have another capability known as recruitment . when one of these ants happens to find food , it will return with it , marking its path with a chemical scent . other ants will then follow this pheromone trail , renewing it each time they manage to find food and return . once the food in that spot is depleted , the ants stop marking their return . the scent dissipates and ants are no longer attracted to that path . these seemingly crude methods of search and retrieval are , in fact , so useful that they are applied in computer models to obtain optimal solutions from decentralized elements , working randomly and exchanging simple information . this has many theoretical and practical applications , from solving the famous traveling salesman problem , to scheduling computing tasks and optimizing internet searches , to enabling groups of robots to search a minefield or a burning building collectively , without any central control . but you can observe these fascinatingly simple , yet effective , processes directly through some simple experiments , by allowing ants to enter empty spaces of various sizes and paying attention to their behavior . ants may not be able to vote , hold meetings or even make any plans , but we humans may still be able to learn something from the way that such simple creatures are able to function so effectively in such complex ways .
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now imagine having to do this without any sort of planning or higher level communication . welcome to the ant colony . ants have some of the most complex social organization in the animal kingdom , living in structured colonies containing different types of members who perform specific roles .
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why have different ant species evolved to search differently , depending on the environment they are in ?
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when reverend jim jones founded the peoples temple in 1955 , few could have imagined its horrifying end . this progressive religious movement rose in popularity and gained support from some of san francisco 's most prominent politicians . but in 1977 , amidst revelations of brainwashing and abuse , jones moved with several hundred followers to establish the commune of jonestown in guyana . billed as a utopian paradise , the colony was more like a prison camp , and when a congressional delegation arrived to investigate its conditions , jones executed his final plan . on november 18 , 1978 , 909 men , women , and children died after being forced to drink poisoned flavor aid . that grizzly image has since been immortalized as shorthand slang for single-minded cult-like thinking , `` they drank the kool-aid . '' today , there are thousands of cults around the world . it 's important to note two things about them . first , not all cults are religious . some are political , therapy-based , focused on self-improvement , or otherwise . and on the flip side , not all new religions are what we 're referring to as cults . so what exactly defines our modern understanding of cults , and why do people join them ? broadly speaking , a cult is a group or movement with a shared commitment to a usually extreme ideology that 's typically embodied in a charismatic leader . and while few turn out as deadly as jonestown or heaven 's gate , which ended in a mass suicide of 39 people in 1997 , most cults share some basic characteristics . a typical cult requires a high level of commitment from its members and maintains a strict hierarchy , separating unsuspecting supporters and recruits from the inner workings . it claims to provide answers to life 's biggest questions through its doctrine , along with the required recipe for change that shapes a new member into a true believer . and most importantly , it uses both formal and informal systems of influence and control to keep members obedient , with little tolerance for internal disagreement or external scrutiny . you might wonder whether some of these descriptions might also apply to established religions . in fact , the world `` cultus '' originally described people who cultivated the worship of certain gods by performing rituals and maintaining temples . but in time , it came to mean excessive devotion . many religions began as cults , but integrated into the fabric of the larger society as they grew . a modern cult , by contrast , separates its members from others . rather than providing guidelines for members to live better lives , a cult seeks to directly control them , from personal and family relationships , to financial assets and living arrangements . cults also demand obedience to human leaders who tend to be highly persuasive people with authoritarian and narcissistic streaks motivated by money , sex , power , or all three . while a cult leader uses personal charisma to attract initial followers , further expansion works like a pyramid scheme , with early members recruiting new ones . cults are skilled at knowing whom to target , often focusing on those new to an area , or who have recently undergone some personal or professional loss . loneliness and a desire for meaning make one susceptible to friendly people offering community . the recruitment process can be subtle , sometimes taking months to establish a relationship . in fact , more than two-thirds of cult members are recruited by a friend , family member , or co-worker whose invitations are harder to refuse . once in the cult , members are subjected to multiple forms of indoctrination . some play on our natural inclination to mimic social behaviors or follow orders . other methods may be more intense using techniques of coercive persuasion involving guilt , shame , and fear . and in many cases , members may willingly submit out of desire to belong and to attain the promised rewards . the cult environment discourages critical thinking , making it hard to voice doubts when everyone around you is modeling absolute faith . the resulting internal conflict , known as cognitive dissonance , keeps you trapped , as each compromise makes it more painful to admit you 've been deceived . and though most cults do n't lead members to their death , they can still be harmful . by denying basic freedoms of thought , speech , and association , cults stunt their members ' psychological and emotional growth , a particular problem for children , who are deprived of normal developmental activities and milestones . nevertheless , many cult members eventually find a way out , whether through their own realizations , the help of family and friends , or when the cult falls apart due to external pressure or scandals . many cults may be hard to identify , and for some , their beliefs , no matter how strange , are protected under religious freedom . but when their practices involve harassment , threats , illegal activities , or abuse , the law can intervene . believing in something should not come at the cost of your family and friends , and if someone tells you to sacrifice your relationships or morality for the greater good , they 're most likely exploiting you for their own .
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by denying basic freedoms of thought , speech , and association , cults stunt their members ' psychological and emotional growth , a particular problem for children , who are deprived of normal developmental activities and milestones . nevertheless , many cult members eventually find a way out , whether through their own realizations , the help of family and friends , or when the cult falls apart due to external pressure or scandals . many cults may be hard to identify , and for some , their beliefs , no matter how strange , are protected under religious freedom .
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one characteristic of a cult is :
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vatican city : capitol of the catholic church , home to the pope , owner of impressive collections of art and history all contained within the borders of the world 's smallest country : conveniently circumnavigateable on foot in only 40 minutes . just how did the world end up with this tiny nation ? the short answer is : because mussolini and the long answer is fiendishly complicated so here 's a simplified medium version : the popes used to rule a country called the papal states that covered much of modern day italy . it was during this 1,000+ year reign that the popes constructed st. peter 's basilica the largest church in the world -- and also built a wall around the base of a hill known as vatican upon which st. peter 's stood . but the kingdom of italy next door thought rome would be an awesome capital for their country and so conquered the papal states . his nation destroyed the pope hid behind the walls of vatican and conflictingly refused to acknowledge that the kingdom of italy existed , while simultaneously complaining about being a prisoner of the kingdom of italy -- which according to him did n't exist . rather than risk religious civil war by getting rid of the pope the kingdom of italy decided to wait him out assuming he 'd eventually give up -- but religion is nothing if not obstinate -- and 1 , 2 , 3 , 4 , 5 popes and sixty years later nothing had changed . which brings us to benito mussolini the then prime minister of italy who was tired of listing to the pope complain to italian catholics about his self-imposed imprisonment so mussolini thought he could score some political points by striking a deal which looked like this : 1 ) italy gave the land of vatican to the pope . and… 2 ) italy gave the pope a bunch of apology money in return 1 ) the pope acknowledged that italy existed and and… 2 ) the pope promised to remain neutral in politics and wars . on the off chance that , you know , mussolini thought this might be a thing . the deal was signed and a new country , vatican city was born . and today the tiny nation on a hill has all the things you 'd expect of a country : its own government that makes its own laws that are enforced by its own police , who put people who break them in its own jail . it also has its own bank and prints its own stamps and issues its own license plates , though only its citizens can drive within its borders presumably because of terrible , terrible parking -- and as the true mark of any self-respecting nation : it has its own top-level domain : .va but , despite all these national trappings vatican city is not really like any other country . hold on to your fancy hat , because it 's about to get weird : to understand the vatican : there are two people and two things that you need to know about : the famous pope , the incredibly confusing holy see , the country of vatican city and along with that the almost completely unknown king of vatican city . but first the pope : who gets a throne to sit upon and from which he acts as the bishop for all the catholics in rome . actually all bishops in the catholic church get their own thrones but because the bishop of rome is also the pope his thrown is special and has it 's own special name : the holy see . every time a pope dies or retires there is a sort of game of thrones to see which of the bishops will next get to occupy the holy see . so while popes come and go the throne is eternal . as such the name the holy see not only refers to the throne but also all the rules that make the catholic church the catholic church . when mussolini crafted that aforementioned deal , technically he gave the land of vatican city to the holy see -- which , believe it or not , is a legal corporate person in international law . basically every time you hear the words the holy see think catholic church , inc of which the pope is the ceo . now back to the king . the king of vatican city has absolute , unchecked power within the country 's borders and his presence makes vatican city one of only six remanning absolute monarchies in the world , including brunei , oman , qatar , saudi arabia , and swaziland . the king 's absolute power is why vatican city ca n't join the european union because only democracies are allowed . through vatican city does , strictly speaking , have a legislative brach of government -- staffed by cardinals , appointed by the pope -- the king of vatican city can overrule their decisions and at any time for any reason . so why do you never hear about the king of vatican city ? because though king and pope are two different roles , they just happen to be occupied by the same person at the same time -- which has the funny consequence that , because the pope is elected and the king is all-powerful but they 're the same guy it makes vatican city the world 's only elected , non-hereditary absolute monarchy . it 's this dual-role that makes untangling vatican city so difficult because the pope , depending on the situation either acts as the king of the country of vatican city or the pope of the holy see . got it ? no ? ok , here 's an analogy : imagine if a powerful international company , say grey industries , had a ceo who convinced the united states to give one of its islands to the company which then made the island into a new country -- greytropolis -- with an absolute monarchy as its government and the law that the king of greytropolis is , by definition , the ceo of grey industries . it 's pretty obvious at that point that the ceo should move his corporate headquarters to the new nation -- so that the laws of the country can benefit the company and the company 's global reach can benefit the country . as for the man in the middle sometimes it 's good to the the ceo and sometimes it 's good to be the king . that is essentially vatican city . but if you 're still confused , do n't worry even other countries ca n't keep it straight . for example the united nations has the holy see the corporation as a member but not vatican city the actual country . and the holy see gives passports to vatican city citizens that other countries accept even though those passports come from a company , not a country . and speaking of vatican city citizens , they are perhaps the strangest consequence of the pope 's dual role as religious leader and monarch . while other countries mint new citizens with the ever popular process of human reproduction vatican city does not . no one in vatican city is born a citizen -- and that 's not just because , within a rounding error , there are no female vaticans . the only way to become a citizen is for the king of vatican city to appoint you as one . and the king only appoints you a citizen if you work for the pope -- who is also the king . and because the king is all-powerful your citizenship is at his whim . if you quit your job for the pope , the king -- who is also the pope -- will revoke your citizenship . these rules mean that vatican city does n't have a real permanent population to speak of : there are only about 500 full citizens -- which is fewer people that live in single skyscrapers in many countries -- and all these citizens work for the holy see as either cardinals or diplomats or the pope 's bodyguards or other catholic-related jobs . so it 's best to think of vatican city as a kind of sovereign corporate headquarters that grants temporary citizenship to its managers rather than a real city-state like singapore : which has a self-reproducing population of citizens engaged in a variety of economic activities both of which vatican city lacks . but in the end , the reason the world cares about vatican city is not because of the citizens within its walls but because of the billion members of its church outside those walls .
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while other countries mint new citizens with the ever popular process of human reproduction vatican city does not . no one in vatican city is born a citizen -- and that 's not just because , within a rounding error , there are no female vaticans . the only way to become a citizen is for the king of vatican city to appoint you as one . and the king only appoints you a citizen if you work for the pope -- who is also the king .
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explain how one could become a citizen of vatican city .
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shall i ask for a show of hands or a clapping of people in different generations ? i 'm interested in how many are three to 12 years old . ( laughter ) none , huh ? ( laughter ) all right . i 'm going to talk about dinosaurs . do you remember dinosaurs when you were that age ? ( applause ) dinosaurs are kind of funny , you know . ( laughter ) we 're going to kind of go in a different direction right now . i hope you all realize that . so i 'll just give you my message up front : try not to go extinct . ( laughter ) that 's it . ( laughter ) people ask me a lot -- in fact , one of the most asked questions i get is , why do children like dinosaurs so much ? what 's the fascination ? and i usually just say , `` well , dinosaurs were big , different and gone . '' they 're all gone . well that 's not true , but we 'll get to the goose in a minute . so that 's sort of the theme : big , different and gone . the title of my talk : shape-shifting dinosaurs : the cause of a premature extinction . now i assume that we remember dinosaurs . and there 's lots of different shapes . lots of different kinds . a long time ago , back in the early 1900s , museums were out looking for dinosaurs . they went out and gathered them up . and this is an interesting story . every museum wanted a little bigger or better one than anybody else had . so if the museum in toronto went out and collected a tyrannosaur , a big one , then the museum in ottawa wanted a bigger one , and a better one . and that happened for all museums . so everyone was out looking for all these bigger and better dinosaurs . and this was in the early 1900s . by about 1970 , some scientists were sitting around and they thought , `` what in the world -- look at these dinosaurs , they 're all big . where are all the little ones ? '' ( laughter ) and they thought about it and they even wrote papers about it : `` where are the little dinosaurs ? '' ( laughter ) well , go to a museum , you 'll see , see how many baby dinosaurs there are . people assumed -- and this was actually a problem -- people assumed that if they had little dinosaurs , if they had juvenile dinosaurs , they 'd be easy to identify . you 'd have a big dinosaur and a littler dinosaur . ( laughter ) but all they had were big dinosaurs . and it comes down to a couple of things . first off , scientists have egos , and scientists like to name dinosaurs . they like to name anything . everybody likes to have their own animal that they named . ( laughter ) and so every time they found something that looked a little different , they named it something different . and what happened , of course , is we ended up with a whole bunch of different dinosaurs . in 1975 , a light went on in somebody 's head . dr. peter dodson at the university of pennsylvania actually realized that dinosaurs grew kind of like birds do , which is different than the way reptiles grow . and in fact , he used the cassowary as an example . and it 's kind of cool -- if you look at the cassowary , or any of the birds that have crests on their heads , they grow to about 80 percent adult size before the crest starts to grow . now think about that . they 're basically retaining their juvenile characteristics very late in what we call ontogeny . so allometric cranial ontogeny is relative skull growth . so you can see that if you actually found one that was 80 percent grown and you did n't know that it was going to grow up to a cassowary , you would think they were two different animals . so this was a problem , and peter dodson pointed this out using some duck-billed dinosaurs then called hypacrosaurus . and he showed that if you were to take a baby and an adult and make an average of what it should look like , if it grew in sort of a linear fashion , it would have a crest about half the size of the adult . but the actual subadult at 65 percent had no crest at all . so this was interesting . so this is where people went astray again . i mean , if they 'd have just taken that , taken peter dodson 's work , and gone on with that , then we would have a lot less dinosaurs than we have . but scientists have egos ; they like to name things . and so they went on naming dinosaurs because they were different . now we have a way of actually testing to see whether a dinosaur , or any animal , is a young one or an older one . and that 's by actually cutting into their bones . but cutting into the bones of a dinosaur is hard to do , as you can imagine , because in museums , bones are precious . you go into a museum , and they take really good care of them . they put them in foam , little containers . they 're very well taken care of . they do n't like it if you come in and want to saw them open and look inside . ( laughter ) so they do n't normally let you do that . ( laughter ) but i have a museum and i collect dinosaurs and i can saw mine open . so that 's what i do . ( applause ) so if you cut open a little dinosaur , it 's very spongy inside , like a . and if you cut into an older dinosaur , it 's very massive . you can tell it 's mature bone . so it 's real easy to tell them apart . so what i want to do is show you these . in north america in the northern plains of the united states and the southern plains of alberta and saskatchewan , there 's this unit of rock called the hell creek formation that produces the last dinosaurs that lived on earth . and there are 12 of them that everyone recognizes -- i mean the 12 primary dinosaurs that went extinct . and so we will evaluate them . and that 's sort of what i 've been doing . so my students , my staff , we 've been cutting them open . now as you can imagine , cutting open a leg bone is one thing , but when you go to a museum and say , `` you do n't mind if i cut open your dinosaur 's skull , do you ? '' they say , `` go away . '' ( laughter ) so here are 12 dinosaurs . and we want to look at these three first . so these are dinosaurs that are called pachycephalosaurus . and everybody knows that these three animals are related . and the assumption is that they 're related like cousins or whatever . but no one ever considered that they might be more closely related . in other words , people looked at them and they saw the differences . and you all know that if you are going to determine whether you 're related to your brother or your sister , you ca n't do it by looking at differences . you can only determine relatedness by looking for similarities . so people were looking at these and they were talking about how different they are . pachycephalosaurus has a big , thick dome on its head , and it 's got some little bumps on the back of its head , and it 's got a bunch of gnarly things on the end of its nose . and then stygimoloch , another dinosaur from the same age , lived at the same time , has spikes sticking out the back of its head . it 's got a little , tiny dome , and it 's got a bunch of gnarly stuff on its nose . and then there 's this thing called dracorex hogwartsia . guess where that came from ? dragon . so here 's a dinosaur that has spikes sticking out of its head , no dome and gnarly stuff on its nose . nobody noticed the gnarly stuff sort of looked alike . but they did look at these three and they said , `` these are three different dinosaurs , and dracorex is probably the most primitive of them . and the other one is more primitive than the other . '' it 's unclear to me how they actually sorted these three of them out . but if you line them up , if you just take those three skulls and just line them up , they line up like this . dracorex is the littlest one , stygimoloch is the middle-size one , pachycephalosaurus is the largest one . and one would think , that should give me a clue . ( laughter ) but it did n't give them a clue . ( laughter ) because , well we know why . scientists like to name things . so if we cut open dracorex -- i cut open our dracorex -- and look , it was spongy inside , really spongy inside . i mean , it is a juvenile and it 's growing really fast . so it is going to get bigger . if you cut open stygimoloch , it is doing the same thing . the dome , that little dome , is growing really fast . it 's inflating very fast . what 's interesting is the spike on the back of the dracorex was growing very fast as well . the spikes on the back of the stygimoloch are actually resorbing , which means they 're getting smaller as that dome is getting bigger . and if we look at pachycephalosaurus , pachycephalosaurus has a solid dome and its little bumps on the back of its head were also resorbing . so just with these three dinosaurs , as a scientist , we can easily hypothesize that it is just a growth series of the same animal . which of course means that stygimoloch and dracorex are extinct . ( laughter ) ok. ( laughter ) which of course means we have 10 primary dinosaurs to deal with . so a colleague of mine at berkeley -- he and i were looking at triceratops . and before the year 2000 -- now remember , triceratops was first found in the 1800s -- before 2000 , no one had ever seen a juvenile triceratops . there 's a triceratops in every museum in the world , but no one had ever collected a juvenile . and we know why , right ? because everybody wants to have a big one . so everyone had a big one . so we went out and collected a whole bunch of stuff and we found a whole bunch of little ones . they 're everywhere , they 're all over the place . so we have a whole bunch of them at our museum . ( laughter ) and everybody says it 's because i have a little museum . when you have a little museum , you have little dinosaurs . ( laughter ) if you look at the triceratops , you can see it 's changing , it 's shape-shifting . as the juveniles are growing up , their horns actually curve backwards . and then as they get older , the horns grow forward . and that 's pretty cool . if you look along the edge of the frill , they have these little triangular bones that actually grow big as triangles and then they flatten against the frill pretty much like the spikes do on the pachycephalosaurs . and then , because the juveniles are in my collection , i cut them open ... ( laughter ) and look inside . and the little one is really spongy . and the middle-size one is really spongy . but what was interesting was the adult triceratops was also spongy . and this is a skull that is two meters long . it 's a big skull . but there 's another dinosaur that is found in this formation that looks like a triceratops , except it 's bigger , and it 's called torosaurus . and torosaurus , when we cut into it , has mature bone . but it 's got these big holes in its shield . and everybody says , `` a triceratops and a torosaurus ca n't possibly be the same animal because one of them 's bigger than the other one . '' ( laughter ) `` and it has holes in its frill . '' and i said , `` well do we have any juvenile torosauruses ? '' and they said , `` well , no , but it has holes in its frill . '' so one of my graduate students , john scannella , looked through our whole collection and he actually discovered that the hole starting to form in triceratops and , of course it 's open , in torosaurus -- so he found the transitional ones between triceratops and torosaurus , which was pretty cool . so now we know that torosaurus is actually a grown-up triceratops . now when we name dinosaurs , when we name anything , the original name gets to stick and the second name is thrown out . so torosaurus is extinct . triceratops , if you 've heard the news , a lot of the newscasters got it all wrong . they thought torosaurus should be kept and triceratops thrown out , but that 's not going to happen . ( laughter ) all right , so we can do this with a bunch of dinosaurs . i mean , here 's edmontosaurus and anatotitan . anatotitan : giant duck . it 's a giant duck-bill dinosaur . here 's another one . so we look at the bone histology . the bone histology tells us that edmontosaurus is a juvenile , or at least a subadult , and the other one is an adult , and we have an ontogeny . and we get rid of anatotitan . so we can just keep doing this . and the last one is t. rex . so there 's these two dinosaurs , t. rex and nanotyrannus . ( laughter ) again , it makes you wonder . ( laughter ) but they had a good question . they were looking at them and they said , `` one 's got 17 teeth , and the biggest one 's got 12 teeth . and that does n't make any sense at all , because we do n't know of any dinosaurs that gain teeth as they get older . so it must be true -- they must be different . '' so we cut into them . and sure enough , nanotyrannus has juvenile bone and the bigger one has more mature bone . it looks like it could still get bigger . and at the museum of the rockies where we work , i have four t. rexes , so i can cut a whole bunch of them . but i did n't have to cut any of them really , because i just lined up their jaws and it turned out the biggest one had 12 teeth and the next smallest one had 13 and the next smallest had 14 . and of course , nano has 17 . and we just went out and looked at other people 's collections and we found one that has sort of 15 teeth . so again , real easy to say that tyrannosaurus ontogeny included nanotyrannus , and therefore we can take out another dinosaur . ( laughter ) so when it comes down to our end cretaceous , we have seven left . and that 's a good number . that 's a good number to go extinct , i think . now as you can imagine , this is not very popular with fourth-graders . ( laughter ) fourth-graders love their dinosaurs , they memorize them . and they 're not happy with this . ( laughter ) thank you very much . ( applause )
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they 're basically retaining their juvenile characteristics very late in what we call ontogeny . so allometric cranial ontogeny is relative skull growth . so you can see that if you actually found one that was 80 percent grown and you did n't know that it was going to grow up to a cassowary , you would think they were two different animals .
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allometric cranial ontogeny is :
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you 're in line at the grocery store when , uh oh , someone sneezes on you . the cold virus is sucked inside your lungs and lands on a cell on your airway lining . every living thing on earth is made of cells , from the smallest one-celled bacteria to the giant blue whale to you . each cell in your body is surrounded by a cell membrane , a thick flexible layer made of fats and proteins , that surrounds and protects the inner components . it 's semipermeable , meaning that it lets some thing pass in and out but blocks others . the cell membrane is covered with tiny projections . they all have functions , like helping cells adhere to their neighbors or binding to nutrients the cell will need . animal and plant cells have cell membranes . only plant cells have a cell wall , which is made of rigid cellulose that gives the plant structure . the virus cell that was sneezed into your lungs is sneaky . pretending to be a friend , it attaches to a projection on the cell membrane , and the cell brings it through the cell membrane and inside . when the virus gets through , the cell recognizes its mistake . an enemy is inside ! special enzymes arrive at the scene and chop the virus to pieces . they then send one of the pieces back through the cell membrane , where the cell displays it to warn neighboring cells about the invader . a nearby cell sees the warning and immediately goes into action . it needs to make antibodies , proteins that will attack and kill the invading virus . this process starts in the nucleus . the nucleus contains our dna , the blueprint that tells our cells how to make everything our bodies need to function . a certain section of our dna contains instructions that tell our cells how to make antibodies . enzymes in the nucleus find the right section of dna , then create a copy of these instructions , called messenger rna . the messenger rna leaves the nucleus to carry out its orders . the messenger rna travels to a ribosome . there can be as many as 10 million ribosomes in a human cell , all studded along a ribbon-like structure called the endoplasmic reticulum . this ribosome reads the instructions from the nucleus . it takes amino acids and links them together one by one creating an antibody protein that will go fight the virus . but before it can do that , the antibody needs to leave the cell . the antibody heads to the golgi apparatus . here , it 's packed up for delivery outside the cell . enclosed in a bubble made of the same material as the cell membrane , the golgi apparatus also gives the antibody directions , telling it how to get to the edge of the cell . when it gets there , the bubble surrounding the antibody fuses to the cell membrane . the cell ejects the antibody , and it heads out to track down the virus . the leftover bubble will be broken down by the cell 's lysosomes and its pieces recycled over and over again . where did the cell get the energy to do all this ? that 's the roll of the mitochondria . to make energy , the mitochondria takes oxygen , this is the only reason we breathe it , and adds electrons from the food we eat to make water molecules . that process also creates a high energy molecule , called atp which the cell uses to power all of its parts . plant cells make energy a different way . they have chloroplasts that combine carbon dioxide and water with light energy from the sun to create oxygen and sugar , a form of chemical energy . all the parts of a cell have to work together to keep things running smoothly , and all the cells of your body have to work together to keep you running smoothly . that 's a whole lot of cells . scientists think there are about 37 trillion of them .
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they all have functions , like helping cells adhere to their neighbors or binding to nutrients the cell will need . animal and plant cells have cell membranes . only plant cells have a cell wall , which is made of rigid cellulose that gives the plant structure . the virus cell that was sneezed into your lungs is sneaky . pretending to be a friend , it attaches to a projection on the cell membrane , and the cell brings it through the cell membrane and inside . when the virus gets through , the cell recognizes its mistake .
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once a protein is made , it needs to be able to leave the cell . the structure that packages the protein in a vesicle and directs it to the cell membrane is known as the :
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just now , somewhere in the universe , a star exploded . there goes another one . in fact , a supernova occurs every second or so in the observable universe , and there is one on average every 25 to 50 years in a galaxy the size and age of the milky way . yet we 've never actually been able to watch one happen from its first violent moments . of course , how would we ? there are hundreds of billions of stars close enough that we could watch the supernova explosion break through the surface of the star . but we 'd have to have our best telescopes focused on the right one at precisely the right time to get meaningful data . suffice it to say , the odds of that happening are astronomically low . but what if we could anticipate a supernova before its light reached us ? that may seem impossible . after all , nothing travels faster than the speed of light , right ? as far as we know , yes . but in a race , fast does n't matter if you take a detour while someone else beelines it for the finish line . for exactly that reason , photons do n't win the supernova race to earth . neutrinos do . here 's why . there are two types of supernova . type 1 is when a star accumulates so much matter from a neighboring star , that a runaway nuclear reaction ignites and causes it to explode . in type 2 , the star runs out of nuclear fuel , so the gravitational forces pulling in overwhelm the quantum mechanical forces pushing out , and the stellar core collapses under its own weight in a hundredth of a second . while the outer reaches of the star are unaffected by the collapsed core , the inner edges accelerate through the void , smash into the core , and rebound to launch the explosion . in both of these scenarios , the star expels an unparalleled amount of energy , as well as a great deal of matter . in fact , all atoms heavier than nickel , including elements like gold and silver , only form in supernova reactions . in type 2 supernovae , about 1 % of the energy consists of photons , which we know of as light , while 99 % radiates out as neutrinos , the elementary particles that are known for rarely interacting with anything . starting from the center of the star , the exploding matter takes tens of minutes , or even hours , or in rare cases , several days , to reach and break through the surface of the star . however , the neutrinos , thanks to their non-interactivity , take a much more direct route . by the time there is any visible change in the star 's suface , the neutrinos typically have a several hour head start over the photons . that 's why astronomers and physicists have been able to set up a project called snews , the supernova early warning system . when detectors around the world pick up bursts of neutrinos , they send messages to a central computer in new york . if multiple detectors receive similar signals within ten seconds , snews will trigger an alert warning that a supernova is imminent . aided by some distance and direction information from the neutrino detectors , the amateur astronomers and scientists alike will scan the skies and share information to quickly identify the new galactic supernova and turn the world 's major telescopes in that direction . the last supernova that sent detectable neutrinos to earth was in 1987 on the edge of the tarantula nebula in the large magellanic cloud , a nearby galaxy . its neutrinos reached earth about three hours ahead of the visible light . we 're due for another one any day now , and when that happens , snews should give you the opportunity to be among the first to witness something that no human has ever seen before .
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in both of these scenarios , the star expels an unparalleled amount of energy , as well as a great deal of matter . in fact , all atoms heavier than nickel , including elements like gold and silver , only form in supernova reactions . in type 2 supernovae , about 1 % of the energy consists of photons , which we know of as light , while 99 % radiates out as neutrinos , the elementary particles that are known for rarely interacting with anything .
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metals heavier than what element are formed in supernovae ?
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to understand climate change , think of the game `` tetris . '' for eons , earth has played a version of this game with blocks of carbon . they enter the atmosphere as carbon dioxide gas from volcanoes , decaying plant matter , breathing creatures and the surface of the sea . and they leave the atmosphere when they 're used by plants during photosynthesis , absorbed back into the ocean , or stored in soil and sediment . this game of tetris is called the carbon cycle , and it 's the engine of life on earth . what 's the connection to climate ? well , when that carbon dioxide is in the air , waiting to be reabsorbed , it traps a portion of the sun 's heat , which would otherwise escape to space . that 's why carbon dioxide is called a greenhouse gas . it creates a blanket of warmth , known as the greenhouse effect , that keeps our earth from freezing like mars . the more carbon dioxide blocks hang out in the atmosphere waiting to be cleared , the warmer earth becomes . though the amount of carbon in the atmosphere has varied through ice ages and astroid impacts , over the past 8,000 years the stable climate we know took shape , allowing human civilization to thrive . but about 200 years ago , we began digging up that old carbon that had been stored in the soil . these fossil fuels , coal , oil and natural gas are made from the buried remains of plants and animals that died long before humans evolved . the energy stored inside them was able to power our factories , cars and power plants . but burning these fuels also injected new carbon blocks into earth 's tetris game . at the same time , we cleared forests for agriculture , reducing the earth 's ability to remove the blocks . and since 1750 , the amount of carbon in the atmosophere has increased by 40 % , and shows no sign of slowing . just like in tetris , the more blocks pile up , the harder it becomes to restore stability . the extra carbon dioxide in the atmosphere accelerates the greenhouse effect by trapping more heat near the surface and causing polar ice caps to melt . and the more they melt , the less sunlight they 're able to reflect , making the oceans warm even faster . sea levels rise , coastal populations are threatened with flooding , natural ecosystems are disrupted , and the weather becomes more extreme over time . climate change may effect different people and places in different ways . but , ultimately , it 's a game that we 're all stuck playing . and unlike in tetris , we wo n't get a chance to start over and try again .
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and they leave the atmosphere when they 're used by plants during photosynthesis , absorbed back into the ocean , or stored in soil and sediment . this game of tetris is called the carbon cycle , and it 's the engine of life on earth . what 's the connection to climate ?
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what role does the ocean play in the carbon cycle ?
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there 's a job out there with a great deal of power , pay , prestige , and near-perfect job security . and there 's only one way to be hired : get appointed to the us supreme court . if you want to become a justice on the supreme court , the highest federal court in the united states , three things have to happen . you have to be nominated by the president of the united states , your nomination needs to be approved by the senate , and finally , the president must formally appoint you to the court . because the constitution does n't specify any qualifications , in other words , that there 's no age , education , profession , or even native-born citizenship requirement , a president can nominate any individual to serve . so far , six justices have been foreign-born , at least one never graduated from high school , and another was only 32 years old when he joined the bench . most presidents nominate individuals who broadly share their ideological view , so a president with a liberal ideology will tend to appoint liberals to the court . of course , a justice 's leanings are not always so predictable . for example , when president eisenhower , a republican , nominated earl warren for chief justice , eisenhower expected him to make conservative decisions . instead , warren 's judgements have gone down as some of the most liberal in the court 's history . eisenhower later remarked on that appointment as `` the biggest damned-fool mistake '' he ever made . many other factors come up for consideration , as well , including experience , personal loyalties , ethnicity , and gender . the candidates are then thoroughly vetted down to their tax records and payments to domestic help . once the president interviews the candidate and makes a formal nomination announcement , the senate leadership traditionally turns the nomination over to hearings by the senate judiciary committee . depending on the contentiousness of the choice , that can stretch over many days . since the nixon administration , these hearings have averaged 60 days . the nominee is interviewed about their law record , if applicable , and where they stand on key issues to discern how they might vote . and especially in more recent history , the committee tries to unearth any dark secrets or past indiscretions . the judiciary committee votes to send the nomination to the full senate with a positive or negative recommendation , often reflective of political leanings , or no recommendation at all . most rejections have happened when the senate majority has been a different political party than the president . when the senate does approve , it 's by a simple majority vote , with ties broken by the vice president . with the senate 's consent , the president issues a written appointment , allowing the nominee to complete the final steps to take the constitutional and judicial oaths . in doing so , they solemnly swear to administer justice without respect to persons and do equal right to the poor and the rich and faithfully and impartially discharge and perform all the duties incumbent upon a us supreme court justice . this job is for life , barring resignation , retirement , or removal from the court by impeachment . and of the 112 justices who have held the position , not one has yet been removed from office as a result of an impeachment . one of their roles is to protect the fundamental rights of all americans , even as different parties take power . with the tremendous impact of this responsibility , it 's no wonder that a us supreme court justice is expected to be , in the words of irving r. kaufman , `` a paragon of virtue , an intellectual titan , and an administrative wizard . '' of course , not every member of the court turns out to be an exemplar of justice . each leaves behind a legacy of decisions and opinions to be debated and dissected by the ultimate judges , time and history .
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instead , warren 's judgements have gone down as some of the most liberal in the court 's history . eisenhower later remarked on that appointment as `` the biggest damned-fool mistake '' he ever made . many other factors come up for consideration , as well , including experience , personal loyalties , ethnicity , and gender .
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who said “ the biggest damn fool mistake ( he ) ever made ” was to appoint earl warren to the united states supreme court ?
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so this is mercury . it ’ s a liquid metal , it is one of the , well , one liquid metal at this temperature . there are a couple of liquid metals in a little bit more exotic places in the world like spain or perhaps africa . but mercury is the chemical formula hg , the best way to remember the formula for mercury is like h.g . wells . hg , mercury , comes out of a well . mercury is one of the few elements that is liquid at room temperature or is the only metal that is liquid at room temperature unless you live in a very hot country , it is also very dense . and it has been known again since very early times . mercury is very poisonous . it is a really fantastic liquid . it was really used for making scientific instruments like barometers and thermometers , you know , and it ’ s really quite a beautiful metal . i really love it , when i was in school we used to but it on the bench and play football with it . you know , lots of people don ’ t like us to do that anymore , but what i will do is to pour a little bit of the liquid metal into this beaker so we can see the properties and you can see that it is really nice . flows , just like a liquid , it forms really quite nice balls . and you can see the really quite high meniscus forming around the mercury . it can get into the human body particularly in the brain where it gives signs of madness . it used to be used in the uk for making hats . i am not quite sure what they did with mercury to make hats , but this is where the expression , “ mad as a hatter ” came from , because the people making hats breathed in mercury vapour and this caused them to show signs of madness . so here we can slosh it around a little bit but we have got to be very careful that we don ’ t slosh it too much because it is extremely dense and heavy and it is very , very easy to go through the middle or the bottom of the glass bottle itself . tell me why you aren ’ t touching it with your hands ? well mercury it is associated with toxicity especially for the salts , so you know we like to try and minimise the contact with the mercury and the mercury salts as much as possible really , just so that we could be very careful with our health and safety . there was a tragic case in japan in the 1950s , when mercury got into the sea from chemical emissions from factories , and the organisms on the bottom of the sea turned them into , the mercury metal , into a compound that could be absorbed by the fish , particularly the shellfish , and then the fishermen and the people living the round this minamata bay , starting eating these things got large amounts of mercury in their brain . and i can ’ t remember the number but several thousand people got very ill and many of them died , so mercury in the environment is quite a serious problem . it is also an interesting point that mercury has been used for making chlorine by putting electric current thought solutions of salt and it is gradually being replaced . but unlike chemicals you can ’ t get rid of an element , so if you have mercury you can ’ t burn it or destroy it in any way . and so , there are problems now , what to do with the mercury that people no longer want . but it is a really beautiful element , really fantastic . it is used very often in electric chemistry , because you can form very , very good electrical contact with mercury . and in fact , many people that may have old telephones or old bells , you know the door bells which we have on our front door , inside the ‘ bing-bong ’ , is a mercury-activated switch which turns on the magnet and off the magnet very , very quickly . it is really beautiful . mercury has an interesting property that it will very easily form alloys which are called amalgams . my teeth and probably many of your teeth are filled with so called silver amalgam which is a mixture of mercury and silver which when it is freshly mixed is like a paste . but when the dentist pushes it into your tooth it then hardens and , all being well , it does not come out or at least does not come out for a number of years . but amalgams are not very strong . and many years ago when i worked at another university , mercury was being stolen from the university , from the chemistry department and nobody knew who was stealing it . until one day the window cleaner was walking out of the building and the bottom fell out of his bucket , because he had been stealing mercury by pouring it into the bottom…pouring it into his bucket and hiding it below the dirty water . and the mercury started to amalgamate with the metal of the bucket , it was a metal bucket , and eventually , the bucket could no longer hold the weight of the mercury and it suddenly fell out and the mercury all came off .
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so this is mercury . it ’ s a liquid metal , it is one of the , well , one liquid metal at this temperature . there are a couple of liquid metals in a little bit more exotic places in the world like spain or perhaps africa .
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as pete showed at the beginning of the video , mercury is a liquid metal at room temperature . what is its melting point at atmospheric pressure ?
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all animals communicate . crabs wave their claws at each other to signal that they 're healthy and ready to mate . cuttlefish use pigmented skin cells called chromatophores to create patterns on their skin that act as camouflage or warnings to rivals . honeybees perform complex dances to let other bees know the location and quality of a food source . all of these animals have impressive communication systems , but do they have language ? to answer that question , we can look at four specific qualities that are often associated with language : discreteness , grammar , productivity , and displacement . discreteness means that there is a set of individual units , such as sounds or words , that can be combined to communicate new ideas , like a set of refrigerator poetry magnets you can rearrange to create different phrases . grammar provides a system of rules that tells you how to combine those individual units . productivity is the ability to use language to create an infinite number of messages . and displacement is the ability to talk about things that are n't right in front of you , such as past , future , or fictional events . so , does animal communication exhibit any of these qualities ? for crabs and cuttlefish , the answer is no . they do n't combine their signals in creative ways . those signals also do n't have to be in a grammatical order , and they only communicate current conditions , like , `` i am healthy , '' or `` i am poisonous . '' but some animals actually do display some of these properties . bees use the moves , angle , duration , and intensity of their waggle dance to describe the location and richness of a food source . that source is outside the hive , so they exhibit the property of displacement . they share that language trait with prairie dogs , which live in towns of thousands , and are hunted by coyotes , hawks , badgers , snakes , and humans . their alarms calls indicate the predator 's size , shape , speed , and , even for human predators , what the person is wearing and if he 's carrying a gun . great apes , like chimps and gorillas , are great communicators , too . some have even learned a modified sign language . a chimpanzee named washoe demonstrated discreteness by combining multiple signs into original phrases , like , `` please open . hurry . '' coco , a female gorilla who understands more than 1000 signs , and around 2000 words of spoken english referred to a beloved kitten that had died . in doing so , she displayed displacement , though it 's worth noting that the apes in both of these examples were using a human communication system , not one that appeared naturally in the wild . there are many other examples of sophisticated animal communication , such as in dolphins , which use whistles to identify age , location , names , and gender . they can also understand some grammar in a gestural language researchers use to communicate with them . however , grammar is not seen in the dolphin 's natural communication . while these communication systems may have some of the qualities of language we 've identified , none display all four . even washoe and coco 's impressive abilities are still outpaced by the language skills of most three-year-old humans . and animals ' topics of conversation are usually limited . bees talk about food , prairie dogs talk about predators , and crabs talk about themselves . human language stands alone due to the powerful combination of grammar and productivity , on top of discreteness and displacement . the human brain can take a finite number of elements and create an infinite number of messages . we can craft and understand complex sentences , as well as words that have never been spoken before . we can use language to communicate about an endless range of subjects , talk about imaginary things , and even lie . research continues to reveal more and more about animal communication . it may turn out that human language and animal communication are n't entirely different but exist on a continuum . after all , we are all animals .
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their alarms calls indicate the predator 's size , shape , speed , and , even for human predators , what the person is wearing and if he 's carrying a gun . great apes , like chimps and gorillas , are great communicators , too . some have even learned a modified sign language .
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great apes like koko and washoe :
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translator : andrea mcdonough reviewer : jessica ruby today , we 're going to look at the world of rome through the eyes of a young girl . here she is , drawing a picture of herself in the atrium of her father 's enormous house . her name is domitia , and she is just 5 years old . she has an older brother who is fourteen , lucius domitius ahenobarbus , named after her dad . girls do n't get these long names that boys have . what is worse is that dad insists on calling all his daughters domitia . `` domitia ! '' his call to domitia drawing on the column , domitia iii . she has an older sister , domitia ii , who is 7 years old . and then there 's domitia i , who is ten . there would have been a domitia iv , but mom died trying to give birth to her three years ago . confused ? the romans were too . they could work out ancestry through the male line with the nice , tripartite names such as lucius domitius ahenobarbus . but they got in a real mess over which domitia was married to whom and was either the great aunt or the great stepmother and so on to whom when they came to write it down . domitia iii is not just drawing on the pillar , she 's also watching the action . you see , it 's early , in the time of day when all her dad 's clients and friends come to see him at home to pay their respects . lucius popidius secundus , a 17 year old , he wants to marry domitia ii within the next five to seven years , has come as well . he seems to be wooing not his future wife , but her dad . poor lucius , he does not know that domitia 's dad thinks he and his family are wealthy but still scumbags from the subura . afterall , it is the part of rome full of barbers and prostitutes . suddenly , all the men are leaving with dad . it 's the second hour and time for him to be in court with a sturdy audience of clients to applaud his rhetoric and hiss at his opponent . the house is now quieter . the men wo n't return for seven hours , not until dinner time . but what happens in the house for those seven hours ? what do domitia , domitia , and domitia do all day ? not an easy question ! everything written down by the romans that we have today was written by men . this makes constructing the lives of women difficult . however , we ca n't have a history of just roman men , so here it goes . we can begin in the atrium . there is a massive loom , on which dad 's latest wife is working on a new toga . domitia , domitia , and domitia are tasked with spinning the wool that will be used to weave this mighty garment , 30 or more feet long and elliptical in shape . romans loved the idea that their wives work wool . we know that because it 's written on the gravestones of so many roman women . unlike women in greece , roman women go out the house and move about the city . they go to the baths in the morning to avoid the men or to separate baths that are for women only . some do go in for the latest fad of the ad 70s : nude bathing with men present . where they have no place is where the men are : in the forum , in the law court , or in the senate house . their place in public is in the porticos with gardens , with sculpture , and with pathways for walking in . when domitia , domitia , and domitia want to leave the house to go somewhere , like the portico of livia , they must get ready . domitia ii and domitia iii are ready , but domitia i , who is betrothed to be married in two years to darling philatus , is n't ready . she 's not slow , she just has more to do . being betrothed means she wears the insignia of betrothal : engagement rings and all the gifts pilatus has given her - jewels , earrings , necklaces , and the pendants . she may even wear her myrtle crown . all this bling shouts , `` i 'm getting married to that 19 year old who gave me all this stuff i 'm wearing ! '' while as they wait , domitia ii and domitia iii play with their dolls that mirror the image of their sister decked out to be married . one day , these dolls will be dedicated to the household gods on the day of their wedding . okay , we 're ready . the girls step into litters carried by some burly slaves . they also have a chaperone with them and will be meeting an aunt at the porticus of livia . carried high on the shoulders of these slaves , the girls look out through the curtains to see the crowded streets below them . they traverse the city , pass the coliseum , but then turn off to climb up the hill to the porticus of livia . it was built by livia , the wife of the first emperor augustus , on the site of the house of vedius pollio . he was n't such a great guy . he once tried to feed a slave to the eels in his fish pond for simply dropping a dish . luckily , the emperor was at the dinner and tamed his temper . the litters are placed on the ground and the girls get out and arm in arm , two by two , they ascend the steps into the enclosed garden with many columns . domitia iii shot off and is drawing on a column . domitia ii joins her but seeks to read the graffiti higher up on the column . she spots a drawing of gladiators and tries to imagine seeing them fighting , something she will never be permitted to do , except from the very rear of the coliseum . from there , she will have a good view of the 50,000 spectators but will see little by way of blood and gore . if she really wanted a decent view , she could become a vestal virgin and would sit right down the front . but a career tending the sacred flame of vesta is not to everybody 's taste . domitia i has met another ten year old also decked out in the insignia of betrothal . home time . when they get there after the eighth hour , something is up . a smashed dish lies on the floor . all the slaves are being gathered together in the atrium and await the arrival of their master . dad is going to go mad . he will not hit his children , but like many other romans , he believes that slaves have to be punished . the whip lies ready for his arrival . no one knows who smashed the dish , but dad will call the undertaker to torture it out of them , if he must . the doorkeeper opens the front door to the house . a hush comes over the anxious slaves . in walks not their master but , instead , a pregnant teenager . it is the master 's eldest daughter , age 15 , who is already a veteran of marriage and child birth . guess what her name is . there is a five to ten percent chance she wo n't survive giving birth to her child , but , for now , she has come to dinner with her family . as a teenage mother , she has proved that she is a successful wife by bringing children and descendants for her husband , who will carry on his name in the future . the family head off to the dining room and are served dinner . it would seem dad has had an invite to dinner elsewhere . with dinner concluded , the girls crossed the atrium to bid farewell to their older sister who is carried home in a litter , escorted by some of dad 's bodyguards . returning to the house , the girls cross the atrium . the slaves , young and old , male and female , await the return of their owner . when he returns , he may exact vengeance , ensuring his power over the slaves is maintained through violence and terror , to which any slave could be subjected . but , for the girls , they head upstairs for the night , ready for bed .
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translator : andrea mcdonough reviewer : jessica ruby today , we 're going to look at the world of rome through the eyes of a young girl . here she is , drawing a picture of herself in the atrium of her father 's enormous house .
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who wrote all the recorded history of ancient rome that we have today ?
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it begins with a bit of discomfort and soon becomes a pressing sensation that 's impossible to ignore . finally , it 's all you can think about , and out of sheer desperation , you go on a hunt for a bathroom until `` ahh . '' humans should urinate at least four to six times a day , but occasionally , the pressures of modern life forces us to clench and hold it in . how bad is this habit , and how long can our bodies withstand it ? the answers lie in the workings of the bladder , an oval pouch that sits inside the pelvis . surrounding this structure are several other organs that together make up the whole urinary system . two kidneys , two ureters , two urethral sphincters , and a urethra . constantly trickling down from the kidneys is the yellowish liquid known as urine . the kidneys make urine from a mix of water and the body 's waste products , funneling the unwanted fluid into two muscular tubes called ureters . these carry it downward into the hollow organ known as the bladder . this organ 's muscular wall is made of tissue called detrusor muscle which relaxes as the bladder fills allowing it to inflate like a balloon . as the bladder gets full , the detrusor contracts . the internal urethral sphincter automatically and involuntarily opens , and the urine is released . whooshing downwards , the fluid enters the urethra and stops short at the external urethral sphincter . this works like a tap . when you want to delay urinating , you keep the sphincter closed . when you want to release it , you can voluntarily open the flood gates . but how do you sense your bladder 's fullness so you know when to pee ? inside the layers of detrusor muscles are millions of stretch receptors that get triggered as the bladder fills . they send signals along your nerves to the sacral region in your spinal cord . a reflex signal travels back to your bladder , making the detrusor muscle contract slightly and increasing the bladder 's pressure so you 're aware that it 's filling up . simultaneously , the internal urethral sphincter opens . this is called the micturition reflex . the brain can counter it if it 's not a good time to urinate by sending another signal to contract the external urethral sphincter . with about 150 to 200 milliliters of urine inside of it , the bladder 's muscular wall is stretched enough for you to sense that there 's urine within . at about 400 to 500 milliliters , the pressure becomes uncomfortable . the bladder can go on stretching , but only to a point . above 1,000 milliliters , it may burst . most people would lose bladder control before this happens , but in very rare cases , such as when as a person ca n't sense the need to urinate , the pouch can rupture painfully requiring surgery to fix . but under normal circumstances , your decision to urinate stops the brain 's signal to the external urethral sphincter , causing it to relax and the bladder to empty . the external urethral sphincter is one of the muscles of the pelvic floor , and it provides support to the urethra and bladder neck . it 's lucky we have these pelvic floor muscles because placing pressure on the system by coughing , sneezing , laughing , or jumping could cause bladder leakage . instead , the pelvic floor muscles keep the region sealed until you 're ready to go . but holding it in for too long , forcing out your urine too fast , or urinating without proper physical support may over time weaken or overwork that muscular sling . that can lead to an overactive pelvic floor , bladder pain , urgency , or urinary incontinence . so in the interest of long-term health , it 's not a great habit to hold your pee . but in the short term , at least , your body and brain have got you covered , so you can conveniently choose your moment of sweet release .
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simultaneously , the internal urethral sphincter opens . this is called the micturition reflex . the brain can counter it if it 's not a good time to urinate by sending another signal to contract the external urethral sphincter .
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in the micturition reflex , as the bladder fills , a reflex nerve signal from the spinal cord to the bladder causes :
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when we talk about english , we often think of it as a single language but what do the dialects spoken in dozens of countries around the world have in common with each other , or with the writings of chaucer ? and how are any of them related to the strange words in beowulf ? the answer is that like most languages , english has evolved through generations of speakers , undergoing major changes over time . by undoing these changes , we can trace the language from the present day back to its ancient roots . while modern english shares many similar words with latin-derived romance languages , like french and spanish , most of those words were not originally part of it . instead , they started coming into the language with the norman invasion of england in 1066 . when the french-speaking normans conquered england and became its ruling class , they brought their speech with them , adding a massive amount of french and latin vocabulary to the english language previously spoken there . today , we call that language old english . this is the language of beowulf . it probably does n't look very familiar , but it might be more recognizable if you know some german . that 's because old english belongs to the germanic language family , first brought to the british isles in the 5th and 6th centuries by the angles , saxons , and jutes . the germanic dialects they spoke would become known as anglo-saxon . viking invaders in the 8th to 11th centuries added more borrowings from old norse into the mix . it may be hard to see the roots of modern english underneath all the words borrowed from french , latin , old norse and other languages . but comparative linguistics can help us by focusing on grammatical structure , patterns of sound changes , and certain core vocabulary . for example , after the 6th century , german words starting with `` p , '' systematically shifted to a `` pf '' sound while their old english counterparts kept the `` p '' unchanged . in another split , words that have `` sk '' sounds in swedish developed an `` sh '' sound in english . there are still some english words with `` sk , '' like `` skirt , '' and `` skull , '' but they 're direct borrowings from old norse that came after the `` sk '' to `` sh '' shift . these examples show us that just as the various romance languages descended from latin , english , swedish , german , and many other languages descended from their own common ancestor known as proto-germanic spoken around 500 b.c.e . because this historical language was never written down , we can only reconstruct it by comparing its descendants , which is possible thanks to the consistency of the changes . we can even use the same process to go back one step further , and trace the origins of proto-germanic to a language called proto-indo-european , spoken about 6000 years ago on the pontic steppe in modern day ukraine and russia . this is the reconstructed ancestor of the indo-european family that includes nearly all languages historically spoken in europe , as well as large parts of southern and western asia . and though it requires a bit more work , we can find the same systematic similarities , or correspondences , between related words in different indo-european branches . comparing english with latin , we see that english has `` t '' where latin has `` d '' , and `` f '' where latin has `` p '' at the start of words . some of english 's more distant relatives include hindi , persian and the celtic languages it displaced in what is now britain . proto-indo-european itself descended from an even more ancient language , but unfortunately , this is as far back as historical and archeological evidence will allow us to go . many mysteries remain just out of reach , such as whether there might be a link between indo-european and other major language families , and the nature of the languages spoken in europe prior to its arrival . but the amazing fact remains that nearly 3 billion people around the world , many of whom can not understand each other , are nevertheless speaking the same words shaped by 6000 years of history .
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because this historical language was never written down , we can only reconstruct it by comparing its descendants , which is possible thanks to the consistency of the changes . we can even use the same process to go back one step further , and trace the origins of proto-germanic to a language called proto-indo-european , spoken about 6000 years ago on the pontic steppe in modern day ukraine and russia . this is the reconstructed ancestor of the indo-european family that includes nearly all languages historically spoken in europe , as well as large parts of southern and western asia .
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proto-indo-european was most likely spoken in _____ .
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steel and plastic . these two materials are essential to so much of our infrastructure and technology , and they have a complementary set of strengths and weaknesses . steel is strong and hard , but difficult to shape intricately . while plastic can take on just about any form , it 's weak and soft . so would n't it be nice if there were one material as strong as the strongest steel and as shapeable as plastic ? well , a lot of scientists and technologists are getting excited about a relatively recent invention called metallic glass with both of those properties , and more . metallic glasses look shiny and opaque , like metals , and also like metals , they conduct heat and electricity . but they 're way stronger than most metals , which means they can withstand a lot of force without getting bent or dented , making ultrasharp scalpels , and ultrastrong electronics cases , hinges , screws ; the list goes on . metallic glasses also have an incredible ability to store and release elastic energy , which makes them perfect for sports equipment , like tennis racquets , golf clubs , and skis . they 're resistant to corrosion , and can be cast into complex shapes with mirror-like surfaces in a single molding step . despite their strength at room temperature , if you go up a few hundred degrees celsius , they soften significantly , and can be deformed into any shape you like . cool them back down , and they regain the strength . so where do all of these wondrous attributes come from ? in essence , they have to do with metallic glass ' unique atomic structure . most metals are crystalline as solids . that means that if you zoomed in close enough to see the individual atoms , they 'd be neatly lined up in an orderly , repeating pattern that extends throughout the whole material . ice is crystalline , and so are diamonds , and salt . if you heat these materials up enough and melt them , the atoms can jiggle freely and move randomly , but when you cool them back down , the atoms reorganize themselves , reestablishing the crystal . but what if you could cool a molten metal so fast that the atoms could n't find their places again , so that the material was solid , but with the chaotic , amorphous internal structure of a liquid ? that 's metallic glass . this structure has the added benefit of lacking the grain boundaries that most metals have . those are weak spots where the material is more susceptible to scratches or corrosion . the first metallic glass was made in 1960 from gold and silicon . it was n't easy to make . because metal atoms crystallize so rapidly , scientists had to cool the alloy down incredibly fast , a million degrees kelvin per second , by shooting tiny droplets at cold copper plates , or spinning ultrathin ribbons . at that time , metallic glasses could only be tens or hundreds of microns thick , which was too thin for most practical applications . but since then , scientists have figured out that if you blend several metals that mix with each other freely , but ca n't easily crystallize together , usually because they have very different atomic sizes , the mixture crystallizes much more slowly . that means you do n't have to cool it down as fast , so the material can be thicker , centimeters instead of micrometers . these materials are called bulk metallic glasses , or bmgs . now there are hundreds of different bmgs , so why are n't all of our bridges and cars made out of them ? many of the bmgs currently available are made from expensive metals , like palladium and zirconium , and they have to be really pure because any impurities can cause crystallization . so a bmg skyscraper or space shuttle would be astronomically expensive . and despite their strength , they 're not yet tough enough for load-bearing applications . when the stresses get high , they can fracture without warning , which is n't ideal for , say , a bridge . but when engineers figure out how to make bmgs from cheaper metals , and how to make them even tougher , for these super materials , the sky 's the limit .
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in essence , they have to do with metallic glass ' unique atomic structure . most metals are crystalline as solids . that means that if you zoomed in close enough to see the individual atoms , they 'd be neatly lined up in an orderly , repeating pattern that extends throughout the whole material .
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how can you make metals or mixtures of metals glassy ?
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translator : andrea mcdonough reviewer : bedirhan cinar nearly every one of your science classes starts off with the scientific method . you recognize this ? ask a question , form a hypothesis , perform an experiment , collect data , draw conclusions , and then memorize a bunch of facts . this is really boring ! science is not a simple recipe in a cookbook , and learning is not memorizing facts for tests . yet , that is exactly what we do . we have to change this ! we have to look at how curiosity can ultimately benefit society by looking towards tomorrow , by going through a path from involvement to imagination to invention to innovation . and i 'd like to illustrate this by telling you the real story about how we discovered how geckos stick . first you need to get involved . you need to do curiosity-driven research yourself . we know that learning by being an active researcher is the best way to learn . imagine being in my lab and trying to discover how geckos stick . `` here is one of our subjects . this is a crested gecko . we are going to put the gecko on glass and we 're going to use a high speed camera that can capture up to 1,000 pictures in one second . there he goes . ok , record it . there 's the animal 's toes . '' `` so how do their feet stick and unstick so quickly ? '' how < i > do < /i > they do this ? we wonder , it 's kind of crazy , right ? it 's hard to believe . well it turns out , it was already known that the geckos have hairy toes , and those hairs are really small compared to your hair , and the little tips at the end are even smaller . well , my student tanya , who is not much older than some of you when she did this , a sophomore undergraduate , tried to figure this out , and we told that her that in order to do this , you 'd have to measure the force of a single hair . though we kind of only did this jokingly because these hairs are so small , we did n't think it was possible . but tanya did n't know that , and she went on to build the simplest , most beautiful measurement device ever . here it is : she took one of those tiny little hairs and put it on to a probe , and then she began pushing it into the metal beam . now she was very frustrated for months - it did n't stick . but she had figured out she had to orient it just like the gecko grabs on , and then it worked ! and there 's the little split ends grabbing the beam in that little window . and then she did something magical : for the first time ever , she measured the force of a single gecko hair that allowed her to discover a completely new way to stick to something , something no human has ever known before . they have hairy little toes , huge numbers of hairs , and each hair has the worst case of split ends possible , 100 to 1,000 nano-tips that an animal has on one hair , and 2 billion total , and they do n't stick by glue , or by suction , or by velcro . it was discovered that they stick by inter-molecular forces alone , by van der waals forces , and you 'll learn this in chemistry and physics , if you take it . it 's unbelievable ! it 's a whole new way of thinking about making an adhesive ! well , this is n't the end of the story , there are still mysteries . why are the gecko 's feet looking like this ? they have bizarre toes and we do n't know why . if you go into a museum and look at each gecko species , you see they have all different hairs , different lengths , and thicknesses , and patterns . why ? i do n't know ! but you should come to berkeley and help me figure this out . it 's just about right , so , apply . but it 's a mystery . there is even more stuff that is unknown . this tarantula also has hairs and can stick this way , too , but recently it was found that they also can secrete silk from their feet , not just their behind , like you know they do . and even more recently , my graduate student ann showed that all spiders can secrete glue , and we know nothing about this glue except it was around way before this guy , millions of years before . so do n't stop at the discovery , next imagine the possible uses for society . here is the first human supported by a gecko-inspired adhesive . this is my former graduate student , kellar autumn , who is professor at lewis and clark , offering his second born child for the test . and she 's a very good sport about it ! now imagine all the things you could make from this , not only adhesives , but products in sports , and biomedicine , technology , robotics , toys , automotive , fashion , clothes , and yes , even hair pieces . i swear to you , we got a call from michael jackson 's hairdresser about hair pieces before he passed away . who would have guessed from studying geckos ? ! ? next , invent a game-changing technology , device , or product . like my engineering colleague at berkeley , ron fearing , did when he made one of the first synthetic , self-cleaning dry adhesives after the simplest version that you see in animals . believe it or not , right now , because of this work , you can make your own synthetic gecko nano-tape by nano-molding with just a few parts , and here 's the recipe that we can give you . it 's been incredible since we made this discovery of all the papers and the work and the different ways to make it , it 's emerging into a billion dollar industry . and who would have imagined that it started because we were curious about how geckos can run up walls . next you need to innovate , create a business that ultimately benefits society . did you know that there are 6 million people per year that have chronic wounds , 2 million develop an infection , and infections account for 100,000 hospital deaths ? imagine if you could build a company that could produce a gecko-inspired band-aid that would remove the pain and suffering . just a simple invention . if you look at the last three great earthquakes , over 700,000 people were trapped and lost their lives . imagine the company that made a search-and-rescue robot inspired from a gecko that could move anywhere and quickly find individuals that have been trapped , that sometimes survive as long as two weeks . there is a gecko-inspired robot , stickybot , from the stanford group , that can grab on to any surface . now we ran our own , for ted , mini bio-inspired design challenge to get you to think about these kinds of products . we have a winner . here 's the winner . the winner came up with this design called stickyseat . really clever . it 's a seat that is not only comfortable , but it aids a seat belt , if you were in an accident , in terms of keeping your seat and moving . this is brilliant ! we did n't think about this , although we might think about patenting it now , but there is a winner for this , and the winner , and you ca n't , you ca n't make up something like this , the winner 's name is harry . where 's harry ? harry , come here , we have a prize for you . where 's harry ? harry ! come here ! we have a crested gecko for you that has very cool hairs on it . congratulations for harry ! excellent job ! so do n't worry , if you missed out on this , it 's ok because we are doing another design challenge working with the san diego zoo . they 're developing a best ideas project in san diego , but it 's going to go national . and i 'll leave you with a fact that you should keep being curious because curiosity-based research leads to the biggest benefits , as we showed you in our example , and you < i > can < /i > make a difference < i > now < /i > because like tanya , you do n't know what ca n't be done . thank you .
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there 's the animal 's toes . '' `` so how do their feet stick and unstick so quickly ? '' how < i > do < /i > they do this ?
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how do gecko 's feet stick and unstick so quickly ?
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if you 've had surgery , you might remember starting to count backwards from ten , nine , eight , and then waking up with the surgery already over before you even got to five . and it might seem like you were asleep , but you were n't . you were under anesthesia , which is much more complicated . you were unconscious , but you also could n't move , form memories , or , hopefully , feel pain . without being able to block all those processes at once , many surgeries would be way too traumatic to perform . ancient medical texts from egypt , asia and the middle east all describe early anesthetics containing things like opium poppy , mandrake fruit , and alcohol . today , anesthesiologists often combine regional , inhalational and intravenous agents to get the right balance for a surgery . regional anesthesia blocks pain signals from a specific part of the body from getting to the brain . pain and other messages travel through the nervous system as electrical impulses . regional anesthetics work by setting up and electrical baracade . they bind to the proteins in neurons ' cell membranes that let charged particles in and out , and lock out positively charged particles . one compound that does this is cocaine , whose painkilling effects were discovered by accident when an ophthalmology intern got some on his tongue . it 's still occasionally used as an anesthetic , but many of the more common regional anesthetics have a similar chemical structure and work the same way . but for major surgeries where you need to be unconscious , you 'll want something that acts on the entire nervous system , including the brain . that 's what inhalational anesthetics do . in western medicine , diethyl ether was the first common one . it was best known as a recreational drug until doctors started to realize that people sometimes did n't notice injuries they received under the influence . in the 1840s , they started sedating patients with ether during dental extractions and surgeries . nitrous oxide became popular in the decades that followed and is still used today . although ether derivatives , like sevoflurane , are more common . inhalational anesthesia is usually supplemented with intravenous anesthesia , which was developed in the 1870s . common intravenous agents include sedatives , like propofol , which induce unconsciousness , and opioids , like fentanyl , which reduce pain . these general anesthetics also seem to work by affecting electrical signals in the nervous system . normally , the brain 's electrical signals are a chaotic chorus as different parts of the brain communicate with each other . that connectivity keeps you awake and aware . but as someone becomes anesthetized , those signals become calmer and more organized , suggesting that different parts of the brain are n't talking to each other anymore . there 's a lot we still do n't know about exactly how this happens . several common anesthetics bind to the gaba-a receptor in the brain 's neurons . they hold the gateway open , letting negatively charged particles flow into the cell . negative charge builds up and acts like a log jam , keeping the neuron from transmitting electrical signals . the nervous system has lots of these gated channels , controlling pathways for movement , memory , and consciousness . most anesthetics probably act on more than one , and they do n't act on just the nervous system . many anesthetics also affect the heart , lungs , and other vital organs . just like early anesthetics , which included familiar poisons like hemlock and aconite , modern drugs can have serious side effects . so an anesthesiologist has to mix just the right balance of drugs to create all the features of anesthesia , while carefully monitoring the patient 's vital signs , and adjusting the drug mixture as needed . anesthesia is complicated , but figuring out how to use it allowed for the development of new and better surgical techniques . surgeons could learn how to routinely and safely perform c-sections , reopen blocked arteries , replace damaged livers and kidneys , and many other life-saving operations . and each year , new anesthesia techniques are developed that will ensure more and more patients survive the trauma of surgery .
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just like early anesthetics , which included familiar poisons like hemlock and aconite , modern drugs can have serious side effects . so an anesthesiologist has to mix just the right balance of drugs to create all the features of anesthesia , while carefully monitoring the patient 's vital signs , and adjusting the drug mixture as needed . anesthesia is complicated , but figuring out how to use it allowed for the development of new and better surgical techniques .
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recently in america , there was an operation in which the patient had his/her phone recording the whole case . the patient ended up recording the hospital staff , including the anesthesiologist , saying hurtful and insensitive remarks about the patient while they were out , such as making rude comments about the patient 's weight , etc . how do you feel about this ? should the hospital staff simply get a slap on the wrist or should they lose their jobs ? what is the ethical responsibility of medical professionals while operating on a patient who is under anesthetics ?
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energy is all around us , a physical quantity that follows precise natural laws . our universe has a finite amount of it ; it 's neither created nor destroyed but can take different forms , such as kinetic or potential energy , with different properties and formulas to remember . for instance , an led desk lamp 's 6 watt bulb transfers 6 joules of light energy per second . but let 's jump back up into space to look at our planet , its systems , and their energy flow . earth 's physical systems include the atmosphere , hydrosphere , lithosphere , and biosphere . energy moves in and out of these systems , and during any energy transfer between them , some is lost to the surroundings , as heat , light , sound , vibration , or movement . our planet 's energy comes from internal and external sources . geothermal energy from radioactive isotopes and rotational energy from the spinning of the earth are internal sources of energy , while the sun is the major external source , driving certain systems , like our weather and climate . sunlight warms the surface and atmosphere in varying amounts , and this causes convection , producing winds and influencing ocean currents . infrared radiation , radiating out from the warmed surface of the earth , gets trapped by greenhouse gases and further affects the energy flow . the sun is also the major source of energy for organisms . plants , algae , and cyanobacteria use sunlight to produce organic matter from carbon dioxide and water , powering the biosphere 's food chains . we release this food energy using chemical reactions , like combustion and respiration . at each level in a food chain , some energy is stored in newly made chemical structures , but most is lost to the surroundings , as heat , like your body heat , released by your digestion of food . now , as plants are eaten by primary consumers , only about 10 % of their total energy is passed on to the next level . since energy can only flow in one direction in a food chain , from producers on to consumers and decomposers , an organism that eats lower on the food chain , is more efficient than one higher up . so eating producers is the most efficient level at which an animal can get its energy , but without continual input of energy to those producers , mostly from sunlight , life on earth as we know it would cease to exist . we humans , of course , spend our energy doing a lot of things besides eating . we travel , we build , we power all sorts of technology . to do all this , we use sources like fossil fuels : coal , oil , and natural gas , which contain energy that plants captured from sunlight long ago and stored in the form of carbon . when we burn fossil fuels in power plants , we release this stored energy to generate electricity . to generate electricity , heat from burning fossil fuels is used to power turbines that rotate magnets , which , in turn , create magnetic field changes relative to a coil of wire , causing electrons to be induced to flow in the wire . modern civilization depends on our ability to keep powering that flow of electrons . fortunately , we are n't limited to burning non-renewable fossil fuels to generate electricity . electrons can also be induced to flow by direct interaction with light particles , which is how a solar cell operates . other renewable energy sources , such as wind , water , geothermal , and biofuels can also be used to generate electricity . global demand for energy is increasing , but the planet has limited energy resources to access through a complex energy infrastructure . as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important . access to energy impacts health , education , political power , and socioeconomic status . if we improve our energy efficiency , we can use our natural resources more responsibly and improve quality of life for everyone .
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other renewable energy sources , such as wind , water , geothermal , and biofuels can also be used to generate electricity . global demand for energy is increasing , but the planet has limited energy resources to access through a complex energy infrastructure . as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important .
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which of the following provides the most energy for our ecosystem ?
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the idea of human rights is that each one of us , no matter who we are or where we are born , is entitled to the same basic rights and freedoms . human rights are not privileges , and they can not be granted or revoked . they are inalienable and universal . that may sound straighforward enough , but it gets incredibly complicated as soon as anyone tries to put the idea into practice . what exactly are the basic human rights ? who gets to pick them ? who enforces them , and how ? the history behind the concept of human rights is a long one . throughout the centuries and across societies , religions , and cultures we have struggled with defining notions of rightfulness , justice , and rights . but one of the most modern affirmations of universal human rights emerged from the ruins of world war ii with the creation of the united nations . the treaty that established the un gives as one of its purposes to reaffirm faith in fundamental human rights . and with the same spirit , in 1948 , the un general assembly adopted the universal declaration of human rights . this document , written by an international committee chaired by eleanor roosevelt , lays the basis for modern international human rights law . the declaration is based on the principle that all human beings are born free and equal in dignity and rights . it lists 30 articles recognizing , among other things , the principle of nondiscrimination and the right to life and liberty . it refers to negative freedoms , like the freedom from torture or slavery , as well as positive freedoms , such as the freedom of movement and residence . it encompasses basic civil and political rights , such as freedom of expression , religion , or peaceful assembly , as well as social , economic , and cultural rights , such as the right to education and the right to freely choose one 's occupation and be paid and treated fairly . the declaration takes no sides as to which rights are more important , insisting on their universality , indivisibility , and interdependence . and in the past decades , international human rights law has grown , deepening and expanding our understanding of what human rights are , and how to better protect them . so if these principles are so well-developed , then why are human rights abused and ignored time and time again all over the world ? the problem in general is that it is not at all easy to universally enforce these rights or to punish transgressors . the udhr itself , despite being highly authoritative and respected , is a declaration , not a hard law . so when individual countries violate it , the mechanisms to address those violations are weak . for example , the main bodies within the un in charge of protecting human rights mostly monitor and investigate violations , but they can not force states to , say , change a policy or compensate a victim . that 's why some critics say it 's naive to consider human rights a given in a world where state interests wield so much power . critics also question the universality of human rights and emphasize that their development has been heavily guided by a small number of mostly western nations to the detriment of inclusiveness . the result ? a general bias in favor of civil policital liberties over sociopolitical rights and of individual over collective or groups rights . others defend universal human rights laws and point at the positive role they have on setting international standards and helping activists in their campaigns . they also point out that not all international human rights instruments are powerless . for example , the european convention on human rights establishes a court where the 47 member countries and their citizens can bring cases . the court issues binding decisions that each member state must comply with . human rights law is constantly evolving as are our views and definitions of what the basic human rights should be . for example , how basic or important is the right to democracy or to development ? and as our lives are increasingly digital , should there be a right to access the internet ? a right to digital privacy ? what do you think ?
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the court issues binding decisions that each member state must comply with . human rights law is constantly evolving as are our views and definitions of what the basic human rights should be . for example , how basic or important is the right to democracy or to development ?
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human rights are universal and apply to everybody no matter where they live .
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we have historical records that allow us to know how the ancient greeks dressed , how they lived , how they fought ... but how did they think ? one natural idea is that the deepest aspects of human thought -- our ability to imagine , to be conscious , to dream -- have always been the same . another possibility is that the social transformations that have shaped our culture may have also changed the structural columns of human thought . we may all have different opinions about this . actually , it 's a long-standing philosophical debate . but is this question even amenable to science ? here i 'd like to propose that in the same way we can reconstruct how the ancient greek cities looked just based on a few bricks , that the writings of a culture are the archaeological records , the fossils , of human thought . and in fact , doing some form of psychological analysis of some of the most ancient books of human culture , julian jaynes came up in the '70s with a very wild and radical hypothesis : that only 3,000 years ago , humans were what today we would call schizophrenics . and he made this claim based on the fact that the first humans described in these books behaved consistently , in different traditions and in different places of the world , as if they were hearing and obeying voices that they perceived as coming from the gods , or from the muses ... what today we would call hallucinations . and only then , as time went on , they began to recognize that they were the creators , the owners of these inner voices . and with this , they gained introspection : the ability to think about their own thoughts . so jaynes 's theory is that consciousness , at least in the way we perceive it today , where we feel that we are the pilots of our own existence -- is a quite recent cultural development . and this theory is quite spectacular , but it has an obvious problem which is that it 's built on just a few and very specific examples . so the question is whether the theory that introspection built up in human history only about 3,000 years ago can be examined in a quantitative and objective manner . and the problem of how to go about this is quite obvious . it 's not like plato woke up one day and then he wrote , `` hello , i 'm plato , and as of today , i have a fully introspective consciousness . '' ( laughter ) and this tells us actually what is the essence of the problem . we need to find the emergence of a concept that 's never said . the word introspection does not appear a single time in the books we want to analyze . so our way to solve this is to build the space of words . this is a huge space that contains all words in such a way that the distance between any two of them is indicative of how closely related they are . so for instance , you want the words `` dog '' and `` cat '' to be very close together , but the words `` grapefruit '' and `` logarithm '' to be very far away . and this has to be true for any two words within the space . and there are different ways that we can construct the space of words . one is just asking the experts , a bit like we do with dictionaries . another possibility is following the simple assumption that when two words are related , they tend to appear in the same sentences , in the same paragraphs , in the same documents , more often than would be expected just by pure chance . and this simple hypothesis , this simple method , with some computational tricks that have to do with the fact that this is a very complex and high-dimensional space , turns out to be quite effective . and just to give you a flavor of how well this works , this is the result we get when we analyze this for some familiar words . and you can see first that words automatically organize into semantic neighborhoods . so you get the fruits , the body parts , the computer parts , the scientific terms and so on . the algorithm also identifies that we organize concepts in a hierarchy . so for instance , you can see that the scientific terms break down into two subcategories of the astronomic and the physics terms . and then there are very fine things . for instance , the word astronomy , which seems a bit bizarre where it is , is actually exactly where it should be , between what it is , an actual science , and between what it describes , the astronomical terms . and we could go on and on with this . actually , if you stare at this for a while , and you just build random trajectories , you will see that it actually feels a bit like doing poetry . and this is because , in a way , walking in this space is like walking in the mind . and the last thing is that this algorithm also identifies what are our intuitions , of which words should lead in the neighborhood of introspection . so for instance , words such as `` self , '' `` guilt , '' `` reason , '' `` emotion , '' are very close to `` introspection , '' but other words , such as `` red , '' `` football , '' `` candle , '' `` banana , '' are just very far away . and so once we 've built the space , the question of the history of introspection , or of the history of any concept which before could seem abstract and somehow vague , becomes concrete -- becomes amenable to quantitative science . all that we have to do is take the books , we digitize them , and we take this stream of words as a trajectory and project them into the space , and then we ask whether this trajectory spends significant time circling closely to the concept of introspection . and with this , we could analyze the history of introspection in the ancient greek tradition , for which we have the best available written record . so what we did is we took all the books -- we just ordered them by time -- for each book we take the words and we project them to the space , and then we ask for each word how close it is to introspection , and we just average that . and then we ask whether , as time goes on and on , these books get closer , and closer and closer to the concept of introspection . and this is exactly what happens in the ancient greek tradition . so you can see that for the oldest books in the homeric tradition , there is a small increase with books getting closer to introspection . but about four centuries before christ , this starts ramping up very rapidly to an almost five-fold increase of books getting closer , and closer and closer to the concept of introspection . and one of the nice things about this is that now we can ask whether this is also true in a different , independent tradition . so we just ran this same analysis on the judeo-christian tradition , and we got virtually the same pattern . again , you see a small increase for the oldest books in the old testament , and then it increases much more rapidly in the new books of the new testament . and then we get the peak of introspection in `` the confessions of saint augustine , '' about four centuries after christ . and this was very important , because saint augustine had been recognized by scholars , philologists , historians , as one of the founders of introspection . actually , some believe him to be the father of modern psychology . so our algorithm , which has the virtue of being quantitative , of being objective , and of course of being extremely fast -- it just runs in a fraction of a second -- can capture some of the most important conclusions of this long tradition of investigation . and this is in a way one of the beauties of science , which is that now this idea can be translated and generalized to a whole lot of different domains . so in the same way that we asked about the past of human consciousness , maybe the most challenging question we can pose to ourselves is whether this can tell us something about the future of our own consciousness . to put it more precisely , whether the words we say today can tell us something of where our minds will be in a few days , in a few months or a few years from now . and in the same way many of us are now wearing sensors that detect our heart rate , our respiration , our genes , on the hopes that this may help us prevent diseases , we can ask whether monitoring and analyzing the words we speak , we tweet , we email , we write , can tell us ahead of time whether something may go wrong with our minds . and with guillermo cecchi , who has been my brother in this adventure , we took on this task . and we did so by analyzing the recorded speech of 34 young people who were at a high risk of developing schizophrenia . and so what we did is , we measured speech at day one , and then we asked whether the properties of the speech could predict , within a window of almost three years , the future development of psychosis . but despite our hopes , we got failure after failure . there was just not enough information in semantics to predict the future organization of the mind . it was good enough to distinguish between a group of schizophrenics and a control group , a bit like we had done for the ancient texts , but not to predict the future onset of psychosis . but then we realized that maybe the most important thing was not so much what they were saying , but how they were saying it . more specifically , it was not in which semantic neighborhoods the words were , but how far and fast they jumped from one semantic neighborhood to the other one . and so we came up with this measure , which we termed semantic coherence , which essentially measures the persistence of speech within one semantic topic , within one semantic category . and it turned out to be that for this group of 34 people , the algorithm based on semantic coherence could predict , with 100 percent accuracy , who developed psychosis and who will not . and this was something that could not be achieved -- not even close -- with all the other existing clinical measures . and i remember vividly , while i was working on this , i was sitting at my computer and i saw a bunch of tweets by polo -- polo had been my first student back in buenos aires , and at the time he was living in new york . and there was something in this tweets -- i could not tell exactly what because nothing was said explicitly -- but i got this strong hunch , this strong intuition , that something was going wrong . so i picked up the phone , and i called polo , and in fact he was not feeling well . and this simple fact , that reading in between the lines , i could sense , through words , his feelings , was a simple , but very effective way to help . what i tell you today is that we 're getting close to understanding how we can convert this intuition that we all have , that we all share , into an algorithm . and in doing so , we may be seeing in the future a very different form of mental health , based on objective , quantitative and automated analysis of the words we write , of the words we say . gracias . ( applause )
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we have historical records that allow us to know how the ancient greeks dressed , how they lived , how they fought ... but how did they think ? one natural idea is that the deepest aspects of human thought -- our ability to imagine , to be conscious , to dream -- have always been the same . another possibility is that the social transformations that have shaped our culture may have also changed the structural columns of human thought . we may all have different opinions about this .
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what does mariano sigman believe are the fossils of human thought ?
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how do you get what you want using just your words ? aristotle set out to answer exactly that question over 2,000 years ago with the treatise on rhetoric . rhetoric , according to aristotle , is the art of seeing the available means of persuasion . and today we apply it to any form of communication . aristotle focused on oration , though , and he described three types of persuasive speech . forensic , or judicial , rhetoric establishes facts and judgements about the past , similar to detectives at a crime scene . epideictic , or demonstrative , rhetoric makes a proclamation about the present situation , as in wedding speeches . but the way to accomplish change is through deliberative rhetoric , or symbouleutikon . rather than the past or the present , deliberative rhetoric focuses on the future . it 's the rhetoric of politicians debating a new law by imagining what effect it might have , like when ronald regan warned that the introduction of medicare would lead to a socialist future spent telling our children and our children 's children what it once was like in america when men were free . but it 's also the rhetoric of activists urging change , such as martin luther king jr 's dream that his children will one day live in a nation where they will not be judged by the color of their skin , but by the content of their character . in both cases , the speaker 's present their audience with a possible future and try to enlist their help in avoiding or achieving it . but what makes for good deliberative rhetoric , besides the future tense ? according to aristotle , there are three persuasive appeals : ethos , logos , and pathos . ethos is how you convince an audience of your credibility . winston churchill began his 1941 address to the u.s. congress by declaring , `` i have been in full harmony all my life with the tides which have flowed on both sides of the atlantic against privilege and monopoly , '' thus highlighting his virtue as someone committed to democracy . much earlier , in his defense of the poet archias , roman consul cicero appealed to his own practical wisdom and expertise as a politician : `` drawn from my study of the liberal sciences and from that careful training to which i admit that at no part of my life i have ever been disinclined . '' and finally , you can demonstrate disinterest , or that you 're not motivated by personal gain . logos is the use of logic and reason . this method can employ rhetorical devices such as analogies , examples , and citations of research or statistics . but it 's not just facts and figures . it 's also the structure and content of the speech itself . the point is to use factual knowledge to convince the audience , as in sojourner truth 's argument for women 's rights : `` i have as much muscle as any man and can do as much work as any man . i have plowed and reaped and husked and chopped and mowed and can any man do more than that ? '' unfortunately , speakers can also manipulate people with false information that the audience thinks is true , such as the debunked but still widely believed claim that vaccines cause autism . and finally , pathos appeals to emotion , and in our age of mass media , it 's often the most effective mode . pathos is neither inherently good nor bad , but it may be irrational and unpredictable . it can just as easily rally people for peace as incite them to war . most advertising , from beauty products that promise to relieve our physical insecurities to cars that make us feel powerful , relies on pathos . aristotle 's rhetorical appeals still remain powerful tools today , but deciding which of them to use is a matter of knowing your audience and purpose , as well as the right place and time . and perhaps just as important is being able to notice when these same methods of persuasion are being used on you .
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how do you get what you want using just your words ? aristotle set out to answer exactly that question over 2,000 years ago with the treatise on rhetoric .
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how do you persuade others and to what end ( s ) ?
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thorium itself as a metal is quite frisky and if you heat it in air it burns incredibly intensely . it ’ s also a component of lenses for cameras because when it ’ s mixed in with certain other elements to give you these lenses , it has a very high refractive index and a very low dispersion , which means you get really sharp images ; possibly in the lens that you ’ re filming me with right now .
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thorium itself as a metal is quite frisky and if you heat it in air it burns incredibly intensely . it ’ s also a component of lenses for cameras because when it ’ s mixed in with certain other elements to give you these lenses , it has a very high refractive index and a very low dispersion , which means you get really sharp images ; possibly in the lens that you ’ re filming me with right now .
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thorium is not exactly a rare element ; in the earth ’ s crust , it is almost as abundant as lead . at about 12 ppm in the earth ’ s crust , which position do you think thorium occupies in the table of most abundant elements ?
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gifts . what a wonderful thing . who can say `` no '' to them , right ? when i was six years old , i received my gifts . my first grade teacher had this brilliant idea . she wanted us to experience receiving gifts but also learning the virtue of complimenting each other . so she had all of us come to the front of the classroom , and she bought all of us gifts and stacked them in the corner . and she said , `` why do n't we just stand here and compliment each other ? if you hear your name called , go and pick up your gift and sit down . '' what a wonderful idea , right ? what could go wrong ? ( laughter ) well , there were 40 of us to start with , and every time i heard someone 's name called , i would give out the heartiest cheer . and then there were 20 people left , and 10 people left , and five left ... and three left . and i was one of them . and the compliments stopped . well , at that moment , i was crying . and i did n't want to hear `` gifts '' anymore . i did n't want compliments anymore , i just wanted to get out of there and sit down . and the teacher was freaking out . she was like , `` hey , would anyone say anything nice about these people ? '' ( laughter ) `` no one ? ok , why do n't you go get your gift and sit down . so behave next year -- someone might say something nice about you . '' ( laughter ) well , as i 'm describing this you , you probably know i remember this really well . ( laughter ) but i do n't know who felt worse that day . was it me or the teacher ? she must have realized that she turned a team-building event into a public roast for three six-year-olds . and without the humor . you know , when you see people get roasted on tv , it was funny . there was nothing funny about that day . so that was one version of me , and i would die to avoid being in that situation again -- to get rejected in public again . that 's one version . then fast-forward eight years . bill gates came to my hometown -- beijing , china -- to speak , and i saw his message . i fell in love with that guy . i thought , wow , i know what i want to do now . that night i wrote a letter to my family telling them : `` by age 25 , i will build the biggest company in the world , and that company will buy microsoft . '' ( laughter ) i totally embraced this idea of conquering the world -- domination , right ? and i did n't make this up , i did write that letter . and here it is -- ( laughter ) you do n't have to read this through -- ( laughter ) this is also bad handwriting , but i did highlight some key words . you get the idea . ( laughter ) so ... that was another version of me : one who will conquer the world . well , then two years later , i was presented with the opportunity to come to the united states . i jumped on it , because that was where bill gates lived , right ? ( laughter ) i thought that was the start of my entrepreneur journey . then , fast-forward another 14 years . i was 30 . nope , i did n't build that company . i did n't even start . i was actually a marketing manager for a fortune 500 company . and i felt i was stuck ; i was stagnant . why is that ? where is that 14-year-old who wrote that letter ? it 's not because he did n't try . it 's because every time i had a new idea , every time i wanted to try something new , even at work -- i wanted to make a proposal , i wanted to speak up in front of people in a group -- i felt there was this constant battle between the 14-year-old and the six-year-old . one wanted to conquer the world -- make a difference -- another was afraid of rejection . and every time that six-year-old won . and this fear even persisted after i started my own company . i mean , i started my own company when i was 30 -- if you want to be bill gates , you 've got to start sooner or later , right ? when i was an entrepreneur , i was presented with an investment opportunity , and then i was turned down . and that rejection hurt me . it hurt me so bad that i wanted to quit right there . but then i thought , hey , would bill gates quit after a simple investment rejection ? would any successful entrepreneur quit like that ? no way . and this is where it clicked for me . ok , i can build a better company . i can build a better team or better product , but one thing for sure : i 've got to be a better leader . i 've got to be a better person . i can not let that six-year-old keep dictating my life anymore . i have to put him back in his place . so this is where i went online and looked for help . google was my friend . ( laughter ) i searched , `` how do i overcome the fear of rejection ? '' i came up with a bunch of psychology articles about where the fear and pain are coming from . then i came up with a bunch of `` rah-rah '' inspirational articles about `` do n't take it personally , just overcome it . '' who does n't know that ? ( laughter ) but why was i still so scared ? then i found this website by luck . it 's called rejectiontherapy.com . ( laughter ) `` rejection therapy '' was this game invented by this canadian entrepreneur . his name is jason comely . and basically the idea is for 30 days you go out and look for rejection , and every day get rejected at something , and then by the end , you desensitize yourself from the pain . and i loved that idea . ( laughter ) i said , `` you know what ? i 'm going to do this . and i 'll feel myself getting rejected 100 days . '' and i came up with my own rejection ideas , and i made a video blog out of it . and so here 's what i did . this is what the blog looked like . day one ... ( laughter ) borrow 100 dollars from a stranger . so this is where i went to where i was working . i came downstairs and i saw this big guy sitting behind a desk . he looked like a security guard . so i just approached him . and i was just walking and that was the longest walk of my life -- hair on the back of my neck standing up , i was sweating and my heart was pounding . and i got there and said , `` hey , sir , can i borrow 100 dollars from you ? '' ( laughter ) and he looked up , he 's like , `` no . '' `` why ? '' and i just said , `` no ? i 'm sorry . '' then i turned around , and i just ran . ( laughter ) i felt so embarrassed . but because i filmed myself -- so that night i was watching myself getting rejected , i just saw how scared i was . i looked like this kid in `` the sixth sense . '' i saw dead people . ( laughter ) but then i saw this guy . you know , he was n't that menacing . he was a chubby , loveable guy , and he even asked me , `` why ? '' in fact , he invited me to explain myself . and i could 've said many things . i could 've explained , i could 've negotiated . i did n't do any of that . all i did was run . i felt , wow , this is like a microcosm of my life . every time i felt the slightest rejection , i would just run as fast as i could . and you know what ? the next day , no matter what happens , i 'm not going to run . i 'll stay engaged . day two : request a `` burger refill . '' ( laughter ) it 's when i went to a burger joint , i finished lunch , and i went to the cashier and said , `` hi , can i get a burger refill ? '' ( laughter ) he was all confused , like , `` what 's a burger refill ? '' ( laughter ) i said , `` well , it 's just like a drink refill but with a burger . '' and he said , `` sorry , we do n't do burger refill , man . '' ( laughter ) so this is where rejection happened and i could have run , but i stayed . i said , `` well , i love your burgers , i love your joint , and if you guys do a burger refill , i will love you guys more . '' ( laughter ) and he said , `` well , ok , i 'll tell my manager about it , and maybe we 'll do it , but sorry , we ca n't do this today . '' then i left . and by the way , i do n't think they 've ever done burger refill . ( laughter ) i think they 're still there . but the life and death feeling i was feeling the first time was no longer there , just because i stayed engaged -- because i did n't run . i said , `` wow , great , i 'm already learning things . great . '' and then day three : getting olympic doughnuts . this is where my life was turned upside down . i went to a krispy kreme . it 's a doughnut shop in mainly the southeastern part of the united states . i 'm sure they have some here , too . and i went in , i said , `` can you make me doughnuts that look like olympic symbols ? basically , you interlink five doughnuts together ... `` i mean there 's no way they could say yes , right ? the doughnut maker took me so seriously . ( laughter ) so she put out paper , started jotting down the colors and the rings , and is like , `` how can i make this ? '' and then 15 minutes later , she came out with a box that looked like olympic rings . and i was so touched . i just could n't believe it . and that video got over five million views on youtube . the world could n't believe that either . ( laughter ) you know , because of that i was in newspapers , in talk shows , in everything . and i became famous . a lot of people started writing emails to me and saying , `` what you 're doing is awesome . '' but you know , fame and notoriety did not do anything to me . what i really wanted to do was learn , and to change myself . so i turned the rest of my 100 days of rejection into this playground -- into this research project . i wanted to see what i could learn . and then i learned a lot of things . i discovered so many secrets . for example , i found if i just do n't run , if i got rejected , i could actually turn a `` no '' into a `` yes , '' and the magic word is , `` why . '' so one day i went to a stranger 's house , i had this flower in my hand , knocked on the door and said , `` hey , can i plant this flower in your backyard ? '' ( laughter ) and he said , `` no . '' but before he could leave i said , `` hey , can i know why ? '' and he said , `` well , i have this dog that would dig up anything i put in the backyard . i do n't want to waste your flower . if you want to do this , go across the street and talk to connie . she loves flowers . '' so that 's what i did . i went across and knocked on connie 's door . and she was so happy to see me . ( laughter ) and then half an hour later , there was this flower in connie 's backyard . i 'm sure it looks better now . ( laughter ) but had i left after the initial rejection , i would 've thought , well , it 's because the guy did n't trust me , it 's because i was crazy , because i did n't dress up well , i did n't look good . it was none of those . it was because what i offered did not fit what he wanted . and he trusted me enough to offer me a referral , using a sales term . i converted a referral . then one day -- and i also learned that i can actually say certain things and maximize my chance to get a yes . so for example , one day i went to a starbucks , and asked the manager , `` hey , can i be a starbucks greeter ? '' he was like , `` what 's a starbucks greeter ? '' i said , `` do you know those walmart greeters ? you know , those people who say 'hi ' to you before you walk in the store , and make sure you do n't steal stuff , basically ? i want to give a walmart experience to starbucks customers . '' ( laughter ) well , i 'm not sure that 's a good thing , actually -- actually , i 'm pretty sure it 's a bad thing . and he was like , `` oh '' -- yeah , this is how he looked , his name is eric -- and he was like , `` i 'm not sure . '' this is how he was hearing me . `` not sure . '' then i ask him , `` is that weird ? '' he 's like , `` yeah , it 's really weird , man . '' but as soon as he said that , his whole demeanor changed . it 's as if he 's putting all the doubt on the floor . and he said , `` yeah , you can do this , just do n't get too weird . '' ( laughter ) so for the next hour i was the starbucks greeter . i said `` hi '' to every customer that walked in , and gave them holiday cheers . by the way , i do n't know what your career trajectory is , do n't be a greeter . ( laughter ) it was really boring . but then i found i could do this because i mentioned , `` is that weird ? '' i mentioned the doubt that he was having . and because i mentioned , `` is that weird ? `` , that means i was n't weird . that means i was actually thinking just like him , seeing this as a weird thing . and again , and again , i learned that if i mention some doubt people might have before i ask the question , i gained their trust . people were more likely to say yes to me . and then i learned i could fulfill my life dream ... by asking . you know , i came from four generations of teachers , and my grandma has always told me , `` hey jia , you can do anything you want , but it 'd be great if you became a teacher . '' ( laughter ) but i wanted to be an entrepreneur , so i did n't . but it has always been my dream to actually teach something . so i said , `` what if i just ask and teach a college class ? '' i lived in austin at the time , so i went to university of texas at austin and knocked on professors ' doors and said , `` can i teach your class ? '' i did n't get anywhere the first couple of times . but because i did n't run -- i kept doing it -- and on the third try the professor was very impressed . he was like , `` no one has done this before . '' and i came in prepared with powerpoints and my lesson . he said , `` wow , i can use this . why do n't you come back in two months ? i 'll fit you in my curriculum . '' and two months later i was teaching a class . this is me -- you probably ca n't see , this is a bad picture . you know , sometimes you get rejected by lighting , you know ? ( laughter ) but wow -- when i finished teaching that class , i walked out crying , because i thought i could fulfill my life dream just by simply asking . i used to think i have to accomplish all these things -- have to be a great entrepreneur , or get a phd to teach -- but no , i just asked , and i could teach . and in that picture , which you ca n't see , i quoted martin luther king , jr. why ? because in my research i found that people who really change the world , who change the way we live and the way we think , are the people who were met with initial and often violent rejections . people like martin luther king , jr. , like mahatma gandhi , nelson mandela , or even jesus christ . these people did not let rejection define them . they let their own reaction after rejection define themselves . and they embraced rejection . and we do n't have to be those people to learn about rejection , and in my case , rejection was my curse , was my boogeyman . it has bothered me my whole life because i was running away from it . then i started embracing it . i turned that into the biggest gift in my life . i started teaching people how to turn rejections into opportunities . i use my blog , i use my talk , i use the book i just published , and i 'm even building technology to help people overcome their fear of rejection . when you get rejected in life , when you are facing the next obstacle or next failure , consider the possibilities . do n't run . if you just embrace them , they might become your gifts as well . thank you . ( applause )
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who can say `` no '' to them , right ? when i was six years old , i received my gifts . my first grade teacher had this brilliant idea .
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what happened to jua jiang when he was six years old ? how did it make him feel ?
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take a look out your window , put on your glasses if you wear them . you might want to grab a pair of binoculars , too , or a magnifying lens . now , what do you see ? well , whatever it is , it 's not the multiple layers of glass right in front of you . but have you ever wondered how something so solid can be so invisible ? to understand that , we have to understand what glass actually is , and where it comes from . it all begins in the earth 's crust , where the two most common elements are silicon and oxygen . these react together to form silicon dioxide , whose molecules arrange themselves into a regular crystalline form known as quartz . quartz is commonly found in sand , where it often makes up most of the grains and is the main ingredient in most type of glass . of course , you probably noticed that glass is n't made of multiple tiny bits of quartz , and for good reason . for one thing , the edges of the rigidly formed grains and smaller defects within the crystal structure reflect and disperse light that hits them . but when the quartz is heated high enough the extra energy makes the molecules vibrate until they break the bonds holding them together and become a flowing liquid , the same way that ice melts into water . unlike water , though , liquid silicon dioxide does not reform into a crystal solid when it cools . instead , as the molecules lose energy , they are less and less able to move into an ordered position , and the result is what is called an amorphous solid . a solid material with the chaotic structure of a liquid , which allows the molecules to freely fill in any gaps . this makes the surface of glass uniform on a microscopic level , allowing light to strike it without being scattered in different directions . but this still does n't explain why light is able to pass through glass rather than being absorbed as with most solids . for that , we need to go all the way down to the subatomic level . you may know that an atom consists of a nucleus with electrons orbiting around it , but you may be surprised to know that it 's mostly empty space . in fact , if an atom were the size of a sports stadium , the nucleus would be like a single pea in the center , while the electrons would be like grains of sand in the outer seats . that should leave plenty of space for light to pass through without hitting any of these particles . so the real question is not why is glass transparent , but why are n't all materials transparent ? the answer has to do with the different energy levels that electrons in an atom can have . think of these as different rows of seats in the stadium stands . an electron is initially assigned to sit in a certain row , but it could jump to a better row , if it only had the energy . as luck would have it , absorbing one of those light photons passing through the atom can provide just the energy the electron needs . but there 's a catch . the energy from the photon has to be the right amount to get an electron to the next row . otherwise , it will just let the photon pass by , and it just so happens that in glass , the rows are so far apart that a photon of visible light ca n't provide enough energy for an electron to jump between them . photons from ultraviolet light , on the other hand , give just the right amount of energy , and are absorbed , which is why you ca n't get a suntan through glass . this amazing property of being both solid and transparent has given glass many uses throughout the centuries . from windows that let in light while keeping out the elements , to lenses that allow us to see both the vast worlds beyond our planet , and the tiny ones right around us . it is hard to imagine modern civilization without glass . and yet for such an important material we rarely think about glass and its impact . it is precisely because the most important and useful quality of glass is being featureless and invisible that we often forget that it 's even there .
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think of these as different rows of seats in the stadium stands . an electron is initially assigned to sit in a certain row , but it could jump to a better row , if it only had the energy . as luck would have it , absorbing one of those light photons passing through the atom can provide just the energy the electron needs . but there 's a catch .
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what might help an electron move from one energy level to another ?
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for most of us , two degrees celsius is a tiny difference in temperature , not even enough to make you crack a window . but scientists have warned that as co2 levels in the atmosphere rise , an increase in the earth 's temperature by even this amount can lead to catastrophic effects all over the world . how can such a small measurable change in one factor lead to massive and unpredictable changes in other factors ? the answer lies in the concept of a mathematical tipping point , which we can understand through the familiar game of billiards . the basic rule of billiard motion is that a ball will go straight until it hits a wall , then bounce off at an angle equal to its incoming angle . for simplicity 's sake , we 'll assume that there is no friction , so balls can keep moving indefinitely . and to simplify the situation further , let 's look at what happens with only one ball on a perfectly circular table . as the ball is struck and begins to move according to the rules , it follows a neat star-shaped pattern . if we start the ball at different locations , or strike it at different angles , some details of the pattern change , but its overall form remains the same . with a few test runs , and some basic mathematical modeling , we can even predict a ball 's path before it starts moving , simply based on its starting conditions . but what would happen if we made a minor change in the table 's shape by pulling it apart a bit , and inserting two small straight edges along the top and bottom ? we can see that as the ball bounces off the flat sides , it begins to move all over the table . the ball is still obeying the same rules of billiard motion , but the resulting movement no longer follows any recognizable pattern . with only a small change to the constraints under which the system operates , we have shifted the billiard motion from behaving in a stable and predictable fashion , to fluctuating wildly , thus creating what mathematicians call chaotic motion . inserting the straight edges into the table acts as a tipping point , switching the systems behavior from one type of behavior ( regular ) , to another type of behavior ( chaotic ) . so what implications does this simple example have for the much more complicated reality of the earth 's climate ? we can think of the shape of the table as being analogous to the co2 level and earth 's average temperature : constraints that impact the system 's performance in the form of the ball 's motion or the climate 's behavior . during the past 10,000 years , the fairly constant co2 atmospheric concentration of 270 parts per million kept the climate within a self-stabilizing pattern , fairly regular and hospitable to human life . but with co2 levels now at 400 parts per million , and predicted to rise to between 500 and 800 parts per million over the coming century , we may reach a tipping point where even a small additional change in the global average temperature would have the same effect as changing the shape of the table , leading to a dangerous shift in the climate 's behavior , with more extreme and intense weather events , less predictability , and most importantly , less hospitably to human life . the hypothetical models that mathematicians study in detail may not always look like actual situations , but they can provide a framework and a way of thinking that can be applied to help understand the more complex problems of the real world . in this case , understanding how slight changes in the constraints impacting a system can have massive impacts gives us a greater appreciation for predicting the dangers that we can not immediately percieve with our own senses . because once the results do become visible , it may already be too late .
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for most of us , two degrees celsius is a tiny difference in temperature , not even enough to make you crack a window . but scientists have warned that as co2 levels in the atmosphere rise , an increase in the earth 's temperature by even this amount can lead to catastrophic effects all over the world . how can such a small measurable change in one factor lead to massive and unpredictable changes in other factors ?
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is there a way to avoid reaching the predicated levels of 800 ppm of carbon dioxide in the atmosphere ? what can you do on a person level to decrease your carbon footprint ?
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so now you can see the reactionís really going and itís really exothermic , weíre forming aluminium triiodide , and the exotherm is actually heating and starting to sublime off the excess iodine which you can see coming off as this really nice purple plume . iodine is this beautifully-coloured element . it has this beautiful purple colour . if you put it in solution , the colour of the solution varies depending what you dissolve it in . if you dissolve it in water , itís a sort-of dirty brown colour . if you dissolve it in an organic material like chloroform or carbon tetrachloride it is a beautiful purple colour . iodine is halide , a halogen element from the far right-hand side of the periodic table and it 's strongly oxidising in nature . likes to nick electrons off other atoms , so what weíre going to do is we are going to do a reaction with iodine , and today weíve ground some iodine . so itís normally found from chemical suppliers as really nice large crystals . but what we want to do as a reaction with it , well we need to make sure that the surface area of the iodine is really , really large so that all of it can react very very quickly with the other component . iodine also occurs quite widely in nature and is absolutely essential to life . if you donít have iodine , your thyroid gland , which is a small gland that controls development of all sorts of things in your body , doesnít operate properly . nowadays , iodide is added to table salt in countries like the uk and most other developed countries so nearly everybody has enough iodine . in the old days iodine had to be got from the environment and usually from the spray from the sea that was blown across the land , and so in nottingham , which is really near the centre of england a long way from the sea , or relatively long way from the sea , there were serious illnesses caused by people not having enough iodine . so-called goiter , which caused a swelling , the thyroid gland gets bigger , and this used to be called derbyshire neck this unpleasant illness , because it happened in this area of nottingham and derbyshire . so what weíre going to do is that we are going to mix it now with another element and that element is aluminium . so aluminium has electrons to give away . iodineís gon na nab ëem . going to see some oxidation chemistry in the formation of a new compound , which is aluminium triiodide . itís a really nice chemical reaction . but the way that we do it is that we mix the two together and we have to add water which acts a bit like solvent and also the oxygen in the water activates the iodine so that it becomes more strongly oxidising and then hopefully weíll see the new reaction . so iím going to just put some out into this small vessel . you can see this development effect of iodine really well that if you had tadpoles , baby frogs , they donít develop their legs and turn into frogs unless there is iodine in the water . the other component in this reaction is aluminium , ok ; and weíre using very , very finely powdered aluminium . not foil or not a rather large lump . this has been especially powdered for us , so again it has a very , very high surface area . one of my favourite chemical equations is ëtadpoles plus iodine goes to frogsí . so you can see the aluminium and the iodine mixed within this solid mixture . now still , these two components , these two elements they are still held away from one another they canít react . so what we need to do is add a small amount of water , which actually acts like a solvent but actually activates the iodine and then weíll wait and see what happens with the chemical reaction . iodine can be used as a disinfectant , in fact chlorine can be as well , but solution of iodine is often used when people have cuts . so if you cut yourself , fortunately i havenít any cuts at the moment , you can paint on iodine and because of its rather red colour it made cuts often look much worse . children would come home from school and their whole hand would be red and this would cause some excitement at home but it is quite an effective antiseptic . water : just take a small amount and add it to the reaction . so you can see itís starting to go now the chemical reaction because we are seeing the excess iodine subliming in the form of a vapour . now if we go in close we can hear it fizzing because this is actually an oxidation reaction and the formation of the new aluminium triiodide . now iím going to just mix this slightly to try and increase the rate of the chemical reaction slightly . so now you can see the reactionís really going and itís really exothermic , weíre forming aluminium triiodide , and the exotherm is actually heating and starting to sublime off the excess iodine which you can see coming off as this really nice purple plume . now deep inside the reaction now you can see the exothermic or the energy coming out and starting to cause a flame . really , really nice , really rapid chemical reaction : really beautiful . so weíre forming aluminium triiodide here which again is a very , very delicate compound ; quite reactive in itself . so you can see now the really nice new crystalline material . so , sadly , weíve managed to stain stigís fume cupboard . all of this really nice iodine forming a very fine layer across this fume cupboard . what do you think about that ? looks like a thorough cleaning job coming to be honest .
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in the old days iodine had to be got from the environment and usually from the spray from the sea that was blown across the land , and so in nottingham , which is really near the centre of england a long way from the sea , or relatively long way from the sea , there were serious illnesses caused by people not having enough iodine . so-called goiter , which caused a swelling , the thyroid gland gets bigger , and this used to be called derbyshire neck this unpleasant illness , because it happened in this area of nottingham and derbyshire . so what weíre going to do is that we are going to mix it now with another element and that element is aluminium .
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in an area near nottingham , why did several people suffer `` derbyshire neck , '' caused by a lack of iodine ( before this element was added to table salt ) ?
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what does the french revolution have to do with the time nasa accidentally crashed a $ 200 million orbiter into the surface of mars ? actually , everything . that crash happened due to an error in converting between two measurement systems , u.s. customary units and their s.i , or metric , equivalence . so what 's the connection to the french revolution ? let 's explain . for the majority of recorded human history , units like the weight of a grain or the length of a hand were n't exact and varied from place to place . and different regions did n't just use varying measurements . they had completely different number systems as well . by the late middle ages , the hindu-arabic decimal system mostly replaced roman numerals and fractions in europe , but efforts by scholars like john wilkins to promote standard decimal-based measures were less successful . with a quarter million different units in france alone , any widespread change would require massive disruption . and in 1789 , that disruption came . the leaders of the french revolution did n't just overthrow the monarchy . they sought to completely transform society according to the rational principles of the enlightenment . when the new government took power , the academy of sciences convened to reform the system of measurements . old standards based on arbitrary authority or local traditions were replaced with mathematical and natural relationships . for example , the meter , from the greek word for measure , was defined as 1/10,000,000 between the equator and north pole . and the new metric system was , in the words of the marquis de condorcet , `` for all people , for all time . '' standardizing measurements had political advantages for the revolutionaries as well . nobles could no longer manipulate local units to extract more rent from commoners , while the government could collect taxes more efficiently . and switching to a new republican calendar with ten-day weeks reduced church power by eliminating sundays . adoption of this new system was n't easy . in fact , it was a bit of a mess . at first , people used new units alongside old ones , and the republican calendar was eventually abandoned . when napoléon bonaparte took power , he allowed small businesses to use traditional measurements redefined in metric terms . but the metric system remained standard for formal use , and it spread across the continent , along with france 's borders . while napoléon 's empire lasted eight years , its legacy endured far longer . some european countries reverted to old measurements upon independence . others realized the value of standardization in an age of international trade . after portugal and the netherlands switched to metric voluntarily , other nations followed , with colonial empires spreading the system around the world . as france 's main rival , britain had resisted revolutionary ideas and retained its traditional units . but over the next two centuries , the british empire slowly transitioned , first approving the metric system as an optional alternative before gradually making it offical . however , this switch came too late for thirteen former colonies that had already gained independence . the united states of america stuck with the english units of its colonial past and today remains one of only three countries which have n't fully embraced the metric system . despite constant initiatives for metrication , many americans consider units like feet and pounds more intuitive . and ironically , some regard the once revolutionary metric system as a symbol of global conformity . nevertheless , the metric system is almost universally used in science and medicine , and it continues to evolve according to its original principles . for a long time , standard units were actually defined by carefully maintained physical prototypes . but thanks to improving technology and precision , these objects with limited access and unreliable longevity are now being replaced with standards based on universal constants , like the speed of light . consistent measurements are such an integral part of our daily lives that it 's hard to appreciate what a major accomplishment for humanity they 've been . and just as it arose from a political revolution , the metric system remains crucial for the scientific revolutions to come .
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nevertheless , the metric system is almost universally used in science and medicine , and it continues to evolve according to its original principles . for a long time , standard units were actually defined by carefully maintained physical prototypes . but thanks to improving technology and precision , these objects with limited access and unreliable longevity are now being replaced with standards based on universal constants , like the speed of light .
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what defines our current ‘ standard ’ for one meter ?
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in 1977 , the physicist edward purcell calculated that if you push a bacteria and then let go , it will stop in about a millionth of a second . in that time , it will have traveled less than the width of a single atom . the same holds true for a sperm and many other microbes . it all has to do with being really small . microscopic creatures inhabit a world alien to us , where making it through an inch of water is an incredible endeavor . but why does size matter so much for a swimmer ? what makes the world of a sperm so fundamentally different from that of a sperm whale ? to find out , we need to dive into the physics of fluids . here 's a way to think about it . imagine you are swimming in a pool . it 's you and a whole bunch of water molecules . water molecules outnumber you a thousand trillion trillion to one . so , pushing past them with your gigantic body is easy , but if you were really small , say you were about the size of a water molecule , all of a sudden , it 's like you 're swimming in a pool of people . rather than simply swishing by all the teeny , tiny molecules , now every single water molecule is like another person you have to push past to get anywhere . in 1883 , the physicist osborne reynolds figured out that there is one simple number that can predict how a fluid will behave . it 's called the reynolds number , and it depends on simple properties like the size of the swimmer , its speed , the density of the fluid , and the stickiness , or the viscosity , of the fluid . what this means is that creatures of very different sizes inhabit vastly different worlds . for example , because of its huge size , a sperm whale inhabits the large reynolds number world . if it flaps its tail once , it can coast ahead for an incredible distance . meanwhile , sperm live in a low reynolds number world . if a sperm were to stop flapping its tail , it would n't even coast past a single atom . to imagine what it would feel like to be a sperm , you need to bring yourself down to its reynolds number . picture yourself in a tub of molasses with your arms moving about as slow as the minute hand of a clock , and you 'd have a pretty good idea of what a sperm is up against . so , how do microbes manage to get anywhere ? well , many do n't bother swimming at all . they just let the food drift to them . this is somewhat like a lazy cow that waits for the grass under its mouth to grow back . but many microbes do swim , and this is where those incredible adaptations come in . one trick they can use is to deform the shape of their paddle . by cleverly flexing their paddle to create more drag on the power stroke than on the recovery stroke , single-celled organisms like paramecia manage to inch their way through the crowd of water molecules . but there 's an even more ingenious solution arrived at by bacteria and sperm . instead of wagging their paddles back and forth , they wind them like a cork screw . just as a cork screw on a wine bottle converts winding motion into forward motion , these tiny creatures spin their helical tails to push themselves forward in a world where water feels as thick as cork . other strategies are even stranger . some bacteria take batman 's approach . they use grappling hooks to pull themselves along . they can even use this grappling hook like a sling shot and fling themselves forward . others use chemical engineering . h. pylori lives only in the slimy , acidic mucus inside our stomachs . it releases a chemical that thins out the surrounding mucus , allowing it to glide through slime . maybe it 's no surprise that these guys are also responsible for stomach ulcers . so , when you look really closely at our bodies and the world around us , you can see all sorts of tiny creatures finding clever ways to get around in a sticky situation . without these adaptations , bacteria would never find their hosts , and sperms would never make it to their eggs , which means you would never get stomach ulcers , but you would also never be born in the first place . ( pop )
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picture yourself in a tub of molasses with your arms moving about as slow as the minute hand of a clock , and you 'd have a pretty good idea of what a sperm is up against . so , how do microbes manage to get anywhere ? well , many do n't bother swimming at all .
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which of the following strategies are used by microbes to get around ?
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