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are you sleeping restlessly , feeling irritable or moody , forgetting little things , and feeling overwhelmed and isolated ? do n't worry . we 've all been there . you 're probably just stressed out . stress is n't always a bad thing . it can be handy for a burst of extra energy and focus , like when you 're playing a competitive sport , or have to speak in public . but when its continuous , the kind most of us face day in and day out , it actually begins to change your brain . chronic stress , like being overworked or having arguments at home , can affect brain size , its structure , and how it functions , right down to the level of your genes . stress begins with something called the hypothalamus pituitary adrenal axis , a series of interactions between endocrine glands in the brain and on the kidney , which controls your body 's reaction to stress . when your brain detects a stressful situation , your hpa axis is instantly activated and releases a hormone called cortisol , which primes your body for instant action . but high levels of cortisol over long periods of time wreak havoc on your brain . for example , chronic stress increases the activity level and number of neural connections in the amygdala , your brain 's fear center . and as levels of cortisol rise , electric signals in your hippocampus , the part of the brain associated with learning , memories , and stress control , deteriorate . the hippocampus also inhibits the activity of the hpa axis , so when it weakens , so does your ability to control your stress . that 's not all , though . cortisol can literally cause your brain to shrink in size . too much of it results in the loss of synaptic connections between neurons and the shrinking of your prefrontal cortex , the part of your brain the regulates behaviors like concentration , decision-making , judgement , and social interaction . it also leads to fewer new brain cells being made in the hippocampus . this means chronic stress might make it harder for you to learn and remember things , and also set the stage for more serious mental problems , like depression and eventually alzheimer 's disease . the effects of stress may filter right down to your brain 's dna . an experiment showed that the amount of nurturing a mother rat provides its newborn baby plays a part in determining how that baby responds to stress later in life . the pups of nurturing moms turned out less sensitive to stress because their brains developed more cortisol receptors , which stick to cortisol and dampen the stress response . the pups of negligent moms had the opposite outcome , and so became more sensitive to stress throughout life . these are considered epigenetic changes , meaning that they effect which genes are expressed without directly changing the genetic code . and these changes can be reversed if the moms are swapped . but there 's a surprising result . the epigenetic changes caused by one single mother rat were passed down to many generations of rats after her . in other words , the results of these actions were inheritable . it 's not all bad news , though . there are many ways to reverse what cortisol does to your stressed brain . the most powerful weapons are exercise and meditation , which involves breathing deeply and being aware and focused on your surroundings . both of these activities decrease your stress and increase the size of the hippocampus , thereby improving your memory . so do n't feel defeated by the pressures of daily life . get in control of your stress before it takes control of you .
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but there 's a surprising result . the epigenetic changes caused by one single mother rat were passed down to many generations of rats after her . in other words , the results of these actions were inheritable .
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what are epigenetic changes ?
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translator : andrea mcdonough reviewer : bedirhan cinar about 100 days ago , we landed a two-ton suv on the surface of another planet , on the surface of mars . this is one of the first pictures we took there with our rover , looking out at mount sharp . i kind of cry a little bit , choke up , when i see this picture . why mars and why do we look at these other planets ? part of it is to understand our own planet -- what 's the context for us ? we live on this amazing planet , but mars is a lot like earth . it 's similar in size . during the daytime , it can get up to 70 degrees fahrenheit . so , it 's so like earth , but at the same time , this is a barren landscape . you do n't see any trees , you do n't see any cactuses growing , anything like that . today i 'm going to tell you about how we got from earth to mars and why it 's so cool . so one of the things we start with is a blank sheet of paper . we knew from the previous missions in 2004 , spirit and opportunity , there was water on mars in the past . but what 's the next step ? we 're looking for an even more fundamental level of , what does it take to have life survive ? and so , to have that kind of knowledge and understanding , we have to carry a mass amount of instruments . we have to carry the kind of labs that people have whole rooms devoted to on earth inside of , essentially , a small car . and we shrunk it all down to something that weighs about as much as i do , and then put it inside of this rover that weighs as much as your car does . and that rover is now on the surface of mars , but it 's so heavy , and so it kind of takes a special challenge for us to make it all work and come together . so we look at our tool of , what do we have to land stuff on mars ? and one of the options is airbags . we 've done it before . airbags are pretty cool , they bounce around a lot . you could never put a human inside of an airbag , because they would get squashed . but the problem with airbags is , the airbags you see here , which landed the smaller rover -- it 's like 400 pounds , the entire rover -- were about the size of this room . so you can imagine the size of airbags it would take to land a two-ton rover on mars . and they 'd have to be made out of materials that do n't even exist today , so it 'd be some kind of exotic material that we 'd have to develop and it may or may not work . so , what about rockets ? you know , you see all the rocket ships landing in old movies , all rockets on the bottom -- it 's a cool idea . it works when they 're pretty light still , but the problem is , these rockets have to be pretty strong to actually softly land you on mars . and so they would be so powerful they could dig holes into the ground and then you would just end up inside of a hole and not be able to drive out of it . so , not the best design . but what if i could take the rockets and move them up ? and that 's what we came up with . it 's a rocket-powered jet pack ; we call it the sky crane . basically , this big rocket sits on top of our rover and when we 're ready to land , the rocket hovers in place and we slowly lower the rover to the ground . and then we touch down , we 're actually on the wheels , we 're ready to drive , day one . but in addition to that , the scientists were like , `` we actually want to go somewhere interesting . '' the last two missions were cool , but they basically landed in what was like landing in the plains or desert . not very exciting . we all know from the exciting places on earth like the grand canyon , those are , for the scientists , the most interesting , because you see that whole layer , you see years and years of history all in one place . the same thing is true for where we landed . we wanted to land somewhere that was unique , that had this crater wall where things had been dug up for us , where mountains were pushing things up . but the problem is , if you landed with the older systems , you could 've landed on the side of that mountain and just tumbled off , could 've been the side of a cliff , the crater wall or a large boulder . so we needed a kind of technology to help us land in a very small area , and that was this little guided entry from apollo . we took it from the 1960s . we flew over like the manned vehicle , because they have to pick up men , you ca n't just land all over the place . and then we landed , like , spot-on in the middle . and in fact , it was so spot-on that when we did it , it was basically like a quarterback launching towards mars -- like a quarterback , though , that was in seattle , throwing at a receiver that was moving here in giants stadium . that 's how accurate we were . kind of awesome . but you only get one shot , and so we actually have to design a system that we can build and test and operate , and so it 's not just about can we get it to mars , but , if it 's only one chance , how do you make sure that one chance goes well ? so there 's all these processes to make sure things are built properly . then we go out to the desert and drive around and test it . we fly things in f-18s to make sure the radar systems work in high speeds . then , most importantly , we test the team to make sure they know how to operate it . we do n't want to miss it because we sent the wrong command and now it 's going to be rebooting forever . so , that guy fred there , he did a lot of that . and then we launched it on this rocket to mars . we landed 2,000 pounds on mars , but the entire thing was about 10,000 pounds when we lifted off from earth , all the fuel and the solar arrays and everything else that we needed . and , again , we were so accurate that we landed in this , like , little pin-point on mars . in the meantime , though , we had to design a landing system that worked . and i told you about the actual physics of it , but here 's the catch : mars is about 14 minutes away from earth in light speed , which means if i try to control it with a joystick , i would be always controlling to 14 minutes in advance , so it would n't work . so we had to give it all the smarts and knowledge it needed to make it happen . so we built in all these smarts and algorithms and told it here 's what you 're going to have to do , and it goes from basically five times the speed of a speeding bullet to about a baby 's crawl , all within about seven minutes , which are called the seven minutes of terror , because i was about to throw up . ( laughter ) but today we 're on the surface of mars , and this was one of the panoramas we took a couple days after we landed , and it 's amazing to me , because you look at this , and can see the grand canyon , you can see your own planet , you can imagine walking on the surface . and so what we 're going to do and continue to do is to understand what makes mars so special and what makes earth even more special that we 're all here together today . so we 'll see where curiosity takes us -- not just our rover , but our sense of exploration . thank you . ( applause )
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and , again , we were so accurate that we landed in this , like , little pin-point on mars . in the meantime , though , we had to design a landing system that worked . and i told you about the actual physics of it , but here 's the catch : mars is about 14 minutes away from earth in light speed , which means if i try to control it with a joystick , i would be always controlling to 14 minutes in advance , so it would n't work .
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ferdowsi likens the landing of curiosity to
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we 've all seen movies about terrible insects from outer space or stories of abduction by little green men , but the study of life in the universe , including the possibility of extraterrestrial life , is also a serious , scientific pursuit . astrobiology draws on diverse fields , such as physics , biology , astronomy , and geology , to study how life was formed on earth , how it could form elsewhere , and how we might detect it . many ancient religions described other worlds inhabited by known human beings , but these are more like mythical realms or parallel universes than other planets existing in the same physical world . it is only within the last century that scientists have been able to seriously undertake the search for extraterrestrial life . we know that at the most basic level organisms on earth need three things : liquid water , a source of energy , and organic , carbon-based material . we also know that the earth is just the right distance from the sun , so as not to be either frozen or molten . so , planets within such a habitable range from their own stars may be able to support life . but while we used to think that life could only exist in such earth-like environments , one of the most amazing discoveries of astrobiology has been just how versatile life is . we now know that life can thrive in some of the most extreme environments that 'd be fatal for most known organisms . life is found everywhere , from black smoke of hydrothermal vents in the dark depths of earth 's oceans , to bubbling , hot , acidic springs on the flanks of volcanoes , to high up in the atmosphere . organisms that live in these challenging environments are called extremophiles , and they can survive at extremes of temperature , pressure , and radiation , as well as salinity , acidity , and limited availability of sunlight , water , or oxygen . what is most remarkable about these extremophiles is that they are found thriving in environments that mimic those on alien worlds . one of the most important of these worlds is our red and dusty neighbor , mars . today , astrobiologists are exploring places where life might once have existed on mars using nasa 's curiosity rover . one of these is gale crater , an impact crater created when a meteor hit the surface of mars nearly 3.8 billions years ago . evidence from orbit suggest past traces of water , which means the crater might once have supported life . planets are not the only places astrobiologists are looking at . for example , europa , one of the moons of jupiter , and enceladus and titan , two of saturn 's moons , are all exciting possibilities . although these moons are extremely cold and two are covered in thick ice , there is evidence of liquid oceans beneath the shell . could life be floating around in these oceans , or could it be living around black smoker vents at the bottom ? titan is particularly promising as it has an atmosphere and earth-like lakes , seas , and rivers flowing across the surface . it is very cold , however , too cold for liquid water , so these rivers may instead be flowing with liquid hydrocarbons such as methane and ethane . these are composed of hydrogen , and , more importantly , carbon , which is the basic building block of all life as we know it . so , could life be found in these lakes ? although instruments are being designed to study these distant worlds , it takes many years to build them and even longer to get them where they need to be . in the meantime , astrobiologists work in our own natural laboratory , the earth , to learn about all the weird and wonderful forms of life that can exist and to help us one day answer one of humanity 's oldest questions : are we alone ?
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many ancient religions described other worlds inhabited by known human beings , but these are more like mythical realms or parallel universes than other planets existing in the same physical world . it is only within the last century that scientists have been able to seriously undertake the search for extraterrestrial life . we know that at the most basic level organisms on earth need three things : liquid water , a source of energy , and organic , carbon-based material .
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astrobiology is the search for _____ in the universe .
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so element 96 was curium which named after marie curie and pierre curie who were the discoverers of radium . because of its high levels of radioactivity curium can be used in thermoelectric generators to produce electricity and you ’ ll get about 120 watts per hour out of one of these . however , because it is so radioactive no-one ’ s really interested in using it in commercial processes . well , past uranium everything is synthetically made , you need access to nuclear power stations or nuclear bombs or big colliders to be able to make these elements . they are extremely radioactive , very hard to handle , and only a handful of places in the uk have got the sort of facilities you need to deal with these types of compounds . so even somebody such as myself , it ’ s not really what i do , it ’ s a little bit beyond where my area is . i ’ d pretty much stop at uranium . that ’ s the limit of normal laboratory chemistry .
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so element 96 was curium which named after marie curie and pierre curie who were the discoverers of radium . because of its high levels of radioactivity curium can be used in thermoelectric generators to produce electricity and you ’ ll get about 120 watts per hour out of one of these .
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pierre curie was killed in 1906 and his wife , the famous marie curie , died in 1934. do you know when curium , named after this pair of great scientists , was discovered ?
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are you as good at things as you think you are ? how good are you at managing money ? what about reading people 's emotions ? how healthy are you compared to other people you know ? are you better than average at grammar ? knowing how competent we are and how are skill stack up against other people 's is more than a self-esteem boost . it helps us figure out when we can forge ahead on our own decisions and instincts and when we need , instead , to seek out advice . but psychological research suggests that we 're not very good at evaluating ourselves accurately . in fact , we frequently overestimate our own abilities . researchers have a name for this phenomena , the dunning-kruger effect . this effect explains why more than 100 studies have shown that people display illusory superiority . we judge ourselves as better than others to a degree that violates the laws of math . when software engineers at two companies were asked to rate their performance , 32 % of the engineers at one company and 42 % at the other put themselves in the top 5 % . in another study , 88 % of american drivers described themselves as having above average driving skills . these are n't isolated findings . on average , people tend to rate themselves better than most in disciplines ranging from health , leadership skills , ethics , and beyond . what 's particularly interesting is that those with the least ability are often the most likely to overrate their skills to the greatest extent . people measurably poor at logical reasoning , grammar , financial knowledge , math , emotional intelligence , running medical lab tests , and chess all tend to rate their expertise almost as favorably as actual experts do . so who 's most vulnerable to this delusion ? sadly , all of us because we all have pockets of incompetence we do n't recognize . but why ? when psychologists dunning and kruger first described the effect in 1999 , they argued that people lacking knowledge and skill in particular areas suffer a double curse . first , they make mistakes and reach poor decisions . but second , those same knowledge gaps also prevent them from catching their errors . in other words , poor performers lack the very expertise needed to recognize how badly they 're doing . for example , when the researchers studied participants in a college debate tournament , the bottom 25 % of teams in preliminary rounds lost nearly four out of every five matches . but they thought they were winning almost 60 % . without a strong grasp of the rules of debate , the students simply could n't recognize when or how often their arguments broke down . the dunning-kruger effect is n't a question of ego blinding us to our weaknesses . people usually do admit their deficits once they can spot them . in one study , students who had initially done badly on a logic quiz and then took a mini course on logic were quite willing to label their original performances as awful . that may be why people with a moderate amount of experience or expertise often have less confidence in their abilities . they know enough to know that there 's a lot they do n't know . meanwhile , experts tend to be aware of just how knowledgeable they are . but they often make a different mistake : they assume that everyone else is knowledgeable , too . the result is that people , whether they 're inept or highly skilled , are often caught in a bubble of inaccurate self-perception . when they 're unskilled , they ca n't see their own faults . when they 're exceptionally competent , they do n't perceive how unusual their abilities are . so if the dunning-kruger effect is invisible to those experiencing it , what can you do to find out how good you actually are at various things ? first , ask for feedback from other people , and consider it , even if it 's hard to hear . second , and more important , keep learning . the more knowledgeable we become , the less likely we are to have invisible holes in our competence . perhaps it all boils down to that old proverb : when arguing with a fool , first make sure the other person is n't doing the same thing .
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but they often make a different mistake : they assume that everyone else is knowledgeable , too . the result is that people , whether they 're inept or highly skilled , are often caught in a bubble of inaccurate self-perception . when they 're unskilled , they ca n't see their own faults .
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what ’ s a possible way to gain an accurate self-image ?
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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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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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the author says , “ variety may be the spice of life , but brevity is its
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translator : andrea mcdonough reviewer : bedirhan cinar nameste . i 'm from india , and india is one of the oldest civilizations in the world . it has contributed to the world concepts such as yoga , ayurveda , spicy chicken tikka , and vedic math . vedic math is one of the world 's easiest and simplest way to do math . we are going to combine together and do some number crunching today . so what we are going to first do is multiply by 11 . we 're going to do it together , so if you blink , you 're going to miss it . so just watch it , ok . so we 're going to do 32 times 11 , ok . so we split 3 , and we split 2 , and we add 3 and 2 and paste it on top , and we get the answer as 352 . that 's it . let 's try another sum . 45 times 11 . let 's hear it . exactly , that 's 495 . and 75 times 11 . so it gives you 7,125 , 1 gets carried over and it becomes 825 . that 's how simple it is . ok , this is the principle behind it where a is the coefficient . let 's move on . ok , now what we 're going to do is the base method . ok , this is used to multiply numbers very close to the powers of 10 , like 10 , 100 , 1,000 , and so on . so we have a sum here , say 99 times 97 . ok , now tell me , is 99 more than 100 or less than 100 ? less by how much ? so we write minus 01 . and 97 is less than 100 by how much ? so we write minus 03 . so what we 're going to do is we 're going to cross subtract and get the first part of the answer , like this . we 're going to do cross subtraction . 97 minus 01 would give us 96. and we multiply 03 times 01 vertically , and we get an answer of 03 . let 's check another sum . try and do it yourselves . we got 98 , which is , is it more than a 100 , less than 100 ? by how much ? and 97 is 3 . so we got 98 , we go crosswise , we got 98 minus 3 , or we can do 97 minus 2 , they 'll all give you the same answer . so that would give us 95 . and the second part would be 06 . so that 's our answer . ok , let 's take a bigger number . let 's try this one . here the base is 1,000 . so we got -004 , and 997 would be -003 . we go crosswise like this , and we get 996 minus 003 would give us 993 , and 004 times 003 would give us 012 . and that 's our answer . thank you . 14 times 12 . ok , here the base is 10 . ok , so is 14 more than 10 or less than 10 ? more , so we got plus 4 , and 12 , we got plus 2 . again , we apply the same rule , so we do 12 plus 4 , which gives us 16 , like this . and we multiply 2 and 4 , that gives us 8 . so now , all of us here , we 're going to do mental squaring , ok. everybody is going to participate here , and we 're going to do squares of numbers more than 100 mentally right now . so we got 101 , ok , now visualize on the board , what 's going to be on the right hand side . plus 01 , so we got that . ok , now we add plus sides , right ? yes ? no ? so we got 101 plus 01 , that would give us 102 , and , see here , like this . and 01 is getting squared , right ? so that would give us 01 , and that 's your answer . try the next one . let 's try 102 squared . let 's try , everybody . so 100 , so 102 would be 10404 . ok , now the next one , try it everybody together . i 'll give you 5 seconds . ok , let 's say it together , let 's say it together , ok. [ 10609 ] 10609 and that 's the answer . woo ! 104 squared , how much would that be ? calculate it , 5 seconds . come on , girls in the back . ok , so the answer would be 10816 . ok , let 's do the next one : 105 squared . oh , no , no , no , no , we 're going to try over , we 're going to try over , ok ? ok . i 'll give you 5 seconds , just think about it . ok , now we 're going to go , ok ? 11025 . ok , let 's going to do the next one , 106 squared . try it , come one , everybody , it 's simple and easy . [ 11236 ] ok , let 's do it one more time . 11236 . now 107 , think , hold on , do n't say anything out loud , just think mentally , 107 squared . ok , now let 's say it out loud . 11449 . and 108 squared . [ 11664 ] fantastic , give yourself a round of applause , come on ! and this is the principle behind this , where a and b are the excesses or the deficiency from the base . i 'm going to teach you in vedic math , there are 16 sutras , or word formulas , ok . they are very visual and one of them is called , `` vertically and crosswise , '' through which you can multiply any number by any number in a single line . so i 'm going to do a two-digit by a two-digit multiplication . let 's do this . so we got 31 times 12 . ok , so we 're going to apply the vertically and crosswise sutra . so we 're going to do like this : vertically , and then we 're going to go crosswise , and then we 're going to do vertical again . so , 2 times 1 gives us [ 2 ] , 2 times 3 gives us [ 6 ] , and 1 times 1 gives us [ 1 ] . 6 plus 1 , [ 7 ] . 1 times 3 gives us [ 3 ] . and that 's it , and that 's our answer . no more tedious calculations , no more going through the rough work , it 's simple in one line . i want to show you a sum again , this time with carry-overs . the same formula , all of us here can do this , ok . same formula . so let 's get started . 4 times 2 gives us [ 8 ] . ok , now we go crosswise like this , so we 're going to multiply 4 times 1 , [ 4 ] , and 3 times 2 , [ 6 ] 4 plus 6 gives us [ 10 ] . so we put down 0 , carry the 1 . and 3 times 1 gives us [ 3 ] , plus 1 , [ 4 ] . exactly , that 's our answer , 408 . ok , thank you for being such a participative audience , and we had a great time number crunching . now i want to end with a question : whether you 'd like math to be dull or boring , or fun and interesting ? the choice is yours .
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it has contributed to the world concepts such as yoga , ayurveda , spicy chicken tikka , and vedic math . vedic math is one of the world 's easiest and simplest way to do math . we are going to combine together and do some number crunching today .
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using vedic math , what do you get when you square the number 105 ?
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most people recognize his name and know that he is famous for having said something , but considering the long-lasting impact his teachings have had on the world , very few people know who confucius really was , what he really said , and why . amid the chaos of 6th century bce china , where warring states fought endlessly among themselves for supremacy , and rulers were frequently assassinated , sometimes by their own relatives , confucius exemplified benevolence and integrity , and through his teaching , became one of china 's greatest philosophers . born to a nobleman but raised in poverty from a very young age following the untimely death of his father , confucius developed what would become a lifelong sympathy for the suffering of the common people . barely supporting his mother and disabled brother as a herder and account keeper at a granary , and with other odd jobs , it was only with the help of a wealthy friend that confucius was able to study at the royal archives , where his world view would be formed . though the ancient texts there were regarded by some as irrelevant relics of the past , confucius was inspired by them . through study and reflection , confucius came to believe that human character is formed in the family and by education in ritual , literature , and history . a person cultivated in this way works to help others , guiding them by moral inspiration rather than brute force . to put his philosophy into practice , confucius became an advisor to the ruler of his home state of lu . but after another state sent lu 's ruler a troop of dancing girls as a present and the ruler ignored his duties while enjoying the girls in private , confucius resigned in disgust . he then spent the next few years traveling from state to state , trying to find a worthy ruler to serve , while holding fast to his principles . it was n't easy . in accordance with his philosophy , and contrary to the practice of the time , confucius dissuaded rulers from relying on harsh punishments and military power to govern their lands because he believed that a good ruler inspires others to spontaneously follow him by virtue of his ethical charisma . confucius also believed that because the love and respect we learn in the family are fundamental to all other virtues , personal duties to family sometimes supersede obligations to the state . so when one duke bragged that his subjects were so upright that a son testified against his own father when his father stole a sheep , confucius informed the duke that genuinely upright fathers and sons protected one another . during his travels , confucius almost starved , he was briefly imprisoned , and his life was threatened at several points . but he was not bitter . confucius had faith that heaven had a plan for the world , and he taught that a virtuous person could always find joy in learning and music . failing to find the ruler he sought , confucius returned to lu and became a teacher and philosopher so influential , that he helped shaped chinese culture and we recognize his name worldwide , even today . for the disciples of confucius , he was the living embodiment of a sage who leads others through his virtue , and they recorded his sayings , which eventually were edited into a book we know in english as `` the analects . '' today , millions of people worldwide adhere to the principles of confucianism , and though the precise meaning of his words has been debated for millennia , when asked to summarize his teachings in a single phrase , confucius himself said , `` do not inflict upon others that which you yourself would not want . '' 2,500 years later , it 's still sage advice .
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for the disciples of confucius , he was the living embodiment of a sage who leads others through his virtue , and they recorded his sayings , which eventually were edited into a book we know in english as `` the analects . '' today , millions of people worldwide adhere to the principles of confucianism , and though the precise meaning of his words has been debated for millennia , when asked to summarize his teachings in a single phrase , confucius himself said , `` do not inflict upon others that which you yourself would not want . '' 2,500 years later , it 's still sage advice .
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what advice would you have given to rulers during the era of confucius ?
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what do euclid , twelve-year-old einstein , and american president james garfield have in common ? they all came up with elegant proofs for the famous pythagorean theorem , the rule that says for a right triangle , the square of one side plus the square of the other side is equal to the square of the hypotenuse . in other words , a²+b²=c² . this statement is one of the most fundamental rules of geometry , and the basis for practical applications , like constructing stable buildings and triangulating gps coordinates . the theorem is named for pythagoras , a greek philosopher and mathematician in the 6th century b.c. , but it was known more than a thousand years earlier . a babylonian tablet from around 1800 b.c . lists 15 sets of numbers that satisfy the theorem . some historians speculate that ancient egyptian surveyors used one such set of numbers , 3 , 4 , 5 , to make square corners . the theory is that surveyors could stretch a knotted rope with twelve equal segments to form a triangle with sides of length 3 , 4 and 5 . according to the converse of the pythagorean theorem , that has to make a right triangle , and , therefore , a square corner . and the earliest known indian mathematical texts written between 800 and 600 b.c . state that a rope stretched across the diagonal of a square produces a square twice as large as the original one . that relationship can be derived from the pythagorean theorem . but how do we know that the theorem is true for every right triangle on a flat surface , not just the ones these mathematicians and surveyors knew about ? because we can prove it . proofs use existing mathematical rules and logic to demonstrate that a theorem must hold true all the time . one classic proof often attributed to pythagoras himself uses a strategy called proof by rearrangement . take four identical right triangles with side lengths a and b and hypotenuse length c. arrange them so that their hypotenuses form a tilted square . the area of that square is c² . now rearrange the triangles into two rectangles , leaving smaller squares on either side . the areas of those squares are a² and b² . here 's the key . the total area of the figure did n't change , and the areas of the triangles did n't change . so the empty space in one , c² must be equal to the empty space in the other , a² + b² . another proof comes from a fellow greek mathematician euclid and was also stumbled upon almost 2,000 years later by twelve-year-old einstein . this proof divides one right triangle into two others and uses the principle that if the corresponding angles of two triangles are the same , the ratio of their sides is the same , too . so for these three similar triangles , you can write these expressions for their sides . next , rearrange the terms . and finally , add the two equations together and simplify to get ab²+ac²=bc² , or a²+b²=c² . here 's one that uses tessellation , a repeating geometric pattern for a more visual proof . can you see how it works ? pause the video if you 'd like some time to think about it . here 's the answer . the dark gray square is a² and the light gray one is b² . the one outlined in blue is c² . each blue outlined square contains the pieces of exactly one dark and one light gray square , proving the pythagorean theorem again . and if you 'd really like to convince yourself , you could build a turntable with three square boxes of equal depth connected to each other around a right triangle . if you fill the largest square with water and spin the turntable , the water from the large square will perfectly fill the two smaller ones . the pythagorean theorem has more than 350 proofs , and counting , ranging from brilliant to obscure . can you add your own to the mix ?
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a babylonian tablet from around 1800 b.c . lists 15 sets of numbers that satisfy the theorem . some historians speculate that ancient egyptian surveyors used one such set of numbers , 3 , 4 , 5 , to make square corners .
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which of the following sets of the numbers consists of a pythagorean triple ( whole numbers which satisfy the pythagorean theorem ) ?
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now , my subject is success , so people sometimes call me a `` motivational speaker . '' but i want you to know right up front i 'm not a motivational speaker . i could n't pass the height requirement . ( laughter ) and i could n't motivate anybody . my employees actually call me a de-motivational speaker . ( laughter ) what i try to be is an informational speaker . i went out and found out some information about success , and i 'm just here to pass it on . and my story started over ten years ago , on a plane . i was on my way to the ted conference in california , and in the seat next to me was a teenage girl , and she came from a really poor family , but she wanted to get somewhere in life . and as i tapped away on my computer , she kept asking me questions , and then out of the blue , she asked , `` are you successful ? '' i said , `` no , i 'm not successful . '' terry fox , my hero , now there 's a big success . he lost a leg to cancer , then ran thousands of miles and raised millions for cancer research . or bill gates , a guy who owns his own plane and does n't have to sit next to some kid asking him questions . ( laughter ) but then i told her about some of the stuff i 'd done . i love communications , and i 've won lots of awards in marketing . i love running , and i still sometimes win my age group , old farts over 60 . ( laughter ) my fastest marathon is two hours and 43 minutes to run the 26 miles , or 42 kilometers . i 've run over 50 marathons , in all 7 continents . this was a run my wife and i did up the inca trail to machu picchu in peru . and to qualify for the 7 continents , we had to run a marathon in antarctica . but when we got there , it did n't look nice and calm like this , it looked like this . the waves were so high , we could n't get to shore . so we sailed 200 miles further south to where the seas were calm and ran the entire 26-mile marathon on the boat . 422 laps around the deck of that little boat . my wife and i have also climbed two of the world 's seven summits , the highest mountains on each continent . we climbed aconcagua , the highest mountain on the american continent , and kilimanjaro , the highest mountain in africa . well , to be honest , i puked my way to the top of kilimanjaro , i got altitude sickness . i got no sympathy from my wife . she passed me and did a lap around the top while i was still struggling up there . in spite of that , we 're still together and have been for over 35 years . ( applause ) i 'd say that 's a success these days . so i said to the girl , `` well , you know , i guess i have had some success . '' and then she said , `` okay , so are you a millionaire ? '' ( laughter ) now , i did n't know what to say , because when i grew up , it was bad manners to talk about money . but i figured i 'd better be honest , and i said , `` yeah . i 'm a millionaire . but i do n't know how it happened . i never went after the money , and it 's not that important to me . '' she said , `` maybe not to you , but it is to me . i do n't want to be poor all my life . i want to get somewhere , but it 's never going to happen . '' i said , `` well , why not ? '' she said , `` well , you know , i 'm not very smart . i 'm not doing great in school . '' i said , `` so what ? i 'm not smart . i barely passed high school . i had absolutely nothing going for me . i was never voted most popular or most likely to succeed . i started a whole new category -- most likely to fail . but in the end , i did okay . so if i can do it , you can do it . '' and then she asked me the big question : `` okay , so what really leads to success ? '' i said , `` jeez , sorry . i do n't know . i guess somehow i did it . i do n't know how i did it . '' so i get off the plane and go to the ted conference , and i 'm standing in a room full of extraordinarily successful people in many fields -- business , science , arts , health , technology , the environment -- when it hit me : why do n't i ask them what helped them succeed , and find out what really leads to success for everyone ? so i was all excited to get out there and start talking to these great people , when the self-doubt set in . i mean , why would people want to talk to me ? i 'm not a famous journalist . i 'm not even a journalist . so i was ready to stop the project before it even began , when who comes walking towards me but ben cohen , the famous co-founder of ben and jerry 's ice cream . i figured it was now or never . i pushed through the self-doubt , jumped out in front of him , and said , `` ben , i 'm working on this project . i do n't even know what to ask you , but can you tell me what helped you succeed ? '' he said , `` yeah , sure , come on . let 's go for a coffee . '' and over coffee and ice cream , ben told me his story . now here we are over 10 years later , and i 've interviewed over 500 successful people face-to-face , and collected thousands of other success stories . i wanted to find the common factors for success in all fields , so i had to interview people in careers ranging from a to z . these are just the careers i interviewed beginning with the letter a , and in most cases more than one person . i interviewed six successful accountants , five corporate auditors , five astronauts who had been into space , four actors who had won the academy award for best actor , three of the world 's top astrophysicists , six of the world 's leading architects and , oh yeah , four nobel prize winners . yeah , i know it does n't start with a , but it 's kind of cool . ( laughter ) and i want to say a sincere thanks to all the great people that i 've interviewed over the years . this really is their story ; i 'm just the messenger . the really big job was taking all the interviews and analyzing them , word by word , line by line , and sorting them into all the factors that people said helped them succeed . and then you start to see the big factors that are common to most people 's success . altogether , i analyzed and sorted millions of words . do you know how much work that is ? that 's all i do , day and night -- sort and analyze . i 'll tell you , if i ever get my hands on that kid on the plane -- ( laughter ) actually , if i do , i 'll thank her . because i 've never had so much fun and met so many interesting people . and now , i can answer her question . i discovered the 8 traits successful people have in common , or the 8 to be great : love what you do ; work really hard ; focus on one thing , not everything ; keep pushing yourself ; come up with good ideas ; keep improving yourself and what you do ; serve others something of value , because success is n't just about me , me , me ; and persist , because there 's no overnight success . why did i pick these ? because when i added up all the comments in my interviews , more people said those 8 things helped them than anything else . the eight traits are really the heart of success , the foundation , and then on top we build the specific skills that we need for our particular field or career . technical skills , analytical skills , people skills , creative skills -- lots of other skills we can add on top , depending on our field . but no matter what field we 're in , these eight traits will be at the heart of our success . ( applause )
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i 'm not smart . i barely passed high school . i had absolutely nothing going for me .
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what best describes me in high school ?
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it 's a good day to be a pirate . amaro and his four mateys , bart , charlotte , daniel , and eliza have struck gold : a chest with 100 coins . but now , they must divvy up the booty according to the pirate code . as captain , amaro gets to propose how to distribute the coins . then , each pirate , including amaro himself , gets to vote either yarr or nay . if the vote passes , or if there 's a tie , the coins are divided according to plan . but if the majority votes nay , amaro must walk the plank and bart becomes captain . then , bart gets to propose a new distribution and all remaining pirates vote again . if his plan is rejected , he walks the plank , too , and charlotte takes his place . this process repeats , with the captain 's hat moving to daniel and then eliza until either a proposal is accepted or there 's only one pirate left . naturally , each pirate wants to stay alive while getting as much gold as possible . but being pirates , none of them trust each other , so they ca n't collaborate in advance . and being blood-thirsty pirates , if anyone thinks they 'll end up with the same amount of gold either way , they 'll vote to make the captain walk the plank just for fun . finally , each pirate is excellent at logical deduction and knows that the others are , too . what distribution should amaro propose to make sure he lives ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 if we follow our intuition , it seems like amaro should try to bribe the other pirates with most of the gold to increase the chances of his plan being accepted . but it turns out he can do much better than that . why ? like we said , the pirates all know each other to be top-notch logicians . so when each votes , they wo n't just be thinking about the current proposal , but about all possible outcomes down the line . and because the rank order is known in advance , each can accurately predict how the others would vote in any situation and adjust their own votes accordingly . because eliza 's last , she has the most outcomes to consider , so let 's start by following her thought process . she 'd reason this out by working backwards from the last possible scenario with only her and daniel remaining . daniel would obviously propose to keep all the gold and eliza 's one vote would not be enough to override him , so eliza wants to avoid this situation at all costs . now we move to the previous decision point with three pirates left and charlotte making the proposal . everyone knows that if she 's outvoted , the decision moves to daniel , who will then get all the gold while eliza gets nothing . so to secure eliza 's vote , charlotte only needs to offer her slightly more than nothing , one coin . since this ensures her support , charlotte does n't need to offer daniel anything at all . what if there are four pirates ? as captain , bart would still only need one other vote for his plan to pass . he knows that daniel would n't want the decision to pass to charlotte , so he would offer daniel one coin for his support with nothing for charlotte or eliza . now we 're back at the initial vote with all five pirates standing . having considered all the other scenarios , amaro knows that if he goes overboard , the decision comes down to bart , which would be bad news for charlotte and eliza . so he offers them one coin each , keeping 98 for himself . bart and daniel vote nay , but charlotte and eliza grudgingly vote yarr knowing that the alternative would be worse for them . the pirate game involves some interesting concepts from game theory . one is the concept of common knowledge where each person is aware of what the others know and uses this to predict their reasoning . and the final distribution is an example of a nash equilibrium where each player knows every other players ' strategy and chooses theirs accordingly . even though it may lead to a worse outcome for everyone than cooperating would , no individual player can benefit by changing their strategy . so it looks like amaro gets to keep most of the gold , and the other pirates might need to find better ways to use those impressive logic skills , like revising this absurd pirate code .
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since this ensures her support , charlotte does n't need to offer daniel anything at all . what if there are four pirates ? as captain , bart would still only need one other vote for his plan to pass .
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why can ’ t the pirates coordinate their votes ?
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translator : andrea mcdonough reviewer : bedirhan cinar picture this : your friend and you are watching a sitcom and a sassy sidekick walks into a room , carrying a four-tiered wedding cake . he trips , falls , and face-plants into the cake . your friend doubles over with laughter and says , `` it 's so ridiculous ! so ironic ! '' well , quick , what do you do ? do you laugh along with the laugh track and let this grievous misinterpretation of irony go ? or , do you throw caution to the wind and explain the true meaning of irony ? if you 're me , you choose the latter . unfortunately , irony has been completely misunderstood . we tend to throw out that term whenever we see something funny or coincidental . and while many examples of true irony can be funny , that is not the driving factor of being ironic . a situation is only ironic if what happens is the exact opposite of what was expected . if you expect a , but get b , then you have irony . let 's take the slap-stick cake situation as an example . when someone walks in precariously balancing something that should n't be carried alone , trips , falls , and makes a mess , it is funny , but it 's not ironic . in fact , you probably expect someone who is single-handedly carrying a huge cake to trip . when he does , reality aligns with expectations , and so that is not irony . but what if the sassy sidekick walked in wearing a gold medal that he 'd won at the cake walking event at the atlanta olympics in 1996 ? what if that sidekick was a professional cake carrier ? then , maybe there would have been a reasonable expectation that he would have been more skilled when carrying a ridiculously large cake . then , when that reasonable expectation was not met by the tripping sidekick , irony would have been exemplified . another example . a senior citizen texting and blogging . the common and reasonable expectation of more mature men and women is that they do n't like or know technology , that they have a hard time turning on a computer , or that they have the old brick cell phones from the 1980s . one should not expect them to be connected , high-tech , or savvy enough to text or to be blogging , which must seem like some sort of newfangled thing that `` back in my day , '' they never had . so when granny pulls out her smart phone to post pictures of her dentures or her grandkids , irony ensues . reasonable expectations of the situation are not met . that is irony . so while the cake dropper might not be ironic , there are all kinds of situations in life that are . go out , and find those true examples of irony .
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your friend doubles over with laughter and says , `` it 's so ridiculous ! so ironic ! '' well , quick , what do you do ?
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have you ever misinterpreted a situation as ironic ? explain the situation and why you thought it was ironic .
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so , you 're thinking of moving to mars . have you picked out a spot for your new home ? no ? well , i 'm here to help . first things first , here are some of the things you 'll need to bring to the red planet : a high tolerance for cold , loneliness , and radiation ; a lifetime supply of breathable air and food ; a multibillion dollar spaceship ; a desire to just get away from it all ; and water . you 're definitely going to need water . so what sort of real estate are you looking for ? how about a mansion in the maze-like noctis labyrinthus ? a hideaway in the happy face crater ? a fortress on the face mesa ? an oceanview ? uh , bad news on the last one . you 're about 4 billion years late . we 're pretty sure that mars used to have oceans , lakes , rivers , the whole package . but over time , almost all of it froze beneath the surface , or evaporated off into space . there 's probably still some trapped beneath the seasonally expanding and contracting carbon dioxide ice caps , though . so what might mars look like today if it had surface water ? that , of course , depends on how much we 're talking about , but maybe something like this . the relatively flat northern hemisphere is below the average elevation , so it would become one giant ocean , while the crater-ridden southern hemisphere would stay mostly high and dry . that difference between hemispheres is a bit bizarre , and we do n't know why it 's like that . the southern half is probably much older , judging by features like the number of craters , and the evidence of increased volcanic activity in the north . okay , so who knows ? maybe one day mars will have oceans again , but for now , what we 've got is essentially one giant dusty desert . in fact , it 's similar enough to deserts on earth , that we 've been able to learn a great deal about mars on our home planet . for instance , martian sand dunes form and behave similarly to our sand dunes , though the martian versions often grow twice as large thanks to a gravitational pull that 's about a third as strong as ours . and mars has some features you wo n't see on earth , like tars , which are crestless sand dunes up to fifteen meters tall , whose formations we have yet to understand . you 're probably wondering , `` what do you get when you combine a planet-wide desert with an atmosphere that , like ours , is subject to wind-generating pressure differentials , dust storms ? '' these will be your main weather hazards on the red planet . they play a large part in making the planet red by distributing rusted iron particles across the surface and into the air . thanks to the low gravity and lack of moisture , these dust storms can last for months and cover the planet . so , you might want to build your home as high as possible . well , look no further . this is olympus mons , the largest volcano in the solar system . even if mars had a breathable atmosphere , you 'd find the views from the 25 kilometer summit breathtaking . or are volcanos not your thing ? then how about valles marineris , the largest canyon in the solar system ? it 's so wide that from one side , the opposite rim would be below the curve of the horizon . still , you 'll catch some spectacular blue sunsets in the normally red sky , which gets its color from the dust absorbing most of the blue light , and the way sunlight is scattered by the atmosphere . have you got spirit , curiosity , or are you just looking for opportunity ? then stop stalling and make the move to mars today . mars : redder than ever .
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well , look no further . this is olympus mons , the largest volcano in the solar system . even if mars had a breathable atmosphere , you 'd find the views from the 25 kilometer summit breathtaking .
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how tall is the largest volcano in our solar system ?
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translator : andrea mcdonough reviewer : bedirhan cinar let me guess , you 've got facebook albums full of photos . you have photos on your computer desktop , on your mobile phone , on your bedroom wall . you see photos in magazines and newspapers , on the side of buses , and of course , in your family albums . we take photos for granted in a major way . but , creating a picture that looked exactly like the person or thing that you were photographing was n't always obvious . in fact , in the past , it was a big mystery . how could you , in essence , take your reflection in the mirror and freeze it in there ? in the 9th century , the arab scientist alhazen had come up with the idea of using the camera obscura , which was literally a dark room , or box , with a single , small hole in one side that let light through . this would project the image outside into the wall inside . during the renaissance , artists like leonardo davinci used this method to introduce 3-d scenes onto a flat plane so that they could copy things , like perspective , more easily . in 1724 , johann heinrich schultz discovered that exposing certain silver compounds to light altered their appearance and left marks wherever the light touched . essentially , schultz found a way to record the images that alhazen was able to project , but only for a little while . schultz 's images disappeared soon after he had made them . it was n't until 1839 that people figured out how to project images onto light-sensitive surfaces that would retain the image after exposure , and thus , photography was born . at that point , it was mostly two inventors who fought for the best way to make photos . one was british scientist henry fox talbot , whose calotype process used paper and allowed many copies to be made from a single negative . the other inventor , louis daguerre , was an artist and chemist in france . he developed something called a daguerreotype , which used a silvered plate and which produced a sharper image . but the daguerreotype could only make positive images so copies had to be made by taking another photo . in the end , the daguerreotype won out as the first commercially successful photographic process mostly because the government made it freely available to the public . so now that photography was available , getting a picture of yourself would be a snap , right ? well , not exactly ! this process still required a whole dark room at the location of the photograph , which was a big hassle . picture the early photographers lugging enormous trailers with all their equipment wherever they wanted to take a picture . not only that , but the early processes had extremely long exposure times . to get a good photo , you would have to stand perfectly still for up to two minutes ! this led to development of inventions like the head holder , a wire frame that would hide behind you while supporting your head . it 's also why you do n't see people smiling in early photographs . it 's not that life was that bad , it was just hard to keep a steady grin for more than a few seconds , so people opted for a straight-faced look . and then george eastman came along . eastman believed that everyone should have access to photography , and he spent many late nights mixing chemicals in his mother 's kitchen to try to achieve a dry plate photographic process . this would allow exposed negatives to be stored and developed later at a more convenient place instead of carting those dark rooms , necessary for wet plates , around . after starting a business , which initially made dry plates , eastman eventually discovered plastic roll film that would fit in hand-held , inexpensive cameras . these cameras sold by the millions under the tag line , `` you push the button , we do the rest . '' while eastman was largely responsible for making photography a universal pastime , even he could not have dreamed of the ways photography had since shaped the world . it 's now estimated that over 380 billion photographs are taken each year . that 's more photographs each day than were taken in the first hundred years after photography was invented . say cheese !
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he developed something called a daguerreotype , which used a silvered plate and which produced a sharper image . but the daguerreotype could only make positive images so copies had to be made by taking another photo . in the end , the daguerreotype won out as the first commercially successful photographic process mostly because the government made it freely available to the public . so now that photography was available , getting a picture of yourself would be a snap , right ? well , not exactly !
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what did the government make available to the pubilc that made it `` a snap '' to have your picture taken ?
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how do you get what you want using just your words ? aristotle set out to answer exactly that question over 2,000 years ago with the treatise on rhetoric . rhetoric , according to aristotle , is the art of seeing the available means of persuasion . and today we apply it to any form of communication . aristotle focused on oration , though , and he described three types of persuasive speech . forensic , or judicial , rhetoric establishes facts and judgements about the past , similar to detectives at a crime scene . epideictic , or demonstrative , rhetoric makes a proclamation about the present situation , as in wedding speeches . but the way to accomplish change is through deliberative rhetoric , or symbouleutikon . rather than the past or the present , deliberative rhetoric focuses on the future . it 's the rhetoric of politicians debating a new law by imagining what effect it might have , like when ronald regan warned that the introduction of medicare would lead to a socialist future spent telling our children and our children 's children what it once was like in america when men were free . but it 's also the rhetoric of activists urging change , such as martin luther king jr 's dream that his children will one day live in a nation where they will not be judged by the color of their skin , but by the content of their character . in both cases , the speaker 's present their audience with a possible future and try to enlist their help in avoiding or achieving it . but what makes for good deliberative rhetoric , besides the future tense ? according to aristotle , there are three persuasive appeals : ethos , logos , and pathos . ethos is how you convince an audience of your credibility . winston churchill began his 1941 address to the u.s. congress by declaring , `` i have been in full harmony all my life with the tides which have flowed on both sides of the atlantic against privilege and monopoly , '' thus highlighting his virtue as someone committed to democracy . much earlier , in his defense of the poet archias , roman consul cicero appealed to his own practical wisdom and expertise as a politician : `` drawn from my study of the liberal sciences and from that careful training to which i admit that at no part of my life i have ever been disinclined . '' and finally , you can demonstrate disinterest , or that you 're not motivated by personal gain . logos is the use of logic and reason . this method can employ rhetorical devices such as analogies , examples , and citations of research or statistics . but it 's not just facts and figures . it 's also the structure and content of the speech itself . the point is to use factual knowledge to convince the audience , as in sojourner truth 's argument for women 's rights : `` i have as much muscle as any man and can do as much work as any man . i have plowed and reaped and husked and chopped and mowed and can any man do more than that ? '' unfortunately , speakers can also manipulate people with false information that the audience thinks is true , such as the debunked but still widely believed claim that vaccines cause autism . and finally , pathos appeals to emotion , and in our age of mass media , it 's often the most effective mode . pathos is neither inherently good nor bad , but it may be irrational and unpredictable . it can just as easily rally people for peace as incite them to war . most advertising , from beauty products that promise to relieve our physical insecurities to cars that make us feel powerful , relies on pathos . aristotle 's rhetorical appeals still remain powerful tools today , but deciding which of them to use is a matter of knowing your audience and purpose , as well as the right place and time . and perhaps just as important is being able to notice when these same methods of persuasion are being used on you .
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and finally , you can demonstrate disinterest , or that you 're not motivated by personal gain . logos is the use of logic and reason . this method can employ rhetorical devices such as analogies , examples , and citations of research or statistics .
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logos focuses on the use of :
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try to measure a circle . the diameter and radius are easy , they 're just straight lines you can measure with a ruler . but to get the circumference , you 'd need measuring tape or a piece of string , unless there was a better way . now , it 's obvious that a circle 's circumference would get smaller or larger along with its diameter , but the relationship goes further than that . in fact , the ratio between the two , the circumference divided by the diameter , will always be the same number , no matter how big or small the circle gets . historians are n't sure when or how this number was first discovered , but it 's been known in some form for almost 4,000 years . estimates of it appear in the works of ancient greek , babylonian , chinese , and indian mathematicians . and it 's even believed to have been used in building the egyptian pyramids . mathematicians estimated it by inscribing polygons in circles . and by the year 1400 , it had been calculated to as far as ten decimal places . so , when did they finally figure out the exact value instead of just estimating ? actually , never ! you see , the ratio of a circle 's circumference to its diameter is what 's known as an irrational number , one that can never be expressed as a ratio of two whole numbers . you can come close , but no matter how precise the fraction is , it will always be just a tiny bit off . so , to write it out in its decimal form , you 'd have an on-going series of digits starting with 3.14159 and continuing forever ! that 's why , instead of trying to write out an infinite number of digits every time , we just refer to it using the greek letter pi . nowadays , we test the speed of computers by having them calculate pi , and quantum computers have been able to calculate it up to two quadrillion digits . people even compete to see how many digits they can memorize and have set records for remembering over 67,000 of them . but for most scientific uses , you only need the first forty or so . and what are these scientific uses ? well , just about any calculations involving circles , from the volume of a can of soda to the orbits of satellites . and it 's not just circles , either . because it 's also useful in studying curves , pi helps us understand periodic or oscillating systems like clocks , electromagnetic waves , and even music . in statistics , pi is used in the equation to calculate the area under a normal distribution curve , which comes in handy for figuring out distributions of standardized test scores , financial models , or margins of error in scientific results . as if that were n't enough , pi is used in particle physics experiments , such as those using the large hadron collider , not only due to its round shape , but more subtly , because of the orbits in which tiny particles move . scientists have even used pi to prove the illusive notion that light functions as both a particle and an electromagnetic wave , and , perhaps most impressively , to calculate the density of our entire universe , which , by the way , still has infinitely less stuff in it than the total number of digits in pi .
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actually , never ! you see , the ratio of a circle 's circumference to its diameter is what 's known as an irrational number , one that can never be expressed as a ratio of two whole numbers . you can come close , but no matter how precise the fraction is , it will always be just a tiny bit off .
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the ratio of a circle 's circumference to its diameter is known as :
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[ music ] they 've sat with us at nearly every table , a pair that 's partnered most of the meals ever cooked in western kitchens . a yin and yang , darkness and light . the importance of salt is crystal clear . life would n't exist without it and if it did it would taste gross and weird . but out of all the herbs and spices on the culinary roster how did this ground up gray stuff become the go-to spice of life . seriously , why not salt and turmeric or salt and mustard , salt and cumin , salt and nutmeg , salt and coriander , salt and paprika , salt and cinnamon , salt and allspice , salt and cloves . [ music ] salt , or specifically sodium chloride . it 's the only rock that we eat , the unlikely joining of a poisonous gas and an explosive-metal and when paired with water it provides both the incubator and ingredients for life . we use sodium and chloride ions to keep our cells inflated , to regulate blood pressure and convey electrical nerve impulses throughout our body . to maintain this we need to consume about six grams of sodium chloride every day . so salt 's culinary and cultural value is no surprise its history could fill a book , and it has . a great book by the way . have you guys read the book salt : a world history early hunter-gatherer societies got all the salt needed from their animal diet to this day the masai people of east africa get theirs from drinking the blood of their livestock . but as human society is shifted to growing and eating plants , salt became something you either found or traded for . the earliest sites of salt harvesting date to at least 6,000 bc in china and europe there 's salt in most of the blue wet stuff covering earth once you boil away or evaporate all that pesky h2o but there 's pure sodium chloride in earth 's crust , if you can find it . following animal trails led us to natural salt licks and some of these became our first highways . several ancient salt harvesting cities still bear a pinch of history in their name . entire economies were built around salt . it was a commodity and currency that you could eat . roman warriors deemed worth their salt where sometimes given a salary . the roman custom of salting bitter greens even gave us salad . although that caesar dressing comes from tijuana . today salt is cheap enough to manufacture that many people are in danger of eating too much . but before the industrial age it was scarce enough that people fought wars over it . it even inspired at least one revolution . before refrigeration , salting was one way to keep food from spoiling . since most harmful bacteria ca n't grow in high salt conditions . but obviously salt also changes how we experience our food . it makes things taste salty but it also accentuates other flavors . sodium chloride can chemically block bitter taste receptors and amplify those that sense sweet , salty , and umami . depending on when and how its applied to food it can change the very chemistry of how it 's cooked . salt is probably the most important ingredient on earth . but then there 's pepper . one spice to rule them all . if you thought salt was interesting , pepper is is a thing . black pepper comes from a flowering vine native to southeast asia . it gets its heat from a chemical called piperine . rather than capsaicin like those confusingly named fruits of the chili pepper family . it 's been a common ingredient in indian cooking for at least four thousand years . but small amounts of black pepper made their way to greece , rome , and even ancient egypt , where peppercorns were apparently valuable enough to stuff up the mummified nose of ramses the second . pepper became a key commodity in the spice trade stretching between asia and europe , where its main use like other pungent spices was to mask the flavor of meat that was , shall we say , past its prime . the extreme distances involved in trading pepper across the known world translated into extreme prices . to inflate them further arab traders invented a myth that pepper gardens were guarded by serpents which had to be chased away with fire before a harvest . who would n't want to put magic snake powder on their food . throughout the middle ages it was common to see many spices used in the food of the wealthy , but the enduring popularity of black pepper may owe itself to one picky eater . its said that louis xiv demanded his food lightly seasoned , preferring only salt and pepper be added . the french cuisine developed then was the basis for much of what we eat today , and now pepper is the spice and i 'm sick of it . too long we 've been forced to look at the world of spice in black and white ! held prisoner by pepper , unable to gaze upon the full rainbow of flavors and i say no more ! join me , brothers and sisters , stand together . we say yes to salt . but let us say anything but pepper ! stay spicy , and curious
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we use sodium and chloride ions to keep our cells inflated , to regulate blood pressure and convey electrical nerve impulses throughout our body . to maintain this we need to consume about six grams of sodium chloride every day . so salt 's culinary and cultural value is no surprise its history could fill a book , and it has .
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how much sodium chloride do we need to consume every day ?
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there is an environmental mystery afoot , and it begins with a seemingly trivial detail that reveals a disaster of global proportions . one day , you notice that the honey you slather on your morning toast is more expensive . instead of switching to jam , you investigate the reason for the price hike . what you find is shocking . the number of domesticated honeybees in the us has been decreasing at an alarming rate . this decline appears too big to be explained by the usual causes of bee death alone : disease , parasites or starvation . a typical crime scene has almost no adult bees left in the hive , except , perhaps , a lonely queen and a few other survivors . it 's full of untouched food stores and a brood of unborn larvae , suggesting that the adults vacated without waiting for them to hatch . but what 's particularly eerie is that there 's no tell-tale mass of dead or dying bees nearby . either they have forgotten their way back to the hive , or they have simply disappeared . these mysterious disappearances are n't new . humans have been collecting honey for centuries . but it was n't until european settlers in the 1600 's introduced the subspecies , apis mellifera , that we domesticated bees . since the 19th century , beekeepers have reported occasional mass disappearances , giving them enigmatic names like disappearing disease , spring dwindle disease and autumn collapse . but when in 2006 such losses were found to affect more than half of all hives in the us , the phenomenon got a new name : colony collapse disorder . the most frightening thing about this mystery is n't that we 'll have to go back to using regular sugar in our tea . we farm bees for their honey , but they also pollinate our crops on an industrial scale , generating over 1/3 of america 's food production this way . so , how can we find the culprit behind this calamity ? here are three of the possible offenders . exhibit a : pests and disease . most infamous is the varroa mite , a minuscule red pest that not only invades colonies and feeds on bees , but also transfers pathogens that stunt bee growth and shortens their life span . exhibit b : genetics . the queen is the core of a healthy hive . but nowadays , the millions of queen bees distributed in commercial hives are bred from just a few original queens , which raises the worry about a lack of genetic diversity which could weaken bees ' defenses against pathogens and pests . exhibit c : chemicals . pesticides used both on commercial beehives and agricultural crops to ward off parasites could be getting into the food and water that honeybees consume . researchers have even found that some pesticides damage the honeybees ' homing abilities . so we have a file full of clues but no clear leads . in reality , scientists , the actual detectives on this case , face disagreement over what causes colony collapse disorder . for now , we assume that several factors are the cause . honeybees are n't necessarily in danger of extinction , but fewer bees overall means less pollination and higher food costs , so it 's crucial that scientists solve the case of the vanishing bees . because while having less honey might be a buzzkill , crop shortages are something that would truly sting .
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exhibit a : pests and disease . most infamous is the varroa mite , a minuscule red pest that not only invades colonies and feeds on bees , but also transfers pathogens that stunt bee growth and shortens their life span . exhibit b : genetics .
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in affected colonies ________ .
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if you 're ever walking down the street and come across an oddly stretched out image , like this , you 'll have an opportunity to see something remarkable , but only if you stand in exactly the right spot . that happens because these works employ a technique called anamorphosis . anamorphosis is a special case of perspective art , where artists represent realistic three-dimensional views on two-dimensional surfaces . though it 's common today , this kind of perspective drawing has only been around since the italian renaissance . ancient art often showed all figures on the same plane , varying in size by symbolic importance . classical greek and roman artists realized they could make objects seem further by drawing them smaller , but many early attempts at perspective were inconsistent or incorrect . in 15th century florence , artists realized the illusion of perspective could be achieved with higher degrees of sophistication by applying mathematical principles . in 1485 , leonardo da vinci manipulated the mathematics to create the first known anamorphic drawing . a number of other artists later picked up the technique , including hans holbein in `` the ambassadors . '' this painting features a distorted shape that forms into a skull as the viewer approaches from the side . in order to understand how artists achieve that effect , we first have to understand how perspective drawings work in general . imagine looking out a window . light bounces off objects and into your eye , intersecting the window along the way . now , imagine you could paint the image you see directly onto the window while standing still and keeping only one eye open . the result would be nearly indistinguishable from the actual view with your brain adding depth to the 2-d picture , but only from that one spot . standing even just a bit off to the side would make the drawing lose its 3-d effect . artists understand that a perspective drawing is just a projection onto a 2-d plane . this allows them to use math to come up with basic rules of perspective that allow them to draw without a window . one is that parallel lines , like these , can only be drawn as parallel if they 're parallel to the plane of the canvas . otherwise , they need to be drawn converging to a common point known as the vanishing point . so that 's a standard perspective drawing . with an anamorphic drawing , like `` the ambassadors , '' directly facing the canvas makes the image look stretched and distorted , but put your eye in exactly the right spot way off to the side , and the skull materializes . going back to the window analogy , it 's as if the artist painted onto a window positioned at an angle instead of straight on , though that 's not how renaissance artists actually created anamorphic drawings . typically , they draw a normal image onto one surface , then use a light , a grid , or even strings to project it onto a canvas at an angle . now let 's say you want to make an anamorphic sidewalk drawing . in this case , you want to create the illusion that a 3-d image has been added seamlessly into an existing scene . you can first put a window in front of the sidewalk and draw what you want to add onto the window . it should be in the same perspective as the rest of the scene , which might require the use of those basic rules of perspective . once the drawing 's complete , you can use a projector placed where your eye was to project your drawing down onto the sidewalk , then chalk over it . the sidewalk drawing and the drawing on the window will be nearly indistinguishable from that point of view , so viewers ' brains will again be tricked into believing that the drawing on the ground is three-dimensional . and you do n't have to project onto a flat surface to create this illusion . you can project onto multiple surfaces , or assemble a jumble of objects , that from the right point of view , appears to be something else entirely . all over the planet , you can find solid surfaces giving way to strange , wonderful , or terrifying visions . from your sidewalk to your computer screen , these are just some of the ways that math and perspective can open up whole new worlds .
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in order to understand how artists achieve that effect , we first have to understand how perspective drawings work in general . imagine looking out a window . light bounces off objects and into your eye , intersecting the window along the way .
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how many places are there to place our eye for a projected image on the window to exactly match up with the world outside of the window ?
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how old is the earth ? well , by counting the number of isotopes in a sample of rock that 's undergone radioactive decay , geologists have estimated the earth 's birthday , when it first formed from a solar nebula , to be 4.6 billion years ago . but just how long is that really ? here 's some analogies that might help you understand . for example , let 's imagine the entire history of earth until the present day as a single calendar year . on january 1st , the earth begins to form . by march 3rd , there 's the first evidence of single-celled bacteria . life remains amazingly unicellular until november 11th when the first multicellular organisms , known as the ediacaran fauna , come along . shortly thereafter , on november 16th at 6:08 p.m. is the cambrian explosion of life , a major milestone , when all of the modern phyla started to appear . on december 10th at 1:26 p.m. , the dinosaurs first evolve but are wiped out by an asteroid just two weeks later . on december 31st , the mighty roman empire rises and falls in just under four seconds . and columbus sets sail for what he thinks is india at three seconds to midnight . if you try to write the history of the earth using just one page per year , your book would be 145 miles thick , more than half the distance to the international space station . the story of the 3.2 million year-old australopithecine fossil known as lucy would be found on the 144th mile , just over 500 feet from the end of the book . the united states of america 's declaration of independence would be signed in the last half-inch . or if we compared geologic time to a woman stretching her arms to a span of six feet , the simple act of filing her nails would wipe away all of recorded human history . finally , let 's imagine the history of the earth as your life : from the moment you 're born to your first day of high school . your first word , first time sitting up , and first time walking would all take place while life on earth was comprised of single-celled organisms . in fact , the first multicellular organism would n't evolve until you were 12 years old and starting 7th grade , right around the time your science teacher is telling the class how fossils are formed . the dinosaurs do n't appear until three months into 8th grade and are soon wiped out right around spring break . three days before 9th grade begins , when you realize summer is over and you need new school supplies , lucy , the australopithecine , is walking around africa . as you finish breakfast and head outside to catch your bus 44 minutes before school , the neanderthals are going extinct throughout europe . the most recent glacial period ends as your bus drops you off 16 minutes before class . columbus sets sail 50 seconds before class as you 're still trying to find the right classroom . the declaration of independence is signed 28 seconds later as you look for an empty seat . and you were born 1.3 seconds before the bell rings . so , you see , the earth is extremely , unbelievably old compared to us humans with a fossil record hiding incredible stories to tell us about the past and possibly the future as well . but in the short time we 've been here , we 've learned so much and will surely learn more over the next decades and centuries , near moments in geological time .
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finally , let 's imagine the history of the earth as your life : from the moment you 're born to your first day of high school . your first word , first time sitting up , and first time walking would all take place while life on earth was comprised of single-celled organisms . in fact , the first multicellular organism would n't evolve until you were 12 years old and starting 7th grade , right around the time your science teacher is telling the class how fossils are formed .
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relative to the percent of time dominating the surface of earth which organisms have the longest reign ?
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what ’ s the next element ? hassium . i know nothing about hassium , shall we make something up ? hassium is an element which i knew nothing about . but now i discover it ’ s much more interesting than i thought . we ’ re here in the german state of hesse at the institute gsi were hassium was first made in 1984 . hassia is the latin name for this part of germany hesse and hence it is named after the place it was discovered . so down here we have the accelerator that accelerated atoms of iron to bang into a lead target to make element 108 hassium . element 108 is actually in the same group of the periodic table as iron , that much i knew when i first talked about it . but what i didn ’ t realise is that the element has a few atoms that are long enough lived that you can really do chemistry . so once the atom flies off from the back of the target when it has been created you can pass it through an atmosphere of oxygen and make the oxide hassium tetroxide hs04 . and the iron of this molecule , this oxide can then be followed to see how volatile it is and compared with osmium tetroxide . osmium tetroxide is a white solid which is quite volatile , it easily evaporates and you can show that hassium tetroxide does not evaporate quite so easily . but it ’ s amazing this is an element only forty atoms have been made but you can tell how its oxide behaves . osmium has one of the highest melting points of any element that ’ s known . the people who make periodic tables where you have a sample of each element have great trouble melting osmium to make a sample , so it may be that hassium would have an even higher melting point , it could be that it ’ s the highest melting point in the periodic table . but one would have to make a lot more atoms than that if you were going to find out what the melting point was . i think people may be able to calculate it , but the melting point depends on the strength of the interaction between the atoms and unless you have quite a few atoms that ’ s very difficult to measure . and quite a few means many tens of millions because even a small particle , a so called nanoparticle , of metal can have quite different properties from a large lump .
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hassia is the latin name for this part of germany hesse and hence it is named after the place it was discovered . so down here we have the accelerator that accelerated atoms of iron to bang into a lead target to make element 108 hassium . element 108 is actually in the same group of the periodic table as iron , that much i knew when i first talked about it .
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which atoms were accelerated at a lead target , in the accelerator the professor showed us at gsi ?
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in 1985 , three researchers on a dolphin-studying expedition got a little bored . to lighten things up , one pretended to be poseidon by placing a seaweed garland on his head and then throwing it into the ocean . moments later , a dolphin surfaced with the seaweed crowning her head . sure , this could have been a coincidence , but it 's also entirely possible that the dolphin was mimicking the scientist . that 's because dolphins are one of the smartest animals species on earth . so exactly how smart are they ? like whales and porpoises , dolphins belong to the group of aquatic mammals known as cetaceans who comprise 86 different species , and share a common link with ungulates , or hoofed animals . originally land mammals , the first cetaceans entered the water about 55 million years ago as large predators with sharp teeth . then , a shift in ocean temperatures about 35 million years ago reduced the availability of prey . one group of cetaceans who survived this distruption , the odontocetes , wound up smaller with less sharp teeth , but also larger and more complex brains that allowed for complex social relationships , as well as echolocation to navigate and communicate . jump ahead to the present , and modern dolphins ' brains are so large that their encephalization quotient , their brain size compared to the average for their body size , is second only to humans . dolphins have evolved to survive through their ability to form complex social networks that hunt , ward off rivals , and raise offspring together . for example , one group of florida dolphins practices a sophisticated form of cooperation to hunt fish . a dolphin designated as `` the net-maker '' kicks up mud while another gives the signal for the other dolphins to simultaneously line up and catch the escaping fish . achieving a goal like this requires deliberate planning and cooperation , which , in turn , requires some form of intentional communication . dolphins pass down their communication methods and other skills from generation to generation . different dolphin populations exhibit variations in greetings , hunting strategies , and other behaviors . this sort of cultural transmission even extends to tool use . one group of bottlenose dolphins off the australian coast nicknamed the dolphin sponge club , has learned how to cover their rostrums with sponges when rooting in sharp corals , passing the knowledge from mother to daughter . dolphins have even demonstrated language comprehension . when taught a language based on whistles and hand gestures , they not only understood what the signals meant , but that their order had meaning : the difference between bringing the ball to the hoop and bringing the hoop to the ball . so they were able to process two of the main elements of human language : symbols that stand for objects and actions , and syntax that governs how they are structured . dolphins are also one of the few species who pass the mirror test . by recognizing themselves in mirrors , they indicate physical self-awareness , and research shows they can recognize not just their bodies , but also their own thoughts , a property called metacognition . in one study , dolphins comparing two sounds could indicate a same , different , or uncertain response . just like humans , they indicated uncertainty more often with difficult trials , suggesting they 're aware of what they know , and how confident they feel about that knowledge . but some of the most amazing things about dolphins are their senses of empathy , altruism , and attachment . the habit of helping injured individuals extends across the species barrier as evidenced by the many accounts of dolphins carrying humans to the surface to breathe . and like us , dolphins mourn their dead . when we consider all the evidence , we may wonder why humans still hunt dolphins for meat , endanger them through fishing and pollution , or imprison them to perform tricks . the ultimate question may not be whether dolphins are intelligent and complex beings , but whether humans can empathize with them enough to keep them safe and free .
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one group of bottlenose dolphins off the australian coast nicknamed the dolphin sponge club , has learned how to cover their rostrums with sponges when rooting in sharp corals , passing the knowledge from mother to daughter . dolphins have even demonstrated language comprehension . when taught a language based on whistles and hand gestures , they not only understood what the signals meant , but that their order had meaning : the difference between bringing the ball to the hoop and bringing the hoop to the ball .
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how would being compassionate and empathic be advantageous for dolphins ?
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imagine the brain could reboot , updating its withered and damaged cells with new , improved units . that may sound like science fiction , but it 's a potential reality scientists are investigating right now . will our brains one day be able to self-repair ? it 's well known that embryonic cells in our young developing brains produce new neurons , the microscopic units that make up the brain 's tissue . those newly generated neurons migrate to various parts of the developing brain , making it self-organize into different structures . but until recently , scientists thought cell production came to an abrupt halt soon after this initial growth , leading them to conclude that neurological diseases , like alzheimer 's and parkinson 's , and damaging events , like strokes , are irreversible . but a series of recent discoveries has revealed that adult brains actually do continue to produce new cells in at least three specialized locations . this process , known as neurogenesis , involves dedicated brain cells , called neural stem cells and progenitor cells , which manufacture new neurons or replace the old ones . the three regions where neurogenesis has been discovered are the dentate gyrus , associated with learning and memory , the subventricular zone , which may supply neurons to the olfactory bulb for communication between the nose and brain , and the striatum , which helps manage movement . scientists do n't yet have a good grasp on exactly what role neurogenesis plays in any of these regions , or why they have this ability that 's absent from the rest of the brain , but the mere presence of a mechanism to grown new neurons in the adult brain opens up an amazing possibility . could we harness that mechanism to get the brain to heal its scars similar to how new skin grows to patch up a wound , or a broken bone stitches itself back together ? so here 's where we stand . certain proteins and other small molecules that mimick those proteins can be administered to the brain to make neural stem cells and progenitor cells produce more neurons in those three locations . this technique still needs improvement so that the cells reproduce more efficiently and more cells survive . but research shows that progenitor cells from these areas can actually migrate to places where injury has occurred and give rise to new neurons there . and another promising possible approach is to transplant healthy human neural stem cells , which are cultured in a laboratory , to injured tissue , like we can do with skin . scientists are currently experimenting to determine whether transplanted donor cells can divide , differentiate and successfully give rise to new neurons in a damaged brain . they 've also discovered that we might be able to teach other kinds of brain cells , such as astrocytes or oligodendrocytes to behave like neural stem cells and start generating neurons , too . so , a couple of decades from now will our brains be able to self-repair ? we ca n't say for sure , but that has become one of the major goals of regenerative medicine . the human brain has 100 billion neurons and we 're still figuring out the wiring behind this huge biological motherboard . but everyday , research on neurogenesis brings us closer to that reboot switch .
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but a series of recent discoveries has revealed that adult brains actually do continue to produce new cells in at least three specialized locations . this process , known as neurogenesis , involves dedicated brain cells , called neural stem cells and progenitor cells , which manufacture new neurons or replace the old ones . the three regions where neurogenesis has been discovered are the dentate gyrus , associated with learning and memory , the subventricular zone , which may supply neurons to the olfactory bulb for communication between the nose and brain , and the striatum , which helps manage movement .
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what type of brain cell , other than neural stem cells , can be coaxed into generating neurons ?
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over 100,000 metric tons of caffeine are consumed around the world every year . that 's equivalent to the weight of 14 eiffel towers . most of this caffeine is consumed in coffee and tea , but it 's also ingested in some sodas , chocolate , caffeine pills , and even beverages labeled decaf . caffeine helps us feel alert , focused , happy , and energetic , even if we have n't had enough sleep . but it can also raise our blood pressure , and make us feel anxious . it 's the world most widely used drug . so how does it keep us awake ? caffeine evolved in plants where it serves a few purposes . in high doses , as it 's found in the leaves and seeds of certain species , it 's toxic to insects . but when they consume it in lower doses , as it 's found in nectar , it can actually help them remember and revisit flowers . in the human body , caffeine acts as a stimulant for the central nervous system . it keeps us awake by blocking one of the body 's key sleep-inducing molecules , a substance called adenosine . your body needs a constant supply of energy , which it gets by breaking down a high-energy molecule called atp . in the process , it liberates adenosine , atp 's chemical backbone . neurons in your brain have receptors perfectly tailored to this molecule . when adenosine docks to these receptors , it activates a cascade of biochemical reactions that cause neurons to fire more sluggishly and slow the release of important brain-signaling molecules . in other words , you get sleepy . caffeine is what 's called an adenosine receptor antagonist . that means it derails this process of slowing your neurons down by blocking adenosine receptors . caffeine and adenosine have a similar molecular structure , close enough that caffeine can wedge into the adenosine receptors , but not close enough to activate them . to summarize , adenosine inhibits your neurons . caffeine inhibits the inhibitor , so it stimulates you . caffeine can also boost positive feelings . in some neurons , the adenosine receptors are linked to receptors for another molecule called dopamine . one of dopamine 's roles in the brain is to promote feelings of pleasure . when adenosine docks in one of these paired receptors , that can make it harder for dopamine to fit in its own spot , interrupting its mood-lifting work . but when caffeine takes adenosine 's place , it does n't have the same effect , and dopamine can slide in . there 's evidence that caffeine 's effects on adenosine and dopamine receptors can have long-term benefits , too , reducing the risk of diseases like parkinson 's , alzheimer 's , and some types of cancer . caffeine can also ramp up the body 's ability to burn fat . in fact , some sports organizations think that caffeine gives athletes an unfair advantage and have placed limits on its consumption . from 1972 until 2004 , olympic athletes had to stay below a certain blood-caffeine concentration to compete . of course , not all of caffeine 's effects are so helpful . it might make you feel better and more alert , but it can also raise your heart rate and blood pressure , cause increased urination or diarrhea , and contribute to insomnia and anxiety . plus , the foods and beverages caffeine is found in have their own impacts on your body that have to be taken into account . your brain can adapt to regular consumption of caffeine . if your adenosine receptors are perpetually clogged , your body will manufacture extra ones . that way , even with caffeine around , adenosine can still do its job of signaling the brain to power down . that 's why you may find you need to consume more and more caffeine to feel as alert . there are more and more adenosine receptors to block . it 's also why if you suddenly quit caffeine , you may experience an unpleasant withdrawal . with plenty of receptors and no competition , adenosine can work overtime , causing symptoms like headaches , tiredness , and depressed moods . but in a few days , the extra adenosine receptors will disappear , your body will readjust , and you 'll feel just as alert as ever , even without an infusion of the world 's most popular stimulant .
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there are more and more adenosine receptors to block . it 's also why if you suddenly quit caffeine , you may experience an unpleasant withdrawal . with plenty of receptors and no competition , adenosine can work overtime , causing symptoms like headaches , tiredness , and depressed moods .
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if someone reduces caffeine consumption slowly , withdrawal symptoms won ’ t be evident . however , when someone stops caffeine use abruptly , they may experience headache , tiredness , and bad mood . why ?
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translator : andrea mcdonough reviewer : jessica ruby the healthy liver cell divides only when it 's stressed . the healthy hair cell divides frequently . and the cancer cell divides even more frequently and recklessly . `` the first draft that i saw was , like , four days before it was supposed to go online or something like that , and i had n't heard , you know i had n't heard , so , i was like , 'hey , guys , just wondering if you need me for anything ? ' you know ? and so she floods my inbox with emails , being like , 'yes , we actually need you for a bunch of stuff ! ' and it was great . like , when i first saw it , i mean , you immediately get the whole natural versus unnatural technique . '' `` not good for you ? '' `` right , yes , there you go , good for you and not good for you . seeing that , actually , was really cool because , i mean , i had no idea . writing the script , you have no idea what it 's going to turn out like in the end . but you get this , like , intuitive feel of 'okay , like , yeah , i get why this is a cancer cell , and i get why this is a healthy cell . ' and , actually , i showed it to , i showed an early draft to the professor with whom i was fact-checking the script who is a cancer researcher at mit , and he said that it was one of the best visualizations of cancer cells that he 'd ever seen . so , that was really cool to hear as well . '' `` when you get a script , do you make a storyboard or not ? '' `` i guess it depends on the method that we use to produce the piece because , for example , things that would definitely be character-heavy , like 'ladder of inference ' , we worked with a storyboard from beginning to end because we were dealing with character animation . and something like that is much different than stop-motion , for example . but , also , i mean biljana and i have also worked together for , like , nearly ten years or something absurd so we do n't need as much of a , you know , a piece of paper to tell us what to do , whereas , if i were working with someone new , then i would really want to work with a storyboard , but we kind of trust each other . '' `` so , you , like , finish ... ... each other 's sentences . '' `` we can try that again . '' `` no , we definitely should n't use that , it 's too cheesy . '' `` so , there was a part in the video where we had to represent how the cells reproduce and how chemotherapy affects it . and it became quite complicated for me to visualize , so i actually had to ask you to draw little doodles for me to actually explain that . how was that for you ? how was that experience ? '' `` i mean , it was pretty difficult for me to visualize , too , so , it was interesting . doing the storyboard actually helped me clarify in my head , like , how it actually works because when you have to explain something to someone else , with anything , obviously , you have to , like , really figure it out yourself . and , then , when you have to draw it , that requires you to take an extra level of abstraction and figure out , like , okay , like , what are the parts of this drawing that are really important ? what do i have to show clearly , and how do i show it ? and , so , doing that on a legal pad , which is , i think , how i ended up sending it to you guys , taking a picture of myself on camera , really helped , you know , me understand the crucial , and that 's the crucial part of why chemotherapy actually works . so , it was a really interesting experience . '' `` yeah , we actually started that on a , we had a whiteboard , and i was trying to figure out that process . i think we started at the beginning from cell division and multiplying and , you know , chemotherapy working . but then it became so crazy that i had to pull back and start from the end and go in a different direction . so , that became quite a challenge , too , figuring it out . '' `` we ended up using the visual that you gave us on the storyboard , which is really cool to have that sort of collaboration with the educator with whom you 're working . '' `` and i ca n't draw , so that should be noted . it was a very rough storyboard . '' `` it was good enough . '' `` good enough ! ''
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what do i have to show clearly , and how do i show it ? and , so , doing that on a legal pad , which is , i think , how i ended up sending it to you guys , taking a picture of myself on camera , really helped , you know , me understand the crucial , and that 's the crucial part of why chemotherapy actually works . so , it was a really interesting experience . ''
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do you think drawing an explanation helps understand a topic ? explain .
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humans know the surprising prick of a needle , the searing pain of a stubbed toe , and the throbbing of a toothache . we can identify many types of pain and have multiple ways of treating it . but what about other species ? how do the animals all around us experience pain ? it 's important that we find out . we keep animals as pets , they enrich our environment , we farm many species for food , and we use them in experiments to advance science and human health . animals are clearly important to us , so it 's equally important that we avoid causing them unnecessary pain . for animals that are similar to us , like mammals , it 's often obvious when they 're hurting . but there 's a lot that is n't obvious , like whether pain relievers that work on us also help them . and the more different an animal is from us , the harder it is to understand their experience . how do you tell whether a shrimp is in pain ? a snake ? a snail ? in vertebrates , including humans , pain can be split into two distinct processes . in first , nerves and the skin sense something harmful and communicate that information to the spinal cord . there , motor neurons activate movements that make us rapidly jerk away from the threat . this is the physical recognition of harm called nociception , and nearly all animals , even those with very simple nervous systems , experience it . without this ability , animals would be unable to avoid harm and their survival would be threatened . the second part is the conscious recognition of harm . in humans , this occurs when the sensory neurons in our skin make a second round of connections via the spinal cord to the brain . there , millions of neurons in multiple regions create the sensations of pain . for us , this is a very complex experience associated with emotions like fear , panic , and stress , which we can communicate to others . but it 's harder to know exactly how animals experience this part of the process because most them ca n't show us what they feel . however , we get clues from observing how animals behave . wild , hurt animals are known to nurse their wounds , make noises to show their distress , and become reclusive . in the lab , scientists have discovered that animals like chickens and rats will self-administer pain-reducing drugs if they 're hurting . animals also avoid situations where they 've been hurt before , which suggests awareness of threats . we 've reached the point that research has made us so sure that vertebrates recognize pain that it 's illegal in many countries to needlessly harm these animals . but what about other types of animals like invertebrates ? these animals are n't legally protected , partly because their behaviors are harder to read . we can make good guesses about some of them , like oysters , worms , and jellyfish . these are examples of animals that either lack a brain or have a very simple one . so an oyster may recoil when squirted with lemon juice , for instance , because of nociception . but with such a simple nervous system , it 's unlikely to experience the conscious part of pain . other invertebrate animals are more complicated , though , like the octopus , which has a sophisticated brain and is thought to be one of the most intelligent invertebrate animals . yet , in many countries , people continue the practice of eating live octopus . we also boil live crawfish , shrimp , and crabs even though we do n't really know how they 're affected either . this poses an ethical problem because we may be causing these animals unnecessary suffering . scientific experimentation , though controversial , gives us some clues . tests on hermit crabs show that they 'll leave an undesirable shell if they 're zapped with electricity but stay if it 's a good shell . and octopi that may originally curl up an injured arm to protect it will risk using it to catch prey . that suggests that these animals make value judgements around sensory input instead of just reacting reflexively to harm . meanwhile , crabs have been known to repeatedly rub a spot on their bodies where they 've received an electric shock . and even sea slugs flinch when they know they 're about to receive a noxious stimulus . that means they have some memory of physical sensations . we still have a lot to learn about animal pain . as our knowledge grows , it may one day allow us to live in a world where we do n't cause pain needlessly .
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these are examples of animals that either lack a brain or have a very simple one . so an oyster may recoil when squirted with lemon juice , for instance , because of nociception . but with such a simple nervous system , it 's unlikely to experience the conscious part of pain .
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nociception produces :
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translator : andrea mcdonough reviewer : jessica ruby we are constantly asked for our opinions . which team do you think will win the super bowl ? who wore it better on the red carpet ? who are you going to vote for for mayor ? public opinion polls are everywhere . important decision makers in american government have long relied on public opinion polls throughout elections and important legislation . the problem is public opinion is n't easy to track and , often times , is n't even right . in 1948 , the < i > chicago daily tribune < /i > ran a now famous headline : `` dewey defeats truman , '' they cried in big , bold , black and white letters . the problem is that dewey had n't defeated truman . the < i > tribune < /i > had relied on polls to come to their conclusion . whoops ! this happens all the time because public opinion polls are either inaccurate or misleading . so , why are they wrong ? and why do we keep using them ? first , let 's start with an important term : sample . a sample is the group of people that respond to questions during a public opinion poll . a poll 's quality rests largely on its sample , and a sample can be bad in a few key ways . it can be too small , too narrow , or the poll itself can be too difficult . polls that are too small are bad for obvious reasons . and while you ca n't possibly ask every single person in america for their opinion , the more people you ask , the more accurate your prediction . polls that are too narrow , that only ask a certain type of person a question , are bad , too . consider a poll about whether or not the potato is the best vegetable in america . if you only asked people in idaho , where the state food is the potato , chances are that you would get a much different answer than if you asked people in the state of new mexico , where the state vegetable is beans . getting the right kind of diversity in your sample means making sure that your sample has a range of ages , races , genders , and geographic regions , just to name a few . finally , polls that are too hard ca n't tell you much either . if you 're asking people for their opinions on things about which they have no prior knowledge , the results will be pointless . you 're better off shaking a magic 8 ball . it 's not just the people you 're asking that can cause bias , though . the person doing the asking is part of the problem , too . that 's called interviewer bias . interviewer bias is all about the effect that the person asking the questions has on the sample . humans generally do n't like confrontation . people worry that their answers may make them look bad . therefore , we find that people tend to give socially desirable responses , not necessarily their honest opinions , because they do n't want to come across as heartless , racist , or bigoted . and the way we word our questions matters too . when polls purposely sway the answers one way or the other , it 's called a push poll because it pushes people to answer a certain way . `` would you vote for candidate smith ? '' is a perfectly normal question . `` would you vote for candidate smith if you knew that he robs senior citizens ? '' is a push poll . so , if polls are open to all sorts of manipulation and inaccuracies , why are they still so prevalent ? despite their flaws , public opinion polls provide us with some sense of the thoughts and moods of large groups of people . they offer politicians the chance to pass legislation they think a majority of americans will support . they help fashionistas on tv know which star wore the dress better on the red carpet . finally , they make us , the people who get polled , feel as though our voice has been heard . so , next time you get a phone call asking your opinion , or if you see a poll online , take some time to think about who is asking and why they 're asking . then , take that poll , and its results , with a grain of salt or a potato .
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humans generally do n't like confrontation . people worry that their answers may make them look bad . therefore , we find that people tend to give socially desirable responses , not necessarily their honest opinions , because they do n't want to come across as heartless , racist , or bigoted . and the way we word our questions matters too .
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we find that people tend to give socially desirable answers in response to poll questions . that means that which of the following is most true ?
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in 1898 , marie and pierre curie discovered radium . claimed to have restorative properties , radium was added to toothpaste , medicine , water , and food . a glowing , luminous green , it was also used in beauty products and jewelry . it was n't until the mid-20th century we realized that radium 's harmful effects as a radioactive element outweighed its visual benefits . unfortunately , radium is n't the only pigment that historically seemed harmless or useful but turned out to be deadly . that lamentable distinction includes a trio of colors and pigments that we 've long used to decorate ourselves and the things we make : white , green , and orange . our story begins with white . as far back as the 4th century bce , the ancient greeks treated lead to make the brilliant white pigment we know today . the problem ? in humans , lead is directly absorbed into the body and distributed to the blood , soft tissues , and mineralized tissues . once in the nervous system , lead mimics and disrupts the normal functions of calcium , causing damages ranging from learning disabilities to high blood pressure . yet the practice of using this toxic pigment continued across time and cultures . lead white was the only practical choice for white oil or tempera paint until the 19th century . to make their paint , artists would grind a block of lead into powder , exposing highly toxic dust particles . the pigment 's liberal use resulted in what was known as painter 's colic , or what we 'd now call lead poisoning . artists who worked with lead complained of palseys , melancholy , coughing , enlarged retinas , and even blindness . but lead white 's density , opacity , and warm tone were irresistible to artists like vermeer , and later , the impressionists . its glow could n't be matched , and the pigment continued to be widely used until it was banned in the 1970s . as bad as all that sounds , white 's dangerous effects pale in comparison to another , more wide-spread pigment , green . two synthetic greens called scheele 's green and paris green were first introduced in the 18th century . they were far more vibrant and flashy than the relatively dull greens made from natural pigments , so they quickly became popular choices for paint as well as dye for textiles , wallpaper , soaps , cake decorations , toys , candy , and clothing . these green pigments were made from a compound called cupric hydrogen arsenic . in humans , exposure to arsenic can damage the way cells communicate and function . and high levels of arsenic have been directly linked to cancer and heart disease . as a result , 18th century fabric factory workers were often poisoned , and women in green dresses reportedly collapsed from exposure to arsenic on their skin . bed bugs were rumored not to live in green rooms , and it 's even been speculated that napoleon died from slow arsenic poisoning from sleeping in his green wallpapered bedroom . the intense toxicity of these green stayed under wraps until the arsenic recipe was published in 1822 . and a century later , it was repurposed as an insecticide . synthetic green was probably the most dangerous color in widespread use , but at least it did n't share radium 's property of radioactivity . another color did , though - orange . before world war ii , it was common for manufacturers of ceramic dinnerware to use uranium oxide in colored glazes . the compound produced brilliant reds and oranges , which were appealing attributes , if not for the radiation they emitted . of course , radiation was something we were unaware of until the late 1800s , let alone the associated cancer risks , which we discovered much later . during world war ii , the u.s. government confiscated all uranium for use in bomb development . however , the atomic energy commission relaxed these restrictions in 1959 , and depleted uranium returned to ceramics and glass factory floors . orange dishes made during the next decade may still have some hazardous qualities on their surfaces to this day . most notably , vintage fiestaware reads positive for radioactivity . and while the levels are low enough that they do n't officially pose a health risk if they 're on a shelf , the u.s. epa warns against eating food off of them . though we still occasionally run into issues with synthetic food dyes , our scientific understanding has helped us prune hazardous colors out of our lives .
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however , the atomic energy commission relaxed these restrictions in 1959 , and depleted uranium returned to ceramics and glass factory floors . orange dishes made during the next decade may still have some hazardous qualities on their surfaces to this day . most notably , vintage fiestaware reads positive for radioactivity . and while the levels are low enough that they do n't officially pose a health risk if they 're on a shelf , the u.s. epa warns against eating food off of them .
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hypothesize why dishes like vintage fiestaware coated with orange glazes are safe on a shelf , but not to eat off .
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cancer is like a car crash . your body typically regulates the speed at which your cells divide , but sometimes , cancer cuts the brake lines , and your cells divide too quickly , accumulating mutations that cause them to veer away from their original function , form dangerous tumors , and land you in the hospital . cancer is basically an inability of the body to control the speed at which cells divide . when cells divide too quickly , they can often accumulate mutations that cause them to ignore their original function in the body , forming tumors . in turn , these tumors may interfere with the natural processes of the body , such as digestion and respiration , potentially leading to death . typically , your body has a number of genetic mechanisms to control how fast your cells divide . one of these genes is brca1 , which stands for breast cancer susceptibility gene 1 . brca1 belongs to a class of genes called tumor suppressor genes . tumor suppressor genes are involved in regulating how fast a cell divides . normally , cell division follows an orderly process called the cell cycle , which is basically the life cycle of a cell . within the cell cycle is a series of checkpoints , where proteins , such as the one produced by brca1 , regulate how fast the cell may proceed . how does it do this ? brca1 helps repair some forms of mutation in your dna . if your dna is damaged , brca1 keeps the cell from dividing until the mutation is repaired . you have two copies of the brca1 gene in every cell of your body . one copy you inherited from mom , the other from dad . this redundancy is a good a thing because you only need one functioning brca1 gene in a cell to regulate the cell cycle . but it 's important to note that while these copies have a similar function they 're not necessarily the same . in fact , there are hundreds of variations , or alleles , of brca1 . some regulate the cell cycle more effectively than others . in other words , some people are born with better regulating and repair mechanisms than others . and in some cases , mutations may render brca1 ineffective . when this happens , cells with damaged dna are allowed to divide . as they divide , these cells may accumulate additional mutations . these mutations may cause the cell to become less specialized and stop performing its original function in the tissue . if this occurs , then there 's a greater chance they 'll develop into cancer cells . while we all have the gene , such as brca1 , that can cause cancer , it 's only when these genes fail at their function that problems develop . having an ineffective or mutated version of brca1 can increase your susceptibility to cancer , much like driving with bad brakes increases the risk of an accident .
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one of these genes is brca1 , which stands for breast cancer susceptibility gene 1 . brca1 belongs to a class of genes called tumor suppressor genes . tumor suppressor genes are involved in regulating how fast a cell divides . normally , cell division follows an orderly process called the cell cycle , which is basically the life cycle of a cell . within the cell cycle is a series of checkpoints , where proteins , such as the one produced by brca1 , regulate how fast the cell may proceed .
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another class of genes , called the proto-oncogenes , function to a similar manner to the gas pedal in a car . only a single copy of a proto-oncogene needs to be mutated in a cell for it to lose control of cell division . why would this be the case ?
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at about six o'clock in the morning on september 14 , 2015 , scientists witnessed something no human had ever seen : two black holes colliding . both about 30 times as massive as our sun , they had been orbiting each other for millions of years . as they got closer together , they circled each other faster and faster . finally , they collided and merged into a single , even bigger , black hole . a fraction of a second before their crash , they sent a vibration across the universe at the speed of light . and on earth , billions of years later , a detector called the laser interferometer gravitational wave observatory , or ligo for short , picked it up . the signal only lasted a fifth of a second and was the detector 's first observation of gravitational waves . what are these ripples in space ? the answer starts with gravity , the force that pulls any two objects together . that 's the case for everything in the observable universe . you 're pulling on the earth , the moon , the sun , and every single star , and they 're pulling on you . the more mass something has , the stronger its gravitational pull . the farther away the object , the lower its pull . if every mass has an effect on every other mass in the universe , no matter how small , then changes in gravity can tell us about what those objects are doing . fluctuations in the gravity coming from the universe are called gravitational waves . gravitational waves move out from what caused them , like ripples on a pond , getting smaller as they travel farther from their center . but what are they ripples on ? when einstein devised his theory of relativity , he imagined gravity as a curve in a surface called space-time . a mass in space creates a depression in space-time , and a ball rolling across a depression will curve like it 's being attracted to the other mass . the bigger the mass , the deeper the depression and the stronger the gravity . when the mass making the depression moves , that sends out ripples in space-time . these are gravitationl waves . what would a gravitational wave feel like ? if our bodies were sensitive enough to detect them , we 'd feel like we were being stretched sideways while being compressed vertically . and in the next instant , stretched up and down while being compressed horizontally , sideways , then up and down . this back and forth would happen over and over as the gravitational wave passed right through you . but this happens on such a minute scale that we ca n't feel any of it . so we 've built detectors that can feel it for us . that 's what the ligo detectors do . and they 're not the only ones . there are gravitational wave detectors spread across the world . these l-shaped instruments have long arms , whose exact length is measured with lasers . if the length changes , it could be because gravitational waves are stretching and compressing the arms . once the detectors feel a gravitational wave , scientists can extract information about the wave 's source . in a way , detectors like ligo are big gravitational wave radios . radio waves are traveling all around you , but you ca n't feel them or hear the music they carry . it takes the right kind of detector to extract the music . ligo detects a gravitational wave signal , which scientists then study for data about the object that generated it . they can derive information , like its mass and the shape of its orbit . we can also hear gravitational waves by playing their signals through speakers , just like the music a radio extracts from radio waves . so those two black holes colliding sounds like this . scientists call this slide whistle-like noise a chirp , and it 's the signature of any two objects orbiting into each other . the black hole collision was just one example of what gravitational waves can tell us . other high-energy astronomical events will leave gravitational echoes , too . the collapse of a star before it explodes in a supernova , or a very dense neutron stars colliding . every time we create a new tool to look at space , we discover something we did n't expect , something that might revolutionize our understanding of the universe . ligo 's no different . in the short time it 's been on , ligo 's already revealed surprises , like that black holes collide more often than we ever expected . it 's impossible to say , but exciting to imagine , what revelations may now be propagating across space towards our tiny blue planet and its new way of perceiving the universe .
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you 're pulling on the earth , the moon , the sun , and every single star , and they 're pulling on you . the more mass something has , the stronger its gravitational pull . the farther away the object , the lower its pull .
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which of the following is true about the pull of gravity ?
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i want to tell you all about a piece of american history that is so secret , that nobody has done anything about it for 167 years , until right now . and the way that we 're going to uncover this vestigial organ of america past is by asking this question : why ? as we all know -- ( laughter ) we are in the middle of another presidential election , hotly contested , as you can see . ( laughter ) but what you may not know is that american voter turnout ranks near the bottom of all countries in the entire world , 138th of 172 nations . this is the world 's most famous democracy . so ... why do we vote on tuesday ? does anybody know ? and as a matter of fact , michigan and arizona are voting today . here 's the answer : absolutely no good reason whatsoever . ( laughter ) i 'm not joking . you will not find the answer in the declaration of independence , nor will you find it in the constitution . it is just a stupid law from 1845 . ( laughter ) in 1845 , americans traveled by horse and buggy . as did i , evidently . it took a day to get to the county seat to vote , a day to get back , and you could n't travel on the sabbath , so , tuesday it was . i do n't often travel by horse and buggy , i would imagine most of you do n't , so when i found out about this , i was fascinated . i linked up with a group called , what else -- `` why tuesday ? '' to go and ask our nation 's most prominent elected leaders if they knew the answer to the question , `` why do we vote on tuesday ? '' ( video ) rick santorum : anybody knows ? ok , i 'm going to be stumped on this . anybody knows why we vote on tuesdays ? jacob soboroff : do you happen to know ? ron paul : on tuesdays ? js : the day after the first monday in november . rp : i do n't know how that originated . js : do you know why we do vote on tuesday ? newt gingrich : no . dick lugar : no , i do n't . ( laughter ) dianne feinstein : i do n't . darrell issa : no . john kerry : in truth , really , i 'm not sure why . js : ok , thanks very much . ( laughter ) js : these are people that live for election day , yet they do n't know why we vote on that very day . ( laughter ) chris rock said , `` they do n't want you to vote . if they did , we would n't vote on a tuesday in november . have you ever thrown a party on a tuesday ? ( laughter ) no , of course not . nobody would show up . '' ( laughter ) here 's the cool part . because we asked this question , `` why tuesday ? '' there is now this bill , the weekend voting act in the congress of the united states of america . it would move election day from tuesday to the weekend , so that -- duh -- more people can vote . ( applause ) it has only taken 167 years , but finally , we are on the verge of changing american history . thank you very much . ( applause ) thanks a lot . ( applause )
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( laughter ) here 's the cool part . because we asked this question , `` why tuesday ? '' there is now this bill , the weekend voting act in the congress of the united states of america . it would move election day from tuesday to the weekend , so that -- duh -- more people can vote . ( applause ) it has only taken 167 years , but finally , we are on the verge of changing american history .
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do you think that changing america ’ s voting date from tuesday to a weekend date will impact voter turnout ? how ? why or why not ?
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every second , one million tons of matter is blasted from the sun at the velocity of one million miles per hour , and it 's on a collision course with earth ! but do n't worry , this is n't the opening of a new michael bay movie . this is the journey of the polar lights . the northern and southern lights , also known as the aurora borealis and aurora australis , respectively , occur when high energy particles from the sun collide with neutral atoms in our atmosphere . the energy emitted from this crash produces a spectacle of light that mankind has marveled at for centuries . but the particles ' journey is n't just as simple as leaving the sun and arriving at earth . like any cross-country road trip , there 's a big detour and nobody asks for directions . let 's track this intergalactic voyage by focusing on three main points of their journey : leaving the sun , making a pit stop in the earth 's magnetic fields , and arriving at the atmosphere above our heads . the protons and electrons creating the northern lights depart from the sun 's corona . the corona is the outermost layer of the sun 's atmosphere and is one of the hottest regions . its intense heat causes the sun 's hydrogen and helium atoms to vibrate and shake off protons and electrons as if they were stripping off layers on a hot , sunny day . impatient and finally behind the wheel , these free protons and electrons move too fast to be contained by the sun 's gravity and group together as plasma , an electrically charged gas . they travel away from the sun as a constant gale of plasma , known as the solar wind . however , the earth prevents the solar wind from traveling straight into the planet by setting up a detour , the magnetosphere . the magnetosphere is formed by the earth 's magnetic currents and shields our planet from the solar winds by sending out the particles around the earth . their opportunity to continue the journey down to the atmosphere comes when the magnetosphere is overwhelmed by a new wave of travelers . this event is coronal mass ejection , and it occurs when the sun shoots out a massive ball of plasma into the solar wind . when one of these coronal mass ejections collides with earth , it overpowers the magnetosphere and creates a magnetic storm . the heavy storm stresses the magnetosphere until it suddenly snaps back , like and overstretched elastic band , flinging some of the detoured particles towards earth . the retracting band of the magnetic field drags them down to the aurora ovals , which are the locations of the northern and southern lights . after traveling 93 million miles across the galaxy , the sun 's particles finally produce their dazzling light show with the help of some friends . 20 to 200 miles above the surface , the electrons and protons meet up with oxygen and nitrogen atoms , and they sure are happy to see each other . the sun 's particles high five the atoms , giving their energy to the earth 's neutral oxygen and nitrogen atoms . when the atoms in the atmosphere are contacted by the particles , they get excited and emit photons . photons are small bursts of energy in the form of light . the colors that appear in the sky depend on the wavelength of the atom 's photon . excited oxygen atoms are responsible for the green and red colors , whereas excited nitrogen atoms produce blue and deep red hues . the collection of these interactions is what creates the northern and southern lights . the polar lights are best seen on clear nights in regions close to magnetic north and south poles . nighttime is ideal because the aurora is much dimmer than sunlight and can not be seen in daytime . remember to look up at the sky and read up on the sun 's energy patterns , specifically sunspots and solar flares , as these will be good guides for predicting the auroras .
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impatient and finally behind the wheel , these free protons and electrons move too fast to be contained by the sun 's gravity and group together as plasma , an electrically charged gas . they travel away from the sun as a constant gale of plasma , known as the solar wind . however , the earth prevents the solar wind from traveling straight into the planet by setting up a detour , the magnetosphere .
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what is a constant gale of plasma from the sun called ?
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translator : andrea mcdonough reviewer : bedirhan cinar fourth and nineteen , folks , they 've got ta have a play as time 's ticking away because they 've got to stay in this ball game , they 've got to win . they come out lined up in the empty set , three receivers to the right , two to the left . defense looks like they 're gon na to man up with no safety . this is the exact offensive match-up that they want : the best receiver lined up against the linebacker . quarterback steps back to receive the ball , five yards deep in the gun . he takes a snap , drops three steps , he plants his back foot , he 's looking for an opening . there 's a blitz coming off the edge ! he steps up to avoid the rush . he 's looking down field . he 's got the inside receiver making a cut . he 's got a step on the linebacker . quarterback has a beat on it . he lets the ball go , it 's in the air ! receiver is out in front of the defender . he 's got it beat ! he 's out in front , racing for the ball ! it 's coming down ! he cradles it at the fifteen ! he 's at the ten , five ! touchdown ! unbelievable play ! now , wait a minute . of course , it 's believable , it 's physics , specifically the differences between scalars and vectors . so , let 's just see that replay . `` quarterback steps back to receive the ball , five yards deep in the gun . '' stop . see , measurements are defined as two different quantities . scalars are measurements with only numbers , and vectors are measurements with direction . for example , when that quarterback takes the snap , he 's five yards away , but from where ? back from the line of scrimmage , so the five yards by itself is a scalar quantity . when you add a direction , like five yards deep , it becomes a vector quantity . five yards - scalar , five yards deep - vector . ok , go ahead . `` he takes a snap , drops three steps . he plants his back foot , he 's looking for an opening . there 's a blitz coming off the edge ! he steps up to avoid the rush . '' whoa ! here 's a difference between distance and displacement . distance is a measurement without identifying where you moved . it 's a scalar quantity . when the quarterback makes a three-step drop , he moves about three yards back . when he moves about another three yards forward , when he steps up into the pocket , so that quarterback moves a total distance of six yards . that 's a distance , that 's a scalar . now , displacement is a vector quantity , describing about how far out of place the object is . so the quarterback dropped back three yards and then moved back forward three yards , he 's in the exact same place where he started . so , his displacement is zero yards . distance - six yards , displacement - zero yards . so , let 's look at what happened next . `` quarterback has a beat on it , he let 's the ball go ! it 's in the air ! receiver is out in front of the defender . '' stop . so , here 's speed and velocity , but let 's just do one thing at a time . so , speed is measurement without direction , it 's a scalar quantity . velocity is a vector quantity . it is that object 's speed , but with a direction of motion . so the receiver accelerates away , gaining both speed and distance . this takes the receiver 5 seconds to run those 50 yards . so his average speed , in any given time , is 10 yards/second . the linebacker tries to keep up , but his overall speed is slower , he only goes 35 yards in those 5 seconds , so his average speed is only 7 yards/second . they 're both traveling in a forward direction , so their velocity is also positive . you ca n't go from resting to your peak speed immediately . you 've got to build up to it . this is acceleration . at first the linebacker can keep up with that receiver , but eventually the faster receiver pulls away . that 's acceleration , the change in speed over time . acceleration is a vector quantity . it describes a rate at which an object changes velocity . like velocity , acceleration is a vector . it happens in a direction . so let 's just look at that play just one more time . `` quarterback steps back to receive the ball , five yards deep in the gun . '' vector ! `` he takes a snap , drops three steps , he plants his back foot . he 's looking for an opening . there 's a blitz coming off the edge ! he steps up to avoid the rush . '' displacement ! `` he 's got the inside receiver making a cut . he 's got a step on the linebacker . the quarterback has a beat on it . he let 's the ball go ! it 's in the air ! receiver is out in front of the defender ! '' velocity ! `` he 's got it beat ! he 's out in front , racing for the ball ! it 's coming down ! he cradles it at the fifteen , he 's at the ten , five ! '' acceleration ! `` touchdown ! unbelievable play ! that was a great play as time expired , resulting in the touchdown and ultimately the win and pure effort . '' and pure science .
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so , speed is measurement without direction , it 's a scalar quantity . velocity is a vector quantity . it is that object 's speed , but with a direction of motion .
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to determine velocity , a vector quantity , you divide the displacement by the amount of time .
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so this is a very , very special sample of lutetium . again from the bottom end of the periodic table , the lanthanides , and you can see it ’ s a really quite beautiful metallic foil here . so lutetium is the last of the 4f lanthanide series and it ’ s also used for dating meteorites . and , it ’ s a very small sample . it weighs a few milligrams but it ’ s a very , very nice sample , stirred under an inert atmosphere so that we can control the chemistry , so it ’ s full of un-reactive argon so we can ’ t form the oxide . lutetium , although it might not be obvious to you , is named after a european capital city . lutetium is also used in radionucleotide treatment for cancers so it ’ s got a very useful role . and , in fact , it ’ s named after paris as lutetia was the roman name for paris , when it was a roman city , and therefore lutetium is one of the few elements that is named after a city . some of the other , rarer , are named after cities in sweden , but lutetium is the one that is most easily recognisable , at least by people like me , who had to learn latin when we were children . like thulium it is very expensive so we save it for special occasions . when we know that something will absolutely work for sure then we will try it with lutetium .
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again from the bottom end of the periodic table , the lanthanides , and you can see it ’ s a really quite beautiful metallic foil here . so lutetium is the last of the 4f lanthanide series and it ’ s also used for dating meteorites . and , it ’ s a very small sample .
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lutetium is the last of the lanthanides . what is its correct electronic configuration ?
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every spring , hundreds of adventure-seekers dream of climbing qomolangma , also known as mount everest . at base camp , they hunker down for months waiting for the chance to scale the mountain 's lofty , lethal peak . but why do people risk life and limb to climb everest ? is it the challenge ? the view ? the chance to touch the sky ? for many , the draw is everest 's status as the highest mountain on earth . there 's an important distinction to make here . mauna kea is actually the tallest from base to summit , but at 8850 meters above sea level , everest has the highest altitude on the planet . to understand how this towering formation was born , we have to peer deep into our planet 's crust , where continental plates collide . the earth 's surface is like an armadillo 's armor . pieces of crust constantly move over , under , and around each other . for such huge continental plates , the motion is relatively quick . they move two to four centimeters per year , about as fast as fingernails grow . when two plates collide , one pushes into or underneath the other , buckling at the margins , and causing what 's known as uplift to accomodate the extra crust . that 's how everest came about . 50 million years ago , the earth 's indian plate drifted north , bumped into the bigger eurasian plate , and the crust crumpled , creating huge uplift . mountain everest lies at the heart of this action , on the edge of the indian-eurasian collision zone . but mountains are shaped by forces other than uplift . as the land is pushed up , air masses are forced to rise as well . rising air cools , causing any water vapor within it to condense and form rain or snow . as that falls , it wears down the landscape , dissolving rocks or breaking them down in a process known as weathering . water moving downhill carries the weathered material and erodes the landscape , carving out deep valleys and jagged peaks . this balance between uplift and erosion gives a mountain its shape . but compare the celestial peaks of the himalayas to the comforting hills of appalachia . clearly , all mountains are not alike . that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast . the peaks grow tall with steep slopes . over time , however , gravity and water wear them down . eventually , erosion overtakes uplift , wearing down peaks faster than they 're pushed up . a third factor shapes mountains : climate . in subzero temperatures , some snowfall does n't completely melt away , instead slowly compacting until it becomes ice . that forms the snowline , which occurs at different heights around the planet depending on climate . at the freezing poles , the snowline is at sea level . near the equator , you have to climb five kilometers before it gets cold enough for ice to form . gathered ice starts flowing under its own immense weight forming a slow-moving frozen river known as a glacier , which grinds the rocks below . the steeper the mountains , the faster ice flows , and the quicker it carves the underlying rock . glaciers can erode landscapes swifter than rain and rivers . where glaciers cling to mountain peaks , they sand them down so fast , they lop the tops off like giant snowy buzzsaws . so then , how did the icy mount everest come to be so tall ? the cataclysmic continental clash from which it arose made it huge to begin with . secondly , the mountain lies near the tropics , so the snowline is high , and the glaciers relatively small , barely big enough to widdle it down . the mountain exists in a perfect storm of conditions that maintain its impressive stature . but that wo n't always be the case . we live in a changing world where the continental plates , earth 's climate , and the planet 's erosive power might one day conspire to cut mount everest down to size . for now , at least , it remains legendary in the minds of hikers , adventurers , and dreamers alike .
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in subzero temperatures , some snowfall does n't completely melt away , instead slowly compacting until it becomes ice . that forms the snowline , which occurs at different heights around the planet depending on climate . at the freezing poles , the snowline is at sea level .
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snowline occurs at different heights around the planet due to differences in :
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energy is all around us , a physical quantity that follows precise natural laws . our universe has a finite amount of it ; it 's neither created nor destroyed but can take different forms , such as kinetic or potential energy , with different properties and formulas to remember . for instance , an led desk lamp 's 6 watt bulb transfers 6 joules of light energy per second . but let 's jump back up into space to look at our planet , its systems , and their energy flow . earth 's physical systems include the atmosphere , hydrosphere , lithosphere , and biosphere . energy moves in and out of these systems , and during any energy transfer between them , some is lost to the surroundings , as heat , light , sound , vibration , or movement . our planet 's energy comes from internal and external sources . geothermal energy from radioactive isotopes and rotational energy from the spinning of the earth are internal sources of energy , while the sun is the major external source , driving certain systems , like our weather and climate . sunlight warms the surface and atmosphere in varying amounts , and this causes convection , producing winds and influencing ocean currents . infrared radiation , radiating out from the warmed surface of the earth , gets trapped by greenhouse gases and further affects the energy flow . the sun is also the major source of energy for organisms . plants , algae , and cyanobacteria use sunlight to produce organic matter from carbon dioxide and water , powering the biosphere 's food chains . we release this food energy using chemical reactions , like combustion and respiration . at each level in a food chain , some energy is stored in newly made chemical structures , but most is lost to the surroundings , as heat , like your body heat , released by your digestion of food . now , as plants are eaten by primary consumers , only about 10 % of their total energy is passed on to the next level . since energy can only flow in one direction in a food chain , from producers on to consumers and decomposers , an organism that eats lower on the food chain , is more efficient than one higher up . so eating producers is the most efficient level at which an animal can get its energy , but without continual input of energy to those producers , mostly from sunlight , life on earth as we know it would cease to exist . we humans , of course , spend our energy doing a lot of things besides eating . we travel , we build , we power all sorts of technology . to do all this , we use sources like fossil fuels : coal , oil , and natural gas , which contain energy that plants captured from sunlight long ago and stored in the form of carbon . when we burn fossil fuels in power plants , we release this stored energy to generate electricity . to generate electricity , heat from burning fossil fuels is used to power turbines that rotate magnets , which , in turn , create magnetic field changes relative to a coil of wire , causing electrons to be induced to flow in the wire . modern civilization depends on our ability to keep powering that flow of electrons . fortunately , we are n't limited to burning non-renewable fossil fuels to generate electricity . electrons can also be induced to flow by direct interaction with light particles , which is how a solar cell operates . other renewable energy sources , such as wind , water , geothermal , and biofuels can also be used to generate electricity . global demand for energy is increasing , but the planet has limited energy resources to access through a complex energy infrastructure . as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important . access to energy impacts health , education , political power , and socioeconomic status . if we improve our energy efficiency , we can use our natural resources more responsibly and improve quality of life for everyone .
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as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important . access to energy impacts health , education , political power , and socioeconomic status . if we improve our energy efficiency , we can use our natural resources more responsibly and improve quality of life for everyone .
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energy choice impacts the quality of an individual and society by ________ .
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in the past few months , i 've been traveling for weeks at a time with only one suitcase of clothes . one day , i was invited to an important event , and i wanted to wear something special and new for it . so i looked through my suitcase and i could n't find anything to wear . i was lucky to be at the technology conference on that day , and i had access to 3d printers . so i quickly designed a skirt on my computer , and i loaded the file on the printer . it just printed the pieces overnight . the next morning , i just took all the pieces , assembled them together in my hotel room , and this is actually the skirt that i 'm wearing right now . ( applause ) so it was n't the first time that i printed clothes . for my senior collection at fashion design school , i decided to try and 3d print an entire fashion collection from my home . the problem was that i barely knew anything about 3d printing , and i had only nine months to figure out how to print five fashionable looks . i always felt most creative when i worked from home . i loved experimenting with new materials , and i always tried to develop new techniques to make the most unique textiles for my fashion projects . i loved going to old factories and weird stores in search of leftovers of strange powders and weird materials , and then bring them home to experiment on . as you can probably imagine , my roommates did n't like that at all . ( laughter ) so i decided to move on to working with big machines , ones that did n't fit in my living room . i love the exact and the custom work i can do with all kinds of fashion technologies , like knitting machines and laser cutting and silk printing . one summer break , i came here to new york for an internship at a fashion house in chinatown . we worked on two incredible dresses that were 3d printed . they were amazing -- like you can see here . but i had a few issues with them . they were made from hard plastics and that 's why they were very breakable . the models could n't sit in them , and they even got scratched from the plastics under their arms . with 3d printing , the designers had so much freedom to make the dresses look exactly like they wanted , but still , they were very dependent on big and expensive industrial printers that were located in a lab far from their studio . later that year , a friend gave me a 3d printed necklace , printed using a home printer . i knew that these printers were much cheaper and much more accessible than the ones we used at my internship . so i looked at the necklace , and then i thought , `` if i can print a necklace from home , why not print my clothes from home , too ? '' i really liked the idea that i would n't have to go to the market and pick fabrics that someone else chose to sell -- i could just design them and print them directly from home . i found a small makerspace , where i learned everything i know about 3d printing . right away , they literally gave me the key to the lab , so i could experiment into the night , every night . the main challenge was to find the right filament for printing clothes with . so what is a filament ? filament is the material you feed the printer with . and i spent a month or so experimenting with pla , which is a hard and scratchy , breakable material . the breakthrough came when i was introduced to filaflex , which is a new kind of filament . it 's strong , yet very flexible . and with it , i was able to print the first garment , the red jacket that had the word `` liberté '' -- `` freedom '' in french -- embedded into it . i chose this word because i felt so empowered and free when i could just design a garment from my home and then print it by myself . and actually , you can easily download this jacket , and easily change the word to something else . for example , your name or your sweetheart 's name . ( laughter ) so the printer plates are small , so i had to piece the garment together , just like a puzzle . and i wanted to solve another challenge . i wanted to print textiles that i would use just like regular fabrics . that 's when i found an open-source file from an architect who designed a pattern that i love . and with it , i was able to print a beautiful textile that i would use just like a regular fabric . and it actually even looks a little bit like lace . so i took his file and i modified it , and changed it , played with it -- many kinds of versions out of it . and i needed to print another 1,500 more hours to complete printing my collection . so i brought six printers to my home and just printed 24-7 . and this is actually a really slow process , but let 's remember the internet was significantly slower 20 years ago , so 3d printing will also accelerate and in no time you 'll be able to print a t-shirt in your home in just a couple of hours , or even minutes . so you guys , you want to see what it looks like ? audience : yeah ! ( applause ) danit peleg : rebecca is wearing one of my five outfits . almost everything here she 's wearing , i printed from my home . even her shoes are printed . audience : wow ! audience : cool ! ( applause ) danit peleg : thank you , rebecca . ( to audience ) thank you , guys . so i think in the future , materials will evolve , and they will look and feel like fabrics we know today , like cotton or silk . imagine personalized clothes that fit exactly to your measurements . music was once a very physical thing . you would have to go to the record shop and buy cds , but now you can just download the music -- digital music -- directly to your phone . fashion is also a very physical thing . and i wonder what our world will look like when our clothes will be digital , just like this skirt is . thank you so much . ( applause ) [ thank you ] ( applause )
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the main challenge was to find the right filament for printing clothes with . so what is a filament ? filament is the material you feed the printer with .
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what is filament ?
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we 've decided to make a new video about aluminium because it 's a long time over five years since we made the first one and ... we did n't say very much . aluminium is a surprisingly abundand element . if you look at this periodic table here , where the area of the different elements gives you a rough idea of the abundance you can see that aluminium is one of the most abundant metals up there with sodium , magnesium and calcium . more aluminum than potassium ; about the same or perhaps even more than iron . we 're never going to run out of aluminium . the problem with aluminium is that you do n't find aluminium metal in nature as a metal . it 's always tied up with other compounds ; mostly with oxygen , in clays . you know what clays are , the sort of muddy stuff that you get stuck on your shoes when it 's raining . to get the aluminium out of the clay , that is , to break the aluminium/oxygen bonds , which are very strong ; requires a lot of energy , which comes from electricity . so , making aluminium is very energy intensive . that 's why people like to recycle aluminium because once you 've got it , it 's worth preserving ; but it 's fantastically important because aluminium is a very light metal . and it 's often used as an alloy because the aluminium alloys are stronger than the aluminium itself , so , if you 're using it for aircraft or some other use like that where you want to combine lightness with strength then the stronger you can make it , the better . but when it was first made , in the 19th century , isolated as a metal it was terrifically valuable and there are stories of the french emperor serving his honored guests with aluminium plates or aluminium cutlery while the less important people had silver or gold ; but those times have passed and now you can get cupcakes and things like that surrounded by foil of aluminium . aluminium is a very good metal for making things because it has a very thin coating of aluminium oxide on the surface which prevents it [ from ] reacting with things . but as soon as that coating goes it becomes very reactive . alfred worden : hadley base , do you read houston ? david scott : yeah . now , 5 by , joe . worden : okay . worden : and i guess we 're standing by for your high-gain alignment per the checklist . scott : okay , stand by . you may have seen our video where we put copper chloride in one of these cupcake holders ... [ first of all i 'm going to dissolve some up and make a fairly concentrated solution . i 'm going to place this here . ] ... and what came out was this , or rather the copper chloride came out through the hole . [ it starts boiling really quite nicely . now , imagine i was doing this for my children who were quite small at that time , and ... voosh ! ] and the aluminium was completely dissolved up forming aluminium chloride and copper metal . in my own research , aluminium is quite important ; quite a lot of our equipment uses aluminium . not so much for the high pressure tubing that we use because quite a lot of my reaserch involves high pressures but we use it for the metal blocks that we put round the tubing so that we can heat it up . aluminium has a good electrical conductivity , and it 's also easy to machine . this is a piece of equipment here where we have a tube going down the middle . you can see the diameter of the tube here . around it is an aluminium block and an electrical heater . now , this particular case there was an accident , or a mishap , because the thermocouple that was controlling the temperature of this fell out . so , the heater got hotter and hotter , and eventually , the aluminium melted and poured down here . and i think this is really beautiful . well , fortunately , i was not in the lab or i would 've got very angry with my students but i think when it happened it was quite exciting ; this would have been glowing almost red because the melting point of aluminium is around 500 degrees centigrade . but then once it formed originally it was very shiny but quickly , it again developed the surface layer of aluminium oxide . if you have fine particles of aluminium and blow them into a flame ... ... then they will burn quite spectacularly and you form aluminium oxide . now , on the face of it , aluminium oxide sounds a rather boring compound but it 's really very useful and we use it quite a lot in our research in all sorts of different ways . it looks like a white powder . not very exciting . but in our group this aluminium oxide has been a fantastic catalyst all sorts of reactions that we did n't expect have gone with this material . my students keep it in a bottle almost like a magic catalyst and i 've only been given a little to show you . it acts as a solid acid which can be used at very high temperature and will get various acid-catalyzed reactions of organic compounds . it will make ethers , we have made various alkynes and a whole series of different compounds and my students still use it very much . if you melt the aluminium oxide , which we ca n't do here but can be done industrially , you can make single crystals which are transparent like glass and then you can grow a single crystal tube , like this one , which because it 's a single crystal , it 's terrifically strong . it 's the defects that make something weak and so if you have just one crystal there are no defects and so it 's very strong . so you can put a very high pressure inside this tube without it blowing up . brady : but you could make that tube out of metal , professor . professor : but , if you have a metal then you ca n't see what 's going on inside , and we 're using these tubes for photochemical reactions . so , we take a light like this , and shine it on the chemicals going through the tube under high pressure and we can convert one chemical into another . we can do this very efficiently because the light is absorbed by the molecules that we want to react and so we dont waste the energy on everything else . and using leds , which are a very efficient light source , you can get a process that is very energy efficient and it all depends on having this sapphire tube . this is synthetic sapphire . the real sapphire , the gems , have impurities in them , of other metals , which give them the nice colors , particularly the blue . princess kate has a blue sapphire ring which belonged to her husband 's mother , princess di , before her . and so , these are very valuable ones . but synthetic sapphire is also expensive but not in the same class as a natural gem . brady : what can nature do that the guys at the sapphire factory ca n't do ? professor : nature has time . the people who grow this will take hours or days or perhaps weeks to grow it . nature can spend thousands or millions of years growing a particular gem and therefore they can heat it up and cool it down in natural surroundings , in volcanoes ... or whatever far more slowly than people can afford to do industrially . there 's a lot of argument whether you should call it aluminum or aluminium now , there is n't a totally correct one because both forms are acceptable . but , all or nearly all chemists use aluminium because it 's very important to use a standardized nomenclature right across the world . and i think aluminium sounds nicer . student : hi professor , my question is is it aluminum or aluminium ? 'cause i want to know what to call my aluminium model . apparantly , there was a decision in 1990 by iupac the international union of pure and applied chemistry that it should definately be called a l u m i n i u m but then they relented three years later and said you could use aluminum as well . but if you 're a serious chemist you really need to say aluminium , because otherwise people wo n't find your papers , your publications , when they search because they 'll almost certainly put an `` i '' ' in the name . aluminium is frequently used or used [ to be ] frequently used kkfor sauce pans , for cooking in because it 's easy to make , easy to machine and particularly when people used electric stoves it was easy to make a flat bottom so that you got good contact between the electric element and the sauce pan . the problem with aluminium sauce pans is that if you 're cooking some fairly acidic food , for example boiling lemons or rhubarb something like that which is quite acidic you can dissolve some of the aluminium and people got quite worried about getting aluminium in their food . also , if you cook red cabbage , which is an indicator ; blue for alkali , red for acid , then if you boil it in an aluminium sauce pan it goes blue . and earlier in my carreer i used a red cabbage together with a white one to make a union jack , a u.k. flag with a mixture of red and blue-red cabbage and the white from the white cabbage . unfortionately , i 've lost the photo ; brady is very cross with me . but it was quite fun cooking it in the kitchen . i did it once myself , but it was such a lot of work that the second time a got one of my students to do it .
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but , all or nearly all chemists use aluminium because it 's very important to use a standardized nomenclature right across the world . and i think aluminium sounds nicer . student : hi professor , my question is is it aluminum or aluminium ?
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why do you think the aluminium powder , used by neil , burned in a flame ; while the lump of aluminium , melted by the professor ’ s students , did not burn ?
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translator : jessica ruby reviewer : caroline cristal russia , with the largest territory in the world , has roughly the same total population as nigeria , a country 1/16 its size . but this similarity wo n't last long . one of the populations is rapidly growing , while the other is slowly declining . what can this tell us about the two countries ? population statistics are some of the most important data social scientists and policy experts have to work with . but understanding a country 's situation and making accurate predictions requires knowing not just the total size of the population but its internal characteristics , such as age and gender distribution . so , how can we keep track of all that data in a way that makes it easy to comprehend ? complex data is more easily interpreted through visualization , and one of the ways that demographers represent the internal distribution of a population is the population pyramid . here , the data is divided by gender with females on one side and males on the other . the population numbers are shown for each five-year age interval , starting from 0-4 and continuing up to 100 and up . these intervals are grouped together into pre-reproductive ( 0-14 ) , reproductive ( 15-44 ) , and post-reproductive years ( 45 and up ) . such a population pyramid can be a powerful predictor of future population trends . for example , rwanda 's population pyramid shows it to be a fast-growing country , with most of the population being in the youngest age groups at the bottom of the pyramid . the number will grow rapidly in the coming years . as today 's children reach their reproductive years and have children of their own , the total population is almost certain to double within the next few decades . for our second example , let 's look at canada , where most of the population is clustered around the middle of the graph . because there are less people in the pre-reproductive age groups than there are in the reproductive ones , the population will grow more slowly , as the number of people reaching their reproductive years decreases . finally , let 's look at japan . because the majority of its population is in its post-reproductive years and the number of people is smaller at each younger interval , this means that at current rates of reproduction the population will begin to decline as fewer and fewer people reach reproductive age . comparing these three population pyramids side by side shows us three different stages in a demographic transition , as a country moves from a pre-industrial society to one with an industrial or post-industrial economy . countries that have only recently begun the process of industrialization typically see an increase in life expectancy and a fall in child mortality rates as a result of improvements in medicine , sanitation , and food supply . while birth rates remain constant , leading to a population boom . developing countries that are farther along in the industrialization process begin to see a fall in birth rates , due to factors such as increased education and opportunities for women outside of child-rearing and a move from rural to urban living that makes having large families less economically advantageous . finally , countries in advanced stages of industrialization reach a point where both birth and death rates are low , and the population remains stable or even begins to decline . now , let 's take a look at the projected population pyramids for the same three countries in 2050 . what do these tell us about the expected changes in each country 's population , and what kinds of factors can alter the shape of these future pyramids ? a population pyramid can be useful not only as a predictor of a country 's future but as a record of its past . russia 's population pyramid still bears the scars of world war ii , which explains both the fewer numbers of elderly men compared to elderly women and the relatively sudden population increase as soldiers returned from the war and normal life resumed . china 's population pyramid reflects the establishment of the one child policy 35 years before , which prevented a population boom such as that of rwanda but also led to sex-selective abortions , resulting in more male children than female children . finally , the pyramid for the united states shows the baby boom that followed world war ii . as you can see , population pyramids tell us far more about a country than just a set of numbers , by showing both where it 's been and where it 's headed within a single image . and in today 's increasingly interconnected world , facing issues such as food shortages , ecological threats , and economic disparities , it is increasingly important for both scientists and policy makers to have a rich and complex understanding of populations and the factors affecting them .
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finally , countries in advanced stages of industrialization reach a point where both birth and death rates are low , and the population remains stable or even begins to decline . now , let 's take a look at the projected population pyramids for the same three countries in 2050 . what do these tell us about the expected changes in each country 's population , and what kinds of factors can alter the shape of these future pyramids ?
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which continent would have the most fast growth pyramids
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mysteries of vernacular : zero , a number that indicates an absence of units . in order to understand the genesis of the word zero , we must begin with the very origins of counting . the earliest known archaeological evidence of counting dates back approximately 37,000 years and is merely a series of notches in bone . it was n't until around 2500 b.c . that the first written number system began to take form in mesopotamia , using the units one , ten , and sixty . fast forward another three millennia to seventh century india where mathematicians used a single dot to distinguish between numbers like 25 , 205 , and 250 . employed as both a placeholder and a number , this all-powerful dot eventually morphed into the symbol we know today . the word zero comes from the arabic safira , whose literal translation is empty . passing through italian as zefiro , zero came into english in the seventeenth century . a second descendant of the arabic root was adopted into english through old french as the word cipher . originally sharing the meaning empty with zero , cipher later came to describe a code , as early codes often used complicated substitutions between letters and numbers . from this shared empty origin , zero continues to represent the number that represents nothing .
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employed as both a placeholder and a number , this all-powerful dot eventually morphed into the symbol we know today . the word zero comes from the arabic safira , whose literal translation is empty . passing through italian as zefiro , zero came into english in the seventeenth century . a second descendant of the arabic root was adopted into english through old french as the word cipher .
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what kind of math can you do without zero ?
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i was walking my mountain the other day , and i was feeling really at home with the forest . and i was so grateful to it for showing me that forests are built on relationships which form networks , like these beautiful river networks . and i thought , `` wow , forests are just like human families . '' and i was so taken by the beauty of this idea that i fell and i crashed down on the ground , and i hit my head on this new stump . and i was so angry ! then , i was so heartbroken because there was a whole family of trees cut down . thing is , where i 'm from in western canada , there 's clearcuts like this hidden everywhere , and it was n't until google earth starting sending images , like this , that we realized the whole world was wiping its noses on our old-growth forests . did you know that deforestation like this around the world causes more greenhouse gas emissions than all the trains , planes and automobiles combined ? yeah , i 'm really upset about this , but i 'm also really hopeful because i 've also discovered in my research that forest networks are organized in the same way as our own neural networks and our social networks . and i believe that if we can learn to integrate these into a whole that we can change this dangerous pathway of global warming because i believe we are wired for healing . so , here 's the science : the most ancient of these networks is this below-ground fungal network , or mushroom network . and it evolved over a billion years ago to allow organisms to migrate from the ocean onto the land . and eventually , they got together with plants in this symbiosis . and this allowed plants to photosynthesize , pulling co2 , which is our biggest greenhouse gas , out of the atmosphere and giving off oxygen , which allows us to breathe and actually allowed humans to eventually evolve . now , we call this symbiosis a mycorrhiza , myco for fungus , rrhiza for root . so , the fungus and root get together , and they trade for mutual benefit . now , all trees in all forests all over the world depend on these mycorrhizas for their very survival . they ca n't live without them . and the way it works is that a seed falls on the forest floor , it germinates , it sends a root down into the soil , and it starts sending out chemical signals to the fungi to grow towards the root . and the fungus communicates back with its own signals , and it says to the root , 'you need to grow towards me and branch and soften . ' and so by this communication , they grow together into this magical symbiosis . and the way that symbiosis works is the plant takes its hard-earned carbon from photosynthesis and brings it to the fungus because the fungus ca n't photosynthesize . and the fungus takes nutrients and water it gathers from the soil , where plant roots ca n't grow , and they give it to the plant . and so they 're both benefiting in this cooperation . now , as the fungus grows through the soil , it starts linking plant and plant and tree and tree together until the whole forest is linked together . did you know that a single tree can be literally linked up to hundreds of other trees as far as the eye can see ? and as you 're walking through the forest , what you see , the trees , the roots , the mushrooms , are just the tip of the iceberg . under a single footstep , there are 300 miles of fungal cells stacked end on end moving stuff around . and if you could look down into the ground , it would be like this super highway with cars going everywhere . now , all networks are made of nodes and links . in forests , those nodes would be trees and the links fungi . it 's kind of like in your facebook network , where nodes would be friends and links would be your friendships . now , we all know that some of those nodes , or friends , are busier than others , like that friend who is always sending out group messages . well , it 's the same in forests , and these nodes in forests , we call them hubs , they 're the big trees in the forests with roots going everywhere . now , we also have learned that the systems organized around these hubs , these big old trees , so in forests , that 's where the regeneration occurs . in your facebook network , that might be how parties are organized , around that hub that 's always sending out the group messages . we call those hubs in forests mother trees ; they 're the big old trees in the forest . and they fix the carbon in their leaves , and they send it down through their massive trunks and into the networks all around them that are linked up to all the other trees and seedlings , the young ones , and they start sending that carbon everywhere . the more those seedlings are stressed out , maybe from drought or shade , the more the mother tree sends to them . it 's kind of like in your families , where if you 're kind of stressed out , mom and dad kick in and help you out a bit more , right ? well , it 's the same in forests . the other thing that we 've recently discovered is that mother trees will preferentially send more signals to her own kids , her own children . and then , this way she helps them do better , and then they survive more , and then they can pass their genes on to future generations . so , how natural selection works . now , the way these forests are organized makes them both resilient and vulnerable . they 're resilient because there 's many mother trees , and there 's many fungal species linking them together . and that network is really hard to break . it 's pretty darn tough . but of course , we humans have figured out how to do that . and what we do is we take out the mother trees . and maybe taking one out wo n't make much difference but when you take more and more and more and clearcut and more and more and more that it can cause the system to collapse and fall down , like dominoes . and we can cross tipping points and cause more forest death and more global warming , and we 're doing that . so what we do , our choices we make , can lead us towards global heatlh or global sickness . we do have choices . and i 'm going to leave you with four ideas that i think are worth spreading . first one : to love the forest you have to go spend time in it . go be in the forest , connect with it . and then you 'll fight hard enough to protect them . second : learn how they work . learn how those networks link things together in organized forests . and to do that , you got ta go out there take risks , make mistakes . third : protect forests . they need you to do that because they ca n't do it themselves . they 're stuck in one spot . they ca n't run away from humans , and they ca n't run away from global warming . they need you . and finally , and most importantly , use your own very clever , brilliant , neural and social networks to create amazing messages , and spread the word that forests are worth saving because you 're worth saving , and i believe that together we 're all wired for healing .
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and to do that , you got ta go out there take risks , make mistakes . third : protect forests . they need you to do that because they ca n't do it themselves .
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how humans treat forests will have an important influence on how well we cope with climate change . what can you do to help people help forests ?
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have you ever noticed something swimming in your field of vision ? it may look like a tiny worm or a transparent blob , and whenever you try to get a closer look , it disappears , only to reappear as soon as you shift your glance . but do n't go rinsing out your eyes ! what you are seeing is a common phenomenon known as a floater . the scientific name for these objects is muscae volitantes , latin for `` flying flies , '' and true to their name , they can be somewhat annoying . but they 're not actually bugs or any kind of external objects at all . rather , they exist inside your eyeball . floaters may seem to be alive , since they move and change shape , but they are not alive . floaters are tiny objects that cast shadows on the retina , the light-sensitive tissue at the back of your eye . they might be bits of tissue , red blood cells , or clumps of protein . and because they 're suspended within the vitreous humor , the gel-like liquid that fills the inside of your eye , floaters drift along with your eye movements , and seem to bounce a little when your eye stops . floaters may be only barely distinguishable most of the time . they become more visible the closer they are to the retina , just as holding your hand closer to a table with an overhead light will result in a more sharply defined shadow . and floaters are particularly noticeable when you are looking at a uniform bright surface , like a blank computer screen , snow , or a clear sky , where the consistency of the background makes them easier to distinguish . the brighter the light is , the more your pupil contracts . this has an effect similar to replacing a large diffuse light fixture with a single overhead light bulb , which also makes the shadow appear clearer . there is another visual phenomenon that looks similar to floaters but is in fact unrelated . if you 've seen tiny dots of light darting about when looking at a bright blue sky , you 've experienced what is known as the blue field entoptic phenomenon . in some ways , this is the opposite of seeing floaters . here , you are not seeing shadows but little moving windows letting light through to your retina . the windows are actually caused by white blood cells moving through the capillaries along your retina 's surface . these leukocytes can be so large that they nearly fill a capillary causing a plasma space to open up in front of them . because the space and the white blood cells are both more transparent to blue light than the red blood cells normally present in capillaries , we see a moving dot of light wherever this happens , following the paths of your capillaries and moving in time with your pulse . under ideal viewing conditions , you might even see what looks like a dark tail following the dot . this is the red blood cells that have bunched up behind the leukocyte . some science museums have an exhibit which consists of a screen of blue light , allowing you to see these blue sky sprites much more clearly than you normally would . while everybody 's eyes experience these sort of effects , the number and type vary greatly . in the case of floaters , they often go unnoticed , as our brain learns to ignore them . however , abnormally numerous or large floaters that interfere with vision may be a sign of a more serious condition , requiring immediate medical treatment . but the majority of the time entoptic phenomena , such as floaters and blue sky sprites , are just a gentle reminder that what we think we see depends just as much on our biology and minds as it does on the external world .
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and because they 're suspended within the vitreous humor , the gel-like liquid that fills the inside of your eye , floaters drift along with your eye movements , and seem to bounce a little when your eye stops . floaters may be only barely distinguishable most of the time . they become more visible the closer they are to the retina , just as holding your hand closer to a table with an overhead light will result in a more sharply defined shadow .
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floaters are more visible :
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after the french revolution erupted in 1789 , europe was thrown into chaos . neighboring countries ' monarchs feared they would share the fate of louis xvi , and attacked the new republic , while at home , extremism and mistrust between factions lead to bloodshed . in the midst of all this conflict , a powerful figure emerged to take charge of france . but did he save the revolution or destroy it ? `` order , order , who 's the defendant today ? i do n't see anyone . '' `` your honor , this is napoléon bonaparte , the tyrant who invaded nearly all of europe to compensate for his personal stature-based insecurities . '' `` actually , napoléon was at least average height for his time . the idea that he was short comes only from british wartime propaganda . and he was no tyrant . he was safeguarding the young republic from being crushed by the european monarchies . '' `` by overthrowing its government and seizing power himself ? '' `` your honor , as a young and successful military officer , napoléon fully supported the french revolution , and its ideals of liberty , equality , and fraternity . but the revolutionaries were incapable of real leadership . robespierre and the jacobins who first came to power unleashed a reign of terror on the population , with their anti-catholic extremism and nonstop executions of everyone who disagreed with them . and the directory that replaced them was an unstable and incompetent oligarchy . they needed a strong leader who could govern wisely and justly . '' `` so , france went through that whole revolution just to end up with another all-powerful ruler ? '' `` not quite . napoléon 's new powers were derived from the constitution that was approved by a popular vote in the consulate . '' `` ha ! the constitution was practically dictated at gunpoint in a military coup , and the public only accepted the tyrant because they were tired of constant civil war . '' `` be that as it may , napoléon introduced a new constitution and a legal code that kept some of the most important achievements of the revolution in tact : freedom of religion abolition of hereditary privilege , and equality before the law for all men . '' `` all men , indeed . he deprived women of the rights that the revolution had given them and even reinstated slavery in the french colonies . haiti is still recovering from the consequences centuries later . what kind of equality is that ? '' `` the only kind that could be stably maintained at the time , and still far ahead of france 's neighbors . '' `` speaking of neighbors , what was with all the invasions ? '' `` great question , your honor . '' `` which invasions are we talking about ? it was the neighboring empires who had invaded france trying to restore the monarchy , and prevent the spread of liberty across europe , twice by the time napoléon took charge . having defended france as a soldier and a general in those wars , he knew that the best defense is a good offense . '' `` an offense against the entire continent ? peace was secured by 1802 , and other european powers recognized the new french regime . but bonaparte could n't rest unless he had control of the whole continent , and all he knew was fighting . he tried to enforce a european-wide blockade of britain , invaded any country that did n't comply , and launched more wars to hold onto his gains . and what was the result ? millions dead all over the continent , and the whole international order shattered . '' `` you forgot the other result : the spread of democratic and liberal ideals across europe . it was thanks to napoléon that the continent was reshaped from a chaotic patchwork of fragmented feudal and religious territories into efficient , modern , and secular nation states where the people held more power and rights than ever before . '' `` should we also thank him for the rise of nationalism and the massive increase in army sizes ? you can see how well that turned out a century later . '' `` so what would european history have been like if it were n't for napoléon ? '' `` unimaginably better/worse . '' napoléon seemingly unstoppable momentum would die in the russian winter snows , along with most of his army . but even after being deposed and exiled , he refused to give up , escaping from his prison and launching a bold attempt at restoring his empire before being defeated for the second and final time . bonaparte was a ruler full of contradictions , defending a popular revolution by imposing absolute dictatorship , and spreading liberal ideals through imperial wars , and though he never achieved his dream of conquering europe , he undoubtedly left his mark on it , for better or for worse .
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after the french revolution erupted in 1789 , europe was thrown into chaos . neighboring countries ' monarchs feared they would share the fate of louis xvi , and attacked the new republic , while at home , extremism and mistrust between factions lead to bloodshed .
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why did neighboring countries attack france following the 1789 revolution ?
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a national hero ? or public enemy number one ? historical figures are often controversial , but few were as deified or vilified in their lifetime as the seventh president of the united states . this is history vs. andrew jackson . `` order , order , hm , uh , what were we ... ah yes , mr. jackson ! you stand accused of degrading the office of the presidency , causing financial collapse and wanton cruelty against american indians . how do you plead ? '' `` now , your honor , i am not a big city lawyer , but i do know a few things . and i know that president jackson was a self-made frontiersman , a great general , a real man of the people . '' `` your honor , this 'man of the people ' was a gambler , a drunk , and a brawler . why , i 've heard it said that he would fight at the drop of the hat and then drop the hat himself . i ask you , was such a man fit for the most distinguished office in the nation ? can we forget the debacle of his inauguration ? who ever heard of inviting a drunken mob into the white house ? it took ages to get the upholstery clean . '' `` that drunken mob , sir , was the american people , and they deserve to celebrate their victory . '' `` order , order ! now , did this celebration have pie ? '' `` very well . mr. jackson , is it not the case that immediately upon assuming office you introduced the spoils system , replacing hundreds of perfectly good federal employees with incompetent party loyalists ? '' `` your honor , the president did no such thing . he tried to institute rotation in office to avoid any profiteering or funny business . it was the rest of the party who insisted on giving posts to their lackeys . '' `` but mr. jackson complied , did he not ? '' `` now , uh , see here . '' `` moving on . mr. jackson , did you not help to cause the financial panic of 1837 , and the ensuing economic depression with your obsessive war against the bank of the united states ? was not vetoing its reauthorization , as you did in 1832 , an act of irresponsible populace pandering that made no economic sense ? '' `` your honor , the gentleman has quite the imagination . that bank was just a way for rich yanks to get richer . and all that money panic was caused when british banks raised interest rates and cut lending . to blame it on the president is preposterous , i say . '' `` but if mr. jackson had not destroyed the national bank , it would have been able to lend to farmers and businesses when other credit dried up , would it not ? '' `` hm , this is all highly speculative . can we move on ? '' `` certainly , your honor . we now come to mr. jackson 's most terrible offense : forcing entire tribes out of their native lands via the indian removal act . '' `` i resent that accusation , sir . the u.s. of a. bought that land from the indians fair and square . '' `` do you call coercion and threats by a nation with a far more powerful army fair and square ? or signing a treaty for removing the cherokee with a small group that did n't include their actual leaders ? they did n't have time to properly supply themselves before the army came and forced them to march the trail of tears . '' `` now , hold on a minute . this was all van buren 's doing after president jackson left office . '' `` but mr. jackson laid the groundwork and made sure the treaty was ratified . all president van buren had to do afterwards was enforce it . '' `` look here , your honor . our government 's been purchasing indian land since the beginning , and my client was negotiating these deals even before he was president . president jackson truly believed it was best for the indians to get compensated for their land and move out west , where there was plenty of space for them to keep living the way they were accustomed , rather than stick around and keep butting heads with the white settlers . some of whom , i remind our court , wanted to exterminate them outright . it was a different time . '' `` and yet , even in this different time , there were many in congress and even the supreme court who saw how wrong the removal act was and loudly opposed it , were there not ? '' `` my client was under a great deal of pressure . i say , do you think it 's easy governing such a huge country and keeping the union together , when states are fixing to nullify federal laws ? president jackson barely got south carolina to back down over those import tariffs , and then georgia had to go discover gold and start grabbing up cherokee land . it was either get the indians to move or get in another fight with a state government . '' `` so , you admit that mr. jackson sacrified moral principles to achieve some political goals ? '' `` i do declare , show me one leader who has n't . '' as societies change and morals evolve , yesterday 's hero may become tomorrow 's villain , or vice versa . history may be past , but our understanding of it is always on trial .
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`` moving on . mr. jackson , did you not help to cause the financial panic of 1837 , and the ensuing economic depression with your obsessive war against the bank of the united states ? was not vetoing its reauthorization , as you did in 1832 , an act of irresponsible populace pandering that made no economic sense ? ''
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jackson tried to defund and destroy the bank of the united states because he felt ________ .
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sea turtles are miraculous . first , they 've been around since the late jurassic , roughly 150 million years ago . cohorts of the dinosaurs , sea turtles have survived through the challenges of eons , existing still today , where many others have ended their evolutionary run . second , throughout the centuries and up till today , every living adult sea turtle has overcome the odds , existing as a consequence of chance , skill , and capability . the gauntlet each sea turtle faces in the course of its lifetime goes thus : first , deposited as a clutch of leathery , ping-pong ball-sized eggs into a nesting pit dug by its mother high on the beach , of the 50 to 200 eggs laid , roughly 20 percent will never hatch . roughly a month and a half after having been laid , the surviving eggs hatch , and the young turtles , each small enough to fit in the palm of your hand , squirm to the surface , emerging from the sand en masse , and making their desperate dash for the sea . along the way , debris , pitfalls , crabs , gulls , raccoons , and other threats will claim roughly 50 percent of those who rose from the sand . for those that actually reach the surf , they trade one set of threats for another , as they first face the repelling force of the waves , and then find a whole new host of predators awaiting them : various fish , dolphins , sharks , and sea birds , as the young turtles come to the surface for air . for their first few days of life , should they count themselves amongst the living , the vulnerable turtles swim frantically forward . ultimately , they will often look to settle in a patch of flotsam , preferably a patch of floating seaweed . now for the next several months , they will seek to avoid those that would eat them , find that which they might eat themselves , and not fall to the pressures of challenging weather or unfortunate currents . in this phase , roughly 50 percent of those who reach the surf will perish . ultimately , with the passage of years , the survivors will increase in size , from that of a dinner plate at year one to that of a dinner table , in the case of one species at least , the leatherback , a decade or so later . with size comes some measure of protection . the only truly worrisome predators now are some of the larger shark species -- bulls , tigers , and whites -- and the occasional killer whale . at approximately two decades of age , the survivors will be old enough themselves to breed , and continue the cycle which their very existence heralds . of those that began as eggs on a distant beach , now less than 10 percent remain , at least , those were the odds prior to significant human interference . over the past century , and in particular in the last several decades , human endeavors , from beach development to plastic refuse to poaching , long lines , nets , and even noxious chemicals , including oil , have upped the ante for sea turtles , causing their survival rate to drop to around one percent or less , from each nesting cycle . it is this added human pressure which has pushed each of the eight sea turtle species into either a threatened or endangered state . for while they have evolved to overcome a host of obstacles , the most recent has arisen so quickly and at such scale that the species find themselves overwhelmed . so let 's quickly recap this cycle of odds . using a hypothetical nesting season , for females may nest multiple times in a single year , of 1,000 eggs , for sake of ease . 1000 eggs laid . 800 hatch . 400 make it to the water . 200 progress toward adulthood . 20 survive to breeding age -- that is , without human interference . two survive to breeding age with human interference . so a breeding adult sea turtle is the very embodiment of a long shot . it is the exception , not the rule . a jackpot . it is , in a very real sense , a miracle .
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for those that actually reach the surf , they trade one set of threats for another , as they first face the repelling force of the waves , and then find a whole new host of predators awaiting them : various fish , dolphins , sharks , and sea birds , as the young turtles come to the surface for air . for their first few days of life , should they count themselves amongst the living , the vulnerable turtles swim frantically forward . ultimately , they will often look to settle in a patch of flotsam , preferably a patch of floating seaweed .
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during their first few days of life , sea turtle hatchlings swim frantically out into the ocean , driven by instinct to seek shelter in :
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translator : andrea mcdonough reviewer : bedirhan cinar my name is tom chi . i spent two years of my life building the user experience team for the google x division of google , and it 's a place i affectionately call the department of science fiction because of the futuristic nature of the types of projects we took on : self-driving cars , google glass , and other things that you 'll see soon enough . so , for those who have n't heard of this project , this is what google glass looks like . it allows you to overlay digital things into your eye sight while still maintaining being part of the world . so , if i , you know , were to pull out my cell phone and look into it , i 'm basically out of this world now , like , i 'm in my own little cell phone-tablet world , what have you . but , google glass has the vision of allowing us to continue to be in the world but also have access to the digital things that we need and love . now , i am going to ask you a real simple question about google glass : how would you prototype this experience ? how long do you think it would take you to make the first working version of the headset display ? okay , a little bit on the long side . the answer is one day . and here 's what it looked like . so , basically the magic piece is the coat hanger . the coat hanger , i bent it in a specific shape and the top loop goes around your neck and then the bottom loop rests against your chest and it allows me to carry a piece of plexiglass on with a little sheet protector . so these are the things you put your book reports in so they do n't get wet , i literally got at the drug store . you know , have it out at the end of the plexiglass and then it gets projected onto with the pico projector that 's connected to a netbook . and using this set-up , within one day we 're already able to start having the experience of what it looks like to have digital things overlaid on your physical world , be able to move around with it , and also use the netbook to try out tons and tons of different ideas around software . now , after you start getting something like that working , you know , a really important problem comes up , like you 're wearing this thing on your head , it 's like a pair of glasses , so you do n't have a mouse or a keyboard or a touchscreen , all the ways you are used to interacting with a machine . so , we thought for a second , well , maybe we could do something like , you know , what was shown in < i > minority report < /i > . so , for folks who have n't seen that , basically tom cruise is manipulating software with his hands in front of his face and photos are flying over here and his email is over here and so on and so forth . so i 'll ask the the same question again , how long do you think it would take to have the real experience of doing something like that ? two years , ok. somebody said one day . 45 minutes . so here 's how it looks . so you wear the thing that we saw that first time because you need some way to go project things , but what happens is we got two hairbands , which i think was the hardest part we had to do , ask people for their hairbands . but you put one hand in each hairband and attach that hairband , we tied a fishing line . and the fishing line goes over the top of a whiteboard and then goes down to this little assembly that 's taped to the floor . and what this means is every time i move my hand in any direction , it adds tension to the line and it does the following with the assembly on the floor . so , the other end of the fishing wire is attached to a chopstick and it 's not because i 'm asian , there 's just a cafeteria nearby , i do n't just carry chopsticks on me . but , i tied it to the end of a chopstick , i clipped it into a binder clip , and then put it over a pen , and basically what happens then is when you move your arm and it produces tension on the wire , the chopstick comes down like a lever and clicks a presentation clicker , one hand moves the presentation forward , the other hand moves the presentation backwards . so this was built in 45 minutes and that meant shortly afterwards , we were having experiences like looking at an image gallery and saying , `` next image , next image , previous image , '' or looking at our emails and saying , `` let me click into this email , let me click reply now . '' and this was exactly the experience of what it was like to go control software with your hands . and ultimately , what it taught us is we probably should n't have this in the product . we learned a lot of things about the social awkwardness of it and some of the ergonomic aspects of it that you could n't have figured out ahead of just thinking about it . and , ergo the second prototyping rule , which is `` doing is the best kind of thinking . '' they teach you to think a lot in school , but i think it is a little bit overrated . now last example , you know , actually google is not the first team that 's tried to go make something like this and if you search for headset display , you get tons of images of teams that have built various systems like this , but i can tell you at a glance that none of these pieces of hardware are comfortable to wear for more than 15 minutes except for maybe the helmet over there , but then you got to wear a helmet . so , you know , how would you go figure out a way to go wear something like this comfortably ? the answer is really basic materials : modeling wire , paper , clay , and using something like this is able to make something look like a pair of glasses really quickly . i cut out pieces of clay that weighed exactly the same amount as the electronic components that we were talking about putting on the device , wrapped it in paper so you did n't get clay on your face , and then taped it to the modeling wire in various places to go experiment with how a pair of glasses could fit on you . and , we discovered something really important then . like , if you look at this drawing on the bottom , it turns out that the weight of a pair of glasses is actually mostly perceived through how much weight is on your nose . and , it also turns out that your ears can carry a lot more weight than your nose , and that is a totally different experiment , you can ask me about that . but , because of that fact , if you put weight behind your ears , it allows your ear to go act like the fulcrum of a lever and it then takes weight off of your nose on the front . and , actually , you can try this now , anybody with glasses , if you push very gently on the back of your glasses , you 'll find , actually your glasses feel tremendously lighter . now , this meant that we not only discovered something interesting about how to go , you know , that 's useful for developing a device like this , we actually discovered something pretty fundamental that never been discovered about glasses , period . so , if you have really heavy glasses , you could do this and you would be more comfortable . now , the last point i want to make is about two types of learning because through the process of rapid prototyping , you are able to learn very quickly . it 's a very specific type of learning . the type of learning that you usually learn in school i call book learning . it comes from what humanity already knows and it 's a necessary foundation for you guys to go and explore the world . but there is a totally different type of learning , which i call expansive learning , and this is the learning you do on behalf of humanity . right ? you are creating something new , you are expanding into the possibilities , and you 're building the sphere of human knowledge in that process . and , we think about these things and as soon as you hear like , ok , the infinite realm of possibilities beyond the sphere of human knowledge , you might be thinking there 's the scientists at the large hadron collider who have these amazing instruments , like that 's their job , right ? but the truth is that this action is available to all of us , you know , it 's not just for the scientists , it 's also for the poet or the songwriter that expresses an emotion for the first time in a unique way . it 's also for the person that has an amazing business idea that they 're certain could help millions of lives . and , it 's the realm of using paper , clay , and tape in order to go find a new insight in an ancient technology . so now that you know a lot about rapid prototyping , i 'm excited to see what you do with it . thank you .
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we learned a lot of things about the social awkwardness of it and some of the ergonomic aspects of it that you could n't have figured out ahead of just thinking about it . and , ergo the second prototyping rule , which is `` doing is the best kind of thinking . '' they teach you to think a lot in school , but i think it is a little bit overrated .
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what is chi 's second prototyping rule ?
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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 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 .
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who did cleopatra ally with and against immediately after caesar ’ s death ?
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it 's estimated that for every 10,000 bills in the u.s. , one of those bills is fake . that may not sound like much , but it adds up to millions of dollars in cold hard cash . counterfeit money has the potential to cause all sorts of problems , from leaving you short $ 20 to destabilizing national economies . but do n't worry . you can help catch the counterfeits . all you need are some simple tools and a bit of chemistry . first up , the anti-counterfeit detection pen . the pen looks like a highlighter and contains a solution of potassium iodide and elemental iodine . it reveals of the presence of starch , which is commonly used to strengthen regular printer paper , but wo n't be found in real money . that 's because authentic bills are made of cotton and linen and are threaded with tiny red and blue fibers . that material is made by a single , highly-guarded company called crane and company , which has been printing currency since paul revere asked them to help finance the revolutionary war . the starch in many counterfeit bills , on the other hand , is made of two molecules : amylopectin and amylose . it 's amylose that gives the fake away . its long chain of sugar molecules connected by oxygen atoms forms a helical structure , like dna . iodide likes to squeeze inside this coil , forming a new compound that leaves a dark mark on the paper . however , in the absence of starch , there is no chemical reaction and the mark will look light yellow . so if the fake is n't printed on starchy paper , iodine solutions ca n't help you . that 's one of the reasons u.s. bills printed since 1996 have been chemically enhanced to include another counterfeit countermeasure : a strip that fluoresces under uv light . that 's the same kind of light used at black light parties and airport security lines . the polyester strip printed with invisble ink is just one millimeter wide and is found in different positions depending on a bill 's value . if you hold your dollar up to natural light , you can see the amount and the word usa printed on the band . but under uv light , these strips really shine . they contain molecules that can be excited by absorbing certain amounts of energy , specifically , that given off by common uv light sources . as these excited molecules return to their original states , they lose a bit of energy as heat and then radiate the rest as light . energy is inversely related to wavelength , which means that the longer wavelengths have lower energy . so the lower energy light given off by the strip means longer wavelengths that fall in the visible range , and suddenly we can see that which had been invisible . and if a glowing strip does n't show up on a recent bill , you have a fake on your hands . for times when you 're not dealing with counterfeit masterminds , looking for simple visual cues will do . make sure the portrait looks lifelike and not flat , the seal has perfectly even sawtooth points , the inked border is unbroken , and the serial number has precisely equal spacing between each number . so the next time you come across some dubious dough , have a closer look , pull out your iodine solution , or take it to a rave and you just might catch a counterfeit .
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that material is made by a single , highly-guarded company called crane and company , which has been printing currency since paul revere asked them to help finance the revolutionary war . the starch in many counterfeit bills , on the other hand , is made of two molecules : amylopectin and amylose . it 's amylose that gives the fake away .
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why doesn ’ t amylopectin react with i3- ?
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translator : andrea mcdonough reviewer : jessica ruby the world we live in is made of things , billions and billions of different things , like pickles and pianos and dump trucks and octopi . and even though these things seem totally different , they 're all made of the same stuff , just combined in different ways . to give you an idea of how this combining works , let 's take something apart . let 's start with this bowl of macaroni salad . if you were to reverse a recipe for macaroni salad , you 'll see it 's made by mixing together a bunch of ingredients , like macaroni , mayo , vinegar , vegetables , and mustard . this type of combining is called a mixture . when you make a mixture , you 're combining two or more things together without actually changing the chemical identity of those things . like mud , for example . the soil and water in mud have n't actually changed . they 're still soil and water , you 've just created a mixture of soil and water -- mud . it turns out that macaroni salad is actually a mixture of mixtures because many of the ingredients , like mayo and mustard , are already mixtures themselves , which is nice for us because if we look closely , we 'll the see the three main types of mixtures that exist . the size of the particles in a mixture determines the type of mixture . on one end of the scale is a suspension , like our muddy water example . you get this if you take big chunks of something and mix it with something else so those chunks are just floating around . take runny mustard for example . you 'll see a bunch of little particles like mustard seeds , pepper , allspice , and minced shallots all floating around in a liquid , in this case vinegar with water . this is called a suspension because you 've got particles of one thing suspended in another . now , on the other end of the spectrum is a solution . the particles in this mixture are so small , they are the actual molecules . a solution is sort of like a suspension of molecules where one type of molecule is blended or dissolved with another . vinegar is an example of a solution where the molecules of acetic acid are blended with molecules of water . the chemical properties of the molecules have n't changed , they 're just evenly mixed together now . saltwater and carbonated soda are both examples of solutions where other molecules are dissolved in water . the last type of mixture is called a colloid , which is somewhere between a suspension and a solution . it 's when you take two materials that do n't dissolve and you make the particles so small that they ca n't separate . mayo is what happens when you take oil and water , which do n't mix , and you bind them together , usually with the help of another substance called an emulsifier . in the case of mayo , it 's lecithin , found in eggs . and now you are left with really small globs of oil hanging out with really small droplets of water . whipped cream , hairspray , styrofoam , and jello are all other examples of colloids . so , let 's get back to macaroni salad . you 've call colloids like mayo , suspensions like mustard , and solutions like vinegar , but you 've also got celery , shallots , and all other vegetable chunks that are also part of the salad . these are n't mixtures , really , but we can break them up , just like a tv can be broken up into smaller and smaller complex component parts . in the case of vegetables , if you keep breaking things up , they 'll eventually end with thousands of complex organic molecules , things like atp synthase and rna transcriptase and water . so now , once we 've unblended all the solutions , unmixed all the colloids , separated all the suspensions and taken apart all of our vegetables , we 've reached the end of what we can unmix physically . what we 're left with is a whole bunch of molecules , and these molecules remain chemically the same whether they are by themselves or thrown together in a salad . if you want to separate these guys even further , we need to unmix things chemically , which means we need to start breaking some bonds .
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this is called a suspension because you 've got particles of one thing suspended in another . now , on the other end of the spectrum is a solution . the particles in this mixture are so small , they are the actual molecules .
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what is a characteristic of a solution ?
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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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after losing some balloons and having to use a large ladder , how did neil and pete get the balloon full of helium to sit on the table ?
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why is it so difficult to cure cancer ? we 've harnessed electricity , sequenced the human genome , and eradicated small pox . but after billions of dollars in research , we have n't found a solution for a disease that affects more than 14 million people and their families at any given time . cancer arises as normal cells accumulate mutations . most of the time , cells can detect mutations or dna damage and either fix them or self destruct . however , some mutations allow cancerous cells to grow unchecked and invade nearby tissues , or even metastasize to distant organs . cancers become almost incurable once they metastasize . and cancer is incredibly complex . it 's not just one disease . there are more than 100 different types and we do n't have a magic bullet that can cure all of them . for most cancers , treatments usually include a combination of surgery to remove tumors and radiation and chemotherapy to kill any cancerous cells left behind . hormone therapies , immunotherapy , and targeted treatments tailored for a specific type of cancer are sometimes used , too . in many cases , these treatments are effective and the patient becomes cancer-free . but they 're very far from 100 % effective 100 % of the time . so what would we have to do to find cures for all the different forms of cancer ? we 're beginning to understand a few of the problems scientists would have to solve . first of all , we need new , better ways of studying cancer . most cancer treatments are developed using cell lines grown in labs from cultures of human tumors . these cultured cells have given us critical insights about cancer genetics and biology , but they lack much of the complexity of a tumor in an actual living organism . it 's frequently the case that new drugs , which work on these lab-grown cells , will fail in clinical trials with real patients . one of the complexities of aggressive tumors is that they can have multiple populations of slightly different cancerous cells . over time , distinct genetic mutations accumulate in cells in different parts of the tumor , giving rise to unique subclones . for example , aggressive brain tumors called glioblastomas can have as many as six different subclones in a single patient . this is called clonal heterogeneity , and it makes treatment difficult because a drug that works on one subclone may have no effect on another . here 's another challenge . a tumor is a dynamic interconnected ecosystem where cancer cells constantly communicate with each other and with healthy cells nearby . they can induce normal cells to form blood vessels that feed the tumor and remove waste products . they can also interact with the immune system to actually suppress its function , keeping it from recognizing or destroying the cancer . if we could learn how to shut down these lines of communication , we 'd have a better shot at vanquishing a tumor permanently . additionally , mounting evidence suggests we 'll need to figure out how to eradicate cancer stem cells . these are rare but seem to have special properties that make them resistant to chemotherapy and radiation . in theory , even if the rest of the tumor shrinks beyond detection during treatment , a single residual cancer stem cell could seed the growth of a new tumor . figuring out how to target these stubborn cells might help prevent cancers from coming back . even if we solved those problems , we might face new ones . cancer cells are masters of adaptation , adjusting their molecular and cellular characteristics to survive under stress . when they 're bombarded by radiation or chemotherapy , some cancer cells can effectively switch on protective shields against whatever 's attacking them by changing their gene expression . malignant cancers are complex systems that constantly evolve and adapt . to defeat them , we need to find experimental systems that match their complexity , and monitoring and treatment options that can adjust as the cancer changes . but the good news is we 're making progress . even with all we do n't know , the average mortality rate for most kinds of cancer has dropped significantly since the 1970s and is still falling . we 're learning more every day , and each new piece of information gives us one more tool to add to our arsenal .
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we 're beginning to understand a few of the problems scientists would have to solve . first of all , we need new , better ways of studying cancer . most cancer treatments are developed using cell lines grown in labs from cultures of human tumors . these cultured cells have given us critical insights about cancer genetics and biology , but they lack much of the complexity of a tumor in an actual living organism .
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which is the least faithful model of human cancer ?
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living with her family high above the ground in the northern tropical forests of colombia , you will find shakira , a cotton-top tamarin with a penchant for conversation . say , `` hola ! '' though you may not realize it , this one pound monkey communicates in a highly sophisticated language of 38 distinct calls based on variations of chirps and whistles . the response she just gave is known as a `` b chirp '' , a call often directed at humans . to appreciate the complexities of shakira 's language , let 's learn a few chirps and whistles , then examine how their combinations form grammatically structured sequences . the chirp shakira used to greet us comes from a class of calls known as single frequency modulated syllables . this class is made up of short duration calls , or chirps , and long duration calls , like screams and squeals . researchers have determined that there are eight different types of chirps categorized by stem upsweep , duration , peak frequency , and frequency change . in addition , each chirp has its own unique meaning . for example , shakira 's `` c chirp '' is used when she is approaching food , where as her `` d chirp '' is only used when she has the food in hand . single whistles also exhibit a unique intention with each call and just as there are eight different chirps , there are five different whistles . based on frequency modulation , single whistles are subdivided into four categories : squeaks , initially modulated whistles , terminally modulated whistles , and flat whistles . the language 's quality of unique intention is wonderfully exemplified by the category of initially modulated whistles . these whistles change based on the proximity of shakira to other members of her family . if shakira is greater than .6 meters from her family , she 'll sound a large initally modulated whistle . but if she 's less than .6 meters from her family , she 'll sound a small initially modulated whistle . now that we 've learned a few chirps and whistles , shakira wants to show off by taking you through a quick day in her life with these calls . while heading towards a feeding tree for her first meal of the day , she says , ( monkey noise ) , a call most often used in relaxed investigations . however , suddenly she spots the shadow of a hawk . `` e chirp '' for alarm . this call alerts her family to the presence of this predator , and shakira jumps to the safety of an inner branch . the coast seems clear , so shakira makes her way towards her dad . wait , wait . who is that ? ah , it 's her younger brother , carlos . cotton-top tamarins often squeal during play wrestling . uh-oh . he 's playing a little too roughly , and shakira screams , alerting her parents to help her . her dad makes his way towards the ball of rolling fur and her brother stops . shakira shakes herself and scratches herself to get the hair on her head back in place . then shakira spots another group of unfamiliar tamarins and hears their normal long call . she turns to her family . ( monkey noise ) did you catch that ? first there was a chirp , then a whistle . this is what 's known as a combination vocalization , a phrase that contains both a chirp and a whistle . these are two calls strung together to convey a message . the combination of these two elements alerts her family to the presence of another group , the `` f chirp '' , and the distance they are away , the normal long call whistle . in other words , shakira just said a sentence . her simple demonstration is just the tip of the iceberg . she 's got trills , chatters , multiple whistle calls , more combination vocalizations , even twitters . yet sadly enough , we may not get to hear everything she has to say . mixed in with chirping sonatas from high above is the constant thud of a machete chopping trees . shakira 's habitat in colombia is being cut down , piece by piece , and if we do n't work to protect the critically endangered cotton-top tamarin , it will become extinct in our lifetime . if the chirp from one tamarin to the next has proven to be more than just idle chit chat , imagine what else we have left to discover . imagine what else shakira can tell us .
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ah , it 's her younger brother , carlos . cotton-top tamarins often squeal during play wrestling . uh-oh .
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cotton-top tamarins use vocalizations in a variety of contexts . can you describe a situation in which a cotton-top tamarin uses a vocalization to communicate information to another tamarin ?
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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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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 .
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in what other ways are elephants similar to humans ?
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take a series of still , sequential images . let 's look at them one by one . faster . now , let 's remove the gaps , go faster still . wait for it ... bam ! motion ! why is that ? intellectually , we know we 're just looking at a series of still images , but when we see them change fast enough , they produce the optical illusion of appearing as a single , persistent image that 's gradually changing form and position . this effect is the basis for all motion picture technology , from our led screens of today to their 20th-century cathode ray forebearers , from cinematic film projection to the novelty toy , even , it 's been suggested , all the way back to the stone age when humans began painting on cave walls . this phenomenon of perceiving apparent motion in successive images is due to a characteristic of human perception historically referred to as `` persistence of vision . '' the term is attributed to the english-swiss physicist peter mark roget , who , in the early 19th century , used it to describe a particular defect of the eye that resulted in a moving object appearing to be still when it reached a certain speed . not long after , the term was applied to describe the opposite , the apparent motion of still images , by belgian physicist joseph plateau , inventor of the phenakistoscope . he defined persistence of vision as the result of successive afterimages , which were retained and then combined in the retina , making us believe that what we were seeing is a single object in motion . this explanation was widely accepted in the decades to follow and up through the turn of the 20th century , when some began to question what was physiologically going on . in 1912 , german psychologist max wertheimer outlined the basic primary stages of apparent motion using simple optical illusions . these experiments led him to conclude the phenomenon was due to processes which lie behind the retina . in 1915 , hugo münsterberg , a german-american pioneer in applied psychology , also suggested that the apparent motion of successive images is not due to their being retained in the eye , but is superadded by the action of the mind . in the century to follow , experiments by physiologists have pretty much confirmed their conclusions . as it relates to the illusion of motion pictures , persistence of vision has less to do with vision itself than how it 's interpreted in the brain . research has shown that different aspects of what the eye sees , like form , color , depth , and motion , are transmitted to different areas of the visual cortex via different pathways from the retina . it 's the continuous interaction of various computations in the visual cortex that stitch those different aspects together and culminate in the perception . our brains are constantly working , synchronizing what we see , hear , smell , and touch into meaningful experience in the moment-to-moment flow of the present . so , in order to create the illusion of motion in successive images , we need to get the timing of our intervals close to the speed at which our brains process the present . so , how fast is the present happening according to our brains ? well , we can get an idea by measuring how fast the images need to be changing for the illusion to work . let 's see if we can figure it out by repeating our experiment . here 's the sequence presented at a rate of one frame per two seconds with one second of black in between . at this rate of change , with the blank space separating the images , there 's no real motion perceptible . as we lessen the duration of blank space , a slight change in position becomes more apparent , and you start to get an inkling of a sense of motion between the disparate frames . one frame per second . two frames per second . four frames per second . now we 're starting to get a feeling of motion , but it 's really not very smooth . we 're still aware of the fact that we 're looking at separate images . let 's speed up . eight frames per second . 12 frames per second . it looks like we 're about there . at 24 frames per second , the motion looks even smoother . this is standard full speed . so , the point at which we lose awareness of the intervals and begin to see apparent motion seems to kick in at around eight to 12 frames per second . this is in the neighborhood of what science has determined to be the general threshold of our awareness of seeing separate images . generally speaking , we being to lose that awareness at intervals of around 100 milliseconds per image , which is equal to a frame rate of around ten frames per second . as the frame rate increases , we lose awareness of the intervals completely and are all the more convinced of the reality of the illusion .
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wait for it ... bam ! motion ! why is that ?
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do you think we take motion pictures for granted these days ? why ?
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what does it mean to be one in a million ? not in the greeting card sense , in the scientific sense , where one part per million is a unit of measurement . parts per million counts the number of units of one substance per one million units of another . it can measure concentrations when a small amount makes a big difference . for example , a concentration of just 35 ppm of carbon monoxide in the air is poisonous to us . we encounter measurements like this pretty often , but because it 's hard to conceptualize really large numbers , it 's difficult to wrap our brain around what one part per million really means . so here are nine helpful ways to visualize it . if you had 11,363 pianos-worth of piano keys , one of those keys would be about one part per million . so would a single granule of sugar among 273 sugar cubes , one second in eleven and a half days , or four dots in the painting , `` a sunday afternoon on the island of la grande jatte . '' your bath tub 's capacity is about 60 gallons , so seven drops of ink would be one part per million . the english version of the harry potter series has 1,084,170 words , which makes `` hippogriff '' on page 221 of `` the prisoner of azkaban '' a little less than one part per million . a million kernels of corn is about 1,250 ears , so one kernel in that truckload would be one part per million . there are 10 million bricks in the empire state building , so one part per million would be a pile of just ten . and finally , 100 people worked together to animate this video . collectively , they have about 10 million hairs on their heads . pluck ten of those hairs , and you have one in a million .
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not in the greeting card sense , in the scientific sense , where one part per million is a unit of measurement . parts per million counts the number of units of one substance per one million units of another . it can measure concentrations when a small amount makes a big difference .
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now , how many hands would represent 5 parts per million ?
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hmmm , that 's not what we want , is it ? today 's digital cameras do a lot for us , but there 's no replacement for the human eye . it 's important to learn how cameras work with light to create an image , that way we 'll know what 's going on when it 's time to capture a moment . there are three variables that determine if you 're getting the right amount of light for the correct exposure . with a manual camera , we 're able to change any of the variable ourselves . different settings can result in really different pictures . let 's look at the process together . first , see this here ? this is the aperture . it 's the hole that light passes through . if we make the aperture big , we 'll have more light , true , but the sharpness of your photo will decrease very quickly from your focus point , backward and forward . this is what we call shallow depth of field . if we have a very small aperture , we 'll have less light but a deeper depth of field . for portraits , it can be nice to have a sharp figure separate from a somewhat blurry background so i would suggest a large aperture . aperture is measured in f-stops . this can get a little confusing because lower numbers mean bigger apertures and higher numbers mean smaller apertures . next , there 's shutter speed to think about . the shutter acts like a curtain that covers the sensor , and it only opens when you release the shutter button . if we want less light , we open the shutter for a shorter time . if we want more light , we open it for a longer time , but we run the risk of getting a motion-blurred picture . the speed is measured in seconds and fractions of seconds . for shooting sports or anything with a lot of movement , we 'll need faster speeds . for taking awesome night landscapes , longer exposures will be better , but we 'll need a tripod to steady the shot and prevent motion blur . another cool thing we can do with light exposures is light painting , drawing in the dark with a torch or the light of a cell phone . lastly , iso sensitivity controls how sensitive the sensor is to light . if we use low sensitivity , we 'll need more light to register a photo . with a higher sensitivity , we 'll be able to get a picture with less available light . 100 iso is a low sensitivity , while 6400 iso is a high one . if we increase sensitivity , we 'll be able to use faster speeds and smaller apertures , but we 'll get noisier images . good thing we have something to tell us if we 're getting the correct amount of light to get a good exposure , the light meter . sound good to you ? now it 's time to get out there and practice taking pictures under different conditions , so you know what to do any time you want to take the best picture .
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it 's important to learn how cameras work with light to create an image , that way we 'll know what 's going on when it 's time to capture a moment . there are three variables that determine if you 're getting the right amount of light for the correct exposure . with a manual camera , we 're able to change any of the variable ourselves . different settings can result in really different pictures .
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how many variables are we able to change in a manual camera for getting the right exposure ?
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the human eye is an amazing mechanism , able to detect anywhere from a few photons to direct sunlight , or switch focus from the screen in front of you to the distant horizon in a third of a second . in fact , the structures required for such incredible flexibility were once considered so complex that charles darwin himself acknowledged that the idea of there having evolved seemed absurd in the highest possible degree . and yet , that is exactly what happened , starting more than 500 million years ago . the story of the human eye begins with a simple light spot , such as the one found in single-celled organisms , like euglena . this is a cluster of light-sensitive proteins linked to the organism 's flagellum , activating when it finds light and , therefore , food . a more complex version of this light spot can be found in the flat worm , planaria . being cupped , rather than flat , enables it to better sense the direction of the incoming light . among its other uses , this ability allows an organism to seek out shade and hide from predators . over the millenia , as such light cups grew deeper in some organisms , the opening at the front grew smaller . the result was a pinhole effect , which increased resolution dramatically , reducing distortion by only allowing a thin beam of light into the eye . the nautilus , an ancestor of the octopus , uses this pinhole eye for improved resolution and directional sensing . although the pinhole eye allows for simple images , the key step towards the eye as we know it is a lens . this is thought to have evolved through transparent cells covering the opening to prevent infection , allowing the inside of the eye to fill with fluid that optimizes light sensitivity and processing . crystalline proteins forming at the surface created a structure that proved useful in focusing light at a single point on the retina . it is this lens that is the key to the eye 's adaptability , changing its curvature to adapt to near and far vision . this structure of the pinhole camera with a lens served as the basis for what would eventually evolve into the human eye . further refinements would include a colored ring , called the iris , that controls the amount of light entering the eye , a tough white outer layer , known as the sclera , to maintain its structure , and tear glands that secrete a protective film . but equally important was the accompanying evolution of the brain , with its expansion of the visual cortex to process the sharper and more colorful images it was receiving . we now know that far from being an ideal masterpiece of design , our eye bares traces of its step by step evolution . for example , the human retina is inverted , with light-detecting cells facing away from the eye opening . this results in a blind spot , where the optic nerve must pierce the retina to reach the photosensitive layer in the back . the similar looking eyes of cephalopods , which evolved independently , have a front-facing retina , allowing them to see without a blind spot . other creatures ' eyes display different adaptations . anableps , the so called four-eyed fish , have eyes divided in two sections for looking above and under water , perfect for spotting both predators and prey . cats , classically nighttime hunters , have evolved with a reflective layer maximizing the amount of light the eye can detect , granting them excellent night vision , as well as their signature glow . these are just a few examples of the huge diversity of eyes in the animal kingdom . so if you could design an eye , would you do it any differently ? this question is n't as strange as it might sound . today , doctors and scientists are looking at different eye structures to help design biomechanical implants for the vision impaired . and in the not so distant future , the machines built with the precision and flexibilty of the human eye may even enable it to surpass its own evolution .
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the story of the human eye begins with a simple light spot , such as the one found in single-celled organisms , like euglena . this is a cluster of light-sensitive proteins linked to the organism 's flagellum , activating when it finds light and , therefore , food . a more complex version of this light spot can be found in the flat worm , planaria .
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which organism demonstrates the use of simple light spots ?
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in this short video , we 're going to show you how we use two different animation techniques , both rotoscoping and traditional hand-drawn animation in the ted-ed lesson , `` miss gayle 's 5 steps to slam poetry : a lesson of transformation . '' a poetry slam is a competition in which poets are judged on their poems , often for qualities of emotional power and lyrical resonance . our lesson was created by gayle danley , a veteran slam poet who spent decades teaching children to express themselves through spoken words , a lesson , which offers a guide to creating poetry with immediacy and power , also serves as a great example of exactly that . it 's a story told in the form of a poem that packs a real emotional punch . she introduces tyler , who 's sitting in an 11th grade writing class , struggling with the assignment of having to write a poem based on a personal experience . the story is told from two perspectives , one external and one internal . miss gayle 's narration sets the stage of the outside world , and spoken word artist pages d. matan performs tyler 's inner voice . to set these two realms of inner- and outer-experience apart , a different animation technique was used to illustrate each . the real world was animated by rotoscoping , with a frame-by-frame tracing of live-action footage in black and white line art . the animation depicting the inner-stream of consciousness world of tyler 's memories was traditionally drawn on paper , featured watercolored backgrounds and a more expressionistic design . once deciding on this general approach , the project went right into pre-production . in animation , pre-production is the planning stage . it 's all the decisions that need to be made before going and actually making the thing in its final form . this can include developing the look or design of the piece , experimenting with colors and camera angles , revising the script , and so on . all these decisions are important because they determine how much work and time the production will take . extra time spent here figuring things out can often save a lot of time down the road . for our project , a storyboard was first created , in which the framing , composition , and imagery for each shot was determined . then an animatic was made , which is basically a movie of the storyboard . this helped us figure out the timing of each shot . it also helped us get an idea of how well everything would flow together visually between our rotoscoped and traditionally animated scenes once they were assembled . for the rotoscoped shots , we first had to create the live action footage to be traced . working with what we had in our humble office , we created a classroom of desks using only one small table . we shot this multiple times from each angle the storyboard called for , each time with a different volunteer from among our co-workers . our source footage elements then needed to be composited , or assembled and arranged together , before we could rotoscope them . a composite is a special effects term for a shot that combines two or more elements in it that were created separately . to do this , we used after effects , a digital compositing and motion graphics program . the first step was to isolate the part of the frame we needed by masking off the unnecessary negative space , or parts of the frame we did n't need . the individual shots were then each layered into one composite shot , resized and arranged appropriately to create the illusion of them all being there in perspective at the same time . every third frame was then exported as an image sequence , ready to be rotoscoped . the tracing was done digitally , drawn directly on a cintiq monitor . the rest of the animation was done by hand on paper . unlike rotoscoping , here the timing and motion of the animation was all planned out by the animator ahead of time . an appropriate number of drawings were then done to accomplish the movement . each animation drawing is then scanned , registered , and sequenced together in the computer . that animation sequence is then composited with the layered background art . camera moves are then plotted out and executed . one way that poetry uses language to communicate emotions and ideas is through the use of metaphor . `` mama 's lies are footsteps too many to count making excuses on black snow . '' animation 's a medium that 's also uniquely well-suited to communicating emotions and ideas through visual metaphor . applying the dual techniques of rotoscoped and traditional animation , each with their own inherent looks , allowed us to visually represent the dual nature of the creative process described in the lesson . there 's the internal aspect of experience and memory , which is mined for inspiration , and there 's the external aspect of revealing it to the world through a structured presentation . we combined both techniques for the last shots of tyler delivering his poem to the world , allowing us to convey in a direct , visual way the power of that moment of communication when internal becomes external , which , in both poetry and animation , is where the magic happens .
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in this short video , we 're going to show you how we use two different animation techniques , both rotoscoping and traditional hand-drawn animation in the ted-ed lesson , `` miss gayle 's 5 steps to slam poetry : a lesson of transformation . '' a poetry slam is a competition in which poets are judged on their poems , often for qualities of emotional power and lyrical resonance .
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how is traditional animation different from rotoscoping ?
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you probably do n't need to be told how important your brain is . after all , every single thing you experience , your thoughts and your actions , your perceptions and your memories are processed here in your body 's control center . but if this already seems like a lot for a single organ to handle , it 's actually only a small part of what the brain does . most of its activities are ones you 'd never be aware of , unless they suddenly stopped . the brain is made up of billions of neurons , and trillions of connections . neurons can be activated by specific stimuli or thoughts , but they are also often spontaneously active . some fire cyclically in a set pattern . others fire rapidly in short bursts before switching off , or remain quiet for long periods until thousands of inputs from other neurons line up in just the right way . on a large scale , this results in elaborate rhythms of internally generated brain activity , humming quietly in the background whether we 're awake , asleep , or trying not to think about anything at all . and these spontaneously occurring brain functions form the foundation upon which all other brain functions rely . the most crucial of these automatically occurring activities are the ones that keep us alive . for example , while you 've been paying attention to this video spontaneous activity in your brain has been maintaining your breathing at 12 to 16 breaths a minute , making sure that you do n't suffocate . without any conscious effort , signals from parts of your brainstem are sent through the spinal cord to the muscles that inflate your lungs , making them expand and contract , whether or not you 're paying attention . the neuronal circuits underlying such rhythmic spontaneous activity are called central pattern generators , and control many simple repetitive behaviors , like breathing , walking , and swallowing . ongoing neural activity also underlies our sensory perception . it may seem that the neurons in your retina that translate light into neural signals would remain quiet in the dark , but in fact , the retinal ganglion cells that communicate with the brain are always active . and the signals they send are increases and decreases in the rate of activity , rather than separate bursts . so at every level , our nervous system is teeming with spontaneous activity that helps it interpret and respond to any signals it might receive . and our brain 's autopilot is n't just limited to our basic biological functions . have you ever been on the way home , started thinking about what 's for dinner , and then realized you do n't remember walking for the past five minutes ? while we do n't understand all the details , we do know that the ongoing activity in multiple parts of your brain is somehow able to coordinate what is actually a complex task involving both cognitive and motor functions , guiding you down the right path and moving your legs while you 're getting dinner figured out . but perhaps the most interesting thing about spontaneous brain function is its involvement in one of the most mysterious and poorly understood phenomena of our bodies : sleep . you may shut down and become inactive at night , but your brain does n't . while you sleep , ongoing spontaneous activity gradually becomes more and more synchronized , eventually developing into large , rhythmic neural oscillations that envelop your brain . this transition to the more organized rhythms of sleep starts with small clusters of neurons tucked in the hypothalamus . despite their small number , these neurons have a huge effect in turning off brainstem regions that normally keep you awake and alert , letting other parts , like the cortex and thalamus , slowly slip into their own default rhythms . the deeper we fall into sleep , the slower and more synchronized this rhythm becomes , with the deepest stages dominated by large amplitude , low frequency delta waves . but surprisingly , in the middle of this slow wave sleep , the brain 's synchronized spontaneous activity repeatedly transitions into the sort of varied bursts that occur when we 're wide awake . this is the sleep stage known as rem sleep , where our eyes move rapidly back and forth as we dream . neuroscientists are still trying to answer many fundamental questions about sleep , such as its role in rejuvenating cognitive capacity , cellular homeostasis , and strengthening memory . and more broadly , they are exploring how it is that brain can accomplish such important and complex tasks , such as driving , or even breathing , without our awareness . but for now , until we are better able to understand the inner workings of their spontaneous functioning , we need to give our brains credit for being much smarter than we ourselves are .
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most of its activities are ones you 'd never be aware of , unless they suddenly stopped . the brain is made up of billions of neurons , and trillions of connections . neurons can be activated by specific stimuli or thoughts , but they are also often spontaneously active .
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the brain is made up of _____
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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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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 .
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many people are surprised to learn that insects are animals . think of your favorite animal and list the traits and characteristics that it has in common with an insect .
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translator : andrea mcdonough reviewer : bedirhan cinar every human being starts out the same way : two cells , one from each parent , found each other and became one . and that one cell reproduced itself , dividing , dividing and dividing until there were 10 trillion of them . do you realize there 's more cells in one person 's body than there are stars in the milky way ? but those 10 trillion cells are n't just sitting there in a big pile . that would make for a pretty boring human being ! so what is it that says a nose is a nose , and toes is toes ? what is it that says this is bone and this is brain and this is heart and this is that little thing in the back of your throat you can never remember the name of ? everything you are or ever will be made of starts as a tiny book of instructions found in each and every cell . every time your body wants to make something , it goes back to the instruction book , looks it up and puts it together . so how does one cell hold all that information ? let 's get small . i mean , really small -- smaller than the tip of a sewing needle . then we can take a journey inside a single cell to find out what makes up the book of you , your genome . the first thing we see is that the whole genome , all your dna , is contained inside its own tiny compartment , called the nucleus . if we stretched out all the dna in this one cell into a single thread , it would be over 3 feet long ! we have to make it fit in a tiny compartment that 's a million times smaller . we could just bunch it up like christmas lights , but that could get messy . we need some organization . first , the long thread of dna wraps around proteins clustered into little beads called nucleosomes , which end up looking like a long , beaded necklace . and that necklace is wrapped up in its own spiral , like an old telephone cord . and those spirals get layered on top of one another until we get a neat little shape that fits inside the nucleus . voilà ! three feet of dna squeezed into a tiny compartment . if only we could hire dna to pack our suitcases ! each tiny mass of dna is called a chromosome . the book of you would have 46 chapters , one for each chromosome . twenty-three chapters of your book came from your mom , and 23 chapters came from your dad . two of those chapters , called `` x '' and `` y , '' determine if you 're male , `` xy , '' or female , `` xx . '' put them together , and we get two almost identical but slightly different sets of 23 chapters . the tiny variations are what makes each person different . it 's estimated that all the chapters together hold about 20,000 individual instructions , called genes . written out , all those 20,000 instructions are 30 million letters long ! if someone were writing one letter per second , it would take them almost an entire year to write it once . it turns out that our genome book is much , much longer than just those 30 million letters -- almost 100 times longer ! what are all those extra pages for ? well , each page of instructions has a few pages of nonsense inserted that have to be taken out before we end up with something useful . the parts we throw out , we call introns . the instructions we keep , we call exons . we can also have hundreds of pages in between each gene . some of these excess pages were inserted by nasty little infections in our ancestors , but some of them are actually helpful . they protect the ends of each chapter from being damaged , or some help our cells find a particular thing they 're looking for , or give a cell a signal to stop making something . all in all , for every page of instructions , there 's almost 100 pages of filler . in the end , each of our books ' 46 chapters is between 48 and 250 million letters long . that 's 3.2 billion letters total ! to type all that copy , you 'd be at it for over 100 years , and the book would be over 600,000 pages long . every type of cell carries the same book , but each has a set of bookmarks that tell it exactly which pages it needs to look up . so a bone cell reads only the set of instructions it needs to become bone . your brain cells , they read the set that tells them how to become brain . if some cells suddenly decide to start reading other instructions , they can actually change from one type to another . so every little cell in your body is holding on to an amazing book , full of the instructions for life . your nose reads nose pages , your toes read toes pages . and that little thing in the back of your throat ? it 's got its own pages , too . they 're under `` uvula . ''
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put them together , and we get two almost identical but slightly different sets of 23 chapters . the tiny variations are what makes each person different . it 's estimated that all the chapters together hold about 20,000 individual instructions , called genes .
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though all humans start off the same way , give a brief explanation about what makes us all so different .
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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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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 .
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how can we plot √17 on the number line ?
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cities are a big deal : we pretty much all have to live in them ; we should try hard to get them right . so few cities are nice ; very , very few out of many thousands are really beautiful . embarrassingly , the more appealing ones tend to be old , which is weird because we 're mostly much better at making things now : cars , planes , or phones . why not , then , cities ? it 's crazy to settle for this and to leave something so important to chance . we need to get more scientific and identify the principles that determine how a city gets to be pretty or ugly . it 's not a mystery why we like some cities so much better than others . this is a manifesto about how to make attractive cities . there are six fundamental things a city needs to get right . 1 . not too chaotic ; not too ordered one of the things we really love in cities is order . order means balance , symmetry and repetition ; it means the same thing happening again and again , and the left side matching the right side . order is one of the reasons so many people love paris . but most cities are a complete mess . when it 's a mess , it seems like no one is in charge . and that 's worrying . it 's horrible when everything is jumbled up . a pitched roof next to a flat roof , a stark geometrical box next to a muddled car park , high rise towers that look as if they 've been placed at random , like teeth in a gaping mouth . we generally have an itch to straighten things out , and when we ca n't , it 's frustrating . the same urge is there when we look at cities . often , it 's not skyscrapers that we mind in the city , it 's skyscrapers that have been dumped without planning , like they are increasingly in london , whereas new york or chicago shows the ordered way that we love . however , you have to keep something else in mind : excessive order can be just as much of a problem . too much regularity can be soul destroying . too much order feels rigid and alien . it can be bleak , relentless , and harsh . so the ideal we 're seeking is variety and order . this is the idea in a square in telč in the czech republic : where every house is the same width and height but within that ordered pattern , every house has been allowed freedom at the level of form and colour or in java-eiland in amsterdam where the pattern is quite strict : each house has the same height and width , the color range is restricted , but within this grid , each unit is completely individual . we 're perfectly in the middle between chaos and boringness here . and that 's what humans adore . that 's what more and more cities should have : order and variety . so as a general rule : too much mess , and it 's off putting , but too much simple order , and it 's boring . what we crave it 's organized complexity which you can see as much here : as here : now , for the second thing that makes cities beautiful : they have to have visible life . there are streets that are dead and streets that are alive and in general , we crave the live ones . this is a live street in hong kong . this is a live scene in venice . in the 18th century , the painter canaletto specialized in pictures of cities everyone loved because they 're full of life . there 's always plenty going on . in this painting we can see a stonemason 's yard . the work sheds are rough , but they 're charming . it 's fascinating to see what people are up to . how do they load those huge blocks onto the gondolas ? the life of the city is on display , and we 're primed to love this . contrast this with dead streets of many modern cities . today , the places where a lot of the work gets done look dull and dead . they 're spaced out along huge highways , and you never go there unless you happen to work there yourself because there 's nothing to see . and most office buildings are brutally anonymous ; the people inside might be working in all sorts of fascinating stuff , but we just do n't know , and it 's disorienting and cold . the street levels are dead . contrast this with the streets we all love , where you can see things going on : a bakery , a cobbler 's shop , and markets selling carpets , a burger bar , a bookshop ; these are streets we love because they 're full of life . more and more , in modern cities , we 've hidden life away . we have lots of dead sheds , and dead towers , connected up by dead motorways where you can barely glimpse your fellow humans . rather than the old alleyways where you can see people at work , look them in the eye as they walk down the road and feel connected to others . modern planners have become obessed by hiding technology rather than trying to make it nice to look at . today we'de be outraged if we heard a huge pipeline was gon na be slapped across a lovely river ; we 'd be up in arms ! but we book trips to go and see the roman pont du gard in southern france . that 's because it 's built for beauty and practicality . we think it 's the pipe we hate . it 's not . it 's just the ugliness . so let 's make sure our streets are full of life , full of people doing stuff you can see through the windows . that 's what make certain cities so attractive to walk along : the work is on show , the people are proud of what they 're doing and happy to let the world notice and appreciate the practical side of things . there 's a third principle of good cities : they are compact . in the past , being able to be alone or just with your partner or family , was at first , a huge achievement . only the largest class , the poor , lived huddled together and it was horrid . as soon as people had money , they wanted to move out , and have their own plots . through the later decades of 20th century , more and more people tucked themselves away in a private realm . and it 's been a disaster . it 's become deadly , cold , and boring , and very , very wasteful on the environment . a compact city like barcelona swallows a fraction of the energy of a sprawling one like phoenix , in arizona . we 've built a world of endless dead dormitory suburbs connected by sterile wide motorways all because we labor under the false impression that we want to be far away from other people . but in fact it 's wonderful to have the balancing moderating influence of living close to other people in uplifting surroundings . that 's why we need tightly packed , well-ordered cities with lots of squares in public places in which we can hang out . all the most beautiful compact cities have squares . yet , the art of the square has gone into terrible decline . we keep promoting the invention of mobile phones , but no one 's built a good square anywhere on this planet for decades . it 's not rocket science though . look at the piazza di santa maria in trastevere , rome . it 's a public place , but intimate and closed enough to feel like an extension of your home . lounging about here , having a coffee or a beer , reading a paper , you get to be around other people , their moderating , cheering affect is restoring . it takes you away from the over intense , couple obsessed atmosphere of the home . there 's an art to a good square : it should be neither too big nor too small , anything over 30 meters in diameter starts become too large by which we mean : the individual become overly small relative to the space around them , creating a sense of alienation and dislocation . in a good square you should be able to see the face of a person across the square , you could if need be hail someone walking on the other side . the ideal square must offer a feeling of containment , but not claustrophobia . there 's another principle of good cities to do with orientation and mystery . by definition , cities are huge , but the cities that a lot of people love also have lots of little back streets and small lanes where you can feel cozy and get a bit lost . we 're drawn to the sense of mystery and enclosure that these streets offer . it 's actually lovely to get a bit lost . a warren of alleyways can feel homely and intimate . at cartagena , in colombia , the balconies nearly touch across the street- you can see your neighbors having breakfast , you know when they 've gone to bed , what time the children do their homework on a sunday evening . the fact that everyone is little bit on display a lot of the time tends to make people nicer . they do n't shout at each other quite so much . they put flowers on the table more often . we like it , but we forget that we do , and we do n't quite know how to ask for it . modern planners and developers give us maximum privacy because they suppose that 's what we all want , and because they insist that cars and lorries , which like a lot more space than people , are the most important things in the world . of course we need balance between small streets and big ones . necessarily , cities are large . we love small streets , but they 're a nightmare when you have to go any distance . so the ideal is to have big boulevards , grand , wide straight places , and also little warrens of streets . we need cities that offer us two important pleasures : the pleasures of mystery and the pleasures of orientation . let 's think about scale now . modern cities are all about big things . joseph campbell once wrote : `` if you want to see what a society really believes in , look at what the biggest buildings on the horizon are dedicated to '' . the biggest most prominent things tell us about the actual , rather than admitted priorities of a society . we do n't collectively say we worship sports shoe corporations , tax specialists , the oil industry , and pharmaceuticals . our cities , however , tell another story . they 're full of enormous towers devoted to just these things . that is a bit depressing . as humans , we do n't mind things being big , per se , we do n't mind being humbled , so long as the things we are bowing to deserve homage , like a beautiful mosque , or a cathedral , or a museum . but we 've allowed our cities to be hijacked by aggressive commercial interests , by towers that honor not god , or love , or humanity , but pizza corporations and hedge funds . they exist because we 've made a big dumb collective mistake : we focused on who owns land , but we do n't think about who owns space , who has air rights . and in the end , who has air rights determines what you can see from your window . we suggest that the ideal height for any city block is five stories high . no more . above that people start to feel small , insignificant , and trivial . so we say : cut down those towers and pack everything into five stories . make it dense , compact , and tight , like they do in some parts of berlin , amsterdam , london , and paris , the bits we love . of course , occasionally there can be a huge building , but let 's keep it for something really special , something all of humanity can love . towers have to be worthy of their prominence , they must be aligned with our best ambitions and long-term needs . finally , make it local . somethings should be the same everywhere . we do n't expect there to be a uniquely venezuelan telephone or a distinctively icelandic bicycle . but , we do n't want buildings to look the same everywhere . it 's hugely disappointing when you fly somewhere for hours , land , and feel you could be anywhere . the problem is n't just that we like a bit of variation for it 's own sake ; because of climate , history and social traditions , each society really does have different needs , different strengths and weaknesses . there are many distinct styles of happiness ; many good and varied ways of conductive and collective life . the sameness of cities is a problem because it reveals how far each of us must be from engaging with an specific character of it 's own place . it 's like wearing the same clothes in all climates , or speaking exactly the same way irrespective of who you 're talking to . cities need to have strong characters connected to the use of distinctive local materials and forms . the pale sandstone , of millbrae crescent in glasgow 's south side , is a local material , a medium grained , carboniferous , blond sandstone- formed when the scottish landmass lay near the equator . or around cambridge , brick from the local yellowish gault clay is a major traditional material . or think of the way the great australian architect , glenn murcutt , found ways to put up buildings that reflected the distinctive character australian life . so the law should be : do n't make your city from buildings that could be just anywhere ; find a style of architecture that reflects what makes your location specific . the obstacles to building beautiful cities and not economic . collectively , we 've got enough money . we face two main problems : firstly , an intellectual confusion around beauty , and secondly , lack of political will . the intellectual confusion is : we think no one has a right to say what 's beautiful and what 's ugly ; we get worried about who decides ; we think beauty is subjective , so surely no one should say anything about it . it 's a very understandable qualm , but it 's horribly useful to greedy property developers . it 's such a relief to these people to learn that there is no such thing as beauty ; it means they can get away with murder . we may not agree to the very last point about what a beautiful city is , but we know an ugly one when we see it . no one 's ever willingly taken holiday in frankfurt-on-main or birmingham , and there are good reasons for this to do with an objective sense of beauty . so let 's stop being dangerously relativistic about this . yes ! there is such a thing as beauty . sydney and san francisco and bath and bordeaux have it and most other places do n't . the proof lies in the tourist statistics . let 's not just say that beauty is in the eye of the beholder ; that 's just a gift to the next wealthy idiot who wants to put up a horrible tower . the other obstacle is a lack of political will . we 've abandoned the design of cities to the greedy rich . we 've given up believing in democracy . we 've faced and have lost the battle between the public good and commercial opportunism . there will always be a greedy , slick lobby fighting for ugly development , but we can say no . beautiful cities have only ever been created when governments impose strict and ambitious regulations to keep the greedy , private guys in check . think of edinburgh 's amazing new town , which only got of the ground because the government established clear rules to keep developers in check . they were precise legislation detailing heights for buildings , quality of finish , the width of pavements , and a character of the skyline . that 's the only way you get beauty . they did n't leave it to the free market . do that , and you will have chaos . when governments give up on beauty , people start to hate all building . we become collectively despondent . we think we hate all building , and that we ca n't create beautiful places we get obsessed by restorations and opposed to anything new , which is wrong because we need places to live . humanity has n't put up a single beautiful city since about 1905 . when venice was built , no one regretted the lagoons that had been swallowed up . the goal of building , should be to put up things that do n't leave us regretting the nature that 's been lost because the architecture is every bit the equal of the designs of nature . we can create more beautiful cities , but we have to confront opportunistic developers and our own intellectual confusions . governments can only create beauty if they have enough public backing . political will is ultimately about what all of us , the electorate , are asking for . that 's why we made this film and hope to awaken you to your power as citizens to help legislate for beautiful cities in the future these are the six rules . now , it 's time to fight to put them in action .
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towers have to be worthy of their prominence , they must be aligned with our best ambitions and long-term needs . finally , make it local . somethings should be the same everywhere .
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what elements of a city make it appealing to you ?
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many people in the united states and latin america have grown up celebrating the anniversary of christopher columbus 's voyage , but was he an intrepid explorer who brought two worlds together or a ruthless exploiter who brought colonialism and slavery ? and did he even discover america at all ? it 's time to put columbus on the stand in history vs. christopher columbus . `` order , order in the court . wait , am i even supposed to be at work today ? '' cough `` yes , your honor . from 1792 , columbus day was celebrated in many parts of the united states on october 12th , the actual anniversary date . but although it was declared an official holiday in 1934 , individual states are n't required to observe it . only 23 states close public services , and more states are moving away from it completely . '' cough `` what a pity . in the 70s , we even moved it to the second monday in october so people could get a nice three-day weekend , but i guess you folks just hate celebrations . '' `` uh , what are we celebrating again ? '' `` come on , your honor , we all learned it in school . christopher columbus convinced the king of spain to send him on a mission to find a better trade route to india , not by going east over land but sailing west around the globe . everyone said it was crazy because they still thought the world was flat , but he knew better . and when in 1492 he sailed the ocean blue , he found something better than india : a whole new continent . '' `` what rubbish . first of all , educated people knew the world was round since aristotle . secondly , columbus did n't discover anything . there were already people living here for millennia . and he was n't even the first european to visit . the norse had settled newfoundland almost 500 years before . '' `` you do n't say , so how come we 're not all wearing those cow helmets ? '' `` actually , they did n't really wear those either . '' cough `` who cares what some vikings did way back when ? those settlements did n't last , but columbus 's did . and the news he brought back to europe spread far and wide , inspiring all the explorers and settlers who came after . without him , none of us would be here today . '' `` and because of him , millions of native americans are n't here today . do you know what columbus did in the colonies he founded ? he took the very first natives he met prisoner and wrote in his journal about how easily he could conquer and enslave all of them . '' `` oh , come on . everyone was fighting each other back then . did n't the natives even tell columbus about other tribes raiding and taking captives ? '' `` yes , but tribal warfare was sporadic and limited . it certainly did n't wipe out 90 % of the population . '' `` hmm . why is celebrating this columbus so important to you , anyway ? '' `` your honor , columbus 's voyage was an inspiration to struggling people all across europe , symbolizing freedom and new beginnings . and his discovery gave our grandparents and great-grandparents the chance to come here and build better lives for their children . do n't we deserve a hero to remind everyone that our country was build on the struggles of immigrants ? '' `` and what about the struggles of native americans who were nearly wiped out and forced into reservations and whose descendants still suffer from poverty and discrimination ? how can you make a hero out of a man who caused so much suffering ? '' `` that 's history . you ca n't judge a guy in the 15th century by modern standards . people back then even thought spreading christianity and civilization across the world was a moral duty . '' `` actually , he was pretty bad , even by old standards . while governing hispaniola , he tortured and mutilated natives who did n't bring him enough gold and sold girls as young as nine into sexual slavery , and he was brutal even to the other colonists he ruled , to the point that he was removed from power and thrown in jail . when the missionary , bartolomé de las casas , visited the island , he wrote , 'from 1494 to 1508 , over 3,000,000 people had perished from war , slavery and the mines . who in future generations will believe this ? ' '' `` well , i 'm not sure i believe those numbers . '' `` say , are n't there other ways the holiday is celebrated ? '' `` in some latin american countries , they celebrate the same date under different names , such as día de la raza . in these places , it 's more a celebration of the native and mixed cultures that survived through the colonial period . some places in the u.s. have also renamed the holiday , as native american day or indigenous people 's day and changed the celebrations accordingly . '' `` so , why not just change the name if it 's such a problem ? '' `` because it 's tradition . ordinary people need their heroes and their founding myths . ca n't we just keep celebrating the way we 've been doing for a century , without having to delve into all this serious research ? it 's not like anyone is actually celebrating genocide . '' `` traditions change , and the way we choose to keep them alive says a lot about our values . '' `` well , it looks like giving tired judges a day off is n't one of those values , anyway . '' traditions and holidays are important to all cultures , but a hero in one era may become a villain in the next as our historical knowledge expands and our values evolve . and deciding what these traditions should mean today is a major part of putting history on trial .
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and did he even discover america at all ? it 's time to put columbus on the stand in history vs. christopher columbus . `` order , order in the court .
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what was columbus trying to find in his expedition ?
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translator : andrea mcdonough reviewer : bedirhan cinar once upon a time in the magical and very round land of pi , there lived six swashbuckling musketeers . there names were parentheses , exponents , multiplication , division , addition , and subtraction . but each was known best by his or her mark : the two hands ready to catch a fly of parentheses , the small and raised digits of exponents , the mighty x of multiplication , slash of division , plus of addition , and , well , you can guess the symbol by which little subtraction was best known . the land of pi was not necessarily the most peaceful place , and that 's why the numbers of the kingdom needed the musketeers . the land of pi had been ruled by the numbers as anarcho-syndicalist commune , each number with a vote , but , one powerful number from what we 'll call the imperial senate , engineered a war between some robot things and the knights of the kingdom , and then installed himself as supreme emperor , and then puff the magic digit dragon ate him , and a princess or two , and , well , all the other numbers in the land of pi actually . it was kind of a big day . anyway , the musketeers were called to action to save the land of pi from the voracious dragon . they rode towards him on their valiant steeds and attacked . first multiplication , then parentheses , but that did n't work . the dragon continued eating people . so addition tried , but was thrown aside . exponents leaped at the beast and was quickly squashed . nothing was working . the musketeers huddled and formulated a plan . they would attack in sequence , but who should go first ? they bickered for a while , the dragon ate a few more princesses , and then they finally agreed . they jumped into the first , smallest parentheses inside the great puff the digit dragon . parentheses pointed out where to work first and protected exponents , multiplication , division , addition , and subtraction while they diced and sliced . first here , then , move over there , then there . look out ! there 's another set ! parentheses pointed and exponents took the lead . then , it was multiplication , division , addition , and subtraction , each in turn , always the same order . p-e-m-d-a-s when they finished that set , they went to another , and another , always working inside the parentheses in pemdas order . pop ! pop ! pop ! pop ! pop ! pemdas , there is another spot ! do n't forget , there can be parentheses inside parentheses . there 's one ! and that tricky exponent . there we go ! finally , the pemdas musketeers had whittled puff down to his last fearsome roar . but , having vanquished puff the magic digit dragon , all the empire 's numbers sprang again from this tiny little number one , and they all lived happily ever after . except for the emperor number , which they threw into the mouth of an ancient nesting creature in the desert . the end .
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there names were parentheses , exponents , multiplication , division , addition , and subtraction . but each was known best by his or her mark : the two hands ready to catch a fly of parentheses , the small and raised digits of exponents , the mighty x of multiplication , slash of division , plus of addition , and , well , you can guess the symbol by which little subtraction was best known . the land of pi was not necessarily the most peaceful place , and that 's why the numbers of the kingdom needed the musketeers .
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solve this problem : ( 5-6 ) x 46 - 8^6 / 24
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[ pbs intro ] this episode is supported by 23 and me a long time ago a guy built a tomb out of rocks so he could live in it after he died and not be dead . his son was like “ hey that ’ s cool ” so he built one too.. then his son was like “ me too ” so he made a third and they were all buried there . and that ’ s how we got this . the pyramids of giza . how did people who hadn ’ t even invented the wheel build these things , and… why ? they ’ re so big ! they ’ re so precise ! they ’ re so directionally oriented ! they ’ re so mysterrrrrrious . at first glance they really do look out-of-this world . thing is , the pyramids are much older than you probably think . they were already ancient history to people in ancient history , which led to some pretty wild theories about how they came to be . but pyramid technology didn ’ t just show up out of nowhere . it was the end product of centuries of scientific and cultural evolution , of people… figuring it out . and it definitely wasn ’ t aliens . [ open ] early on , egyptians buried their dead like we do . the desert naturally mummified some corpses , which influenced their religious beliefs : you need to preserve the body to reach the afterlife , and when you get there you ’ ll need all your stuff . rich people ’ s graves had nicer stuff , and they needed to protect their afterlife investment . first with simple mounds , and later with mud brick “ eternal houses ” . then a king named djoser was like “ why have one little mud mastaba when i can have six stone mastabas in a stack ? ” so he stacked six stone mastabas like a mastaba boss and the age of the pyramids had begun . this was literally the first time humans had piled stone this high . egyptians knew totally vertical walls got less stable as they got taller , so djoser ’ s architect stacked bricks at an incline and let gravity do the work . step pyramid achieved ! why pyramids and not other shapes ? if you want to make a big pile of blocks , a pyramid gets you the most stability for the least material . a third of the way up , you ’ ve already laid two-thirds of your stone . halfway , you ’ ve placed more than 80 % . next comes sneferu , mr. pyramid . he built his own step pyramid , but then decided he wanted a smooth one instead , so they started on a second . no one had ever built one of those before , so they made some mistakes . for starters , they built it on sand , which is soft , they laid blocks carelessly , and it was too steep , so halfway through they changed the slope and ended up with this . sneferu was like “ you ’ re not burying me in that ” , so he ordered a third pyramid ! only this time they built a solid foundation , laid the stones in horizontal rows , and precision cut the edges . sneferu ’ s motto ? if at first you don ’ t succeed , try again , and then try again one more time . sneferu had experimented his way to a blueprint for building awesome pyramids the great pyramid at giza , built by his son khufu , took that blueprint to the next level . khufu ’ s pyramid remained the tallest structure on earth for almost 4000 years , until some church tower in the year 1311 , which fell down , so it was tallest again until this radio antenna was finished in 1889 . khufu ’ s son khafre built his pyramid right next to dad ’ s , and he didn ’ t stop innovating . instead of leveling the entire 46,000 square meter footprint , he built his pyramid over a natural stone mound and only leveled the outer edge , which was less work , duh ! it ’ s 3 meters shorter than his dad ’ s , but this higher ground creates the illusion that khafre ’ s pyramid is taller . kids , amirite ? but even these seemingly perfect pyramids weren ’ t without mistakes . khafre ’ s had a slight twist near the top in order to make the edges line up evenly . what ’ s remarkable is egypt ’ s biggest stone pyramids were the product of just three human generations , but those were generations full of trial and error . pyramid building continued for nearly 700 years , and like any product , efficiency started to win out over quality . precision-cut cores were replaced by rough-cut blocks . kings still wrapped their pyramids in fine white limestone , but over the next thousand years that was removed by stone stealers and rock robbers , leaving the cheaply-produced cores to collapse into rubble , which is probably why you ’ ve never heard of them . ironically , the kings were probably disappointed by the whole afterlife thing , but the pyramids themselves have proven to be surprisingly resilient . ancient is not a synonym for stupid . the world ’ s first skyscrapers were tombs , and just like our own buildings , they didn ’ t spring up out of nowhere , they were the product of centuries of engineering trial and error . go back 500 years and show someone a smartphone and they ’ d probably think you were a wizard . but when we look back from the present at the ideas and failures along the way , we see that it ’ s not magic at all ! it ’ s science . and if you still think aliens did it , you ’ re in de-nile . you know , the river . stay curious .
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khafre ’ s had a slight twist near the top in order to make the edges line up evenly . what ’ s remarkable is egypt ’ s biggest stone pyramids were the product of just three human generations , but those were generations full of trial and error . pyramid building continued for nearly 700 years , and like any product , efficiency started to win out over quality .
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egypt 's great stone pyramids were the work of how many generations of egyptians ?
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there have been many different things written and said about marriage . from the sweetly inspirational to the hilariously cynical . but what many of them have in common is that they sound like they express a universal and timeless truth , when in fact nearly everything about marriage , from its main purpose to the kinds of relationships it covers to the rights and responsibilities involved , has varied greatly between different eras , cultures and social classes . so , let 's take a quick look at the evolution of marriage . pair bonding and raising children is as old as humanity itself . with the rise of sedentary agricultural societies about 10,000 years ago , marriage was also a way of securing rights to land and property by designating children born under certain circumstances as rightful heirs . as these societies became larger and more complex , marriage became not just a matter between individuals and families , but also an official institution governed by religious and civil authorities . and it was already well established by 2100 b.c . when the earliest surviving written laws in the mesopotamian code of ur-nammu provided many specifics governing marriage , from punishments for adultery to the legal status of children born to slaves . many ancient civilizations allowed some form of multiple simultaneous marriage . and even today , less than a quarter of the world 's hundreds of different cultures prohibit it . but just because something was allowed does n't mean it was always possible . demographic realities , as well as the link between marriage and wealth , meant that even though rulers and elites in ancient mesopotamia , egypt and israel had multiple concubines or wives , most commoners could only afford one or two tending towards monogamy in practice . in other places , the tables were turned , and a woman could have multiple husbands as in the himalayan mountains where all brothers in a family marrying the same woman kept the small amount of fertile land from being constantly divided into new households . marriages could vary not only in the number of people they involved but the types of people as well . although the names and laws for such arrangements may have differed , publicly recognized same-sex unions have popped up in various civilizations throughout history . mesopotamian prayers included blessings for such couples , while native american two-spirit individuals had relationships with both sexes . the first instances of such arrangements actually being called `` marriage '' come from rome , where the emperors nero and elagabalus both married men in public ceremonies with the practice being explictly banned in 342 a.d . but similar traditions survived well into the christian era , such as adelphopoiesis , or `` brother-making '' in orthodox churches , and even an actual marriage between two men recorded in 1061 at a small chapel in spain . nor was marriage even necessarily between two living people . ghost marriages , where either the bride or groom were deceased , were conducted in china to continue family lineages or appease restless spirits . and some tribes in sudan maintain similar practices . despite all these differences , a lot of marriages throughout history did have one thing in common . with crucial matters like property and reproduction at stake , they were way too important to depend on young love . especially among the upperclasses , matches were often made by families or rulers . but even for commoners , who had some degree of choice , the main concern was practicality . the modern idea of marriage as being mainly about love and companionship only emerged in the last couple of centuries . with industrialization , urbanization and the growth of the middle class more people became independent from large extended families and were able to support a new household on their own . encouraged by new ideas from the enlightenment , people began to focus on individual happiness and pursuits , rather than familial duty or wealth and status , at least some of the time . and this focus on individual happiness soon led to other transformations , such as easing restrictions on divorce and more people marrying at a later age . so , as we continue to debate the role and definition of marriage in the modern world , it might help to keep in mind that marriage has always been shaped by society , and as a society 's structure , values and goals change over time , its ideas of marriage will continue to change along with them .
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and this focus on individual happiness soon led to other transformations , such as easing restrictions on divorce and more people marrying at a later age . so , as we continue to debate the role and definition of marriage in the modern world , it might help to keep in mind that marriage has always been shaped by society , and as a society 's structure , values and goals change over time , its ideas of marriage will continue to change along with them .
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why would the authorities in an agricultural society have official laws governing marriage ?
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many modern musical instruments are cumbersome or have a lot of parts . some need a stand or a stool . but the cajon is a drum , a stand and a seat all in one convenient box . and this simplicity may be key to its journey across continents and cultures to become one of the most popular percussion instruments in the world today . the cajon 's story begins in west africa , whose indigenousness people had rich musical traditions centered on drumming and dancing . when many of them were captured and brought to the americas as slaves , they brought this culture with them , but without their native instruments , they had to improvise . african slaves in coastal peru did n't have the materials or the opportunity to craft one of their traditional drums such as a djembe or a djun djun . but what they did have were plenty of shipping crates . not only were these readily accessible , but their inconspicuous appearance may have helped get around laws prohibiting slaves from playing music . early peruvian cajons consisted of a simple box with five thick wooden sides . the sixth side , made of a thinner sheet of wood , would be used as the striking surface , or more commonly known as the tapa . a sound hole was also cut into the back to allow the sound to escape . as an afro-peruvian culture developed , and new forms of music and dance , such as zamacueca , festejo and landó were born , the cajon became a dedicated musical instrument in its own right . early modifications involved simply bending the planks of the box to tweak the sound , and when abolition of slavery introduced the cajon to a broader population , more improvisation and experimentation soon followed . perhaps the person most responsible for introducing the cajon to european audiences was spanish flamenco guitarist paco de lucía . when touring in peru in 1977 , he and his percussionist rubem dantas discovered the cajon and brought it back to spain , recognizing its potential for use in flamenco music . by stretching guitar strings along the inside of the tapa , the flamenco musicians were able to create a buzz-like snare sound . combined with the regular base tone , this gave the cajon a sound close to a basic drum set . the cajon quickly caught on , not only becoming standard in flamenco , but being used in genres like folk , jazz , blues and rock . today , many specialized cajons are manufactured , some with adjustable strings , some with multiple playing surfaces , and some with a snare mechansim . but the basic concept remains the same , and the story of the cajon shows that the simplest things can have the most amazing potential when you think outside and inside the box .
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the sixth side , made of a thinner sheet of wood , would be used as the striking surface , or more commonly known as the tapa . a sound hole was also cut into the back to allow the sound to escape . as an afro-peruvian culture developed , and new forms of music and dance , such as zamacueca , festejo and landó were born , the cajon became a dedicated musical instrument in its own right .
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what modifications would you make to the cajon to change or add to its sound ?
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it was a night like any other night , except here i was climbing the platonic peaks like romeo on a second date . ( ugh ) i was there for the dame . she had eyes like imaginary numbers and curves that went on forever . said she wanted to go home . said i could help . said the pay was good . did n't say anything about climbing a ... voice : `` who 's there ? '' manny brot : `` manny brot , private eye . '' voice : `` what are you doing here ? '' `` a pretty number sent me to find a stolen dingus . '' voice : `` well , to enter the cave , you must answer my riddles three . '' what was it with riddles , and why do they always come in threes ? `` is it an egg ? '' `` no . why would it be an egg ? '' `` it 's usually an egg . '' `` what can i hold in my hand , but has zero area ? '' `` is it a dodo egg ? '' `` it 's not an egg ! '' i took out the rock that had nearly brained me before and gave it a hard ponder . the size of the rising bump on my conk said to me that this thing had area , and a lot of it . but what if i carved out a triangle from this side here ? as any mook could see , this triangle had a quarter of the area of the full triangle . i did the same thing again with each of the smaller triangles . again , a quarter of the remaining area -- gone . and i just kept going . after an infinite number of cuts , i was satisfied that my triangle had zero area . a bounded shape with zero area . now , it 's not often that i surprise myself , but my own two mitts had created something crazy , and new . `` very good . ( ahem ) now , show me a shape with finite area , but an infinitely long perimeter . '' `` let me get this straight . if i want to make a snip in the border of this shape , smooth it out , and lay it on the ground ... `` `` it would go on for ... `` `` wait 'til i 'm through , and then you can talk . it would go on forever . '' `` are you through ? '' `` yeah . '' `` so show me that shape then . '' mmm ... i had n't been this stuck since the rubik 's cube fiasco of '58 . all the shapes i knew had perimeters . circles : 2πr . triangles : sum of their sides . what 's this ? an angle . an angle from heaven . what if i were to pinch each side , like so . a third of the way through , just so . and do it again , and again , and again . after each pinch , the perimeter got a third longer because where there had been three line segments , now there were four . as for the area , every pinch made more triangles , that 's true . but those triangles were getting smaller and smaller . you could say that the area was converging , approaching a fixed number , while the perimeter was just getting bigger and bigger , uncontrollably ballooning like an overindulgent birthday clown . after infinity pinches , flimflam , there it was : finite area , but infinite perimeter . now that is a piece of work . `` oh , you 're good . ( ahem ) riddle three : show me a picture that if i magnify it under my microscope , i 'll keep seeing the original picture , no matter how much i zoom in . '' `` you 're a strange little man . '' `` thank you . '' i was out of ideas , so i looked at my muse , my complex dora . voice : `` who 's the dame ? '' and then it hit me . `` she 's a heart breaker , my fractal femme fatale . will she do ? '' `` yes , she 'll do just fine . '' ( lightning ) it was dark , and at first i thought the cave was empty , but then i noticed : the box . the dame had played me like a triangle . she had told me she wanted to go home . ( lightning ) what she really wanted was to bring her home here . the fractals spread everywhere . most of them the same no matter how deep you looked at them , like dora 's mugshot . some had infinitely long perimeters , others were objects with no area or volume , all of them created through infinite repetition . so , you wanted to know what fractals are ? well , kid , they 're the stuff that dreams are made of . ( music )
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did n't say anything about climbing a ... voice : `` who 's there ? '' manny brot : `` manny brot , private eye . '' voice : `` what are you doing here ? ''
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what are the differences between the world before and after manny opens dora ’ s box ? what might that signify ?
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translator : andrea mcdonough reviewer : bedirhan cinar 9th of january , 2007 joshua bell , one of the greatest violinist in the world , played to a packed audience at boston 's stately symphony hall of 1,000 people where most seats went for more than $ 100 . he was used to full , sell-out shows . he was at the peak of his abilities and fame . three days later , joshua bell played to an audience of nobody ! well , maybe six people paused for a moment , and one child stopped for a while looking , as if he understood that something special was happening . joshua said of the experience , `` it was a strange feeling that people were actually ignoring me . '' joshua bell was playing violin in a subway station . `` at a music hall , i 'll get upset if someone coughs or if someone 's cell phone goes off , but here my expectations quickly diminished . i was oddly grateful when somebody threw in a dollar . '' what changed ? same music , on the same violin , played with the same passion and by the same man . why did people listen and then not listen ? aristotle would be able to explain . what does it take to persuade people ? 2,300 years ago , aristotle wrote the single most important work on persuasion , < i > rhetoric < /i > , the 3 means of persuasion : logos , ethos , and pathos . logos is that the idea makes sense from the audience 's point of view . this is usually different from the speaker 's point of view , so work needs to be done to make the idea relevant to the world view , the pains and the challenges of the listeners . a good argument is like good music . good music follows some rules of composition ; good arguments follow some rules of logic . it makes sense to the audience . ethos is reputation , what are you known for ; credibility , do you look and act professional ; trustworthy , are your motives clear , do you show the listener that you care about them as much as yourself ? authority is confidence plus a concise message , a clear , strong voice . pathos is the emotional connection . stories are an effective human tool for creating an emotional connection . there are moments where an audience is not ready to hear the message . a speaker must create the right emotional environment for their message . what changed ? why did people travel for miles to hear him play one night , and not even pause for moment to listen the next morning ? the answer is that ethos and pathos were missing . ethos the fact that the great concert hall hosts joshua 's concert transfers its trust to joshua . we trust the institution , we now trust joshua . the subway does not have our trust for musical talent , we do not expect to find great art , great music , or great ideas , so it confers no trust to joshua . pathos the concert hall is designed for an emotional bond between an audience and an artist , a subway platform is not . the hustle and movement and stress is just not conducive to the emotional connection needed between performer and listener . logos , ethos , pathos , the idea is nothing without the rest . this is what joshua bell learned on that cold , january day in 2007 . if you have a great idea , how do you build credibility and emotional connection ?
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what does it take to persuade people ? 2,300 years ago , aristotle wrote the single most important work on persuasion , < i > rhetoric < /i > , the 3 means of persuasion : logos , ethos , and pathos . logos is that the idea makes sense from the audience 's point of view .
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who wrote `` rhetoric : the three means of persuasion '' ?
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the victory of the underdog over the favored team . the last minute penalty shot that wins the tournament . the high-energy training montages . many people love to glorify victory on the playing field , cheer for favorite teams , and play sports . but here 's a question : should we be so obsessed with sports ? is playing sports actually as good for us as we make it out to be , or just a fun and entertaining pastime ? what does science have to say ? first of all , it 's well accepted that exercise is good for our bodies and minds , and that 's definitely true . exercising , especially when we 're young , has all sorts of health benefits , like strengthening our bones , clearing out bad cholesterol from our arteries , and decreasing the risk of stroke , high blood pressure , and diabetes . our brains also release a number of chemicals when we workout , including endorphins . these natural hormones , which control pain and pleasure responses in the cental nervous system , can lead to feelings of euphoria , or , what 's often called , a runner 's high . increased endorphins and consistent physical activity in general can sharpen your focus and improve your mood and memory . so does that mean we get just as much benefit going to the gym five days a week as we would joining a team and competing ? well , here 's where it gets interesting : because it turns out that if you can find a sport and a team you like , studies show that there are all sorts of benefits that go beyond the physical and mental benefits of exercise alone . some of the most significant are psychological benefits , both in the short and long term . some of those come from the communal experience of being on a team , for instance , learning to trust and depend on others , to accept help , to give help , and to work together towards a common goal . in addition , commitment to a team and doing something fun can also make it easier to establish a regular habit of exercise . school sport participation has also been shown to reduce the risk of suffering from depression for up to four years . meanwhile , your self-esteem and confidence can get a big boost . there are a few reasons for that . one is found in training . just by working and working at skills , especially with a good coach , you reinforce a growth mindset within yourself . that 's when you say , `` even if i ca n't do something today , i can improve myself through practice and achieve it eventually . '' that mindset is useful in all walks of life . and then there 's learning through failure , one of the most transformative , long-term benefits of playing sports . the experience of coming to terms with defeat can build the resilience and self-awareness necessary to manage academic , social , and physical hurdles . so even if your team is n't winning all the time , or at all , there 's a real benefit to your experience . now , not everyone will enjoy every sport . perhaps one team is too competitive , or not competitive enough . it can also take time to find a sport that plays to your strengths . that 's completely okay . but if you spend some time looking , you 'll be able to find a sport that fits your individual needs , and if you do , there are so many benefits . you 'll be a part of a supportive community , you 'll be building your confidence , you 'll be exercising your body , and you 'll be nurturing your mind , not to mention having fun .
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exercising , especially when we 're young , has all sorts of health benefits , like strengthening our bones , clearing out bad cholesterol from our arteries , and decreasing the risk of stroke , high blood pressure , and diabetes . our brains also release a number of chemicals when we workout , including endorphins . these natural hormones , which control pain and pleasure responses in the cental nervous system , can lead to feelings of euphoria , or , what 's often called , a runner 's high . increased endorphins and consistent physical activity in general can sharpen your focus and improve your mood and memory .
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exercising increases the rush of endorphins , which lead to feelings of :
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what gives the trumpet its clarion ring and the tuba its gut-shaking `` omm pah pah ? '' and what makes the trombone so jazzy ? the answer lies not in the brass these instruments are made of , but in the journey air takes from the musician 's lungs to the instrument 's bell . like any sound , music consists of vibrations traveling through air . instruments are classified based on how those vibrations are produced . percussion instruments are struck . string instruments are plucked or bowed . woodwinds have air blown against a reed or sharp edge . for brass instruments , however , the vibration come directly from the musician 's mouth . one of the first things a brass player must learn is to breathe in deeply , until every possible particle of air is crammed into the lungs . once all that air is inside , it must come out through the mouth , but there , an internal battle takes place as the musician simultaneously tries to hold their lips firmly closed while blowing enough air to force them open . the escaping air meets resistance from the lip muscles , forms an opening called the aperture and creates the vibration that brass players call `` the buzz . '' when a mouthpiece is held up to those vibrating lips , it slightly refines the buzz , amplifying the vibration at certain frequencies . but things get really interesting depending on what instrument is attached to that mouthpiece . a brass instrument 's body is essentially a tube that resonates with the air column blowing through it . the way that sound waves travel through this column forms a limited pattern of pitches known as the harmonic series , with notes spaced far apart at the lower end , but coming closer together as the pitch increases . the musician can alter the pitch of the note through slight contractions of the lips and alterations to air volume and speed . slower , warm sighing air produces lower pitches , and faster , cool , flowing air produces higher pitches in the series . but any single harmonic series has gaps where pitches are missing and the versatility of brass instruments lies in their ability to switch between multiple series . on instruments like the trumpet , valves can be lowered to increase the length of tubing the air travels through , while on a trombone , this is done by extending its slide . lengthening the tube stretches the vibrating air column , reducing the frequency of vibrations and resulting in a lower pitch . this is why the tuba , the largest brass instrument , is also the one capable of playing the lowest notes . so changing the instrument length shifts its harmonic series , while slight variations of the air flow and the player 's lips produce the different notes within it . and those notes finally emerge through the flared bell opening at the end . what started as a deep breath and a vibrating buzz on the lips has now been transformed into a bold and brassy tune . the musician 's skillful manipulation of every part of the process from lungs , to lips , to the mouthpiece , to the instrument itself creates an amazing palette of pitches that can be heard in musical genres across the globe . by harnessing the power of natural resonance in a flexible and controllable way , brass instruments are great examples of the fusion of human creativity with the physics of our world .
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woodwinds have air blown against a reed or sharp edge . for brass instruments , however , the vibration come directly from the musician 's mouth . one of the first things a brass player must learn is to breathe in deeply , until every possible particle of air is crammed into the lungs .
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explain how a brass musician can create various pitches with his/her instrument .
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so potassium metal is very reactive . one of my colleagues who used to work with it , described it as evil . so we 've come out behind the chemistry department . in the open air . to try and do a re-take of the potassium video . the last sample of potassium was very very small , maybe 500mg . it will react , it is so reactive that if you have it in a box with argon , so that it ca n't get oxygen from anywhere , it will take the oxygen out of paper . which is , paper is a compound of carbon , hydrogen and oxygen . and it can extract this . it 's a reactive element . it 's used in our body all the time . we have like , lots of potassium floating around . and we 've got some samples here , about a gram , maybe a gram and a half of each . it 's a pretty big chunk of potassium this . ready ? yeah . very satisfying reaction . after completing the 100 meters dash ... like sodium it'ss quite a low melting point metal . and if you mix sodium and potassium together , to make so called sodium potassium amalgam , it 's called nak , by those who work in the trade , na for sodium , k for potassium . nak is a liquid at room temperature . it looks a bit like mercury . a silver liquid . it 's very light . and i never played with it , but people say that if you try and drop it on the floor , it will burst into flames before it hits the floor , because it reacts with the water in the air . today i 'm going to show you how to make a potassium mirror . we will just fish out a nice little bit of potassium . it 's stored under mineral oil , because it reacts with water over time . so it 's quite malleable stuff . it 's a little bit like if you imagine cutting blu tac . it 's quite soft . and it starts you see , it 's starting to go a little bit already . tarnishing a wee bit . so we can just manipulate it like that , and we are gon na pop it into our ampule , and we are gon na evacuate it now . i 'm gon na remove all of the atmosphere , from this ampule . ok , we 've done that because the , the boiling point of potassium under one atmosphere is over 700 degrees c. which is pretty high . it 's too high for the glass to tolerate . if i heated it up to that temperature the glass would start to soften , melt . so by evacuating it , we remove all of the atmosphere which is keeping the boiling point as high as it is . so it lowers the boiling point much lower . so it starts to drop into the range of water . ok so we are just going to the blue flame , which is the nice hot flame . and we just keep on gently warming it . and at some point , it will melt . just enough that you will start to see bubbles of potassium just jumping out of this thin oxide layer , which is coating it at the minute . now it 's starting to form . so the reason we do it like this is that we end up with a large surface of potassium , so it 's excellent for keeping our solvents dry . so what we 've got now , is we 've got the ampule , and all the way up here , this is literally a mirror of very thin potassium . potassium is very important . our bodies contain quite a lot of potassium . and it 's in all sorts of biological material . if you burn garden rubbish , in the ash that you get in the end is potassium , which is presumably why it 's called potash . so as neil quite literally wets the wall , to get rid of all the un-reacted potassium . wicked . one of my colleagues who used to work with it , described it as evil . captions by www.subply.com
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after completing the 100 meters dash ... like sodium it'ss quite a low melting point metal . and if you mix sodium and potassium together , to make so called sodium potassium amalgam , it 's called nak , by those who work in the trade , na for sodium , k for potassium . nak is a liquid at room temperature . it looks a bit like mercury .
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what is the name of the amalgam made with sodium and potassium ; liquid at room temperature , and so reactive with water that it can catch fire when exposed to air ?
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take a series of still , sequential images . let 's look at them one by one . faster . now , let 's remove the gaps , go faster still . wait for it ... bam ! motion ! why is that ? intellectually , we know we 're just looking at a series of still images , but when we see them change fast enough , they produce the optical illusion of appearing as a single , persistent image that 's gradually changing form and position . this effect is the basis for all motion picture technology , from our led screens of today to their 20th-century cathode ray forebearers , from cinematic film projection to the novelty toy , even , it 's been suggested , all the way back to the stone age when humans began painting on cave walls . this phenomenon of perceiving apparent motion in successive images is due to a characteristic of human perception historically referred to as `` persistence of vision . '' the term is attributed to the english-swiss physicist peter mark roget , who , in the early 19th century , used it to describe a particular defect of the eye that resulted in a moving object appearing to be still when it reached a certain speed . not long after , the term was applied to describe the opposite , the apparent motion of still images , by belgian physicist joseph plateau , inventor of the phenakistoscope . he defined persistence of vision as the result of successive afterimages , which were retained and then combined in the retina , making us believe that what we were seeing is a single object in motion . this explanation was widely accepted in the decades to follow and up through the turn of the 20th century , when some began to question what was physiologically going on . in 1912 , german psychologist max wertheimer outlined the basic primary stages of apparent motion using simple optical illusions . these experiments led him to conclude the phenomenon was due to processes which lie behind the retina . in 1915 , hugo münsterberg , a german-american pioneer in applied psychology , also suggested that the apparent motion of successive images is not due to their being retained in the eye , but is superadded by the action of the mind . in the century to follow , experiments by physiologists have pretty much confirmed their conclusions . as it relates to the illusion of motion pictures , persistence of vision has less to do with vision itself than how it 's interpreted in the brain . research has shown that different aspects of what the eye sees , like form , color , depth , and motion , are transmitted to different areas of the visual cortex via different pathways from the retina . it 's the continuous interaction of various computations in the visual cortex that stitch those different aspects together and culminate in the perception . our brains are constantly working , synchronizing what we see , hear , smell , and touch into meaningful experience in the moment-to-moment flow of the present . so , in order to create the illusion of motion in successive images , we need to get the timing of our intervals close to the speed at which our brains process the present . so , how fast is the present happening according to our brains ? well , we can get an idea by measuring how fast the images need to be changing for the illusion to work . let 's see if we can figure it out by repeating our experiment . here 's the sequence presented at a rate of one frame per two seconds with one second of black in between . at this rate of change , with the blank space separating the images , there 's no real motion perceptible . as we lessen the duration of blank space , a slight change in position becomes more apparent , and you start to get an inkling of a sense of motion between the disparate frames . one frame per second . two frames per second . four frames per second . now we 're starting to get a feeling of motion , but it 's really not very smooth . we 're still aware of the fact that we 're looking at separate images . let 's speed up . eight frames per second . 12 frames per second . it looks like we 're about there . at 24 frames per second , the motion looks even smoother . this is standard full speed . so , the point at which we lose awareness of the intervals and begin to see apparent motion seems to kick in at around eight to 12 frames per second . this is in the neighborhood of what science has determined to be the general threshold of our awareness of seeing separate images . generally speaking , we being to lose that awareness at intervals of around 100 milliseconds per image , which is equal to a frame rate of around ten frames per second . as the frame rate increases , we lose awareness of the intervals completely and are all the more convinced of the reality of the illusion .
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as it relates to the illusion of motion pictures , persistence of vision has less to do with vision itself than how it 's interpreted in the brain . research has shown that different aspects of what the eye sees , like form , color , depth , and motion , are transmitted to different areas of the visual cortex via different pathways from the retina . it 's the continuous interaction of various computations in the visual cortex that stitch those different aspects together and culminate in the perception .
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research has shown that different the aspects of what the eye sees , like form , color , depth , and motion , are transmitted to different areas of the ________ via different pathways from the ________ .
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a close encounter with a man-eating giant , a sorceress who turns men into pigs , a long-lost king taking back his throne . on their own , any of these make great stories , but each is just one episode in the `` odyssey , '' a 12,000-line poem spanning years of ancient greek history , myth , and legend . how do we make sense of such a massive text that comes from and tells of a world so far away ? the fact that we can read the `` odyssey '' at all is pretty incredible , as it was composed before the greek alphabet appeared in the 8th century bce . it was made for listeners rather than readers , and was performed by oral poets called rhapsodes . tradition identifies its author as a blind man named homer . but no one definitively knows whether he was real or legendary . the earliest mentions of him occur centuries after his era . and the poems attributed to him seem to have been changed and rearranged many times by multiple authors before finally being written down in their current form . in fact , the word rhapsode means stitching together , as these poets combined existing stories , jokes , myths , and songs into a single narrative . to recite these massive epics live , rhapsodes employed a steady meter , along with mnemonic devices , like repetition of memorized passages or set pieces . these included descriptions of scenery and lists of characters , and helped the rhapsode keep their place in the narrative , just as the chorus or bridge of a song helps us to remember the next verses . because most of the tales were familiar to the audience , it was common to hear the sections of the poem out of order . at some point , the order became set in stone and the story was locked into place as the one we read today . but since the world has changed a bit in the last several thousand years , it helps to have some background before jumping in . the `` odyssey '' itself is a sequel to homer 's other famous epic , the `` iliad , '' which tells the story of the trojan war . if there 's one major theme uniting both poems , it 's this : do not , under any circumstances , incur the wrath of the gods . the greek pantheon is a dangerous mix of divine power and human insecurity , prone to jealousy and grudges of epic proportions . and many of the problems faced by humans in the poems are caused by their hubris , or excessive pride in believing themselves superior to the gods . the desire to please the gods was so great that the ancient greeks traditionally welcomed all strangers into their homes with generosity for fear that the strangers might be gods in disguise . this ancient code of hospitality was called xenia . it involved hosts providing their guests with safety , food , and comfort , and the guests returning the favor with courtesy and gifts if they had them . xenia has a significant role in the `` odyssey , '' where odysseus in his wanderings is the perpetual guest , while in his absence , his clever wife penelope plays non-stop host . the `` odyssey '' recounts all of odysseus 's years of travel , but the narrative begins in medias res in the middle of things . ten years after the trojan war , we find our hero trapped on an island , still far from his native ithaca and the family he has n't seen for 20 years . because he 's angered the sea god poseidon by blinding his son , a cyclops , odysseus 's passage home has been fraught with mishap after mishap . with trouble brewing at home and gods discussing his fate , odysseus begins the account of those missing years to his hosts . one of the most fascinating things about the `` odyssey '' is the gap between how little we know about its time period and the wealth of detail the text itself contains . historians , linguists , and archeologists have spent centuries searching for the ruins of troy and identifying which islands odysseus visited . just like its hero , the 24-book epic has made its own long journey through centuries of myth and history to tell us its incredible story today .
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ten years after the trojan war , we find our hero trapped on an island , still far from his native ithaca and the family he has n't seen for 20 years . because he 's angered the sea god poseidon by blinding his son , a cyclops , odysseus 's passage home has been fraught with mishap after mishap . with trouble brewing at home and gods discussing his fate , odysseus begins the account of those missing years to his hosts .
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which god has hindered odysseus ’ journey home ?
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which of these entities has evolved the ability to manipulate an animal many times its size ? the answer is all of them . these are all parasites , organisms that live on or inside another host organism , which they harm and sometimes even kill . parasite survival depends on transmitting from one host to the next , sometimes through an intermediate species . our parasites elegantly achieve this by manipulating their host 's behavior , sometimes through direct brain hijacking . for example , this is the gordian worm . one of its hosts , this cricket . the gordian worm needs water to mate , but the cricket prefers dry land . so once it 's big enough to reproduce , the worm produces proteins that garble the cricket 's navigational system . the confused cricket jumps around erratically , moves closer to water , and eventually leaps in , often drowning in the process . the worm then wriggles out to mate and its eggs get eaten by little water insects that mature , colonize land , and are , in turn , eaten by new crickets . and thus , the gordian worm lives on . and here 's the rabies virus , another mind-altering parasite . this virus infects mammals , often dogs , and travels up the animal 's nerves to its brain where it causes inflammation that eventually kills the host . but before it does , it often increases its host 's aggressiveness and ramps up the production of rabies-transmitting saliva , while making it hard to swallow . these factors make the host more likely to bite another animal and more likely to pass the virus on when it does . and now , meet ophiocordyceps , also known as the zombie fungus . its host of choice is tropical ants that normally live in treetops . after ophiocordyceps spores pierce the ant 's exoskeleton , they set off convulsions that make the ant fall from the tree . the fungus changes the ant 's behavior , compelling it to wander mindlessly until it stumbles onto a plant leaf with the perfect fungal breeding conditions , which it latches onto . the ant then dies , and the fungus parasitizes its body to build a tall , thin stalk from its neck . within several weeks , the stalk shoots off spores , which turn more ants into six-legged leaf-seeking zombies . one of humanity 's most deadly assailants is a behavior-altering parasite , though if it 's any consolation , it 's not our brains that are being hijacked . i 'm talking about plasmodium , which causes malaria . this parasite needs mosquitoes to shuttle it between hosts , so it makes them bite more frequently and for longer . there 's also evidence that humans infected with malaria are more attractive to mosquitoes , which will bite them and transfer the parasite further . this multi-species system is so effective , that there are hundreds of millions of malaria cases every year . and finally , there are cats . do n't worry , there probably are n't any cats living in your body and controlling your thoughts . i mean , probably . but there is a microorganism called toxoplasma that needs both cats and rodents to complete its life cycle . when a rat gets infected by eating cat feces , the parasite changes chemical levels in the rat 's brain , making it less cautious around the hungry felines , maybe even attracted to them . this makes them easy prey , so these infected rodents get eaten and pass the parasite on . mind control successful . there 's even evidence that the parasite affects human behavior . in most cases , we do n't completely understand how these parasites manage their feats of behavior modification . but from what we do know , we can tell that they have a pretty diverse toolbox . gordian worms seem to affect crickets ' brains directly . the malaria parasite , on the other hand , blocks an enzyme that helps the mosquitoes feed , forcing them to bite over and over and over again . the rabies virus may cause that snarling , slobbering behavior by putting the immune system into overdrive . but whatever the method , when you think about how effectively these parasites control the behavior of their hosts , you may wonder how much of human behavior is actually parasites doing the talking . since more than half of the species on earth are parasites , it could be more than we think .
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i mean , probably . but there is a microorganism called toxoplasma that needs both cats and rodents to complete its life cycle . when a rat gets infected by eating cat feces , the parasite changes chemical levels in the rat 's brain , making it less cautious around the hungry felines , maybe even attracted to them .
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suppose you did an experiment in which you gave uninfected rats and rats infected with toxoplasma a choice between hiding places sprinkled with the urine of cats and rabbits . which of the following results would you expect to observe ?
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hey , vsauce . michael here . and what if every single person on earth jumped at the exact same time ? could it cause an earthquake or would we not even be able to tell ? well , first things first , let 's talk about the earth 's rotation . the earth spins , that 's why we have night and day , and it spins quickly . at the equator , the earth is spinning at more than 1,000 mph . now , a spinning ice skater can speed up by moving mass closer to the center and the earth is no different . in fact , if you get down on the ground right now and move your mass closer to earth 's center , technically , you will speed up earth 's rotation , making this day shorter . now , the change that you would make to the earth 's rotation is way smaller than we could even measure , but it is calculable , and the impact can be quite impressive when you talk about redistributing more mass than just one person . for instance , last year , the earthquake in japan redistributed so much of earth 's mass towards the center , that every day since then has been 1.8 microseconds shorter . but that was a giant geological event . what can us humans do to the earth all on our own ? i mean , there are more than 7 billion of us now . what if we all got together in one place and jumped ? well , what would that even look like ? interestingly , if you took the entire human population of earth and had them all live in one place with the same density that people live in in new york city , you could fit everyone - all of us - into the state of texas . but that 's living , not standing around in a crowd , which is how we would probably want to do the jump . if every single person alive right now on earth stood shoulder to shoulder , you could fit all of us into the city of los angeles . it would be an incredible sight to behold - a mere 500 square miles containing every single person on earth . ok , so , then we jump . what happens ? unfortunately , not much . i mean , we 're all awesome people here on earth , but our collective mass compared to the mass of the entire earth ? it 's like nothing . in fact , dot physics calculated that if all of us were to get together in one location and all jump 30 cm into the air at the exact same time , we would push earth away from us a tiny amount . earth would only move away from us about 1/100th of the width of a single hydrogen atom . and here 's another thing . because we 're all jumping and then going back to where we started , earth is just going to move back to where it started . so , our big jump wo n't be able to change earth 's position in space , but , c'mon , 7 billion people all jumping together ? that 's got ta be able to cause some sort of seismic activity , right ? so let 's say you have a lot of people all together in one place and you have them all jump on : 1-2-3 ! did you feel that ? well , the bbc did this with 50,000 people and discovered that a kilometer and a half away , it only registered a .6 on the richter scale . you would need 7 million times more people than even live on earth right now to jump at once to recreate the earthquake that recently happened in japan . so , even though we 're all awesome , compared to the size of the earth , we 're not much . but do n't get too discouraged . our collective jump would contain a lot of energy . the straight dope calculated that even if only the people who lived in china got together and jumped , their jump would be the equivalent of 500 tons of tnt . of course , 500 tons of tnt does n't do much to an earth that weighs 6 sextillion 588 quintillion tons . to make yourself feel more powerful , pick a card . i 've got 10 of them here , let 's say , hmmm , you choose this one . boom , congratulations , we have just decimated this deck of cards . why ? well because , technically , decimate does not mean `` obliterate completely . '' deci=10 . it means to take away 1/10th of something . so , the next time you take a quiz and do n't do so well on it , you only get 10 % . well , sure , that 's an `` f '' , but by getting 10 % of them right , you decimated that quiz . and since we 've been talking about crowds , let 's talk about youtube crowds . youtube audiences , that view count that you see at the bottom of every video , and get some perspective on it . we 'll being with dunbar 's number . it 's an estimation of the maximum number of people we can have stable , social relationships with at a given moment and it 's based on the size of our neo-cortex . these are n't just acquaintances , these are people you have social contact with - a network where you know how everyone relates to everyone else . and the number is usually given to be somewhere between 100-230 , which means that when a youtube video receives more than 230 views from different people , more people have seen that video than you could ever realistically hope to know well , at a given moment . if a video has more than 100,000 views from different people , more people have seen that video than you will ever meet in your life . and by meet , i mean shakes hands with , learn their name , talk with them for a bit . i mean , think of it this way . you and me , we 're only statistically expected to live around 28,470 days . so , even if you were to meet someone , 2-3 people every day of your life , including when you were a baby , you still would n't meet as many people as have seen that youtube video with 100,000 views . but keep this in mind . even though you , or even a large group of us , ca n't do much to change earth 's location or rotation , we can affect it a little bit . newton 's third law guarantees this . if you weigh 150 pounds , the earth is pulling you down with a force of 150 pounds . but you are also pulling up on the earth with a force of 150 pounds . if you fall 3 meters , the earth has pulled you down 3 meters . but you have also exerted a equal and opposite force on the earth . of course , it 's a lot bigger . so , if you fall 3 meters , you pull the earth up about a billionth of the width of a proton , which ai n't bad . so the next time you move your body , the next time you jump , felicia , think about this . you just affected the earth as much as it affected you . you 've got that kind of power . speaking of power , you all should go check out `` geek & amp ; amp ; sundry '' , felicia 's new channel . it 's one of my new favorite things . and as always , thanks for watching .
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but that 's living , not standing around in a crowd , which is how we would probably want to do the jump . if every single person alive right now on earth stood shoulder to shoulder , you could fit all of us into the city of los angeles . it would be an incredible sight to behold - a mere 500 square miles containing every single person on earth .
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if the earth 's entire human population stood shoulder to shoulder , we could all fit into
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one of the great things about science is that when scientists make a discovery , it 's not always in a prescribed manner , as in , only in a laboratory under strict settings , with white lab coats and all sorts of neat science gizmos that go , `` beep ! '' in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get . my case in point : the weird history of the cell theory . there are three parts to the cell theory . one : all organisms are composed of one or more cells . two : the cell is the basic unit of structure and organization in organisms . and three : all cells come from preexisting cells . to be honest , this all sounds incredibly boring until you dig a little deeper into how the world of microscopic organisms , and this theory came to be . it all started in the early 1600s in the netherlands , where a spectacle maker named zacharias janssen is said to have come up with the first compound microscope , along with the first telescope . both claims are often disputed , as apparently he was n't the only bored guy with a ton of glass lenses to play with at the time . despite this , the microscope soon became a hot item that every naturalist or scientist at the time wanted to play with , making it much like the ipad of its day . one such person was a fellow dutchman by the name of anton van leeuwenhoek , who heard about these microscope doohickeys , and instead of going out and buying one , he decided to make his own . and it was a strange little contraption indeed , as it looked more like a tiny paddle the size of a sunglass lens . if he had stuck two together , it probably would have made a wicked set of sunglasses that you could n't see much out of . anyhoo , once leeuwenhoek had his microscope ready , he went to town , looking at anything and everything he could with them , including the gunk on his teeth . yes , you heard right . he actually discovered bacteria by looking at dental scrapings , which , when you keep in mind that people did n't brush their teeth much -- if at all -- back then , he must have had a lovely bunch of bacteria to look at . when he wrote about his discovery , he did n't call them bacteria , as we know them today . but he called them `` animalcules , '' because they looked like little animals to him . while leeuwenhoek was staring at his teeth gunk , he was also sending letters to a scientific colleague in england , by the name of robert hooke . hooke was a guy who really loved all aspects of science , so he dabbled in a little bit of everything , including physics , chemistry and biology . thus it is hooke who we can thank for the term `` the cell , '' as he was looking at a piece of cork under his microscope , and the little chambers he saw reminded him of cells , or the rooms monks slept in in their monasteries . think college dorm rooms , but without the tvs , computers and really annoying roommates . hooke was something of an underappreciated scientist of his day -- something he brought upon himself , as he made the mistake of locking horns with one of the most famous scientists ever , sir isaac newton . remember when i said hooke dabbled in many different fields ? well , after newton published a groundbreaking book on how planets move due to gravity , hooke made the claim that newton had been inspired by hooke 's work in physics . newton , to say the least , did not like that , which sparked a tense relationship between the two that lasted even after hooke died , as quite a bit of hooke 's research -- as well as his only portrait -- was ... misplaced , due to newton . much of it was rediscovered , thankfully , after newton 's time , but not his portrait , as , sadly , no one knows what robert hooke looked like . fast-forward to the 1800s , where two german scientists discovered something that today we might find rather obvious , but helped tie together what we now know as the cell theory . the first scientist was matthias schleiden , a botanist who liked to study plants under a microscope . from his years of studying different plant species , it finally dawned on him that every single plant he had looked at were all made of cells . at the same time , on the other end of germany was theodor schwann , a scientist who not only studied slides of animal cells under the microscope and got a special type of nerve cell named after him , but also invented rebreathers for firefighters , and had a kickin ' pair of sideburns . after studying animal cells for a while , he , too , came to the conclusion that all animals were made of cells . immediately , he reached out via snail mail , as twitter had yet to be invented , to other scientists working in the same field with schleiden , who got back to him , and the two started working on the beginnings of the cell theory . a bone of contention arose between them . as for the last part of the cell theory -- that cells come from preexisting cells -- schleiden did n't exactly subscribe to that thought , as he swore cells came from free-cell formation , where they just kind of spontaneously crystallized into existence . that 's when another scientist named rudolph virchow , stepped in with research showing that cells did come from other cells , research that was actually -- hmm ... how to put it ? -- `` borrowed without permission '' from a jewish scientist by the name of robert remak , which led to two more feuding scientists . thus , from teeth gunk to torquing off newton , crystallization to schwann cells , the cell theory came to be an important part of biology today . some things we know about science today may seem boring , but how we came to know them is incredibly fascinating . so if something bores you , dig deeper . it 's probably got a really weird story behind it somewhere .
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at the same time , on the other end of germany was theodor schwann , a scientist who not only studied slides of animal cells under the microscope and got a special type of nerve cell named after him , but also invented rebreathers for firefighters , and had a kickin ' pair of sideburns . after studying animal cells for a while , he , too , came to the conclusion that all animals were made of cells . immediately , he reached out via snail mail , as twitter had yet to be invented , to other scientists working in the same field with schleiden , who got back to him , and the two started working on the beginnings of the cell theory .
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which scientist realized that , by studying samples under a microscope , all animals are made up of cells ?
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think of all the food made in the world each year . hard to picture ? then , imagine that you are all of humanity , and on a plate in front of you is the one lovely annual meal you make for yourself . you did all sorts of work putting that meal on your table . you must be eager to consume the fruits of your labor . and the vegetables and meats and waffles of your labor , too , right ? well , oddly enough , a third of that meal ends up in the trash . a third of the food we eat globally , an estimated 1.3 billion tons ends up as waste . all the work we put into producing that food is wasted . and what 's worse , it costs us . america alone spends an estimated 165 billion dollars a year managing food waste . we 're wasting food , energy , and money . perhaps worst of all , we 're wasting the chance to change , to make the system of food consumption more efficient . if you want to bring on that change , you should know about a humble yet diligent and ever-so-crucial ally : the worm . worms convert organic waste and other compostable products into natural fertilizers . up to 75 % of what we put in the waste stream can become food and bedding material for vermicomposting . you can create a worm bin in your own home to see the composting process in action . first off , you need worms and not your typical earthworms . you need redworms , eisenia foetida , the species responsible for most vermicomposting in north america . these red wigglers are surface dwellers who do n't burrow too deep , they 're optimal feeders around room temperature , and they 're well-suited to converting organic waste into usable fertilizer . now , your worms might be vermin , but they need a comfortable space to live and work : some bedding materials , either shredded paper or cardboard , some moisture , and , of course , food , mainly , your leftovers , slightly decomposed table scraps . the worms break down food waste and other organic matter into castings , a fancy synonym for worm poop . their excrement is absolutely teeming with microbes , which continue the decomposition process , making all those once-wasted nutrients available again as fertilizer . the timeline for the whole process varies depending on the quantity of worms , the temperature , and how much waste is added to the bin . and there 's another timeline to consider . in a healthy worm-bin habitat , worm reproduction will occur when the wigglers become sexually mature , indicated by an elongation of the segments into a bulbous structure . three-month old wigglers can produce two to three semi-translucent yellow worm cocoons a week . you thought only moths and butterflies come out of cocoons ? well , we ca n't all be majestic . it takes around 11 weeks for new babies to hatch . when your bin seems to be full of living vermicelli noodles , it 's time to share the bounty with your friends and start a vermicompost club . or keep those worms to yourself and start a business . vermicomposting is n't confined only to small worm bins , it 's an emerging entrepreneurial enterprise . large-scale facilities convert bulk organic waste and even manure into rich , black castings called black gold . its value as a soil additive is unparalleled , and it can help plants resist harmful pathogens . the lack of available land in urban environments , coupled with growing interest in smaller-scale farming means there is a market for vermicomposting . many communities use composting as part of zero-waste strategies , and they can sell their worm-eaten table scraps to local farms , hungry for rich fertilizer . so , instead of wasting money , dumping wasted food in landfills , we can remake waste into an asset , putting it back into our food system to make it more sustainable , all with the help of the humble worm , the tiny organism that can help us change the way we look at food 's place in our lives and our place in the world , as long as we give the little guy a place at our table . well , not an actual seat at the table . a bin in the shed is fine .
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worms convert organic waste and other compostable products into natural fertilizers . up to 75 % of what we put in the waste stream can become food and bedding material for vermicomposting . you can create a worm bin in your own home to see the composting process in action . first off , you need worms and not your typical earthworms . you need redworms , eisenia foetida , the species responsible for most vermicomposting in north america .
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you should use earthworms collected from your yard to start vermicomposting efforts at your own home .
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translator : andrea mcdonough reviewer : jessica ruby these are grizzly bears . as you can see , they have big teeth and giant claws . but once you get to know them better , they 're not as ferocious as you might think . they play a critical role in the function of our ecosystems , but , unfortunately , their habitat is dwindling fast . in order to protect them , it 's important to know why do grizzlies choose certain areas to inhabit in the first place ? let 's look at a threatened population of bears living in the rocky mountains of canada . remember those giant claws ? well , they 're not for what you might think . they have evolved specifically for digging up energy-rich roots . it turns out that grizzlies eat a lot of plants . the ones that live here are almost vegetarians . you see , unlike other predators , grizzlies have diverse diets that can include up to 90 % vegetation . however , maintaining a diet of plants can be difficult . in these northern latitudes , you have distinct seasons where it 's really nice and green for part of the year and really cold for the other part . if you eat plants , you have almost nothing to eat for the cold part of the year . so , you either have to migrate like geese or hibernate like ground squirrels . grizzly bears hibernate . their behaviors are closely synchronized with the seasons . during the summer , they have to pack on enough body fat to survive the winter . without it , they would either starve or not have enough energy to successfully produce offspring . but when you eat mostly plants , it 's hard to gain a lot of weight . you need to be a highly effective forager . so , bears tightly follow the schedule of the plants and harvest them like crops at the point in time when they are at the most nutritious . this will happen in different places at different times . in autumn , a large male grizzly can eat up to 200,000 berries in a single day . therefore , to protect these bears , researchers want to take a closer look at the seasonal interaction between grizzlies and plants to identify areas of the highest quality habitat . this begins 700 kilometers up in space . up here , two nasa satellites carry sensors that are sensitive to the light reflected by vegetation . every species of plant reflects a unique combination of wave lengths , called spectral signatures that act like different chords on a piano but use light instead of sound . these signatures are recorded by the satellites every day and are combined like frames in a movie so you can watch the vegetation grow over an entire summer . simultaneously , the movements of bears wearing gps collars are monitored to see how they respond to the ebb and flow of nutrition throughout their habitat . now , instead of ordinary , static habitat maps , these dynamic , time-lapse habitat maps could be used for grizzly bear conservation in a number of ways . first , they help calculate the carrying capacity of the study area . in other words , how many bears can the remaining habitat support ? is there enough food to go around ? second , the maps show where bears will be foraging at specific times . we can prevent disturbing the bears and stressing them out by avoiding these areas during important feeding periods . finally , the maps can be used to predict the effects of climate change , where shifting annual temperatures will alter the rate of plant growth , throwing the bears ' precise foraging schedule out of whack . this provides less food and increases competition between bears . grizzlies are charismatic symbols of the wilderness . these habitat maps made from satellite imagery can not only help conserve grizzly bears but all sorts of different species . they aid us in understanding how ecosystems function , where they are threatened , and how we can try to keep our fragile , amazing planet intact .
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so , you either have to migrate like geese or hibernate like ground squirrels . grizzly bears hibernate . their behaviors are closely synchronized with the seasons .
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grizzly bears have evolved very long claws , for what purpose ?
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when we hear the word radiation , it 's tempting to picture huge explosions and frightening mutations , but that 's not the full story . radiation also applies to rainbows and a doctor examining an x-ray . so what is radiation really , and how much should we worry about its effects ? the answer begins with understanding that the word radiation describes two very different scientific phenomena : electromagnetic radiation and nuclear radiation . electromagnetic radiation is pure energy consisting of interacting electrical and magnetic waves oscillating through space . as these waves oscillate faster , they scale up in energy . at the lower end of the spectrum , there 's radio , infrared , and visible light . at the higher end are ultraviolet , x-ray , and gamma rays . modern society is shaped by sending and detecting electromagnetic radiation . we might download an email to our phone via radio waves to open an image of an x-ray print , which we can see because our screen emits visible light . nuclear radiation , on the other hand , originates in the atomic nucleus , where protons repel each other due to their mutually positive charges . a phenomenon known as the strong nuclear force struggles to overcome this repulsion and keep the nucleus intact . however , some combinations of protons and neutrons , known as isotopes , remain unstable , or radioactive . they will randomly eject matter and/or energy , known as nuclear radiation , to achieve greater stability . nuclear radiation comes from natural sources , like radon , a gas which seeps up from the ground . we also refine naturally occurring radioactive ores to fuel nuclear power plants . even bananas contain trace amounts of a radioactive potassium isotope . so if we live in a world of radiation , how can we escape its dangerous effects ? to start , not all radiation is hazardous . radiation becomes risky when it rips atoms ' electrons away upon impact , a process that can damage dna . this is known as ionizing radiation because an atom that has lost or gained electrons is called an ion . all nuclear radiation is ionizing , while only the highest energy electromagnetic radiation is . that includes gamma rays , x-rays , and the high-energy end of ultraviolet . that 's why as an extra precaution during x-rays , doctors shield body parts they do n't need to examine , and why beach-goers use sunscreen . in comparison , cell phones and microwaves operate at the lower end of the spectrum , so there is no risk of ionizing radiation from their use . the biggest health risk occurs when lots of ionizing radiation hits us in a short time period , also known as an acute exposure . acute exposures overwhelm the body 's natural ability to repair the damage . this can trigger cancers , cellular dysfunction , and potentially even death . fortunately , acute exposures are rare , but we are exposed daily to lower levels of ionizing radiation from both natural and man-made sources . scientists have a harder time quantifying these risks . your body often repairs damage from small amounts ionizing radiation , and if it ca n't , the results of damage may not manifest for a decade or more . one way scientists compare ionizing radiation exposure is a unit called the sievert . an acute exposure to one sievert will probably cause nausea within hours , and four sieverts could be fatal . however , our normal daily exposures are far lower . the average person receives 6.2 millisieverts of radiation from all sources annually , around a third due to radon . at only five microsieverts each , you 'd need to get more than 1200 dental x-rays to rack up your annual dosage . and remember that banana ? if you could absorb all the banana 's radiation , you 'd need around 170 a day to hit your annual dosage . we live in a world of radiation . however , much of that radiation is non-ionizing . for the remainder that is ionizing , our exposures are usually low , and choices like getting your home tested for radon and wearing sunscreen can help reduce the associated health risks . marie curie , one of the early radiation pioneers , summed up the challenge as follows : `` nothing in life is to be feared , it is only to be understood . now is the time to understand more , so that we may fear less . ''
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in comparison , cell phones and microwaves operate at the lower end of the spectrum , so there is no risk of ionizing radiation from their use . the biggest health risk occurs when lots of ionizing radiation hits us in a short time period , also known as an acute exposure . acute exposures overwhelm the body 's natural ability to repair the damage .
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why is it hard for us to get a good understanding of the health impact of exposure to low levels of radiation ?
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what would you do if you thought your country was on the path to tyranny ? if you saw one man gaining too much power , would you try to stop him ? even if that man was one of your closest friends and allies ? these were the questions haunting roman senator marcus junius brutus in 44 bce , the year julius caesar would be assassinated . opposing unchecked power was n't just a political matter for brutus ; it was a personal one . he claimed descent from lucius junius brutus , who had helped overthrow the tyrannical king known as tarquin the proud . instead of seizing power himself , the elder brutus led the people in a rousing oath to never again allow a king to rule . rome became a republic based on the principle that no one man should hold too much power . now , four and a half centuries later , this principle was threatened . julius ceasar 's rise to the powerful position of consul had been dramatic . years of military triumphs had made him the wealthiest man in rome . and after defeating his rival pompey the great in a bitter civil war , his power was at its peak . his victories and initiatives , such as distributing lands to the poor , had made him popular with the public , and many senators vied for his favor by showering him with honors . statues were built , temples were dedicated , and a whole month was renamed , still called july today . more importantly , the title of dictator , meant to grant temporary emergency powers in wartime , had been bestowed upon caesar several times in succession . and in 44 bce , he was made dictator perpetuo , dictator for a potentially unlimited term . all of this was too much for the senators who feared a return to the monarchy their ancestors had fought to abolish , as well as those whose own power and ambition were impeded by caesar 's rule . a group of conspirators calling themselves the liberators began to secretly discuss plans for assassination . leading them were the senator gaius cassius longinus and his friend and brother-in-law , brutus . joining the conspiracy was not an easy choice for brutus . even though brutus had sided with pompey in the ill-fated civil war , caesar had personally intervened to save his life , not only pardoning him but even accepting him as a close advisor and elevating him to important posts . brutus was hesitant to conspire against the man who had treated him like a son , but in the end , cassius 's insistence and brutus 's own fear of caesar 's ambitions won out . the moment they had been waiting for came on march 15 . at a senate meeting held shortly before caesar was to depart on his next military campaign , as many as 60 conspirators surrounded him , unsheathing daggers from their togas and stabbing at him from all sides . as the story goes , caesar struggled fiercely until he saw brutus . despite the famous line , `` et tu , brute ? '' written by shakespeare , we do n't know caesar 's actual dying words . some ancient sources claim he said nothing , while others record the phrase , `` and you , child ? `` , fueling speculation that brutus may have actually been caesar 's illegitimate son . but all agree that when caesar saw brutus among his attackers , he covered his face and gave up the fight , falling to the ground after being stabbed 23 times . unfortunately for brutus , he and the other conspirators had underestimated caesar 's popularity among the roman public , many of whom saw him as an effective leader , and the senate as a corrupt aristocracy . within moments of caesar 's assassination , rome was in a state of panic . most of the other senators had fled , while the assassins barricaded themselves on the capitoline hill . mark antony , caesar 's friend and co-consul , was swift to seize the upper hand , delivering a passionate speech at caesar 's funeral days later that whipped the crowd into a frenzy of grief and anger . as a result , the liberators were forced out of rome . the ensuing power vacuum led to a series of civil wars , during which brutus , facing certain defeat , took his own life . ironically , the ultimate result would be the opposite of what the conspirators had hoped to accomplish : the end of the republic and the concentration of power under the office of emperor . opinions over the assassination of caesar were divided from the start and have remained so . as for brutus himself , few historical figures have inspired such a conflicting legacy . in dante 's `` inferno , '' he was placed in the very center of hell and eternally chewed by satan himself for his crime of betrayal . but swift 's `` gulliver 's travels '' described him as one of the most virtuous and benevolent people to have lived . the interpretation of brutus as either a selfless fighter against dictatorship or an opportunistic traitor has shifted with the tides of history and politics . but even today , over 2000 years later , questions about the price of liberty , the conflict between personal loyalties and universal ideals , and unintended consequences remain more relevant than ever .
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leading them were the senator gaius cassius longinus and his friend and brother-in-law , brutus . joining the conspiracy was not an easy choice for brutus . even though brutus had sided with pompey in the ill-fated civil war , caesar had personally intervened to save his life , not only pardoning him but even accepting him as a close advisor and elevating him to important posts .
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why was brutus convinced to lead the conspiracy against caesar ?
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translator : andrea mcdonough reviewer : bedirhan cinar one of the grandest scientific tools ever made by mankind is called an atom smasher . and i mean literally grand . the biggest one ever built , the large hadron collider , or lhc , is a ring with a circumference of about 18 miles . that 's more than the entire length of manhattan . so what is an atom smasher ? it is a device that collides atomic nuclei together at extremely high energy . the most powerful one scientists have ever built can heat matter to the hottest temperatures ever achieved , temperatures last seen at a trillionth of second after the universe began . our accelerators are full of engineering superlatives . the beam-containing region of the lhc is a vacuum , with lower pressure than what surrounds the international space station , and is 456 degrees fahrenheit below zero , colder than the temperature of deepest space . a previous accelerator sitting in the lhc tunnel holds the world record for velocity , accelerating an electron to a speed so fast that if it were to race a photon of light , it would take about 14 minutes for the photon to get a lead of about 10 feet . if that does n't impress you , remember the photon is fastest thing in the universe , it goes about 186,000 miles per second . so how do these subatomic particle accelerators work ? well , they use electric fields . electric fields make charged particles move in the same way that gravity will pull a dropped baseball . the force from the electric field will pull a particle to make it move . the speed will continue to increase until the charged particle is moving incredibly fast . a simple particle accelerator can be made by hooking two parallel metal plates to a battery . the charge from the battery moves on to the two metal plates and makes an electric field that pulls the particle along . and that 's it , you got a particle accelerator . the problem is that an accelerator built this way is very weak . building a modern accelerator like the lhc this way would take over five trillion standard d-cell batteries . so scientists use much stronger batteries and put them one after another . an earlier accelerator used this method and was about a mile long and was equivalent to 30 billion batteries . however , to make an accelerator that is equivalent to five trillion batteries would require an accelerator 150 miles long . scientists needed another way . while electric fields would make a particle go faster , magnetic fields make them move in a circular path . if you put an electric field along the circle , you do n't need to use miles of electric fields , you can use a single electric field over and over again . the beams go around the circle , and each time they gain more energy . so very high-energy accelerators consist of a short region with accelerating electric fields , combined with long series of magnets that guide the particles in a circle . the strength of the magnets and the radius of the circular path determines the maximum energy of the beam . once the beam is zooming along , then the real fun begins , the smashing . the reason physicists want to get those particles moving so fast is so that they can slam them into one another . these collisions can teach us about the fundamental rules that govern matter , but they 'd be impossible without the feat of engineering that is the particle accelerator .
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the charge from the battery moves on to the two metal plates and makes an electric field that pulls the particle along . and that 's it , you got a particle accelerator . the problem is that an accelerator built this way is very weak .
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what is the role of magnets in a particle accelerator ?
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rising temperatures and seas , massive droughts , changing landscapes . successfully adapting to climate change is growing increasingly important . for humans , this means using our technological advancement to find solutions , like smarter cities and better water management . but for some plants and animals , adapting to these global changes involves the most ancient solution of all : evolution . evolutionary adaptation usually occurs along time scales of thousands to hundreds of thousands of years . but in cases where species are under especially strong selective conditions , like those caused by rapidly changing climates , adaptive evolution can happen more quickly . in recent decades , we 've seen many plants , animals , and insects relocating themselves and undergoing changes to their body sizes , and the dates they flower or breed . but many of these are plastic , or nonheritable changes to an individual 's physical traits . and there are limits to how much an organism can change its own physiology to meet environmental requirements . that 's why scientists are seeking examples of evolutionary changes coded in species ' dna that are heritable , long-lasting , and may provide a key to their future . take the tawny owl . if you were walking through a wintry forest in northern europe 30 years ago , chances are you 'd have heard , rather than seen , this elusive bird . against the snowy backdrop , its plumage would have been near impossible to spot . today , the landscape is vastly different . since the 1980s , climate change has led to significantly less snowfall , but you 'd still struggle to spot a tawny owl because nowadays , they 're brown . the brown color variant is the genetically dominant form of plumage in this species , but historically , the recessive pale gray variant triumphed because of its selective advantage in helping these predators blend in . however , less snow cover reduces opportunities for camouflage , so lately , this gray color variant has been losing the battle against natural selection . the offspring of the brown color morphs , on the other hand , have an advantage in exposed forests , so brown tawny owls are flourishing today . several other species have undergone similar climate-change-adaptive genetic changes in recent decades . pitcher plant mosquitoes have rapidly evolved to take advantage of the warmer temperatures , entering dormancy later and later in the year . two spot ladybug populations , once comprised of equal numbers of melanic and non-melanic morphs , have now shifted almost entirely to the non-melanic color combination . scientists think that keeps them from overheating . meanwhile , pink salmon have adapted to warmer waters by spawning earlier in the season to protect their sensitive eggs . and wild thyme plants in europe are producing more repellent oils to protect themselves against the herbivores that become more common when it 's warm . these plants and animals belong to a group of about 20 identified species with evolutionary adaptations to rapid climate change , including snapping turtles , wood frogs , knotweed , and silver spotted skipper butterflies . however , scientists hope to discover more species evolving in response to climate change out of 8.7 million species on the planet . for most of our planet 's astounding and precious biodiversity , evolution wo n't be the answer . instead , many of those species will have to rely on us to help them survive a changing world or face extinction . the good news is we already have the tools . across the planet , we 're making on-the-ground decisions that will help entire ecosystems adapt . critical climate refuges are being identified and set aside , and projects are underway to help mobile species move to more suitable climates . existing parks and protected areas are also doing climate change check-ups to help their wildlife cope . fortunately , it 's still within our power to preserve much of the wondrous biodiversity of this planet , which , after all , sustains us in so many ways .
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since the 1980s , climate change has led to significantly less snowfall , but you 'd still struggle to spot a tawny owl because nowadays , they 're brown . the brown color variant is the genetically dominant form of plumage in this species , but historically , the recessive pale gray variant triumphed because of its selective advantage in helping these predators blend in . however , less snow cover reduces opportunities for camouflage , so lately , this gray color variant has been losing the battle against natural selection .
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what is the genetically dominant form of plumage for tawny owls ?
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translator : andrea mcdonough reviewer : bedirhan cinar pretty much everyone loves eating pizza , but it can be a messy business . pizza is soft and bendable . so how can you stop all that cheese from falling off ? you might know some tricks : you can use two hands -- not so classy , or you can use a paper plate and allow only the tip of the pizza to peek out . there 's one other trick , though : holding the crust , you can sort of fold the slice down the middle . now the tip of the pizza is n't falling over , and you can eat it without getting tomato sauce all over yourself or accidentally biting off some of that paper plate . but why should the tip stay up just because you bent the crust ? to understand this , you need to know two things : a little bit about the math of curved shapes and a little about the physics of thin sheets . first , the math . suppose i have a flat sheet made out of rubber . it 's really thin and bendable , so it 's easy to roll into a cylinder . i do n't need to stretch the sheet at all , just bend it . this property where one shape can be transformed into another without stretching or crumpling , is called isometry . a mathematician would say that a flat sheet is isometric to a cylinder . but not all shapes are isometric . if i try to turn my flat sheet into part of a sphere , there 's no way i can do it . you can check this for yourself , by trying to fit a flat sheet of paper onto a soccer ball without stretching or crumpling the paper . it 's just not possible . so a mathematician would say that a flat sheet and a sphere are n't isometric . there 's one more familiar shape that is n't isometric to any of the shapes we 've seen so far : a potato chip . potato chip shapes are n't isometric to flat sheets . if you want to get a flat piece of rubber into the shape of a potato chip , you need to stretch it -- not just bend it , but stretch it as well . so , that 's the math . not so hard , right ? now for the physics . it can be summed up in one sentence : thin sheets are easy to bend but hard to stretch . this is really important . thin sheets are easy to bend but hard to stretch . remember when we rolled our flat sheet of rubber into a cylinder ? that was n't hard , right ? but imagine how hard you 'd have pull on the sheet to increase its area by 10 percent . it would be pretty difficult . the point is that bending a thin sheet takes a relatively small amount of force , but stretching or crumbling a thin sheet is much harder . now , finally , we get to talk about pizza . suppose you go down to the pizzeria and buy yourself a slice . you pick it up from the crust , first , without doing the fold . because of gravity , the slice bends downwards . pizza is pretty thin , after all , and we know that thin sheets are easy to bend . you ca n't get it in your mouth , cheese and tomato sauce dripping everywhere -- it 's a big mess . so you fold the crust . when you do , you force the pizza into something like a taco shape . that 's not hard to do -- after all , this shape is isometric to the original pizza , which was flat . but imagine what would happen if the pizza were to droop down while you 're bending it . now it looks like a droopy taco . and what does a droopy taco look like ? a potato chip ! but we know that potato chips are not isometric to flat pieces of rubber or flat pizzas , and that means that in order to get into the shape it 's in now , the slice of pizza had to stretch . since the pizza is thin , this takes a lot of force , compared to the amount of force it takes to bend the pizza in the first place . so , what 's the conclusion ? when you fold the pizza at the crust , you make it into a shape where a lot of force is needed to bend the tip down . often gravity is n't strong enough to provide this force . that was kind of a lot of information , so let 's do a quick backwards recap . when pizza is folded at the crust , gravity is n't strong enough to bend the tip . why ? because stretching a pizza is hard . and to bend the tip downwards , the pizza would have to stretch , because the shape the pizza would be in , the droopy taco shape , is n't isometric to the original flat pizza . why ? because of math . as the pizza example shows , we can learn a lot by looking at the mathematical properties of different shapes . and it 's especially nice when those shapes happen to be pizza slices .
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so how can you stop all that cheese from falling off ? you might know some tricks : you can use two hands -- not so classy , or you can use a paper plate and allow only the tip of the pizza to peek out . there 's one other trick , though : holding the crust , you can sort of fold the slice down the middle .
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humans and mother nature alike use thin-sheet physics to build specific shapes . for example , a plant might sprout a baby leaf , and that leaf might start out flat . but then the plant sends signals telling the cells on the outside of the leaf to grow more quickly than the cells in the middle . this situation leads to the formation of a particular kind of feature on the edge of the leaf . what do you think that structure might be ? [ hint : even though they ’ re not exactly leaves , daffodil “ trumpets ” are a great example of this phenomenon . ]
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what 's that sound ? depending on whom you ask , the crackle of popping joints is either the sound of sweet relief or the noxious tones of a stomach-turning habit . really , though . what 's that sound ? i mean , why does bending your joints in a certain way make them pop like that ? scientists have offered several explanations , including rapidly stretching ligaments , and in severe cases , actual bones grinding against each other . but the most common explanation for why your stretched-out joints sound like bubbles popping is that , well , there are bubbles in there . the joints in your fingers are the easiest ones to crack , but many people also crack the joints between vertebrae in their neck and back , and even their hips , wrists , shoulders and so on . all these joints are synovial joints , and they 're the most flexible ones in your body . the space between the two bones is filled with a viscous liquid , synovial fluid , which contains long , lubricating molecules , like hyaluronic acid and lubricin . synovial fluid is more or less the texture of egg yolk and its primary purpose is to cushion the bones and help them glide past each other . it also contains phagocytic cells that help clean up any bone or cartilage debris that ends up in the joint . but the reason it 's important for knuckle cracking is that , like other fluids in your body , it contains lots of dissolved gas molecules . knuckle-crackers know that to get that satisfying pop , you stretch the joint farther than it normally goes by bending your fingers backwards , for example . when you do that , the bones move away from each other . the space between bones gets bigger , but the amount of synovial fluid stays constant . that creates a low-pressure zone that pulls dissolved gases out of the synovial fluid , just like the carbon dioxide that fizzes out of soda when you twist open the cap . inside the joint , the escaping gases form a bubble with a pop . but the bubble does n't last long . the surrounding fluid presses on it until it finally collapses . the bubble 's gases scatter throughout the synovial cavity and slowly dissolve back into the fluid over the course of about twenty minutes , which is why it can take a while before you can pop the same joint again . some scientists think there may actually be two pops . one when the bubble forms , and another when it bursts . popping a joint temporarily enlarges it , which may be why dedicated knuckle- , neck- and back-crackers say the habit makes their joints feel looser and more flexible . but you may have heard from a concerned relative or annoyed officemate that cracking your joints will give you arthritis . a doctor named donald unger heard this , too . so , determined to disprove his mother 's warnings , he cracked the knuckles of his left hand repeatedly for 50 years , while the right-hand knuckles went unpopped . 36,500 cracks later , both hands were arthritis-free . for this selfless act of devotion to science , dr. unger received an ig nobel prize , a parody of the nobel prize that recognizes wacky , but weirdly fascinating , scientific accomplishments . unger wrote that his results should prompt investigation into other parental beliefs , like the importance of eating spinach . the jury 's still out on that one . as for knuckle-cracking , one study suggests that all that joint stretching and bubble bursting can cause your hands to swell and weaken your grip . but the biggest proven danger seems to be annoying those around you .
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when you do that , the bones move away from each other . the space between bones gets bigger , but the amount of synovial fluid stays constant . that creates a low-pressure zone that pulls dissolved gases out of the synovial fluid , just like the carbon dioxide that fizzes out of soda when you twist open the cap .
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what feature of synovial fluid is responsible for the joint 's popping ?
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earthquakes have always been a terrifying phenomenon , and they 've become more deadly as our cities have grown , with collapsing buildings posing one of the largest risks . why do buildings collapse in an earthquake , and how can it be prevented ? if you 've watched a lot of disaster films , you might have the idea that building collapse is caused directly by the ground beneath them shaking violently , or even splitting apart . but that 's not really how it works . for one thing , most buildings are not located right on a fault line , and the shifting tectonic plates go much deeper than building foundations . so what 's actually going on ? in fact , the reality of earthquakes and their effect on buildings is a bit more complicated . to make sense of it , architects and engineers use models , like a two-dimensional array of lines representing columns and beams , or a single line lollipop with circles representing the building 's mass . even when simplified to this degree , these models can be quite useful , as predicting a building 's response to an earthquake is primarily a matter of physics . most collapses that occur during earthquakes are n't actually caused by the earthquake itself . instead , when the ground moves beneath a building , it displaces the foundation and lower levels , sending shock waves through the rest of the structure and causing it to vibrate back and forth . the strength of this oscillation depends on two main factors : the building 's mass , which is concentrated at the bottom , and its stiffness , which is the force required to cause a certain amount of displacement . along with the building 's material type and the shape of its columns , stiffness is largely a matter of height . shorter buildings tend to be stiffer and shift less , while taller buildings are more flexible . you might think that the solution is to build shorter buildlings so that they shift as little as possible . but the 1985 mexico city earthquake is a good example of why that 's not the case . durng the quake , many buildings between six and fifteen stories tall collapsed . what 's strange is that while shorter buildings nearby did keep standing , buildings taller than fifteen stories were also less damaged , and the midsized buildings that collapsed were observed shaking far more violently than the earthquake itself . how is that possible ? the answer has to do with something known as natural frequency . in an oscillating system , the frequency is how many back and forth movement cycles occur within a second . this is the inverse of the period , which is how many seconds it takes to complete one cycle . and a building 's natural frequency , determined by its mass and stiffness , is the frequency that its vibrations will tend to cluster around . increasing a building 's mass slows down the rate at which it naturally vibrates , while increasing stiffness makes it vibrate faster . so in the equation representing their relationship , stiffness and natural frequency are proportional to one another , while mass and natural frequency are inversely proportional . what happened in mexico city was an effect called resonance , where the frequency of the earthquake 's seismic waves happen to match the natural frequency of the midsized buildings . like a well-timed push on a swingset , each additional seismic wave amplified the building 's vibration in its current direction , causing it to swing even further back , and so on , eventually reaching a far greater extent than the initial displacement . today , engineers work with geologists and seismologists to predict the frequency of earthquake motions at building sites in order to prevent resonance-induced collapses , taking into account factors such as soil type and fault type , as well as data from previous quakes . low frequencies of motion will cause more damage to taller and more flexible buildings , while high frequencies of motion pose more threat to structures that are shorter and stiffer . engineers have also devised ways to abosrb shocks and limit deformation using innovative systems . base isolation uses flexible layers to isolate the foundation 's displacement from the rest of the building , while tuned mass damper systems cancel out resonance by oscillating out of phase with the natural frequency to reduce vibrations . in the end , it 's not the sturdiest buildings that will remain standing but the smartest ones .
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in an oscillating system , the frequency is how many back and forth movement cycles occur within a second . this is the inverse of the period , which is how many seconds it takes to complete one cycle . and a building 's natural frequency , determined by its mass and stiffness , is the frequency that its vibrations will tend to cluster around . increasing a building 's mass slows down the rate at which it naturally vibrates , while increasing stiffness makes it vibrate faster .
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the natural period of a building is :
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many modern musical instruments are cumbersome or have a lot of parts . some need a stand or a stool . but the cajon is a drum , a stand and a seat all in one convenient box . and this simplicity may be key to its journey across continents and cultures to become one of the most popular percussion instruments in the world today . the cajon 's story begins in west africa , whose indigenousness people had rich musical traditions centered on drumming and dancing . when many of them were captured and brought to the americas as slaves , they brought this culture with them , but without their native instruments , they had to improvise . african slaves in coastal peru did n't have the materials or the opportunity to craft one of their traditional drums such as a djembe or a djun djun . but what they did have were plenty of shipping crates . not only were these readily accessible , but their inconspicuous appearance may have helped get around laws prohibiting slaves from playing music . early peruvian cajons consisted of a simple box with five thick wooden sides . the sixth side , made of a thinner sheet of wood , would be used as the striking surface , or more commonly known as the tapa . a sound hole was also cut into the back to allow the sound to escape . as an afro-peruvian culture developed , and new forms of music and dance , such as zamacueca , festejo and landó were born , the cajon became a dedicated musical instrument in its own right . early modifications involved simply bending the planks of the box to tweak the sound , and when abolition of slavery introduced the cajon to a broader population , more improvisation and experimentation soon followed . perhaps the person most responsible for introducing the cajon to european audiences was spanish flamenco guitarist paco de lucía . when touring in peru in 1977 , he and his percussionist rubem dantas discovered the cajon and brought it back to spain , recognizing its potential for use in flamenco music . by stretching guitar strings along the inside of the tapa , the flamenco musicians were able to create a buzz-like snare sound . combined with the regular base tone , this gave the cajon a sound close to a basic drum set . the cajon quickly caught on , not only becoming standard in flamenco , but being used in genres like folk , jazz , blues and rock . today , many specialized cajons are manufactured , some with adjustable strings , some with multiple playing surfaces , and some with a snare mechansim . but the basic concept remains the same , and the story of the cajon shows that the simplest things can have the most amazing potential when you think outside and inside the box .
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combined with the regular base tone , this gave the cajon a sound close to a basic drum set . the cajon quickly caught on , not only becoming standard in flamenco , but being used in genres like folk , jazz , blues and rock . today , many specialized cajons are manufactured , some with adjustable strings , some with multiple playing surfaces , and some with a snare mechansim .
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flamenco , jazz and rock are some of the musical genres using the cajon today . which other musical styles do you think could benefit from the cajon ?
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you might just want to sneak up so you don ’ t sprinkle any dirt at the bottom of this place where we turned it over . yeah ok. look at that soil , it is all cake looking . yeah it is . where are we ? look up yonder . to the left oh wow ! ok , let me get the soil before you start whacking ok ? oh yeah . salt blast covered . here we can see evidence of the mining . now this mine closed , many years ago . the bottom is glass-covered houston . yeah , white glass . so if we look into the quarry in the normal daylight in the absence of the snow it would look a bit like a lunar landscape . no the black stuff that is that stuff is crystal , that is the crystal in rocks , now i say that for one specific reason because during the apollo programme the astronauts , they came back from the moon with bucket loads and bucket loads of moon rock and dust . that part of it is . very good . and upon analysis they were really , really surprised to find that there were a number of elements including yttrium which existed at a much much higher abundance on the moon which happens to be the deepest penetration that bowler made . so we are in ytterby in sweden and it ’ s a really nice day and we have come to the ytterby quarry , or ytterby groover , which is actually the birthplace for 4 of the elements and really the one we are going to talk about now is this one right here yttrium . it was first discovered in this quarry from a really horrible black lump of mineral which people thought was coal . and over a period of 40 years from the late 1700s on , some scientists over in arbo did a lot of work in refining this material and they found a new earth or yttria . ok this was yttrium and oxygen and they couldn ’ t get the oxygen out by using traditional reductive methods , metal making methods like burning with carbon and charcoal . so the yttria survived and it was known for about 40 years before the german scientist volla , decided to react the yttria with a much more reactive element , potassium . the potassium wrestled and ripped out the oxygen and he made yttrium metal for the first time . yttrium its used in a whole range of different things , it ’ s used in semi conductors , where there is yttrium , barium , copper oxides , the 1-2-3 complexes that we know of and it ’ s used for a whole range of applications . it ’ s used in laser technologies to make very intense pulses of light , for technologies like cds and leds etc. , etc. , but a massive , massive area . another activity of another use for yttrium is actually in the use of yttrium oxisulphide which is used as an additive in glass it makes glass really tough , like bullet proof glass it makes it very shock resistant and very very resistant towards temperature changes , so it is a very useful additive in glasses and glassy materials . make sure you don ’ t fall over the rock so yttrium itself is a really quite nice lustrous soft metal from group 3 of the periodic table , it burns really readily in an oxygen rich atmosphere and reacts quite well with water in the atmosphere as well . so you have to be very careful with yttrium because it oxidises and it is really quite easy to destroy . that ’ s yttrium metal , just as turnings . so we have to handle this under nitrogen because generally it will form an oxide layer and then you would not be able to do any chemistry with it . yttrium is an element which is not again particularly widely studied in chemistry , much less so than its neighbour zirconium , and but again it ’ s an area where chemists now are starting to focus rather more . if it is really finely divided then it might burst into flames , in fact , all metals if they are finely divided they are quite likely to spontaneously combust .
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so you have to be very careful with yttrium because it oxidises and it is really quite easy to destroy . that ’ s yttrium metal , just as turnings . so we have to handle this under nitrogen because generally it will form an oxide layer and then you would not be able to do any chemistry with it .
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why does stephen manipulate yttrium inside a glove box full of nitrogen ?
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translator : jessica ruby reviewer : caroline cristal let 's say that it would take you ten minutes to solve this puzzle . how long would it take if you received constant electric shocks to your hands ? longer , right ? because the pain would distract you from the task . well , maybe not ; it depends on how you handle pain . some people are distracted by pain . it takes them longer to complete a task , and they do it less well . other people use tasks to distract themselves from pain , and those people actually do the task faster and better when they 're in pain than when they 're not . some people can just send their mind wandering to distract themselves from pain . how can different people be subjected to the exact same painful stimulus and yet experience the pain so differently ? and why does this matter ? first of all , what is pain ? pain is an unpleasant sensory and emotional experience , associated with actual or potential tissue damage . pain is something we experience , so it 's best measured by what you say it is . pain has an intensity ; you can describe it on a scale from zero , no pain , to ten , the most pain imaginable . but pain also has a character , like sharp , dull , burning , or aching . what exactly creates these perceptions of pain ? well , when you get hurt , special tissue damage-sensing nerve cells , called nociceptors , fire and send signals to the spinal cord and then up to the brain . processing work gets done by cells called neurons and glia . this is your grey matter . and brain superhighways carry information as electrical impulses from one area to another . this is your white matter . the superhighway that carries pain information from the spinal cord to the brain is our sensing pathway that ends in the cortex , a part of the brain that decides what to do with the pain signal . another system of interconnected brain cells called the salience network decides what to pay attention to . since pain can have serious consequences , the pain signal immediately activates the salience network . now , you 're paying attention . the brain also responds to the pain and has to cope with these pain signals . so , motor pathways are activated to take your hand off a hot stove , for example . but modulation networks are also activated that deliver endorphins and enkephalins , chemicals released when you 're in pain or during extreme exercise , creating the runner 's high . these chemical systems help regulate and reduce pain . all these networks and pathways work together to create your pain experience , to prevent further tissue damage , and help you to cope with pain . this system is similar for everyone , but the sensitivity and efficacy of these brain circuits determines how much you feel and cope with pain . this is why some people have greater pain than others and why some develop chronic pain that does not respond to treatment , while others respond well . variability in pain sensitivities is not so different than all kinds of variability in responses to other stimuli . like how some people love roller coasters , but other people suffer from terrible motion sickness . why does it matter that there is variability in our pain brain circuits ? well , there are many treatments for pain , targeting different systems . for mild pain , non-prescription medications can act on cells where the pain signals start . other stronger pain medicines and anesthetics work by reducing the activity in pain-sensing circuits or boosting our coping system , or endorphins . some people can cope with pain using methods that involve distraction , relaxation , meditation , yoga , or strategies that can be taught , like cognitive behavioral therapy . for some people who suffer from severe chronic pain , that is pain that does n't go away months after their injury should have healed , none of the regular treatments work . traditionally , medical science has been about testing treatments on large groups to determine what would help a majority of patients . but this has usually left out some who did n't benefit from the treatment or experienced side effects . now , new treatments that directly stimulate or block certain pain-sensing attention or modulation networks are being developed , along with ways to tailor them to individual patients , using tools like magnetic resonance imaging to map brain pathways . figuring out how your brain responds to pain is the key to finding the best treatment for you . that 's true personalized medicine .
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well , maybe not ; it depends on how you handle pain . some people are distracted by pain . it takes them longer to complete a task , and they do it less well . other people use tasks to distract themselves from pain , and those people actually do the task faster and better when they 're in pain than when they 're not .
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doing a task or solving a puzzle always takes longer if you are in pain ________ .
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an estimated 20 million cases of blindness worldwide are caused by cataracts , a curable condition affecting the lens that focuses images onto the eye 's retina . a cataract occurs when proteins in the lens lose their normal arrangement , clumping together in a way that causes discoloration or clouding , and eventually blocks most vision . cataracts can be caused by eye injury , certain medications , ultraviolet radiation , diabetes , smoking , or some genetic disorders . but the most common cause is aging . in the united states , more than 50 % of people over the age of 80 develop them . cataracts were treated over 2,500 years ago in india , though similar procedures may have existed even earlier in ancient egypt and babylon . the most common procedure , called couching , involved pressing a sharp instrument into the eye to loosen and push the clouded lens out of the way . although this could increase the amount of light entering the eye , the lack of a lens would leave the patient 's vision out of focus . despite its low success rate , and high risk of infection or injury , couching is still performed in some parts of the world . later procedures would also focus on removing the cloudy lens , for example , by making an opening in the cornea to pull out the lens along with the membrane capsule surrounding it . while the invention of eyeglasses allowed for some restoration of focus , they had to be extremely thick to help . furthermore , such techniques still caused complications , like damaging the retina , or leaving the eye with uncomfortable stitches . but in the 20th century , something unexpected happened . eye surgeon sir harold ridley was treating world war ii casualties when he noticed that acrylic plastic from a shattered aircraft cockpit had become lodged in a pilot 's eyes without triggering an adverse reaction . this led him to propose surgically implanting artificial lenses into the eye to replace cataracts . and despite initial resistance , the method became standard practice by the 1980s . since ridley 's discovery , the intraocular lens has undergone several improvements . modern lenses can fit into the membrane capsule that the cataract is extracted from , leaving more of the eye 's natural anatomy intact . and the ability to fine-tune the lens curvature allows the surgery to restore a patient 's normal vision without the need for glasses . of course , surgical techniques have also progressed . microscopic procedures use small instruments or lasers to make precise incisions of one or two millimeters in the cornea , while an ultrasound probe breaks up and removes the cataracted lens with minimal trauma to the eye . low-tech versions of this operation have made the surgery quick and inexpensive , helping it spread across the developing world . places like aravind eye hospital in india have pioneered high-volume , low-cost cataract surgery for as little as six dollars . why then , with all these advances , are there still so many blind people in the world ? the main issue is access to health care , with poor infrastructure and a shortage of doctors being a major barrier in many regions . but this is not the only problem . in many rural areas with poor education , blindness is often accepted as an inevitable part of aging , for which someone might not think to seek treatment . this is why information is crucial . increased community awareness programs and the spread of mobile phones mean that many of those who might have remained blind for the rest of their lives due to cataracts are now reachable . and for them , a brighter future is in sight .
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places like aravind eye hospital in india have pioneered high-volume , low-cost cataract surgery for as little as six dollars . why then , with all these advances , are there still so many blind people in the world ? the main issue is access to health care , with poor infrastructure and a shortage of doctors being a major barrier in many regions .
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how many people in the world are estimated to be blind from cataracts ?
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mysteries of vernacular : quarantine , a state , period , or place of strict isolation meant to prevent the spread of disease . in the 14th century , the bubonic plague , later called `` the black death , '' spread across europe with devastating consequences . it 's been estimated that the plague decimated at least one-third of europe 's population . in a vain effort to stave off infection , the italian-speaking port city of ragusa , in what is now croatia , mandated that ships arriving from plague-infested areas remain isolated on the water until it was deemed likely that they were n't carrying a disease . this meant that the entire contents of a ship and all of its passengers were often forced to remain on board for five or six weeks before being let ashore . though the drastic measure was only marginally successful , it was n't long before other port cities followed suit . in 1397 , the official period of isolation imposed on ships and crews was set at forty days . although it did little to protect ports from infection , the directive stuck . from the italian word quaranta , meaning forty , this period of stasis was given the name quarantine . and by the mid 1600s , the word quarantine was being used to describe any place , period , or state of isolation , plague-related or not .
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mysteries of vernacular : quarantine , a state , period , or place of strict isolation meant to prevent the spread of disease . in the 14th century , the bubonic plague , later called `` the black death , '' spread across europe with devastating consequences . it 's been estimated that the plague decimated at least one-third of europe 's population . in a vain effort to stave off infection , the italian-speaking port city of ragusa , in what is now croatia , mandated that ships arriving from plague-infested areas remain isolated on the water until it was deemed likely that they were n't carrying a disease .
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what caused the initial outbreak of the plague ?
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translator : marcia de brito reviewer : ariana bleau lugo ( guitar music throughout ) music is a language . both music and verbal languages serve the same purpose . they are both forms of expression . they can be used as a way to communicate with others . they can be read and written . they can make you laugh or cry , think or question , and can speak to one or many . and both can definitely make you move . in some instances , music works better than the spoken word , because it does n't have to be understood to be effective . although many musicians agree that music is a language , it is rarely treated as such . many of us treat it as something that can only be learned by following a strict regimen , under the tutelage of a skilled teacher . this approach has been followed for hundreds of years with proven success , but it takes a long time . too long . think about the first language you learn as a child . more importantly , think about how you learned it . you were a baby when you first started speaking , and even though you spoke the language incorrectly you were allowed to make mistakes . and the more mistakes you made , the more your parents smiled . learning to speak was not something you were sent somewhere to do only a few times a week . and the majority of the people you spoke to were not beginners . they were already proficient speakers . imagine your parents forcing you to only speak to other babies until you were good enough to speak to them . you would probably be an adult before you could carry on a proper conversation . to use a musical term , as a baby , you were allowed to jam with professionals . if we approach music in the same natural way we approached our first language , we will learn to speak it in the same short time it took to speak our first language . proof of this could be seen in almost any family where a child grows up with other musicians in the family . here are a few keys to follow in learning or teaching music . in the beginning , embrace mistakes , instead of correcting them . like a child playing air guitar , there are no wrong notes . allow young musicians to play and perform with accomplished musicians on a daily basis . encourage young musicians to play more than they practice . the more they play the more they will practice on their own . music comes from the musician , not the instrument . and most importantly , remember that a language works best when we have something interesting to say . many music teachers never find out what their students have to say . we only tell them what they are supposed to say . a child speaks a language for years before they even learn the alphabet . too many rules at the onset , will actually slow them down . in my eyes , the approach to music should be the same . after all , music is a language too .
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translator : marcia de brito reviewer : ariana bleau lugo ( guitar music throughout ) music is a language . both music and verbal languages serve the same purpose . they are both forms of expression .
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both music and verbal languages serve what purpose , according to wooten ?
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when the infamous fictional character , carrie white , left her high school prom hall ablaze , and brought terror upon her town , she relied on her powers of telekinesis , the ability to manipulate physical objects using the power of the mind alone . but while carrie is just a fictional film based upon a fictional book , belief in telekinesis is n't fictional at all . for centuries , humans have claimed they really do have the power to control the motion of objects using only their minds . levitation , opening doors at will and spoon bending are all intriguing examples . it happens in the matrix when neo freezes bullets midair , and it 's a skill that yoda has honed to a t. but is telekinesis real , or just as fictional as carrie , yoda and neo combined ? to investigate , we need to evaluate telekinetic claims through a scientific lens using the scientific method . telekinesis is part of the discipline called parapsychology , in which researchers study psychic phenomena . parapsychologists regard what they do as a science , but other scientists disagree . let 's start with a few basic observations . observation # 1 : while there are loads of anecdotes out there about telekinesis , there 's no scientific proof that it exists ; no studies conducted according to the scientific method and repeated under lab conditions can show that its real . in the 1930s , the so-called father of parapsychology , joseph banks rhine , tested in the lab whether people could use telekinesis to make a dice roll the way they wanted it to . but afterwards , scientists could n't replicate his results , and since replication is key to proving an idea , that was a problem . aside from scientists , there are also countless self-proclaimed telekinetics , but all have been exposed as tricksters , or ca n't perform under conditions where they 're not totally in control , suggesting that they manipulate the situation to get the results they want . today , there 's even a huge stash of prize money available from lots of organizations for anyone who can prove that psychic abilities , like telekinesis , are real . but these riches remain unclaimed . observation # 2 : when we investigate telekinesis , there 's no consensus about what exactly is being measured . are powerful , yoda-like brainwaves at work perhaps ? since nobody agrees , it 's difficult to apply a research standard , something required in all other types of science to test the validity of ideas . observation # 3 : the point of science is to discover the unknown , and in the history of scientific investigation , it 's definitely happened that new discoveries have gone against established science , and even overturned whole branches of science . such discoveries must be proven extra carefully to withstand skepticism . in the case of telekinesis , the idea goes against established science , but lacks the powerful evidence in favor of it . our universe is controlled and explained by the laws of physics , and one of these laws tells us that brain waves ca n't control objects because they 're neither strong nor far-reaching enough to influence anything outside of our skulls . physics also tells us that the only forces that can influence objects from afar are magnetic and gravitational . probably the closest thing to telekinesis that science can explain is the use of thoughts to control a robotic arm . in the brains of stroke patients who ca n't move , researchers can implant tiny wires into the region that controls movement , and then train the patient to concentrate on moving a robotic arm , which acts like an extension of their minds , and it works . it 's amazing , but it is n't telekinesis . the patients thoughts are n't just vague , undetectable things . they 're measurable brain signals , translated through wires into a robot . science can measure , test and explain the motion , and that 's how we 've shown that this kind of mind control is real . science is a slow process of accumulating the evidence that either stands for or against an idea . when we stack up evidence , we can see which tower grows tallest , and in the case of telekinesis , it 's not the tower showing that it exists . some say this mystical phenomenon ca n't fit within the confines of science , and that 's okay . but then telekinesis becomes purely a matter of personal conviction . if something ca n't be assessed scientifically , then it ca n't be described as scientific either . so the results of our investigation reveal that however much we may want to believe that the force really is within us , the case for telekinesis remains weak . sorry neo , carrie and yoda . your skills are mind-blowing , but for now , they belong in the movies .
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since nobody agrees , it 's difficult to apply a research standard , something required in all other types of science to test the validity of ideas . observation # 3 : the point of science is to discover the unknown , and in the history of scientific investigation , it 's definitely happened that new discoveries have gone against established science , and even overturned whole branches of science . such discoveries must be proven extra carefully to withstand skepticism .
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in science , it 's best to rely on _______ to prove a theory .
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a close encounter with a man-eating giant , a sorceress who turns men into pigs , a long-lost king taking back his throne . on their own , any of these make great stories , but each is just one episode in the `` odyssey , '' a 12,000-line poem spanning years of ancient greek history , myth , and legend . how do we make sense of such a massive text that comes from and tells of a world so far away ? the fact that we can read the `` odyssey '' at all is pretty incredible , as it was composed before the greek alphabet appeared in the 8th century bce . it was made for listeners rather than readers , and was performed by oral poets called rhapsodes . tradition identifies its author as a blind man named homer . but no one definitively knows whether he was real or legendary . the earliest mentions of him occur centuries after his era . and the poems attributed to him seem to have been changed and rearranged many times by multiple authors before finally being written down in their current form . in fact , the word rhapsode means stitching together , as these poets combined existing stories , jokes , myths , and songs into a single narrative . to recite these massive epics live , rhapsodes employed a steady meter , along with mnemonic devices , like repetition of memorized passages or set pieces . these included descriptions of scenery and lists of characters , and helped the rhapsode keep their place in the narrative , just as the chorus or bridge of a song helps us to remember the next verses . because most of the tales were familiar to the audience , it was common to hear the sections of the poem out of order . at some point , the order became set in stone and the story was locked into place as the one we read today . but since the world has changed a bit in the last several thousand years , it helps to have some background before jumping in . the `` odyssey '' itself is a sequel to homer 's other famous epic , the `` iliad , '' which tells the story of the trojan war . if there 's one major theme uniting both poems , it 's this : do not , under any circumstances , incur the wrath of the gods . the greek pantheon is a dangerous mix of divine power and human insecurity , prone to jealousy and grudges of epic proportions . and many of the problems faced by humans in the poems are caused by their hubris , or excessive pride in believing themselves superior to the gods . the desire to please the gods was so great that the ancient greeks traditionally welcomed all strangers into their homes with generosity for fear that the strangers might be gods in disguise . this ancient code of hospitality was called xenia . it involved hosts providing their guests with safety , food , and comfort , and the guests returning the favor with courtesy and gifts if they had them . xenia has a significant role in the `` odyssey , '' where odysseus in his wanderings is the perpetual guest , while in his absence , his clever wife penelope plays non-stop host . the `` odyssey '' recounts all of odysseus 's years of travel , but the narrative begins in medias res in the middle of things . ten years after the trojan war , we find our hero trapped on an island , still far from his native ithaca and the family he has n't seen for 20 years . because he 's angered the sea god poseidon by blinding his son , a cyclops , odysseus 's passage home has been fraught with mishap after mishap . with trouble brewing at home and gods discussing his fate , odysseus begins the account of those missing years to his hosts . one of the most fascinating things about the `` odyssey '' is the gap between how little we know about its time period and the wealth of detail the text itself contains . historians , linguists , and archeologists have spent centuries searching for the ruins of troy and identifying which islands odysseus visited . just like its hero , the 24-book epic has made its own long journey through centuries of myth and history to tell us its incredible story today .
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it was made for listeners rather than readers , and was performed by oral poets called rhapsodes . tradition identifies its author as a blind man named homer . but no one definitively knows whether he was real or legendary .
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the oral tradition of `` iliad '' and `` odyssey '' make these stories cultural , communal , entertainment experiences . since homer ’ s time , in what ways has public , communal entertainment changed ?
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it 's midnight and all is still , except for the soft skittering of a gecko hunting a spider . geckos seem to defy gravity , scaling vertical surfaces and walking upside down without claws , adhesive glues or super-powered spiderwebs . instead , they take advantage of a simple principle : that positive and negative charges attract . that attraction binds together compounds , like table salt , which is made of positively charged sodium ions stuck to negatively charged chloride ions . but a gecko 's feet are n't charged and neither are the surfaces they 're walking on . so , what makes them stick ? the answer lies in a clever combination of intermolecular forces and stuctural engineering . all the elements in the periodic table have a different affinity for electrons . elements like oxygen and fluorine really , really want electrons , while elements like hydrogen and lithium do n't attract them as strongly . an atom 's relative greed for electrons is called its electronegativity . electrons are moving around all the time and can easily relocate to wherever they 're wanted most . so when there are atoms with different electronegativities in the same molecule , the molecules cloud of electrons gets pulled towards the more electronegative atom . that creates a thin spot in the electron cloud where positive charge from the atomic nuclei shines through , as well as a negatively charged lump of electrons somewhere else . so the molecule itself is n't charged , but it does have positively and negatively charged patches . these patchy charges can attract neighboring molecules to each other . they 'll line up so that the positive spots on one are next to the negative spots on the other . there does n't even have to be a strongly electronegative atom to create these attractive forces . electrons are always on the move , and sometimes they pile up temporarily in one spot . that flicker of charge is enough to attract molecules to each other . such interactions between uncharged molecules are called van der waals forces . they 're not as strong as the interactions between charged particles , but if you have enough of them , they can really add up . that 's the gecko 's secret . gecko toes are padded with flexible ridges . those ridges are covered in tiny hair-like structures , much thinner than human hair , called setae . and each of the setae is covered in even tinier bristles called spatulae . their tiny spatula-like shape is perfect for what the gecko needs them to do : stick and release on command . when the gecko unfurls its flexible toes onto the ceiling , the spatulae hit at the perfect angle for the van der waals force to engage . the spatulae flatten , creating lots of surface area for their positively and negatively charged patches to find complimentary patches on the ceiling . each spatula only contributes a minuscule amount of that van der waals stickiness . but a gecko has about two billion of them , creating enough combined force to support its weight . in fact , the whole gecko could dangle from a single one of its toes . that super stickiness can be broken , though , by changing the angle just a little bit . so , the gecko can peel its foot back off , scurrying towards a meal or away from a predator . this strategy , using a forest of specially shaped bristles to maximize the van der waals forces between ordinary molecules has inspired man-made materials designed to imitate the gecko 's amazing adhesive ability . artificial versions are n't as strong as gecko toes quite yet , but they 're good enough to allow a full-grown man to climb 25 feet up a glass wall . in fact , our gecko 's prey is also using van der waals forces to stick to the ceiling . so , the gecko peels up its toes and the chase is back on .
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elements like oxygen and fluorine really , really want electrons , while elements like hydrogen and lithium do n't attract them as strongly . an atom 's relative greed for electrons is called its electronegativity . electrons are moving around all the time and can easily relocate to wherever they 're wanted most .
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an atom 's electronegativity is its _____ .
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would you like to know what 's in our future ? what 's going to happen tomorrow , next year , or even a millennium from now ? well , you 're not alone . everyone from governments to militaries to industry leaders do , as well , and they all employ people called futurists who attempt to forecast the future . some are able to do this with surprising accuracy . in the middle of the 20th century , a think tank known as the rand corporation consulted dozens of scientists and futurists who together forecast many of the technologies we take for granted today , including artificial organs , the use of birth control pills , and libraries able to look up research material for the reader . one way futurists arrive at their predictions is by analyzing movements and trends in society , and charting the paths they are likely to follow into the future with varying degrees of probability . their work informs the decisions of policymakers and world leaders , enabling them to weigh options for the future that otherwise could not have been imagined in such depth or detail . of course , there are obvious limits to how certain anyone can be about the future . there are always unimaginable discoveries that arise which would make no sense to anyone in the present . imagine , for example , transporting a physicist from the middle of the 19th century into the 21st . you explain to him that a strange material exists , uranium 235 , that of its own accord can produce enough energy to power an entire city , or destroy it one fell swoop . `` how can such energy come from nowhere ? '' he would demand to know . `` that 's not science , that 's magic . '' and for all intents and purposes , he would be right . his 19th century grasp of science includes no knowledge of radioactivity or nuclear physics . in his day , no forecast of the future could have predicted x-rays , or the atom bomb , let alone the theory of relativity or quantum mechanics . as arthur c. clarke has said , `` any sufficiently advanced technology is indistinguishable from magic . '' how can we prepare , then , for a future that will be as magical to us as our present would appear to someone from the 19th century ? we may think our modern technology and advanced data analysis techniques might allow us to predict the future with much more accuracy than our 19th century counterpart , and rightly so . however , it 's also true that our technological progress has brought with it new increasingly complex and unpredictable challenges . the stakes for future generations to be able to imagine the unimaginable are higher than ever before . so the question remains : how do we do that ? one promising answer has actually been with us since the 19th century and the industrial revolution that laid the foundation for our modern world . during this time of explosive development and invention , a new form of literature , science fiction , also emerged . inspired by the innovations of the day , jules verne , h.g . wells , and other prolific thinkers explored fantastic scenarios , depicting new frontiers of human endeavor . and throughout the 20th century and into the 21st , storytellers have continued to share their visions of the future and correctly predicted many aspects of the world we inhabit decades later . in `` brave new world , '' aldous huxley foretold the use of antidepressants in 1932 , long before such medication became popular . in 1953 , ray bradbury 's `` fahrenheit 451 , '' forecast earbuds , `` thimble radios , '' in his words . and in `` 2001 : a space odyssey , '' arthur c. clarke described a portable , flat-screen news pad in 1968 . in works that often combine entertainment and social commentary , we are invited to suspend our disbelief and consider the consequences of radical shifts in familiar and deeply engrained institutions . in this sense , the best science fiction fulfills the words of philosopher michel foucault , `` i 'm no prophet . my job is making windows where there were once walls . '' free from the constraints of the present and our assumptions of what 's impossible , science fiction serves as a useful tool for thinking outside of the box . many futurists recognize this , and some are beginning to employ science fictions writers in their teams . just recently , a project called iknow proposed scenarios that look much like science fiction stories . they include the discovery of an alien civilization , development of a way for humans and animals to communicate flawlessly , and radical life extension . so , what does the future hold ? of course , we ca n't know for certain , but science fiction shows us many possibilities . ultimately , it is our responsibility to determine which we will work towards making a reality .
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would you like to know what 's in our future ? what 's going to happen tomorrow , next year , or even a millennium from now ?
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can we know in advance exactly how the future is going to look like ?
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today when people complain about the state of american politics , they often mention the dominance of the democratic and republican parties , or the sharp split between red and blue states . but while it may seem like both of these things have been around forever , the situation looked quite different in 1850 , with the republican party not yet existing , and support for the dominant democrats and whigs cutting across geographic divides . the collapse of this second party system was at the center of increasing regional tensions that would lead to the birth of the republican party , the rise of abraham lincoln as its leader , and a civil war that would claim over half a million lives . and if this collapse could be blamed on a single event , it would be the kansas-nebraska act of 1854 . the story starts with the missouri compromise of 1820 . to balance the number of slave states and free states in the union , it allowed slavery in the newly admitted state of missouri , while making it off limits in the remaining federally administered louisiana territory . but compromises tend to last only as long as they 're convenient , and by the early 1850s , a tenacious democratic senator from illionis named stephen a. douglas found its terms very inconvenient . as an advocate of western expansion , he promoted constructing a transcontinental railroad across the northern plains with an eastern terminus in chicago , where he happened to own real estate . for his proposal to succeed , douglas felt that the territories through which the railroad passed , would have to be formally organized , which required the support of southern politicians . he was also a believer in popular sovereignty , arguing that the status of slavery in a territory should be decided by its residents rather than congress . so douglas introduced a bill designed to kill two birds with one stone . it would divide the large chunk of incorporated land into two new organized territories : nebraska and kansas , each of which would be open to slavery if the population voted to allow it . while douglas and his southern supporters tried to frame the bill as protecting the political rights of settlers , horrified northerners recognized it as repealing the 34-year-old missouri compromise and feared that its supporters ' ultimate goal was to extend slavery to the entire nation . congress was able to pass the kansas-nebraska act , but at the huge cost of bitterly dividing the nation , with 91 % of the opposition coming from northerners . in the house of representatives , politicians traded insults and brandished weapons until a sargent at arms restored order . president pierce signed the bill into law amidst a storm of protest , while georgia 's alexander stephens , future confederate vice president , hailed the act 's passage as , `` glory enough for one day . '' the new york tribune reported , `` the unanimous sentiment of the north is indignant resistance . '' douglas even admitted that he could travel from washington d.c. to chicago by the light of his own burning effigies . the political consequences of the kansas-nebraska act were stunning . previously , both whigs and democrats had included northern and southern lawmakers united around various issues , but now slavery became a dividing factor that could not be ignored . congressmen from both parties spoke out against the act , including an illinois whig named abraham lincoln , denouncing `` the monstrous injustice of slavery '' in an 1854 speech . by this time the whigs had all but ceased to exist , irreparably split between their northern and southern factions . in the same year , the new republican party was founded by the anti-slavery elements from both existing parties . although lincoln still ran for senate as a whig in 1854 , he was an early supporter of the new party , and helped to recruit others to its cause . meanwhile the democratic party was shaken when events in the newly formed kansas territory revealed the violent consequences of popular sovereignty . advertisements appeared across the north imploring people to emigrate to kansas to stem the advance of slavery . the south answered with border ruffians , pro-slavery missourians who crossed state lines to vote in fraudulent elections and raid anti-slavery settlements . one northern abolitionist , john brown , became notorious following the pottawatomie massacre of 1856 when he and his sons hacked to death five pro-slavery farmers with broad swords . in the end , more than 50 people died in bleeding kansas . while nominally still a national party , douglas 's democrats were increasingly divided along sectional lines , and many northern members left to join the republicans . abraham lincoln finally took up the republican party banner in 1856 and never looked back . that year , john c. fremont , the first republican presidential candidate , lost to democrat , james buchanan , but garnered 33 % of the popular vote all from northern states . two years later , lincoln challenged douglas for his illinois senate seat , and although he lost that contest , it elevated his status among republicans . lincoln would finally be vindicated in 1860 , when he was elected president of the united states , defeating in his own home state , a certain northern democrat , who was finally undone by the disastrous aftermath of the law he had masterminded . americans today continue to debate whether the civil war was inevitable , but there is no doubt that the kansas-nebraska act made the ghastly conflict much more likely . and for that reason , it should be remembered as one of the most consequential pieces of legislation in american history .
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douglas even admitted that he could travel from washington d.c. to chicago by the light of his own burning effigies . the political consequences of the kansas-nebraska act were stunning . previously , both whigs and democrats had included northern and southern lawmakers united around various issues , but now slavery became a dividing factor that could not be ignored .
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passage of the kansas-nebraska act resulted in ________ .
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he was one of the most fearsome warlords who ever lived , waging an unstoppable conquest across the eurasian continent . but was genghis khan a vicious barbarian or a unifier who paved the way for the modern world ? we 'll see in `` history vs. genghis khan . '' `` order , order . now who 's the defendant today ? khan ! '' `` i see your honor is familiar with genghis khan , the 13th century warlord whose military campaigns killed millions and left nothing but destruction in their wake . '' `` objection . first of all , it 's pronounced genghis kahn . '' `` really ? '' `` in mongolia , yes . regardless , he was one of the greatest leaders in human history . born temüjin , he was left fatherless and destitute as a child but went on to overcome constant strife to unite warring mongol clans and forge the greatest empire the world had seen , eventually stretching from the pacific to europe 's heartland . '' `` and what was so great about invasion and slaughter ? northern china lost 2/3 of its population . '' `` the jin dynasty had long harassed the northern tribes , paying them off to fight each other and periodically attacking them . genghis khan was n't about to suffer the same fate as the last khan who tried to unite the mongols , and the demographic change may reflect poor census keeping , not to mention that many peasants were brought into the khan 's army . '' `` you can pick apart numbers all you want , but they wiped out entire cities , along with their inhabitants . '' `` the khan preferred enemies to surrender and pay tribute , but he firmly believed in loyalty and diplomatic law . the cities that were massacred were ones that rebelled after surrendering , or killed as ambassadors . his was a strict understanding of justice . '' `` multiple accounts show his army 's brutality going beyond justice : ripping unborn children from mothers ' wombs , using prisoners as human shields , or moat fillers to support siege engines , taking all women from conquered towns -- '' `` enough ! how barbaric ! '' `` is that really so much worse than other medieval armies ? '' `` that does n't excuse genghis khan 's atrocities . '' `` but it does make genghis khan unexceptional for his time rather than some bloodthirsty savage . in fact , after his unification of the tribes abolished bride kidnapping , women in the mongol ranks had it better than most . they controlled domestic affairs , could divorce their husbands , and were trusted advisors . temüjin remained with his first bride all his life , even raising her possibly illegitimate son as his own . '' `` regardless , genghis khan 's legacy was a disaster : up to 40 million killed across eurasia during his descendents ' conquests . 10 % of the world population . that 's not even counting casualties from the black plague brought to europe by the golden horde 's siege of kaffa . '' `` surely that was n't intentional . '' `` actually , when they saw their own troops dying of the plague , they catapulted infected bodies over the city walls . '' `` blech . '' `` the accounts you 're referencing were written over a hundred years after the fact . how reliable do you think they are ? plus , the survivors reaped the benefits of the empire genghis khan founded . '' `` benefits ? '' `` the mongol empire practiced religious tolerance among all subjects , they treated their soldiers well , promoted based on merit , rather than birth , established a vast postal system , and inforced universal rule of law , not to mention their contribution to culture . '' `` you mean like hulagu khan 's annihilation of baghdad , the era 's cultural capital ? libraries , hospitals and palaces burned , irrigation canals buried ? '' `` baghdad was unfortunate , but its kalif refused to surrender , and hulagu was later punished by berke khan for the wanton destruction . it was n't mongol policy to destroy culture . usually they saved doctors , scholars and artisans from conquered places , and transferred them throughout their realm , spreading knowledge across the world . '' `` what about the devastation of kievan rus , leaving its people in the dark ages even as the renaissance spread across western europe ? '' `` western europe was hardly peaceful at the time . the stability of mongol rule made the silk road flourish once more , allowing trade and cultural exchange between east and west , and its legacy forged russia and china from warring princedoms into unified states . in fact , long after the empire , genghis khan 's descendants could be found among the ruling nobility all over eurasia . '' `` not surprising that a tyrant would inspire further tyrants . '' `` careful what you call him . you may be related . '' `` what ? '' `` 16 million men today are descended from genghis khan . that 's one in ever 200 . '' for every great conqueror , there are millions of conquered . whose stories will survive ? and can a leader 's historical or cultural signifigance outweigh the deaths they caused along the way ? these are the questions that arise when we put history on trial .
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now who 's the defendant today ? khan ! '' `` i see your honor is familiar with genghis khan , the 13th century warlord whose military campaigns killed millions and left nothing but destruction in their wake . ''
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what were some reasons for genghis khan ’ s attacking northern china ?
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here 's what has to happen for pregnancy to occur after sexual intercourse . sperm must swim up the vagina , through the cervical opening , upwards through the uterus , and into one of the two fallopian tubes . if an egg , released during that month 's ovulation , is in the tube , one sperm has a chance to fertilize it . contraceptives are designed to prevent this process , and they work in three basic ways . they block the sperm , disable sperm before they reach the uterus , or suppress ovulation . block is the simplest . male and female condoms prevent sperm from coming into contact with the vaginal space . that barrier is also why they , unlike other contraceptive methods , are able to prevent transmission of certain sexually transmitted diseases . meanwhile , the diaphragm , cervical cap , and sponge work by being placed over the cervix , barricading the entrance to the uterus . these contraceptives are sometimes called barrier methods and can be used with spermicides , an example of the second category , disable . a spermicide is a chemical that immobilizes and destroys sperm . today 's spermicides come as foam , cream , jelly , suppositories , and even a thin piece of translucent film that dissolves in the vagina . these products can be inserted directly into the vagina before intercourse , or can be combined with block methods , like a diaphragm or condom , for added proection . the third category for preventing pregnancy works by suppressing the action of an egg maturing in the ovary . if there is n't an egg available in the fallopian tube , there 's nothing for sperm to fertilize . hormonal contraceptives , including the pill , the patch , the depo shot , and the vaginal ring all release synthetic versions of various combinations of progesterone and estrogen . this hormone cocktail suppresses ovulation , keeping the immature egg safely sequestered in the ovary . synthetic progesterone also has a block trick up its sleeve . it makes cervical mucus too thick and sticky for sperm to swim through easily . there are other contraceptives that use multiple approaches at the same time . for example , many iuds , or intrauterine devices , contain synthetic hormones which suppress ovulation . some also contain copper , which disable sperm while also making egg implantation in the uterus difficult . block , disable , or suppress : is one strategy better than the other ? there are differences , but a lot of it has to do with how convenient and easy it is to use each contraceptive correctly . for example , male condoms would be about 98 % effective if everyone used them perfectly . that 98 % means if 100 couples correctly used condoms for a year , two women would get pregnant . but not everyone uses them correctly , so they 're only 82 % effective in practice . other methods , like the patch and pill , are 99 % effective when they 're used perfectly . but in practice , that 's 91 % . spermicide is only 85 % effective , even with perfect usage , and just 71 % effective with typical usage . another important consideration in the choice of contraceptives are side effects , which almost exclusively affect women rather than men . hormonal methods in particular can cause symptoms like headaches , nausea , and high blood pressure , but they vary from woman to woman . that 's why these methods require a prescription from a doctor . the choice of contraceptive method is a personal one , and what works best for you now may change later . scientists also continue to research new methods , such as a male pill that would prevent sperm production . in the meantime , there are quite a few options to block sperm , disable them , or suppress eggs and keep them out of reach .
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another important consideration in the choice of contraceptives are side effects , which almost exclusively affect women rather than men . hormonal methods in particular can cause symptoms like headaches , nausea , and high blood pressure , but they vary from woman to woman . that 's why these methods require a prescription from a doctor . the choice of contraceptive method is a personal one , and what works best for you now may change later .
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methods of contraception are designed :
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