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the epic poem `` la dragontea '' describes how english explorer sir francis drake sailed across the gulf of venezuela in 1595 . he was aiming for the nearby lake maracaibo , home to a colony of spanish settlers he planned to overthrow . but as drake moved towards the mouth of the lake under cover of darkness , his plot was suddenly and magnificently foiled . huge flashes of lightning illuminated the landscape , exposing the fleet as if it were daytime , which warned the spanish about his approach . lake maracaibo is the stormiest place on the planet . the massive body of water at over 13,000 square kilometers is a place of almost perpetual storming . thunderstorms rage above it for up to 200 days of the year , each earsplitting event lasting for several hours . like everywhere else on earth , lightning at lake maracaibo is the result of opposing electrical charges that steadily build up inside storm clouds . once there 's a large enough difference between charges either within the cloud or between the clouds and the earth below , it forms a spark that becomes a lightning bolt . lightning strikes the earth about 350 million times per year , averaging out to eleven strikes a second . we know that thanks to satellites up in space and sensors on the ground . we can also measure the earth 's lightning density , which is the frequency with which lightning flashes in a square kilometer . knowing where lightning strikes and how often reveals the most lightning-rich places on earth . in the polar regions , there may only be one strike per several square kilometers each year . meanwhile , lightning density at the equator averages out to tens of flashes per square kilometer on account of the sun providing more heat to drive storms . yet nowhere can quite compare with lake maracaibo , where lightning strikes an average 250 times per square kilometer , giving it the highest lightning density of any place on earth . a number of factors converge to create the lake 's seemingly everlasting storms . firstly , lake maracaibo lies just ten degrees north of the equator , so there 's a wealth of solar energy available to fuel the storms . thunderstorms also require a supply of water vapor to feed on , and having the warm waters of the caribbean so close by provides an endless supply . finally , the lake 's southern and western edges are bordered by two massive mountain ranges , and as cool winds surge down these slopes , they force up warm air , destabilizing the atmosphere and causing storm clouds to form . together , these ingredients combine to give rise to the most awe-inspiring thunderstorms on the planet , a true sight to behold . centuries ago , sir francis drake may have cursed the lake 's intense illumination , but today , sailors actually embrace this phenomenon . they call it the maracaibo beacon , and use it as a natural lighthouse to illuminate their path across the seas .
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meanwhile , lightning density at the equator averages out to tens of flashes per square kilometer on account of the sun providing more heat to drive storms . yet nowhere can quite compare with lake maracaibo , where lightning strikes an average 250 times per square kilometer , giving it the highest lightning density of any place on earth . a number of factors converge to create the lake 's seemingly everlasting storms .
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given the factors that make lightning so common over lake maracaibo , which other countries or regions of the planet might you also expect to experience a lot of lightning ?
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french fries are delicious . french fries with ketchup are a little slice of heaven . the problem is it 's basically impossible to pour the exactly right amount . we 're so used to pouring ketchup that we do n't realize how weird its behavior is . imagine a ketchup bottle filled with a straight up solid like steel . no amount of shaking would ever get the steel out . now imagine that same bottle full of a liquid like water . that would pour like a dream . ketchup , though , ca n't seem to make up its mind . is it is a solid ? or a liquid ? the answer is , it depends . the world 's most common fluids like water , oils and alcohols respond to force linearly . if you push on them twice as hard , they move twice as fast . sir isaac newton , of apple fame , first proposed this relationship , and so those fluids are called newtonian fluids . ketchup , though , is part of a merry band of linear rule breakers called non-newtonian fluids . mayonnaise , toothpaste , blood , paint , peanut butter and lots of other fluids respond to force non-linearly . that is , their apparent thickness changes depending on how hard you push , or how long , or how fast . and ketchup is actually non-newtonian in two different ways . way number one : the harder you push , the thinner ketchup seems to get . below a certain pushing force , ketchup basically behaves like a solid . but once you pass that breaking point , it switches gears and becomes a thousand times thinner than it was before . sound familiar right ? way number two : if you push with a force below the threshold force eventually , the ketchup will start to flow . in this case , time , not force , is the key to releasing ketchup from its glassy prison . alright , so , why does ketchup act all weird ? well , it 's made from tomatoes , pulverized , smashed , thrashed , utterly destroyed tomatoes . see these tiny particles ? this is what remains of tomatoes cells after they go through the ketchup treatment . and the liquid around those particles ? that 's mostly water and some vinegar , sugar , and spices . when ketchup is just sitting around , the tomato particles are evenly and randomly distributed . now , let 's say you apply a weak force very quickly . the particles bump into each other , but ca n't get out of each other 's way , so the ketchup does n't flow . now , let 's say you apply a strong force very quickly . that extra force is enough to squish the tomato particles , so maybe instead of little spheres , they get smushed into little ellipses , and boom ! now you have enough space for one group of particles to get passed others and the ketchup flows . now let 's say you apply a very weak force but for a very long time . turns out , we 're not exactly sure what happens in this scenario . one possibility is that the tomato particles near the walls of the container slowly get bumped towards the middle , leaving the soup they were dissolved in , which remember is basically water , near the edges . that water serves as a lubricant betwen the glass bottle and the center plug of ketchup , and so the ketchup flows . another possibility is that the particles slowly rearrange themselves into lots of small groups , which then flow past each other . scientists who study fluid flows are still actively researching how ketchup and its merry friends work . ketchup basically gets thinner the harder you push , but other substances , like oobleck or some natural peanut butters , actually get thicker the harder you push . others can climb up rotating rods , or continue to pour themselves out of a beeker , once you get them started . from a physics perspective , though , ketchup is one of the more complicated mixtures out there . and as if that were n't enough , the balance of ingredients and the presence of natural thickeners like xanthan gum , which is also found in many fruit drinks and milkshakes , can mean that two different ketchups can behave completely differently . but most will show two telltale properties : sudden thinning at a threshold force , and more gradual thinning after a small force is applied for a long time . and that means you could get ketchup out of the bottle in two ways : either give it a series of long , slow languid shakes making sure you do n't ever stop applying force , or you could hit the bottle once very , very hard . what the real pros do is keep the lid on , give the bottle a few short , sharp shakes to wake up all those tomato particles , and then take the lid off and do a nice controlled pour onto their heavenly fries .
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the answer is , it depends . the world 's most common fluids like water , oils and alcohols respond to force linearly . if you push on them twice as hard , they move twice as fast .
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how does a newtonian fluid respond to force ?
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in 1978 , louise brown became the world 's first baby to be born by in vitro fertilization , or ivf . her birth revolutionized the field of reproductive medicine . given that approximately one in eight heterosexual couples has difficulty conceiving , and that homosexual couples and single parents often need clinical help to make a baby , the demand for ivf has been growing . ivf is so common , that more than 5 million babies have been born through this technology . ivf works by mimicking the brilliant design of sexual reproduction . in order to understand ivf , we first need to take a look at the natural process of baby making . believe it or not , it all starts in the brain . roughly fifteen days before fertilization can happen , the anterior pituitary gland secretes follicle stimulating hormone , fsh , which ripens a handful of follicles of the ovary that then release estrogen . each follicle contains one egg , and on average , only one follicle becomes fully mature . as it grows and continues to release estrogen , this hormone not only helps coordinate growth and preparation of the uterus , it also communicates to the brain how well the follicle is developing . when the estrogen level is high enough , the anterior pituitary releases a surge of luteinizing hormone , lh , which triggers ovulation and causes the follicle to rupture and release the egg . once the egg leaves the ovary , it is directed into the fallopian tube by the finger-like fimbriae . if the egg is not fertilized by sperm within 24 hours , the unfertilized egg will die , and the entire system will reset itself , preparing to create a new egg and uterine lining the following month . the egg is the largest cell in the body and is protected by a thick , extracellular shell of sugar and protein called the zona pellucida . the zona thwarts the entry and fusion of more than one sperm , the smallest cell in the body . it takes a man two to three months to make sperm , and the process constantly renews . each ejaculation during sexual intercourse releases more than 100 million sperm . but only 100 or so will ultimately make it to the proximity of the egg , and only one will successfully penetrate through the armor of the zona pellucida . upon successful fertilization , the zygote immediately begins developing into an embryo , and takes about three days to reach the uterus . there , it requires another three or so days to implant firmly into the endometrium , the inner lining of the uterus . once implanted , the cells that are to become the placenta secrete a hormone that signals to the ovulated follicle that there is a pregnancy in the uterus . this helps rescue that follicle , now called the corpus luteum , from degenerating as it normally would do in that stage of the menstrual cycle . the corpus luteum is responsible for producing the progesterone required to maintain the pregnancy until six to seven weeks of gestation , when the placenta develops and takes over , until the baby is born approximately 40 weeks later . now , how do you make a baby in a lab ? in patients undergoing ivf , fsh is administered at levels that are higher than naturally occuring to cause a controlled overstimulation of the ovaries so that they ultimately produce multiple eggs . the eggs are then retrieved just before ovulation would occur , while the woman is under anesthesia , through an aspirating needle that is guided by ultrasound . most sperm samples are produced by masturbation . in the laboratory , the identified eggs are stripped of surrounding cells and prepared for fertilization in a petri dish . fertilization can occur by one of two techniques . in the first , the eggs are incubated with thousands of sperm and fertilization occurs naturally over a few hours . the second technique maximizes certainty of fertilization by using a needle to place a single sperm inside the egg . this is particularly useful when there is a problem with the quality of the sperm . after fertilization , embryos can be further screened for genetic suitability , frozen for later attempted pregnancies , or delivered into the woman 's uterus via catheter . common convention is to transfer the embryo three days after fertilization , when the embryo has eight cells , or on day five , when the embryo is called a blastocyst , and has hundreds of cells . if the woman 's eggs are of poor quality due to age or toxic exposures , or have been removed due to cancer , donor eggs may be used . in the case that the intended mother has a problematic uterus , or lacks one , another woman , called the gestational carrier or surrogate , can use her uterus to carry the pregnancy . to increase the odds of success , which are as high as 40 % for a woman younger than 35 , doctors sometimes transfer multiple embryos at once , which is why ivf results in twins and triplets more often than natural pregnancies . however , most clinics seek to minimize the chances of multiple pregnancies , as they are riskier for mothers and babies . millions of babies , like louise brown , have been born from ivf and have had normal , healthy lives . the long-term health consequences of ovarian stimulation with ivf medicines are less clear , though so far , ivf seems safe for women . because of better genetic testing , delayed childbearing , increased accessibility and diminishing cost , it 's not inconceivable that artificial baby making via ivf and related techniques could outpace natural reproduction in years to come .
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in 1978 , louise brown became the world 's first baby to be born by in vitro fertilization , or ivf . her birth revolutionized the field of reproductive medicine .
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aside from couples with infertility , who else could benefit from in vitro fertilization ?
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imagine you 're watching a runaway trolley barreling down the tracks straight towards five workers who ca n't escape . you happen to be standing next to a switch that will divert the trolley onto a second track . here 's the problem . that track has a worker on it , too , but just one . what do you do ? do you sacrifice one person to save five ? this is the trolley problem , a version of an ethical dilemma that philosopher philippa foot devised in 1967 . it 's popular because it forces us to think about how to choose when there are no good choices . do we pick the action with the best outcome or stick to a moral code that prohibits causing someone 's death ? in one survey , about 90 % of respondents said that it 's okay to flip the switch , letting one worker die to save five , and other studies , including a virtual reality simulation of the dilemma , have found similar results . these judgments are consistent with the philosophical principle of utilitarianism which argues that the morally correct decision is the one that maximizes well-being for the greatest number of people . the five lives outweigh one , even if achieving that outcome requires condemning someone to death . but people do n't always take the utilitarian view , which we can see by changing the trolley problem a bit . this time , you 're standing on a bridge over the track as the runaway trolley approaches . now there 's no second track , but there is a very large man on the bridge next to you . if you push him over , his body will stop the trolley , saving the five workers , but he 'll die . to utilitarians , the decision is exactly the same , lose one life to save five . but in this case , only about 10 % of people say that it 's ok to throw the man onto the tracks . our instincts tell us that deliberately causing someone 's death is different than allowing them to die as collateral damage . it just feels wrong for reasons that are hard to explain . this intersection between ethics and psychology is what 's so interesting about the trolley problem . the dilemma in its many variations reveal that what we think is right or wrong depends on factors other than a logical weighing of the pros and cons . for example , men are more likely than women to say it 's okay to push the man over the bridge . so are people who watch a comedy clip before doing the thought experiment . and in one virtual reality study , people were more willing to sacrifice men than women . researchers have studied the brain activity of people thinking through the classic and bridge versions . both scenarios activate areas of the brain involved in conscious decision-making and emotional responses . but in the bridge version , the emotional response is much stronger . so is activity in an area of the brain associated with processing internal conflict . why the difference ? one explanation is that pushing someone to their death feels more personal , activating an emotional aversion to killing another person , but we feel conflicted because we know it 's still the logical choice . trolleyology has been criticized by some philosophers and psychologists . they argue that it does n't reveal anything because its premise is so unrealistic that study participants do n't take it seriously . but new technology is making this kind of ethical analysis more important than ever . for example , driver-less cars may have to handle choices like causing a small accident to prevent a larger one . meanwhile , governments are researching autonomous military drones that could wind up making decisions of whether they 'll risk civilian casualties to attack a high-value target . if we want these actions to be ethical , we have to decide in advance how to value human life and judge the greater good . so researchers who study autonomous systems are collaborating with philosophers to address the complex problem of programming ethics into machines , which goes to show that even hypothetical dilemmas can wind up on a collision course with the real world .
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it just feels wrong for reasons that are hard to explain . this intersection between ethics and psychology is what 's so interesting about the trolley problem . the dilemma in its many variations reveal that what we think is right or wrong depends on factors other than a logical weighing of the pros and cons .
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the lesson discusses a common variation on the trolley problem that involves :
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so , i think all good tornado talks need to start with an awesome tornado shot . and this is not that awesome tornado shot . that was the first tornado i ever saw , it was really cool , really scary , and i 'm showing it to you guys because that 's why i got into the field in the first place . so even though it 's a bad photograph , it was really cool to be out there the first time . but now i 'm taking real tornado footage . fast forward a few years . this is a few years ago , during a field project called vortex2 , where myself and a bunch of other scientists were out there , surrounding tornadoes with different types of instrumentation and trying to figure out how tornadoes form . it 's a big question we 're trying to answer . it sounds like a very basic one , but it 's something we 're still trying to figure out . we 're also still trying to figure out what the winds are like near the surface . we know what the winds are like above building level , but we really do n't know what they 're like at the surface and how that relates to what we 're seeing above building level . most tornadoes form from what we call supercell thunderstorms . supercell thunderstorms are what you commonly think of as tornado-raising storms . they 're big , rotating thunderstorms that happen a lot of times in the midsection of the united states . but the problem is that even though they 're rotating up above , it does n't mean they 're rotating at the surface . and when we look at these storms and at these pictures and at the data we have , they all kind of look the same . and it 's really problematic if we 're trying to make tornado forecasts or warnings , because we only want to warn or forecast about the storms that are going to actually make a tornado . one of the big , critical distinguishing features , we think , between these storms , is something about the rear-flank downdraft . so these big rotating thunderstorms have this downdraft that wraps around the rear edge of it , hence the `` rear-flank '' downdraft . but we think how warm that is , how buoyant that air is , and then also how strong the updraft it 's wrapping into , makes a big difference on whether or not it 's going to make a tornado . there 's a lot more that goes into it -- i 'll tell you about that in a second . once you actually get a tornado , again , the problem that we have is getting measurements near the surface . it 's really hard to get measurements near the surface -- most people do n't want to drive into tornadoes . there are a few exceptions ; you might have seen them on tv shows . but most people do n't want to do that . even getting instrumentation in the path of the tornado is pretty tricky , too . because , again , you do n't want to be that close to a tornado because sometimes the winds around the tornado are strong as well . so getting information , that critical location , is key for us because , again , we do n't know if the winds that we 're seeing above ground level , way above building level , actually map to the surface , if they 're stronger , weaker , or about the same as what we 're seeing above buildings . the way we get at answering a lot of these questions -- and i 'm an observationalist ; i love to get out in the field , and collect data on tornadoes -- we compile a lot of observations . i work with this group who operates mobile radars , and they 're exactly what they say -- basically , a radar on the back of a big blue truck , and we drive up really close to tornadoes to map out the winds . we map out the precipitation . we map out all these different things that are going on in order to better understand the processes in these storms . and that bottom there , that 's what a tornado looks like when you 're looking at it with a mobile radar , and really close . also , what we do is a lot of modeling , so we do a lot of computer models and simulations , because the atmosphere is governed by the laws of physics . so we can model the laws of physics and see where the tornado might go , where the storm might go , how strong the winds are near the surface and not actually have to go out in the field . but of course , we want to have both observations and modeling to move forward with the science . so , i showed you that video earlier that went real quick , too . this is what it looks like , looking at it with a radar . so you saw it visually , but this is what i get really excited about when i see now in the field , stuff that looks like this . the really exciting thing about looking at stuff like this is that we caught this storm from when it did n't make a tornado to when it made a tornado and intensified and when it dissipated . this is the one of the rare data sets that we have out there that were able to study the entire life cycle of a tornado . i talked about how we think that rear-flank downdraft is important because it tilts , there 's a lot of spin in the atmosphere , but the problem with all this spin in the atmosphere is it needs to be oriented vertically , because that 's what tornadoes are doing , and it needs to orientated vertically near the ground . so we think this rear-flank downdraft just pulses . and these pulses in this rear-flank downdraft , we think , are very important for converging that rotation , but also getting that rotation into the right place . other things we 've learned is that we have gotten a bunch of fortuitous measurements in the path of the tornadoes and very near the surface . and we found out that the winds near the surface are actually pretty comparable to what we 're seeing 30 , 40 meters above ground level . so there 's not a big reduction in what we 're seeing above the surface to what we 're seeing at house level . and that was a pretty surprising finding for us , because we kind of assumed that the winds decrease pretty substantially near the surface . i 'm going to end with this real quick . and this is not my last tornado i ever saw , but i really like this image , because this was taken with one of those mobile radars i was talking about . this is a tornado , not a hurricane , and this is what it looks like when you 're really close to it . and i find this amazing , that we can actually take technology this close to these types of storms and see these inner workings . and for those of you who look at tornado images often , you can see there 's a lot going on -- there 's rain spiraling , and you can actually see the debris cloud associated with this tornado . i look forward to the future and future technologies and being able to learn a lot more about these storms , as the world advances , as you guys contribute to the science and we 're able to really learn more about how tornadoes form . thank you . ( applause )
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most tornadoes form from what we call supercell thunderstorms . supercell thunderstorms are what you commonly think of as tornado-raising storms . they 're big , rotating thunderstorms that happen a lot of times in the midsection of the united states .
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________ are rotating thunderstorms that are most commonly associated with tornado production .
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so , the apocalypse has happened . the zombies have come and gone , and all plant life on earth has died somehow . all you have are some basic supplies and some seeds of a few types of essential plants . so , what should you do to make absolutely sure they grow , seeing how rebuilding human civilization absolutely depends on it ? well , you 'd probably think the last thing you should do with these crucially important seeds is something like poking holes in them , or grinding them with sandpaper , or throwing them in acid or hot water . but , in fact , all of these are methods that are commonly used to help seeds start growing . a typical seed consists of a plant embryo encased in a hard seed coat . to start growing , it needs to emerge or sprout from inside this shell . this process is called germination . but just as it would be hard for you to get out of a jail cell with no windows and no doors , the embryo might need a little help escaping from its seed prison , and any process that makes this easier by wearing down the seed coat is called scarification . this lets moisture and nutrients get through the seed coat , making the embryo start growing until it breaks through . now , you might be wondering why it is that plants would need humans to do all these weird things to their seeds in order to grow , and , in fact , they do n't . in natural environments , seed coats are worn down by cold temperatures , bacteria , or even animal digestion . our scarification methods just mimick and accelerate these natural processes to increase the chances of successful germination . one technique we can use is called nicking . to do this , we make a small cut or scratch into the seed coat . be careful not to cut too deep ! you do n't want to damage the plant embryo inside . another way is to file down the seed coat using sandpaper or a nail file . once again , you do n't want to file too much , just enough to wear down some of the seed coat . after applying either of these methods , you 'll want to spray the seeds with bleach to prevent mold . seeds can also be soaked in water to soften the coat . one way to do this is to place the seeds in a nylon bag , then place the bag into hot water . turn off the heat immediately and allow the water to cool to room temperature before removing the seeds . it 's important not to heat the seed for too long as this will kill the embryo . again , you 'll want to spray them with bleach afterwards . finally , you can try immersing the seeds in a sulfuric acid solution . make sure you 're wearing protective goggles and gloves any time you work with such a dangerous substance . place the seeds into a wire mesh pouch and immerse the pouch in the solution for ten minutes . then take out the pouch and rinse it with clean water . take out the seeds and , as before , spray them with bleach so they do n't get moldy . if you try all of these methods , you will see that some of them are more effective than others , and some work best for different types of plants that have harder or thicker coats . so , knowing what seed scarification techniques work best will be useful if you ever need to survive a cataclysm , start a farm , or just want to plant in your own garden .
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in natural environments , seed coats are worn down by cold temperatures , bacteria , or even animal digestion . our scarification methods just mimick and accelerate these natural processes to increase the chances of successful germination . one technique we can use is called nicking .
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discuss how the man-made methods of scarification are related to the methods of scarification found in nature .
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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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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 .
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why are chemotherapeutic drugs generally successful against cancer cells ?
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we all know about the dinosaurs that once roamed the planet , but long after they went extinct , great beasts we call the megafauna lived on every continent . in the americas , ground sloths the size of elephants pulled down trees with their claws . saber-toothed cats the size of brown bears hunted in packs , but they were no match for short-faced bears , which stood thirteen feet on their hind legs , and are likely to have driven these cats away from their prey . there were armadillos as big as small cars , an eight foot beaver , and a bird with a 26 foot wingspan . almost everywhere , the world 's megafauna were driven to extinction , often by human hunters . some species still survive in parts of africa and asia . in other places , you can still see the legacy of these great beasts . most trees are able to resprout where their trunk is broken to withstand the loss of much of their bark and to survive splitting , twisting and trampling , partly because they evolved to survive attacks by elephants . the american pronghorn can run so fast because it evolved to escape the american cheetah . the surviving animals live in ghost ecosystems adapted to threats from species that no longer exist . today , it may be possible to resurrect those ghosts , to bring back lost species using genetic material . for instance , there 's been research in to cloning woolly mammoths from frozen remains . but even if it 's not possible , we can still restore many of the ecosystems the world has lost . how ? by making use of abandoned farms . as the market for food is globalized , infertile land becomes uncompetitive . farmers in barren places ca n't compete with people growing crops on better land elsewhere . as a result , farming has started to retreat from many regions , and trees have started to return . one estimate claims that two-thirds of land in the us that was once forested but was cleared for farming has become forested again . another estimate suggests that by 2030 , an area in europe the size of poland will be vaccated by farmers . so even if we ca n't use dna to bring back ground sloths and giant armadillos , we can restore bears , wolves , pumas lynx , moose and bison to the places where they used to live . some of these animals can reshape their surroundings , creating conditions that allow other species to thrive . when wolves were reintroduced to the yellowstone national park in 1995 , they quickly transformed the ecosystem . where they reduced the numbers of overpopulated deer , vegetation began to recover . the height of some trees quintupled in just six years . as forests returned , so did songbirds . beavers , which eat trees , multiplied in the rivers , and their dams provided homes for otters , muskrats , ducks , frogs and fish . the wolves killed coyotes , allowing rabbits and mice to increase , providing more food for hawks , weasels , foxes and badgers . bald eagles and ravens fed on the carrion that the wolves abandoned . so did bears , which also ate the berries on the returning shrubs . bison numbers rose as they browsed the revitalized forests . the wolves changed almost everything . this is an example of a trophic cascade , a change at the top of the food chain that tumbles all the way to the bottom , affecting every level . the discovery of widespread trophic cascades may be one of the most exciting scientific findings of the past half century . they tell us that ecosystems that have lost just one or two species of large animals can behave in radically different ways from those that retain them . all over the world , new movements are trying to catalyze the restoration of nature in a process called rewilding . this means undoing some of the damage we 've caused , reestablishing species which have been driven out , and then stepping back . there is no attempt to create an ideal ecosystem , to produce a heath , a rainforest or a coral reef . rewilding is about bringing back the species that drive dynamic processes and then letting nature take its course . but it 's essential that rewilding must never be used as an excuse to push people off the land . it should happen only with the consent and enthusiasm of the people who work there . imagine standing on a cliff in england , watching sperm whales attacking shoals of herring as they did within sight of the shore until the 18th century . by creating marine reserves in which no commerical fishing takes place , that can happen again . imagine a european serengeti full of the animals that used to live there : hippos , rhinos , elephants , hyenas and lions . what rewilding reintroduces , alongside the missing animals and plants , is that rare species called hope . it tells us that ecological change need not always proceed in the same direction . the silent spring could be followed by a wild summer .
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so even if we ca n't use dna to bring back ground sloths and giant armadillos , we can restore bears , wolves , pumas lynx , moose and bison to the places where they used to live . some of these animals can reshape their surroundings , creating conditions that allow other species to thrive . when wolves were reintroduced to the yellowstone national park in 1995 , they quickly transformed the ecosystem .
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the `` keystone species '' which has reshaped the ecology of much of the yellowstone national park , creating habitats for many other animals , is :
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if you ca n't imagine life without chocolate , you 're lucky you were n't born before the 16th century . until then , chocolate only existed in mesoamerica in a form quite different from what we know . as far back as 1900 bce , the people of that region had learned to prepare the beans of the native cacao tree . the earliest records tell us the beans were ground and mixed with cornmeal and chili peppers to create a drink - not a relaxing cup of hot cocoa , but a bitter , invigorating concoction frothing with foam . and if you thought we make a big deal about chocolate today , the mesoamericans had us beat . they believed that cacao was a heavenly food gifted to humans by a feathered serpent god , known to the maya as kukulkan and to the aztecs as quetzalcoatl . aztecs used cacao beans as currency and drank chocolate at royal feasts , gave it to soldiers as a reward for success in battle , and used it in rituals . the first transatlantic chocolate encounter occurred in 1519 when hernán cortés visited the court of moctezuma at tenochtitlan . as recorded by cortés 's lieutenant , the king had 50 jugs of the drink brought out and poured into golden cups . when the colonists returned with shipments of the strange new bean , missionaries ' salacious accounts of native customs gave it a reputation as an aphrodisiac . at first , its bitter taste made it suitable as a medicine for ailments , like upset stomachs , but sweetening it with honey , sugar , or vanilla quickly made chocolate a popular delicacy in the spanish court . and soon , no aristocratic home was complete without dedicated chocolate ware . the fashionable drink was difficult and time consuming to produce on a large scale . that involved using plantations and imported slave labor in the caribbean and on islands off the coast of africa . the world of chocolate would change forever in 1828 with the introduction of the cocoa press by coenraad van houten of amsterdam . van houten 's invention could separate the cocoa 's natural fat , or cocoa butter . this left a powder that could be mixed into a drinkable solution or recombined with the cocoa butter to create the solid chocolate we know today . not long after , a swiss chocolatier named daniel peter added powdered milk to the mix , thus inventing milk chocolate . by the 20th century , chocolate was no longer an elite luxury but had become a treat for the public . meeting the massive demand required more cultivation of cocoa , which can only grow near the equator . now , instead of african slaves being shipped to south american cocoa plantations , cocoa production itself would shift to west africa with cote d'ivoire providing two-fifths of the world 's cocoa as of 2015 . yet along with the growth of the industry , there have been horrific abuses of human rights . many of the plantations throughout west africa , which supply western companies , use slave and child labor , with an estimation of more than 2 million children affected . this is a complex problem that persists despite efforts from major chocolate companies to partner with african nations to reduce child and indentured labor practices . today , chocolate has established itself in the rituals of our modern culture . due to its colonial association with native cultures , combined with the power of advertising , chocolate retains an aura of something sensual , decadent , and forbidden . yet knowing more about its fascinating and often cruel history , as well as its production today , tells us where these associations originate and what they hide . so as you unwrap your next bar of chocolate , take a moment to consider that not everything about chocolate is sweet .
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the earliest records tell us the beans were ground and mixed with cornmeal and chili peppers to create a drink - not a relaxing cup of hot cocoa , but a bitter , invigorating concoction frothing with foam . and if you thought we make a big deal about chocolate today , the mesoamericans had us beat . they believed that cacao was a heavenly food gifted to humans by a feathered serpent god , known to the maya as kukulkan and to the aztecs as quetzalcoatl .
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cocoa has been consumed as a medicine for hundreds of years and is now thought to be heart healthy . why is that so ? ( hint : search the web for chocolate and medicine to read about the vasodilation of arteries )
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you might remember a pair of ted-ed lessons written and performed by two educators , brad voytek and tim verstynen . these two scientists used a drooling , hag-faced , animated zombie as a mechanism to model the symptoms and medical diagnosis process for various neurological conditions . for example , they spent time debating whether the zombie 's stiff gait was caused by basal ganglia damage , like that in parkinson 's patients , or by severe damage to the cerebellum , which can cause ataxia . in each lesson , brad and tim certainly showed us how the walking dead can help us understand neuroscience , but how can the walking dead help us understand animation ? or , more simply put , how did this one-eyed , decaying , and very much dead pile of pixels walk ? puppet animation is a relatively quick solution to creating 2-d animation of a hand-drawn character . since the character does not need to be drawn over and over again , it can be animated by moving each element individually . aside from their portrayal in a few great modern zombie flicks , these concocted carcasses are generally known for limited , stiff movements . their traditional stride is perfect for puppet-style animation . when designing a 2-d zombie puppet , or any other type of puppet , it is important to find a design that is both fun and functional in a flat environment . for example , you might not want to puppetize , say , julie andrews in the `` sound of music '' as she spins in circles . we used rotoscoping for her , but that 's another lesson . always begin by sketching and designing your puppet in a neutral pose like this . this will allow it to easily transition into and out of a variety of extreme positions . once a character transitions from concept stetches to final design , the next step is to break up the pieces in order to assemble a puppet , keeping in mind that each element needs to have an appropriate amount of overlap so that the zombie can bend at his joints . an understanding of anatomy is an integral part of designing any 2-d or 3-d animated character that needs to move realistically in the context of its environment . regardless of the number of dimensions your character has , you 'll need to create a skeleton , which in animation terms is known as a rig . once the rig is finalized and the range of motion is determined , the next step is to choose anchor points . each piece of artwork has its own anchor point , which essentially assigns the limb a hinge , which in this case is a joint . next , line the artwork up so that the anchor point for the forearm-elbow sits on the upper arm 's elbow area . once all the artwork is in place , you can use an expression script that creates links between the body parts . in this case , we used the expressions provided in after effects . by parenting one layer to another , you could teach the forearm to follow the upper arm and the hand to follow the forearm . this is what 's called forward kinematics . the alternative is inverse kinematics , in which a separate set of scripts control the motions . in this case , a controller is attached to the anchor point of the hand . the animator then uses the controller to position the hand . the scripts will then use an algorithm to make sure that the rest of the arm and body follows along . once the character is rigged , we can start animating . often times , puppet animation is done as straight-ahead action , which means moving a character frame-by-frame from beginning to end . another approach is pose-to-pose animation , which involves choosing your key poses first , and then filling in the intervals , or in-betweens , later . regardless of the method of motion , it 's important to think of your 2-d puppet as a piece of paper . it can move across a surface in a variety of poses , but it can not move in perspective . if your character needs to turn its head , then you will need to create additional art . we created three different zombie heads and six different hands to achieve different movements and angles that the neutral pose could n't accommodate . you can recreate almost everything you 've seen in this lesson with a pen , paper , and a camera . the method is called cut-out animation , and it was around well before the age of software . to create a stumbling 2-d zombie , or a speeding narwhal , or even an abstract character with some semblance of joints , simply print , cut , and fasten your character 's limbs together in a neutral pose . you can use fasteners , string , or even just place and move them each time . all the same rules and theories that we use in the computer apply to cut-out animation , except under the camera , the only way to animate is straight ahead .
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you can recreate almost everything you 've seen in this lesson with a pen , paper , and a camera . the method is called cut-out animation , and it was around well before the age of software . to create a stumbling 2-d zombie , or a speeding narwhal , or even an abstract character with some semblance of joints , simply print , cut , and fasten your character 's limbs together in a neutral pose .
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what is the process called where you create animation by drawing , cutting out the drawing , and taking pictures of it after you move it ?
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in 1815 , the eruption of mount tambora plunged parts of the world into darkness and marked a gloomy period that came to be known as the year without a summer . so when mary and percy shelley arrived at the house of lord byron on lake geneva , their vacation was mostly spent indoors . for amusement , byron proposed a challenge to his literary companions : who could write the most chilling ghost story ? this sparked an idea in 18-year-old mary . over the next few months , she would craft the story of frankenstein . popular depictions may evoke a green and groaning figure , but that 's not mary shelley 's monster . in fact , in the book , frankenstein refers to the nameless monster 's maker , dr. victor frankenstein . so tense is the struggle between creator and creature that the two have merged in our collective imagination . before you read or reread the original text , there are several other things that are helpful to know about frankenstein and how it came to assume its multiple meanings . the book traces dr. frankenstein 's futile quest to impart and sustain life . he constructs his monster part by part from dead matter and electrifies it into conscious being . upon completing the experiment , however , he 's horrified at the result and flees . but time and space are n't enough to banish the abandoned monster , and the plot turns on a chilling chase between the two . shelley subtitled her fireside ghost story , `` the modern prometheus . '' that 's in reference to the greek myth of the titan prometheus who stole fire from the gods and gave it to humanity . this gave humanity knowledge and power , but for tampering with the status quo , prometheus was chained to a rock and eaten by vultures for eternity . prometheus enjoyed a resurgence in the literature of the romantic period during the 18th century . mary was a prominent romantic , and shared the movement 's appreciation for nature , emotion , and the purity of art . two years after mary released `` frankenstein '' , percy reimagined the plight of prometheus in his lyrical drama , `` prometheus unbound . '' the romantics used these mythical references to signal the purity of the ancient world in contrast to modernity . they typically regarded science with suspicion , and `` frankenstein '' is one of the first cautionary tales about artificial intelligence . for shelley , the terror was not supernatural , but born in a lab . in addition , gothic devices infuse the text . the gothic genre is characterized by unease , eerie settings , the grotesque , and the fear of oblivion - all elements that can be seen in `` frankenstein . '' but this horror had roots in personal trauma , as well . the text is filled with references to shelley 's own circumstances . born in 1797 , mary was the child of william godwin and mary wollstonecraft . both were radical intellectual figures , and her mother 's book , `` a vindication of the rights of women , '' is a key feminist text . tragically , she died as a result of complications from mary 's birth . mary was haunted by her mother 's death , and later experienced her own problems with childbirth . she became pregnant following her elopement with percy at 16 , but that baby died shortly after birth . out of four more pregnancies , only one of their children survived . some critics have linked this tragedy to the themes explored in `` frankenstein . '' shelley depicts birth as both creative and destructive , and the monster becomes a disfigured mirror of the natural cycle of life . the monster , therefore , embodies dr. frankenstein 's corruption of nature in the quest for glory . this constitutes his fatal flaw , or hamartia . his god complex is most clear in the line , `` life and death appear to me ideal bounds which i should first break through and pour a torrent of light onto our dark world . '' although he accomplishes something awe-inspiring , he has played with fire at his own ethical expense . and that decision echoes throughout the novel , which is full of references to fire and imagery that contrasts light and dark . these moments suggest not only the spark of prometheus 's fire , but the power of radical ideas to expose darker areas of life .
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the romantics used these mythical references to signal the purity of the ancient world in contrast to modernity . they typically regarded science with suspicion , and `` frankenstein '' is one of the first cautionary tales about artificial intelligence . for shelley , the terror was not supernatural , but born in a lab .
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in science , religion or politics , the term frankenstein is sometimes used to describe a disastrous event created as the result of deliberate circumstances . why do you think this is ?
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some of the issues that are important if you want to have people in space for long periods of time . one is that people will tend to lose bone and muscle mass . we know this . if you have to put a cast on your leg , and you take the cast off after a few weeks , you 'll see that your muscles have shrunk in size . and if you measured the bone strength , you 'd also see that might have gone down a little bit , too . and so , it 's very interesting that our body has that ability to adapt to the loads that are put on it , so that bones and muscles are n't static , they 're always changing . while we think of bone as being a solid thing that does n't change very much , it changes too . and it turns out that in weightlessness , you lose bone . and then you also cause the muscles that work against gravity , what are called the postural muscles , they 'll start to shrink and lose strength . there are other things in the cardiovascular system , the heart and blood vessels . and if you think about it , standing up in gravity means you have to work against gravity in order to keep blood pumping to your head . so , if you could n't keep blood pumping in the head , you 'd pass out every time you stood up because when you 're lying down , you do n't have to push against gravity . but when you stand up , you got to work against gravity to keep blood flowing to your head . and your heart and blood vessels have a really nicely worked-out system to make that happen every time . but that system can also change in weightlessness . and then the other area that changes is the system that has to do with balance . again , maintaining your balance is something that you 're doing against gravity , right ? if you did n't have gravity present , you would n't have to worry about falling . but you obviously do have to worry about falling , and we have a very highly developed sense of balance to keep us upright and to prevent us from falling . and when you see what skaters do , you realize just how exquisite a system it is . but when you go into weightlessness , your balance system changes . you do n't really notice it while you are in weightlessness , but when you come back , you do notice it , that your balance has changed and you have a little bit of trouble maintaining your balance . and what it shows is that while you 're in space , your brain is trying to allow you to function in weightlessness . and so , it re-adapts you to be weightless , which you do n't notice until you come back and find out that you 're now back on earth with a balance system that 's been adapted to space . you know , all life developed here on earth with gravity being present , so life evolved under the influence of gravity , and then we grow up with gravity being present , so we learn how to walk and catch a ball and ice skate or whatever , all with gravity being present . and what if you were to grow up without gravity ? what about the systems that depend on gravity , like your muscles or your balance system or the heart and blood vessels ? would they develop normally , or would they be different in some way ? one reason why you might think that it would go down a different pathway is from an experiment that was done some time ago by two neuroscientists called hubel and wiesel . and what they did is they had a kitten , and they put a patch over the eye of the kitten . and then the kitten grew up to be a cat , and they removed the patch . and so , the question is , can the cat see out of that eye ? now , there 's nothing wrong with the eye , right ? but it just has n't seen anything , there has n't been any light coming in . and the answer is that the cat ca n't see out of that eye because what happens is that the brain goes down a different pathway when it develops and the connections that would ordinarily develop to that eye do n't develop . and that ca n't be undone , that 's a permanent change . so , the brain of that cat is fundamentally different from the brain of a cat that grew up seeing out of that eye . that cat grew up with a different brain , in essence . so , then you wonder , well , what about gravity ? what if you do n't have the forces that gravity produces ? is your balance organ going to develop in the same way , or will it be different ? if somebody grew up in space , could they come back to earth and function , or would they really be a different person ?
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would they develop normally , or would they be different in some way ? one reason why you might think that it would go down a different pathway is from an experiment that was done some time ago by two neuroscientists called hubel and wiesel . and what they did is they had a kitten , and they put a patch over the eye of the kitten .
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what animal was used in the famous hubel and wiesel experiments ?
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pick a card , any card . actually , just pick up all of them and take a look . this standard 52-card deck has been used for centuries . everyday , thousands just like it are shuffled in casinos all over the world , the order rearranged each time . and yet , every time you pick up a well-shuffled deck like this one , you are almost certainly holding an arrangement of cards that has never before existed in all of history . how can this be ? the answer lies in how many different arrangements of 52 cards , or any objects , are possible . now , 52 may not seem like such a high number , but let 's start with an even smaller one . say we have four people trying to sit in four numbered chairs . how many ways can they be seated ? to start off , any of the four people can sit in the first chair . one this choice is made , only three people remain standing . after the second person sits down , only two people are left as candidates for the third chair . and after the third person has sat down , the last person standing has no choice but to sit in the fourth chair . if we manually write out all the possible arrangements , or permutations , it turns out that there are 24 ways that four people can be seated into four chairs , but when dealing with larger numbers , this can take quite a while . so let 's see if there 's a quicker way . going from the beginning again , you can see that each of the four initial choices for the first chair leads to three more possible choices for the second chair , and each of those choices leads to two more for the third chair . so instead of counting each final scenario individually , we can multiply the number of choices for each chair : four times three times two times one to achieve the same result of 24 . an interesting pattern emerges . we start with the number of objects we 're arranging , four in this case , and multiply it by consecutively smaller integers until we reach one . this is an exciting discovery . so exciting that mathematicians have chosen to symbolize this kind of calculation , known as a factorial , with an exclamation mark . as a general rule , the factorial of any positive integer is calculated as the product of that same integer and all smaller integers down to one . in our simple example , the number of ways four people can be arranged into chairs is written as four factorial , which equals 24 . so let 's go back to our deck . just as there were four factorial ways of arranging four people , there are 52 factorial ways of arranging 52 cards . fortunately , we do n't have to calculate this by hand . just enter the function into a calculator , and it will show you that the number of possible arrangements is 8.07 x 10^67 , or roughly eight followed by 67 zeros . just how big is this number ? well , if a new permutation of 52 cards were written out every second starting 13.8 billion years ago , when the big bang is thought to have occurred , the writing would still be continuing today and for millions of years to come . in fact , there are more possible ways to arrange this simple deck of cards than there are atoms on earth . so the next time it 's your turn to shuffle , take a moment to remember that you 're holding something that may have never before existed and may never exist again .
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just as there were four factorial ways of arranging four people , there are 52 factorial ways of arranging 52 cards . fortunately , we do n't have to calculate this by hand . just enter the function into a calculator , and it will show you that the number of possible arrangements is 8.07 x 10^67 , or roughly eight followed by 67 zeros .
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which symbol do mathematicians use as a short hand to describe the product ( multiplication ) of an integer and all smaller integers down to 1 [ n x ( n-1 ) x ( n-2 ) x … x 1 ] ?
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this is a balloon of helium , and helium is a very small gas . we use in this case to find leaks in high pressure in high vacuum operators , because it 's very very small , finds the smallest , smallest holes . but just like hydrogen , it 's also very very light . and you know , in the past we used hydrogen to fill balloons , for transport , and now you see the goodyear blimp , sporting occasions , filled with helium . so helium is probably the most unreactive of the elements . it has a mass of 4 , so it weighs four times as much as a hydrogen atom , but hydrogen is an h2 molecule , whereas helium exists as isolated atoms , so that the a helium molecule weighs twice as much as hydrogen . see here , we have a helium filled balloon , and it 's extremely light , so i 'm not gon na let it go right now so i will lose it to the ceiling . so i 'm just gon na put on a piece of string . tie a lead around it again . helium can not be synthesized in nature because it is just an element . it is found as a component of natural gas in some places , particularly in the united states , because it is formed by the radioactive decay of minerals underground , and these form helium , which is trapped with the natural gas . so here we have a helium balloon floating , because it 's displacing its volume of air , and it 'll float quite nicely . it 's actually quite hard to contain , so the piece of string and the heavy stand is there holding it down , because we do n't really wan na lose it . if we take a balloon of another light gas , and that 's hydrogen , and we add a match to it or we set it on fire , it will burn really really quickly , and really energetically , because it makes for lots and lots of water , hydrogen plus oxygen . we 're gon na do the same experiment now , but we 're gon na do it with a helium filled balloon , and see if that 'll burn . so here we have a technical match on a stick , and we 're gon na offer it out to our floating balloon of helium . let 's see what happens this time . a little bit of a bang , but that 's just bang of the gas escaping , it did n't burn . yep , it 's unreactive , it 's an inert gas . the molecule is very light , so once it is in the atmosphere it will eventually go out into outer space . so that we are , in theory at least , likely to run out of helium in eventual future . if it is just released to the atmosphere . so what i got here is a balloon of helium , and it 's really really light , and it 's displacing a lot of volume , so if i let go of it it 's gon na fly like a balloon . so what we 're gon na do is i 'm gon na hold it down here , and neil is gon na cool it for me using some liquid nitrogen . now you can see neil is using gloves , because it 's very very cold . okay , so as he cools the balloon the gasses inside are slowing down , and they take up much much less volume as we slow them down , and now you can see it 's displacing less volume , so the balloon is quite happy to sit on the table . if we stop pouring the liquid nitrogen onto it now , and watch what happens as the balloon starts to warm up again . because the gases are gaining more energy , and they are occupying more space , and becoming more bouyant , so the helium comes back to the ceiling , where it really wants to be . the helium has a whole series of useful properties because it 's a very light gas , if you breathe in helium , you then start speaking like donald duck , in a very squeaky voice . helium . fantastic element . very light , very fun . because the speed of sound is much greater in helium than it is in ordinary gases . it is also very useful as a liquid . it only liquifies at very low temperature . its boiling point is -269 degrees centigrade . but if you cool things with liquid helium , you get very strange properties , for example , some materials lose their electrical resistance . so liquid helium is used for magnets when you need very powerful magnets , and for example , they 're used magnets from magnetic resonance imaging in hospitals . if you use a vacuum pump to pump hard on the helium , the boiling point will go even lower , and you can go to nearly two degrees absolute . and so helium is very important for all sorts of refrigiration . captions by www.subply.com
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the helium has a whole series of useful properties because it 's a very light gas , if you breathe in helium , you then start speaking like donald duck , in a very squeaky voice . helium . fantastic element .
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why did helium substitute hydrogen as the gas of choice in party balloons and airships ?
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is it a flying comma , or a quotation mark chopped in half ? either way , you may already be well-versed in how to use the apostrophe , but here 's a quick refresher on its usage . the apostrophe can be used in three ways : to mark possession , to mark contraction , to mark the plural of single letters . most of the time , if you see an apostrophe hovering helpfully near a word , it 's trying to mark possession or contraction . first , let 's look at how the apostrophe marks possession . as you can see , the placement of this punctuation mark can really change the meaning of a sentence . `` those robots in the sand are my sister 's . '' `` those robots in the sand are my sisters . ' '' `` those robots in the sand are my sisters . '' when showing possession , the apostrophe belongs next to the noun that owns or possesses something . the noun can be singular or plural . proper nouns work , too . so if lucy needs to get her robots under control before they cause mayhem , those dangerous creatures would be `` lucy 's robots . '' but what if lucy was lucas ? would we write `` lucas ' robots '' or `` lucas 's robots '' ? and what if lucas gave his robots to the robinsons family ? would it be `` the robinsons ' robots , '' or `` the robinsons 's robots '' ? the truth is , even grammar nerds disagree on the right thing to do . the use of 's after a proper noun ending in s is a style issue , not a hard and fast grammar rule . it 's a conundrum without a simple answer . professional writers solve this problem by learning what 's considered correct for a publication , and doing that . the important thing is to pick one style and stick with it throughout a piece of writing . one more wrinkle . certain pronouns already have possession built in and do n't need an apostrophe . remembering that will help you avoid one of the trickiest snags in english grammar : its vs. it 's . `` it 's '' only take an apostrophe when it 's a contraction for `` it is '' or `` it has . '' if you can replace `` it 's '' with one of those two phrases , use the apostrophe . if you 're showing possession , leave it out . otherwise , contractions are pretty straightforward . the apostrophe stands in for missing letters , and lets common phrases squash into a single word . in rare cases , you can have a double contraction , though those generally are n't accepted in writing , with the exception of dialogue . so it 's possessive , it 's often followed by s 's , and it 's sometimes tricky when it comes to its usage . it 's the apostrophe .
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so it 's possessive , it 's often followed by s 's , and it 's sometimes tricky when it comes to its usage . it 's the apostrophe .
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when in doubt as a writer of english , it 's best to leave out an apostrophe . why ?
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( music ) on a typical day at school , endless hours are spent learning the answers to questions . but right now , we 'll do the opposite . we 're going to focus on questions where you ca n't learn the answers , because they 're unknown . i used to puzzle about a lot of things as a boy . for example , what would it feel like to be a dog ? do fish feel pain ? how about insects ? was the big bang just an accident ? and is there a god ? and if so , how are we so sure that it 's a he and not a she ? why do so may innocent people and animals suffer terrible things ? is there really a plan for my life ? is the future yet to be written , or is it already written and we just ca n't see it ? but then , do i have free will ? who am i , anyway ? am i just a biological machine ? but then , why am i conscious ? what is consciousness ? will robots become conscious one day ? i mean , i kind of assumed that some day i would be told the answers to all these questions . i mean , someone must know , right ? huh . guess what ? no one knows . most of those questions puzzle me more now than ever . but diving into them is exciting because it takes you to the edge of knowledge , and you never know what you 'll find there . so , two questions to kick off this series , questions that no one on earth knows the answer to ... text : how many universes are there ? why ca n't we see evidence of alien life ?
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why do so may innocent people and animals suffer terrible things ? is there really a plan for my life ? is the future yet to be written , or is it already written and we just ca n't see it ?
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one of the questions anderson poses concerns predestination : “ is there a plan for my life ? ” is that idea comforting or disturbing ?
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once upon a time , south america lived harmoniously alongside africa until a crack in the earth drove the two continents apart . this breakup began about 200 million years ago during the separation of the supercontinent known as pangaea . their proximity back then explains why the same plant fossils and reptile fossils , like the mesosaurus , can be found on the south american east coast and african west coast . however , this evidence does not account for how the continents moved apart . for that , we 'll need to take a close look at the earth below our feet . though you may not realize it , the ground below you is traveling across the earth at a rate of about 10 cm/year , or the speed at which your fingernails grow . this is due to plate tectonics , or the large-scale movement of earth 's continents . the motion occurs within the top two layers of the earth 's mantle , the lithosphere and asthenosphere . the lithosphere , which includes the crust and uppermost mantle , comprises the land around you . beneath the lithosphere is the asthenosphere the highly viscous but solid rock portion of the upper mantle . it 's between 80 and 200 km below the earth 's surface . while the asthenosphere wraps around the earth 's core as one connected region , the lithosphere is separated on top into tectonic plates . there are seven primary tectonic plates that compose the shape of the planet we know today . like the other smaller tectonic plates , the primary plates are about 100 km thick and are composed of one or two layers : continental crust and oceanic crust . continental crust forms the continents and areas of shallow water close to their shores , whereas oceanic crust forms the ocean basins . the transition from the granitic continental crust to the basaltic oceanic crust occurs beyond the continentel shelf , in which the shore suddenly slopes down towards the ocean floor . the south american plate is an example of a tectonic plate made of two crusts : the continent we know from today 's map and a large region of the atlantic ocean around it . collectively comprising the lithosphere , these plates are brittler and stiffer than the heated , malleable layer of the asthenosphere below . because of this , the tectonic plates float on top of this layer , independently of one another . the speed and direction in which these tectonic plates move depends on the temperature and pressure of the asthenosphere below . scientists are still trying to nail down the driving forces behind this movement , with some theories pointing towards mantle convection , while others are examining the influence of the earth 's rotation and gravitational pull . though the mechanics have not been sorted out , the scientific community agrees that our tectonic plates are moving and have been for billions of years . because these plates move independently , a fair amount of pushing and pulling between the plates occurs . the first type of interaction is a divergent boundary , in which two plates move away from one another . we see this in the mid-atlantic ridge between south america and africa . the next interaction is when two plates collide , known as a convergent boundary . in this instance , the land is pushed upward to form large mountain ranges , like the himalayas . in fact , the indian plate is still colliding with the eurasian plate , which is why mount everest grows one cm/year . finally , there 's the transform boundaries , where two plates scrape past one another . the grinding of the transform boundary leads to many earthquakes , which is what happens in the 810 mile-long san andreas fault . the moving earth is unstoppable , and , while a shift of 10 cm/year may not seem like a lot , over millions of years our planet will continue to dramatically change . mountains will rise , shorelines will recede , islands will pop up . in fact , one projected map shows the cities of los angeles and san francisco on top of each other . maybe south america and africa will come together again , too . only time will tell .
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in fact , the indian plate is still colliding with the eurasian plate , which is why mount everest grows one cm/year . finally , there 's the transform boundaries , where two plates scrape past one another . the grinding of the transform boundary leads to many earthquakes , which is what happens in the 810 mile-long san andreas fault . the moving earth is unstoppable , and , while a shift of 10 cm/year may not seem like a lot , over millions of years our planet will continue to dramatically change .
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how does a transform boundary affect the planet ?
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you have about 20,000 genes in your dna . they encode the molecules that make up your body , from the keratin in your toenails , to the collagen at the tip of your nose , to the dopamine surging around inside your brain . other species have genes of their own . a spider has genes for spider silk . an oak tree has genes for chlorophyll , which turns sunlight into wood . so where did all those genes come from ? it depends on the gene . scientists suspect that life started on earth about 4 billion years ago . the early life forms were primitive microbes with a basic set of genes for the basic tasks required to stay alive . they passed down those basic genes to their offspring through billions of generations . some of them still do the same jobs in our cells today , like copying dna . but none of those microbes had genes for spider silk or dopamine . there are a lot more genes on earth today than there were back then . it turns out that a lot of those extra genes were born from mistakes . each time a cell divides , it makes new copies of its dna . sometimes it accidentally copies the same stretch of dna twice . in the process , it may make an extra copy of one of its genes . at first , the extra gene works the same as the original one . but over the generations , it may pick up new mutations . those mutations may change how the new gene works , and that new gene may duplicate again . a surprising number of our mutated genes emerged more recently ; many in just the past few million years . the youngest evolved after our own species broke off from our cousins , the apes . while it may take over a million years for a single gene to give rise to a whole family of genes , scientists are finding that once the new genes evolve , they can quickly take on essential functions . for example , we have hundreds of genes for the proteins in our noses that grab odor molecules . the mutations let them grab different molecules , giving us the power to perceive trillions of different smells . sometimes mutations have a bigger effect on new copies of genes . they may cause a gene to make its protein in a different organ , or at a different time of life , or the protein may start doing a different job altogether . in snakes , for example , there 's a gene that makes a protein for killing bacteria . long ago , the gene duplicated and the new copy mutated . that mutation changed the signal in the gene about where it should make its protein . instead of becoming active in the snake 's pacreas , it started making this bacteria-killing protein in the snake 's mouth . so when the snake bit its prey , this enzyme got into the animal 's wound . and when this protein proved to have a harmful effect , and helped the snake catch more prey , it became favored . so now what was a gene in the pancreas makes a venom in the mouth that kills the snake 's prey . and there are even more incredible ways to make a new gene . the dna of animals and plants and other species contain huge stretches without any protein coding genes . as far as scientists can tell , its mostly random sequences of genetic gibberish that serve no function . these stretches of dna sometimes mutate , just like genes do . sometimes those mutations turn the dna into a place where a cell can start reading it . suddenly the cell is making a new protein . at first , the protein may be useless , or even harmful , but more mutations can change the shape of the protein . the protein may start doing something useful , something that makes an organism healthier , stronger , better able to reproduce . scientists have found these new genes at work in many parts of animal bodies . so our 20,000 genes have many origins , from the origin of life , to new genes still coming into existence from scratch . as long as life is here on earth , it will be making new genes .
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the protein may start doing something useful , something that makes an organism healthier , stronger , better able to reproduce . scientists have found these new genes at work in many parts of animal bodies . so our 20,000 genes have many origins , from the origin of life , to new genes still coming into existence from scratch . as long as life is here on earth , it will be making new genes .
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many of the new genes produced are born from :
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translator : andrea mcdonough reviewer : bedirhan cinar the human eye is one of the most powerful machines on the planet . it 's like a 500 megapixel camera that can run in bright light , in near darkness , and even under water , though not real well . it communicates to our brains so much about the world . our eyes are how we find partners , how we understand the people around us , how we read , and how we watch game shows on tv where people get knocked into cold water by padded wrecking balls . yup , the human eye is pretty neat , and we 're lucky enough to have two of them . but , there are things that , despite looking really hard , we still ca n't quite see . for example , you can watch a horse galloping , but your eyes ca n't keep up with its fast-moving hooves enough to figure out whether all four feet are ever off the ground simultaneously . for these types of questions , we need cameras . about 150 years ago , the photographer eadweard muybridge used one to solve the galloping horse mystery . using careful photography , muybridge proved that at certain points as it gallops , a horse really is flying . `` look , ma ! no hooves ! '' since then , photography has found its way into all aspects of math and science . it enhances our understanding of a world we thought we could already see , but it 's one which we really need help to see a little better . it 's not always a matter of the world moving by too quickly for our eyes to process . sometimes cameras can help us see matter or movements that are too small for the naked eye . botanists use multiple photographs to show the life cycle of plants and how flowers turn over the course of a few hours to follow the sun in what is called phototropism , growing towards the light . mathematicians have used photos to look at where in the twists and turns of a whip the crack sound comes when the whip is breaking the sound barrier . meteorologists and environmental scientists show the growth of major hurricanes and the recession over the years of many of the world 's glaciers . slow-motion film or high-speed photography have shown us the beating of a hummingbird 's wings and the course of a bullet through its target . in one project , cadavers , that 's dead bodies , were frozen and sliced into thousands of wafer-thin discs . the discs were photographed to produced animated movies that allow a viewer to travel up and down the skeleton , and into the flesh , and through the bones , and the veins , and , perhaps i should have suggested you do n't watch this during dinner , my bad . in classrooms today , the camera , now present in just about every phone and computer , allows the youngest scientists to observe the world around them , to document it , and to share their findings online . whether it 's the change of seasons or the growth of the germinating seed , cameras are allowing us to see a beautiful world through new eyes .
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botanists use multiple photographs to show the life cycle of plants and how flowers turn over the course of a few hours to follow the sun in what is called phototropism , growing towards the light . mathematicians have used photos to look at where in the twists and turns of a whip the crack sound comes when the whip is breaking the sound barrier . meteorologists and environmental scientists show the growth of major hurricanes and the recession over the years of many of the world 's glaciers .
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who used photos to show how horses run ?
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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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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 .
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which social dance was born from slaves ’ experience on the plantation ?
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translator : andrea mcdonough reviewer : bedirhan cinar the oval office , inauguration day , rose garden signings , and secret service agents with dark sunglasses and cool wrist radios . for a moment , forget all of it . toss out everything you know about the president . now , start over . what would you do if you had to invent the president ? that was the question facing the 55 men who got together in secret to draw up the plans for a new american government in the summer of 1787 in philadelphia , in the same place where the declaration of independence had been written eleven years earlier . declaring independence had been risky business , demanding ferocious courage that put lives and fortunes in jeopardy . but , inventing a new government was no field day either , especially when it 's summer and you 're in scratchy suits , and the windows are closed because you do n't want anybody to hear what you are saying , and the air conditioning does n't work because it wo n't be invented for nearly 200 years . and , when you do n't agree on things , it gets even hotter . for the framers , the question they argued over most while writing the constitution and creating three branches of government had to do with the executive department . one man or three to do the job ? how long should he serve ? what would he really do ? who would pick him ? how to get rid of him if he 's doing a bad job or he 's a crook ? and , of course , they all meant him , and he would be a white man . the idea of a woman or an african american , for instance , holding this high office was not a glimmer in their eyes . but the framers knew they needed someone who could take charge , especially in a crisis , like an invasion or a rebellion , or negotiating treaties . congress was not very good at making such important decisions without debates and delays . but the framers thought america needed a man who was decisive and could act quickly . they called it energy and dispatch . one thing they were dead-set against : there would be no king . they had fought a war against a country with a monarch and were afraid that one man with unchecked powers , in charge of an army , could take over the country . instead , they settled on a president and laid out his powers in article 2 of the constitution . but who would choose him ? not the people , they were too liable to be misled as one framer worried . not the legislature , that would lead to cabal and factions . got it : electors , wise , informed men who have time to make a good decision . and if they did n't produce a winner , then the decision would go to one of the other branches of government , the congress . the house of representatives would step in and make the choice , which they did in 1801 and 1825 . in the long , hot summer of 1787 , compromises were made to invent the presidency , like counting slaves as 3/5 of a person , giving the president command of the army but congress the power to declare war , and unlimited four-year terms . since then , some of those compromises have been amended and the men in office have sometimes been too strong or too weak . but , if you could start from scratch , how would you redesign the oval office ?
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for a moment , forget all of it . toss out everything you know about the president . now , start over .
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the electoral college was created in 1787 to avoid direct election of the president by the voters . is that system still a good idea , or should it be changed ? how ?
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translator : jessica ruby reviewer : caroline cristal they 're long and slithery , and they 're not very colorful . but they do have a strange beauty of their own . their sinuous , nocturnal movements through the water are mesmerizing to watch . and though they may resemble underwater snakes , eels are , in fact , a very interesting type of fish . there are several things about eels that make them unique besides their elongated shape and limbless bodies . for one thing , eels have the ability to breathe through their skin . some can even leave the water and move over land for short periods . and , unlike most migratory fish , such as salmon , which spawn in fresh water but live their adult lives in salt water , eels of the genus anguilla migrate in the opposite direction , spawning and breeding in oceans and seas , while spending most of their intervening time in fresh water . if we were to take one such fresh water eel and follow its life story , it would be born in the middle of the north atlantic ocean , about a thousand miles east of bermuda . this area , called the sargasso sea , forms the western part of a subtropical gyre , a giant whirlpool in the middle of the ocean . our eel , let 's call it eli , would begin as one of ten to twenty million tiny eggs , carried by a female eel , hatching into a transparent leaf-shaped thing that looks nothing like an adult eel . eli starts to drift in ocean currents , predominantly the gulf stream towards either europe or north america , depending on its particular species . upon reaching the coast , eli is about two inches long , looking more eely but still transparent , known at this stage as a glass eel . but within a couple of days in fresh water , eli 's skin becomes pigmented a brownish-black , now looking more like that of an adult eel . you might notice that we have n't mentioned anything about eli 's gender yet . that 's because this is only determined once an eel enters fresh water , though nobody is sure exactly how that happens . most of the eels that stay in the estuaries and brackish water become males , while those that go upstream become females , growing up to two to three times bigger than their future mates . in this case , it turns out that eli was actually short for elaine . as a female eel , elaine will be quite solitary for most of her life in the stream , eating whatever falls in the water : grasshoppers , crickets , small fish , insect larvae , frogs , baby birds , almost anything she can get her mouth around . and she will grow quite big , up to four feet long and weighing as much as thirteen pounds . we do n't know exactly how fresh water eels know when it 's time to return to the ocean , but something calls to them . and their fall migration is one of the largest unseen migrations on the planet . as elaine leaves fresh water for the ocean , she undergoes a shocking metamorphosis . her eyes enlarge by about ten times , her skin gets thicker , and her fins get larger . these are most likely adaptations for their upcoming ocean travel , and elaine seamlessly makes the transition from fresh to salt water , which would be toxic for most other fish . once elaine leaves the mouth of the fresh water streams , she will disappear completely from human view . no one has witnessed , or been able to follow , an adult eel on their migration , nor do we know how deep they spawn . but it 's assumed that they can follow some signs that they can detect , such as a thermal barrier between ocean currents or a salinity front , in order to return to the same area of the ocean where they were born . because we do n't even know exactly what happens during an eel 's migration , we can only imagine what the actual breeding looks like . but the common hypothesis is that elaine and thousands , or hundreds of thousands , of other eels gather in large , intertwined masses and release their eggs and sperm in a giant orgy known as panmixia . a couple of days after the eggs are laid , they hatch , and the cycle begins again . and because we 've never seen the adult eels returning up the fresh water rivers , we must assume that , having completed their long and roundabout journey , these amazing and mysterious creatures finally die there , in the same place where they were born . goodbye , elaine ! it was a pleasure knowing you .
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there are several things about eels that make them unique besides their elongated shape and limbless bodies . for one thing , eels have the ability to breathe through their skin . some can even leave the water and move over land for short periods .
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eels have what incredible ability ?
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germanium is the first element in the periodic table , beginning at hydrogen , that ’ s named after a country : it is named after germany . there are other elements named after france and poland and america but we will come to those later . one of the things about germanium and what really makes it important in the periodic table is that this is one of the elements which was unknown when mendeleev constructed the periodic table and he predicted its existence and when it was found it had many of the properties that he had predicted based on the change in properties as you go down and across the periodic table . so this is a small sample of germanium , named after germany , so you can see the wonderful shiny surfaces . germanium is used quite widely as a so-called semi- conducting material . if you look at it in visible light it looks like a metal . germanium na , na , n-na na . i have used germanium mirrors in some of my experiments . the lasers that i used when i was younger had a germanium mirror that let the light out at the front of it and germanium is used quite widely in electronics . this is quite a nice piece of germanium . unfortunately i broke it somewhat earlier in my career , but you can see very nicely how this material looks like a piece of metal but on the other hand if you shine infrared light through it , it ’ s transparent so the infrared light will through but visible light doesn ’ t .
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germanium is the first element in the periodic table , beginning at hydrogen , that ’ s named after a country : it is named after germany . there are other elements named after france and poland and america but we will come to those later .
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like scandium and gallium , germanium was predicted to exist by mendeleev . what was the name he gave to that undiscovered element at the time ?
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the epic poem `` la dragontea '' describes how english explorer sir francis drake sailed across the gulf of venezuela in 1595 . he was aiming for the nearby lake maracaibo , home to a colony of spanish settlers he planned to overthrow . but as drake moved towards the mouth of the lake under cover of darkness , his plot was suddenly and magnificently foiled . huge flashes of lightning illuminated the landscape , exposing the fleet as if it were daytime , which warned the spanish about his approach . lake maracaibo is the stormiest place on the planet . the massive body of water at over 13,000 square kilometers is a place of almost perpetual storming . thunderstorms rage above it for up to 200 days of the year , each earsplitting event lasting for several hours . like everywhere else on earth , lightning at lake maracaibo is the result of opposing electrical charges that steadily build up inside storm clouds . once there 's a large enough difference between charges either within the cloud or between the clouds and the earth below , it forms a spark that becomes a lightning bolt . lightning strikes the earth about 350 million times per year , averaging out to eleven strikes a second . we know that thanks to satellites up in space and sensors on the ground . we can also measure the earth 's lightning density , which is the frequency with which lightning flashes in a square kilometer . knowing where lightning strikes and how often reveals the most lightning-rich places on earth . in the polar regions , there may only be one strike per several square kilometers each year . meanwhile , lightning density at the equator averages out to tens of flashes per square kilometer on account of the sun providing more heat to drive storms . yet nowhere can quite compare with lake maracaibo , where lightning strikes an average 250 times per square kilometer , giving it the highest lightning density of any place on earth . a number of factors converge to create the lake 's seemingly everlasting storms . firstly , lake maracaibo lies just ten degrees north of the equator , so there 's a wealth of solar energy available to fuel the storms . thunderstorms also require a supply of water vapor to feed on , and having the warm waters of the caribbean so close by provides an endless supply . finally , the lake 's southern and western edges are bordered by two massive mountain ranges , and as cool winds surge down these slopes , they force up warm air , destabilizing the atmosphere and causing storm clouds to form . together , these ingredients combine to give rise to the most awe-inspiring thunderstorms on the planet , a true sight to behold . centuries ago , sir francis drake may have cursed the lake 's intense illumination , but today , sailors actually embrace this phenomenon . they call it the maracaibo beacon , and use it as a natural lighthouse to illuminate their path across the seas .
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finally , the lake 's southern and western edges are bordered by two massive mountain ranges , and as cool winds surge down these slopes , they force up warm air , destabilizing the atmosphere and causing storm clouds to form . together , these ingredients combine to give rise to the most awe-inspiring thunderstorms on the planet , a true sight to behold . centuries ago , sir francis drake may have cursed the lake 's intense illumination , but today , sailors actually embrace this phenomenon .
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climate scientists predict that average temperatures across the planet are very likely to increase in the next 100 years . what do think this will mean for the frequency and intensity of thunderstorms ?
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when we think of classic works of art , the most common setting we imagine them in is a museum . but what we often forget is that much of this art was not produced with a museum setting in mind . what happens to an artwork when it 's taken out of its originally intended context ? take the example of michelangelo 's statue of david , depicting the boy hero who slew the giant philistine , goliath , armed with only his courage and his slingshot . when michelangelo began carving a block of pure white marble to communicate this famous biblical story , the city of florence intended to place the finished product atop their grand cathedral . not only would the 17 foot tall statue be easily visible at this height , but its placement alongside 11 other statues of old testament heroes towering over onlookers would have a powerful religious significance , forcing the viewer to stare in awe towards the heavens . but by the time michelangelo had finished the work , in 1504 , the plans for the other statues had fallen through , and the city realized that lifting such a large sculpture to the roof would be more difficult than they had thought . furthermore , the statue was so detailed and lifelike , down to the bulging veins in david 's arm and the determination on his face , that it seemed a shame to hide it so far from the viewer . a council of politicians and artists convened to decide on a new location for the statue . ultimately voting to place it in front of the palazzo della signoria , the town hall and home of the new republican government . this new location transformed the statue 's meaning . the medici family , who for generations had ruled the city through their control of banking , had recently been exiled , and florence now saw itself as a free city , threatened on all sides by wealthy and powerful rivals . david , now the symbol of heroic resistance against overwhelming odds , was placed with his intense stare , now a look of stern warning , focused directly towards rome , the home of cardinal giovanni de medici . though the statue itself had not been altered , its placement changed nearly every aspect of it from a religious to a political significance . though a replica of david still appears at the palazzo , the original statue was moved in 1873 to the galleria dell'accademia , where it remains today . in the orderly , quiet environment of the museum , alongside numerous half-finished michelangelo sculptures , overt religious and political interpretations fall away , giving way to detached contemplation of michelangelo 's artistic and technical skill . but even here , the astute viewer may notice that david 's head and hand appear disproportionately large , a reminder that they were made to be viewed from below . so , not only does context change the meaning and interpretation of an artwork throughout its history , sometimes it can make that history resurface in the most unexpected ways .
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ultimately voting to place it in front of the palazzo della signoria , the town hall and home of the new republican government . this new location transformed the statue 's meaning . the medici family , who for generations had ruled the city through their control of banking , had recently been exiled , and florence now saw itself as a free city , threatened on all sides by wealthy and powerful rivals .
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can you think of any other artistic pieces that change meaning as they change location ? what about duchamp ’ s fountain or picasso ’ s guernica ? what significance is added by the original locations ?
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the sun is shining . the birds are singing . it looks like the start of another lovely day . you 're walking happily in the park , when , `` ah-choo ! '' a passing stranger has expelled mucus and saliva from their mouth and nose . you can feel the droplets of moisture land on your skin , but what you ca n't feel are the thousands , or even millions , of microscopic germs that have covertly traveled through the air and onto your clothing , hands and face . as gross as this scenario sounds , it 's actually very common for our bodies to be exposed to disease-causing germs , and most of the time , it 's not nearly as obvious . germs are found on almost every surface we come into contact with . when we talk about germs , we 're actually referring to many different kinds of microscopic organisms , including bacteria , fungi , protozoa and viruses . but what our germs all have in common is the ability to interact with our bodies and change how we feel and function . scientists who study infectious diseases have wondered for decades why it is that some of these germs are relatively harmless , while others cause devastating effects and can sometimes be fatal . we still have n't solved the entire puzzle , but what we do know is that the harmfulness , or virulence , of a germ is a result of evolution . how can it be that the same evolutionary process can produce germs that cause very different levels of harm ? the answer starts to become clear if we think about a germ 's mode of transmission , which is the strategy it uses to get from one host to the next . a common mode of transmission occurs through the air , like the sneeze you just witnessed , and one germ that uses this method is the rhinovirus , which replicates in our upper airways , and is responsible for up to half of all common colds . now , imagine that after the sneeze , one of three hypothetical varieties of rhinovirus , let 's call them `` too much , '' `` too little , '' and `` just right , '' has been lucky enough to land on you . these viruses are hardwired to replicate , but because of genetic differences , they will do so at different rates . `` too much '' multiplies very often , making it very successful in the short run . however , this success comes at a cost to you , the host . a quickly replicating virus can cause more damage to your body , making cold symptoms more severe . if you 're too sick to leave your home , you do n't give the virus any opportunities to jump to a new host . and if the disease should kill you , the virus ' own life cycle will end along with yours . `` too little , '' on the other hand , multiplies rarely and causes you little harm in the process . although this leaves you healthy enough to interact with other potential hosts , the lack of symptoms means you may not sneeze at all , or if you do , there may be too few viruses in your mucus to infect anyone else . meanwhile , `` just right '' has been replicating quickly enough to ensure that you 're carrying sufficient amounts of the virus to spread but not so often that you 're too sick to get out of bed . and in the end , it 's the one that will be most successful at transmitting itself to new hosts and giving rise to the next generation . this describes what scientists call trade-off hypothesis . first developed in the early 1980s , it predicts that germs will evolve to maximize their overall success by achieving a balance between replicating within a host , which causes virulence , and transmission to a new host . in the case of the rhinovirus , the hypothesis predicts that its evolution will favor less virulent forms because it relies on close contact to get to its next victim . for the rhinovirus , a mobile host is a good host , and indeed , that is what we see . while most people experience a runny nose , coughing and sneezing , the common cold is generally mild and only lasts about a week . it would be great if the story ended there , but germs use many other modes of transmission . for example , the malaria parasite , plasmodium , is transmitted by mosquitoes . unlike the rhinovirus , it does n't need us to be up and about , and may even benefit from harming us since a sick and immobile person is easier for mosquitoes to bite . we would expect germs that depend less on host mobility , like those transmitted by insects , water or food , to cause more severe symptoms . so , what can we do to reduce the harmfulness of infectious diseases ? evolutionary biologist dr. paul ewald has suggested that we can actually direct their evolution through simple disease-control methods . by mosquito-proofing houses , establishing clean water systems , or staying home when we get a cold , we can obstruct the transmission strategies of harmful germs while creating a greater dependence on host mobility . so , while traditional methods of trying to eradicate germs may only breed stronger ones in the long run , this innovative approach of encouraging them to evolve milder forms could be a win-win situation . ( cough ) well , for the most part .
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as gross as this scenario sounds , it 's actually very common for our bodies to be exposed to disease-causing germs , and most of the time , it 's not nearly as obvious . germs are found on almost every surface we come into contact with . when we talk about germs , we 're actually referring to many different kinds of microscopic organisms , including bacteria , fungi , protozoa and viruses . but what our germs all have in common is the ability to interact with our bodies and change how we feel and function . scientists who study infectious diseases have wondered for decades why it is that some of these germs are relatively harmless , while others cause devastating effects and can sometimes be fatal . we still have n't solved the entire puzzle , but what we do know is that the harmfulness , or virulence , of a germ is a result of evolution .
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germs include :
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like many heroes of greek myths , the philosopher hippasus was rumored to have been mortally punished by the gods . but what was his crime ? did he murder guests , or disrupt a sacred ritual ? no , hippasus 's transgression was a mathematical proof : the discovery of irrational numbers . hippasus belonged to a group called the pythagorean mathematicians who had a religious reverence for numbers . their dictum of , `` all is number , '' suggested that numbers were the building blocks of the universe and part of this belief was that everything from cosmology and metaphysics to music and morals followed eternal rules describable as ratios of numbers . thus , any number could be written as such a ratio . 5 as 5/1 , 0.5 as 1/2 and so on . even an infinitely extending decimal like this could be expressed exactly as 34/45 . all of these are what we now call rational numbers . but hippasus found one number that violated this harmonious rule , one that was not supposed to exist . the problem began with a simple shape , a square with each side measuring one unit . according to pythagoras theorem , the diagonal length would be square root of two , but try as he might , hippasus could not express this as a ratio of two integers . and instead of giving up , he decided to prove it could n't be done . hippasus began by assuming that the pythagorean worldview was true , that root 2 could be expressed as a ratio of two integers . he labeled these hypothetical integers p and q . assuming the ratio was reduced to its simplest form , p and q could not have any common factors . to prove that root 2 was not rational , hippasus just had to prove that p/q can not exist . so he multiplied both sides of the equation by q and squared both sides . which gave him this equation . multiplying any number by 2 results in an even number , so p^2 had to be even . that could n't be true if p was odd because an odd number times itself is always odd , so p was even as well . thus , p could be expressed as 2a , where a is an integer . substituting this into the equation and simplifying gave q^2 = 2a^2 once again , two times any number produces an even number , so q^2 must have been even , and q must have been even as well , making both p and q even . but if that was true , then they had a common factor of two , which contradicted the initial statement , and that 's how hippasus concluded that no such ratio exists . that 's called a proof by contradiction , and according to the legend , the gods did not appreciate being contradicted . interestingly , even though we ca n't express irrational numbers as ratios of integers , it is possible to precisely plot some of them on the number line . take root 2 . all we need to do is form a right triangle with two sides each measuring one unit . the hypotenuse has a length of root 2 , which can be extended along the line . we can then form another right triangle with a base of that length and a one unit height , and its hypotenuse would equal root three , which can be extended along the line , as well . the key here is that decimals and ratios are only ways to express numbers . root 2 simply is the hypotenuse of a right triangle with sides of a length one . similarly , the famous irrational number pi is always equal to exactly what it represents , the ratio of a circle 's circumference to its diameter . approximations like 22/7 , or 355/113 will never precisely equal pi . we 'll never know what really happened to hippasus , but what we do know is that his discovery revolutionized mathematics . so whatever the myths may say , do n't be afraid to explore the impossible .
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even an infinitely extending decimal like this could be expressed exactly as 34/45 . all of these are what we now call rational numbers . but hippasus found one number that violated this harmonious rule , one that was not supposed to exist .
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what are rational numbers ?
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we all know the scene : dorothy closes her eyes , and repeats the good witch 's mantra , `` no coordinates exist like one 's domicile , no coordinates exist like one 's domicile , no coordinates exist like one 's domicile . '' only dorothy does n't say that . she says five one-syllable words , `` there 's no place like home . '' each a word you probably learned in your first year of speaking , each perfectly concise . it 's not that l. frank baum did n't have a thesaurus , it 's that in most cases $ 10 words fail . would aerosmith have had a hit with `` ambulate this direction ? '' probably not . would patrick henry have ignited a revolution by saying , `` provide me with liberty or bestow upon me fatality ? '' unlikely . when it comes to words , bigger is n't always better . ten-dollar words are rendered worthless if they 're not understood . that 's not to say every piece of literature should be written at a fourth-grade reading level , but it is important to know your audience . if you 're a novelist , your audience is probably expecting 300 pages of vivid descriptors . at the very least , they 're expecting you wo n't use the same 50 words to fill those pages . but most of us do n't have the luxury of a captive audience . we 're competing against a whole world of distractions and we 're fighting for space in an attention span that continues to shrink across generations . so get to the point already . variety may be the spice of life , but brevity is its bread and butter . so when it comes to $ 10 words , save your money and buy a scrabble board .
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but most of us do n't have the luxury of a captive audience . we 're competing against a whole world of distractions and we 're fighting for space in an attention span that continues to shrink across generations . so get to the point already .
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the author thinks that speakers and writers are “ fighting for space in an attention span that continues to shrink across generations. ” what does she mean by this , and do you think it ’ s true ? if it is true , what ’ s driving it , and is it necessarily a bad thing ? if it ’ s false , why do you think the author ( and other people too ) have this impression ?
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when you hear the word art , what comes to mind ? a painting , like the mona lisa , or a famous sculpture or a building ? what about a vase or a quilt or a violin ? are those things art , too , or are they craft ? and what 's the difference anyway ? it turns out that the answer is not so simple . a spoon or a saddle may be finely wrought , while a monument may be , well , uninspired . just as not every musical instrument is utilitarian , not every painting or statue is made for its own sake . but if it 's so tricky to separate art from craft , then why do we distinguish objects in this way ? you could say it 's the result of a dramatic historical turn of events . it might seem obvious to us today to view people , such as da vinci or michelangelo , as legendary artists , and , of course , they possessed extraordinary talents , but they also happened to live in the right place at the right time , because shortly before their lifetimes the concept of artists hardly existed . if you had chanced to step into a medieval european workshop , you would have witnessed a similar scene , no matter whether the place belonged to a stonemason , a goldsmith , a hatmaker , or a fresco painter . the master , following a strict set of guild statutes , insured that apprentices and journeymen worked their way up the ranks over many years of practice and well-defined stages of accomplishment , passing established traditions to the next generation . patrons regarded these makers collectively rather than individually , and their works from murano glass goblets , to flemish lace , were valued as symbols of social status , not only for their beauty , but their adherence to a particular tradition . and the customer who commissioned and paid for the work , whether it was a fine chair , a stone sculpture , a gold necklace , or an entire building , was more likely to get credit than those who designed or constructed it . it was n't until around 1400 that people began to draw a line between art and craft . in florence , italy , a new cultural ideal that would later be called renaissance humanism was beginning to take form . florentine intellectuals began to spread the idea of reformulating classical greek and roman works , while placing greater value on individual creativity than collective production . a few brave painters , who for many centuries , had been paid by the square foot , successfully petitioned their patrons to pay them on the basis of merit instead . within a single generation , people 's attitudes about objects and their makers would shift dramatically , such that in 1550 , giorgio vasari , not incidentally a friend of michelangelo , published an influential book called , `` lives of the most excellent painters , sculptors and architects , '' elevating these types of creators to rock star status by sharing juicy biographical details . in the mind of the public , painting , sculpture and architecture were now considered art , and their makers creative masterminds : artists . meanwhile , those who maintained guild traditions and faithfully produced candelsticks , ceramic vessels , gold jewelery or wrought iron gates , would be known communally as artisans , and their works considered minor or decorative arts , connoting an inferior status and solidifying the distinction between art and craft that still persists in the western world . so , if we consider a painting by rembrandt or picasso art , then where does that leave an african mask ? a chinese porclein vase ? a navajo rug ? it turns out that in the history of art , the value placed on innovation is the exception rather than the rule . in many cultures of the world , the distinction between art and craft has never existed . in fact , some works that might be considered craft , a peruvian rug , a ming dynasty vase , a totem pole , are considered the cultures ' preeminent visual forms . when art historians of the 19th century saw that the art of some non-western cultures did not change for thousands of years , they classified the works as primitive , suggesting that their makers were incapable of innovating and therefore were not really artists . what they did n't realize was that these makers were not seeking to innovate at all . the value of their works lay precisely in preserving visual traditions , rather than in changing them . in the last few decades , works such as quilts , ceramics and wood carvings have become more prominently included in art history textbooks and displayed in museums alongside paintings and sculpture . so maybe it 's time to dispense with vague terms like art and craft in favor of a word like visual arts that encompasses a wider array of aesthetic production . after all , if our appreciation of objects and their makers is so conditioned by our culture and history , then art and its definition are truly in the eye of the beholder .
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it was n't until around 1400 that people began to draw a line between art and craft . in florence , italy , a new cultural ideal that would later be called renaissance humanism was beginning to take form . florentine intellectuals began to spread the idea of reformulating classical greek and roman works , while placing greater value on individual creativity than collective production .
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before the renaissance , there was no concept of ________ .
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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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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 .
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what is the role of mitochondria in aging ?
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today we 're talking about weird materials that we use in space , in robots and in your mouth . i 'm talking about shape memory alloys . like the name says , these are metals that remember different shapes . to understand how these metals work , we 've got to talk about atoms and organizing . let 's talk about atoms first . atoms are tiny bits of matter that you can not see with your eye yet they make up everything in our world , from the chair that you 're sitting on to your cell phone . atoms have some surprising ways of behaving too . we 'll talk about that shortly . now , how big is an atom ? well , imagine pulling one of your hairs out of your head and whittling it like a stick 100,000 times . one of those shavings would be the width of an atom . they 're that small . now let 's talk about atoms and organizing . you may not know this , but atoms arrange themselves similar to the way we humans arrange ourselves . sometimes they sit in rows , like we do on a bus or an airplane . we call that seating arrangement a phase . other times they sit diagonal from each other , sort of like seats in a movie theater or sports stadium . this is another phase . when atoms move from one seating to another this is called a phase change . phase changes are all around us . you may already know about water 's phases : solid , liquid and gas . many other materials have phases like that too . some of them have several solid phases . ok. back to those shape memory alloys we mentioned before . when we say that the metals remember their different shapes , what we 're really saying is they remember different seating arrangements of atoms . when the atoms rearrange , the metal moves from one shape to another . let 's look at a phase change in action . here i have a metal wire that is made out of nickel and titanium . this metal wire is a shape memory alloy , and i 'm going to make it switch between its different shapes using heat from a lighter . watch this . i 'm going to wrap this wire around my finger and then heat it . amazing ! that wire returns to a straight line , when i heat it . let 's try that again . i 'm going to wrap it around my finger , and heat it . yep , that 's still amazing . not only is it amazing , this is weird , because metals generally do n't do that . here 's a paper clip . when i heat it , i get nothing . what we 're seeing is the shape memory wire changing phases when it gets hot . when the wire is cold , atoms are in a diagonal arrangement , like the movie theater seating , we talked about before . we call this a monoclinic arrangement , and scientists will call this phase martensite . when i heated up the wire , the atoms moved into columns like airplane seating . this is a cubic arrangement . scientists will call this phase austenite . so when we added the heat , the atoms shifted positions seamlessly , and they 'll do this forever . they have this coordinated motion , just like members of a tireless marching band . each makes a small shift , but all together those small shifts create a totally different pattern . so that 's pretty cool , but where do we use these materials ? well , if you look in the sky tonight , shape memory alloys are at work - on mars . they 're used to move panels on the mars rover , so that it can study the environment . like our metal straightened when it was heated , the metals holding the panels will move when electrically heated . when we stop heating the shape memory metal , the panel will return back , due to an opposing spring . back on earth , shape memory alloys are used to open up clogged arteries as stents , which are small collapsible springs that force open passages . shape memory alloys are also used to move robots , toy butterflies , teeth in braces , and for a perfect fit every time , shape memory wires are used as underwires in bras . now you know victoria 's secret . by popping a bra into the dryer , it 'll be brand new every time . so whether it 's on mars or in your mouth , small atomic movements can create huge changes , and understanding the way atoms behave allows us to make materials that make our world a better place .
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today we 're talking about weird materials that we use in space , in robots and in your mouth . i 'm talking about shape memory alloys . like the name says , these are metals that remember different shapes .
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how do the different phases in shape memory alloys differ ?
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prolonged space travel takes a severe toll on the human body . microgravity impairs muscle and bone growth , and high doses of radiation cause irreversible mutations . as we seriously consider the human species becoming space-faring , a big question stands . even if we break free from earth 's orbit and embark on long-duration journeys among the stars , can we adapt to the extreme environments of space ? this wo n't be the first time that humans have adapted to harsh environments and evolved superhuman capabilities . not fantastical powers like laser vision or invisibility , but physiological adaptations for survival in tough conditions . for example , on the himalayan mountains where the highest elevation is nine kilometers above sea level , an unacclimated lowland human will experience symptoms of hypoxia , commonly known as mountain sickness . at these altitudes , the body usually produces extra red blood cells , thickening the blood and impeding its flow . but himalayans who have lived on these mountains for thousands of years permanently evolved mechanisms to circumvent this process and maintain normal blood flow . cases like that prove that humans can develop permanent lifesaving traits . but natural adaptation for entire human populations could take tens of thousands of years . recent scientific advances may help us accelerate human adaptation to single generations . to thrive as a species during space travel , we could potentially develop methods to quickly program protective abilities into ourselves . a beta version of these methods is gene therapy , which we can currently use to correct genetic diseases . gene editing technology , which is improving rapidly , allows scientists to directly change the human genome to stop undesirable processes or make helpful substances . an example of an unwanted process is what happens when our bodies are exposed to ionizing radiation . without an atmospheric barrier and a magnetic field like earth 's , most planets and moons are bombarded with these dangerous subatomic particles . they can pass through nearly anything and would cause potentially cancerous dna damage to space explorers . but what if we could turn the tables on radiation ? human skin produces a pigment called melanin that protects us from the filtered radiation on earth . melanin exists in many forms across species , and some melanin-expressing fungi use the pigment to convert radiation into chemical energy . instead of trying to shield the human body , or rapidly repair damage , we could potentially engineer humans to adopt and express these fungal , melanin-based energy-harvesting systems . they 'd then convert radiation into useful energy while protecting our dna . this sounds pretty sci-fi , but may actually be achievable with current technology . but technology is n't the only obstacle . there are ongoing debates on the consequences and ethics of such radical alterations to our genetic fabric . besides radiation , variation in gravitational strength is another challenge for space travelers . until we develop artificial gravity in a space ship or on another planet , we should assume that astronauts will spend time living in microgravity . on earth , human bone and muscle custodial cells respond to the stress of gravity 's incessant tugging by renewing old cells in processes known as remodeling and regeneration . but in a microgravity environment like mars , human bone and muscle cells wo n't get these cues , resulting in osteoporosis and muscle atrophy . so , how could we provide an artificial signal for cells to counteract bone and muscle loss ? again , this is speculative , but biochemically engineered microbes inside our bodies could churn out bone and muscle remodeling signaling factors . or humans could be genetically engineered to produce more of these signals in the absence of gravity . radiation exposure and microgravity are only two of the many challenges we will encounter in the hostile conditions of space . but if we 're ethically prepared to use them , gene editing and microbial engineering are two flexible tools that could be adapted to many scenarios . in the near future , we may decide to further develop and tune these genetic tools for the harsh realities of space living .
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radiation exposure and microgravity are only two of the many challenges we will encounter in the hostile conditions of space . but if we 're ethically prepared to use them , gene editing and microbial engineering are two flexible tools that could be adapted to many scenarios . in the near future , we may decide to further develop and tune these genetic tools for the harsh realities of space living .
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gene therapy and microbial engineering are two biological tools that have helped alleviate human diseases . what are some ways that astronauts might benefit from biotechnology ?
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the sun is shining . the birds are singing . it looks like the start of another lovely day . you 're walking happily in the park , when , `` ah-choo ! '' a passing stranger has expelled mucus and saliva from their mouth and nose . you can feel the droplets of moisture land on your skin , but what you ca n't feel are the thousands , or even millions , of microscopic germs that have covertly traveled through the air and onto your clothing , hands and face . as gross as this scenario sounds , it 's actually very common for our bodies to be exposed to disease-causing germs , and most of the time , it 's not nearly as obvious . germs are found on almost every surface we come into contact with . when we talk about germs , we 're actually referring to many different kinds of microscopic organisms , including bacteria , fungi , protozoa and viruses . but what our germs all have in common is the ability to interact with our bodies and change how we feel and function . scientists who study infectious diseases have wondered for decades why it is that some of these germs are relatively harmless , while others cause devastating effects and can sometimes be fatal . we still have n't solved the entire puzzle , but what we do know is that the harmfulness , or virulence , of a germ is a result of evolution . how can it be that the same evolutionary process can produce germs that cause very different levels of harm ? the answer starts to become clear if we think about a germ 's mode of transmission , which is the strategy it uses to get from one host to the next . a common mode of transmission occurs through the air , like the sneeze you just witnessed , and one germ that uses this method is the rhinovirus , which replicates in our upper airways , and is responsible for up to half of all common colds . now , imagine that after the sneeze , one of three hypothetical varieties of rhinovirus , let 's call them `` too much , '' `` too little , '' and `` just right , '' has been lucky enough to land on you . these viruses are hardwired to replicate , but because of genetic differences , they will do so at different rates . `` too much '' multiplies very often , making it very successful in the short run . however , this success comes at a cost to you , the host . a quickly replicating virus can cause more damage to your body , making cold symptoms more severe . if you 're too sick to leave your home , you do n't give the virus any opportunities to jump to a new host . and if the disease should kill you , the virus ' own life cycle will end along with yours . `` too little , '' on the other hand , multiplies rarely and causes you little harm in the process . although this leaves you healthy enough to interact with other potential hosts , the lack of symptoms means you may not sneeze at all , or if you do , there may be too few viruses in your mucus to infect anyone else . meanwhile , `` just right '' has been replicating quickly enough to ensure that you 're carrying sufficient amounts of the virus to spread but not so often that you 're too sick to get out of bed . and in the end , it 's the one that will be most successful at transmitting itself to new hosts and giving rise to the next generation . this describes what scientists call trade-off hypothesis . first developed in the early 1980s , it predicts that germs will evolve to maximize their overall success by achieving a balance between replicating within a host , which causes virulence , and transmission to a new host . in the case of the rhinovirus , the hypothesis predicts that its evolution will favor less virulent forms because it relies on close contact to get to its next victim . for the rhinovirus , a mobile host is a good host , and indeed , that is what we see . while most people experience a runny nose , coughing and sneezing , the common cold is generally mild and only lasts about a week . it would be great if the story ended there , but germs use many other modes of transmission . for example , the malaria parasite , plasmodium , is transmitted by mosquitoes . unlike the rhinovirus , it does n't need us to be up and about , and may even benefit from harming us since a sick and immobile person is easier for mosquitoes to bite . we would expect germs that depend less on host mobility , like those transmitted by insects , water or food , to cause more severe symptoms . so , what can we do to reduce the harmfulness of infectious diseases ? evolutionary biologist dr. paul ewald has suggested that we can actually direct their evolution through simple disease-control methods . by mosquito-proofing houses , establishing clean water systems , or staying home when we get a cold , we can obstruct the transmission strategies of harmful germs while creating a greater dependence on host mobility . so , while traditional methods of trying to eradicate germs may only breed stronger ones in the long run , this innovative approach of encouraging them to evolve milder forms could be a win-win situation . ( cough ) well , for the most part .
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first developed in the early 1980s , it predicts that germs will evolve to maximize their overall success by achieving a balance between replicating within a host , which causes virulence , and transmission to a new host . in the case of the rhinovirus , the hypothesis predicts that its evolution will favor less virulent forms because it relies on close contact to get to its next victim . for the rhinovirus , a mobile host is a good host , and indeed , that is what we see .
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explain the statement , `` evolution favors the less virulent form because it relies on close contact to get to its next victim . ”
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can you grow a human bone outside the human body ? the answer may soon be yes , but before we can understand how that 's possible , we need to look at how bones grow naturally inside the body . most bones start in a growing fetus as a soft , flexible cartilage . bone-forming cells replace the cartilage with a spongy mineral lattice made of elements like calcium and phosphate . this lattice gets harder , as osteoblasts , which are specialized bone-forming cells , deposit more mineral , giving bones their strength . while the lattice itself is not made of living cells , networks of blood vessels , nerves and other living tissues grow through special channels and passages . and over the course of development , a legion of osteoblasts reinforce the skeleton that protects our organs , allows us to move , produces blood cells and more . but this initial building process alone is not enough to make bones strong and functional . if you took a bone built this way , attached muscles to it , and tried to use it to lift a heavy weight , the bone would probably snap under the strain . this does n't usually happen to us because our cells are constantly reinforcing and building bone wherever they 're used , a principle we refer to as wolff 's law . however , bone materials are a limited resource and this new , reinforcing bone can be formed only if there is enough material present . fortunately , osteoblasts , the builders , have a counterpart called osteoclasts , the recyclers . osteoclasts break down the unneeded mineral lattice using acids and enzymes so that osteoblasts can then add more material . one of the main reasons astronauts must exercise constantly in orbit is due to the lack of skeletal strain in free fall . as projected by wolff 's law , that makes osteoclasts more active than osteoblasts , resulting in a loss of bone mass and strength . when bones do break , your body has an amazing ability to reconstruct the injured bone as if the break had never happened . certain situations , like cancer removal , traumatic accidents , and genetic defects exceed the body 's natural ability for repair . historical solutions have included filling in the resulting holes with metal , animal bones , or pieces of bone from human donors , but none of these are optimal as they can cause infections or be rejected by the immune system , and they ca n't carry out most of the functions of healthy bones . an ideal solution would be to grow a bone made from the patient 's own cells that 's customized to the exact shape of the hole , and that 's exactly what scientists are currently trying to do . here 's how it works . first , doctors extract stem cells from a patient 's fat tissue and take ct scans to determine the exact dimensions of the missing bone . they then model the exact shape of the hole , either with 3d printers , or by carving decellularized cow bones . those are the bones where all of the cells have been stripped away , leaving only the sponge-like mineral lattice . they then add the patient 's stem cells to this lattice and place it in a bioreactor , a device that will simulate all of the conditions found inside the body . temperature , humidity , acidity and nutrient composition all need to be just right for the stem cells to differentiate into osteoblasts and other cells , colonize the mineral lattice , and remodel it with living tissue . but there 's one thing missing . remember wolff 's law ? an artificial bone needs to experience real stress , or else it will come out weak and brittle , so the bioreactor constantly pumps fluids around the bone , and the pressure tells the osteoblasts to add bone density . put all of this together , and within three weeks , the now living bone is ready to come out of the bioreactor and to be implanted into the patient 's body . while it is n't yet certain that this method will work for humans , lab grown bones have already been successfully implanted in pigs and other animals , and human trials may begin as early as 2016 .
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bone-forming cells replace the cartilage with a spongy mineral lattice made of elements like calcium and phosphate . this lattice gets harder , as osteoblasts , which are specialized bone-forming cells , deposit more mineral , giving bones their strength . while the lattice itself is not made of living cells , networks of blood vessels , nerves and other living tissues grow through special channels and passages .
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what gives bones their strength ?
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this is a crystal of sugar . if you press on it , it will actually generate its own electricity . how can this simple crystal act like a tiny power source ? because sugar is piezoelectric . piezoelectric materials turn mechanical stress , like pressure , sound waves , and other vibrations into electricity and vice versa . this odd phenomenon was first discovered by the physicist pierre curie and his brother jacques in 1880 . they discovered that if they compressed thin slices of certain crystals , positive and negative charges would appear on opposite faces . this difference in charge , or voltage , meant that the compressed crystal could drive current through a circuit , like a battery . and it worked the other way around , too . running electricity through these crystals made them change shape . both of these results , turning mechanical energy into electrical , and electrical energy into mechanical , were remarkable . but the discovery went uncelebrated for several decades . the first practical application was in sonar instruments used to detect german submarines during world war i. piezoelectric quartz crystals in the sonar 's transmitter vibrated when they were subjected to alternating voltage . that sent ultrasound waves through the water . measuring how long it took these waves to bounce back from an object revealed how far away it was . for the opposite transformation , converting mechanical energy to electrical , consider the lights that turn on when you clap . clapping your hands send sound vibrations through the air and causes the piezo element to bend back and forth . this creates a voltage that can drive enough current to light up the leds , though it 's conventional sources of electricity that keep them on . so what makes a material piezoelectric ? the answer depends on two factors : the materials atomic structure , and how electric charge is distributed within it . many materials are crystalline , meaning they 're made of atoms or ions arranged in an orderly three-dimensional pattern . that pattern has a building block called a unit cell that repeats over and over . in most non-piezoelectric crystalline materials , the atoms in their unit cells are distributed symmetrically around a central point . but some crystalline materials do n't possess a center of symmetry making them candidates for piezoelectricity . let 's look at quartz , a piezoelectric material made of silicon and oxygen . the oxygens have a slight negative charge and silicons have a slight positive , creating a separation of charge , or a dipole along each bond . normally , these dipoles cancel each other out , so there 's no net separation of charge in the unit cell . but if a quartz crystal is squeezed along a certain direction , the atoms shift . because of the resulting asymmetry in charge distribution , the dipoles no longer cancel each other out . the stretched cell ends up with a net negative charge on one side and a net positive on the other . this charge imbalance is repeated all the way through the material , and opposite charges collect on opposite faces of the crystal . this results in a voltage that can drive electricity through a circuit . piezoelectric materials can have different structures . but what they all have in common is unit cells which lack a center of symmetry . and the stronger the compression on piezoelectric materials , the larger the voltage generated . stretch the crystal , instead , and the voltage will switch , making current flow the other way . more materials are piezoelectric than you might think . dna , bone , and silk all have this ability to turn mechanical energy into electrical . scientists have created a variety of synthetic piezoelectric materials and found applications for them in everything from medical imaging to ink jet printers . piezoelectricity is responsible for the rhythmic oscillations of the quartz crystals that keep watches running on time , the speakers of musical birthday cards , and the spark that ignites the gas in some barbecue grill lighters when you flick the switch . and piezoelectric devices may become even more common since electricity is in high demand and mechanical energy is abundant . there are already train stations that use passengers ' footsteps to power the ticket gates and displays and a dance club where piezoelectricity helps power the lights . could basketball players running back and forth power the scoreboard ? or might walking down the street charge your electronic devices ? what 's next for piezoelectricity ?
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this results in a voltage that can drive electricity through a circuit . piezoelectric materials can have different structures . but what they all have in common is unit cells which lack a center of symmetry .
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which of the following is/are naturally occurring piezoelectric materials ?
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imagine a police lineup where ten witnesses are asked to identify a bank robber they glimpsed fleeing the crime scene . if six of them pick out the same person , there 's a good chance that 's the real culprit , and if all ten make the same choice , you might think the case is rock solid , but you 'd be wrong . for most of us , this sounds pretty strange . after all , much of our society relies on majority vote and consensus , whether it 's politics , business , or entertainment . so it 's natural to think that more consensus is a good thing . and up until a certain point , it usually is . but sometimes , the closer you start to get to total agreement , the less reliable the result becomes . this is called the paradox of unanimity . the key to understanding this apparent paradox is in considering the overall level of uncertainty involved in the type of situation you 're dealing with . if we asked witnesses to identify the apple in this lineup , for example , we should n't be surprised by a unanimous verdict . but in cases where we have reason to expect some natural variance , we should also expect varied distribution . if you toss a coin one hundred times , you would expect to get heads somewhere around 50 % of the time . but if your results started to approach 100 % heads , you 'd suspect that something was wrong , not with your individual flips , but with the coin itself . of course , suspect identifications are n't as random as coin tosses , but they 're not as clear cut as telling apples from bananas , either . in fact , a 1994 study found that up to 48 % of witnesses tend to pick the wrong person out of a lineup , even when many are confident in their choice . memory based on short glimpses can be unreliable , and we often overestimate our own accuracy . knowing all this , a unanimous identification starts to seem less like certain guilt , and more like a systemic error , or bias in the lineup . and systemic errors do n't just appear in matters of human judgement . from 1993-2008 , the same female dna was found in multiple crime scenes around europe , incriminating an elusive killer dubbed the phantom of heilbronn . but the dna evidence was so consistent precisely because it was wrong . it turned out that the cotton swabs used to collect the dna samples had all been accidentally contaminated by a woman working in the swab factory . in other cases , systematic errors arise through deliberate fraud , like the presidential referendum held by saddam hussein in 2002 , which claimed a turnout of 100 % of voters with all 100 % supposedly voting in favor of another seven-year term . when you look at it this way , the paradox of unanimity is n't actually all that paradoxical . unanimous agreement is still theoretically ideal , especially in cases when you 'd expect very low odds of variability and uncertainty , but in practice , achieving it in situations where perfect agreement is highly unlikely should tell us that there 's probably some hidden factor affecting the system . although we may strive for harmony and consensus , in many situations , error and disagreement should be naturally expected . and if a perfect result seems too good to be true , it probably is .
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but if your results started to approach 100 % heads , you 'd suspect that something was wrong , not with your individual flips , but with the coin itself . of course , suspect identifications are n't as random as coin tosses , but they 're not as clear cut as telling apples from bananas , either . in fact , a 1994 study found that up to 48 % of witnesses tend to pick the wrong person out of a lineup , even when many are confident in their choice .
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consider the same scenario , but that about 80 of your friends all agree on the number of apples , and about 20 come up with different numbers . how likely is that the 80 friends have got it right ?
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what 's the worst bug on the planet ? you might vote for the horsefly or perhaps the wasp , but for many people , the worst offender is by far the mosquito . the buzzing , the biting , the itching , the mosquito is one of the most commonly detested pests in the world . in alaska , swarms of mosquitos can get so thick that they actually asphyxiate caribou . and mosquito-borne diseases kill millions of people every year . the scourge that is the mosquito is n't new . mosquitoes have been around for over a hundred million years and over that time have coevolved with all sorts of species , including our own . there are actually thousands of species of mosquitos in the world , but they all share one insidious quality : they suck blood , and they 're really , really good at sucking blood . here 's how they do it . after landing , a mosquito will slather some saliva onto the victim 's skin , which works like an antiseptic , numbing the spot so we do n't notice their attack . this is what causes the itchy , red bumps , by the way . then the bug will use its serrated mandibles to carve a little hole in your skin , allowing it to probe around with its proboscis , searching for a blood vessel . when it hits one , the lucky parasite can suck two to three times its weight in blood . turns out we do n't really like that too much . in fact , humans hate mosquitos so much that we spend billions of dollars worldwide to keep them away from us -- from citronella candles to bug sprays to heavy-duty agricultural pesticides . but it 's not just that mosquitos are annoying , they 're also deadly . mosquitos can transmit everything from malaria to yellow fever to west nile virus to dengue . over a million people worldwide die every year from mosquito-borne diseases , and that 's just people . horses , dogs , cats , they can all get diseases from mosquitoes too . so , if these bugs are so dastardly , why do n't we just get rid of them ? we are humans after all , and we 're pretty good at getting rid of species . well , it 's not quite so simple . getting rid of the mosquito removes a food source for lots of organisms , like frogs and fish and birds . without them , plants would lose a pollinator . but some scientists say that mosquitos are n't actually all that important . if we got rid of them , they argue , another species would simply take their place and we 'd probably have far fewer deaths from malaria . the problem is that nobody knows what would happen if we killed off all the mosquitos . something better might take their spot or perhaps something even worse . the question is , are we willing to take that risk ? ( buzzing )
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mosquitoes have been around for over a hundred million years and over that time have coevolved with all sorts of species , including our own . there are actually thousands of species of mosquitos in the world , but they all share one insidious quality : they suck blood , and they 're really , really good at sucking blood . here 's how they do it .
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once a mosquito locates a blood vessel , how much blood can it consume ?
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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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`` last night i had a horrible nightmare ” , said the organic chemist to the theoretical one . “ i could see the blue color of liquid oxygen ! ” why is this beautiful liquid so feared by organic chemists ?
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if i were to distill the 20 years of elephant research that i 've done into one sentence , what would it be ? what could i tell you ? i would say that elephants are just like us ! and what do i mean by that ? it takes a lot of patience to be out there in the field and trying to figure out patterns of these very slow and intelligent animals . but over time , it is true they are very similar to us . and you think , `` well , how can i say that ? look , they have huge ears , they have really long noses . what do you mean they 're like us ? '' well , in fact , their families are very similar to ours . and family is extremely important to elephants . they grow up in very tight-knit families and they have extended families . and it 's just like our family reunions where you have all the aunts gathering around with all the food they 're going to bring and plan , and all the boys are thinking , `` are we going to play our video games together ? are we going to spar ? '' it 's very , very similar , and it 's jubilant , and screaming , yelling , it 's really amazing to see . but , as soon as you get that family gathering , it 's just like a wedding or anything else , all of the sudden the family politics come out , and the lower-ranking individuals in this scene , you see the arrow off to the back , the lower-ranking individuals already know their station , they 're going to drink at the muddiest part of the pan because the whole family 's here and we ca n't drink at the best water because that 's reserved for the top-ranking family . what 's also very similar is that you have elders in the group that everyone reveres . this is the matriarch , and the other female is reaching over and doing what 's called a trunk to mouth placing her trunk in the mouth , and it 's a sign of respect , it 's kind of like a handshake , but it 's also like a salute . and this salute is learned at a very young age . now , ritual and bonding within the family also facilitates coordinated activities . so , here 's a young female whose calf has fallen into the trough and she does n't know what to do and she panics . well , the older female , that 's the matriarch , she says , `` no problem here , '' she just scoops the baby out . now , that 's not true for a lot of different families , they ca n't coordinate very well , the younger females do n't really know what to do , but the older ones will just get down , kneel down together and pick the baby out . another thing that 's very similar is the coming of age of teenage boys . male elephants at the age of about 12 to 15 . the biggest elephant in this photograph here is an elephant who 's about the leave the family . he gets too big , he gets a little fresh , the adult females had enough of him , but he also is independent , he wants to go out and play with the guys . so what happens then is that you have this all male society , very ritual male society . greg is our main dominant bull here , you can see him in the middle . he 's got a huge posse , his following reveres him . and it 's very interesting how very good leaders , very good dominant individuals know how to titrate the carrot and the stick . this guy 's a master at it , and there 's other bullies out there that want to kind of want to create their own little following , but they ca n't do it because they 're too agressive . and so when he 's not around they try and sweet talk the underlings to come into their fold , and they actually become less agressive . so it 's very interesting to see how politics play out in these male and female societies . now back to the ladies here . in a core family group you 'll have a mother , maybe even a grandmother , her daughters and all of their offspring , the male and female calves . and what 's very interesting here is that how character makes a difference . so each matriarch has a very different character . these two characters are kind of curious , they 're uncertain , whereas these other two characters are really agressive . `` we 're going to charge first , ask questions later . '' but then there are also matriarchs that say , `` forget it ! i 'm going to run first and then figure it out when we 're in the bush and it 's safe . '' but the wisest matriarch , the matriarchs that succeed best in all of the studies that have been done , is the one that assesses the danger and decides is this worth running away from or is this not a big deal at all . now being social is super important for elephants and of course right at the beginning , just like early childhood development , socialization is very important . bathing together , eating together , playing together , rough housing , this is all very important for social development . and who has n't tried to beat their sibling to the head of the line coming into the water hole ? and these relationships from the beginning is just like best friends forever for real . these females are going to live together for life . now if it 's a male , female they might know each other for life , but it 's really important to develop those bonds early on . those are the relationships that are going to save you later . i 'll show you a little schoolyard scenario here . where , i think if you just focus on what 's happening here you can see that we have the bully , he 's pulling on the trunk of this baby calf , and then we have the diplomat who 's reaching over and saying , `` no , do n't do that ! stop doing that ! '' and then , of course , we have the bystander . and how do you get these three different characters within the family ? it 's kind of fascinating to think that elephants really are just like us . and so i got curious about this and i thought , `` well , what if you measure the difference in character of a dominant female 's calf versus a lower-ranking female 's calf , and see what happens in their growing up . '' and so we started doing this . and you can see this little guy with his ears out , really charging at you . the difference between that character and the character who holds back , wants to touch mom , is n't so certain about what 's going on here . but the other one 's charging ahead all confident . well , we started measuring how far away a calf will stray from mom , how often do they touch others , how often do they initiate play , and then look at the dominance of the females , of their mothers . and what we found is that socializing with the dominant calves actually socialize more significantly more than the lower-ranking calves . and what it looks like is it 's not that the lower-ranking calves do n't want to play , they 're actually not allowed to interact with the higher-ranking calves . they get swatted away from the dominant females . and so this is kind of the downside of , okay we are very much like elephants , elephants are as much like us , but it 's kind of for better or for worse because i can also see this happening in humans and maybe we should take a lesson from that . one last thing that we found is that the males will be the risk-takers , they 're more independent and they 're more likely to spend more time away from mom . and that 's very true in human societies and with other social animals . so i hope i 've convinced you that we have very similar lives to elephants and that elephants have very individual , durable characters that we 've measured across years . the bully always tends to be the bully unless there 's some kind of social upset , and he decides he better be a softy or else he 's not going to gain favor at all . and then you have the gentle giants that are always going to be gentle . the young males really need mentoring from the elders , and those gentle giants are very good at doing that , soliciting them . leaving family is a really hard things for the males , but they survive and they figure out who to hang out with . so , just to end here , i just wanted to say that since they are so similar to us , and have these characters , i hope when you see them on tv or you go out and you 're lucky enough to see them in the wild , that maybe you 'll think of them as individual characters deserving of our attention , and also deserving of our protection . thank you .
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he gets too big , he gets a little fresh , the adult females had enough of him , but he also is independent , he wants to go out and play with the guys . so what happens then is that you have this all male society , very ritual male society . greg is our main dominant bull here , you can see him in the middle .
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why are rituals important in society ?
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we like to think of romantic feelings as spontaneous and indescribable things that come from the heart . but it 's actually your brain running a complex series of calculations within a matter of seconds that 's responsible for determining attraction . does n't sound quite as poetic , does it ? but just because the calculations are happening in your brain does n't mean those warm , fuzzy feelings are all in your head . in fact , all five of your senses play a role , each able to vote for , or veto , a budding attraction . the eyes are the first components in attraction . many visual beauty standards vary between cultures and eras , and signs of youth , fertility and good health , such as long lustrous hair , or smooth , scar-free skin , are almost always in demand because they 're associated with reproductive fitness . and when the eyes spot something they like , our instinct is to move closer so the other senses can investigate . the nose 's contribution to romance is more than noticing perfume or cologne . it 's able to pick up on natural chemical signals known as pheromones . these not only convey important physical or genetic information about their source but are able to activate a physiological or behavioral response in the recipient . in one study , a group of women at different points in their ovulation cycles wore the same t-shirts for three nights . after male volunteers were randomly assigned to smell either one of the worn shirts , or a new unworn one , saliva samples showed an increase in testosterone in those who had smelled a shirt worn by an ovulating woman . such a testosterone boost may give a man the nudge to pursue a woman he might not have otherwise noticed . a woman 's nose is particularly attuned to mhc molecules , which are used to fight disease . in this case , opposites attract . when a study asked women to smell t-shirts that had been worn by different men , they preferred the odors of those whose mhc molecules differed from theirs . this makes sense . genes that result in a greater variety of immunities may give offspring a major survival advantage . our ears also determine attraction . men prefer females with high-pitched , breathy voices , and wide formant spacing , correlated with smaller body size . while women prefer low-pitched voices with a narrow formant spacing that suggest a larger body size . and not surprisingly , touch turns out to be crucial for romance . in this experiment , not realizing the study had begun , participants were asked to briefly hold the coffee , either hot or iced . later , the participants read a story about a hypothetical person , and were asked to rate their personality . those who had held the hot cup of coffee perceived the person in the story as happier , more social , more generous and better-natured than those who had held the cup of iced coffee , who rated the person as cold , stoic , and unaffectionate . if a potential mate has managed to pass all these tests , there 's still one more : the infamous first kiss , a rich and complex exchange of tactile and chemical cues , such as the smell of one 's breath , and the taste of their mouth . this magical moment is so critical that a majority of men and women have reported losing their attraction to someone after a bad first kiss . once attraction is confirmed , your bloodstream is flooded with norepinephrine , activating your fight or flight system . your heart beats faster , your pupils dilate , and your body releases glucose for additional energy , not because you 're in danger but because your body is telling you that something important is happening . to help you focus , norepinephrine creates a sort of tunnel vision , blocking out surrounding distractions , possibly even warping your sense of time , and enhancing your memory . this might explain why people never forget their first kiss . the idea of so much of our attraction being influenced by chemicals and evolutionary biology may seem cold and scientific rather than romantic , but the next time you see someone you like , try to appreciate how your entire body is playing matchmaker to decide if that beautiful stranger is right for you .
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the eyes are the first components in attraction . many visual beauty standards vary between cultures and eras , and signs of youth , fertility and good health , such as long lustrous hair , or smooth , scar-free skin , are almost always in demand because they 're associated with reproductive fitness . and when the eyes spot something they like , our instinct is to move closer so the other senses can investigate .
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what do things like long lustrous hair and smooth scar free skin indicate and why would that be important ?
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translator : tom carter reviewer : bedirhan cinar ( circus music ) [ ted n ' ed 's carnival ] [ john lloyd 's inventory of the invisible ] [ adapted from a tedtalk given by john lloyd in 2009 ] june cohen : our next speaker has spent his whole career eliciting that sense of wonder . please welcome john lloyd . ( applause ) [ hall of mirrors ] the question is , `` what is invisible ? '' there 's more of it than you think , actually . everything , i would say -- everything that matters -- except every thing , and except matter . we can see matter but we ca n't see what 's the matter . we can see the stars and the planets but we ca n't see what holds them apart , or what draws them together . with matter as with people , we see only the skin of things , we ca n't see into the engine room , we ca n't see what makes people tick , at least not without difficulty , and the closer we look at anything , the more it disappears . in fact , if you look really closely at stuff , if you look at the basic substructure of matter , there is n't anything there . electrons disappear in a kind of fuzz , and there is only energy . one of the interesting things about invisibility is , the things that we can 's see , we also ca n't understand . gravity is one thing that we ca n't see , and which we do n't understand . it 's the least understood of all the four fundamental forces , and the weakest , and nobody really knows what it is or why it 's there . for what it 's worth , sir isaac newton , the greatest scientist who ever lived , he thought jesus came to earth specifically to operate the levers of gravity . that 's what he thought he was there for . so , bright guy , could be wrong on that one , i do n't know . ( laughter ) consciousness . i see all your faces ; i 've no idea what any of you are thinking . is n't that amazing ? is n't it incredible that we ca n't read each other 's minds , when we can touch each other , taste each other , perhaps , if we get close enough , but we ca n't read each other 's minds . i find that quite astonishing . in the sufi faith , this great middle eastern religion which some claim is the root of all religions , sufi masters are all telepaths , so they say , but their main exercise of telepathy is to send out powerful signals to the rest of us that it does n't exist . so that 's why we do n't think it exists ; the sufi masters working on us . in the question of consciousness and artificial intelligence , artificial intelligence has really , like the study of consciousness , gotten nowhere , we have no idea how consciousness works . not only have they not created artificial intelligence , they have n't yet created artificial stupidity . ( laughter ) the laws of physics : invisible , eternal , omnipresent , all powerful . remind you of anyone ? interesting . i 'm , as you can guess , not a materialist , i 'm an immaterialist . and i 've found a very useful new word -- ignostic . okay ? i 'm an ignostic . [ god ? ] i refuse to be drawn on the question on whether god exists until somebody properly defines the terms . another thing we ca n't see is the human genome . and this is increasingly peculiar , because about 20 years ago when they started delving into the genome , they thought it would probably contain around 100 thousand genes . every year since , it 's been revised downwards . we now think there are likely to be just over 20 thousand genes in the human genome . this is extraordinary , because rice -- get this -- rice is known to have 38 thousand genes . potatoes have 48 chromosomes , two more than people , and the same as a gorilla . ( laughter ) you ca n't see these things , but they are very strange . the stars by day , i always think that 's fascinating . the universe disappears . the more light there is , the less you can see . time . nobody can see time . i do n't know if you know this . there 's a big movement in modern physics to decide that time does n't really exist , because it 's too inconvenient for the figures . it 's much easier if it 's not really there . you ca n't see the future , obviously , and you ca n't see the past , except in your memory . one of the interesting things about the past is you particularly ca n't see -- my son asked me this the other day , `` dad , can you remember what i was like when i was two ? and i said , `` yes . '' he said , `` why ca n't i ? '' is n't that extraordinary ? you can not remember what happened to you earlier than the age of two or three . which is great news for psychoanalysts , because otherwise they 'd be out of a job . because that 's where all the stuff happens ( laughter ) that makes you who you are . another thing you ca n't see is the grid on which we hang . this is fascinating . you probably know , some of you , that cells are continually renewed . skin flakes off , hairs grow , nails , that kind of stuff -- but every cell in your body is replaced at some point . taste buds , every ten days or so . livers and internal organs take a bit longer . spine takes several years . but at the end of seven years , not one cell in your body remains from what was there seven years ago . the question is : who then are we ? what are we ? what is this thing that we hang on ? that is actually us ? atoms , ca n't see them . nobody ever will . they 're smaller than the wavelength of light . gas , ca n't see that . interesting , somebody mentioned 1600 recently . gas was invented in 1600 by a dutch chemist called van helmont . it 's said to be the most successful ever invention of a word by a known individual . quite good . he also invented a word called `` blas , '' meaning astral radiation . did n't catch on , unfortunately . ( laughter ) but well done , him . light -- you ca n't see light . when it 's dark , in a vacuum , if a person shines a beam of light straight across your eyes , you wo n't see it . slightly technical , some physicists will disagree with this . but it 's odd that you ca n't see the beam of light , you can only see what it hits . electricity , ca n't see that . do n't let anyone tell you they understand electricity , they do n't . nobody knows what it is . ( laughter ) you probably think the electrons in an electric wire move instantaneously down a wire , do n't you , at the speed of light , when you turn the light on , they do n't . electrons bumble down the wire , about the speed of spreading honey , they say . galaxies -- hundred billion of them , estimated in the universe . hundred billion . how many can we see ? five . five , out of a hundred billion galaxies , with the naked eye . and one of them is quite difficult to see , unless you 've got very good eyesight . radio waves . there 's another thing . heinrich hertz , when he discovered radio waves , in 1887 , he called them radio waves because they radiated . somebody said to him , `` what 's the point of these , heinrich ? what 's the point of these radio waves that you 've found ? '' and he said , `` well , i 've no idea , but i guess somebody will find a use for them someday . the biggest thing that 's invisible to us is what we do n't know . it is incredible how little we know . thomas edison once said , `` we do n't know one percent of one millionth about anything . '' and i 've come to the conclusion -- because you ask this other question : `` what 's another thing we ca n't see ? '' the point , most of us . what 's the point ? the point -- what i 've got it down to is there are only two questions really worth asking . `` why are we here ? `` , and `` what should we do about it while we are ? '' to help you , i 've got two things to leave you with , from two great philosophers , perhaps two of the greatest philosopher thinkers of the 20th century . one a mathematician and engineer , and the other a poet . the first is ludwig wittgenstein , who said , `` i do n't know why we are here , but i am pretty sure it 's not in order to enjoy ourselves . '' ( laughter ) he was a cheerful bastard , was n't he ? ( laughter ) and secondly , and lastly , w.h . auden , one of my favorite poets , who said , `` we are here on earth to help others . what the others are here for , i 've no idea . '' ( laughter ) ( applause ) ( circus music ) [ get your souvenir photo here ! ] [ continue your journey into the unknown ! ] ( circus music )
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it is incredible how little we know . thomas edison once said , `` we do n't know one percent of one millionth about anything . '' and i 've come to the conclusion -- because you ask this other question : `` what 's another thing we ca n't see ? ''
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which is one of the four fundamental forces ?
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translator : andrea mcdonough reviewer : bedirhan cinar the brain is the center of all of our thoughts , dreams , emotions , and memories . it 's what makes us who we are . but , there is still a lot that we do n't know about the brain . scientists have worked for years on trying to understand the human brain using techniques like eeg and fmri , where we scan the brain from the outside . but what if we could look inside the brains of humans and watch them as they work ? well , now we can by looking at the brains of people who are already going through surgery for clinical reasons , like curing epilepsy . epilepsy is a disease in which a faulty part of the brain starts working spontaneously for no apparent reason . it 's like an earthquake but inside your head . there 's no way to know in advance when a seizure will occur , so the patients are always at risk of unexpectedly losing control . there are drugs that treat epilepsy , but these do n't always work . some patients who do n't respond well to the drugs can undergo a different treatment where the faulty part in their brain , the part that starts the seizures , is surgically removed . the challenge is knowing which part to take out . how do you figure out which bit of the brain is faulty ? in order to find the exact location of the seizure onset , doctors embed electrodes directly into the patient 's brain around the suspected seizure center . the patient then stays in the hospital for a few days , waiting to have a seizure with the electrodes constantly recording the activity inside his or her brain . yes , now we want the patient to have a seizure so doctors can use the embedded electrodes to measure it and learn exactly where its origin was . after doctors are sure where the seizures come from in the brain , they can take the electrodes out . now they know what part of the brain they can remove in order to cure the patient . these brain electrodes can tell us more than just where the seizures happen . based on where the doctors place the electrodes in the brain , we can ask questions about what the brain does . sometimes we find one cell that starts bursting in activity every time the patient sees a particular picture , for example , a picture of marilyn monroe . see , every time the patient sees marilyn monroe , some specific cells fire in the brain . you can now know when the patient is thinking of marilyn monroe just by listening to these cells fire . when we find one or a few of these cells with each patient , we can then do all kinds of fancy things . for example , we can connect the recording electrode to a cursor on a screen and have the patient move the cursor left or right just by thinking of things . this can help people who lost the ability to move their hands , like people with spinal cord injuries or wounded soldiers , by having them control a prosthetic arm directly with their brain . our brain is a brilliant device which can make predictions about the future . for example , we can all know which word will appear at the end of this ... sentence . the brain can solve complicated problems , imagine the entire universe , and grasp concepts such as infinity or unicorns . the brain produces complex emotions like love or jealousy , it 's what makes us creative and curious , and it can even contemplate about itself . and the brain is the organ we use to study the brain . i think that the brain is the most beautiful organ in our body , but then i ask myself , `` which organ is making me think that ? ''
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well , now we can by looking at the brains of people who are already going through surgery for clinical reasons , like curing epilepsy . epilepsy is a disease in which a faulty part of the brain starts working spontaneously for no apparent reason . it 's like an earthquake but inside your head .
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what is it called when a faulty part of the brain starts working spontaneously for no apparent reason ?
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hendrix , cobain and page . they can all shred , but how exactly do the iconic contraptions in their hands produce notes , rhythm , melody and music . when you pluck a guitar string , you create a vibration called a standing wave . some points on the string , called nodes , do n't move at all , while other points , anti-nodes , oscillate back and forth . the vibration translates through the neck and bridge to the guitar 's body , where the thin and flexible wood vibrates , jostling the surrounding air molecules together and apart . these sequential compressions create sound waves , and the ones inside the guitar mostly escape through the hole . they eventually propagate to your ear , which translates them into electrical impulses that your brain interprets as sound . the pitch of that sound depends on the frequency of the compressions . a quickly vibrating string will cause a lot of compressions close together , making a high-pitched sound , and a slow vibration produces a low-pitched sound . four things affect the frequency of a vibrating string : the length , the tension , the density and the thickness . typical guitar strings are all the same length , and have similar tension , but vary in thickness and density . thicker strings vibrate more slowly , producing lower notes . each time you pluck a string , you actually create several standing waves . there 's the first fundamental wave , which determines the pitch of the note , but there are also waves called overtones , whose frequencies are multiples of the first one . all these standing waves combine to form a complex wave with a rich sound . changing the way you pluck the string affects which overtones you get . if you pluck it near the middle , you get mainly the fundamental and the odd multiple overtones , which have anti-nodes in the middle of the string . if you pluck it near the bridge , you get mainly even multiple overtones and a twangier sound . the familiar western scale is based on the overtone series of a vibrating string . when we hear one note played with another that has exactly twice its frequency , its first overtone , they sound so harmonious that we assign them the same letter , and define the difference between them as an octave . the rest of the scale is squeezed into that octave divided into twelve half steps whose frequency is each 2^ ( 1/12 ) higher than the one before . that factor determines the fret spacing . each fret divides the string 's remaining length by 2^ ( 1/12 ) , making the frequencies increase by half steps . fretless instruments , like violins , make it easier to produce the infinite frequencies between each note , but add to the challenge of playing intune . the number of strings and their tuning are custom tailored to the chords we like to play and the physiology of our hands . guitar shapes and materials can also vary , and both change the nature and sound of the vibrations . playing two or more strings at the same time allows you to create new wave patterns like chords and other sound effects . for example , when you play two notes whose frequencies are close together , they add together to create a sound wave whose amplitude rises and falls , producing a throbbing effect , which guitarists call the beats . and electric guitars give you even more to play with . the vibrations still start in the strings , but then they 're translated into electrical signals by pickups and transmitted to speakers that create the sound waves . between the pickups and speakers , it 's possible to process the wave in various ways , to create effects like distortion , overdrive , wah-wah , delay and flanger . and lest you think that the physics of music is only useful for entertainment , consider this . some physicists think that everything in the universe is created by the harmonic series of very tiny , very tense strings . so might our entire reality be the extended solo of some cosmic jimi hendrix ? clearly , there 's a lot more to strings than meets the ear .
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each fret divides the string 's remaining length by 2^ ( 1/12 ) , making the frequencies increase by half steps . fretless instruments , like violins , make it easier to produce the infinite frequencies between each note , but add to the challenge of playing intune . the number of strings and their tuning are custom tailored to the chords we like to play and the physiology of our hands .
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does the sound of an engine or a breaking glass have a particular note or can only tuned musical instruments produce particular notes ?
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you are the cargo director on the maiden voyage of the s.s . buoyant , and you 've agreed to transport several tanks containing the last specimens of a critically endangered fish species to their new aquarium . unfortunately , as you 're passing through shark-infested waters , the boat is battered by a fierce storm , throwing your precious cargo overboard . and to make matters worse , no one seems certain just how many fish tanks are missing . fortunately , you have a rescue sub at your disposal , but only enough fuel for one trip to the ocean floor . you need to know where the tanks are so you can gather them all in one quick pass . not a single fish can be lost . you decide to scan the three sectors of the ocean floor where the cargo could have landed . thermal imaging shows 50 organisms in the area , and you quickly realize that that number includes both your fish and some ravenous sharks . you flip on the sonar to get a better look . the image for sector alpha shows four tanks and two sharks , the image for sector beta shows two tanks and four sharks , and the image for sector gamma is blank . your sonar has malfunctioned , and you 're going to have to go with the info you have . you check the shipping notes , but all you learn is that each tank had the same number of fish inside . the cargo hold had space for anywhere from 1 to 13 total tanks . and finally , the old captain tells you that this area has the odd property that no two sectors can have the same number of sharks , but every sector will have at least one , and no more than seven . there 's no time to waste . the tanks wo n't withstand the pressure much longer . as you descend in the sub , you review everything you know . how many fish tanks do you need to find in sector gamma ? hurry , the fate of an entire species depends on you . pause here if you want to figure it out for yourself . answer in : 3 answer in : 2 answer in : 1 at first , it seems like there are just too many missing pieces of information . after all , you do n't know how many fish or how many tanks there are , let alone how many fish are in each one . but then you remember the best way to compare multiple pieces of partial information - a table . since we know there are thirteen tanks at most , and we already see six tanks in sectors alpha and beta , we know the total number of tanks must be between 6 and 13 . we also know that each sector has a different amount of sharks with no more than seven in each one . since there are two in sector alpha and four in sector beta , sector gamma can have 1 , 3 , 5 , 6 , or 7 sharks . what about the number of endangered fish ? out of the 50 total organisms in all three sectors , we know at least seven are sharks , leaving a maximum of 43 fish inside all the tanks . and the more sharks we find in sector 3 , the fewer fish there are to save . now , remember that the fish are equally distributed across all the tanks . why is that important ? because it means that one of the possible values for the total amount of fish must be divisible by one of the possible values for the total amount of tanks . and looking at the table , we can see that the only combination that works is 39 fish divided between 13 tanks with three fish in each . with sharks swarming around , you quickly pilot the sub through the first two sectors before retrieving the remaining seven tanks in sector gamma . you 've saved the species and taken an impromptu dive . all in all , not a bad day , unless you happen to be a hungry shark .
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since there are two in sector alpha and four in sector beta , sector gamma can have 1 , 3 , 5 , 6 , or 7 sharks . what about the number of endangered fish ? out of the 50 total organisms in all three sectors , we know at least seven are sharks , leaving a maximum of 43 fish inside all the tanks .
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would it be possible to solve this riddle if there were two sectors with an unknown number of fish , but a known number of sharks ? why or why not ?
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they call me the tornado chaser . when the wind is up and conditions are right , i get in my car and follow violent storms . `` crazy , '' you say ? perhaps , but really i chase these sky beasts to learn about them . i want to share with you what i know . tornadoes are rapidly rotating columns of air that form inside storms that connect with the ground via a funnel of cloud . when that happens , they tear across the earth , posing a huge threat to life and property . because of this , there 's a great deal of research into these phenomena , but the truth is , there 's still a lot we do n't know about how tornadoes form . the conditions that may give rise to one tornado wo n't necessarily cause another . but we have learned a lot since people first started recording tornadoes , like how to recognize the signs when one is brewing in the sky . are you coming along for the ride ? tornadoes begin with a thunderstorm but not just any thunderstorm . these are especially powerful , towering thunderstorms called supercells . reaching up to over 50,000 feet , they bring high force winds , giant hailstones , sometimes flooding and great flashes of lightning , too . these are the kinds of storms that breed tornadoes , but only if there are also very specific conditions in place , clues that we can measure and look out for when we 're trying to forecast a storm . rising air is the first ingredient needed for a tornado to develop . any storm is formed when condensation occurs , the byproducts of the clouds . condensation releases heat , and heat becomes the energy that drives huge upward drafts of air . the more condensation and the bigger the storm clouds grow , the more powerful those updrafts become . in supercells , this rising airmass is particularly strong . as the air climbs , it can change direction and start to move more quickly . finally , at the storm 's base , if there is a lot of moisture , a huge cloud base develops , giving the tornado something to feed off later , if it gets that far . when all these things are in place , a vortex can develop enclosed by the storm , and forming a wide , tall tube of spinning air that then gets pulled upwards . we call this a mesocyclone . outside , cool , dry , sinking air starts to wrap around the back of this mesocyclone , forming what 's known as a rear flank downdraft . this unusual scenario creates a stark temperature difference between the air inside the mesocyclone , and the air outside , building up a level of instability that allows a tornado to thrive . then , the mesocyclone 's lower part becomes tighter , increasing the speed of the wind . if , and that 's a big if , this funnel of air moves down into that large , moist cloud base at the bottom of the parent storm , it sucks it in and turns it into a rotating wall of cloud , forming a link between the storm that created it and the earth . the second that tube of spinning cloud touches the ground , it becomes a tornado . most are small and short-lived , producing winds of 65-110 miles per hour , but others can last for over an hour , producing 200 mile per hour winds . they are beautiful but terrifying , especially if you or your town is in its path . in that case , no one , not even tornado chasers like me , enjoy watching thing unfold . just like everything , however , tornadoes do come to an end . when the temperature difference disappears and conditions grow more stable , or the moisture in the air dries up , the once fierce parent storm loses momentum and draws its tornado back inside . even so , meteorologists and storm chasers like me will remain on the lookout , watching , always watching to see if the storm releases its long rope again .
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in that case , no one , not even tornado chasers like me , enjoy watching thing unfold . just like everything , however , tornadoes do come to an end . when the temperature difference disappears and conditions grow more stable , or the moisture in the air dries up , the once fierce parent storm loses momentum and draws its tornado back inside .
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tornadoes will stop when :
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as an experiment , we gave recordings of the same walt whitman poem to 3 different animators . each interpreted the text with no knowledge of what the others were creating here 's the result . `` a noiseless patient spider '' by walt whitman interpretation # 1 by jeremiah dickey , medium : paint on glass `` a noiseless patient spider , i mark 'd where on a little promontory it stood isolated , mark 'd how to explore the vacant vast surrounding , it launch 'd forth filament , filament , filament , out of itself , ever unreeling them , ever tirelessly speeding them . and you o my soul where you stand , surrounded , detached , in measureless oceans of space , ceaselessly musing , venturing , throwing , seeking the spheres to connect them , till the bridge you will need be form 'd , till the ductile anchor hold , till the gossamer thread you fling catch somewhere , o my soul . '' interpretation # 2 by biljana labovic , medium : video `` a noiseless patient spider , i mark ’ d where on a little promontory it stood isolated , mark ’ d how to explore the vacant vast surrounding , it launch ’ d forth filament , filament , filament , out of itself , ever unreeling them , ever tirelessly speeding them . and you o my soul where you stand , surrounded , detached , in measureless oceans of space , ceaselessly musing , venturing , throwing , seeking the spheres to connect them , till the bridge you will need be form ’ d , till the ductile anchor hold , till the gossamer thread you fling catch somewhere , o my soul . '' interpretation # 3 by lisa labracio , medium : scratchboard `` a noiseless patient spider , i mark ’ d where on a little promontory it stood isolated , mark ’ d how to explore the vacant vast surrounding , it launch ’ d forth filament , filament , filament , out of itself , ever unreeling them , ever tirelessly speeding them . and you o my soul where you stand , surrounded , detached , in measureless oceans of space , ceaselessly musing , venturing , throwing , seeking the spheres to connect them , till the bridge you will need be form ’ d , till the ductile anchor hold , till the gossamer thread you fling catch somewhere , o my soul . ''
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as an experiment , we gave recordings of the same walt whitman poem to 3 different animators . each interpreted the text with no knowledge of what the others were creating here 's the result .
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whitman uses alliteration ( the occurrence of the same letter or sound at the beginning of closely connected or adjacent words ) in this poem . read the poem and list the phrases that contain alliteration below . why would a writer use alliteration ?
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global oneness project a game for life i do n't know how i can really put this , but my football is really something that is very powerful in my life , that gives me the drive to be who i am now , and have the goals i have now . i think if it was n't for football… i ca n't really imagine myself without football . certain things , certain principles in my life are based on my football . i do n't know if you understand what i mean . [ ♪ native music ♪ ] [ children playing ] [ ♪ native music ♪ ] this is my place . its a very small place . its just a four room house . this is where we sit as a family , watch tv , eat supper , and chat . just family chats . i 'll show you the kitchen where we cook our dinner . this is my kitchen . its not a very big place but it is where i live . this is my bedroom ; i share it with my aunt , but unfortunately now she is asleep because she was working night shift . this is my bed . i sleep here with my kitten . oh yes , this is my kitten . it is my friend . i sleep with her almost every night . this is my aunt . she stays here . she is selling veggies and fruit and her business is definitely going very well . in one week you find that you come and buy something and then its not there , its finished . so she 's got a business that is doing well . this road that we are walking on , this is where i started playing soccer when i got to port elizabeth . we put small stones , there would be goals on each side of the road , then we 'd be playing with the guys . that was before there was grass here . there was no grass here , so we would play from that wall to this side of the road . i grew up playing here and when i see this road or when i walk here i always remember where i started playing soccer . [ ♪ native music ♪ ] most of the time i was with my other two cousin-brothers , and they would spend most of their time playing soccer and that 's how i got on to the field and played as well . [ ♪ native music ♪ ] when i was growing up i was very , very poor . when i was still in primary school , i would wash with cold water . my school shoes , the sole was broken , so when it was raining , my socks would be so wet . and in terms of food , there was absolutely nothing to eat . [ ♪ native music ♪ ] for me to be able to eat at school i would have to wait until we are writing a test . then each pupil would put on 10 cents or 20 cents . then the whole amount would go to the person who was the highest on a test , and that is how i would manage to eat , because , if we were writing a test and put on some money , it was definitely my money because i was a very good student . [ ♪ native music ♪ ] i know their are many people out there who are going through what i went through . i know they wo n't deal with it the way i dealt with it , because i was taking everyday as it was coming . [ ♪ native music ♪ ] i never thought of going out and being a prostitute or something , and i know other people who are going through that thing . always , not always , but sometimes opt for that if they are girls , and if they are boys , they go to armed robbery , bad things like that . so the main reason i always tell the story is just to let them know that poverty can not conquer you for the rest of your life . you can conquer poverty as well . [ ♪ native music ♪ ] [ dog barking ] [ ♪ native music ♪ ] there is a way that you can go . there is a solution to poverty . they always do things that are unethical because they say they are going through poverty . [ ♪ native music ♪ ] i 've never done anything to anyone when i was very poor , but here i am today . i 'm not as poor as i was before and for me , now , i do n't feel like i 'm poor , even though i do n't have everything i want . i do n't have a big house , i do n't have a car , but i still feel that i am rich because i am rich inside . [ speaking in native language ] [ laughter ] this is a very good friend of mine . i grew up playing with him on the street . he was never a very good player , but a very good goal keeper . [ laughter ] come try it : [ gaming device sounds ] [ winning tune ] [ quarters hitting the metal return ] i 've won . it 's my lucky day . there you go , that 's all the money . [ ♪ native hip-hop music ♪ ] soccer helped me to stay away from the option of being a prostitute . i have always had love for my football and discipline . if you are going to be doing all the wrong things to try and get something to eat , or money , then those things wo n't be in-line with your football . if you look at soccer , the things you do that are in line with football , they are also in line with your own life . [ ♪ native hip-hop music ♪ ] people love soccer , and the young kids out there , they are interested in soccer . if you talk about soccer , they all know what you 're talking about , because everyone knows about soccer . so its easy to reach out to the people with soccer . [ ♪ native hip-hop music ♪ ] grassroots soccer we have the kids who know how to prevent themselves from getting hiv and also to teach them life skills . [ ♪ native hip-hop music ♪ ] the older guys have gone through things in their lives , but would like to teach the kids so that they could not go through those things . the way we would do is with interactive games . so we do n't really say , `` yeah , we 're going to talk about hiv now . '' some people might just lose interest in it , but simply because its interactive , we do the actual activities where they just learn from them . and its not as if we are telling them what to do , like to abstain . [ ♪ native hip-hop music ♪ ] so why was it not easy to find the ball ? because you could n't see the ball . so remember when we play that game , what did you say ? teacher > yes my girl , say it . student > someone who has the ball is going to be hiv positive . so what does that tell you about hiv ? you ca n't see someone who has hiv . [ clapping ] since we work with kids we use the power of soccer , and we use soccer balls because kids love to play . if you just make them play , especially with our street leagues , the way we do the teaching for hiv and aids gives them time to play soccer . [ ♪ native hip-hop music ♪ ] those are tools for them to be better people , to stay away from things that could destroy their lives . [ ♪ native hip-hop music ♪ ] after we 've done the program , we also assess the change in their attitudes . [ ♪ native hip-hop music ♪ ] [ clapping ] if there 's a big difference where their attitudes were before they went through the program , i would be very happy about that . [ ♪ native music ♪ ] when you 've got something in your heart and you also want someone else to have that same feeling , i do n't know how to say it ... but it 's always important to just share things with other people . it 's just important . if you know you can do something to help the next person , just do it with all your heart . and not expect to get a reward . it really makes more sense to be able to have others help because , really , we can not live in isolation . honestly , we could be a unity here , but what about the others that are not a unity ? we are going to say , yes we are a unity , that is fine for us . they are not a unity , that 's their own problem . it should n't be like that . [ ♪ native music ♪ ] if people could unite . i 'm telling you , i do n't see anything stopping the world from being a better place . i do n't see anything stopping it . [ ♪ native music ♪ ] it does n't take much for soccer to get people together . if there 's a soccer match somewhere , as long as they know that match is somewhere , they will definitely go . it 's really easy for it to unite people . [ ♪ native music ♪ ] for me its really about passion because i love soccer . i love soccer . it just really ... even if i can be stressed out about something , at my training session or at my game , i forget about it . i do n't know what to say about soccer , but that 's the thing about it . i just do n't know what it is . [ ♪ native music ♪ ] nolusindiso `` titie '' plaatjie is 22 years old and lives in port elizabeth south africa . she studied human movement science at nelson mandela metropolitan university and dreams of becoming an engineer . titie is a well-known soccer star , and in 2001 , she was named captain of the provincial team . she has been playing soccer since the age of five . currently working for grassroots soccer as the port elizabeth project coordinator , titie is a key facilitator in raising hiv ? aids awareness among youth and people of her community . she believes that this is a fight for the world . www.globalonenessproject.org
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if you just make them play , especially with our street leagues , the way we do the teaching for hiv and aids gives them time to play soccer . [ ♪ native hip-hop music ♪ ] those are tools for them to be better people , to stay away from things that could destroy their lives . [ ♪ native hip-hop music ♪ ] after we 've done the program , we also assess the change in their attitudes .
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titie knows that soccer can help kids stay away from “ things that could destroy their lives. ” how can soccer keep the kids in her neighborhood away from trouble , including theft and prostitution ?
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without water , a human can only survive for about 100 hours . but there 's a creature so resilient that it can go without it for decades . this one millimeter animal can survive both the hottest and coldest environments on earth , and can even withstand high levels of radiation . this is the tardigrade , and it 's one of the toughest creatures on earth , even if it does look more like a chubby , eight-legged gummy bear . most organisms need water to survive . water allows metabolism to occur , which is the process that drives all the biochemical reactions that take place in cells . but creatures like the tardigrade , also known as the water bear , get around this restriction with a process called anhydrobiosis , from the greek meaning life without water . and however extraordinary , tardigrades are n't alone . bacteria , single-celled organisms called archaea , plants , and even other animals can all survive drying up . for many tardigrades , this requires that they go through something called a tun state . they curl up into a ball , pulling their head and eight legs inside their body and wait until water returns . it 's thought that as water becomes scarce and tardigrades enter their tun state , they start synthesize special molecules , which fill the tardigrade 's cells to replace lost water by forming a matrix . components of the cells that are sensitive to dryness , like dna , proteins , and membranes , get trapped in this matrix . it 's thought that this keeps these molecules locked in position to stop them from unfolding , breaking apart , or fusing together . once the organism is rehydrated , the matrix dissolves , leaving behind undamaged , functional cells . beyond dryness , tardigrades can also tolerate other extreme stresses : being frozen , heated up past the boiling point of water , high levels of radiation , and even the vacuum of outer space . this has led to some erroneous speculation that tardigrades are extraterrestrial beings . while that 's fun to think about , scientific evidence places their origin firmly on earth where they 've evolved over time . in fact , this earthly evolution has given rise to over 1100 known species of tardigrades and there are probably many others yet to be discovered . and because tardigrades are so hardy , they exist just about everywhere . they live on every continent , including antarctica . and they 're in diverse biomes including deserts , ice sheets , the sea , fresh water , rainforests , and the highest mountain peaks . but you can find tardigrades in the most ordinary places , too , like moss or lichen found in yards , parks , and forests . all you need to find them is a little patience and a microscope . scientists are now to trying to find out whether tardigrades use the tun state , their anti-drying technique , to survive other stresses . if we can understand how they , and other creatures , stabilize their sensitive biological molecules , perhaps we could apply this knowledge to help us stabilize vaccines , or to develop stress-tolerant crops that can cope with earth 's changing climate . and by studying how tardigrades survive prolonged exposure to the vacuum of outer space , scientists can generate clues about the environmental limits of life and how to safeguard astronauts . in the process , tardigrades could even help us answer a critical question : could life survive on planets much less hospitable than our own ?
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if we can understand how they , and other creatures , stabilize their sensitive biological molecules , perhaps we could apply this knowledge to help us stabilize vaccines , or to develop stress-tolerant crops that can cope with earth 's changing climate . and by studying how tardigrades survive prolonged exposure to the vacuum of outer space , scientists can generate clues about the environmental limits of life and how to safeguard astronauts . in the process , tardigrades could even help us answer a critical question : could life survive on planets much less hospitable than our own ?
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what kind of real world applications do scientists hope to develop by studying tardigrades ?
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in the early 1960s , dick fosbury tried his hand at almost every sport , but never excelled at anything , until , at the age of 16 , he turned to the high jump . but when he could n't compete against the strong athletes at his college using the standard high jump techniques of the time , fosbury tried to jump a different way : backwards . instead of jumping with his face towards the bar , bringing each leg over in the traditional straddle method , he jumped with his back towards the bar . fosbury improved his record by over half a foot , and left his coaches amazed by this strange new style of high jumping . during the next few years , fosbury perfected his high jump style , won the u.s. national trials , and assured his place in the 1968 olympics in mexico . in the olympic games , fosbury amazed the world with his new technique , winning a gold metal with an olympic record leap of 2.24 meters . by the next olympic games , almost all of the competing of high jumpers had adopted what came to be known as the fosbury flop . what 's the secret behind the technique ? it lies in a physics concept called the center of mass . for every object , we can locate the average position of all of its mass by taking into account how the mass is spread around the object . for instance , the center of mass of a flat , rectangular object of uniform density will be in the intersection of both diagonals , in equal distance from each corner . we can find the center of mass for other objects by similar calculations , or by finding the object 's balancing point , which lies right underneath its center of mass . try balancing a broom by holding it and slowly bringing your hands together until they meet . this balancing point lies right underneath the broom 's center of mass . we humans also have a center of mass . when most people stand up , their center of mass is around the belly , but what happens to your center of mass when you lift your hands in the air ? your center of mass moves upwards . it moves all the time as you move through the day , based on how your body is positioned . it can even move outside of your body . when you bend forward , your center of mass is located below your bent belly in a place where there is no mass at all . weird to think about , but that 's the average position of all your mass . many objects ' center of mass are outside their bodies . think of doughnuts or boomerangs . now look at the fosbury flop , and follow the position of the center of mass of the jumper . the jumper runs very fast , so he can divert his horizontal velocity to vertical velocity , and jumps . wait for it ... there . look at the jumper 's center of mass as his body bends backward . it 's below the bar . that is the secret behind the jump . with the old , pre-fosbury techniques , the jumper had to apply enough force to lift his center of mass above the bar by a few inches in order to clear it . the fosbury flopper does n't have to do that . the genius of the fosbury flop is that the jumper can apply the same amount of force , but raise his body much higher than before . that means he can raise the bar so high that even when his center of mass ca n't go any higher , his arching body can . fosbury 's technique brought the high jump to new heights by splitting the jumper 's body away from his center of mass , giving it that much more room to clear higher and higher bars . so the fosbury flop may be sports history 's only great leap forward , that is also a great leap backward .
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when most people stand up , their center of mass is around the belly , but what happens to your center of mass when you lift your hands in the air ? your center of mass moves upwards . it moves all the time as you move through the day , based on how your body is positioned .
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complete the sentence : your center of mass _______ .
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why does salt dissolve in water but oil does n't ? well , in a word , chemistry , but that 's not very satisfying , is it ? well , the reason salt dissolves and oil does not comes down to the two big reasons why anything happens at all : energetics and entropy . energetics deals primarily with the attractive forces between things . when we look at oil or salt in water , we focus on the forces between particles on a very , very , very small scale , the molecular level . to give you a sense of this scale , in one glass of water , there are more molecules than known stars in the universe . now , all of these molecules are in constant motion , moving , vibrating , and rotating . what prevents almost all of those molecules from just flying out of the glass are the attractive interactions between molecules . the strength of the interactions between water , itself , and other substances is what we mean when we say energetics . you can think of the water molecules engaging in a constant dance , sort of like a square dance where they constantly and randomly exchange partners . put simply , the ability for substances to interact with water , balanced with how they disrupt how water interacts with itself , plays an important role in explaining why certain things mix well into water and others do n't . entropy basically describes the way things and energy can be arranged based on random motion . for example , think of the air in a room . imagine all the different possible arrangements in space for the trillions of particles that make up the air . some of those arrangments might have all the oxygen molecules over here and all the nitrogen molecules over there , separated . but far more of the possible arrangements have those molecules mixed up with one another . so , entropy favors mixing . energetics deals with attractive forces . and so , if attractive forces are present , the probability of some arrangements can be enhanced , the ones where things are attracted to each other . so , it is always the balance of these two things that determines what happens . on the molecular level , water is comprised of water molecules , made up of two hydrogen atoms and an oxygen atom . as liquid water , these molecules are engaged in a constant and random square dance that is called the hydrogen bonding network . entropy favors keeping the square dance going at all times . there are always more ways that all the water molecules can arrange in a square dance , as compared to if the water molecules did a line dance . so , the square dance constantly goes on . so , what happens when you put salt in the water ? well , on the molecular level , salt is actually made up of two different ions , chlorine and sodium , that are organized like a brick wall . they show up to the dance as a big group in formation and sit on the side at first , shy and a bit reluctant to break apart into individual ions to join the dance . but secretly , those shy dancers just want someone to ask them to join . so , when a water randomly bumps into one of them and pulls them into the dance away from their group , they go . and once they go into the dance , they do n't come back out . and in fact , the addition of the salt ions adds more possible dance positions in the square dance , so it is favored for them to stay dancing with water . now , let 's take oil . with oil , the molecules are sort of interested in dancing with water , so entropy favors them joining the dance . the problem is that oil molecules are wearing gigantic ballgowns , and they 're way bigger than water molecules . so , when an oil molecule gets pulled in , their size is really disruptive to the dance and the random exchange of partners that the waters engage in , a very important part of the dance . in addition , they are not great dancers . the water molecules try to engage the oil molecules in the dance , but they just keep bumping into their dresses and taking up all the room on the dance floor . there are way more ways the waters can dance when the oil gets off the floor , so the waters squeeze out the oil , pushing it back to the bench with the others . pretty soon , when a large number of oils have been squeezed over to the side , they band together to commiserate about how unfair the waters are being and stick together as a group . so , it is this combination of the interactions between molecules and the configurations available to them when they 're moving randomly that dictates whether they mix . in other words , water and oil do n't mix because they just do n't make great dance partners .
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on the molecular level , water is comprised of water molecules , made up of two hydrogen atoms and an oxygen atom . as liquid water , these molecules are engaged in a constant and random square dance that is called the hydrogen bonding network . entropy favors keeping the square dance going at all times .
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which statement best describes the “ hydrogen bonding network ” ?
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have you ever tried to picture an ideal world ? one without war , poverty , or crime ? if so , you 're not alone . plato imagined an enlightened republic ruled by philosopher kings , many religions promise bliss in the afterlife , and throughout history , various groups have tried to build paradise on earth . thomas more 's 1516 book `` utopia '' gave this concept a name , greek for `` no place . '' though the name suggested impossibility , modern scientific and political progress raised hopes of these dreams finally becoming reality . but time and time again , they instead turned into nightmares of war , famine , and oppression . and as artists began to question utopian thinking , the genre of dystopia , the not good place , was born . one of the earliest dystopian works is jonathan swift 's `` gulliver 's travels . '' throughout his journey , gulliver encounters fictional societies , some of which at first seem impressive , but turn out to be seriously flawed . on the flying island of laputa , scientists and social planners pursue extravagant and useless schemes while neglecting the practical needs of the people below . and the houyhnhnm who live in perfectly logical harmony have no tolerance for the imperfections of actual human beings . with his novel , swift established a blueprint for dystopia , imagining a world where certain trends in contemporary society are taken to extremes , exposing their underlying flaws . and the next few centuries would provide plenty of material . industrial technology that promised to free laborers imprisoned them in slums and factories , instead , while tycoons grew richer than kings . by the late 1800 's , many feared where such conditions might lead . h. g. wells 's `` the time machine '' imagined upper classes and workers evolving into separate species , while jack london 's `` the iron heel '' portrayed a tyrannical oligarchy ruling over impoverished masses . the new century brought more exciting and terrifying changes . medical advances made it possible to transcend biological limits while mass media allowed instant communication between leaders and the public . in aldous huxley 's `` brave new world '' , citizens are genetically engineered and conditioned to perform their social roles . while propaganda and drugs keep the society happy , it 's clear some crucial human element is lost . but the best known dystopias were not imaginary at all . as europe suffered unprecedented industrial warfare , new political movements took power . some promised to erase all social distinctions , while others sought to unite people around a mythical heritage . the results were real-world dystopias where life passed under the watchful eye of the state and death came with ruthless efficiency to any who did n't belong . many writers of the time did n't just observe these horrors , but lived through them . in his novel `` we '' , soviet writer yevgeny zamyatin described a future where free will and individuality were eliminated . banned in the u.s.s.r. , the book inspired authors like george orwell who fought on the front lines against both fascism and communism . while his novel `` animal farm '' directly mocked the soviet regime , the classic `` 1984 '' was a broader critique of totalitarianism , media , and language . and in the u.s.a. , sinclair lewis 's `` it ca n't happen here '' envisioned how easily democracy gave way to fascism . in the decades after world war ii , writers wondered what new technologies like atomic energy , artificial intelligence , and space travel meant for humanity 's future . contrasting with popular visions of shining progress , dystopian science fiction expanded to films , comics , and games . robots turned against their creators while tv screens broadcast deadly mass entertainment . workers toiled in space colonies above an earth of depleted resources and overpopulated , crime-plagued cities . yet politics was never far away . works like `` dr. strangelove '' and `` watchmen '' explored the real threat of nuclear war , while `` v for vendetta '' and `` the handmaid 's tale '' warned how easily our rights could disappear in a crisis . and today 's dystopian fiction continues to reflect modern anxieties about inequality , climate change , government power , and global epidemics . so why bother with all this pessimism ? because at their heart , dystopias are cautionary tales , not about some particular government or technology , but the very idea that humanity can be molded into an ideal shape . think back to the perfect world you imagined . did you also imagine what it would take to achieve ? how would you make people cooperate ? and how would you make sure it lasted ? now take another look . does that world still seem perfect ?
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but time and time again , they instead turned into nightmares of war , famine , and oppression . and as artists began to question utopian thinking , the genre of dystopia , the not good place , was born . one of the earliest dystopian works is jonathan swift 's `` gulliver 's travels . ''
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what does the word dystopia literally mean ?
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just a minute ago , this oil helped make a delicious meal possible . but now , it 's just some nasty goop . what should we do with it ? well , the easiest thing would be to pour it down the drain ; that makes it seem like it 's gone , but it 's not really gone . instead , it 's collecting bits of food and other random stuff , producing monstrous , greasy blockages that clog not only your own drain but entire sewage systems , causing flooding and pollution . many places have laws for proper disposal of grease , but we can go one step further . instead of just throwing it away safely , we can turn it into something useful . and if you 're wondering what anyone could possibly want with a bunch of digusting , used cooking oil , the answer is : biodiesel . you 've probably heard of diesel engines . they power farming and construction equipment , trucks , buses , ships , trains , backup generators , and even some cars . most of the fuel that feeds these engines is refined from petroleum , which comes from long-dead dinosaurs and other ancient fossils . but diesel fuel can also be derived from more recently-dead organisms , like plants and animals . and this type of fuel is what we call biodiesel . biodiesel is a biodegradable energy source , made from plant oils or animal fats , that can usually be burned in regular diesel engines . you guessed it , it 's the 'bio ' version of diesel . it 's cleaner than normal diesel , so there has been a push to generate it from crops like soybeans . now , growing plants for fuel , instead of food , comes with its own problems . but fortunately , we already have some oils and fats right here . preparing your used cooking grease for recycling is easy . first , let it cool down to room temperature . then , transfer it to a clean container . you can use any old bottles you have lying around , like milk jugs , as long as they 're completely empty , rinsed , and dried . use a funnel to avoid spills and a sieve to filter out any small food particles . you can even add bacon grease and other animal fats or the excess oil from canned food , like tuna or sardines , just make sure it 's really oil and not brine . so , what happens now that your oil is safely contained ? well , many cities have recycling services that will pick up large amounts of grease from restaurants and other establishments . but there are locations where individuals can drop off their containers , as well . all of this grease will end up at a processing plant , where it can be converted to useable biodiesel . how does this conversion work ? well , all these oils and fats you donated are made up of triglycerides , a glycerol molecule connected to three fatty acid chains . to convert fats to fuel , they react with an alcohol , usually methanol or ethanol , which produces long-chain esters and glycerol . to compare , here are some molecules of regular diesel fuel . now , here are the molecules we created by breaking apart the triglycerides . glycerol is the odd man out , so it 's removed at the end of the process . but look at these esters ! if you squint , their structures look pretty similar to those of the long-chain hydrocarbons in regular diesel . and diesel engines , with a few small modifications , can also be made to squint and burn these esters like regular diesel fuel . et voila ! biodiesel . now , you might be wondering whether all this hassle over recycling used cooking oil is even worth it . after all , how much energy can it possibly generate ? well , if all the grease that new yorkers throw away in one day were converted to jet fuel , it would be enough to power several hundred flights from new york to los angeles . and let 's not forget that using waste oil instead of burning more fossil fuels will limit our negative effects on the environment . recycling used cooking grease turns goop into good . by contributing a little bit , individuals and businesses can help create an alternative , stable source of diesel oil , while protecting the environment and keeping our cities cleaner . and that 's pretty slick .
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et voila ! biodiesel . now , you might be wondering whether all this hassle over recycling used cooking oil is even worth it .
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what is the reactor used to make biodiesel ?
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have you ever talked with a friend about a problem only to realize that he just does n't seem to grasp why the issue is so important to you ? have you ever presented an idea to a group and it 's met with utter confusion ? or maybe you 've been in an argument when the other person suddenly accuses you of not listening to what they 're saying at all ? what 's going on here ? the answer is miscommunication , and in some form or another , we 've all experienced it . it can lead to confusion , animosity , misunderstanding , or even crashing a multimillion dollar probe into the surface of mars . the fact is even when face-to-face with another person , in the very same room , and speaking the same language , human communication is incredibly complex . but the good news is that a basic understanding of what happens when we communicate can help us prevent miscommunication . for decades , researchers have asked , `` what happens when we communicate ? '' one interpretation , called the transmission model , views communication as a message that moves directly from one person to another , similar to someone tossing a ball and walking away . but in reality , this simplistic model does n't account for communication 's complexity . enter the transactional model , which acknowledges the many added challenges of communicating . with this model , it 's more accurate to think of communication between people as a game of catch . as we communicate our message , we receive feedback from the other party . through the transaction , we create meaning together . but from this exchange , further complications arise . it 's not like the star trek universe , where some characters can vulcan mind meld , fully sharing thoughts and feelings . as humans , we ca n't help but send and receive messages through our own subjective lenses . when communicating , one person expresses her interpretation of a message , and the person she 's communicating with hears his own interpretation of that message . our perceptual filters continually shift meanings and interpretations . remember that game of catch ? imagine it with a lump of clay . as each person touches it , they shape it to fit their own unique perceptions based on any number of variables , like knowledge or past experience , age , race , gender , ethnicity , religion , or family background . simultaneously , every person interprets the message they receive based on their relationship with the other person , and their unique understanding of the semantics and connotations of the exact words being used . they could also be distracted by other stimuli , such as traffic or a growling stomach . even emotion might cloud their understanding , and by adding more people into a conversation , each with their own subjectivities , the complexity of communication grows exponentially . so as the lump of clay goes back and forth from one person to another , reworked , reshaped , and always changing , it 's no wonder our messages sometimes turn into a mush of miscommunication . but , luckily , there are some simple practices that can help us all navigate our daily interactions for better communication . one : recognize that passive hearing and active listening are not the same . engage actively with the verbal and nonverbal feedback of others , and adjust your message to faciliate greater understanding . two : listen with your eyes and ears , as well as with your gut . remember that communication is more than just words . three : take time to understand as you try to be understood . in the rush to express ourselves , it 's easy to forget that communication is a two-way street . be open to what the other person might say . and finally , four : be aware of your personal perceptual filters . elements of your experience , including your culture , community , and family , influence how you see the world . say , `` this is how i see the problem , but how do you see it ? '' do n't assume that your perception is the objective truth . that 'll help you work toward sharing a dialogue with others to reach a common understanding together .
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two : listen with your eyes and ears , as well as with your gut . remember that communication is more than just words . three : take time to understand as you try to be understood .
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noise can be defined as any interference that disrupts and/or distorts communication . what are some examples of noise ? what sources of noise do you struggle with the most in your own communication ?
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the heisenberg uncertainty principle is one of a handful of ideas from quantum physics to expand into general pop culture . it says that you can never simultaneously know the exact position and the exact speed of an object and shows up as a metaphor in everything from literary criticism to sports commentary . uncertainty is often explained as a result of measurement , that the act of measuring an object 's position changes its speed , or vice versa . the real origin is much deeper and more amazing . the uncertainty principle exists because everything in the universe behaves like both a particle and a wave at the same time . in quantum mechanics , the exact position and exact speed of an object have no meaning . to understand this , we need to think about what it means to behave like a particle or a wave . particles , by definition , exist in a single place at any instant in time . we can represent this by a graph showing the probability of finding the object at a particular place , which looks like a spike , 100 % at one specific position , and zero everywhere else . waves , on the other hand , are disturbances spread out in space , like ripples covering the surface of a pond . we can clearly identify features of the wave pattern as a whole , most importantly , its wavelength , which is the distance between two neighboring peaks , or two neighboring valleys . but we ca n't assign it a single position . it has a good probability of being in lots of different places . wavelength is essential for quantum physics because an object 's wavelength is related to its momentum , mass times velocity . a fast-moving object has lots of momentum , which corresponds to a very short wavelength . a heavy object has lots of momentum even if it 's not moving very fast , which again means a very short wavelength . this is why we do n't notice the wave nature of everyday objects . if you toss a baseball up in the air , its wavelength is a billionth of a trillionth of a trillionth of a meter , far too tiny to ever detect . small things , like atoms or electrons though , can have wavelengths big enough to measure in physics experiments . so , if we have a pure wave , we can measure its wavelength , and thus its momentum , but it has no position . we can know a particles position very well , but it does n't have a wavelength , so we do n't know its momentum . to get a particle with both position and momentum , we need to mix the two pictures to make a graph that has waves , but only in a small area . how can we do this ? by combining waves with different wavelengths , which means giving our quantum object some possibility of having different momenta . when we add two waves , we find that there are places where the peaks line up , making a bigger wave , and other places where the peaks of one fill in the valleys of the other . the result has regions where we see waves separated by regions of nothing at all . if we add a third wave , the regions where the waves cancel out get bigger , a fourth and they get bigger still , with the wavier regions becoming narrower . if we keep adding waves , we can make a wave packet with a clear wavelength in one small region . that 's a quantum object with both wave and particle nature , but to accomplish this , we had to lose certainty about both position and momentum . the positions is n't restricted to a single point . there 's a good probability of finding it within some range of the center of the wave packet , and we made the wave packet by adding lots of waves , which means there 's some probability of finding it with the momentum corresponding to any one of those . both position and momentum are now uncertain , and the uncertainties are connected . if you want to reduce the position uncertainty by making a smaller wave packet , you need to add more waves , which means a bigger momentum uncertainty . if you want to know the momentum better , you need a bigger wave packet , which means a bigger position uncertainty . that 's the heisenberg uncertainty principle , first stated by german physicist werner heisenberg back in 1927 . this uncertainty is n't a matter of measuring well or badly , but an inevitable result of combining particle and wave nature . the uncertainty principle is n't just a practical limit on measurment . it 's a limit on what properties an object can have , built into the fundamental structure of the universe itself .
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both position and momentum are now uncertain , and the uncertainties are connected . if you want to reduce the position uncertainty by making a smaller wave packet , you need to add more waves , which means a bigger momentum uncertainty . if you want to know the momentum better , you need a bigger wave packet , which means a bigger position uncertainty .
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there is a relationship similar to the heisenberg uncertainty principle for position and momentum between the uncertainty in the energy of a particle and the uncertainty in the time at which that energy is measured—a smaller energy uncertainty means a bigger time uncertainty , and vice versa . in quantum physics , the energy of a particle is related to the frequency at which the wave associated with that particle oscillates ( that is , the number of times per second that the wave goes from peak to valley and back ) . given that , can you explain the origin of the energy-time uncertainty relationship ?
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what do an ancient greek philosopher and a 19th century quaker have in common with nobel prize-winning scientists ? although they are separated over 2,400 years of history , each of them contributed to answering the eternal question : what is stuff made of ? it was around 440 bce that democritus first proposed that everything in the world was made up of tiny particles surrounded by empty space . and he even speculated that they vary in size and shape depending on the substance they compose . he called these particles `` atomos , '' greek for indivisible . his ideas were opposed by the more popular philosophers of his day . aristotle , for instance , disagreed completely , stating instead that matter was made of four elements : earth , wind , water and fire , and most later scientists followed suit . atoms would remain all but forgotten until 1808 , when a quaker teacher named john dalton sought to challenge aristotelian theory . whereas democritus 's atomism had been purely theoretical , dalton showed that common substances always broke down into the same elements in the same proportions . he concluded that the various compounds were combinations of atoms of different elements , each of a particular size and mass that could neither be created nor destroyed . though he received many honors for his work , as a quaker , dalton lived modestly until the end of his days . atomic theory was now accepted by the scientific community , but the next major advancement would not come until nearly a century later with the physicist j.j. thompson 's 1897 discovery of the electron . in what we might call the chocolate chip cookie model of the atom , he showed atoms as uniformly packed spheres of positive matter filled with negatively charged electrons . thompson won a nobel prize in 1906 for his electron discovery , but his model of the atom did n't stick around long . this was because he happened to have some pretty smart students , including a certain ernest rutherford , who would become known as the father of the nuclear age . while studying the effects of x-rays on gases , rutherford decided to investigate atoms more closely by shooting small , positively charged alpha particles at a sheet of gold foil . under thompson 's model , the atom 's thinly dispersed positive charge would not be enough to deflect the particles in any one place . the effect would have been like a bunch of tennis balls punching through a thin paper screen . but while most of the particles did pass through , some bounced right back , suggesting that the foil was more like a thick net with a very large mesh . rutherford concluded that atoms consisted largely of empty space with just a few electrons , while most of the mass was concentrated in the center , which he termed the nucleus . the alpha particles passed through the gaps but bounced back from the dense , positively charged nucleus . but the atomic theory was n't complete just yet . in 1913 , another of thompson 's students by the name of niels bohr expanded on rutherford 's nuclear model . drawing on earlier work by max planck and albert einstein he stipulated that electrons orbit the nucleus at fixed energies and distances , able to jump from one level to another , but not to exist in the space between . bohr 's planetary model took center stage , but soon , it too encountered some complications . experiments had shown that rather than simply being discrete particles , electrons simultaneously behaved like waves , not being confined to a particular point in space . and in formulating his famous uncertainty principle , werner heisenberg showed it was impossible to determine both the exact position and speed of electrons as they moved around an atom . the idea that electrons can not be pinpointed but exist within a range of possible locations gave rise to the current quantum model of the atom , a fascinating theory with a whole new set of complexities whose implications have yet to be fully grasped . even though our understanding of atoms keeps changing , the basic fact of atoms remains , so let 's celebrate the triumph of atomic theory with some fireworks . as electrons circling an atom shift between energy levels , they absorb or release energy in the form of specific wavelengths of light , resulting in all the marvelous colors we see . and we can imagine democritus watching from somewhere , satisfied that over two millennia later , he turned out to have been right all along .
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drawing on earlier work by max planck and albert einstein he stipulated that electrons orbit the nucleus at fixed energies and distances , able to jump from one level to another , but not to exist in the space between . bohr 's planetary model took center stage , but soon , it too encountered some complications . experiments had shown that rather than simply being discrete particles , electrons simultaneously behaved like waves , not being confined to a particular point in space .
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compare and contrast dalton ’ s model , thomson ’ s model , rutherford ’ s model , and bohr ’ s model of the atom .
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for most of human history , medical workers sought to treat diseases or cure them . the rise of vaccination in the 19th century enhanced the potential to prevent people from contracting illnesses in the first place . but only in recent decades did it become possible to ensure that a particular disease never threatens humanity again . the story of smallpox , the first and , so far , the only disease to be permanently eradicated from the world , shows how disease eradication can happen and why it is so difficult to achieve . smallpox emerged in human populations thousands of years ago as a contagious virus that spread rapidly , primarily through close , face to face contact , causing fever , aches and rashes . it killed up to 30 % of its victims and often left survivors with life-long disfiguring scars . the devastating impact of smallpox was so great that several cultures had religious deities specifically dedicated to it . in the 20th century alone , it is estimated to have killed more than 300 million people worldwide . with the effective deployment of vaccination , the number of cases began to decrease . by seeking out infected individuals , isolating them , and vaccinating their contacts to prevent further transmission , scientists realized that the spread of the disease could be haulted . in fact , because smallpox could only survive in human hosts , vaccinating all of an infected persons ' potential contacts would stop the virus dead in its tracks and eliminate it from that region . once this strategy had succeeded in ridding most industrialized countries from disease , health officials realized that eradicating it worldwide was within reach . but this was not an easy process , proving especially difficult in places suffering from poor infrastructure or civil wars . the eradication effort took decades and involved millions of people working together , from world leaders and international organizations to rural doctors and community workers . in india , one of the last strongholds of the disease , health workers visited every one of the country 's 100 million households to search for cases . through this unprecedented worldwide effort , in which even rival superpowers cooperated , smallpox was finally declared eradicated in 1980 , saving approximately 40 million lives over the following two decades . there were several factors that made smallpox an ideal candidate for eradication . first , humans are essential to the smallpox lifecycle , so breaking the chain of human to human transmission causes the virus to die out . in contrast , many other pathogens , like ebola or the bubonic plague , can survive in animal carriers , while the bacteria that cause tetanus can even live in the soil . secondly , individuals infected with smallpox displayed a characteristic rash , making them easy to identify , even without a lab test . the lack of such practical diagnostic tools for diseases with non-specific symptoms , or that have long incubation periods , such as aids , makes their eradication more difficult . third , the availability of a smallpox vaccine that provided immunity for five to ten years in a single dose meant that there was an effective intervention to stop the virus from spreading . and finally , the initial success of several countries in eliminating the disease within their borders served as a proof of principle for its eradication worldwide . today , the same criteria are applied to determine whether other diseases can be similarly eliminated . and even though smallpox remains the only success story thus far , several other pathogens may be next in line . great progress has been made towards eradicating guinea worm disease simply by use of water filters . and vaccination for polio , which previously disabled hundreds of thousands of people each year is estimated to have prevented 13 million cases of paralysis , and 650,000 deaths since 1988 . with a 99 % drop in infections since the eradication effort began , one final push is all that is needed to ensure that polio will never paralyze another child . disease eradication is one public health effort that benefits all of humanity and challenges us to work together as a global community . beyond eliminating specific diseases , eradication programs benefit local populations by improving health infrastructure . for example , nigeria recently used facilities and personnel from their polio eradication program to effectively control an ebola outbreak . further more , globalization and international travel means that even a single infection anywhere in the world can potentially spread to other regions . by helping to protect others , we help to protect ourselves . disease eradication is the ultimate gift we can give to everyone alive today , as well as all future generations of humanity .
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the story of smallpox , the first and , so far , the only disease to be permanently eradicated from the world , shows how disease eradication can happen and why it is so difficult to achieve . smallpox emerged in human populations thousands of years ago as a contagious virus that spread rapidly , primarily through close , face to face contact , causing fever , aches and rashes . it killed up to 30 % of its victims and often left survivors with life-long disfiguring scars .
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how does smallpox spread ?
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translator : andrea mcdonough reviewer : bedirhan cinar you 've probably heard of pavlov 's dogs , the phrase that often summarizes dr. ivan pavlov 's early 20th century research , in which he demonstrated that we can alter what stimuli elicit a reflective response in canines . he showed this by sounding a bell just before he presented his group of dogs with meat powder . after many presentations of the bell , followed by tasty meat powder , the dogs eventually began to salivate at just the sound of the bell . they salivated even when there was no meat powder present . this phenomenon is n't limited to dogs . consider the placebo effect , in which a pill with no active substances brings about a response similar to a pill with a substance present . what changes here is our reaction to our ailment , such as perceiving less pain and not the ailment itself . or , consider the love humans have for a parent . some would argue that this love is instinctual , and they may be partially right . but , the argument fails to account for the equal amount of love that children adopted later in life hold for their adoptive parents . but the behaviorist argument can account for both accounts of love . a parent , biological or not , is constantly paired with things like food , smiles , toys , affection , games , protection , and entertainment . and a parent 's constant association with these wonderful or crucial aspects of a child 's life has a similar , albeit more complicated , effect that meat powder had on pavlov 's salivating dogs . in other words , if one 's parent is predictive of really good or really important things , then one 's parent becomes a really good and important thing , too . and there is also romantic advice to be gained from pavlov 's observations . we all need food to survive , right ? and someone who can provide such things in a delicious , saliva-producing manner stands to become our human equivalent of a ringing bell . in other words , if you can cook one or more scrumptious meals for a potential love interest , there 's a good chance that you 'll be viewed more favorably in the future , even if you did n't prepare the delicious food . and who would n't want the love of their life drooling over them ? but life is not just bell rings and salivation . there 's also a dark side to this type of learning , called `` taste aversion '' . taste aversion occurs when we ingest some food that eventually makes us sick , and , as a result , we avoid that food , sometimes for the rest of our lives . taste aversion is so powerful that the effect can be seen even if the illness is experienced hours later and even if the food itself did not actually make us sick . such is the case when we have the flu , and , by accident , we ingest some food moments prior to vomiting . in this case , we know that the food did not cause the vomiting , but our bodies do n't know that . and the next time we encounter that food , we are likely to refuse eating it . now , imagine the potential consequences of undercooking a meal on a first date . if the food makes your date sick , it is possible for them to associate that bad feeling with not just the food , but with < i > your < /i > food in particular . if the episode was traumatizing enough , or if it also happens on a subsequent date , they may come to relate you with the consequences , just like pavlov 's dogs related the bell with the meat powder . in other words , the sight of you showing up at the next dinner date might actually make your date nauseous ! as the old saying goes , the fastest way to someone 's heart is through their stomach , assuming you do n't make them sick in the process .
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but the behaviorist argument can account for both accounts of love . a parent , biological or not , is constantly paired with things like food , smiles , toys , affection , games , protection , and entertainment . and a parent 's constant association with these wonderful or crucial aspects of a child 's life has a similar , albeit more complicated , effect that meat powder had on pavlov 's salivating dogs .
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who is credited with identifying that neutral stimuli , like a bell , can produce reflexive responses when paired with stimuli that elicit those reflexes ?
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translator : jessica ruby reviewer : caroline cristal they 're long and slithery , and they 're not very colorful . but they do have a strange beauty of their own . their sinuous , nocturnal movements through the water are mesmerizing to watch . and though they may resemble underwater snakes , eels are , in fact , a very interesting type of fish . there are several things about eels that make them unique besides their elongated shape and limbless bodies . for one thing , eels have the ability to breathe through their skin . some can even leave the water and move over land for short periods . and , unlike most migratory fish , such as salmon , which spawn in fresh water but live their adult lives in salt water , eels of the genus anguilla migrate in the opposite direction , spawning and breeding in oceans and seas , while spending most of their intervening time in fresh water . if we were to take one such fresh water eel and follow its life story , it would be born in the middle of the north atlantic ocean , about a thousand miles east of bermuda . this area , called the sargasso sea , forms the western part of a subtropical gyre , a giant whirlpool in the middle of the ocean . our eel , let 's call it eli , would begin as one of ten to twenty million tiny eggs , carried by a female eel , hatching into a transparent leaf-shaped thing that looks nothing like an adult eel . eli starts to drift in ocean currents , predominantly the gulf stream towards either europe or north america , depending on its particular species . upon reaching the coast , eli is about two inches long , looking more eely but still transparent , known at this stage as a glass eel . but within a couple of days in fresh water , eli 's skin becomes pigmented a brownish-black , now looking more like that of an adult eel . you might notice that we have n't mentioned anything about eli 's gender yet . that 's because this is only determined once an eel enters fresh water , though nobody is sure exactly how that happens . most of the eels that stay in the estuaries and brackish water become males , while those that go upstream become females , growing up to two to three times bigger than their future mates . in this case , it turns out that eli was actually short for elaine . as a female eel , elaine will be quite solitary for most of her life in the stream , eating whatever falls in the water : grasshoppers , crickets , small fish , insect larvae , frogs , baby birds , almost anything she can get her mouth around . and she will grow quite big , up to four feet long and weighing as much as thirteen pounds . we do n't know exactly how fresh water eels know when it 's time to return to the ocean , but something calls to them . and their fall migration is one of the largest unseen migrations on the planet . as elaine leaves fresh water for the ocean , she undergoes a shocking metamorphosis . her eyes enlarge by about ten times , her skin gets thicker , and her fins get larger . these are most likely adaptations for their upcoming ocean travel , and elaine seamlessly makes the transition from fresh to salt water , which would be toxic for most other fish . once elaine leaves the mouth of the fresh water streams , she will disappear completely from human view . no one has witnessed , or been able to follow , an adult eel on their migration , nor do we know how deep they spawn . but it 's assumed that they can follow some signs that they can detect , such as a thermal barrier between ocean currents or a salinity front , in order to return to the same area of the ocean where they were born . because we do n't even know exactly what happens during an eel 's migration , we can only imagine what the actual breeding looks like . but the common hypothesis is that elaine and thousands , or hundreds of thousands , of other eels gather in large , intertwined masses and release their eggs and sperm in a giant orgy known as panmixia . a couple of days after the eggs are laid , they hatch , and the cycle begins again . and because we 've never seen the adult eels returning up the fresh water rivers , we must assume that , having completed their long and roundabout journey , these amazing and mysterious creatures finally die there , in the same place where they were born . goodbye , elaine ! it was a pleasure knowing you .
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for one thing , eels have the ability to breathe through their skin . some can even leave the water and move over land for short periods . and , unlike most migratory fish , such as salmon , which spawn in fresh water but live their adult lives in salt water , eels of the genus anguilla migrate in the opposite direction , spawning and breeding in oceans and seas , while spending most of their intervening time in fresh water . if we were to take one such fresh water eel and follow its life story , it would be born in the middle of the north atlantic ocean , about a thousand miles east of bermuda .
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some eels travel from fresh water to salt water to ________ .
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this may look like a neatly arranged stack of numbers , but it 's actually a mathematical treasure trove . indian mathematicians called it the staircase of mount meru . in iran , it 's the khayyam triangle . and in china , it 's yang hui 's triangle . to much of the western world , it 's known as pascal 's triangle after french mathematician blaise pascal , which seems a bit unfair since he was clearly late to the party , but he still had a lot to contribute . so what is it about this that has so intrigued mathematicians the world over ? in short , it 's full of patterns and secrets . first and foremost , there 's the pattern that generates it . start with one and imagine invisible zeros on either side of it . add them together in pairs , and you 'll generate the next row . now , do that again and again . keep going and you 'll wind up with something like this , though really pascal 's triangle goes on infinitely . now , each row corresponds to what 's called the coefficients of a binomial expansion of the form ( x+y ) ^n , where n is the number of the row , and we start counting from zero . so if you make n=2 and expand it , you get ( x^2 ) + 2xy + ( y^2 ) . the coefficients , or numbers in front of the variables , are the same as the numbers in that row of pascal 's triangle . you 'll see the same thing with n=3 , which expands to this . so the triangle is a quick and easy way to look up all of these coefficients . but there 's much more . for example , add up the numbers in each row , and you 'll get successive powers of two . or in a given row , treat each number as part of a decimal expansion . in other words , row two is ( 1x1 ) + ( 2x10 ) + ( 1x100 ) . you get 121 , which is 11^2 . and take a look at what happens when you do the same thing to row six . it adds up to 1,771,561 , which is 11^6 , and so on . there are also geometric applications . look at the diagonals . the first two are n't very interesting : all ones , and then the positive integers , also known as natural numbers . but the numbers in the next diagonal are called the triangular numbers because if you take that many dots , you can stack them into equilateral triangles . the next diagonal has the tetrahedral numbers because similarly , you can stack that many spheres into tetrahedra . or how about this : shade in all of the odd numbers . it does n't look like much when the triangle 's small , but if you add thousands of rows , you get a fractal known as sierpinski 's triangle . this triangle is n't just a mathematical work of art . it 's also quite useful , especially when it comes to probability and calculations in the domain of combinatorics . say you want to have five children , and would like to know the probability of having your dream family of three girls and two boys . in the binomial expansion , that corresponds to girl plus boy to the fifth power . so we look at the row five , where the first number corresponds to five girls , and the last corresponds to five boys . the third number is what we 're looking for . ten out of the sum of all the possibilities in the row . so 10/32 , or 31.25 % . or , if you 're randomly picking a five-player basketball team out of a group of twelve friends , how many possible groups of five are there ? in combinatoric terms , this problem would be phrased as twelve choose five , and could be calculated with this formula , or you could just look at the sixth element of row twelve on the triangle and get your answer . the patterns in pascal 's triangle are a testament to the elegantly interwoven fabric of mathematics . and it 's still revealing fresh secrets to this day . for example , mathematicians recently discovered a way to expand it to these kinds of polynomials . what might we find next ? well , that 's up to you .
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so 10/32 , or 31.25 % . or , if you 're randomly picking a five-player basketball team out of a group of twelve friends , how many possible groups of five are there ? in combinatoric terms , this problem would be phrased as twelve choose five , and could be calculated with this formula , or you could just look at the sixth element of row twelve on the triangle and get your answer .
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how many teams of two persons can you make from a group of five people ?
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let 's say you 're on a game show . you 've already earned $ 1000 in the first round when you land on the bonus space . now , you have a choice . you can either take a $ 500 bonus guaranteed or you can flip a coin . if it 's heads , you win $ 1000 bonus . if it 's tails , you get no bonus at all . in the second round , you 've earned $ 2000 when you land on the penalty space . now you have another choice . you can either take a $ 500 loss , or try your luck at the coin flip . if it 's heads , you lose nothing , but if it 's tails , you lose $ 1000 instead . if you 're like most people , you probably chose to take the guaranteed bonus in the first round and flip the coin in the second round . but if you think about it , this makes no sense . the odds and outcomes in both rounds are exactly the same . so why does the second round seem much scarier ? the answer lies in a phenomenon known as loss aversion . under rational economic theory , our decisions should follow a simple mathematical equation that weighs the level of risk against the amount at stake . but studies have found that for many people , the negative psychological impact we feel from losing something is about twice as strong as the positive impact of gaining the same thing . loss aversion is one cognitive bias that arises from heuristics , problem-solving approaches based on previous experience and intuition rather than careful analysis . and these mental shortcuts can lead to irrational decisions , not like falling in love or bungee jumping off a cliff , but logical fallacies that can easily be proven wrong . situations involving probability are notoriously bad for applying heuristics . for instance , say you were to roll a die with four green faces and two red faces twenty times . you can choose one of the following sequences of rolls , and if it shows up , you 'll win $ 25 . which would you pick ? in one study , 65 % of the participants who were all college students chose sequence b even though a is shorter and contained within b , in other words , more likely . this is what 's called a conjunction fallacy . here , we expect to see more green rolls , so our brains can trick us into picking the less likely option . heuristics are also terrible at dealing with numbers in general . in one example , students were split into two groups . the first group was asked whether mahatma gandhi died before or after age 9 , while the second was asked whether he died before or after age 140 . both numbers were obviously way off , but when the students were then asked to guess the actual age at which he died , the first group 's answers averaged to 50 while the second group 's averaged to 67 . even though the clearly wrong information in the initial questions should have been irrelevant , it still affected the students ' estimates . this is an example of the anchoring effect , and it 's often used in marketing and negotiations to raise the prices that people are willing to pay . so , if heuristics lead to all these wrong decisions , why do we even have them ? well , because they can be quite effective . for most of human history , survival depended on making quick decisions with limited information . when there 's no time to logically analyze all the possibilities , heuristics can sometimes save our lives . but today 's environment requires far more complex decision-making , and these decisions are more biased by unconscious factors than we think , affecting everything from health and education to finance and criminal justice . we ca n't just shut off our brain 's heuristics , but we can learn to be aware of them . when you come to a situation involving numbers , probability , or multiple details , pause for a second and consider that the intuitive answer might not be the right one after all .
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the answer lies in a phenomenon known as loss aversion . under rational economic theory , our decisions should follow a simple mathematical equation that weighs the level of risk against the amount at stake . but studies have found that for many people , the negative psychological impact we feel from losing something is about twice as strong as the positive impact of gaining the same thing .
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according to rational economic theory , people make decisions by :
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[ ♪sustained note♪ ] [ flag flapping in breeze ] [ path of freedom ] [ ♪ music ♪ ] [ prisoners chattering ] [ ♪ music ♪ ] - this is a tough guy world , and we have to control all of their movement and their behavior [ roberta richman - rhode island dept . of corrections ] because that 's the way you keep an institution safe for everybody who lives in it . [ ♪ music ♪ ] we have everybody here— murderers and rapists , sex offenders , drug addicts— everybody . [ 1 out of every 100 americans is currently behind bars ] my name is dennis . i 'm 52 years old . i 'm serving a 15-year sentence for assaulting my wife . my name is louis , 35 . i sold narcotics [ clears throat ] since i was about 13 or so . my name is juan . i 'm 34 years old . i 'm here for second degree murder . yeah . sadly , this is my charge . my name is celine . i 'm 39 . i 'll be 40 soon . i was given a life term . [ ♪ music ♪ ] a lot of times what lands people in prison [ fleet maull - prison mindfulness institute ] and what brings them back is a lack of good problem-solving skills and good communication skills . [ ♪ music ♪ ] [ richman ] fleet approached us asking if he could do some work in here . we were challenged . our union wanted to know how we could possibly bring an ex-offender in . [ maull ] i served 14½ years on a 25-year , no parole sentence . hello . [ ♪ music ♪ ] having served 14 years boosts his credibility— boosts his credibility with inmates . how 's your week been ? - it 's good . [ maull ] yeah ? good . what 's up ? yeah . hey . welcome . when i got locked up , i really hit a wall of just seeing the craziness of my life path up until then and the incredible selfish decisions i 'd been making . my son was 9 years old . he was going to grow up without his dad . and i was just so deeply full of remorse and regret that i just literally started practicing meditation like my hair was on fire . so i became extremely motivated to turn my life around . [ ♪ music ♪ ] and so i was living the life of this prison monk . [ ♪ music ♪ ] i was sourcing a meditation group twice a week in the chapel . [ ♪ music ♪ ] i started receiving letters from prisoners while i was in prison . i had published some articles ; people knew about me out in the world a little bit , and they started sending some of these letters to me thinking i would know what to do with them . i worked in the education department , and i had access to a copy machine . i would copy articles out of books , and i 'd put together a little thing and i 'd send it off to a prisoner . so it started off that way , and i decided it was a much bigger deal than i could do from my prison cells . i think we have a co-creative relationship with our life . we ca n't control other people , we do n't control life , but is there some relationship between what we put out and what comes back ? freedom before i came here was just another word . i had never been to prison before . all you know is what the media and the movies say about prison— `` take care of yourself , man . '' `` somebody 's going to try to take your manhood or something . '' you know what i mean ? i 'm thinking i 'm going to come in here and fight the world . [ maull ] in a prison like moran , there 's a serious conflict waiting around any corner . it 's an environment where people 's worst behaviors are just right there just under the surface . [ ♪ music ♪ ] when i first came in , i fought with officers , would beat up anyone , would do the unthinkable just because . [ dennis ] it 's a vicious cycle because once you come to prison your life just keeps tumbling , tumbling , tumbling , and it 's like a never-ending wall that wo n't stop building unless you find some way to get over that wall or at least in front of it . [ richman ] what circumstances did they have to survive on the street to bring them to where they are now ? do we want to save those lives , or do we want to discard them ? the crimes i committed , i brought shame to not only myself but to those who i love . so i 'm just really trying to do something to get out of that cycle . somebody 's given us an opportunity just to meditate and connect ourselves , and that 's golden . so sit up with that good posture , just rest your hands on your legs , and just take a moment to just feel . [ ♪ music ♪ ] [ richman ] i 've always thought that the people who survive are so much stronger than i could ever be . i asked fleet how he survived and thrived the way he has . he credits meditation for having given him the strength to live his life in prison and come out not as much the worse for wear as most people do . i do n't have a release date . so i can only go home when they decide i can . so i learned to live day by day , and that helped me to deal with prison , and i could only do that being in the moment , being in the now . [ ♪ music ♪ ] it 's like if i do n't like what 's going on , what can i do to shift it ? if i do n't like the relationship i have with my boss or with one of the cos or something , could i approach that person in a different way ? can i get creative about what i 'm doing to bring about a shift in the way things are— in other words , owning my own situation . so how do you resolve that ? i take a breath and then [ chuckles ] i step back . really , you have to . [ maull ] then suddenly get that there 's this whole thing there that they thought was who they are . that 's the only reality they knew . suddenly they get to step outside of that a little bit . you just see the lights go on . it 's like this sudden illumination . it 's like a mini enlightenment of sorts . and that 's very powerful . that 's what keeps me coming . the reality of it is i 'm living life , and meditation it has brought a new perspective in the way that it gave me like a tool to really look inside myself and change the way i am . [ richman ] people do n't understand the value of what they call the soft stuff , and i sometimes think without the soft stuff , no matter how much hard stuff you have , you 're bound to fail . you can live your life . you can be yourself . you can show others that this is n't a place to breed a better criminal ; this could actually be a place to breed a better person . you 're here because the way that you were did n't work . so why not be better ? [ prisoners chattering ] [ richman ] the people in prison are us . they 're not monsters . and more importantly , whether we want them to or not , they 're getting out . so do you want them to come out angrier and meaner and more dangerous than they were when they came in , or do you want to do whatever you can to change their behavior while they 're here ? we need people to see and experience prisoners stepping out of that culture and doing something transformative with their lives , and then people will start to have faith , people will see people coming back to their community and they realize these are human beings and that human beings ' lives have value and they 're not expendable . [ ♪ music ♪ ] [ this year 700,000 people will return home from prison ] [ ♪ music ♪ ] [ directed by emmanuel vaughan-lee , produced by dorothee royal-hedinger ] [ cinematography by elias koch , edited by adam loften , sound recording by emmanuel vaughan-lee ] [ music by h. scott salinas , sound mix by d. chris smith ] [ www.globalonenessproject.org ]
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i was given a life term . [ ♪ music ♪ ] a lot of times what lands people in prison [ fleet maull - prison mindfulness institute ] and what brings them back is a lack of good problem-solving skills and good communication skills . [ ♪ music ♪ ] [ richman ] fleet approached us asking if he could do some work in here .
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what might be some everyday problem solving or communication skills fleet maull is referring to ? how might these skills support a person to make positive choices in lieu of negative choices ?
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all the material objects around you are composed of submicroscopic units we call molecules . and molecules in turn are composed of individual atoms . molecules frequently break apart and then form new molecules . on the other hand , virtually all the atoms you come in to contact with through the course of your life , the ones in the ground beneath you , the air you breath , the food you eat , those that make up every living thing , including you , have existed for billions of years and were created in places very unlike our planet . how those atoms came about is what i want to share with you . it all started 14 billion years ago with an event we call the big bang , which resulted in a universe consisting of gas alone . there were no stars and no planets . the gas was made up only of atoms belonging to the simplest elements . it was about 75 percent hydrogen and almost all the rest was helium . no elements like carbon , oxygen or nitrogen existed . no iron , silver or gold . in some places , the density of this gas was slightly higher than in others . due to gravity , those places attracted even more gas , which further strengthened the pull of gravity , which then drew more gas in , and so on . eventually , large dense gas balls formed , shrinking under their own gravity and consequently heating up on the inside . at some point , the core of such a ball gets hot enough that nuclear fusion occurs . hydrogen atoms smash together to form helium , accompanied by a great release of energy , strong enough to counteract the shrinking force of the gravity . when the energy pushing out from the fusion reactions matches the gravity pulling all the gas inwards , an equilibrium occurs . from this a star is born . over its lifetime , the fusion reactions in the core of a massive star will produce not only helium , but also carbon , oxygen , nitrogen and all the other elements in the periodic table up to iron . but eventually , the core 's fuel runs out , leaving it to collapse completely . that causes an unbelievably powerful explosion we call a supernova . now there are two things to note about how supernovas create elements . first , this explosion releases so much energy that fusion goes wild forming elements with atoms even heavier than iron like silver , gold and uranium . second , all the elements that had been accumulating in the core of the star , like carbon , oxygen , nitrogen , iron , as well as all of those formed in the supernova explosion , are ejected in to interstellar space where they mix with the gas that 's already there . history then repeats itself . gas clouds , now containing many elements besides the original hydrogen and helium , have higher density areas that attract more matter , and so on . as before , new stars result . our sun was born this way about 5 billion years ago . that means that the gas it arose from had itself been enriched with many elements from supernova explosions since the universe began . so that 's how the sun wound up with all the elements . it 's still mostly hydrogen at 71 percent , with most of the rest being helium at 27 percent . but bear in mind that while the first stars were made up of hydrogen and helium alone , the remaining elements in the periodic table make up two percent of the sun . and what about earth ? planets form as an incidental process to star formation out of the same gas cloud as the star itself . small planets like ours do n't have enough gravity to hold on to much hydrogen or helium gas since both of those are very light . so , even though carbon , nitrogen , oxygen and so on made up only two percent of the gas cloud from which earth was formed , these heavier elements form the bulk of our planet and everything on it . think about this : with the exception of hydrogen and some helium , the ground you walk on , the air you breath , you , everything is made of atoms that were created inside stars . when scientists first worked this out over the first half of the 20th century , the famous astronomer harlow shapley commented , `` we are brothers of the boulders , cousins of the clouds . ''
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it was about 75 percent hydrogen and almost all the rest was helium . no elements like carbon , oxygen or nitrogen existed . no iron , silver or gold .
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carbon is a key element in many molecules that make up living creatures . the carbon atoms in your body ________ .
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modern computers are revolutionizing our lives , performing tasks unimaginable only decades ago . this was made possible by a long series of innovations , but there 's one foundational invention that almost everything else relies upon : the transistor . so what is that , and how does such a device enable all the amazing things computers can do ? well , at their core , all computers are just what the name implies , machines that perform mathematical operations . the earliest computers were manual counting devices , like the abacus , while later ones used mechanical parts . what made them computers was having a way to represent numbers and a system for manipulating them . electronic computers work the same way , but instead of physical arrangements , the numbers are represented by electric voltages . most such computers use a type of math called boolean logic that has only two possible values , the logical conditions true and false , denoted by binary digits one and zero . they are represented by high and low voltages . equations are implemented via logic gate circuits that produce an output of one or zero based on whether the inputs satisfy a certain logical statement . these circuits perform three fundamental logical operations , conjunction , disjunction , and negation . the way conjunction works is an `` and gate '' provides a high-voltage output only if it receives two high-voltage inputs , and the other gates work by similar principles . circuits can be combined to perform complex operations , like addition and subtraction . and computer programs consist of instructions for electronically performing these operations . this kind of system needs a reliable and accurate method for controlling electric current . early electronic computers , like the eniac , used a device called the vacuum tube . its early form , the diode , consisted of two electrodes in an evacuated glass container . applying a voltage to the cathode makes it heat up and release electrons . if the anode is at a slightly higher positive potential , the electrons are attracted to it , completing the circuit . this unidirectional current flow could be controlled by varying the voltage to the cathode , which makes it release more or less electrons . the next stage was the triode , which uses a third electrode called the grid . this is a wire screen between the cathode and anode through which electrons could pass . varying its voltage makes it either repel or attract the electrons emitted by the cathode , thus , enabling fast current-switching . the ability to amplify signals also made the triode crucial for radio and long distance communication . but despite these advancements , vacuum tubes were unreliable and bulky . with 18,000 triodes , eniac was nearly the size of a tennis court and weighed 30 tons . tubes failed every other day , and in one hour , it consumed the amount of electricity used by 15 homes in a day . the solution was the transistor . instead of electrodes , it uses a semiconductor , like silicon treated with different elements to create an electron-emitting n-type , and an electron absorbing p-type . these are arranged in three alternating layers with a terminal at each . the emitter , the base , and the collector . in this typical npn transistor , due to certain phenomena at the p-n interface , a special region called a p-n junction forms between the emitter and base . it only conducts electricity when a voltage exceeding a certain threshold is applied . otherwise , it remains switched off . in this way , small variations in the input voltage can be used to quickly switch between high and low-output currents . the advantage of the transistor lies in its efficiency and compactness . because they do n't require heating , they 're more durable and use less power . eniac 's functionality can now be surpassed by a single fingernail-sized microchip containing billions of transistors . at trillions of calculations per second , today 's computers may seem like they 're performing miracles , but underneath it all , each individual operation is still as simple as the flick of a switch .
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circuits can be combined to perform complex operations , like addition and subtraction . and computer programs consist of instructions for electronically performing these operations . this kind of system needs a reliable and accurate method for controlling electric current .
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based on what you have learned , how does a computer add two numbers ?
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flatulence , or passing gas , is a normal daily phenomenon . most individuals , yes , that includes you , will make anywhere from 500-1500 milliliters of gas and can pass gas ten to twenty times a day . but where does this bodily gas come from ? a small proportion may come from ingesting air during sleep , or at other times , but the majority of gas is produced by bacteria in our intestines as they digest parts of food which we can not . our intestine is home to trillions of bacteria living in a symbiotic relationship with us . we provide them with a safe place to stay and food to eat . in exchange , they help us extract energy from our food , make vitamins for us , like vitamin b and k , boost our immune system , and play an important role in gastrointestinal barrier function , motility and the development of various organ systems . clearly , it 's in our best interest to keep these bacteria happy . gut bacteria get their nutrition primarily from undigested food , such as carbohydrates and proteins , which come to the large intestine . they ferment this undigested food to produce a wide range of compounds , such as short-chain fatty acids and , of course , gases . hydrogen and carbon dioxide are the most common gaseous products of bacterial fermentation , and are odorless . some people also produce methane due to specific microbes present in their gut . but methane is actually odorless , too . well then , what stinks ? the foul smell is usually due to volatile sulfur compounds , such as hydrogen sulfide and methanethiol , or methyl mercaptan . these gases , however , constitute less than 1 % of volume , and are often seen with ingestion of amino acids containing sulfur , which may explain the foul smell of gas from certain high protein diets . increased passage of gas is commonly noticed after eating foods with high amounts of indigestible carbohydrates , like beans , lentils , dairy products , onions , garlic , leeks , radishes , potatoes , oats , wheat , cauliflower , broccoli , cabbage , and brussel sprouts . humans lack the enzymes , so the bacteria able to ferment complex carbohydrates take over , and this naturally leads to more gas than usual . but if you feel uncomfortable , bloated or visibly distended , this may indicate impaired movement of gas along the gastrointestinal track . it 's important not to just blame certain foods for gas and bloating and then avoid them . you do n't want to starve the bacteria that digest these complex carbohydrates , or they 'll have to start eating the sugars in the mucus lining of your intestines . your personal gas will vary based on what you eat , and what bacteria are in your gut . for example , from the same starting sugar , the bacteria clostridium produces carbon dioxide , butyrate and hydrogen , while propionibacterium can produce carbon dioxide , propionate and acetate . at the same time , methanogens can use hydrogen and carbon dioxide produced by other bacteria to generate methane , which can reduce the total volume of gas by using up hydrogen and carbon dioxide . so there 's a complex web among intestinal bacteria allowing them to flourish by either directly consuming undigested food , or using what other bacteria produce . this interaction largely determines the amount and type of gas produced , so gas production is a sign that your gut bacteria are at work . but in some instances , people may develop abnormal increased flatulence . a common example is lactose intolerance . most individuals have the enzyme for breaking down lactose , a sugar present in milk and milk-derived products . but some people either lack it entirely , or have a reduced amount , such as after a gastrointestinal infection , so they 're unable to digest lactose products and may experience cramping , along with increased flatulence due to bacterial fermentation . but remember , most gas is produced as a natural result of bacterial fermentation in the intestine , and indicates healthy functioning of the gut . the amount and type can vary based on your diet and the bacteria in your intestine . exercise social courtesy while passing gas , and do try to forgive your bacteria . they 're only trying to be helpful .
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hydrogen and carbon dioxide are the most common gaseous products of bacterial fermentation , and are odorless . some people also produce methane due to specific microbes present in their gut . but methane is actually odorless , too .
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the smell humans produce from flatulence is due to :
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translator : jennifer cody reviewer : jessica ruby when faced with a big challenge where potential failure seems to lurk at every corner , maybe you 've heard this advice before : `` be more confident . '' and most likely , this is what you think when you hear it : `` if only it were that simple . '' but what is confidence ? take the belief that you are valuable , worthwhile , and capable , also known as self-esteem , add in the optimism that comes when you are certain of your abilities , and then empowered by these , act courageously to face a challenge head-on . this is confidence . it turns thoughts into action . so where does confidence even come from ? there are several factors that impact confidence . one : what you 're born with , such as your genes , which will impact things like the balance of neurochemicals in your brain . two : how you 're treated . this includes the social pressures of your environment . and three : the part you have control over , the choices you make , the risks you take , and how you think about and respond to challenges and setbacks . it is n't possible to completely untangle these three factors , but the personal choices we make certainly play a major role in confidence development . so , by keeping in mind a few practical tips , we do actually have the power to cultivate our own confidence . tip 1 : a quick fix . there are a few tricks that can give you an immediate confidence boost in the short term . picture your success when you 're beginning a difficult task , something as simple as listening to music with deep bass ; it can promote feelings of power . you can even strike a powerful pose or give yourself a pep talk . tip two : believe in your ability to improve . if you 're looking for a long-term change , consider the way you think about your abilities and talents . do you think they are fixed at birth , or that they can be developed , like a muscle ? these beliefs matter because they can influence how you act when you 're faced with setbacks . if you have a fixed mindset , meaning that you think your talents are locked in place , you might give up , assuming you 've discovered something you 're not very good at . but if you have a growth mindset and think your abilities can improve , a challenge is an opportunity to learn and grow . neuroscience supports the growth mindset . the connections in your brain do get stronger and grow with study and practice . it also turns out , on average , people who have a growth mindset are more successful , getting better grades , and doing better in the face of challenges . tip three : practice failure . face it , you 're going to fail sometimes . everyone does . j.k. rowling was rejected by twelve different publishers before one picked up `` harry potter . '' the wright brothers built on history 's failed attempts at flight , including some of their own , before designing a successful airplane . studies show that those who fail regularly and keep trying anyway are better equipped to respond to challenges and setbacks in a constructive way . they learn how to try different strategies , ask others for advice , and perservere . so , think of a challenge you want to take on , realize it 's not going to be easy , accept that you 'll make mistakes , and be kind to yourself when you do . give yourself a pep talk , stand up , and go for it . the excitement you 'll feel knowing that whatever the result , you 'll have gained greater knowledge and understanding . this is confidence .
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but if you have a growth mindset and think your abilities can improve , a challenge is an opportunity to learn and grow . neuroscience supports the growth mindset . the connections in your brain do get stronger and grow with study and practice .
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give some examples of things people might say which indicate they have a fixed mindset ? how would you correct these statements to help them develop a growth mindset ?
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sometimes when a fish is reeled up to the surface it will appear inflated , with its eyes bulging out of their sockets and its stomach projecting out of its mouth , as if its been blown up like a balloon . this type of bodily damage , caused by rapid changes in pressure , is called barotrauma . under the sea , pressure increases by 14.7 pounds per square inch for every 33 foot increase in depth . so , take the yelloweye rockfish , which can live as deep as 1800 feet , where there 's over 800 pounds of pressure on every square inch . that 's equivalent to the weight of a polar bear balancing on a quarter . now , boyle 's gas law states that the volume of a gas is inversely related to pressure . so , any air-filled spaces , like a rockfish 's swim bladder , or human lungs , will compress as they descend deeper and expand as they ascend . after a fish bites a fisherman 's hook and is quickly reeled up to the surface , the air in its swim bladder begins to expand . its rapid expansion actually forces the fish 's stomach out of its mouth , while the increased internal pressure pushes its eyes out of their sockets , a condition called exophthalmia . sometimes rockfish eyes will even have a crystallized appearance from corneal emphysemas , little gas bubbles that build up inside the cornea . thankfully , a scuba diver does n't have a closed swim bladder to worry about . a diver can regulate pressure in her lungs by breathing out as she ascends , but must be wary of other laws of physics that are at play under the sea . henry 's law states that the amount of a gas that dissolves in a liquid is proportional to its partial pressure . the air a diver breathes is 78 % nitrogen . at a higher pressure under the sea , the nitrogen from the air in a scuba tank diffuses into a diver 's tissues in greater concentrations than it would on land . if the diver ascends too quickly , this built up nitrogen can come out of solution and form microbubbles in her tissues , blood and joints , causing decompression sickness , aka the bends . this is similar to the fizz of carbon dioxide coming out of your soda . gas comes out of solution when the pressure 's released . but for a diver , the bubbles cause severe pain and sometimes even death . divers avoid falling victim to the bends by rising slowly and taking breaks along the way , called decompression stops , so the gas has time to diffuse back out of their tissues and to be released through their breath . just as a diver needs decompression , for a fish to recover , it needs recompression , which can be accomplished by putting it back in the sea . but that does n't mean that fish should just be tossed overboard . an inflated body will float and get scooped up by a hungry sea lion or pecked at by seagulls . there 's a common myth that piercing its stomach with a needle will let air escape , allowing the fish to swim back down on its own . but that is one balloon that should n't be popped . to return a fish properly to its habitat , fisherman can use a descending device instead to lower it on a fishing line and release it at the right depth . as it heads home and recompression reduces gas volume , its eyes can return to their sockets and heal , and its stomach can move back into place . this fish will live to see another day , once more free to swim , eat , reproduce and replenish the population .
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but for a diver , the bubbles cause severe pain and sometimes even death . divers avoid falling victim to the bends by rising slowly and taking breaks along the way , called decompression stops , so the gas has time to diffuse back out of their tissues and to be released through their breath . just as a diver needs decompression , for a fish to recover , it needs recompression , which can be accomplished by putting it back in the sea . but that does n't mean that fish should just be tossed overboard .
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what is the best way to put a rockfish back into the sea ?
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what happens after death ? is there a restful paradise ? an eternal torment ? a rebirth ? or maybe just nothingness ? well , one chinese emperor thought that whatever the hereafter was , he better bring an army . we know that because in 1974 , farmers digging a well near their small village stumbled upon one of the most important finds in archeological history : vast underground chambers surrounding that emperor 's tomb , and containing more than 8,000 life-size clay soldiers ready for battle . the story of the subterranean army begins with ying zheng , who came to power as the king of the qin state at the age of 13 in 246 bce . ambitious and ruthless , he would go on to become qin shi huangdi , the first emperor of china after uniting its seven warring kingdoms . his 36 year reign saw many historic accomplishments , including a universal system of weights and measures , a single standardized writing script for all of china , and a defensive barrier that would later come to be known as the great wall . but perhaps qin shi huangdi dedicated so much effort to securing his historical legacy because he was obsessed with his mortality . he spent his last years desperately employing alchemists and deploying expeditions in search of elixirs of life that would help him achieve immortality . and as early as the first year of his reign , he began the construction of a massive underground necropolis filled with monuments , artifacts , and an army to accompany him into the next world and continue his rule . this magnificent army is still standing in precise battle formation and is split across several pits . one contains a main force of 6,000 soldiers , each weighing several hundred pounds , a second has more than 130 war chariots and over 600 horses , and a third houses the high command . an empty fourth pit suggests that the grand project could not be finished before the emperor 's death . in addition , nearby chambers contain figures of musicians and acrobats , workers and government officials , and various exotic animals , indicating that emperor qin had more plans for the afterlife than simply waging war . all the figurines are sculpted from terracotta , or baked earth , a type of reddish brown clay . to construct them , multiple workshops and reportedly over 720,000 laborers were commandeered by the emperor , including groups of artisans who molded each body part separately to construct statues as individual as the real warriors in the emperor 's army . they stand according to rank and feature different weapons and uniforms , distinct hairstyles and expressions , and even unique ears . originally , each warrior was painted in bright colors , but their exposure to air caused the paint to dry and flake , leaving only the terracotta base . it is for this very reason that another chamber less than a mile away has not been excavated . this is the actual tomb of qin shi huangdi , reported to contain palaces , precious stones and artifacts , and even rivers of mercury flowing through mountains of bronze . but until a way can be found to expose it without damaging the treasures inside , the tomb remains sealed . emperor qin was not alone in wanting company for his final destination . ancient egyptian tombs contain clay models representing the ideal afterlife , the dead of japan 's kofun period were buried with sculptures of horses and houses , and the graves of the jaina island off the mexican coast are full of ceramic figurines . fortunately , as ruthless as he was , emperor qin chose to have servants and soldiers built for this purpose , rather than sacrificing living ones to accompany him , as had been practiced in egypt , west africa , anatolia , parts of north america and even china during the previous shang and zhou dynasties . and today , people travel from all over the world to see these stoic soldiers silently awaiting their battle orders for centuries to come .
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this is the actual tomb of qin shi huangdi , reported to contain palaces , precious stones and artifacts , and even rivers of mercury flowing through mountains of bronze . but until a way can be found to expose it without damaging the treasures inside , the tomb remains sealed . emperor qin was not alone in wanting company for his final destination .
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within the tombs , archeologists found all of the following except :
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hendrix , cobain and page . they can all shred , but how exactly do the iconic contraptions in their hands produce notes , rhythm , melody and music . when you pluck a guitar string , you create a vibration called a standing wave . some points on the string , called nodes , do n't move at all , while other points , anti-nodes , oscillate back and forth . the vibration translates through the neck and bridge to the guitar 's body , where the thin and flexible wood vibrates , jostling the surrounding air molecules together and apart . these sequential compressions create sound waves , and the ones inside the guitar mostly escape through the hole . they eventually propagate to your ear , which translates them into electrical impulses that your brain interprets as sound . the pitch of that sound depends on the frequency of the compressions . a quickly vibrating string will cause a lot of compressions close together , making a high-pitched sound , and a slow vibration produces a low-pitched sound . four things affect the frequency of a vibrating string : the length , the tension , the density and the thickness . typical guitar strings are all the same length , and have similar tension , but vary in thickness and density . thicker strings vibrate more slowly , producing lower notes . each time you pluck a string , you actually create several standing waves . there 's the first fundamental wave , which determines the pitch of the note , but there are also waves called overtones , whose frequencies are multiples of the first one . all these standing waves combine to form a complex wave with a rich sound . changing the way you pluck the string affects which overtones you get . if you pluck it near the middle , you get mainly the fundamental and the odd multiple overtones , which have anti-nodes in the middle of the string . if you pluck it near the bridge , you get mainly even multiple overtones and a twangier sound . the familiar western scale is based on the overtone series of a vibrating string . when we hear one note played with another that has exactly twice its frequency , its first overtone , they sound so harmonious that we assign them the same letter , and define the difference between them as an octave . the rest of the scale is squeezed into that octave divided into twelve half steps whose frequency is each 2^ ( 1/12 ) higher than the one before . that factor determines the fret spacing . each fret divides the string 's remaining length by 2^ ( 1/12 ) , making the frequencies increase by half steps . fretless instruments , like violins , make it easier to produce the infinite frequencies between each note , but add to the challenge of playing intune . the number of strings and their tuning are custom tailored to the chords we like to play and the physiology of our hands . guitar shapes and materials can also vary , and both change the nature and sound of the vibrations . playing two or more strings at the same time allows you to create new wave patterns like chords and other sound effects . for example , when you play two notes whose frequencies are close together , they add together to create a sound wave whose amplitude rises and falls , producing a throbbing effect , which guitarists call the beats . and electric guitars give you even more to play with . the vibrations still start in the strings , but then they 're translated into electrical signals by pickups and transmitted to speakers that create the sound waves . between the pickups and speakers , it 's possible to process the wave in various ways , to create effects like distortion , overdrive , wah-wah , delay and flanger . and lest you think that the physics of music is only useful for entertainment , consider this . some physicists think that everything in the universe is created by the harmonic series of very tiny , very tense strings . so might our entire reality be the extended solo of some cosmic jimi hendrix ? clearly , there 's a lot more to strings than meets the ear .
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each fret divides the string 's remaining length by 2^ ( 1/12 ) , making the frequencies increase by half steps . fretless instruments , like violins , make it easier to produce the infinite frequencies between each note , but add to the challenge of playing intune . the number of strings and their tuning are custom tailored to the chords we like to play and the physiology of our hands .
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why can you distinguish between instruments even when they are playing the same note ?
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translator : tom carter reviewer : bedirhan cinar dialogue gives a story color , makes it exciting and moves it forward . romeo : o , wilt thou leave me so unsatisfied ? juliet : what satisfaction canst thou have tonight ? romeo : the exchange of thy love 's faithful vows for mine . without dialogue : ( cricket sounds ) so what goes into writing effective dialogue ? well , there are social skills : making friends , solving conflicts , being pleasant and polite . we wo n't be using any of those today . instead , we 'll be working on -- let 's call them `` anti-social skills . '' if you 're a writer , you may already have a few of these . the first is eavesdropping . if you 're riding a bus and hear an interesting conversation , you could write it all down . of course , when you write fiction , you 're not describing real people , you 're making up characters . but sometimes the words you overhear can give you ideas . `` i did not , '' says one person . `` i saw you , '' the other replies . who might be saying those words ? maybe it 's two kids in a class , and the boy thinks the girl pushed him . maybe it 's a couple , but one of them is a vampire , and the woman vampire saw the man flirting with a zombie . or maybe not . maybe the characters are a teenager and his mother , and they 're supposed to be vegetarians , but the mother saw him eating a burger . so let 's say you 've decided on some characters . this is anti-social skill number two : start pretending they 're real . what are they like ? where are they from ? what music do they listen to ? spend some time with them . if you 're on a bus , think about what they might be doing if they were there too . would they talk on the phone , listen to music , draw pictures , sleep ? what we say depends on who we are . an older person might speak differently than a younger person . someone from the south might speak differently than someone from the north . once you know your characters , you can figure out how they talk . at this stage , it 's helpful to use anti-social skill number three : muttering to yourself . when you speak your character 's words , you can hear whether they sound natural , and fix them if necessary . remember , most people are usually pretty informal when they speak . they use simple language and contractions . so , `` do not attempt to lie to me '' sounds more natural as `` do n't try to lie to me . '' also keep it short . people tend to speak in short bursts , not lengthy speeches . and let the dialogue do the work . ask yourself : do i really need that adverb ? for instance , `` 'your money or your life , ' she said threateningly . '' here , `` threateningly '' is redundant , so you can get rid of it . but if the words and the actions do n't match , an adverb can be helpful . `` 'your money or your life , ' she said lovingly . '' so , to recap : first , eavesdrop . next , pretend imaginary people are real . finally , mutter to yourself , and write it all down . you already have everything you need . this is fictional dialogue , or `` how to hear voices in your head . ''
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romeo : the exchange of thy love 's faithful vows for mine . without dialogue : ( cricket sounds ) so what goes into writing effective dialogue ? well , there are social skills : making friends , solving conflicts , being pleasant and polite .
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read the discussions of wuthering heights and crime and punishment in the article , “ creating effective dialogue , ” by william h. coles ( available at http : //fictioneditorsopinions.com/2009/08/creating-effective-dialog/ ) . now , consider some examples of fictional dialogue that you ’ ve particularly enjoyed reading . what do you think made the dialogue effective ? which techniques did the author seem to be using ?
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humans have been fascinated with speed for ages . the history of human progress is one of ever-increasing velocity , and one of the most important achievements in this historical race was the breaking of the sound barrier . not long after the first successful airplane flights , pilots were eager to push their planes to go faster and faster . but as they did so , increased turbulence and large forces on the plane prevented them from accelerating further . some tried to circumvent the problem through risky dives , often with tragic results . finally , in 1947 , design improvements , such as a movable horizontal stabilizer , the all-moving tail , allowed an american military pilot named chuck yeager to fly the bell x-1 aircraft at 1127 km/h , becoming the first person to break the sound barrier and travel faster than the speed of sound . the bell x-1 was the first of many supersonic aircraft to follow , with later designs reaching speeds over mach 3 . aircraft traveling at supersonic speed create a shock wave with a thunder-like noise known as a sonic boom , which can cause distress to people and animals below or even damage buildings . for this reason , scientists around the world have been looking at sonic booms , trying to predict their path in the atmosphere , where they will land , and how loud they will be . to better understand how scientists study sonic booms , let 's start with some basics of sound . imagine throwing a small stone in a still pond . what do you see ? the stone causes waves to travel in the water at the same speed in every direction . these circles that keep growing in radius are called wave fronts . similarly , even though we can not see it , a stationary sound source , like a home stereo , creates sound waves traveling outward . the speed of the waves depends on factors like the altitude and temperature of the air they move through . at sea level , sound travels at about 1225 km/h . but instead of circles on a two-dimensional surface , the wave fronts are now concentric spheres , with the sound traveling along rays perpendicular to these waves . now imagine a moving sound source , such as a train whistle . as the source keeps moving in a certain direction , the successive waves in front of it will become bunched closer together . this greater wave frequency is the cause of the famous doppler effect , where approaching objects sound higher pitched . but as long as the source is moving slower than the sound waves themselves , they will remain nested within each other . it 's when an object goes supersonic , moving faster than the sound it makes , that the picture changes dramatically . as it overtakes sound waves it has emitted , while generating new ones from its current position , the waves are forced together , forming a mach cone . no sound is heard as it approaches an observer because the object is traveling faster than the sound it produces . only after the object has passed will the observer hear the sonic boom . where the mach cone meets the ground , it forms a hyperbola , leaving a trail known as the boom carpet as it travels forward . this makes it possible to determine the area affected by a sonic boom . what about figuring out how strong a sonic boom will be ? this involves solving the famous navier-stokes equations to find the variation of pressure in the air due to the supersonic aircraft flying through it . this results in the pressure signature known as the n-wave . what does this shape mean ? well , the sonic boom occurs when there is a sudden change in pressure , and the n-wave involves two booms : one for the initial pressure rise at the aircraft 's nose , and another for when the tail passes , and the pressure suddenly returns to normal . this causes a double boom , but it is usually heard as a single boom by human ears . in practice , computer models using these principles can often predict the location and intensity of sonic booms for given atmospheric conditions and flight trajectories , and there is ongoing research to mitigate their effects . in the meantime , supersonic flight over land remains prohibited . so , are sonic booms a recent creation ? not exactly . while we try to find ways to silence them , a few other animals have been using sonic booms to their advantage . the gigantic diplodocus may have been capable of cracking its tail faster than sound , at over 1200 km/h , possibly to deter predators . some types of shrimp can also create a similar shock wave underwater , stunning or even killing pray at a distance with just a snap of their oversized claw . so while we humans have made great progress in our relentless pursuit of speed , it turns out that nature was there first .
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where the mach cone meets the ground , it forms a hyperbola , leaving a trail known as the boom carpet as it travels forward . this makes it possible to determine the area affected by a sonic boom . what about figuring out how strong a sonic boom will be ? this involves solving the famous navier-stokes equations to find the variation of pressure in the air due to the supersonic aircraft flying through it .
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when is a sonic boom generated ?
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okay , i 've got a piece of crystalline bismuth , so you can actually take sort of pellets of bismuth , metal , and heat it up , i 've seen photos of people doing that on their home cookers , their ovens and things , but you can make them in the lab so you get crystals of bismuth out which look like this which is actually really really pretty and there are websites of people who 've made these crystals and they 're selling them for collectors and things which is quite nice . bismuth is interesting because it is the heaviest element that is not radioactive . you can imagine the nucleus , the center of the atom , rather like a drop of water , and if you imagine a drop of water as it gets bigger and bigger it becomes unstable and will usually split into two , and it just happens that bismuth is the largest size that 's not radioactive . - the interesting thing about bismuth actually is that it 's long been regarded , bismuth 209 has long been regarded as the heaviest non-radioactive element , and technically actually that 's not true . it was actually found i think about 5 years ago now , it was actually proven to be an alpha emitter , so it 's actually a radioactive element , that emits alpha particles . - so here is a very old sample of bismuth . this is a bismuth rod and as you can see it 's packed up really quite nicely , but if we open this then we can go in and see what it is in here . let 's see . here if we pull it out carfully . - but actually it 's kind of a little bit pedantic i suppose because the half life of this bismuth 209 they 've found is actually 1.9x10 to the power of 19 years . its half life , that 's the time it takes a kilo of bismuth , for 500 grams of it to decompose to its daughter element which i think is thalium 205 if i 'm right , and so that half life is actually longer than the current age of the universe , so for all intents and purposes , it 's still quite stable and i think they actually call it meta stable . - it is used particularly in an alloy which they call woods metal , which is a very low melting alloy , will even melt in boiling water , and there are endless practical jokes where you can buy woods metal spoons and give it to somebody to stir their tea and it melted in their tea and they look suprised . - bismuth . really old sample from johnson matthey and let 's see if we can find out what the purity is , so it 's 99.9 % , really a quite nice sample of a bismuth rod . - bismuth suprisingly is not very poisonous compared to the fact that led is very poisonous , and so there are some suggestions that we should be exploring more the chemistry of bismuth as a catalist because if it works well then it can be used in chemical processes with much less danger than some of these other materials . - so if we can push it out from this old paper package then you can see it 's packaged really quite nicely , here you can see the bismuth metal itself , bismuth is used in catalysis to attenuate selective reactions so perhaps we might use bismuth with a platinum group metal like paladium or platinum even to make chemistry work even more selectively , it 's a really beautiful element then . really nice , so we 'll pop that back in there nice and safe . - what have you got there , where did that come from ? - i bought it because it 's so pretty , i bought it from a shop , i ca n't remember actually which shop now , but i collect these sorts of things . these very big pretty looking sort of metallic things and crystals and as you can see it 's really nice and irradescent so it 's got a tarnished oxide layer and it shines like all the colors of the rainbow which is really really pretty in my opinion . lovely ! captions by www.subply.com
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- it is used particularly in an alloy which they call woods metal , which is a very low melting alloy , will even melt in boiling water , and there are endless practical jokes where you can buy woods metal spoons and give it to somebody to stir their tea and it melted in their tea and they look suprised . - bismuth . really old sample from johnson matthey and let 's see if we can find out what the purity is , so it 's 99.9 % , really a quite nice sample of a bismuth rod .
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what is the composition of the oxide of bismuth and other metals called bisco or bscco that have superconducting properties at temperatures up to -164ºc ?
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so this is a sample of ruthenium sponge . so the ruthenium metal has been precipitated to form very fine particles . so here we will just open the box i am rather ashamed that i made a big mistake about the name of ruthenium . i thought it referred to somewhere in middle europe perhaps in czechoslovakia whereas ruthenium actually comes from ruthenia which is the latin translation for the country that is now called russia and , in fact , the element ruthenium was first discovered in russia in the city of kazan . why would that be a particular cause of shame for you ? well , because my father was born in russia and therefore to get something connected to russia wrong is a bit embarrassing . the ruthenium is a very , very reactive metal especially when it is formed in this very fine sponge type material . ruthenium was actually discovered relatively early in the middle of the 19th century . there is some discussion , whether in fact the swedish chemist berzelius analysed something that contained ruthenium and missed it or not , but i am not quite sure about that . but the reason why i am interested in this is because i did my doctorate with a supervisor and if you look at his supervisor and then that ö then go back one supervisor after another you eventually get to the swedish chemist berzelius who was my great , great , great , great , great , great , great supervisor and you will find that most of the chemists now working in the world were related to just a few pioneering chemists in the 18th century . so the ruthenium is very finely divided and if i tip it you can see in the bottom of the vial very fine powders but again because of the particle size this is really dark , very black , very nice sample of ruthenium very useful for catalytic chemistry . it is as a catalyst that ruthenium is particularly famous . ruthenium itself if you look at a lump of the metal is a kind of silvery colour . this is a sample of ruthenium as a catalyst . now because it is an expensive metal the ruthenium is just distributed as a very thin layer on silica . silica is like sand and you can see that this finely divided ruthenium looks black . they are very finely divided so it has a large surface area so the molecules can come in and react it . and my students were using this catalyst to react an organic compound , that is one with carbon and hydrogen and to get it to react with more hydrogen and so they lent me this catalyst so i could show it to you . there are other ruthenium catalysts which dissolve in the solution that you are trying to get the reaction to go . and there is a very famous catalyst named after the american chemist bob grubbs , who won the nobel prize about 4 years ago , and his catalyst does a reaction which most people even some chemists had not heard of called which is called metathesis in which double bonds between two carbon atoms are broken and joined together in a different way . and you can use this for all sorts of things you can make plastics out of oils ; you can make new sorts of wax ; you can make a really great sort of wax that has oxygen atoms in it ; and if you use this for candles then the oxygen atoms make fragrance molecules dissolve much better than in ordinary wax . so you can have a christmas candle which , when you light it , smells of christmas pudding or smells of alcohol or vanilla or whatever spice you want . you canít do that with an ordinary wax but this ruthenium catalyst opens up all sorts of things so that is why he got the nobel prize . he got the nobel prize because he made nice smelling candles ? no , he got the nobel prize because he invented the catalyst that opened up all sorts of reactions that otherwise could not be done . bob grubbs compound has ruthenium and his is the most widely used and it is now used in a whole series of industrial processes . this is another compound of ruthenium which you can see is a rather nice red colour and it has the rather unromantic name of ruthenium bpy three times or chemists who use it call it rubpy . and the point about this compound is that it absorbs light well and it is very stable , you can shine light on it , very intense light for a long time and the compound does not decompose , it does not change . but what it can do when you shine light is that you can move electrons around inside the compound and this compound and ones like it are being used by people to try and capture the light from the sun - capture solar energy
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so the ruthenium is very finely divided and if i tip it you can see in the bottom of the vial very fine powders but again because of the particle size this is really dark , very black , very nice sample of ruthenium very useful for catalytic chemistry . it is as a catalyst that ruthenium is particularly famous . ruthenium itself if you look at a lump of the metal is a kind of silvery colour .
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who won the 2005 nobel prize in chemistry , using his famous ruthenium catalyst in olefin metathesis reactions ?
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humans have been fascinated with speed for ages . the history of human progress is one of ever-increasing velocity , and one of the most important achievements in this historical race was the breaking of the sound barrier . not long after the first successful airplane flights , pilots were eager to push their planes to go faster and faster . but as they did so , increased turbulence and large forces on the plane prevented them from accelerating further . some tried to circumvent the problem through risky dives , often with tragic results . finally , in 1947 , design improvements , such as a movable horizontal stabilizer , the all-moving tail , allowed an american military pilot named chuck yeager to fly the bell x-1 aircraft at 1127 km/h , becoming the first person to break the sound barrier and travel faster than the speed of sound . the bell x-1 was the first of many supersonic aircraft to follow , with later designs reaching speeds over mach 3 . aircraft traveling at supersonic speed create a shock wave with a thunder-like noise known as a sonic boom , which can cause distress to people and animals below or even damage buildings . for this reason , scientists around the world have been looking at sonic booms , trying to predict their path in the atmosphere , where they will land , and how loud they will be . to better understand how scientists study sonic booms , let 's start with some basics of sound . imagine throwing a small stone in a still pond . what do you see ? the stone causes waves to travel in the water at the same speed in every direction . these circles that keep growing in radius are called wave fronts . similarly , even though we can not see it , a stationary sound source , like a home stereo , creates sound waves traveling outward . the speed of the waves depends on factors like the altitude and temperature of the air they move through . at sea level , sound travels at about 1225 km/h . but instead of circles on a two-dimensional surface , the wave fronts are now concentric spheres , with the sound traveling along rays perpendicular to these waves . now imagine a moving sound source , such as a train whistle . as the source keeps moving in a certain direction , the successive waves in front of it will become bunched closer together . this greater wave frequency is the cause of the famous doppler effect , where approaching objects sound higher pitched . but as long as the source is moving slower than the sound waves themselves , they will remain nested within each other . it 's when an object goes supersonic , moving faster than the sound it makes , that the picture changes dramatically . as it overtakes sound waves it has emitted , while generating new ones from its current position , the waves are forced together , forming a mach cone . no sound is heard as it approaches an observer because the object is traveling faster than the sound it produces . only after the object has passed will the observer hear the sonic boom . where the mach cone meets the ground , it forms a hyperbola , leaving a trail known as the boom carpet as it travels forward . this makes it possible to determine the area affected by a sonic boom . what about figuring out how strong a sonic boom will be ? this involves solving the famous navier-stokes equations to find the variation of pressure in the air due to the supersonic aircraft flying through it . this results in the pressure signature known as the n-wave . what does this shape mean ? well , the sonic boom occurs when there is a sudden change in pressure , and the n-wave involves two booms : one for the initial pressure rise at the aircraft 's nose , and another for when the tail passes , and the pressure suddenly returns to normal . this causes a double boom , but it is usually heard as a single boom by human ears . in practice , computer models using these principles can often predict the location and intensity of sonic booms for given atmospheric conditions and flight trajectories , and there is ongoing research to mitigate their effects . in the meantime , supersonic flight over land remains prohibited . so , are sonic booms a recent creation ? not exactly . while we try to find ways to silence them , a few other animals have been using sonic booms to their advantage . the gigantic diplodocus may have been capable of cracking its tail faster than sound , at over 1200 km/h , possibly to deter predators . some types of shrimp can also create a similar shock wave underwater , stunning or even killing pray at a distance with just a snap of their oversized claw . so while we humans have made great progress in our relentless pursuit of speed , it turns out that nature was there first .
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these circles that keep growing in radius are called wave fronts . similarly , even though we can not see it , a stationary sound source , like a home stereo , creates sound waves traveling outward . the speed of the waves depends on factors like the altitude and temperature of the air they move through . at sea level , sound travels at about 1225 km/h . but instead of circles on a two-dimensional surface , the wave fronts are now concentric spheres , with the sound traveling along rays perpendicular to these waves .
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the speed of sound depends on :
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so , we ’ re braving the elements brady , to repeat the experiment that we did quite some time ago , so you will remember that we had a very small balloon of hydrogen match on a stick to hydrogen , big bang coming ! are you ready ? yep ! here we go ! and the fact that we ’ ve come outside , might actually give you an idea of what we are going to do , cause we are going to make it a little bit bigger , so let ’ s go and fill a balloon . alright , cool . well , hydrogen , i think is very important because , it is the simplest atom , it ’ s the atom , consists of a positively charged proton which is relatively large and a negatively charged electron , that goes round it . electric match ? i think an electric match will go well on that . yep . oh , look at the tension on the balloon ! hold it , i ’ ve really gone for it and blown that one up . the tension ! what happens is that hydrogen is reacting with oxygen and h2 plus o2 reacts to form h2o and an oxygen atom and then that oxygen atom goes on to react with another hydrogen molecule to make more water and the reaction generates a lot of heat and that heat , heats up more gas to make it react faster , so you generate more and more heat , so the reaction that begins quite slowly with the first few molecules , runs away and that is why you get the explosion . so here we have a rather large balloon of hydrogen , neil is just preparing our electric match which we are going to attach to the side of this balloon . and some of the biggest explosions in the 20th century , the chernobyl reactor , the space shuttle that blew up when it was taking off , were in fact explosions caused by hydrogen and oxygen . so we ’ ve filled up a balloon of hydrogen , and i think if you look at the hydrogen balloon you will see that it is slightly larger than those we have attempted before . now we are going to try to detonate it or burn the hydrogen , in the air by giving it a match and the match we are going to use is again an electric match , which is connected to our detonator box . if you stick a pin in the balloon , the balloon will burst because the rubber will break , but the hydrogen will come out and it won ’ t react with the oxygen because the hydrogen is cool , it ’ s at the same temperature as the air , but the reaction of hydrogen and oxygen like many reactions involves so called activation energy , you have to put in a certain amount of energy to get it going . but once you get it going , you get more heat coming out , than you put in to start it off . so , let ’ s arm the circuit , 5-4-3-2-1 . that was more like it . lovely ! when pete puts the match to the balloon , first of all the match burns a hole in the balloon , and then the heat gets the hydrogen and oxygen near the outside of the balloon and they start reacting and the heat then spreads through the volume of the hydrogen and oxygen , faster probably than the balloon is bursting and as it spreads through the temperature builds up and up and up because you are generating so much heat . the reason that you hear a noise , is because , it causes a rise in pressure which sends a pressure wave out through the air and it hits your ears or the microphone on your camera . i honestly don ’ t know why you see any colour . i suspect that the colour may actually be caused by the burning balloon which contains carbon and is really like the flame on a candle . because normally when you have a hydrogen/oxygen flame you don ’ t see any colour at all . alternatively , it may be some impurities in the gas , but i suspect that what you are seeing in the fire ball is just the burning of the balloon . the other thing which is really quite exciting about hydrogen is that in principle if you heat hydrogen to really high temperatures , you can get two hydrogen atoms to fuse together , or rather , it will not work with hydrogen , but it will work with a heavier form of hydrogen which is know as deuterium where instead of a proton and an electron , you have a proton and a neutron , which is a neutral particle , and an electron , and two molecules of deuterium can fuse together to make one atom of helium which has two protons , two neutrons , and two electrons and this produces a lot of energy . it is the basis of the so-called hydrogen bombs , which are like super atomic bombs , but which require an enormously high temperature to get the reaction to go . you can probably hear it hitting and fizzing into the bottle there . there is great hope that in the end much of the world ’ s energy crisis can be solved by doing this so called nuclear fusion of deuterium to make helium which would produce energy extremely cleanly . so here , we ’ ll just tie it off , if my welsh hands can actually tie a knot on a balloon , ‘ cause , you know we are all a little bit bizarre . deuterium gas , in all its properties , will be very similar to that of hydrogen , of course it is denser , because it has a neutron as well as a proton but it is still much lighter than air so a deuterium balloon will still float up to the ceiling and make pete look just as stupid as the hydrogen one . you ’ ve got to keep hold of it . or you lose it or you lose it , you know ! i was thinking more of fusing it , that sounds like a really big explosion we could do out the back . no ! fusing reactors are way beyond what pete can do unless he is a lot cleverer than i think . i got a balloon ! i had a balloon of hydrogen ! that is the second time you have done that ! now it ’ s going to go up there eventually anyway !
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i got a balloon ! i had a balloon of hydrogen ! that is the second time you have done that !
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most hydrogen is produced industrially by steam reforming of natural gas . electrolysis of water also produces hydrogen , but it is used less frequently . can you write the general equation for the electrolysis of water ?
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translator : andrea mcdonough reviewer : bedirhan cinar you 've probably heard of pavlov 's dogs , the phrase that often summarizes dr. ivan pavlov 's early 20th century research , in which he demonstrated that we can alter what stimuli elicit a reflective response in canines . he showed this by sounding a bell just before he presented his group of dogs with meat powder . after many presentations of the bell , followed by tasty meat powder , the dogs eventually began to salivate at just the sound of the bell . they salivated even when there was no meat powder present . this phenomenon is n't limited to dogs . consider the placebo effect , in which a pill with no active substances brings about a response similar to a pill with a substance present . what changes here is our reaction to our ailment , such as perceiving less pain and not the ailment itself . or , consider the love humans have for a parent . some would argue that this love is instinctual , and they may be partially right . but , the argument fails to account for the equal amount of love that children adopted later in life hold for their adoptive parents . but the behaviorist argument can account for both accounts of love . a parent , biological or not , is constantly paired with things like food , smiles , toys , affection , games , protection , and entertainment . and a parent 's constant association with these wonderful or crucial aspects of a child 's life has a similar , albeit more complicated , effect that meat powder had on pavlov 's salivating dogs . in other words , if one 's parent is predictive of really good or really important things , then one 's parent becomes a really good and important thing , too . and there is also romantic advice to be gained from pavlov 's observations . we all need food to survive , right ? and someone who can provide such things in a delicious , saliva-producing manner stands to become our human equivalent of a ringing bell . in other words , if you can cook one or more scrumptious meals for a potential love interest , there 's a good chance that you 'll be viewed more favorably in the future , even if you did n't prepare the delicious food . and who would n't want the love of their life drooling over them ? but life is not just bell rings and salivation . there 's also a dark side to this type of learning , called `` taste aversion '' . taste aversion occurs when we ingest some food that eventually makes us sick , and , as a result , we avoid that food , sometimes for the rest of our lives . taste aversion is so powerful that the effect can be seen even if the illness is experienced hours later and even if the food itself did not actually make us sick . such is the case when we have the flu , and , by accident , we ingest some food moments prior to vomiting . in this case , we know that the food did not cause the vomiting , but our bodies do n't know that . and the next time we encounter that food , we are likely to refuse eating it . now , imagine the potential consequences of undercooking a meal on a first date . if the food makes your date sick , it is possible for them to associate that bad feeling with not just the food , but with < i > your < /i > food in particular . if the episode was traumatizing enough , or if it also happens on a subsequent date , they may come to relate you with the consequences , just like pavlov 's dogs related the bell with the meat powder . in other words , the sight of you showing up at the next dinner date might actually make your date nauseous ! as the old saying goes , the fastest way to someone 's heart is through their stomach , assuming you do n't make them sick in the process .
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they salivated even when there was no meat powder present . this phenomenon is n't limited to dogs . consider the placebo effect , in which a pill with no active substances brings about a response similar to a pill with a substance present .
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what is the name for the phenomenon in which we avoid certain foods that make us ill ?
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cloudy climate change : how clouds affect earth 's temperature . earth 's average surface temperature has warmed by .8 celsius since 1750 . when carbon dioxide concentrations in the atmosphere have doubled , which is expected before the end of the 21st century , researchers project global temperatures will have risen by 1.5 to 4.5 degrees celsius . if the increase is near the low end , 1.5 celsius , then we 're already halfway there , and we should be more able to adapt with some regions becoming drier and less productive , but others becoming warmer , wetter and more productive . on the other hand , a rise of 4.5 degrees celsius would be similar in magnitude to the warming that 's occurred since the last glacial maximum 22,000 years ago , when most of north america was under an ice sheet two kilometers thick . so that would represent a dramatic change of climate . so it 's vitally important for scientists to predict the change in temperature with as much precision as possible so that society can plan for the future . the present range of uncertainty is simply too large to be confident of how best to respond to climate change . but this estimate of 1.5 to 4.5 celsius for a doubling of carbon dioxide has n't changed in 35 years . why have n't we been able to narrow it down ? the answer is that we do n't yet understand aerosols and clouds well enough . but a new experiment at cern is tackling the problem . in order to predict how the temperature will change , scientists need to know something called earth 's climate sensitivity , the temperature change in response to a radiative forcing . a radiative forcing is a temporary imbalance between the energy received from the sun and the energy radiated back out to space , like the imbalance caused by an increase of greenhouse gases . to correct the imbalance , earth warms up or cools down . we can determine earth 's climate sensitivity from the experiment that we 've already performed in the industrial age since 1750 and then use this number to determine how much more it will warm for various projected radiative forcings in the 21st century . to do this , we need to know two things : first , the global temperature rise since 1750 , and second , the radiative forcing of the present day climate relative to the pre-industrial climate . for the radiative forcings , we know that human activities have increased greenhouse gases in the atmosphere , which have warmed the planet . but our activities have at the same time increased the amount of aerosol particles in clouds , which have cooled the planet . pre-industrial greenhouse gas concentrations are well measured from bubbles trapped in ice cores obtained in greenland and antarctica . so the greenhouse gas forcings are precisely known . but we have no way of directly measuring how cloudy it was in 1750 . and that 's the main source of uncertainty in earth 's climate sensitivity . to understand pre-industrial cloudiness , we must use computer models that reliably simulate the processes responsible for forming aerosols in clouds . now to most people , aerosols are the thing that make your hair stick , but that 's only one type of aerosol . atmospheric aerosols are tiny liquid or solid particles suspended in the air . they are either primary , from dust , sea spray salt or burning biomass , or secondary , formed by gas to particle conversion in the atmosphere , also known as particle nucleation . aerosols are everywhere in the atmosphere , and they can block out the sun in polluted urban environments , or bathe distant mountains in a blue haze . more importantly , a cloud droplet can not form without an aerosol particle seed . so without aerosol particles , there 'd be no clouds , and without clouds , there 'd be no fresh water . the climate would be much hotter , and there would be no life . so we owe our existence to aerosol particles . however , despite their importance , how aerosol particles form in the atmosphere and their effect on clouds are poorly understood . even the vapors responsible for aerosol particle formation are not well established because they 're present in only minute amounts , near one molecule per million million molecules of air . this lack of understanding is the main reason for the large uncertainty in climate sensitivity , and the corresponding wide range of future climate projections . however , an experiment underway at cern , named , perhaps unsurprisingly , `` cloud '' has managed to build a steel vessel that 's large enough and has a low enough contamination , that aerosol formation can , for the first time , be measured under tightly controlled atmospheric conditions in the laboratory . in its first five years of operation , cloud has identified the vapors responsible for aerosol particle formation in the atmosphere , which include sulfuric acid , ammonia , amines , and biogenic vapors from trees . using an ionizing particle beam from the cern proton synchrotron , cloud is also investigating if galactic cosmic rays enhance the formation of aerosols in clouds . this has been suggested as a possible unaccounted natural climate forcing agent since the flux of cosmic rays raining down on the atmosphere varies with solar activity . so cloud is addressing two big questions : firstly , how cloudy was the pre-industrial climate ? and , hence , how much have clouds changed due to human activities ? that knowledge will help sharpen climate projections in the 21st century . and secondly , could the puzzling observations of solar climate variability in the pre-industrial climate be explained by an influence of galactic cosmic rays on clouds ? ambitious but realistic goals when your head 's in the clouds .
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even the vapors responsible for aerosol particle formation are not well established because they 're present in only minute amounts , near one molecule per million million molecules of air . this lack of understanding is the main reason for the large uncertainty in climate sensitivity , and the corresponding wide range of future climate projections . however , an experiment underway at cern , named , perhaps unsurprisingly , `` cloud '' has managed to build a steel vessel that 's large enough and has a low enough contamination , that aerosol formation can , for the first time , be measured under tightly controlled atmospheric conditions in the laboratory .
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what is the main reason for the large range of uncertainty in future climate projections ?
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cadmium ? yes ok oh yeah , that ’ s some ! that is cool man ! so cadmium is an element which is really quite similar to mercury and the way that most people have seen cadmium is that cadmium sulphide has a very strong orange colour and it is therefore used for dying things yellow or orange . if you look round your house or your parents ’ house , you may easily find a cast iron pot which has , a cooking pot , which has nice orange sides and orange lid and this is using cadmium sulphide as a glaze . so this is a sample which was generated or which was used by some of our researchers in the school of chemistry many years ago and this is a sample of cadmium metal . now it ’ s very interesting because it is stored in this really quite nice box which was perhaps a medication that somebody had bought , but if we open it… it 's also i believe , to colour the plastic pipe that you see in the street for gas pipes and so on . i think it is coloured with a cadmium compound . now in both these applications , even though that cadmium is quite poisonous , that they are so strongly fixed into the materials that it isn ’ t a threat to people . and we can see the lumps of the metallic cadmium . now i am not going to touch the cadmium because we know of some of the issues with toxicity . but it is used very often in batteries , or it was traditionally used in batteries . it is really important that we dispose of our batteries in a correct way .
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cadmium ? yes ok oh yeah , that ’ s some !
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when he showed to us , why didn ’ t pete touch the cadmium metal lumps ?
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english , like all languages , is a messy business . you can be uncouth but not couth . you can be ruthless , but good luck trying to show somebody that you have ruth unless you happen to be married to someone named ruth . it 's bad to be unkempt but impossible to be kempt , or sheveled as opposed to disheveled . there are other things that make no more sense than those but that seem normal now because the sands of time have buried where they came from . for example , did you ever wonder why a nickname for edward is ned ? where 'd the n come from ? it 's the same with nellie for ellen . afterall , if someone 's name is ethan , we do n't nickname him nethan , nor do we call our favorite maria , nmaria . in fact , if anyone did , our primary urge would be to either scold them or gently hide them away until the company had departed . all these nicknames trace back to a mistake , although , a perfectly understandable one . in fact , even the word nickname is weird . what 's so `` nick '' about a nickname ? is it that it 's a name that has a nick in it ? let 's face it , not likely . actually , in old english , the word was ekename , and eke meant also or other . you can see eke still used in chaucer 's < em > canterbury tales < /em > in a sentence like , `` whan zephyrus eek with his sweete breeth , '' which meant , `` when zephyr also with his sweet breath . '' ekename meant `` also name . '' what happened was that when people said , `` an ekename , '' it could sound like they were saying , `` a nekename , '' and after a while , so many people were hearing it that way that they started saying , `` that 's my nickname , '' instead of , `` that 's my ekename . '' now , the word had a stray n at the front that started as a mistake , but from now on was what the word really was . it was rather as if you had gum on the bottom of your shoe and stepped on a leaf , dragged that leaf along for the rest of your life , were buried wearing that shoe and went to heaven in it to spend eternity wedded to that stray , worn-out leaf . ekename picked up an n and never let it go . the same thing happened with other words . old english speakers cut otches into wood . but after centuries of being asked to cut an otch into something , it was easy to think you were cutting a notch instead , and pretty soon you were . in a world where almost no one could read , it was easier for what people heard to become , after awhile , what it started to actually be . here 's where the ned-style nicknames come in . old english was more like german than our english is now , and just as in german , my is mein , in old english , my was meen . you would say meen book , actually boke in old english , or meen cat . and just as today , we might refer to our child as my dahlia or my laura , in old english , they would say , `` meen ed '' . that is mein ed , mein ellie . you see where this is going . as time passed , meen morphed into the my we know today . that meant that when people said , `` mein ed , '' it sounded like they were saying my ned . that is , it sounded like whenever someone referred to edward affectionately , they said ned instead of ed . behold , the birth of a nickname ! or an ekename . hence , also nellie for ellen and nan for ann , and even in the old days , nabby for abigal . president john adam 's wife abigail 's nickname was nabby . all sorts of words are like this . old english speakers wore naprons , but a napron sounds like an apron , and that gave birth to a word apron that no one in beowulf would have recognized . umpire started as numpires , too . if all of this sounds like something sloppy that we modern people would never do , then think about something you hear all the time and probably say , `` a whole nother . '' what 's nother ? we have the word another , of course , but it 's composed of an and other , or so we thought . yet , when we slide whole into the middle , we do n't say , `` a whole other , '' we clip that n off of the an and stick it to other and create a new word , nother . for a long time , nobody was writing these sort of things down or putting them in a dictionary , but that 's only because writing is more codified now than it was 1,000 years ago . so , when you see a weird word , remember that there might be a whole nother side to the story .
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old english speakers cut otches into wood . but after centuries of being asked to cut an otch into something , it was easy to think you were cutting a notch instead , and pretty soon you were . in a world where almost no one could read , it was easier for what people heard to become , after awhile , what it started to actually be .
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if language changed so much in the past , then why do you think we tend to think of changes in the language today as slang or mistakes ?
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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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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 .
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what are the similarities and differences between beta-agonist and corticosteroid inhalers ? which one would you use for long-term control ? for immediate symptom relief ?
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tens of millions of years ago , a force of nature set two giant masses on an unavoidable collision course that would change the face of the earth and spell life or death for thousands of species . the force of nature was plate tectonics , and the bodies were north and south america . and even though they were hurdling towards each other at an underwhelming 2.5 cm per year , their collision actually did have massive biological reprocussions by causing one of the greatest episodes of biological migration in earth 's history : the great american biotic interchange . our story begins 65 million years ago , the beginning of the age of mammals , when what is now north and south america were continents separated by a marine connection between the pacific and atlantic oceans . during this time , south america was the home of fauna that included armored glyptodonts as large as compact cars , giant ground sloths weighing more than a ton , opossums , monkeys , and carnivorous terror birds . north america had its own species , such as horses , bears , and saber-toothed cats . over 20 million years , the shifting of the farallon and caribbean plates produced the central america volcanic arc , a peninsula connected to north america , with only a very narrow seaway separating it from south america . as these plates continued to surf the earth 's magma layer far beneath the pacific ocean floor , the caribbean plate migrated eastward , and about 15 million years ago , south america finally collided with this central american arc . this gradually closed the water connection between the pacific and the caribbean , creating a land bridge , which connected north america to south america . terrestrial organisms could now cross between the two continents , and from the fossil records , it 's evident that different waves of their dispersals took place . even though plants do n't physically move , they are easily dispersed by wind and waves , so they migrated first , along with a few species of birds . they were followed by some freshwater fishes and amphibians , and finally , various mammals began to traverse the bridge . from south america , mammals like ground sloths and glyptodonts were widly distributed in north america . moreover , many south american tropical mammals , like monkeys and bats , colonized the forests of central america , and are very abundant today . south american predator marsupials went extinct 3 million years ago , at which point north american predators , such as cats , bears and foxes , migrated south and occupied the ecological space left behind . horses , llamas , tapirs , cougars , saber-toothed cats , gomphotheres , and later humans also headed south across the land bridge . but what happened on land is only half the story . what had been one giant ocean was now two , creating differences in temperature and salinity for the two bodies of water . the isthmus also became a barrier for many marine organisms , like mollusks , crustaceans , foraminifera , bryozoans , and fish , and separated the populations of many marine species . it also allowed the establishment of the thermohaline circulation , a global water conveyor belt , which transports warm water across the atlantic , and influences the climate of the east coast of north america , the west coast of europe , and many other areas . it 's a challenge to track all of the ways the collision of the americas changed the world , but it 's safe to say that the ripples of the great american biotic interchange have propagated through the history of life on the planet , and that of mankind . what if these species had n't gone extinct , or if there were no monkeys in central america , or jaguars in south america ? what if the thermohaline circulation was n't flowing ? would the east coast of north america be much colder ? it all goes to show some of the most impactful transformations of our planet are n't the explosive ones that happen in an instant , but the ones that crawl towards irreversible change . we are the product of history .
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they were followed by some freshwater fishes and amphibians , and finally , various mammals began to traverse the bridge . from south america , mammals like ground sloths and glyptodonts were widly distributed in north america . moreover , many south american tropical mammals , like monkeys and bats , colonized the forests of central america , and are very abundant today .
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when did the collision between north and south america take place ?
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have you ever had someone try to explain something to you a dozen times with no luck – but , then , when you see a picture , the idea finally clicks ? if that sounds familiar , maybe you might consider yourself a visual learner . or , if reading or listening does the trick , maybe you feel like you ’ re a verbal learner . we call these labels learning styles , but is there /really/ a way to categorize different types of students ? well , it actually seems like /multiple/ presentation formats , especially if one of them is visual , help most people learn . when psychologists and educators test for learning styles , they ’ re trying to figure out whether these are inherent traits that affect how well students learn , instead of just a preference . usually , they start by giving a survey to figure out what style a student favors , like visual or verbal learning . then , they try to teach the students something with a specific presentation style , like using visual aids , and do a follow-up test to see how much they learned . that way , the researchers can see if the self-identified verbal learners really learned better when the information was just spoken aloud , for example . but , according to a 2008 review , only /one/ study that followed this design found that students actually learned best with their preferred style… and it had some pretty big flaws . the researchers excluded two-thirds of the original participants because they did n't seem to have /any/ clear learning style from the survey at the beginning . plus , they removed outliers from the data if they thought they were “ extreme , ” without defining exactly what that meant . and , they did n't even report the actual test scores in the final paper . so ... it doesn ’ t really seem like learning styles are an inherent trait that we all have . but , that does n't mean that all students will do amazingly if they just spend all their time reading from a textbook . instead , /most people/ seem to learn better if they ’ re taught in several ways – especially if one is visual . in one study , researchers tested whether students remembered lists of words better if they heard them , saw them , or both . and everyone seemed to do better if they got to see the words in print , even the self-identified auditory learners . that preference did n't seem to matter . similar studies tested whether students learned basic physics and chemistry concepts better by reading plain text or viewing pictures , too . and everyone did better with the help of pictures . so the question of whether or not you 're a visual learner could best be answered with : `` well , yeah , kinda . but so are most people . '' thanks for asking , and thanks especially to all of our patrons on patreon who keep these answers coming . if you ’ d like to submit questions to be answered , or get some videos a few days early , go to patreon.com/scishow . and don ’ t forget to go to youtube.com/scishow and subscribe !
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when psychologists and educators test for learning styles , they ’ re trying to figure out whether these are inherent traits that affect how well students learn , instead of just a preference . usually , they start by giving a survey to figure out what style a student favors , like visual or verbal learning . then , they try to teach the students something with a specific presentation style , like using visual aids , and do a follow-up test to see how much they learned .
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what makes any learning aid ( verbal , auditory , visual , etc . ) most effective ?
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in many ways , our memories make us who we are , helping us remember our past , learn and retain skills , and plan for the future . and for the computers that often act as extensions of ourselves , memory plays much the same role , whether it 's a two-hour movie , a two-word text file , or the instructions for opening either , everything in a computer 's memory takes the form of basic units called bits , or binary digits . each of these is stored in a memory cell that can switch between two states for two possible values , 0 and 1 . files and programs consist of millions of these bits , all processed in the central processing unit , or cpu , that acts as the computer 's brain . and as the number of bits needing to be processed grows exponentially , computer designers face a constant struggle between size , cost , and speed . like us , computers have short-term memory for immediate tasks , and long-term memory for more permanent storage . when you run a program , your operating system allocates area within the short-term memory for performing those instructions . for example , when you press a key in a word processor , the cpu will access one of these locations to retrieve bits of data . it could also modify them , or create new ones . the time this takes is known as the memory 's latency . and because program instructions must be processed quickly and continuously , all locations within the short-term memory can be accessed in any order , hence the name random access memory . the most common type of ram is dynamic ram , or dram . there , each memory cell consists of a tiny transistor and a capacitor that store electrical charges , a 0 when there 's no charge , or a 1 when charged . such memory is called dynamic because it only holds charges briefly before they leak away , requiring periodic recharging to retain data . but even its low latency of 100 nanoseconds is too long for modern cpus , so there 's also a small , high-speed internal memory cache made from static ram . that 's usually made up of six interlocked transistors which do n't need refreshing . sram is the fastest memory in a computer system , but also the most expensive , and takes up three times more space than dram . but ram and cache can only hold data as long as they 're powered . for data to remain once the device is turned off , it must be transferred into a long-term storage device , which comes in three major types . in magnetic storage , which is the cheapest , data is stored as a magnetic pattern on a spinning disc coated with magnetic film . but because the disc must rotate to where the data is located in order to be read , the latency for such drives is 100,000 times slower than that of dram . on the other hand , optical-based storage like dvd and blu-ray also uses spinning discs , but with a reflective coating . bits are encoded as light and dark spots using a dye that can be read by a laser . while optical storage media are cheap and removable , they have even slower latencies than magnetic storage and lower capacity as well . finally , the newest and fastest types of long-term storage are solid-state drives , like flash sticks . these have no moving parts , instead using floating gate transistors that store bits by trapping or removing electrical charges within their specially designed internal structures . so how reliable are these billions of bits ? we tend to think of computer memory as stable and permanent , but it actually degrades fairly quickly . the heat generated from a device and its environment will eventually demagnetize hard drives , degrade the dye in optical media , and cause charge leakage in floating gates . solid-state drives also have an additional weakness . repeatedly writing to floating gate transistors corrodes them , eventually rendering them useless . with data on most current storage media having less than a ten-year life expectancy , scientists are working to exploit the physical properties of materials down to the quantum level in the hopes of making memory devices faster , smaller , and more durable . for now , immortality remains out of reach , for humans and computers alike .
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sram is the fastest memory in a computer system , but also the most expensive , and takes up three times more space than dram . but ram and cache can only hold data as long as they 're powered . for data to remain once the device is turned off , it must be transferred into a long-term storage device , which comes in three major types . in magnetic storage , which is the cheapest , data is stored as a magnetic pattern on a spinning disc coated with magnetic film .
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among the properties of a memory device ( speed , capacity , cost , data life-span ) which one , in your opinion is the most important , and why ?
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translator : andrea mcdonough reviewer : bedirhan cinar people often think the word `` doubt '' spelling is a little crazy because of the letter `` b '' . since it does n't spell a sound , most folks ca n't figure out what it 's doing there . but in spite of what most of us learn in school , sound is < i > never < /i > the most important aspect of spelling an english word . a word 's meaning and history need to come first . to doubt means to question , to waver , to hesitate . as a noun , it means uncertainty or confusion . the present-day english word `` doubt '' started as a latin word , `` dubitare '' . it first moved from latin into french where it lost both its `` buh '' sound and its letter `` b '' . and then it came into english in the 13th century . about 100 years later , scribes who wrote english but also knew latin , started to reinsert the `` b '' into the word 's spelling , even though no one pronounced it that way . but why would they do this ? why would anyone in their right mind reinsert a silent letter into a spelling ? well , because they knew latin , the scribes understood that the root of `` doubt '' had a `` b '' in it . over time , even as fewer literate people knew latin , the `` b '' was kept because it marked important , meaningful connections to other related words , like `` dubious '' and `` indubitalbly , '' which were subsequently borrowed into english from the same latin root , `` dubitare '' . understanding these historical connections not only helped us to spell `` doubt , '' but also to understand the meaning of these more sophisticated words . but the story does n't end there . if we look even deeper , we can see beyond the shadow of a doubt , just how revealing that `` b '' can be . there are only two base words in all of english that have the letters `` d-o-u-b '' : one is doubt , and the other is double . we can build lots of other words on each of these bases , like doubtful and doubtless , or doublet , and redouble , and doubloon . it turns out that if we look into their history , we can see that they both derive from the same latin forms . the meaning of double , two , is reflected in a deep understanding of doubt . see , when we doubt , when we hesitate , we second guess ourselves . when we have doubts about something , when we have questions or confusion , we are of two minds . historically , before english began to borrow words from french , it already had a word for doubt . that old english word was `` tweogan , '' a word whose relationship to `` two '' is clear in its spelling as well . so the next time you are in doubt about why english spelling works the way it does , take a second look . what you find just might make you do a double-take .
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since it does n't spell a sound , most folks ca n't figure out what it 's doing there . but in spite of what most of us learn in school , sound is < i > never < /i > the most important aspect of spelling an english word . a word 's meaning and history need to come first . to doubt means to question , to waver , to hesitate .
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according to cooke , sound is never the most important aspect of spelling an english word . what should come first ?
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so today we ’ re going to look at bromine . so this is bromine , it ’ s a small sample , about 2 or 3 grammes . bromine is a red liquid . there are not many elements that are actually liquid : caesium , mercury , gallium and bromine . it ’ s this beautiful red colour and it has an unpleasant smell . bromine comes from the greek word bromos which means stench , a really horrible smell . in fact this bromine probably comes from near where i did my degree because in europe , the second , well the largest producer of bromine in europe is the octale company which is based on amlwch on anglesey which is where i went last weekend . so it ’ s a nice sample . we ’ re going to get it out of this bottle now because it ’ s sealed in because it ’ s obviously very , very volatile as a liquid and we ’ re going to cut the glass , get it out and look at its chemistry . thanks neil . bromine is also quite a common element in the world . it is found in sea water as bromide , it ’ s also found particularly in the dead sea between israel and jordan where there are very concentrated solutions of bromide . so you can make bromine just by bubbling chlorine into a solution of bromide like dead sea water and the chlorine displaces the bromine and forms chloride and the bromine just comes out as red fumes which you can catch . so neil ’ s now using a glass knife to open the ampoule and he ’ s going to pour the liquid bromine into this small evaporating dish inside our fume hood . now instantly you can see the vapour of the bromine coming off . you see all those really nice orange fumes which are coming off from the liquid and then they ’ re being drawn away by our fume hood . bromine has a number of uses , it is particularly used in plastics as an additive to try and make them less flammable . if you ’ re watching your videos on a screen which has a plastic surround almost certainly that surround will contain bromine to make it less flammable . bromine itself is strongly oxidising so we thought we ’ d do an oxidation reaction today . and that reaction is to take another element and here we have aluminium , simple aluminium foil , like you wrap your dinner in , and we ’ re now going to put some small amounts of aluminium foil into the bromine liquid . so we put it in and it generally takes a few moments for this reaction to start but as i said , the aluminium is strongly oxidising . it oxidises and generates aluminium tribromide . which is a beautiful nice material but it ’ s a strongly exothermic reaction . so let ’ s see what happens . this may initiate . it is also an unusual element because elements have different isotopes these are the same form of the element but with different numbers of neutrons in the atoms so they weigh different amounts . usually you get one isotope that is very common and another one that is only a small amount . bromine is unusual because it has two isotopes 79 and 81 which have almost equal quantities in nature so that they have approximately 51 % of one and 49 % of the other which is really quite unusual . so here we see the exothermic oxidation and formation of aluminium tribromide . so the reaction is strongly exothermic which means it gives out energy and that energy then evaporates off excess bromine which you can see coming off as a vapour . a wonderful exothermic reaction : very , very fast , very , very rapid forming aluminium tribromide . bromine is quite dangerous but it is less dangerous than chlorine because it ’ s a liquid at room temperature . chlorine is a gas so if you let out chlorine it disperses everywhere . with bromine it is a heavy gas which can disperse rather more slowly . so now as the reaction cools down we can see that the volume of bromine is significantly reduced . reacts with water quite well .
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so this is bromine , it ’ s a small sample , about 2 or 3 grammes . bromine is a red liquid . there are not many elements that are actually liquid : caesium , mercury , gallium and bromine .
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bromine is a liquid at room temperature . what is the melting point of bromine at atmospheric pressure ?
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have you ever talked with a friend about a problem only to realize that he just does n't seem to grasp why the issue is so important to you ? have you ever presented an idea to a group and it 's met with utter confusion ? or maybe you 've been in an argument when the other person suddenly accuses you of not listening to what they 're saying at all ? what 's going on here ? the answer is miscommunication , and in some form or another , we 've all experienced it . it can lead to confusion , animosity , misunderstanding , or even crashing a multimillion dollar probe into the surface of mars . the fact is even when face-to-face with another person , in the very same room , and speaking the same language , human communication is incredibly complex . but the good news is that a basic understanding of what happens when we communicate can help us prevent miscommunication . for decades , researchers have asked , `` what happens when we communicate ? '' one interpretation , called the transmission model , views communication as a message that moves directly from one person to another , similar to someone tossing a ball and walking away . but in reality , this simplistic model does n't account for communication 's complexity . enter the transactional model , which acknowledges the many added challenges of communicating . with this model , it 's more accurate to think of communication between people as a game of catch . as we communicate our message , we receive feedback from the other party . through the transaction , we create meaning together . but from this exchange , further complications arise . it 's not like the star trek universe , where some characters can vulcan mind meld , fully sharing thoughts and feelings . as humans , we ca n't help but send and receive messages through our own subjective lenses . when communicating , one person expresses her interpretation of a message , and the person she 's communicating with hears his own interpretation of that message . our perceptual filters continually shift meanings and interpretations . remember that game of catch ? imagine it with a lump of clay . as each person touches it , they shape it to fit their own unique perceptions based on any number of variables , like knowledge or past experience , age , race , gender , ethnicity , religion , or family background . simultaneously , every person interprets the message they receive based on their relationship with the other person , and their unique understanding of the semantics and connotations of the exact words being used . they could also be distracted by other stimuli , such as traffic or a growling stomach . even emotion might cloud their understanding , and by adding more people into a conversation , each with their own subjectivities , the complexity of communication grows exponentially . so as the lump of clay goes back and forth from one person to another , reworked , reshaped , and always changing , it 's no wonder our messages sometimes turn into a mush of miscommunication . but , luckily , there are some simple practices that can help us all navigate our daily interactions for better communication . one : recognize that passive hearing and active listening are not the same . engage actively with the verbal and nonverbal feedback of others , and adjust your message to faciliate greater understanding . two : listen with your eyes and ears , as well as with your gut . remember that communication is more than just words . three : take time to understand as you try to be understood . in the rush to express ourselves , it 's easy to forget that communication is a two-way street . be open to what the other person might say . and finally , four : be aware of your personal perceptual filters . elements of your experience , including your culture , community , and family , influence how you see the world . say , `` this is how i see the problem , but how do you see it ? '' do n't assume that your perception is the objective truth . that 'll help you work toward sharing a dialogue with others to reach a common understanding together .
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engage actively with the verbal and nonverbal feedback of others , and adjust your message to faciliate greater understanding . two : listen with your eyes and ears , as well as with your gut . remember that communication is more than just words .
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what can we do to listen more effectively ?
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to understand what 's happening with greece and the eurozone , think about a dinner party . if you 're cooking just for yourself and your spouse , it 's easy : you make something you both like . but if you 've got guests , things get harder . if you need to accommodate a vegetarian , and someone who is gluten free , and someone with a soy allergy , your options get really limited . and that 's the problem with europe 's idea of having a whole bunch of countries all use the same currency . so greece 's economy is in a disaster . a quarter of the population is unemployed , and it has this very high debt burden . normally , if you 've got really high unemployment , what happens is that a country makes its currency cheaper by printing extra money . that makes its products cheaper on world markets , it makes it a more attractive tourist destination , and it means that foreign investors can get great bargains . but if unemployment is really low , a country likes to have an expensive currency . that increases people 's purchasing power and it keeps prices down . and in europe , you have a bunch of economies that are really different . a price of euros that 's appropriate for greece , where they have a 25 % unemployment rate is way too low for germany , where the unemployment rate is below 5 % . and greece 's problem is that it 's small , poor , and geographically isolated from the rest of the eurozone . it 's like the only vegetarian at a barbeque , except when it comes to currencies , there 's no side dishes . and so there 's plenty of specific decisions we can second-guess , plenty of things greece did and various banks did that we can question , but fundamentally having all these countries come to a dinner party with only one dish on the menu was a mistake . the euro was a project that europe set about on for really political reasons . it was a symbol of their determination to have peace on the continent , but they did n't really take the economics of it seriously . so greece joins the euro in 2001 and initially , it works out great for greece because all of a sudden everyone was like 'yeah , sure , let 's lend them money . ' so they borrowed lots and lots and lots of euros , except that did n't change the fact that their economy is a lot weaker than some of the other european countries . so to really work , you would need a much , much , much closer union , where you had big financial transfers coming from the richer places to the poorer places all the time . in the united states , the poor states like kentucky , mississippi , alabama , they 're constantly getting money from the richer states like massachusetts , california , new york , through the welfare system , through social security , through medicare , through medicaid . and you know , people may complain about this or that program , but we do n't dispute the idea that it 's all one country so money is going to circulate around . europeans , you know , they just do n't feel that way . germans are willing to support poor german people , but they do n't want to support greek people with their tax dollars . so they 're kind of like half-way integrated in a way that does n't really work .
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so greece 's economy is in a disaster . a quarter of the population is unemployed , and it has this very high debt burden . normally , if you 've got really high unemployment , what happens is that a country makes its currency cheaper by printing extra money . that makes its products cheaper on world markets , it makes it a more attractive tourist destination , and it means that foreign investors can get great bargains .
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the major factors that led to the present greek debt crisis could be attributed to excess borrowing , premature entry to single currency , high interest rates or other factors . according to the video , discuss which one is the most significant and why .
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françois-marie arouet was born in paris in 1694 his father , a well-established lawyer , sent him to the best school in the capital , and by all accounts , he was a brilliant student . the young arouet , decided at an early age to make his name as a writer , or rather to remake his name , as the first thing he did was to change his name to voltaire . the 18th century is often referred to as the age of reason , or the age of enlightenment , but sometimes more fairly simply as the age of voltaire . so , changing his name was a good call . the age of arouet , which is not of work quite as well . voltaire was precociously talented as a poet . at the age of only 24 , he had his first verse tragedy performed at the comédie-française . by then , he 'd already begun work on an epic poem about the french religious civil wars of the 16th century , about the french religious civil wars of the 16th century , by pragmatically converting from protestantism to catholicism . this was to be a subject dear to voltaire 's heart , for under the guise of writing a national epic , he was dwelling at length on the bloody consequences of religious intolerance . right from the start , voltaire 's views on religion were expressed robustly . he was not an atheist . in part , because he thought that some minimal belief in a deity was useful for social cohesion . voltaire 's god had created the world , instilled in us a sense of good and evil and then basically taken a back seat . this was known as rational religion , or in the 18th century called natural religion , or deism . and it had no truck with metaphysics of any kind . voltaire was basically a man of reason , who loathed fanaticism , idolatry and superstition . that men can kill each other to defend some bit of religious doctrine , which they scarcely understand , is something he found repellent . and he reserved his greatest hatred for the clerics , who exploited the credulity of believers to maintain their own power base . voltaire wanted religion but not the church . for obvious reasons , the catholic authorities were not keen for voltaire 's poem about henry iv , la henriade , to be published in france . so voltaire decided to go and publish it in london instead , and in 1726 , went and traveled to england . what began as a business trip soon turned , however , into something quite different . and voltaire ended up staying in england for some two and a half years . he learned to speak english fluently , got to know writers and politicians , and became a great admirer of english protestant culture . he decided to write a book about his experience of england . and the letters concerning the english nation appeared first in english in 1733 . the french authorities were horrified . the book was censored and voltaire only narrowly avoided prison . that 's because the book presented an informal portrait of english culture , in a witty and ironical style looking in turn at religion , politics , science and literature , in ways that were critical implicitly of french culture and politics . here , for example , is how voltaire presents the royal exchange , a handsome building in the heart of the city of london , where merchants from across the world would meet to transact business . `` take a view of the royal exchange , '' voltaire wrote , where the representatives of all nations meet for the benefit of mankind . there the jew , the muhammadan and a christian transact together as though they all profess the same religion , and give the name of infidel to none but the bankrupts . there the presbyterian confides in the anabaptist , and the churchman depends on the quaker ’ s word . at the breaking up of this pacific and free assembly , some will withdraw to the synagogue , and others to take a glass . this man goes and is baptised in a great tub , in the name of the father , son and holy ghost : that man has his son ’ s foreskin cut off , whilst a set of hebrew words ( quite unintelligible to him ) are mumbled over his child . if one religion only were allowed in england , the government would very possibly become arbitrary ; if there were but two , the people would cut one another ’ s throats ; but as there as such a multitude , they all live happy and in peace . '' voltaire 's message is clear . religious differences are trivial and separate men , while trade is important and brings them together . his conclusion , that the plurality of religions in england leads to a more peaceful society , is , of course , a covert criticism of france , where the catholic church was so dominant . the letters concerning the english nation , also discuss locke and newton , thinkers then poorly known in france the subject-matter might seem challenging , but voltaire is a past master popularising difficult material . ask any schoolchild today what they know about newton , and they 'll tell you about the apple falling on his head , and the survival of this anecdote is due entirely to voltaire . he heard it from newton 's niece and immediately understood that this simple homely image was the perfect way of conveying the simplicity of newton 's explanation of the force of gravity . after voltaire used the story in his letters concerning the english nation , everyone remembered it and voltaire left his mark on english popular culture . voltaire struggled with the question of good and evil the problem at the heart of his best-known work , candide which was published in 1759 and was a best seller from the moment it appeared . translated into every possible language , it remains the most widely read work of the european enlightenment . it 's even left its mark on our language expressions like 'pour encourager les autres ' to encourage the others or 'il faut cultiver le jardin ' , we must cultivate our garden have entered common usage . 'in the best of all possible worlds ' , yes , that 's another one speakers of french or english quote candide , without even realising it . and that 's the sure mark of a classic . candide is a timeless work , as satire of the human condition , but it 's also work of the enlightenment and its philosophical theme is announced in the title : `` candide '' or `` optimism '' . the hero of candide , as his name tells us , is an innocent anti-hero . he is in thrall to his tutor , pangloss , who preaches the philosophy of optimism . this is not 'optimism ' in the modern sense of looking on the bright side . optimism , spelled with a capital o and as expounded by the german philosopher , leibniz , was an attempt to answer the age-old problem of evil . why , if god is good , does he permit the existence of evil in the world ? to which the 18th century leibnizian optimist replies , evil is all part of some greater pattern of good : 'all partial evil , universal good ' as the english poet `` pope '' put it . in other words , evil does n't really exist at all . it 's just something which man imagines because of his limited view of the world . you might think this sounds like a bit of a confidence trick , voltaire certainly did , but this idea did find widespread acceptance in the 18th century . candide 's great mission was to put this philosophy to the test . ejected from his comfortable home in an obscure german castle , after trying to seduce the baron 's beautiful daughter , cunégonde , voltaire 's hero , candide , undergoes many trials and tribulations : conscripted into the army , he fights in a war , then deserts , only to find himself a witness to an earthquake in lisbon . candide is repeatedly brought face to face with evil in its most extreme forms : moral evil , in the case of the earthquake , where man is not apparently to blame ; and most of all human evil , such as the war , where man is very definitely to blame . pangloss 's breezy optimism is clearly an inadequate response to enormities of evil on this scale . eventually , even candide comes to realize this : to quote from the book , 'and sometimes pangloss would say to candide : after 1760 , voltaire took up residence in the château at ferney , just outside geneva . by now , he was the most famous living writer in europe , and he became widely known as the ‘ patriarch of ferney ’ . he took up a number of public causes . in 1761 , a protestant merchant jean calas , was accused of murdering his son and sentenced by the judges of toulouse to be tortured and then broken on the wheel . the legal processes were , to say the least , irregular , and the suspicions grew that the judges in his catholic city had acted with excessive zeal out of religious bigotry . voltaire became involved in the case and mounted an energetic campaign to rehabilitate calas ’ memory and help the members of his family , who had been left destitute . he wrote letters to those in authority and published a stream of pamphlets , culminating in 1763 in his traité sur la tolérance , which begins with the historical facts of the calas case and broadens out into a history of religious intolerance in european culture . voltaire 's writings had enormous impact on public opinion , and eventually the judges in paris quashed the judgment of the toulouse court . too late to save calas , but a huge victory for voltaire , who had learnt an important lesson about how change could be brought about through the pressure of public opinion . voltaire said of himself that he ‘ wrote to act ’ , and he wanted his writings to change the way people thought and behaved . in leading his crusades against fanaticism , he even invented a campaign slogan , ecrasez l ’ infâme ! , which translates roughly as ‘ crush the despicable ! ’ . l ’ infâme stands here for everything that voltaire hates , everything that he had spent his life fighting : superstition , intolerance , irrational behaviour of every kind . we should never forget that voltaire was also a brilliant writer , one of the greatest stylist the french language has ever known . the power of his ideas had a lot to do with the power of his expression . many writers made fun of miracles . no one did so hilariously as voltaire . always , voltaire had an ear for the telling phrase : it 's a good line , even in english , and better still in the original french where it is more memorable because it is a classical alexandrine line in 12 syllables : si dieu n ’ existait pas , il faudrait l ’ inventer . voltaire 's legacy in our present debates about religious toleration remain extremely potent . hardly a week passes without an article in the press quoting : ‘ i disapprove of what you say , but i will defend to the death your right to say it. ’ this rallying cry of tolerant multiculturalism is so potent that if voltaire had n't said it , we would have had to invent it , which is what happened . the expression was invented by an english woman in 1906 . no matter , it expresses a truth which is fundamentally important to our culture , so we have adopted the phrase and decided that voltaire said it . voltaire , his name has become synonymous with a set of liberal values : freedom of speech , rejection of bigotry and superstition , belief in reason and tolerance . it 's a unique , and nowadays , extremely precious legacy .
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this was to be a subject dear to voltaire 's heart , for under the guise of writing a national epic , he was dwelling at length on the bloody consequences of religious intolerance . right from the start , voltaire 's views on religion were expressed robustly . he was not an atheist . in part , because he thought that some minimal belief in a deity was useful for social cohesion .
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true / false : voltaire was an atheist .
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there 's a quote usually attributed to the writer mark twain that goes , `` a lie can travel halfway around the world while the truth is putting on its shoes . '' funny thing about that . there 's reason to doubt that mark twain ever said this at all , thus , ironically , proving the point . and today , the quote , whoever said it , is truer than ever before . in previous decades , most media with global reach consisted of several major newspapers and networks which had the resources to gather information directly . outlets like reuters and the associated press that aggregate or rereport stories were relatively rare compared to today . the speed with which information spreads now has created the ideal conditions for a phenomenon known as circular reporting . this is when publication a publishes misinformation , publication b reprints it , and publication a then cites b as the source for the information . it 's also considered a form of circular reporting when multiple publications report on the same initial piece of false information , which then appears to another author as having been verified by multiple sources . for instance , the 1998 publication of a single pseudoscientific paper arguing that routine vaccination of children causes autism inspired an entire antivaccination movement , despite the fact that the original paper has repeatedly been discredited by the scientific community . deliberately unvaccinated children are now contracting contagious diseases that had been virtually eradicated in the united states , with some infections proving fatal . in a slightly less dire example , satirical articles that are formatted to resemble real ones can also be picked up by outlets not in on the joke . for example , a joke article in the reputable british medical journal entitled `` energy expenditure in adolescents playing new generation computer games , '' has been referenced in serious science publications over 400 times . user-generated content , such as wikis , are also a common contributer to circular reporting . as more writers come to rely on such pages for quick information , an unverified fact in a wiki page can make its way into a published article that may later be added as a citation for the very same wiki information , making it much harder to debunk . recent advances in communication technology have had immeasurable benefits in breaking down the barriers between information and people . but our desire for quick answers may overpower the desire to be certain of their validity . and when this bias can be multiplied by billions of people around the world , nearly instantaneously , more caution is in order . avoiding sensationalist media , searching for criticisms of suspicious information , and tracing the original source of a report can help slow down a lie , giving the truth more time to put on its shoes .
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there 's a quote usually attributed to the writer mark twain that goes , `` a lie can travel halfway around the world while the truth is putting on its shoes . '' funny thing about that .
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before the 20th century , because it took longer to publish writing , it was more accurate .
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studies have shown that taking vitamins is good for your health and bad for your health . that newly discovered herb can improve your memory or destroy your liver . headlines proclaim a promising new cancer treatment and never mention it again . on a daily basis , we are bombarded with attention-grabbing news , backed up by scientific studies , but what are these studies ? how are they performed ? and how do we know whether they 're reliable ? when it comes to dietary or medical information , the first thing to remember is that while studies on animals or individual cells can point the way towards further research , the only way to know how something will affect humans is through a study involving human subjects . and when it comes to human studies , the scientific gold standard is the randomized clinical trial , or rct . the key to rcts is that the subjects are randomly assigned to their study groups . they are often blinded to make them more rigorous . this process attempts to ensure that the only difference between the groups is the one the researchers are attempting to study . for example , when testing a new headache medication , a large pool of people with headaches would be randomly divided into two groups , one receiving the medication and another receiving a placebo . with proper randomization , the only significant overall difference between the two groups will be whether or not they received the medication , rather than other differences that could affect results . randomized clinical trials are incredible tools , and , in fact , the us food and drug administration often requires at least two to be conducted before a new drug can be marketed . but the problem is that an rct is not possible in many cases , either because it 's not practical or would require too many volunteers . in such cases , scientists use an epidemiological study , which simply observes people going about their usual behavior , rather than randomly assigning active participants to control invariable groups . let 's say we wanted to study whether an herbal ingredient on the market causes nausea . rather than deliberately giving people something that might make them nauseated , we would find those who already take the ingredient in their everyday lives . this group is called the cohort . we would also need a comparison group of people who do not have exposure to the ingredient . and we would then compare statistics . if the rate of nausea is higher in the herbal cohort , it suggests an association between the herbal supplement and nausea . epidemiological studies are great tools to study the health effects of almost anything , without directly interfering in people 's lives or assigning them to potentially dangerous exposures . so , why ca n't we rely on these studies to establish causal relationships between substances and their effects on health ? the problem is that even the best conducted epidemiological studies have inherent flaws . precisely because the test subjects are not randomly assigned to their groups . for example , if the cohort in our herbal study consisted of people who took the supplement for health reasons , they may have already had higher rates of nausea than the other people in the sample . or the cohort group could 've been composed of people who shop at health food stores and have different diets or better access to healthcare . these factors that can affect results , in addition to the factor being studied , are known as confounding variables . these two major pitfalls , combined with more general dangers , such as conflicts of interest or selective use of data , can make the findings of any particular epidemiological study suspect , and a good study must go out of its way to prove that its authors have taken steps to eliminate these types of errors . but even when this has been done , the very nature of epidemiological studies , which examine differences between preexisting groups , rather than deliberately inducing changes within the same individuals , means that a single study can only demonstrate a correlation between a substance and a health outcome , rather than a true cause and effect relationship . at the end of the day , epidemiological studies have served as excellent guides to public health , alerting us to critical health hazards , such as smoking , asbestos , lead , and many more . but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction . so , the next time you see a headline about a new miracle cure or the terrible danger posed by an everyday substance , try to learn more about the original study and the limitations inherent in any epidemiological study or clinical trial before jumping to conclusions .
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but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction . so , the next time you see a headline about a new miracle cure or the terrible danger posed by an everyday substance , try to learn more about the original study and the limitations inherent in any epidemiological study or clinical trial before jumping to conclusions .
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what can i look for the next time i read about a health study in the news ?
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if insects suddenly morphed into large beings , and decided to wage war on us , there 's no doubt that humans would lose . we 'd simply be crushed by their sheer numbers . there are an estimated 10 quintillion individual insects on earth . that 's a one followed by 19 zeroes . so , compared with our population of about 7 billion , these invertebrates outnumber us by more than a billion to one . their astounding numbers exist at the species level , as well . there are more than 60,000 vertebrate species on the planet . but the class of insects contains a million known species , and many others that have n't been classified . in fact , these critters make up approximately 75 % of all animals on earth . so , what 's their secret to success ? insect abundance comes down to many things that together make them some of the most adaptable and resilient creatures , beginning with their impressive ability to breed . many species can produce hundreds of offspring within their lifetimes . most offspring will die , but more than enough will survive into adulthood to reproduce . offspring also mature very rapidly , so the cycle of reproduction resumes quickly , and can occur over and over again in a short time . these numbers mean that as a class , insects harbor a tremendous amount of genetic diversity . the different species contain a wealth of genetic data that give them the necessary adaptations they need to thrive in a range of environments across the planet . even some of the most extreme environments are in bounds ; flat bark beetles can live at -40 degrees fahrenheit , sahara desert ants can venture out when surface temperatures exceed 155 degrees , and some bumblebees can survive 18,000 feet above sea level . insect exoskeletons also work like body armor , protecting insects against the outside world and helping them cope with habitats that other creatures ca n't . even their small size , which we might see as a disadvantage , is something they use to their benefit . because most species are so tiny , millions of insects can inhabit a small space and make use of all the available resources within it . this means they can occupy hundreds of different niches across ecosystems . some insects survive by eating the roots , stems , leaves , seeds , pollen , and nectar of specific plants . others , like wasps , make use of live insects by paralyzing the victims and laying their eggs inside so that when the hatchlings emerge , they can eat their way out and get nourishment . mosquitos and biting flies feed on blood , taking advantage of this unusual resource to ensure their survival . and a whole bunch of other insects have built a niche around feces . flies lay their eggs there , and some beetles even build large balls out of animal dung , which they eat and use as accommodation for their eggs . and then there 's the insects ' mighty power of metamorphosis . this trait not only transforms insects , but also helps them maximize the available resources in an ecosystem . take butterflies . in their larval caterpillar form , they chomp hungrily through leaves at a rapid rate to help them grow and spin cocoons . but when they emerge as butterflies , these insects feed only on flower nectar . metamorphosis means the larvae and adults of one species will never compete for the same resource , so they successfully share an ecological niche without limiting their own success . this process is so efficient that an incredible 86 % of insect species undergo complete metamorphosis . we 're big and they 're small , so it 's easy to forget that these critters are moving in their millions all around us , all the time . but examine almost any patch of ground , and you 're sure to find them there . their numbers are immense , and their success is unmatched . we may have to accept that it 's insects , not us , that are the true conquerors of the planet .
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metamorphosis means the larvae and adults of one species will never compete for the same resource , so they successfully share an ecological niche without limiting their own success . this process is so efficient that an incredible 86 % of insect species undergo complete metamorphosis . we 're big and they 're small , so it 's easy to forget that these critters are moving in their millions all around us , all the time .
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which of the following list the stages of complete metamorphosis in the correct order ?
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a boy named prince tamino runs through a dark wood pursued by a dragon . just as it rears up to devour him , three mysterious ladies appear and slay the dragon with their fierce battle cry . so begins wolfgang amadeus mozart 's `` die zauberflöte , '' or `` the magic flute . '' this fantasy singspiel , a type of folk opera with music and dialogue , premiered in 1791 in vienna . though it may seem like a childish fairytale , this intricate opera is full of subversive symbolism , and it 's now regarded as one of the most influential operas in history . tamino 's run in with the dragon is only the start of his journey . the three women summon their leader , the queen of the night . she , in turn , sends tamino on a quest to rescue her daughter pamina from the evil sorcerer , sarastro . and to help him on his journey , she gives him the titular magic flute . tamino eventually finds pamina at sarastro 's temple , but behind enemy lines , tamino and pamina learn that they 're on the wrong side . the queen of night actually wants to plunge the world into darkness . everything tamino thought he knew was wrong , filling him with doubt and confusion . so , a new quest begins for tamino and pamina . they must pass three trials of wisdom , and only then can the day vanquish the night . helped by the flute 's magic power , the two youths overcome these trials and the queen 's attempts to sabotage them . they 're finally initiated into the temple having restored balance to the kingdom . many elements in this peculiar fairytale were inspired by mozart 's involvement in freemasonry , a network of fraternal organizations throughout europe . much of their history , symbolism , and ritual came from the middle ages . but the freemasons of mozart 's time were also influenced by 18th century european ideals - rationalism , humanism , and skepticism towards traditional authorities , like monarchy and the church . the symbols of freemasonry and these ideals of the enlightenment are found throughout the opera . if this sounds like a conspiracy theory , that 's because it sort of was at the time , but it 's now taken quite seriously and has been the subject of considerable scholarly publication . for example , some mozart scholars believe the queen of the night symbolizes maria theresa , the empress of the holy roman empire who opposed freemasonry and banned it in austria . while there continues to be debate as to the specific meaning , interpretation , and location of these masonic references , scholars agree that they 're there and are fully intentional . one of these symbols is the number three , which represented balance and order to freemasons . now the number three is , of course , easy to find in any work of storytelling , but it 's particularly prominent in `` the magic flute '' : three trials , three ladies , three spirits , and three doors , much of the music is written in e-flat major , which has three flats in its key signature , and historically , masonic rituals began with three knocks . the opera references them by opening with three majestic chords complete with dramatic pauses . those chords , which reoccur throughout the opera , serve another purpose . they capture the dramatic arc of the opera in miniature . the first chord , e-flat major , is in its most natural root position , simple and unadorned . it echoes the child-like prince tamino , who , in his naiveté , accepts everything the queen and her ladies say without question . the second chord is c minor , a sour sonority that mirrors tamino 's sadness and doubt in the middle of the opera . that 's when his world and notions of good and evil get turned on their heads . and good and evil are just two of the opera 's extreme opposites . it features some of the highest and lowest notes in opera , day and night , simple hummable melodies and complicated forward-looking music . the opera 's central theme concerns balancing these extremes to achieve perfect harmony . to reflect this , the final chord in the opening restores musical order . it returns to the triumphant e-flat major , the same chord it started with but inverted , meaning mozart moved the bottom note to the top . although it retains its original harmony , the chord sounds higher , pointing towards enlightenment . that 's similar to tamino , who in passing his trials restores balance to the kingdom while growing stronger , wiser , and more complete .
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so begins wolfgang amadeus mozart 's `` die zauberflöte , '' or `` the magic flute . '' this fantasy singspiel , a type of folk opera with music and dialogue , premiered in 1791 in vienna . though it may seem like a childish fairytale , this intricate opera is full of subversive symbolism , and it 's now regarded as one of the most influential operas in history .
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what is a singspiel ?
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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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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 .
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alfred nobel mentioned three criteria for the nobel peace prize : disarmament , peace congresses , and brotherhood between nations . why are these relevant for peace work ?
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`` order , order . so who do we have here ? '' `` your honor , this is cleopatra , the egyptian queen whose lurid affairs destroyed two of rome 's finest generals and brought the end of the republic . '' `` your honor , this is cleopatra , one of the most powerful women in history whose reign brought egypt nearly 22 years of stability and prosperity . '' `` uh , why do n't we even know what she looked like ? '' `` most of the art and descriptions came long after her lifetime in the first century bce , just like most of the things written about her . '' `` so what do we actually know ? cleopatra vii was the last of the ptolemaic dynasty , a macedonian greek family that governed egypt after its conquest by alexander the great . she ruled jointly in alexandria with her brother- to whom she was also married- until he had her exiled . '' `` but what does all this have to do with rome ? '' `` egypt had long been a roman client state , and cleopatra 's father incurred large debts to the republic . after being defeated by julius caesar in rome 's civil war , the general pompey sought refuge in egypt but was executed by cleopatra 's brother instead . '' `` caesar must have liked that . '' `` actually , he found the murder unseemly and demanded repayment of egypt 's debt . he could have annexed egypt , but cleopatra convinced him to restore her to the throne instead . '' `` we hear she was quite convincing . '' `` and why not ? cleopatra was a fascinating woman . she commanded armies at 21 , spoke several languages , and was educated in a city with the world 's finest library and some of the greatest scholars of the time . '' `` hmm . '' `` she kept caesar lounging in egypt for months when rome needed him . '' `` caesar did more than lounge . he was fascinated by egypt 's culture and knowledge , and he learned much during his time there . when he returned to rome , he reformed the calendar , commissioned a census , made plans for a public library , and proposed many new infrastructure projects . '' `` yes , all very ambitious , exactly what got him assassinated . '' `` do n't blame the queen for rome 's strange politics . her job was ruling egypt , and she did it well . she stabilized the economy , managed the vast bureaucracy , and curbed corruption by priests and officials . when drought hit , she opened the granaries to the public and passed a tax amnesty , all while preserving her kingdom 's stability and independence with no revolts during the rest of her reign . '' `` so what went wrong ? '' `` after caesar 's death , this foreign queen could n't stop meddling in roman matters . '' `` actually , it was the roman factions who came demanding her aid . and of course she had no choice but to support octavian and marc antony in avenging caesar , if only for the sake of their son . '' `` and again , she provided her particular kind of support to marc antony . '' `` why does that matter ? why does n't anyone seem to care about caesar or antony 's countless other affairs ? why do we assume she instigated the relationships ? and why are only powerful women defined by their sexuality ? '' `` order . '' `` cleopatra and antony were a disaster . they offended the republic with their ridiculous celebrations sitting on golden thrones and dressing up as gods until octavian had all of rome convinced of their megalomania . '' `` and yet octavian was the one who attacked antony , annexed egypt , and declared himself emperor . it was the roman 's fear of a woman in power that ended their republic , not the woman herself . '' `` how ironic . '' cleopatra 's story survived mainly in the accounts of her enemies in rome , and later writers filled the gaps with rumors and stereotypes . we may never know the full truth of her life and her reign , but we can separate fact from rumor by putting history on trial .
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`` so what do we actually know ? cleopatra vii was the last of the ptolemaic dynasty , a macedonian greek family that governed egypt after its conquest by alexander the great . she ruled jointly in alexandria with her brother- to whom she was also married- until he had her exiled . ''
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what was pompey ’ s connection to egypt and cleopatra ’ s family ?
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are you familiar with the word symbiosis ? it 's a fancy term for a partnership between two different species , such as bees and flowers . in a symbiosis , both species depend on each other . i want to tell you about a remarkable symbiosis between a little bird , the clark 's nutcracker , and a big tree , the whitebark pine . whitebark grow in the mountains of wyoming , montana and other western states . they have huge canopies and lots of needles , which provide cover and shelter for other plants and animals , and whitebark feed the forest . their cones are packed with protein . squirrels gnaw the cones from the upper branches so they fall to the ground , and then race down to bury them in piles , or middens . but they do n't get to keep all of them ; grizzlies and black bears love finding middens . but there 's more to a symbiosis than one species feeding another . in the case of the clark 's nutcracker , this bird gives back . while gathering its seeds , it also replants the trees . here 's how it works : using her powerful beak , the nutcracker picks apart a cone in a treetop , pulling out the seeds . she can store up to 80 of them in a pouch in her throat . then she flies through the forest looking for a place to cache the seeds an inch under the soil in piles of up to eight seeds . nutcrackers can gather up to 90,000 seeds in the autumn , which they return for in the winter and spring . and these birds are smart . they remember where all those seeds are . they even use landmarks on the landscape -- trees , stumps , rocks -- to triangulate to caches buried deep under the snow . what they do n't go back and get , those seeds become whitebark . this symbiosis is so important to both species that they 've changed , or evolved , to suit each other . nutcrackers have developed long , tough beaks for extracting seeds from cones , and whitebarks ' branches all sweep upwards with the cones at the very ends , so they can offer them to the nutcrackers as they fly by . that 's a symbiosis : two species cooperating to help each other for the benefit of all .
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are you familiar with the word symbiosis ? it 's a fancy term for a partnership between two different species , such as bees and flowers . in a symbiosis , both species depend on each other . i want to tell you about a remarkable symbiosis between a little bird , the clark 's nutcracker , and a big tree , the whitebark pine .
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flowering plants have a symbiotic relationship with honey bees and bumble bees . what are other examples of symbiosis in nature ?
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about 66 million years ago , something terrible happened to life on our planet . ecosystems were hit with a double blow as massive volcanic eruptions filled the atmosphere with carbon dioxide and an asteroid roughly the size of manhattan struck the earth . the dust from the impact reduced or stopped photosynthesis from many plants , starving herbivores and the carnivores that preyed on them . within a short time span , three-quarters of the world 's species disappeared forever , and the giant dinosaurs , flying pterosaurs , shelled squids , and marine reptiles that had flourished for ages faded into prehistory . it may seem like the dinosaurs were especially unlucky , but extinctions of various severities have occurred throughout the earth 's history , and are still happening all around us today . environments change , pushing some species out of their comfort zones while creating new opportunities for others . invasive species arrive in new habitats , outcompeting the natives . and in some cases , entire species are wiped out as a result of activity by better adapted organisms . sometimes , however , massive changes in the environment occur too quickly for most living creatures to adapt , causing thousands of species to die off in a geological instant . we call this a mass extinction event , and although such events may be rare , paleontologists have been able to identify several of them through dramatic changes in the fossil record , where lineages that persisted through several geological layers suddenly disappear . in fact , these mass extinctions are used to divide the earth 's history into distinct periods . although the disappearance of the dinosaurs is the best known mass extinction event , the largest occurred long before dinosaurs ever existed . 252 million years ago , between the permian and triassic periods , the earth 's land masses gathered together into the single supercontinent pangaea . as it coalesced , its interior was filled with deserts , while the single coastline eliminated many of the shallow tropical seas where biodiversity thrived . huge volcanic eruptions occurred across siberia , coinciding with very high temperatures , suggesting a massive greenhouse effect . these catastrophes contributed to the extinction of 95 % of species in the ocean , and on land , the strange reptiles of the permian gave way to the ancestors of the far more familiar dinosaurs we know today . but mass extinctions are not just a thing of the distant past . over the last few million years , the fluctuation of massive ice sheets at our planet 's poles has caused sea levels to rise and fall , changing weather patterns and ocean currents along the way . as the ice sheets spread , retreated , and returned , some animals were either able to adapt to the changes , or migrate to a more suitable environment . others , however , such as giant ground sloths , giant hyenas , and mammoths went extinct . the extinction of these large mammals coincides with changes in the climate and ecosystem due to the melting ice caps . but there is also an uncomfortable overlap with the rise of a certain hominid species originating in africa 150,000 years ago . in the course of their adaptation to the new environment , creating new tools and methods for gathering food and hunting prey , humans may not have single-handedly caused the extinction of these large animals , as some were able to coexist with us for thousands of years . but it 's clear that today , our tools and methods have become so effective that humans are no longer reacting to the environment , but are actively changing it . the extinction of species is a normal occurrence in the background of ecosystems . but studies suggest that rates of extinction today for many organisms are hundreds to thousands of times higher than the normal background . but the same unique ability that makes humans capable of driving mass extinctions can also enable us to prevent them . by learning about past extinction events , recognizing what is happening today as environments change , and using this knowledge to lessen our effect on other species , we can transform humanity 's impact on the world from something as destructive as a massive asteroid into a collaborative part of a biologically diverse future .
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sometimes , however , massive changes in the environment occur too quickly for most living creatures to adapt , causing thousands of species to die off in a geological instant . we call this a mass extinction event , and although such events may be rare , paleontologists have been able to identify several of them through dramatic changes in the fossil record , where lineages that persisted through several geological layers suddenly disappear . in fact , these mass extinctions are used to divide the earth 's history into distinct periods . although the disappearance of the dinosaurs is the best known mass extinction event , the largest occurred long before dinosaurs ever existed . 252 million years ago , between the permian and triassic periods , the earth 's land masses gathered together into the single supercontinent pangaea . as it coalesced , its interior was filled with deserts , while the single coastline eliminated many of the shallow tropical seas where biodiversity thrived .
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the permian-triassic mass extinction paved the way for what group of animals to diversify ?
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two or three days ago , i got a letter from one of our fans and it ’ s different from any other letter that we have ever had , because this fan , young , has attached to it a sample of an element and what ’ s more it is an element that i had never seen . it ’ s scandium . it ’ s only a small piece but according to my colleague steve , it ’ s a very expensive element , so this might be quite valuable , and scandium is a really interesting element , much more interesting than i realised , when i first talked about it on the video . scandium is an element which chemists usually ignore , i have never used scandium in any of my research . it was one of the elements that mendeleev predicted ought to exist when he first devised the periodic table , when he made it there were lots of elements which were not known , but what he did was to predict that there were holes in various places where he felt that there ought to be an element and because obviously these elements did not have names , he called them ekea boron or ekea aluminium or ekea silicon meaning underneath those elements . and the triumph of the periodic table was that people actually discovered these elements . and the first one that was discovered was the element gallium ( ekea aluminium ) and the second one was ekea boron which is scandium . now you might think that it is a bit surprising because if you look at a modern periodic table , scandium and boron are really quite a long way apart but in the original way that medeleev started the periodic table when he wrote it down first , scandium and boron came very close together because both of them , have three electrons in their outer shell which makes their chemistry quite similar . of course medeleev did not know about electrons , but he guessed from looking at titanium which has four electrons and calcium which has two that he thought there was something missing and what is also interesting about these three elements that he predicted is that they all ended up with names of countries . there was gallium that was named after france , from the latin word for france . scandium that was named after , well perhaps not a country but a region , scandinavia , and then germanium , that was named after germany . the first time that an element was discovered , when gallium was discovered , people said well it was just luck , but when scandium was discovered , they really began to take mendeleev pretty seriously , and by the time germanium was discovered they really all decided that mendeleev was right . scandium , because it is an uncommon element , is one where people don ’ t know much about the chemistry . i have never really done any research in this area but like many elements suddenly there comes a time where they become really quite popular and topical and now is the time for scandium and the reason is that scandium is a really light metal . its density is slightly less than 4 , that ’ s 4 grams per cubic centimetre and that is very much lighter than most metals . copper is nearly 10 and lead and gold are close to 20 , so this is really very light . so why should metals be important if they are light , and that ’ s , the reason is sometimes you want to use a metal , but you don ’ t want the object you make to be very heavy and so for example titanium which is very light , is used for making everything from golf clubs to jet fighter planes , where you want it to be really light either so that you can swing it fast or fly fast . for scandium the reasons are rather different , people are now thinking about using hydrogen , to power cars , to use hydrogen gas , to use hydrogen gas as the fuel to power cars , but what they want to do is to store the hydrogen , in the equivalent of the petrol tank . you can ’ t just pressurise the hydrogen as in a gas cylinder because the container would be so heavy , that your car would be like a military tank it would be so heavy . so what they want to try and do is produce a chemical compound , which is a bit like a sponge that will absorb the hydrogen and then for example if you warm it gently they hydrogen will come out , and it is here that you want the metal to be light because you want this material that you are using to store hydrogen not to weigh very much . because you have got to cart it around in your car all the time , and scandium compounds are now looking really quite promising , for storage of hydrogen , and the idea is that rather like a molecular model kit , where you have balls joined with sticks , you can use organic compounds , those of carbon and hydrogen with a little oxygen , like sticks to join together scandium atoms , and produce a structure which has a lot of holes in it and then the hydrogen can go into those holes and be stored without needing an enormous pressure . sounds like an incredibly complicated way to make a fuel tank . it is quite complicated but on the other hand , if it works , you don ’ t need to understand the chemistry . you just add the hydrogen to your tank and away you go . how can you have got to your ripe old age as a chemist and never seen scandium ? well , chemists very often use compounds , salts of metals , but it ’ s not too often that you use the metal itself and salts because they don ’ t have to be purified and so on quite as much as the metals are easier to get , they are not as expensive and so there are lots of the elements which i haven ’ t seen , but i am really quite pleased with this sample of scandium , so when i am finished i am going to frame it and hang it on my wall . so we have one of my students who works with one of my colleagues , martin schroder and the student , has done his whole project , three year project , on the chemistry of scandium , so when i got this letter i asked him : have you ever seen scandium ? and he hadn ’ t , he had never seen the metal , so he was really quite excited to see john ’ s letter .
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it was one of the elements that mendeleev predicted ought to exist when he first devised the periodic table , when he made it there were lots of elements which were not known , but what he did was to predict that there were holes in various places where he felt that there ought to be an element and because obviously these elements did not have names , he called them ekea boron or ekea aluminium or ekea silicon meaning underneath those elements . and the triumph of the periodic table was that people actually discovered these elements . and the first one that was discovered was the element gallium ( ekea aluminium ) and the second one was ekea boron which is scandium . now you might think that it is a bit surprising because if you look at a modern periodic table , scandium and boron are really quite a long way apart but in the original way that medeleev started the periodic table when he wrote it down first , scandium and boron came very close together because both of them , have three electrons in their outer shell which makes their chemistry quite similar . of course medeleev did not know about electrons , but he guessed from looking at titanium which has four electrons and calcium which has two that he thought there was something missing and what is also interesting about these three elements that he predicted is that they all ended up with names of countries .
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in his first periodic table ( 1869 ) , dmitri mendeleev predicted the existence of the element scandium and two others . what was the first , temporary name that the father of the periodic table gave to this element ?
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sometimes when a fish is reeled up to the surface it will appear inflated , with its eyes bulging out of their sockets and its stomach projecting out of its mouth , as if its been blown up like a balloon . this type of bodily damage , caused by rapid changes in pressure , is called barotrauma . under the sea , pressure increases by 14.7 pounds per square inch for every 33 foot increase in depth . so , take the yelloweye rockfish , which can live as deep as 1800 feet , where there 's over 800 pounds of pressure on every square inch . that 's equivalent to the weight of a polar bear balancing on a quarter . now , boyle 's gas law states that the volume of a gas is inversely related to pressure . so , any air-filled spaces , like a rockfish 's swim bladder , or human lungs , will compress as they descend deeper and expand as they ascend . after a fish bites a fisherman 's hook and is quickly reeled up to the surface , the air in its swim bladder begins to expand . its rapid expansion actually forces the fish 's stomach out of its mouth , while the increased internal pressure pushes its eyes out of their sockets , a condition called exophthalmia . sometimes rockfish eyes will even have a crystallized appearance from corneal emphysemas , little gas bubbles that build up inside the cornea . thankfully , a scuba diver does n't have a closed swim bladder to worry about . a diver can regulate pressure in her lungs by breathing out as she ascends , but must be wary of other laws of physics that are at play under the sea . henry 's law states that the amount of a gas that dissolves in a liquid is proportional to its partial pressure . the air a diver breathes is 78 % nitrogen . at a higher pressure under the sea , the nitrogen from the air in a scuba tank diffuses into a diver 's tissues in greater concentrations than it would on land . if the diver ascends too quickly , this built up nitrogen can come out of solution and form microbubbles in her tissues , blood and joints , causing decompression sickness , aka the bends . this is similar to the fizz of carbon dioxide coming out of your soda . gas comes out of solution when the pressure 's released . but for a diver , the bubbles cause severe pain and sometimes even death . divers avoid falling victim to the bends by rising slowly and taking breaks along the way , called decompression stops , so the gas has time to diffuse back out of their tissues and to be released through their breath . just as a diver needs decompression , for a fish to recover , it needs recompression , which can be accomplished by putting it back in the sea . but that does n't mean that fish should just be tossed overboard . an inflated body will float and get scooped up by a hungry sea lion or pecked at by seagulls . there 's a common myth that piercing its stomach with a needle will let air escape , allowing the fish to swim back down on its own . but that is one balloon that should n't be popped . to return a fish properly to its habitat , fisherman can use a descending device instead to lower it on a fishing line and release it at the right depth . as it heads home and recompression reduces gas volume , its eyes can return to their sockets and heal , and its stomach can move back into place . this fish will live to see another day , once more free to swim , eat , reproduce and replenish the population .
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now , boyle 's gas law states that the volume of a gas is inversely related to pressure . so , any air-filled spaces , like a rockfish 's swim bladder , or human lungs , will compress as they descend deeper and expand as they ascend . after a fish bites a fisherman 's hook and is quickly reeled up to the surface , the air in its swim bladder begins to expand . its rapid expansion actually forces the fish 's stomach out of its mouth , while the increased internal pressure pushes its eyes out of their sockets , a condition called exophthalmia . sometimes rockfish eyes will even have a crystallized appearance from corneal emphysemas , little gas bubbles that build up inside the cornea .
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what is the name of the air-filled organ that has the most potential to cause bodily harm due to rapid expansion when a rockfish is reeled to the surface ?
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right now , you 're probably sitting down to watch this video and staying seated for a few minutes to view it is probably okay . but the longer you stay put , the more agitated your body becomes . it sits there counting down the moments until you stand up again and take it for a walk . that may sound ridiculous . our bodies love to sit , right ? not really . sure , sitting for brief periods can help us recover from stress or recuperate from exercise . but nowadays , our lifestyles make us sit much more than we move around , and our bodies simply are n't built for such a sedentary existence . in fact , just the opposite is true . the human body is built to move , and you can see evidence of that in the way it 's structured . inside us are over 360 joints , and about 700 skeletal muscles that enable easy , fluid motion . the body 's unique physical structure gives us the ability to stand up straight against the pull of gravity . our blood depends on us moving around to be able to circulate properly . our nerve cells benefit from movement , and our skin is elastic , meaning it molds to our motions . so if every inch of the body is ready and waiting for you to move , what happens when you just do n't ? let 's start with the backbone of the problem , literally . your spine is a long structure made of bones and the cartilage discs that sit between them . joints , muscles and ligaments that are attached to the bones hold it all together . a common way of sitting is with a curved back and slumped shoulders , a position that puts uneven pressure on your spine . over time , this causes wear and tear in your spinal discs , overworks certain ligaments and joints , and puts strain on muscles that stretch to accommodate your back 's curved position . this hunched shape also shrinks your chest cavity while you sit , meaning your lungs have less space to expand into when you breath . that 's a problem because it temporarily limits the amount of oxygen that fills your lungs and filters into your blood . around the skeleton are the muscles , nerves , arteries and veins that form the body 's soft tissue layers . the very act of sitting squashes , pressurizes and compresses , and these more delicate tissues really feel the brunt . have you ever experienced numbness and swelling in your limbs when you sit ? in areas that are the most compressed , your nerves , arteries and veins can become blocked , which limits nerve signaling , causing the numbness , and reduces blood flow in your limbs , causing them to swell . sitting for long periods also temporarily deactivates lipoprotein lipase , a special enzyme in the walls of blood capillaries that breaks down fats in the blood , so when you sit , you 're not burning fat nearly as well as when you move around . what effect does all of this stasis have on the brain ? most of the time , you probably sit down to use your brain , but ironically , lengthy periods of sitting actually run counter to this goal . being stationary reduces blood flow and the amount of oxygen entering your blood stream through your lungs . your brain requires both of those things to remain alert , so your concentration levels will most likely dip as your brain activity slows . unfortunately , the ill effects of being seated do n't only exist in the short term . recent studies have found that sitting for long periods is linked with some types of cancers and heart disease and can contribute to diabetes , kidney and liver problems . in fact , researchers have worked out that , worldwide , inactivity causes about 9 % of premature deaths a year . that 's over 5 million people . so what seems like such a harmless habit actually has the power to change our health . but luckily , the solutions to this mounting threat are simple and intuitive . when you have no choice but to sit , try switching the slouch for a straighter spine , and when you do n't have to be bound to your seat , aim to move around much more , perhaps by setting a reminder to yourself to get up every half hour . but mostly , just appreciate that bodies are built for motion , not for stillness . in fact , since the video 's almost over , why not stand up and stretch right now ? treat your body to a walk . it 'll thank you later .
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sitting for long periods also temporarily deactivates lipoprotein lipase , a special enzyme in the walls of blood capillaries that breaks down fats in the blood , so when you sit , you 're not burning fat nearly as well as when you move around . what effect does all of this stasis have on the brain ? most of the time , you probably sit down to use your brain , but ironically , lengthy periods of sitting actually run counter to this goal .
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you are studying for a final exam and have been sitting all day . what effect could this have on your ability to learn ?
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scientific breakthrough , the kind that can potentially save lives , can sometimes be lying right out in the open for us to discover , in the evolved , accumulated body of human anecdote , for example , or in the time-tested adaptations that we observe in the natural world around us . science starts with observation , but the trick is to identify the patterns and signatures that we might otherwise dismiss as myth or coincidence , isolate them , and test them with scientific rigor . and when we do , the results will often surprise . western australia has had a particular problem with shark attacks over the last three years , unfortunately and tragically culminating in five fatal shark attacks in a 10-month period during that time . but western australia is not alone in this . the incident of shark engagements on humans is escalating worldwide . and so it 's not surprising , perhaps , that in july of this year , shark attack mitigation systems in collaboration with the university of western australia oceans institute made an announcement which captured the attention of the worldwide media and of ocean users worldwide , and that was around the development of technology to mitigate or reduce the risk of shark attack based on the science of what sharks can see . and i have for you today the story of that journey , but also the notion that science can be as powerful as a translator as it can be for invention . when we began this process , we were looking , it was about three years ago , and we 'd just had the first two fatal shark attacks in western australia , and by chance , in a previous role , i happened to be having dinner with harry butler . now harry butler , who most australians would know is a famous naturalist , had spent a lot of time in the marine environment . harry butler is a precursor , if you like , to the late steve irwin . when i asked him about what the solution to the problem might be , the answer was quite surprising . he said , `` take a black wetsuit , band it in yellow stripes like a bumblebee , and you 'll be mimicking the warning systems of most marine species . '' i did n't think about that much at the time , and it was n't until the next three fatal shark attacks happened , and it caused me to think , maybe there 's some merit to this idea . and i turned to the web to see if there might be some clues . and it turns out the web is awash with this sort of evidence that supports this sort of thinking . so biologically , there are plenty of species that display banding or patterns , warning patterns , to either be cryptical in the water or warn against being attacked , not the least of which is the pilot fish which spends a big slab of its life around the business end of a shark . on the human side , walter starck , an oceanographer , has been painting his wetsuit since the 1970s , and anthropologically , pacific island tribes painted themselves in bands in a sea snake ceremony to ward off the shark god . so what 's going on here ? is this an idea lying wide out in the open for us to consider and define ? we know that sharks use a range of sensors when they engage , particularly for attack , but the sight sensor is the one that they use to identify the target , and particularly in the last number of meters before the attack . it makes sense to pay attention to the biological anecdote because that 's time-tested evolution over many millennia . but is n't human anecdote also an evolution of sorts , the idea that there 's a kernel of truth thought to be important , passed down from generation to generation , so that it actually ends up shaping human behavior ? i wanted to test this idea . i wanted to put some science to this anecdotal evidence , because if science could support this concept , then we might have at least part of the solution to shark attack right under our very nose . to do that , i needed some experts in shark vision and shark neurology , and a worldwide search , again , led to the university of w.a . on the doorstep here , with the oceans institute . and professor nathan hart and his team had just written a paper which tells us , confirms that predatory sharks see in black and white , or grayscale . so i called up nathan , a little bit sheepishly , actually , about this idea that maybe we could use these patterns and shapes to produce a wetsuit to try and mitigate the risk of shark attack , and fortunately , he thought that was a good idea . so what ensued is a collaborative bit of research supported by the west australian state government . and we did three key things . the first is that we mapped the characteristics , the physical characteristics of the eyes of the three main predatory sharks , so the great white , tiger and bull shark . we did that genetically and we did that anatomically . the next thing we did was to understand , using complex computer modeling , what that eye can see at different depths , distances , light conditions , and water clarity in the ocean . and from there , we were able to pinpoint two key characteristics : what patterns and shapes would present the wearer as hidden or hard to make out in the water , cryptic , and what patterns and shapes might provide the greatest contrast but provide the greatest breakup of profile so that that person was n't confused for shark prey or shark food . the next thing we needed to do was to convert this into wetsuits that people might actually wear , and to that end , i invited ray smith , a surfer , industrial designer , wetsuit designer , and in fact the guy that designed the original quiksilver logo , to come over and sit with the science team and interpret that science into aesthetic wetsuits that people might actually wear . and here 's an example of one of the first drawings . so this is what i call a `` do n't eat me '' wetsuit . so this takes that banding idea , takes that banding idea , it 's highly visible , provides a highly disruptive profile , and is intended to prevent the shark from considering that you would be ordinary food , and potentially even create confusion for the shark . and this one 's configured to go with a surfboard . you can see that dark , opaque panel on the front , and it 's particularly better for the surface , where being backlit and providing a silhouette is problematic . second iteration is the cryptic wetsuit , or the one which attempts to hide the wearer in the water column . there are three panels on this suit , and in any given conditions , one or more of those panels will match the reflective spectra of the water so as to disappear fully or partially , leaving the last panel or panels to create a disruptive profile in the water column . and this one 's particularly well-suited to the dive configuration , so when you 're deeper under the water . so we knew that we had some really solid science here . we knew , if you wanted to stand out , you needed to look stripy , and we knew if you wanted to be cryptic , you needed to look like this . but the acid test is always going to be , how would sharks really behave in the context of these patterns and shapes . and testing to simulate a person in a wetsuit in the water with a predatory shark in a natural environment is actually a lot harder than you might think . ( laughter ) so we have to bait the rig , because we need to get the statistical number of samples through to get the scientific evidence , and by baiting the rig , we 're obviously changing shark behavior . we ca n't put humans in the water . we 're ethically precluded from even using humanoid shapes and baiting them up in the water . but nevertheless , we started the testing process in january of this year , initially with tiger sharks and subsequently with great white sharks . the way we did that was to get a perforated drum which is full of bait , wrap it in a neoprene skin , and then run two stereo underwater cameras to watch how the shark actually engages with that rig . and because we use stereo , we can capture all the statistics on how big the shark is , what angle it comes in at , how quickly it leaves , and what its behavior is in an empirical rather than a subjective way . because we needed to preserve the scientific method , we ran a control rig which was a black neoprene rig just like a normal black wetsuit against the , what we call , sams technology rig . and the results were not just exciting , but very encouraging , and today i would like to just give you a snapshot of two of those engagements . so here we 've got a four-meter tiger shark engaging the black control rig , which it had encountered about a minute and a half before . now that exact same shark had engaged , or encountered this sams rig , which is the elude sams rig , about eight minutes before , and spent six minutes circling it , hunting for it , looking for what it could smell and sense but not see , and this was the final engagement . great white sharks are more confident than the tigers , and here you see great white shark engaging a control rig , so a black neoprene wetsuit , and going straight to the bottom , coming up and engaging . in contrast to the sams technology rig , this is the banded one , where it 's more tactile , it 's more investigative , it 's more apprehensive , and shows a reluctance to come straight in and go . ( applause ) so , it 's important for us that all the testing is done independently , and the university of w.a . is doing the testing . it 'll be an ongoing process . it 's subject to peer review and subject to publication . it 's so important that this concept is led with the science . from the perspective of shark attack mitigation systems , we 're a biotechnology licensing company , so we do n't make wetsuits ourselves . we 'll license others to do that . but i thought you might be interested in seeing what sams technology looks like embedded in a wetsuit , and to that end , for the first time , live , worldwide -- ( laughter ) — i can show you what biological adaptation , science and design looks like in real life . so i can welcome sam , the surfer , from this side . where are you , sam ? ( applause ) and eduardo . ( applause ) cheers , mate . cheers . thanks , gentlemen . ( applause ) so what have we done here ? well , to my mind , rather than take a blank sheet and use science as a tool for invention , we 've paid attention to the biological evidence , we 've put importance to the human anecdotal evidence , and we 've used science as a tool for translation , translation of something that was already there into something that we can use for the benefit of mankind . and it strikes me that this idea of science as a tool for translation rather than invention is one that we can apply much more widely than this in the pursuit of innovation . after all , did the wright brothers discover manned flight , or did they observe the biological fact of flight and translate that mechanically , replicate it in a way that humans could use ? as for the humble wetsuit , who knows what oceanwear will look like in two years ' time , in five years ' time or in 50 years ' time , but with this new thinking , i 'm guessing there 's a fair chance it wo n't be pure black . thank you . ( applause )
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and i have for you today the story of that journey , but also the notion that science can be as powerful as a translator as it can be for invention . when we began this process , we were looking , it was about three years ago , and we 'd just had the first two fatal shark attacks in western australia , and by chance , in a previous role , i happened to be having dinner with harry butler . now harry butler , who most australians would know is a famous naturalist , had spent a lot of time in the marine environment . harry butler is a precursor , if you like , to the late steve irwin . when i asked him about what the solution to the problem might be , the answer was quite surprising .
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why does harry butler believe attacks are increasing ?
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humans have observed comets for thousands of years as their orbits have brought them within visible distance of earth . appearing throughout historical records , these mysterious lights that came out of nowhere and disappeared after a short while were thought to be ill omens of war and famine , or the wrath of gods . but recent research has revealed that comets may be even more deeply connected to humanity and our presence on earth than any of these mythical explanations suggested . when you think of our solar system , you probably imagine the nine , sorry eight , planets orbiting the sun . but beyond neptune , far from the heat of the sun , there is a sparse ring found formed by icy chunks ranging from the size of marbles to that of small planets . and thousands of times farther at the outer reaches of the solar system lies a spherical cloud of small fragments and gases . many of these ancient clumps of stardust are leftovers from the formation of the solar system 4.6 billion years ago , while some of the most distant may even come from a neighboring system . but sometimes the gravity from passing planets or stars pulls them toward our sun , beginning a journey that can take up to millions of years . as the frozen object travels further into the solar system , the sun grows from a distant spark to an inferno , melting the ice for the first time in billions of years . gas and steam eject dust into space , forming a bright surrounding cloud , called a coma , that can grow even larger than the sun itself . meanwhile , the intense stream of high-energy particles constantly emitted by the sun , known as the solar wind , blows particles away from the comet 's core , forming a trail of debris up to millions of miles long . the ice , gas and dust reflect light glowing brightly . a comet is born , now orbiting the sun along with the rest of the objects in our solar system . but as the comet travels through the solar system , the solar wind tears apart and recombines molecules into various compounds . in some of the compounds that scientists found , first in the rubble left by a meteorite that disintegrated above northern canada , and then in samples collected by a space craft from a passing comet 's tail , were nothing less important than amino acids . coming together to form proteins according to the instructs encoded in dna , these are the main active components in all living cells , from bacteria to blue whales . if comets are where these building blocks of life were first formed , then they are the ultimate source of life on earth , and , perhaps , some of the other places they visited as well . we know that planets orbit nearly every star in the night sky , with one in five having a planet similar to earth in size and temperature . if earth-like planets and the molecules found in dna are not anomalies , we may be only one example of what 's possible when a planet under the right conditions is seeded with organic molecules by a passing comet . so , rather than an omen of death , the comet that first brought amino acids to earth could have been a portent of life , a prediction of a distant future , where creatures of stardust would return to space to find the mysteries of where they came from .
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as the frozen object travels further into the solar system , the sun grows from a distant spark to an inferno , melting the ice for the first time in billions of years . gas and steam eject dust into space , forming a bright surrounding cloud , called a coma , that can grow even larger than the sun itself . meanwhile , the intense stream of high-energy particles constantly emitted by the sun , known as the solar wind , blows particles away from the comet 's core , forming a trail of debris up to millions of miles long .
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the cloud of dust and gas surrounding a comet 's rocky core is called a _____ .
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