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translator : tom carter reviewer : bedirhan cinar ( stories from the sea : how life came to land ) life for my kind was n't always this way . there was a time when no animals lived on land . all life was in the ocean . the ocean 's where all of us animals got our start , more than half a billion years ago , this is where all animal body types -- or phyla , as scientists call them -- first evolved . you know , there are more than 30 animal phyla , but only a handful of major ones had what it took to do something completely daring : step out of the ocean , and on to dry land . so , which of these land-dwelling phyla first invaded the land ? was it me and my mollusc friends , with our amazing mantles and single foot ? perhaps the chordate crowd , with their notochords , segmented muscles and big bony skeletons . or maybe those lowly annelid worms , with their powerful ringed bodies . or did the arthropods first make landfall , with their little flexible suits of armor -- their exoskeleton ? ah , yes . the arthropods . from crustaceans to millipedes , spiders to insects , the arthropods outnumber all animals on land . so what 's their secret ? their exoskeleton is key , but here 's the real kicker : jointed appendages . they 're like little living swiss army knives : antennae , multiple mouth parts , an obscene number of legs , if you ask me . there 's one group of arthropods -- the insects -- that really rule the land . three body parts , six legs , and an annoying tendency to take over . sure , they have to molt to grow , but that does n't seem to pose a problem . the insects even invented the first wings , and conquered the skies . ah , well . so what if arthropods were the first to reach land and invent flight , a hundred million years before the rest of us ? so what if they pollinate crops around the world , and make up 75 % of all land animal species ? and that for every single human , there 's 200 million of them ? sure , those leggy arthropods may still be in the lead when it comes to conquering land , but we still rule in the sea . there are more species of molluscs in the ocean than any other animal phylum . we 're just getting started up here on land . besides , the seas are rising . just give us some time . who knows who 'll end up ruling this ocean planet ?
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there was a time when no animals lived on land . all life was in the ocean . the ocean 's where all of us animals got our start , more than half a billion years ago , this is where all animal body types -- or phyla , as scientists call them -- first evolved .
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when did animal life first arise ?
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your rich , eccentric uncle just passed away , and you and your 99 nasty relatives have been invited to the reading of his will . he wanted to leave all of his money to you , but he knew that if he did , your relatives would pester you forever . so he is banking on the fact that he taught you everything you need to know about riddles . your uncle left the following note in his will : `` i have created a puzzle . if all 100 of you answer it together , you will share the money evenly . however , if you are the first to find the pattern and solve the problem without going through all of the leg work , you will get the entire inheritance all to yourself . good luck . '' the lawyer takes you and your 99 relatives to a secret room in the mansion that contains 100 lockers , each hiding a single word . he explains : every relative is assigned a number from 1 to 100 . heir 1 will open every locker . heir 2 will then close every second locker . heir 3 will change the status of every third locker , specifically if it 's open , she 'll close it , but if it 's closed , she 'll open it . this pattern will continue until all 100 of you have gone . the words in the lockers that remain open at the end will help you crack the code for the safe . before cousin thaddeus can even start down the line , you step forward and tell the lawyer you know which lockers will remain open . but how ? pause the video now if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 the key is realizing that the number of times a locker is touched is the same as the number of factors in the locker number . for example , in locker # 6 , person 1 will open it , person 2 will close it , person 3 will open it , and person 6 will close it . the numbers 1 , 2 , 3 , and 6 are the factors of 6 . so when a locker has an even number of factors it will remain closed , and when it has an odd number of factors , it will remain open . most of the lockers have an even number of factors , which makes sense because factors naturally pair up . in fact , the only lockers that have an odd number of factors are perfect squares because those have one factor that when multiplied by itself equals the number . for locker 9 , 1 will open it , 3 will close , and 9 will open it . 3 x 3 = 9 , but the 3 can only be counted once . therefore , every locker that is a perfect square will remain open . you know that these ten lockers are the solution , so you open them immediately and read the words inside : `` the code is the first five lockers touched only twice . '' you realize that the only lockers touched twice have to be prime numbers since each only has two factors : 1 and itself . so the code is 2-3-5-7-11 . the lawyer brings you to the safe , and you claim your inheritance . too bad your relatives were always too busy being nasty to each other to pay attention to your eccentric uncle 's riddles .
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3 x 3 = 9 , but the 3 can only be counted once . therefore , every locker that is a perfect square will remain open . you know that these ten lockers are the solution , so you open them immediately and read the words inside : `` the code is the first five lockers touched only twice . ''
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what is the pattern of the numbers of the lockers that remain open ?
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fish are in trouble . the cod population off canada 's east coast collapsed in the 1990s , intense recreational and commercial fishing has decimated goliath grouper populations in south florida , and most populations of tuna have plummeted by over 50 % , with the southern atlantic bluefin on the verge of extinction . those are just a couple of many examples . overfishing is happening all over the world . how did this happen ? when some people think of fishing , they imagine relaxing in a boat and patiently reeling in the day 's catch . but modern industrial fishing , the kind that stocks our grocery shelves , looks more like warfare . in fact , the technologies they employ were developed for war . radar , sonar , helicopters , and spotter planes are all used to guide factory ships towards dwindling schools of fish . long lines with hundreds of hooks or huge nets round up massive amounts of fish , along with other species , like seabirds , turtles , and dolphins . and fish are hauled up onto giant boats , complete with onboard flash freezing and processing facilities . all of these technologies have enabled us to catch fish at greater depths and farther out at sea than ever before . and as the distance and depth of fishing have expanded , so has the variety of species we target . for example , the patagonian toothfish neither sounds nor looks very appetizing . and fishermen ignored it until the late 1970s . then it was rebranded and marketed to chefs in the u.s. as chilean sea bass , despite the animal actually being a type of cod . soon it was popping up in markets all over the world and is now a delicacy . unfortunately , these deep water fish do n't reproduce until they 're at least ten years old , making them extremely vulnerable to overfishing when the young are caught before they 've had the chance to spawn . consumer taste and prices can also have harmful effects . for example , shark fin soup is considered such a delicacy in china and vietnam that the fin has become the most profitable part of the shark . this leads many fishermen to fill their boats with fins leaving millions of dead sharks behind . the problems are n't unique to toothfish and sharks . almost 31 % of the world 's fish populations are overfished , and another 58 % are fished at the maximum sustainable level . wild fish simply ca n't reproduce as fast as 7 billion people can eat them . fishing also has impacts on broader ecosystems . wild shrimp are typically caught by dragging nets the size of a football field along the ocean bottom , disrupting or destroying seafloor habitats . the catch is often as little as 5 % shrimp . the rest is by-catch , unwanted animals that are thrown back dead . and coastal shrimp farming is n't much better . mangroves are bulldozed to make room for shrimp farms , robbing coastal communities of storm protection and natural water filtration and depriving fish of key nursery habitats . so what does it look like to give fish a break and let them recover ? protection can take many forms . in national waters , governments can set limits about how , when , where , and how much fishing occurs , with restrictions on certain boats and equipment . harmful practices , such as bottom trawling , can be banned altogether , and we can establish marine reserves closed to all fishing to help ecosystems restore themselves . there 's also a role for consumer awareness and boycotts to reduce wasteful practices , like shark finning , and push fishing industries towards more sustainable practices . past interventions have successfully helped depleted fish populations recover . there are many solutions . the best approach for each fishery must be considered based on science , respect for the local communities that rely on the ocean , and for fish as wild animals . and then the rules must be enforced . international collaboration is often needed , too , because fish do n't care about our borders . we need to end overfishing . ecosystems , food security , jobs , economies , and coastal cultures all depend on it .
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international collaboration is often needed , too , because fish do n't care about our borders . we need to end overfishing . ecosystems , food security , jobs , economies , and coastal cultures all depend on it .
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what can governments do to prevent overfishing ?
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there is a curse that has plagued humanity since ancient times . the greeks fought it by chewing aromatic resins , while the chinese resorted to egg shells . in the ancient jewish talmud , it 's even considered legal grounds for divorce . this horrible scourge is halitosis , otherwise known as bad breath . but what causes it , and why is it so universally terrifying ? well , think of some of the worst odors you can imagine , like garbage , feces or rotting meat . all of these smells come from the activity of microorganisms , particularly bacteria , and , as disgusting as it may sound , similar bacteria live in the moisture-rich environment of your mouth . do n't panic . the presence of bacteria in your body is not only normal , it 's actually vital for all sorts of things , like digestion and disease prevention . but like all living things , bacteria need to eat . the bacteria in your mouth feed off of mucus , food remnants , and dead tissue cells . in order to absorb nutrients through their cell membranes , they must break down the organic matter into much smaller molecules . for example , they 'll break proteins into their component amino acids and then break those down even further into various compounds . some of the foul-smelling byproducts of these reactions , such as hydrogen sulfide and cadaverine , escape into the air and waft their way towards unsuspecting noses . our sensitivity to these odors and interpretation of them as bad smells may be an evolutionary mechanism warning us of rotten food and the presence of disease . smell is one of our most intimate and primal senses , playing a huge role in our attraction to potential mates . in one poll , 59 % of men and 70 % of women said they would n't go on a date with someone who has bad breath , which may be why americans alone spend $ 1 billion a year on various breath products . fortunately , most bad breath is easily treated . the worst smelling byproducts come from gram-negative bacteria that live in the spaces between gums and teeth and on the back of the tongue . by brushing and flossing our teeth , using antibacterial mouthwash at bedtime , gently cleaning the back of the tongue with a plastic scraper and even just eating a healthy breakfast , we can remove many of these bacteria and their food sources . in some cases , these measures may not be enough due to dental problems , nasal conditions , or rarer ailments , such as liver disease and uncontrolled diabetes . behaviors like smoking and excessive alcohol consumption also have a very recognizable odor . regardless of cause , the bad smell almost always originates in the mouth and not the stomach or elsewhere in the body . but one of the biggest challenges lies in actually determining how our breath smells in the first place , and it 's unclear why . it may be that we 're too acclimatized to the smell inside our own mouths to judge it . and methods like cupping your hands over your mouth , or licking and smelling your wrist do n't work perfectly either . one study showed that even when people do this , they tend to rate the smell subjectively according to how bad they thought it was going to be . but there 's one simple , if socially difficult , way of finding out how your breath smells : just take a deep breath and ask a friend .
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well , think of some of the worst odors you can imagine , like garbage , feces or rotting meat . all of these smells come from the activity of microorganisms , particularly bacteria , and , as disgusting as it may sound , similar bacteria live in the moisture-rich environment of your mouth . do n't panic .
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bacteria cause the smells by breaking down _____ .
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the sight of mistletoe may either send you scurrying , or if you have your eye on someone , awaiting an opportunity beneath its snow white berries , but how did the festive christmas tradition of kissing under mistletoe come about ? the long-lived custom intertwines the mythology and biology of this intriguing plant . there are more than 1,000 species of mistletoe , which grows the world over . in fact , the ancient europeans were so captivated by the plant 's unusual growth habits that they included it in their legends and myths . in ancient rome , pliny the elder described how the druid priesthood in ancient england believed that mistletoe was a plant dropped down from heaven by the gods . that explained its unlikely position amongst the high branches of certain trees . they also believed it had powers of healing and bestowing fertility . meanwhile , scandinavian legend told of the plant 's mystical qualities in the story of the god baldr and his adoring mother frigg , goddess of love , marriage , and fertility . frigg loved her son so much that she commanded every plant , animal , and inanimate object to vow they 'd never harm him . in her fervor , however , she overlooked the mistletoe . the mischievous god loki realized this oversight and pierced baldr 's heart with an arrow carved from a mistletoe branch . frigg cried tears of such sadness that they formed the mistletoe 's pearly berries , making the other gods pity her and agree to resurrect baldr . hearing the news , frigg became so overjoyed that she transformed the mistletoe from a symbol of death into one of peace and love . she mandated a one-day truce for all fights , and that everyone embrace beneath its branches when they passed to spread more love into the world . in the 17th century , british colonists arriving in the new world found a different , but very similar looking , species of mistletoe . they applied it to these tales of magic , fertility , and love , spreading the mistletoe-hanging tradition from europe into america . by the 18th century , people in britain had turned this into a christmas tradition , but this custom comes down to more than just human imagination . all of it was inspired by the plant 's intriguing biology . we see mistletoe as a festive decoration , but draped on tree boughs in the wild , it 's known as a partly parasitic plant . mistletoe relies on modified roots called haustoria that penetrate the tree bark and siphon off the water and minerals trees carry up their trunks to colonize nearby trees with its seeds , mistletoe depends on birds and other creatures to do the dispersing . birds that eat the mistletoe 's sticky white berries sometimes get rid of the gluey seeds by wiping them off onto tree bark . or with a bit of luck , they excrete the indigestible seed onto a tree where it germinates and starts to grow . with its resilience and foliage that stays lush even while the surrounding trees lose their leaves , you can see why mistletoe captivated our superstitious ancestors . they saw these as signs of the plant 's magical qualities and fertility . even today , the mistletoe inspires wonder with the diversity of wildlife it supports . more than just a parasite , it 's also known as a keystone species . it 's eaten by a diversity of animals , including deer , elk , squirrels , chipmunks , porcupines , robins , bluebirds , morning doves , and the butterfly genus delias . some mistletoe species produce dense bushes , which are excellent nesting locations for a variety of birds . and despite their parasitic relationship with trees , mistletoes can also help other plants . for instance , juniper sprouts near mistletoe to benefit from the visiting berry-eating birds . through the many benefits it provides , mistletoe influences diversity , and allows ecosystems to flourish . you might even say that for this iconic plant , life imitates legend . in the wild , mistletoe has the power to bring things together , and in our own traditions , we see that happening , too .
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the sight of mistletoe may either send you scurrying , or if you have your eye on someone , awaiting an opportunity beneath its snow white berries , but how did the festive christmas tradition of kissing under mistletoe come about ? the long-lived custom intertwines the mythology and biology of this intriguing plant .
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the mistletoe ’ s berries represent frigga ’ s :
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in mythological ancient greece , soaring above crete on wings made from wax and feathers , icarus , the son of daedalus , defied the laws of both man and nature . ignoring the warnings of his father , he rose higher and higher . to witnesses on the ground , he looked like a god , and as he peered down from above , he felt like one , too . but , in mythological ancient greece , the line that separated god from man was absolute and the punishment for mortals who attempted to cross it was severe . such was the case for icarus and daedalus . years before icarus was born , his father daedalus was highly regarded as a genius inventor , craftsman , and sculptor in his homeland of athens . he invented carpentry and all the tools used for it . he designed the first bathhouse and the first dance floor . he made sculptures so lifelike that hercules mistook them for actual men . though skilled and celebrated , daedalus was egotistical and jealous . worried that his nephew was a more skillful craftsman , daedalus murdered him . as punishment , daedalus was banished from athens and made his way to crete . preceded by his storied reputation , daedalus was welcomed with open arms by crete 's king minos . there , acting as the palace technical advisor , daedalus continued to push the boundaries . for the king 's children , he made mechanically animated toys that seemed alive . he invented the ship 's sail and mast , which gave humans control over the wind . with every creation , daedalus challenged human limitations that had so far kept mortals separate from gods , until finally , he broke right through . king minos 's wife , pasiphaë , had been cursed by the god poseidon to fall in love with the king 's prized bull . under this spell , she asked daedalus to help her seduce it . with characteristic audacity , he agreed . daedalus constructed a hollow wooden cow so realistic that it fooled the bull . with pasiphaë hiding inside daedalus 's creation , she conceived and gave birth to the half-human half-bull minotaur . this , of course , enraged the king who blamed daedalus for enabling such a horrible perversion of natural law . as punishment , daedalus was forced to construct an inescapable labyrinth beneath the palace for the minotaur . when it was finished , minos then imprisoned daedalus and his only son icarus within the top of the tallest tower on the island where they were to remain for the rest of their lives . but daedalus was still a genius inventor . while observing the birds that circled his prison , the means for escape became clear . he and icarus would fly away from their prison as only birds or gods could do . using feathers from the flocks that perched on the tower , and the wax from candles , daedalus constructed two pairs of giant wings . as he strapped the wings to his son icarus , he gave a warning : flying too near the ocean would dampen the wings and make them too heavy to use . flying too near the sun , the heat would melt the wax and the wings would disintegrate . in either case , they surely would die . therefore , the key to their escape would be in keeping to the middle . with the instructions clear , both men leapt from the tower . they were the first mortals ever to fly . while daedalus stayed carefully to the midway course , icarus was overwhelmed with the ecstasy of flight and overcome with the feeling of divine power that came with it . daedalus could only watch in horror as icarus ascended higher and higher , powerless to change his son 's dire fate . when the heat from the sun melted the wax on his wings , icarus fell from the sky . just as daedalus had many times ignored the consequences of defying the natural laws of mortal men in the service of his ego , icarus was also carried away by his own hubris . in the end , both men paid for their departure from the path of moderation dearly , icarus with his life and daedalus with his regret .
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worried that his nephew was a more skillful craftsman , daedalus murdered him . as punishment , daedalus was banished from athens and made his way to crete . preceded by his storied reputation , daedalus was welcomed with open arms by crete 's king minos .
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why was daedalus banned from athens ?
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many of my friends , teachers , romantic partners and even my parents have all told me to stop fidgeting , `` trace stop shaking your leg . '' but i did n't even know i was doing it mom , geez ! fidgeting friends once upon a time , psychologist sir francis galton was sitting in a lecture , got bored and decided to watch the audience instead of listen to the speaker . ( been there ! ) according to him , these elderly victorian lecture-goers were , `` swaying from side-to-side '' at about `` 1 fidget a minute . '' when the audience 's attention was aroused , he noticed their fidgeting would lessen . in his paper , published in nature , titled `` the measure of fidget '' galton determined people must fidget out of boredom ! this was before discussions about hyperactivity or sugar , or before the television ruined our attention span . this was 1885 ! 130 years ago , people fidgeted . it 's definitely not caused by over-caffeinated , adhd-prone , coddled millennials . instead , fidgeting seems to be part of human nature . the dictionary defines fidgeting as `` small movements , especially of the hands and feet , caused by nervousness or impatience , '' but science has another explanation ; it 's a way to keep my brain active and focused . yep , you heard me , fidgeting may equal focus . hashtag science , yo . when brains are stressed we do n't pay as close attention , and we do n't learn as much ! cognitive load theory says to think of the brain like a cpu ; when too much is going on the brain ca n't focus . so , to offload some of that stress , the brain might trigger our fidgeting ! lower stress is highly associated with better learning and memory performance , so fidgeting can help us learn ! though science is n't sure… because maybe it 's just men… for some reason men fidget twice as often as women , and a 2005 study from the university of hertfordshire found fidgeting can reduce levels of the stress hormone cortisol , which should lower stress . a study in plos one , however , that benefit seems to fall on men who fidgeted . the fidgeting men they tested performed better on cognitive tests and had lower stress , but fidgeting women did neither . another study with adhd kids further muddies the fidgeting waters , as fidgeting does n't help everyone all the time . a study in the journal of abnormal psychology assessed the working memory of young fidgeting boys . when adhd kids were put in a swivel chair and allowed to spin , they performed better on memory tests . however , kids without adhd performed worse when they were allowed to spin , and better when they stayed still . it would seem , though fidgeting may lower stress and help learning , there 's a level where the benefits to our attention and learning disappear . for example , drawing random doodles , kicking feet , or shaking legs may be fine , but drawing specific pictures or walking around the room is too distracting and benefits are lost . so , perhaps boys with adhd need to fidget ? what about girls ? do they get any benefit ? well , a study from september 2015 in the american journal of preventive medicine , looked at 13,000 uk women 12 years apart and found adults who fidgeted , also burned calories ! their results found fidgeters had quote `` better health outcomes , '' than their still counterparts . and another study in medicine & amp ; amp ; science in sports & amp ; amp ; exercise found fidgeting can burn up to 144 calories a day ! that 's more than a can of pop ! some researchers believe fidgeting seems to be an adaptation to our more sedentary lifestyle . but a study in frontiers in psychology looking at memory retention of lectures , and fidgeting… found almost the same as galton in 1885 . if you track the number of fidgets per minute , it 's a good indicator of audience boredom . fidgeting seems to be a representation of our animal brains working hard to keep on task and learning . it can be irksome , but as long as it 's not distracting to others , it 's not necessarily bad , and is ( at least ) burning some calories ! sometimes we 're just… fidgety widgety . do you fidget ? how ? pen clicker ? leg shaker ? finger tapper ? nail biter ? whatchoo got ? tell us your fidgeting functions down below . fidgeting might be annoying to some , but sitting is killing you . yep . your chair . it 's slowing killing you right now . find out more in this video
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a study in plos one , however , that benefit seems to fall on men who fidgeted . the fidgeting men they tested performed better on cognitive tests and had lower stress , but fidgeting women did neither . another study with adhd kids further muddies the fidgeting waters , as fidgeting does n't help everyone all the time . a study in the journal of abnormal psychology assessed the working memory of young fidgeting boys .
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if nervousness is a cause of fidgeting what can students and teachers do to reduce it ?
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nestled in the tissues of your neck is a small unassuming organ that wields enormous power over your body . it 's called the thyroid . like the operations manager in a company , its role is to make sure that the cells in your body are working properly . it does that by using hormones to deliver messages to every single one of them . this high-ranking organ is made up of lobules that each contains smaller cells called follicles , which store the hormones the thyroid sends out into your blood . two of the most important hormones it produces are thyroxine and triiodothyronine , or t3 and t4 . as messengers , the hormone 's job is to instruct every cell in the body when to consume oxygen and nutrients . that maintains the body 's metabolism , the series of reactions our cells perform to provide us with energy . this hormonal notification from the thyroid gets the heart pumping more efficiently , and makes our cells break down nutrients faster . when you need more energy , the thyroid helps by sending out hormones to increase metabolism . ultimately , the thyroid allows our cells to use energy , grow and reproduce . the thyroid is controlled by the pituitary gland , a hormonal gland deep in the brain that oversees the thyroid 's tasks , making sure it knows when to send out its messengers . the pituitary 's role is to sense if hormone levels in the blood are too low or too high , in which case it sends out instructions in the form of the thyroid- stimulating hormone . even in this tightly controlled system , however , management sometimes slips up . certain diseases , growths in the thryoid or chemical imbalances in the body can confuse the organ and make it deaf to the pituitary 's guiding commands . the first problem this causes is hyperthyroidism , which happens when the organ sends out too many hormones . that means the cells are overloaded with instructions to consume nutrients and oxygen . they become overactive as a result , meaning a person with hyperthyroidism experiences a higher metabolism signaled by a faster heartbeat , constant hunger , and rapid weight loss . they also feel hot , sweaty , anxious , and find it difficult to sleep . the opposite problem is hypothyroidism , which happens when the thyroid sends out too few hormones , meaning the body 's cells do n't have as many messengers to guide them . in response , cells grow listless and metabolism slows . people with hypothyroidism see symptoms in weight gain , sluggishness , sensitivity to cold , swollen joints and feeling low . luckily , there are medical treatments that can help trigger the thyroid 's activities again , and bring the body back to a steady metabolic rate . for such a little organ , the thyroid wields an awful lot of power . but a healthy thyroid manages our cells so effectively that it can keep us running smoothly without us even noticing it 's there .
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it 's called the thyroid . like the operations manager in a company , its role is to make sure that the cells in your body are working properly . it does that by using hormones to deliver messages to every single one of them . this high-ranking organ is made up of lobules that each contains smaller cells called follicles , which store the hormones the thyroid sends out into your blood .
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looks up thyroxine and triiodothyronine and try to explain how they deliver messages to the body 's cells .
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translator : ido dekkers reviewer : ariana bleau lugo so what is gravity ? i bet most of you think it 's : `` what goes up , must come down ! '' is that right ? well , sorta , but not really . technically , the law of gravity is an equation . it is : f = g x m1 x m2 / r^2 , where g is the universal gravitational constant , m1 and m2 are the masses of the two objects , and r is the distance between them squared . that was easy , right ? probably not . what does this actually mean ? well it means that - well , everything is attracted to everything else . what i mean by that is if you have two objects , any two objects , they are attracted to each other . ok. let 's try and wrap our minds around this . what happens when you drop a rock off a cliff ? it falls to the earth . right ? well , yes , but something else happens . you see , the law of gravity says that both objects , the rock and the earth , are attracted to each other . this means that the rock falls towards the earth , and the earth falls towards the rock . wait a second - you mean to tell me that if - the earth falls up to meet the rock ? yes , that 's exactly what i 'm saying . and the reason you do n't see the earth fall up to meet the rock is because the objects move towards each other proportionate to their respective masses . the earth is much much much more massive than the rock , so it moves a very very small distance , and the rock is much less massive , so it moves farther with respect to the earth . maybe a better way to understand gravity is to take two teenagers in spacesuits , and place them far out in space - away from all the planets and the stars . it turns out they will be attracted to each other . i 'm not talking about that kind of attraction . see , they have mass , and since they have mass , they will move towards each other . they are attracted to each other . maybe one more thing might help . have you ever played with two magnets ? you know , the magnets with the north and the south poles ? when you take the magnets and put them closer to each other , they move together . they are attracted to each other . and the closer they are , the stronger the attraction . think of the mass of the object like the strength of a magnet and the distance between the objects like the distance between the two magnets . now understand , i 'm not saying that gravity and magnetism are the same , they just behave in a similar way . let 's think of one other thing - astronauts . you know , astronauts , they weigh less on the moon than on the earth . why is that ? well you see , the moon is less massive than the earth . therefore it has a smaller gravitational pull on the astronaut . it 's like the moon is a weaker magnet . they are n't as attracted to each other . distance also plays a role . think back to playing with a magnet . the pull of the magnets towards each other are stronger when they are closer together . the same is true of gravity . for example , the sun is the most massive object near the earth . it dictates most of the gravitational forces in our solar system . it is very very massive . but it is relatively far away , so even though the sun is a much stronger magnet , so to speak , it is a long ways away . therefore the attraction is n't as strong . so let 's look back at that law of gravity . the equation : f = g x m1 x m2 / r ^2 . you see the force of gravity is equal to a number . that 's that universal gravitational constant g times the mass of object one , times the mass of object two . think of m1 being the mass of the sun and m2 being the mass of the earth . and then we divide by the distance between them squared . this determines the force of attraction between the sun and earth . you could just as easily plug in your mass and the earth 's mass and the distance between you and the center of the earth , and find out how much you are attracted to the earth , and the earth attracted to you . so , what 's gravity ? everything is attracted to everything else . everything . oh , one last thing , just to make you wonder . what causes gravity ? why are two objects with mass attracted to each other ? well , the answer is - we do n't know . the cause of gravity remains a mystery to scientists . we do n't really know conclusively what causes gravity . it is one of the great mysteries of science .
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oh , one last thing , just to make you wonder . what causes gravity ? why are two objects with mass attracted to each other ?
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the video uses magnets as an analogy to gravity . in what ways are magnetism and gravity the same ? in what ways are they different ?
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translator : andrea mcdonough reviewer : bedirhan cinar so how many of you have a robot at home ? ok , i see about 20 , 30 hands . that 's actually pretty good . how many of you would want your own personal robot at home ? i know i would ! ok , so why does n't this exist ? why ca n't i go to the convenience store or the department store and , you know , go up to the cashier and say , `` yeah , i want my personal robot '' ? well , i 'm going to talk to you about how to make that happen . the thing that we need to do is to make robots smarter . now , no one will argue that we do n't have robots . we have rovers that are going to mars and are getting science data and expanding our understanding of the world . we have manufacturing robots that are helping to build our cars that we drive today . we even have robots that are helping our military , that are out disposing of bombs so our soldiers can come home safely . so we have all this , so why do n't we have the personal robot ? why do n't i have my robot chef ? because i ca n't cook . ( laughter ) so , here 's one of my robots , this is a simple walking robot , but it is by no means smart . and so , what we need to do is we need to change the definition of what a robot is . how do we do that ? well , the first step , before we even start designing and getting our hands dirty , we have to come up with rules , kind of the laws , rules of conduct . and why is this ? because if these robots are smart , they might be capable of more than we want . and so we have to come up with rules . thou , robot , shall not harm a human . thou shall obey me , and only me . thou shall always protect me at all possible times . so we have to lay the boundaries , the rules of engagement , before we actually start designing . and then we have to come up with tools . so i believe that the way to make robots smarter is to mimic people . now , our brains are complex , there 's a lot going on in there , and so , it 'd be hard to try to open up the brain and actually figure out how to mimic humans . the best way is to observe , is to actually watch people do things , and figure out what are they doing , what are their thoughts , what are their actions , what are their emotions ? and so , part of making robots smarter is actually trying to mimic humans , mimic how we do things , so maybe they can do it a little bit better . and so , some of the tools are varied . and so , i 'm classically trained as an electrical engineer . i never thought i 'd have to understand things like child psychology , infant development . so , understanding that the way infants develop to children , develop to adults , and how they learn and interact is actually important for robotics . i did n't understand that i 'd actually have to watch tapes of monkeys interacting and communicating , because they have a whole social kind of mechanism where they learn from each other , and so that 's really good to make robots smarter . and , of course , neuroscience , i 've always been fascinated with neuroscience , but i never understood that i had to figure out why do the neurons fire , what about the environment helps us to learn , and all of those really contribute to making robots a little bit smarter . and so , some of the things that i do -- and this is just a little snapshot -- one of the things is mirroring . so they say our ability to look in a mirror and wave and actually recognize that the person on the other side is us , that self-awareness , is a sign of intelligence , and that allows us to then look at someone pitch a ball and figure out , `` ok , i know how to pitch a ball , i 'm going to mirror their improvement . '' and so i actually have a robot where we are trying to design a robot health coach . and so , i have an exercise physiologist showing the robot how to do some exercises . you know , we want to get strong . and then , the other thing is learning . so , learning is important . we do this as children , we do this even as adults , we do this as elder . and yet , one form of learning is muscle memory . so how many of you play an instrument ? ok , so when you start off , for example , if you think about the violin , you start off and your instructor might actually come and move your hand a little bit or maybe move your bow a little bit up . so they actually touch you in order to give you muscle memory . and that helps you understand how to do things a little better . and so we actually have a learning methodology where of course , we 're not going to take the motors and move the legs , and so we have to nunchuk to give our robot muscle memory in terms of how to do dance moves . and then , lastly , is creativity . so , you might ask , `` robots ? creativity ? i do n't get this . why does the robot have to be creative ? what about creativity makes them smarter ? '' well , creativity and imagination , those are the things that allow us to create problems when we do n't know how to attack it . they allow us to make something out of nothing . i mean , if you look at the apps that at out there and the tablets , and the ipads , and the iphones , and the androids -- 20 years ago they did n't exist . so , how is it that we got from something where there was nothing and expanded ? it was our imagination . it was our creativity . and these are the things that allow us to figure out new things . and so , i have a robot that is creative , it plays piano , is a composer , and if you listen , it plays `` twinkle , twinkle little star . '' ( music ) so , all of this together , the last thing is interaction . so , you have a robot , you want it to be your playmate , your teacher , your instructor , you want it to interact . and is n't it so cute ? ( laughter ) so , interaction is key , it is key to understanding how to work in our world with us , and so the interaction piece is very important . it deals with communication , it deals with understanding , it deals with gaze , it deals with attention . all of these things together allow that interaction and our robots to be smart . and so these are just some of the tools that we use in order to make robots smarter . so , i want to leave you with one thought . so , i 'm all for robots and smart robots . i mean , that 's what i do , i 'd be out of a job if i did n't believe in that . but yet , where does it end ? how far do we push it ? how far and how smart should we make our smart robots ? thank you . ( applause )
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so , i want to leave you with one thought . so , i 'm all for robots and smart robots . i mean , that 's what i do , i 'd be out of a job if i did n't believe in that .
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generally speaking , robots are mechanical , synthetic , and exist separate from the human body . using your wildest imagination , explain how you think robots and humans may become more closely related in the future .
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so the blue one in the middle of this series is argon , so again this is a very nice glass tube that we ’ ve had made with a low pressure of argon inside . we ’ ve put a potential across from the two ends , here and here , and this excites all the argon molecules inside so you can see this wonderful characteristic eerie blue glow coming off from the argon . argon is one of the noble gases or so-called rare gases . it ’ s not really quite so rare . it consists in really quite a high percentage , nearly one percent of the atmosphere . if i look at the one in the middle i can see lots and lots of lines in the blue and the green region and these are all specific to the individual atoms that are in the tubes themselves . but it ’ s very un-reactive so early chemists found it quite difficult to identify , in fact it was only sir william ramsey that identified the argon in 1894 and he was in fact the first person in britain to win a nobel prize for chemistry . so if we turn off the power to this , we turn off the potential and then we don ’ t excite the molecules so what we ’ d see is just a clear glass tube with no visible sign of anything inside . and only when we turn on the potential that we excite the molecules , so they emit and give us these really quite wonderful colours .
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so the blue one in the middle of this series is argon , so again this is a very nice glass tube that we ’ ve had made with a low pressure of argon inside . we ’ ve put a potential across from the two ends , here and here , and this excites all the argon molecules inside so you can see this wonderful characteristic eerie blue glow coming off from the argon . argon is one of the noble gases or so-called rare gases . it ’ s not really quite so rare .
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why is argon used to fill incandescent light bulbs ?
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you might think you know a lot about native americans through popular movies , books , and classes in school , but it turns out that a lot of what we think we know about famous native american figures is n't quite right . take sacajawea for example . you probably remember her as a beautiful indian woman who lived an exotic life serving as the all-knowing guide for lewis and clark 's famous expedition , right ? well , that 's not exactly how it happened . not much is known about sacajawea 's early childhood , but we do know that she was born in 1788 into the agaidika tribe of the lemhi shoshone in what is now idaho . in 1800 , when she was about 12 years old , sacajawea and several other girls were kidnapped by a group of hidatsa indians . she was taken as a captive to a hidatsa village in present-day north dakota . then , she was sold to a french canadian fur trapper named toussaint charbonneau . within a year or so , she was pregnant with her first child . soon after she became pregnant , the corps of discovery arrived near the hidatsa villages . captains meriwether lewis and william clark built fort mandan there , and then started interviewing people to help guide them on their perilous expedition . they agreed to hire sacajawea 's husband , charbonneau , with the understanding that his lovely wife would also come along as an interpreter . they figured her very presence would help any encounters with native tribes along the way . as clark noted in his journal , `` a woman with a party of men is a token of peace . '' shortly thereafter , sacajawea gave birth to a little boy named jean baptiste charbonneau . clark called him pompy . she carried pompy on a board strapped to her back as the corps of discovery forged on . besides interpreting the language when lewis and clark encountered indians , sacajawea 's activities as a member of the corps included digging for roots , collecting edible plants , and picking berries . in 1805 , the boat they were riding in was capsized . she dove into the water , recovering all the important papers and supplies that would otherwise have been lost , including the journals and records of lewis and clark . later that year , captain lewis and three men scouted 75 miles ahead of the expedition 's main party , crossing the continental divide . the next day they encountered a group of shishones . not only did they prove to be sacajawea 's band , but their leader , chief cameahwait , turned out to be her very own brother . after five years of separation since her kidnapping as a young girl , sacajawea and cameahwait had an emotional reunion . unfortunately , she quickly had to bid farewell to her beloved brother and continue on with the journey . at one point , the expedition became so difficult and freezing , the group was reduced to eating candles to survive . when temperatures finally became more bearable , sacajawea found , dug , and cooked roots to help the group regain their strength . on the return trip , they encountered an indian wearing a beautiful fur robe . lewis and clark wanted to bring the robe to thomas jefferson as a gift but had nothing to trade for it . so , sacajawea agreed to trade her most precious possession , her beaded belt , for the fur . a little over two years after the expedition began , it was finally over , ending in st. louis . today , we learn about sacajawea in school as a heroic guide , but her life , like most everyone 's , was much more complicated than history books sometimes give her credit for .
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the next day they encountered a group of shishones . not only did they prove to be sacajawea 's band , but their leader , chief cameahwait , turned out to be her very own brother . after five years of separation since her kidnapping as a young girl , sacajawea and cameahwait had an emotional reunion . unfortunately , she quickly had to bid farewell to her beloved brother and continue on with the journey .
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chief cameahwait was sacajawea ’ s :
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translator : tom carter reviewer : bedirhan cinar literary critic northrop frye once observed that in our primitive days , our literary heroes were -- well , nearly gods , and as civilization advanced , they came down the mountain of the gods , so to speak , and became more human , more flawed , less heroic . from the divine heroes like hercules , down the mountain below the miraculous but mortal heroes such as beowulf , the great leaders such as king arthur , and the great but flawed heroes like macbeth or othello . below even the unlikely but eventual heroes such as harry potter , luke skywalker , or hiccup , until we reach the bottom and meet the anti-hero . contrary to the sound , the anti-hero is not the villain , not the antagonist . the anti-hero is actually the main character in some contemporary works of literature . guy montag in `` fahrenheit 451 , '' winston smith in `` 1984 , '' who unwittingly ends up challenging those in power -- that is , those who abuse their power to brainwash the populace to believe that the ills of society have been eliminated . ideally , those who challenge the establishment should be wise , confident , brave , physically strong , with a type of charisma that inpires followers . the anti-hero , however , at best demonstrates a few underdeveloped traits , at worst , is totally inept . the story of the anti-hero usually unfolds something like this . the anti-hero initially conforms , ignorantly accepting the established views , a typical , unquestioning , brainwashed member of society . the anti-hero struggles to conform , all the while starting to object , perhaps finding other outsiders with whom to voice his questions , and naïvely , unwisely , sharing those questions with an authority figure . the anti-hero openly challenges society , and tries to fight against the lies and tactics used to oppress the populace . this step , for the anti-hero , is seldom a matter of brave , wise and heroic opposition . maybe the anti-hero fights and succeeds in destroying the oppressive government , with a lot of impossible luck . perhaps he or she runs away , escapes to fight another day . all too often though , the anti-hero is killed , or brainwashed to return to conformity with the masses . no heroic triumph here , no brave individual standing up against impersonal institutions of a modern world , inspiring others to fight , or resourcefully outwitting and outgunning the massive army of the evil empire . our storytelling ancestors calmed our fears of powerlessness by giving us hercules and other heroes strong enough to fight off the demons and monsters that we suspected haunted the night beyond our campfires . but eventually , we realized the monsters did not lie out there , they reside inside of us . beowulf 's greatest enemy was mortality . othello 's , jealousy . hiccup , self-doubt . and in the tales of the ineffectual anti-hero , in the stories of guy montag and winston smith , lie the warnings of contemporary storytellers playing on very primitive fears : that we are not strong enough to defeat the monsters . only this time , not the monsters chased away by the campfire , but the very monsters who built the campfire in the first place .
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the anti-hero , however , at best demonstrates a few underdeveloped traits , at worst , is totally inept . the story of the anti-hero usually unfolds something like this . the anti-hero initially conforms , ignorantly accepting the established views , a typical , unquestioning , brainwashed member of society .
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write a brief synopsis of a story in which an antihero is the protagonist . be sure to use descriptors that illustrate why the protagonist is an antihero .
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prolonged space travel takes a severe toll on the human body . microgravity impairs muscle and bone growth , and high doses of radiation cause irreversible mutations . as we seriously consider the human species becoming space-faring , a big question stands . even if we break free from earth 's orbit and embark on long-duration journeys among the stars , can we adapt to the extreme environments of space ? this wo n't be the first time that humans have adapted to harsh environments and evolved superhuman capabilities . not fantastical powers like laser vision or invisibility , but physiological adaptations for survival in tough conditions . for example , on the himalayan mountains where the highest elevation is nine kilometers above sea level , an unacclimated lowland human will experience symptoms of hypoxia , commonly known as mountain sickness . at these altitudes , the body usually produces extra red blood cells , thickening the blood and impeding its flow . but himalayans who have lived on these mountains for thousands of years permanently evolved mechanisms to circumvent this process and maintain normal blood flow . cases like that prove that humans can develop permanent lifesaving traits . but natural adaptation for entire human populations could take tens of thousands of years . recent scientific advances may help us accelerate human adaptation to single generations . to thrive as a species during space travel , we could potentially develop methods to quickly program protective abilities into ourselves . a beta version of these methods is gene therapy , which we can currently use to correct genetic diseases . gene editing technology , which is improving rapidly , allows scientists to directly change the human genome to stop undesirable processes or make helpful substances . an example of an unwanted process is what happens when our bodies are exposed to ionizing radiation . without an atmospheric barrier and a magnetic field like earth 's , most planets and moons are bombarded with these dangerous subatomic particles . they can pass through nearly anything and would cause potentially cancerous dna damage to space explorers . but what if we could turn the tables on radiation ? human skin produces a pigment called melanin that protects us from the filtered radiation on earth . melanin exists in many forms across species , and some melanin-expressing fungi use the pigment to convert radiation into chemical energy . instead of trying to shield the human body , or rapidly repair damage , we could potentially engineer humans to adopt and express these fungal , melanin-based energy-harvesting systems . they 'd then convert radiation into useful energy while protecting our dna . this sounds pretty sci-fi , but may actually be achievable with current technology . but technology is n't the only obstacle . there are ongoing debates on the consequences and ethics of such radical alterations to our genetic fabric . besides radiation , variation in gravitational strength is another challenge for space travelers . until we develop artificial gravity in a space ship or on another planet , we should assume that astronauts will spend time living in microgravity . on earth , human bone and muscle custodial cells respond to the stress of gravity 's incessant tugging by renewing old cells in processes known as remodeling and regeneration . but in a microgravity environment like mars , human bone and muscle cells wo n't get these cues , resulting in osteoporosis and muscle atrophy . so , how could we provide an artificial signal for cells to counteract bone and muscle loss ? again , this is speculative , but biochemically engineered microbes inside our bodies could churn out bone and muscle remodeling signaling factors . or humans could be genetically engineered to produce more of these signals in the absence of gravity . radiation exposure and microgravity are only two of the many challenges we will encounter in the hostile conditions of space . but if we 're ethically prepared to use them , gene editing and microbial engineering are two flexible tools that could be adapted to many scenarios . in the near future , we may decide to further develop and tune these genetic tools for the harsh realities of space living .
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cases like that prove that humans can develop permanent lifesaving traits . but natural adaptation for entire human populations could take tens of thousands of years . recent scientific advances may help us accelerate human adaptation to single generations .
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which of the following is a super-trait that some human populations have evolved ?
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translator : andrea mcdonough reviewer : bedirhan cinar you look down and see a yellow pencil lying on your desk . your eyes , and then your brain , are collecting all sorts of information about the pencil : its size , color , shape , distance , and more . but , how exactly does this happen ? the ancient greeks were the first to think more or less scientifically about what light is and how vision works . some greek philosophers , including plato and pythagoras , thought that light originated in our eyes and that vision happened when little , invisible probes were sent to gather information about far-away objects . it took over a thousand years before the arab scientist , alhazen , figured out that the old , greek theory of light could n't be right . in alhazen 's picture , your eyes do n't send out invisible , intelligence-gathering probes , they simply collect the light that falls into them . alhazen 's theory accounts for a fact that the greek 's could n't easily explain : why it gets dark sometimes . the idea is that very few objects actually emit their own light . the special , light-emitting objects , like the sun or a lightbulb , are known as sources of light . most of the things we see , like that pencil on your desk , are simply reflecting light from a source rather than producing their own . so , when you look at your pencil , the light that hits your eye actually originated at the sun and has traveled millions of miles across empty space before bouncing off the pencil and into your eye , which is pretty cool when you think about it . but , what exactly is the stuff that is emitted from the sun and how do we see it ? is it a particle , like atoms , or is it a wave , like ripples on the surface of a pond ? scientists in the modern era would spend a couple of hundred years figuring out the answer to this question . isaac newton was one of the earliest . newton believed that light is made up of tiny , atom-like particles , which he called corpuscles . using this assumption , he was able to explain some properties of light . for example , refraction , which is how a beam of light appears to bend as it passes from air into water . but , in science , even geniuses sometimes get things wrong . in the 19th century , long after newton died , scientists did a series of experiments that clearly showed that light ca n't be made up of tiny , atom-like particles . for one thing , two beams of light that cross paths do n't interact with each other at all . if light were made of tiny , solid balls , then you would expect that some of the particles from beam a would crash into some of the particles from beam b . if that happened , the two particles involved in the collision would bounce off in random directions . but , that does n't happen . the beams of light pass right through each other as you can check for yourself with two laser pointers and some chalk dust . for another thing , light makes interference patterns . interference patterns are the complicated undulations that happen when two wave patterns occupy the same space . they can be seen when two objects disturb the surface of a still pond , and also when two point-like sources of light are placed near each other . only waves make interference patterns , particles do n't . and , as a bonus , understanding that light acts like a wave leads naturally to an explanation of what color is and why that pencil looks yellow . so , it 's settled then , light is a wave , right ? not so fast ! in the 20th century , scientists did experiments that appear to show light acting like a particle . for instance , when you shine light on a metal , the light transfers its energy to the atoms in the metal in discrete packets called quanta . but , we ca n't just forget about properties like interference , either . so these quanta of light are n't at all like the tiny , hard spheres newton imagined . this result , that light sometimes behaves like a particle and sometimes behaves like a wave , led to a revolutionary new physics theory called quantum mechanics . so , after all that , let 's go back to the question , `` what is light ? '' well , light is n't really like anything we 're used to dealing with in our everyday lives . sometimes it behaves like a particle and other times it behaves like a wave , but it is n't exactly like either .
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alhazen 's theory accounts for a fact that the greek 's could n't easily explain : why it gets dark sometimes . the idea is that very few objects actually emit their own light . the special , light-emitting objects , like the sun or a lightbulb , are known as sources of light .
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all objects emit their own light .
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after witnessing the violent rage shown by babies whenever deprived of an item they considered their own , jean piaget , a founding father of child psychology , observed something profound about human nature . our sense of ownership emerges incredibly early . why are we so clingy ? there 's a well-established phenomenon in psychology known as the endowment effect where we value items much more highly just as soon as we own them . in one famous demonstration , students were given a choice between a coffee mug or a swiss chocolate bar as a reward for helping out with research . half chose the mug , and half chose the chocolate . that is , they seemed to value the two rewards similarly . other students were given a mug first and then a surprise chance to swap it for a chocolate bar , but only 11 % wanted to . yet another group started out with chocolate , and most preferred to keep it rather than swap . in other words , the students nearly always put greater value on whichever reward they started out with . part of this has to do with how quickly we form connections between our sense of self and the things we consider ours . that can even be seen at the neural level . in one experiment , neuroscientists scanned participants ' brains while they allocated various objects either to a basket labeled `` mine , '' or another labeled , `` alex 's . '' when participants subsequently looked at their new things , their brains showed more activity in a region that usually flickers into life whenever we think about ourselves . another reason we 're so fond of our possessions is that from a young age we believe they have a unique essence . psychologists showed us this by using an illusion to convince three to six-year-olds they built a copying machine , a device that could create perfect replicas of any item . when offered a choice between their favorite toy or an apparently exact copy , the majority of the children favored the original . in fact , they were often horrified at the prospect of taking home a copy . this magical thinking about objects is n't something we grow out of . rather it persists into adulthood while becoming ever more elaborate . for example , consider the huge value placed on items that have been owned by celebrities . it 's as if the buyers believed the objects they 'd purchased were somehow imbued with the essence of their former celebrity owners . for similar reasons , many of us are reluctant to part with family heirlooms which help us feel connected to lost loved ones . these beliefs can even alter our perception of the physical world and change our athletic abilities . participants in a recent study were told they were using a golf putter once owned by the champion ben curtis . during the experiment , they perceived the hole as being about a centimeter larger than controlled participants using a standard putter and they sank slightly more putts . although feelings of ownership emerge early in life , culture also plays a part . for example , it was recently discovered that hadza people of northern tanzania who are isolated from modern culture do n't exhibit the endowment effect . that 's possibly because they live in an egalitarian society where almost everything is shared . at the other extreme , sometimes our attachment to our things can go too far . part of the cause of hoarding disorder is an exaggerated sense of responsibility and protectiveness toward one 's belongings . that 's why people with this condition find it so difficult to throw anything away . what remains to be seen today is how the nature of our relationship with our possessions will change with the rise of digital technologies . many have forecast the demise of physical books and music , but for now , at least , this seems premature . perhaps there will always be something uniquely satisfying about holding an object in our hands and calling it our own .
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although feelings of ownership emerge early in life , culture also plays a part . for example , it was recently discovered that hadza people of northern tanzania who are isolated from modern culture do n't exhibit the endowment effect . that 's possibly because they live in an egalitarian society where almost everything is shared .
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can you describe one way that researchers have demonstrated the endowment effect ?
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an enduring myth says we use only 10 % of our brain , the other 90 % standing idly by for spare capacity . hucksters promised to unlock that hidden potential with methods `` based on neuroscience , '' but all they really unlock is your wallet . two-thirds of the public and nearly half of science teachers mistakenly believe the 10 % myth . in the 1890s , william james , the father of american psychology , said , `` most of us do not meet our mental potential . '' james meant this as a challenge , not an indictment of scant brain usage . but the misunderstanding stuck . also , scientists could n't figure out for a long time the purpose of our massive frontal lobes or broad areas of the parietal lobe . damage did n't cause motor or sensory deficits , so authorities concluded they did n't do anything . for decades , these parts were called silent areas , their function elusive . we 've since learned that they underscore executive and integrative ability , without which , we would hardly be human . they are crucial to abstract reasoning , planning , weighing decisions and flexibly adapting to circumstances . the idea that 9/10 of your brain sits idly by in your skull looks silly when we calculate how the brain uses energy . rodent and canine brains consume 5 % of total body energy . monkey brains use 10 % . an adult human brain , which accounts for only 2 % of the body 's mass , consumes 20 % of daily glucose burned . in children , that figure is 50 % , and in infants , 60 % . this is far more than expected for their relative brain sizes , which scale in proportion to body size . human ones weigh 1.5 kilograms , elephant brains 5 kg , and whale brains 9 kg , yet on a per weight basis , humans pack in more neurons than any other species . this dense packing is what makes us so smart . there is a trade-off between body size and the number of neurons a primate , including us , can sustain . a 25 kg ape has to eat 8 hours a day to uphold a brain with 53 billion neurons . the invention of cooking , one and half million years ago , gave us a huge advantage . cooked food is rendered soft and predigested outside of the body . our guts more easily absorb its energy . cooking frees up time and provides more energy than if we ate food stuffs raw and so we can sustain brains with 86 billion densely packed neurons . 40 % more than the ape . here 's how it works . half the calories a brain burns go towards simply keeping the structure intact by pumping sodium and potassium ions across membranes to maintain an electrical charge . to do this , the brain has to be an energy hog . it consumes an astounding 3.4 x 10^21 atp molecules per minute , atp being the coal of the body 's furnace . the high cost of maintaining resting potentials in all 86 billion neurons means that little energy is left to propel signals down axons and across synapses , the nerve discharges that actually get things done . even if only a tiny percentage of neurons fired in a given region at any one time , the energy burden of generating spikes over the entire brain would be unsustainable . here 's where energy efficiency comes in . letting just a small proportion of cells signal at any one time , known as sparse coding , uses the least energy , but carries the most information . because the small number of signals have thousands of possible paths by which to distribute themselves . a drawback of sparse coding within a huge number of neurons is its cost . worse , if a big proportion of cells never fire , then they are superfluous and evolution should have jettisoned them long ago . the solution is to find the optimum proportion of cells that the brain can have active at once . for maximum efficiency , between 1 % and 16 % of cells should be active at any given moment . this is the energy limit we have to live with in order to be conscious at all . the need to conserve resources is the reason most of the brain 's operations must happen outside of consciousness . it 's why multitasking is a fool 's errand . we simply lack the energy to do two things at once , let alone three or five . when we try , we do each task less well than if we had given it our full attention . the numbers are against us . your brain is already smart and powerful . so powerful that it needs a lot of power to stay powerful . and so smart that it has built in an energy-efficiency plan . so do n't let a fraudulent myth make you guilty about your supposedly lazy brain . guilt would be a waste of energy . after all this , do n't you realize it 's dumb to waste mental energy ? you have billions of power-hungry neurons to maintain . so hop to it !
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rodent and canine brains consume 5 % of total body energy . monkey brains use 10 % . an adult human brain , which accounts for only 2 % of the body 's mass , consumes 20 % of daily glucose burned .
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dolphins , whales , and elephants have much larger brains than we do . they are also documented to have complex societies . elephants even seem to mourn their dead , implying that we are not alone in being able to sense other minds and infer their states . what would it take to understand the mind of another species ?
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translator : andrea mcdonough reviewer : bedirhan cinar i would like to introduce you to my favorite parasite . there are millions that i could choose from and this is it : it 's called the jewel wasp . you can find it in parts of africa and asia . it 's a little under an inch long , and it is a beautiful looking parasite . now , you may be saying to yourself , `` this is not a parasite . it 's not a tapeworm , it 's not a virus , how could a wasp be a parasite ? '' you are probably thinking about regular wasps , you know , the ones that build paper nests as their house . well , the thing is that the jewel wasp makes its house inside a living cockroach . here 's how it happens . a jewel wasp is flying around , looking for a cockroach . when it sees one , it lands and bites on its wing . so , i 'll be the cockroach . be-wha ! bewha ! and the cockroach starts shaking it off , `` get away from me ! '' the wasp very quickly starts stinging the cockroach . all of a sudden , the cockroach ca n't move , for about a minute . and then it recovers and stands up . it could run away now , but it does n't . it just does n't want to . it just stays there . it 's become a zombie slave . again , i 'm not making this up . the wasp goes off , it walks away and finds a hole and digs it out , makes it into a burrow . it walks back . this can take up to half an hour . the cockroach is still there . what do we do now ? the wasps grabs onto one of the antenna , bites down on it , of the cockroach , and pulls the cockroach . and the cockroach says , `` alright , '' and walks like a dog on a leash . the wasp takes it all the way down into the burrow . the cockroach says , `` nice place . '' the wasp takes care of some business and then goes and leaves the burrow and seals it shut , leaving the cockroach entombed in darkness , still alive . the cockroach says , `` alright , i 'll stay here if you want . '' now , i mentioned that the cockroach took care , ah , the wasp took care of a little business before it left the burrow . the business was laying an egg on the underside of the cockroach . the egg hatches . out comes a wasp larva . it looks kind of like a maggot with big , nasty jaws . it chews a hole into the cockroach and starts to feed from the outside . it gets bigger , like you can see over here . and then when it gets big enough , it decides to crawl into the hole , into the cockroach . so now it 's inside the still-living cockroach and the cockroach does n't mind much . this goes on for about a month . the larva grows and grows and grows , then makes a pupa , kind of like a cocoon . inside there it grows eyes , it grows wings , it grows legs , the cockroach is still alive , still waiting . finally the wasp is ready to leave , and that 's when the cockroach finally dies because the fullly-formed adult wasp crawls out of the cockroach 's dying body . the wasp shakes itself off , climbs out of the burrow , goes and finds another wasp to mate with to start this whole , crazy cycle again . so , this is not science fiction , this happens every day , all over the world . and scientists are totally fascinated by this . they 're just starting to figure out how all this happens . and , when you really start to look at the science of it , you start to kind of respect this very creepy wasp . you see , the thing is that when it attacks the cockroach , it 's not just stinging wildly , it delivers two precise stings . it knows this cockroach 's nervous system like you know the back of your hand . the first sting goes to that spot there , called the `` walking rhythm generators , '' and , as you can guess , those are the neurons that send signals to the legs to move . it blocks the channels that the neurons use to send these signals . so the cockroach wants to go , it wants to run away , but it ca n't because it ca n't move its legs . and that lasted for about a minute . this is really sophisticated pharmacology . we actually use the same method , a drug called ivermectin , to cure river blindness , which is caused by a parasitic worm that gets into your eye . if you take ivermectin , you paralyze the worm using the same strategy . now , we discovered this in the 1970s , the wasp has been doing this for millions of years . then comes the second sting . now the second sting actually hits two places along the way . and to try to imagine how this can happen , i want you to picture yourself with a friend who 's got a very long , very , very scary looking needle . and your friend , or at least you thought he was your friend , sticks it in your neck , goes into your skull , stops off at one part of your brain and injects some drugs , then keeps going in your brain and injects some more . these are two particular spots , marked here , `` seg '' , and you can see the tip of it in the brain , marked `` br '' . now , we can do this , but it 's really hard for us . it 's called stereotactic drug delivery . you have to put a patient in a big metal frame to hold them still , you need cat scans to know where you 're going , so you look at the picture and say , `` are we going the right way ? '' the jewel wasp has sensors on its stinger and scientists think that it can actually feel its way through the cockroach 's brain until it gets to the exact , right place , and then penetrates an individual neuron and then delivers the goods . so , this is quite amazing stuff , and what seems to happen then is that the wasp is taking away the control that the cockroach has over its own body . it 's taking away the cockroach 's free will . we did n't really appreciate that cockroaches have free will until this wasp showed us . and , we have no idea how it 's doing this , we do n't know yet what the venom has in it and we do n't know which circuits it 's hitting in the cockroach 's brain , and i think that 's why this is , most of all , my favorite parasite because we have so much left to learn from it . thank you very much .
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there are millions that i could choose from and this is it : it 's called the jewel wasp . you can find it in parts of africa and asia . it 's a little under an inch long , and it is a beautiful looking parasite .
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do some research . find another parasite and briefly explain how it functions .
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death and taxes are famously inevitable , but what about decomposition ? as anyone who 's seen a mummy knows , ancient egyptians went to a lot of trouble to evade decomposition . so , how successful were they ? living cells constantly renew themselves . specialized enzymes decompose old structures , and the raw materials are used to build new ones . but what happens when someone dies ? their dead cells are no longer able to renew themselves , but the enzymes keep breaking everything down . so anyone looking to preserve a body needed to get ahead of those enzymes before the tissues began to rot . neurons die quickly , so brains were a lost cause to ancient egyptian mummifiers , which is why , according to greek historian herodotus , they started the process by hammering a spike into the skull , mashing up the brain , flushing it out the nose and pouring tree resins into the skull to prevent further decomposition . brains may decay first , but decaying guts are much worse . the liver , stomach and intestines contain digestive enzymes and bacteria , which , upon death , start eating the corpse from the inside . so the priests removed the lungs and abdominal organs first . it was difficult to remove the lungs without damaging the heart , but because the heart was believed to be the seat of the soul , they treated it with special care . they placed the visceral organs in jars filled with a naturally occurring salt called natron . like any salt , natron can prevent decay by killing bacteria and preventing the body 's natural digestive enzymes from working . but natron is n't just any salt . it 's mainly a mixture of two alkaline salts , soda ash and baking soda . alkaline salts are especially deadly to bacteria . and they can turn fatty membranes into a hard , soapy substance , thereby maintaining the corpse 's structure . after dealing with the internal organs , the priest stuffed the body cavity with sacks of more natron and washed it clean to disinfect the skin . then , the corpse was set in a bed of still more natron for about 35 days to preserve its outer flesh . by the time of its removal , the alkaline salts had sucked the fluid from the body and formed hard brown clumps . the corpse was n't putrid , but it did n't exactly smell good , either . so , priests poured tree resin over the body to seal it , massaged it with a waxy mixture that included cedar oil , and then wrapped it in linen . finally , they placed the mummy in a series of nested coffins and sometimes even a stone sarcophagus . so how successful were the ancient egyptians at evading decay ? on one hand , mummies are definitely not intact human bodies . their brains have been mashed up and flushed out , their organs have been removed and salted like salami , and about half of their remaining body mass has been drained away . still , what remains is amazingly well-preserved . even after thousands of years , scientists can perform autopsies on mummies to determine their causes of death , and possibly even isolate dna samples . this has given us new information . for example , it seems that air pollution was a serious problem in ancient egypt , probably because of indoor fires used to bake bread . cardiovascular disease was also common , as was tuberculosis . so ancient egyptians were somewhat successful at evading decay . still , like death , taxes are inevitable . when some mummies were transported , they were taxed as salted fish .
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cardiovascular disease was also common , as was tuberculosis . so ancient egyptians were somewhat successful at evading decay . still , like death , taxes are inevitable .
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ancient egyptian mummies do not show high rates of :
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so now you can see the reactionís really going and itís really exothermic , weíre forming aluminium triiodide , and the exotherm is actually heating and starting to sublime off the excess iodine which you can see coming off as this really nice purple plume . iodine is this beautifully-coloured element . it has this beautiful purple colour . if you put it in solution , the colour of the solution varies depending what you dissolve it in . if you dissolve it in water , itís a sort-of dirty brown colour . if you dissolve it in an organic material like chloroform or carbon tetrachloride it is a beautiful purple colour . iodine is halide , a halogen element from the far right-hand side of the periodic table and it 's strongly oxidising in nature . likes to nick electrons off other atoms , so what weíre going to do is we are going to do a reaction with iodine , and today weíve ground some iodine . so itís normally found from chemical suppliers as really nice large crystals . but what we want to do as a reaction with it , well we need to make sure that the surface area of the iodine is really , really large so that all of it can react very very quickly with the other component . iodine also occurs quite widely in nature and is absolutely essential to life . if you donít have iodine , your thyroid gland , which is a small gland that controls development of all sorts of things in your body , doesnít operate properly . nowadays , iodide is added to table salt in countries like the uk and most other developed countries so nearly everybody has enough iodine . in the old days iodine had to be got from the environment and usually from the spray from the sea that was blown across the land , and so in nottingham , which is really near the centre of england a long way from the sea , or relatively long way from the sea , there were serious illnesses caused by people not having enough iodine . so-called goiter , which caused a swelling , the thyroid gland gets bigger , and this used to be called derbyshire neck this unpleasant illness , because it happened in this area of nottingham and derbyshire . so what weíre going to do is that we are going to mix it now with another element and that element is aluminium . so aluminium has electrons to give away . iodineís gon na nab ëem . going to see some oxidation chemistry in the formation of a new compound , which is aluminium triiodide . itís a really nice chemical reaction . but the way that we do it is that we mix the two together and we have to add water which acts a bit like solvent and also the oxygen in the water activates the iodine so that it becomes more strongly oxidising and then hopefully weíll see the new reaction . so iím going to just put some out into this small vessel . you can see this development effect of iodine really well that if you had tadpoles , baby frogs , they donít develop their legs and turn into frogs unless there is iodine in the water . the other component in this reaction is aluminium , ok ; and weíre using very , very finely powdered aluminium . not foil or not a rather large lump . this has been especially powdered for us , so again it has a very , very high surface area . one of my favourite chemical equations is ëtadpoles plus iodine goes to frogsí . so you can see the aluminium and the iodine mixed within this solid mixture . now still , these two components , these two elements they are still held away from one another they canít react . so what we need to do is add a small amount of water , which actually acts like a solvent but actually activates the iodine and then weíll wait and see what happens with the chemical reaction . iodine can be used as a disinfectant , in fact chlorine can be as well , but solution of iodine is often used when people have cuts . so if you cut yourself , fortunately i havenít any cuts at the moment , you can paint on iodine and because of its rather red colour it made cuts often look much worse . children would come home from school and their whole hand would be red and this would cause some excitement at home but it is quite an effective antiseptic . water : just take a small amount and add it to the reaction . so you can see itís starting to go now the chemical reaction because we are seeing the excess iodine subliming in the form of a vapour . now if we go in close we can hear it fizzing because this is actually an oxidation reaction and the formation of the new aluminium triiodide . now iím going to just mix this slightly to try and increase the rate of the chemical reaction slightly . so now you can see the reactionís really going and itís really exothermic , weíre forming aluminium triiodide , and the exotherm is actually heating and starting to sublime off the excess iodine which you can see coming off as this really nice purple plume . now deep inside the reaction now you can see the exothermic or the energy coming out and starting to cause a flame . really , really nice , really rapid chemical reaction : really beautiful . so weíre forming aluminium triiodide here which again is a very , very delicate compound ; quite reactive in itself . so you can see now the really nice new crystalline material . so , sadly , weíve managed to stain stigís fume cupboard . all of this really nice iodine forming a very fine layer across this fume cupboard . what do you think about that ? looks like a thorough cleaning job coming to be honest .
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so what we need to do is add a small amount of water , which actually acts like a solvent but actually activates the iodine and then weíll wait and see what happens with the chemical reaction . iodine can be used as a disinfectant , in fact chlorine can be as well , but solution of iodine is often used when people have cuts . so if you cut yourself , fortunately i havenít any cuts at the moment , you can paint on iodine and because of its rather red colour it made cuts often look much worse .
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what chemical property allows iodine to be used as an antiseptic ?
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i was a blue-eyed , chubby-cheeked five-year-old when i joined my family on the picket line for the first time . my mom made me leave my dolls in the minivan . i 'd stand on a street corner in the heavy kansas humidity , surrounded by a few dozen relatives , with my tiny fists clutching a sign that i could n't read yet : `` gays are worthy of death . '' this was the beginning . our protests soon became a daily occurrence and an international phenomenon , and as a member of westboro baptist church , i became a fixture on picket lines across the country . the end of my antigay picketing career and life as i knew it , came 20 years later , triggered in part by strangers on twitter who showed me the power of engaging the other . in my home , life was framed as an epic spiritual battle between good and evil . the good was my church and its members , and the evil was everyone else . my church 's antics were such that we were constantly at odds with the world , and that reinforced our otherness on a daily basis . `` make a difference between the unclean and the clean , '' the verse says , and so we did . from baseball games to military funerals , we trekked across the country with neon protest signs in hand to tell others exactly how `` unclean '' they were and exactly why they were headed for damnation . this was the focus of our whole lives . this was the only way for me to do good in a world that sits in satan 's lap . and like the rest of my 10 siblings , i believed what i was taught with all my heart , and i pursued westboro 's agenda with a special sort of zeal . in 2009 , that zeal brought me to twitter . initially , the people i encountered on the platform were just as hostile as i expected . they were the digital version of the screaming hordes i 'd been seeing at protests since i was a kid . but in the midst of that digital brawl , a strange pattern developed . someone would arrive at my profile with the usual rage and scorn , i would respond with a custom mix of bible verses , pop culture references and smiley faces . they would be understandably confused and caught off guard , but then a conversation would ensue . and it was civil -- full of genuine curiosity on both sides . how had the other come to such outrageous conclusions about the world ? sometimes the conversation even bled into real life . people i 'd sparred with on twitter would come out to the picket line to see me when i protested in their city . a man named david was one such person . he ran a blog called `` jewlicious , '' and after several months of heated but friendly arguments online , he came out to see me at a picket in new orleans . he brought me a middle eastern dessert from jerusalem , where he lives , and i brought him kosher chocolate and held a `` god hates jews '' sign . ( laughter ) there was no confusion about our positions , but the line between friend and foe was becoming blurred . we 'd started to see each other as human beings , and it changed the way we spoke to one another . it took time , but eventually these conversations planted seeds of doubt in me . my friends on twitter took the time to understand westboro 's doctrines , and in doing so , they were able to find inconsistencies i 'd missed my entire life . why did we advocate the death penalty for gays when jesus said , `` let he who is without sin cast the first stone ? '' how could we claim to love our neighbor while at the same time praying for god to destroy them ? the truth is that the care shown to me by these strangers on the internet was itself a contradiction . it was growing evidence that people on the other side were not the demons i 'd been led to believe . these realizations were life-altering . once i saw that we were not the ultimate arbiters of divine truth but flawed human beings , i could n't pretend otherwise . i could n't justify our actions -- especially our cruel practice of protesting funerals and celebrating human tragedy . these shifts in my perspective contributed to a larger erosion of trust in my church , and eventually it made it impossible for me to stay . in spite of overwhelming grief and terror , i left westboro in 2012 . in those days just after i left , the instinct to hide was almost paralyzing . i wanted to hide from the judgement of my family , who i knew would never speak to me again -- people whose thoughts and opinions had meant everything to me . and i wanted to hide from the world i 'd rejected for so long -- people who had no reason at all to give me a second chance after a lifetime of antagonism . and yet , unbelievably , they did . the world had access to my past because it was all over the internet -- thousands of tweets and hundreds of interviews , everything from local tv news to `` the howard stern show '' -- but so many embraced me with open arms anyway . i wrote an apology for the harm i 'd caused , but i also knew that an apology could never undo any of it . all i could do was try to build a new life and find a way somehow to repair some of the damage . people had every reason to doubt my sincerity , but most of them did n't . and -- given my history , it was more than i could 've hoped for -- forgiveness and the benefit of the doubt . it still amazes me . i spent my first year away from home adrift with my younger sister , who had chosen to leave with me . we walked into an abyss , but we were shocked to find the light and a way forward in the same communities we 'd targeted for so long . david , my `` jewlicious '' friend from twitter , invited us to spend time among a jewish community in los angeles . we slept on couches in the home of a hasidic rabbi and his wife and their four kids -- the same rabbi that i 'd protested three years earlier with a sign that said , `` your rabbi is a whore . '' we spent long hours talking about theology and judaism and life while we washed dishes in their kosher kitchen and chopped vegetables for dinner . they treated us like family . they held nothing against us , and again i was astonished . that period was full of turmoil , but one part i 've returned to often is a surprising realization i had during that time -- that it was a relief and a privilege to let go of the harsh judgments that instinctively ran through my mind about nearly every person i saw . i realized that now i needed to learn . i needed to listen . this has been at the front of my mind lately , because i ca n't help but see in our public discourse so many of the same destructive impulses that ruled my former church . we celebrate tolerance and diversity more than at any other time in memory , and still we grow more and more divided . we want good things -- justice , equality , freedom , dignity , prosperity -- but the path we 've chosen looks so much like the one i walked away from four years ago . we 've broken the world into us and them , only emerging from our bunkers long enough to lob rhetorical grenades at the other camp . we write off half the country as out-of-touch liberal elites or racist misogynist bullies . no nuance , no complexity , no humanity . even when someone does call for empathy and understanding for the other side , the conversation nearly always devolves into a debate about who deserves more empathy . and just as i learned to do , we routinely refuse to acknowledge the flaws in our positions or the merits in our opponent 's . compromise is anathema . we even target people on our own side when they dare to question the party line . this path has brought us cruel , sniping , deepening polarization , and even outbreaks of violence . i remember this path . it will not take us where we want to go . what gives me hope is that we can do something about this . the good news is that it 's simple , and the bad news is that it 's hard . we have to talk and listen to people we disagree with . it 's hard because we often ca n't fathom how the other side came to their positions . it 's hard because righteous indignation , that sense of certainty that ours is the right side , is so seductive . it 's hard because it means extending empathy and compassion to people who show us hostility and contempt . the impulse to respond in kind is so tempting , but that is n't who we want to be . we can resist . and i will always be inspired to do so by those people i encountered on twitter , apparent enemies who became my beloved friends . and in the case of one particularly understanding and generous guy , my husband . there was nothing special about the way i responded to him . what was special was their approach . i thought about it a lot over the past few years and i found four things they did differently that made real conversation possible . these four steps were small but powerful , and i do everything i can to employ them in difficult conversations today . the first is do n't assume bad intent . my friends on twitter realized that even when my words were aggressive and offensive , i sincerely believed i was doing the right thing . assuming ill motives almost instantly cuts us off from truly understanding why someone does and believes as they do . we forget that they 're a human being with a lifetime of experience that shaped their mind , and we get stuck on that first wave of anger , and the conversation has a very hard time ever moving beyond it . but when we assume good or neutral intent , we give our minds a much stronger framework for dialogue . the second is ask questions . when we engage people across ideological divides , asking questions helps us map the disconnect between our differing points of view . that 's important because we ca n't present effective arguments if we do n't understand where the other side is actually coming from and because it gives them an opportunity to point out flaws in our positions . but asking questions serves another purpose ; it signals to someone that they 're being heard . when my friends on twitter stopped accusing and started asking questions , i almost automatically mirrored them . their questions gave me room to speak , but they also gave me permission to ask them questions and to truly hear their responses . it fundamentally changed the dynamic of our conversation . the third is stay calm . this takes practice and patience , but it 's powerful . at westboro , i learned not to care how my manner of speaking affected others . i thought my rightness justified my rudeness -- harsh tones , raised voices , insults , interruptions -- but that strategy is ultimately counterproductive . dialing up the volume and the snark is natural in stressful situations , but it tends to bring the conversation to an unsatisfactory , explosive end . when my husband was still just an anonymous twitter acquaintance , our discussions frequently became hard and pointed , but we always refused to escalate . instead , he would change the subject . he would tell a joke or recommend a book or gently excuse himself from the conversation . we knew the discussion was n't over , just paused for a time to bring us back to an even keel . people often lament that digital communication makes us less civil , but this is one advantage that online conversations have over in-person ones . we have a buffer of time and space between us and the people whose ideas we find so frustrating . we can use that buffer . instead of lashing out , we can pause , breathe , change the subject or walk away , and then come back to it when we 're ready . and finally ... make the argument . this might seem obvious , but one side effect of having strong beliefs is that we sometimes assume that the value of our position is or should be obvious and self-evident , that we should n't have to defend our positions because they 're so clearly right and good that if someone does n't get it , it 's their problem -- that it 's not my job to educate them . but if it were that simple , we would all see things the same way . as kind as my friends on twitter were , if they had n't actually made their arguments , it would 've been so much harder for me to see the world in a different way . we are all a product of our upbringing , and our beliefs reflect our experiences . we ca n't expect others to spontaneously change their own minds . if we want change , we have to make the case for it . my friends on twitter did n't abandon their beliefs or their principles -- only their scorn . they channeled their infinitely justifiable offense and came to me with pointed questions tempered with kindness and humor . they approached me as a human being , and that was more transformative than two full decades of outrage , disdain and violence . i know that some might not have the time or the energy or the patience for extensive engagement , but as difficult as it can be , reaching out to someone we disagree with is an option that is available to all of us . and i sincerely believe that we can do hard things , not just for them but for us and our future . escalating disgust and intractable conflict are not what we want for ourselves , or our country or our next generation . my mom said something to me a few weeks before i left westboro , when i was desperately hoping there was a way i could stay with my family . people i have loved with every pulse of my heart since even before i was that chubby-cheeked five-year-old , standing on a picket line holding a sign i could n't read . she said , `` you 're just a human being , my dear , sweet child . '' she was asking me to be humble -- not to question but to trust god and my elders . but to me , she was missing the bigger picture -- that we 're all just human beings . that we should be guided by that most basic fact , and approach one another with generosity and compassion . each one of us contributes to the communities and the cultures and the societies that we make up . the end of this spiral of rage and blame begins with one person who refuses to indulge these destructive , seductive impulses . we just have to decide that it 's going to start with us . thank you . ( applause )
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i needed to listen . this has been at the front of my mind lately , because i ca n't help but see in our public discourse so many of the same destructive impulses that ruled my former church . we celebrate tolerance and diversity more than at any other time in memory , and still we grow more and more divided .
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how does megan believe that her experience mirrors the current public discourse ?
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looking up at the night sky , we are amazed by how it seems to go on forever . but what will the sky look like billions of years from now ? a particular type of scientist , called a cosmologist , spends her time thinking about that very question . the end of the universe is intimately linked to what the universe contains . over 100 years ago , einstein developed the theory of general relativity , formed of equations that help us understand the relationship between what a universe is made of and its shape . it turns out that the universe could be curved like a ball or sphere . we call this positively curved or closed . or it could be shaped like a saddle . we call this negatively curved or open . or it could be flat . and that shape determines how the universe will live and die . we now know that the universe is very close to flat . however , the components of the universe can still affect its eventual fate . we can predict how the universe will change with time if we measure the amounts or energy densities of the various components in the universe today . so , what is the universe made of ? the universe contains all the things that we can see , like stars , gas , and planets . we call these things ordinary or baryonic matter . even though we see them all around us , the total energy density of these components is actually very small , around 5 % of the total energy of the universe . so , now let 's talk about what the other 95 % is . just under 27 % of the rest of the energy density of the universe is made up of what we call dark matter . dark matter is only very weakly interacting with light , which means it does n't shine or reflect light in the way that stars and planets do , but , in every other way , it behaves like ordinary matter -- it attracts things gravitationally . in fact , the only way we can detect this dark matter is through this gravitational interaction , how things orbit around it and how it bends light as it curves the space around it . we have yet to discover a dark matter particle , but scientists all over the world are searching for this elusive particle or particles and the effects of dark matter on the universe . but this still does n't add up to 100 % . the remaining 68 % of the energy density of the universe is made up of dark energy , which is even more mysterious than dark matter . this dark energy does n't behave like any other substance we know at all and acts more like anti-gravity force . we say that it has a gravitational pressure , which ordinary matter and dark matter do not . instead of pulling the universe together , as we would expect gravity to do , the universe appears to be expanding apart at an ever-increasing rate . the leading idea for dark energy is that it is a cosmological constant . that means it has the strange property that it expands as the volume of space increases to keep its energy density constant . so , as the universe expands as it is doing right now , there will be more and more dark energy . dark matter and baryonic matter , on the other hand , do n't expand with the universe and become more diluted . because of this property of the cosmological constant , the future universe will be more and more dominated by dark energy , becoming colder and colder and expanding faster and faster . eventually , the universe will run out of gas to form stars , and the stars themselves will run out of fuel and burn out , leaving the universe with only black holes in it . given enough time , even these black holes will evaporate , leaving a universe that is completely cold and empty . that is what we call the heat death of the universe . while it might sound depressing living in a universe that will end its lifetime cold and devoid of life , the end fate of our universe actually has a beautiful symmetry to its hot , fiery beginning . we call the accelerating end state of the universe a de sitter phase , named after the dutch mathematician willem de sitter . however , we also believe that the universe had another phase of de sitter expansion in the earliest times of its life . we call this early period inflation , where , shortly after the big bang , the universe expanded extremely fast for a brief period . so , the universe will end in much the same state as it began , accelerating . we live at an extraordinary time in the life of the universe where we can start to understand the universe 's journey and view a history that plays itself out on the sky for all of us to see .
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or it could be flat . and that shape determines how the universe will live and die . we now know that the universe is very close to flat .
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the geometry of the universe has an effect on how the shape of objects appear . if we knew there was a spot of a certain physical size , and it appeared larger , what would that tell us about the geometry of space ?
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what do silk , dna , wood , balloons , and silly putty all have in common ? they 're polymers . polymers are such a big part of our lives that it 's virtually impossible to imagine a world without them , but what the heck are they ? polymers are large molecules made of small units called monomers linked together like the railroad cars from a train . poly means many , and mono means one , and mers or mero means parts . many polymers are made by repeating the same small monomer over and over again while others are made from two monomers linked in a pattern . all living things are made of polymers . some of the organic molecules in organisms are small and simple , having only one of a few functional groups . others , especially those that play structural roles or store genetic information , are macromolecules . in many cases , these macromolecules are polymers . for example , complex carbohydrates are polymers of simple sugars , proteins are polymers of amino acids , and nucleic acids , dna and rna , which contain our genetic information , are polymers of nucleotides . trees and plants are made of the polymer cellulose . it 's the tough stuff you find in bark and stems . feathers , fur , hair , and fingernails are made up of the protein keratin , also a polymer . it does n't stop there . did you know that the exoskeletons of the largest phylum in the animal kingdom , the arthropods , are made of the polymer chitin ? polymers also form the basis for synthetic fibers , rubbers , and plastics . all synthetic polymers are derived from petroleum oil and manufactured through chemical reactions . the two most common types of reactions used to make polymers are addition reactions and condensation reactions . in addition reactions , monomers simply add together to form the polymer . the process starts with a free radical , a species with an unpaired electron . the free radical attacks and breaks the bonds to form new bonds . this process repeats over and over to create a long-chained polymer . in condensation reactions , a small molecule , such as water , is produced with each chain-extending reaction . the first synthetic polymers were created by accident as by-products of various chemical reactions . thinking they were useless , chemists mostly discarded them . finally , one named leo baekeland decided maybe his useless by-product was n't so useless after all . his work resulted in a plastic that could be permanently squished into a shape using pressure and high temperatures . since the name of this plastic , polyoxybenzylmethylenglycolanhydride , was n't very catchy , advertisers called it bakelite . bakelite was made into telephones , children 's toys , and insulators for electrical devices . with its development in 1907 , the plastics industry exploded . one other familiar polymer , silly putty , was also invented by accident . during world war ii , the united states was in desperate need of synthetic rubber to support the military . a team of chemists at general electric attempted to create one but ended up with a gooey , soft putty . it was n't a good rubber substitute , but it did have one strange quality : it appeared to be extremely bouncy . silly putty was born ! synthetic polymers have changed the world . think about it . could you imagine getting through a single day without using plastic ? but polymers are n't all good . styrofoam , for example , is made mainly of styrene , which has been identified as a possible carcinogen by the environmental protection agency . as styrofoam products are being made , or as they slowly deteriorate in landfills or the ocean , they can release toxic styrene into the environment . in addition , plastics that are created by addition polymerization reactions , like styrofoam , plastic bags , and pvc , are built to be durable and food-safe , but that means that they do n't break down in the environment . millions of tons of plastics are dumped into landfills every year . this plastic does n't biodegrade , it just breaks down into smaller and smaller pieces , affecting marine life and eventually making their way back to humans . polymers can be soft or hard , squishy or solid , fragile or strong . the huge variation between means they can form an incredibly diverse array of substances , from dna to nylon stockings . polymers are so useful that we 've grown to depend on them every day . but some are littering our oceans , cities , and waterways with effects on our health that we 're only beginning to understand .
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silly putty was born ! synthetic polymers have changed the world . think about it .
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clearly , synthetic polymers make our life easier , but their use has caused environmental problems . what ways can we reduce pollution problems caused by the overuse of synthetic polymers ?
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vsauce , i ’ m jake and thank you for visiting because i have been stuck in this chair for weeks . why you ask ? let me tell you ! it is because of this ! what is that ? well my dear friend , as you may know i have cancer and to try and stop it from spreading , they removed a lot of flesh , muscle , tissue and bone and replaced it with something else…and that got me thinking , about what makes you you . which then in turn got me thinking about paradoxes . specifically logical paradoxes or thought experiments . ya know there is one in particular that pertains to the removal and replacement of certain things…let 's go outside quick little side note : i also figured out teleportation but we ’ ll discuss that later…ya know you should come out here too . so we can discuss the ship of theseus ! the ship of theseus is pretty straightforward as far as logical paradoxes go . let 's say we have a ship , and it 's a very nice ship . but after a while we end up replacing all the wood and then a while later we replace the sails , then a while later we replace the hooks . is it still the same ship ? or is it a new ship ? a different ship ? let ’ s go a step further . let ’ s say we kept all the pieces of this ship that we replaced and used them to make another ship ... an identical one . is this one the original or is this one ? or are they both not original ? what makes something truly original ? i need some sand . here i have what i would consider a heap of sand which leads us into our next logical paradox . the sorites paradox . sorites in ancient greek meaning heap . so , we have our heap , right ? but what happens if we take away a grain of sand ? well , it 's still a heap . but then we take away another grain… still a heap . but then we take another , and another , until we get this . is this a heap ? what about this ? or this ? if we remove a grain until only one is left…is this still a heap ? at what point do we no longer consider it a heap ? let ’ s reverse it . we start with a single grain of sand . obviously not what we would call a heap . but then we add a grain and another , and another . when does it become a heap of sand ? ya know , instead of using objects as our examples , let ’ s discuss a paradox that instead , uses words . we interact with words every day but today we are going to focus on just two words , autological and heterological , these are essential for the grelling-nelson paradox . an autological word is a word that describes itself . for example : pronounceable is pronounceable , polysyllabic is polysyllabic , and a noun is a noun . then there is heterological where a word does not describe itself . for example : purple is not purple , triangle is not a triangle and hyphenated is not hyphenated . the paradox comes into play when we ask the question : is the word “ heterological ” heterological ? if you say no , then heteorological does not describe itself . and if it ’ s not heterological then it must be autological and describe itself . but if it is autological then heterological describes itself and therefor heterological is heterological . paradox . if you say yes , heterological does not describe itself then that means heterological is not heterological . paradox . let ’ s try something . let ’ s combine aspects of the ship of theseus and the sorites paradox and apply it to ourselves . even though part of my leg was replaced i am still me , right ? if my entire leg were removed , i ’ d still be me . so at what point am i no longer myself ? how much would have to be removed for you to no longer be you ? or is what makes us us our memories of who we are and of who we were ? for example , you are different than when you were a baby . obviously you are taller , a little bit heavier , you have different hair , different teeth , and all of your cells have been replaced since birth . i mean your personality has changed . your opinions have changed…so how are you the same person ? ya know ... maybe we should lay off the teleportation for a little not just because of that but also because i 've been thinking of something ... the teletransportation paradox . let ’ s say we have a machine that can teleport you from here to there . in order to transmit you though , the machine kills you and instantly breaks you down into all the atoms that once made you up . it then transmits all the data of what you were to another machine in a different location which remakes you . putting different atoms in the right spot . so the question is , is the person who went into the machine the same person coming out of the other machine ? you have the same memories , the same thoughts , but everything that physically makes you is different . you ’ d remember everything up to being teleported and reemerging on the other side - everything in between would be lost . so , is it your identity , your emotions , feelings and is it your thoughts that make you you ? ya know , you should come a little bit closer . when you wake up in the morning , how do you know that you ’ re the same person as who went to sleep ? how do i know that when i close my eyes , is the same jake opening them ? maybe every time we open our eyes we are being created again and again from the idea of who we are…from our sense of identity . and , as always , thanks for watching .
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i need some sand . here i have what i would consider a heap of sand which leads us into our next logical paradox . the sorites paradox .
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the logical paradox that imagines us holding a heap of sand and removing one grain at a time in an attempt to answer the question `` when does a heap stop being a heap '' is called ...
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imagine two people are listening to music . what are the odds that they are listening to the exact same playlist ? probably pretty low . after all , everyone has very different tastes in music . now , what are the odds that your body will need the exact same medical care and treatment as another person 's body ? even lower . as we go through our lives , each of us will have very different needs for our own healthcare . scientists and doctors are constantly researching ways to make medicine more personalized . one way they are doing this is by researching stem cells . stem cells are cells that are undifferentiated , meaning they do not have a specific job or function . while skin cells protect your body , muscle cells contract , and nerve cells send signals , stem cells do not have any specific structures or functions . stem cells do have the potential to become all other kinds of cells in your body . your body uses stem cells to replace worn-out cells when they die . for example , you completely replace the lining of your intestines every four days . stem cells beneath the lining of your intestines replace these cells as they wear out . scientists hope that stem cells could be used to create a very special kind of personalized medicine in which we could replace your own body parts with , well , your own body parts . stem cell researchers are working hard to find ways in which to use stem cells to create new tissue to replace the parts of organs that are damaged by injury or disease . using stem cells to replace damaged bodily tissue is called regenerative medicine . for example , scientists currently use stem cells to treat patients with blood diseases such as leukemia . leukemia is a form of cancer that affects your bone marrow . bone marrow is the spongy tissue inside your bones where your blood cells are created . in leukemia , some of the cells inside your bone marrow grow uncontrollably , crowding out the healthy stem cells that form your blood cells . some leukemia patients can receive a stem cell transplant . these new stem cells will create the blood cells needed by the patient 's body . there are actually multiple kinds of stem cells that scientists can use for medical treatments and research . adult stem cells or tissue-specific stem cells are found in small numbers in most of your body 's tissues . tissue-specific stem cells replace the existing cells in your organs as they wear out and die . embryonic stem cells are created from leftover embryos that are willingly donated by patients from fertility clinics . unlike tissue-specific stem cells , embryonic stem cells are pluripotent . this means that they can be grown into any kind of tissue in the body . a third kind of stem cells is called induced pluripotent stem cells . these are regular skin , fat , liver , or other cells that scientists have changed to behave like embryonic stem cells . like embryonic stem cells , they , too , can become any kind of cell in the body . while scientists and doctors hope to use all of these kinds of stem cells to create new tissue to heal your body , they can also use stem cells to help understand how the body works . scientists can watch stem cells develop into tissue to understand the mechnanisms that the body uses to create new tissue in a controlled and regulated way . scientists hope that with more research , they can not only develop specialized medicine that is specific to your body but also better understand how your body functions , both when it 's healthy and when it 's not .
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in leukemia , some of the cells inside your bone marrow grow uncontrollably , crowding out the healthy stem cells that form your blood cells . some leukemia patients can receive a stem cell transplant . these new stem cells will create the blood cells needed by the patient 's body .
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a stem cell is…
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translator : andrea mcdonough reviewer : jessica ruby olive oil is 100 % fat ; there 's nothing else in it . pancake mix , on the other hand , is only about 11 % fat . and , yet , olive oil is good for you , and pancake mix is not . why is that ? as it turns out , the amount of fat we eat does n't impact our weight or our cholesterol or our risk of heart disease nearly as much as what kind of fat we eat . but let 's back up : what is fat ? if we were to zoom in on a salmon , which is a fatty fish , past the organs , past the tissues , into the cells , we would see that the stuff we call fat is actually made up of molecules called triglycerides , and they are not all alike . here 's one example . those three carbons on the left , that 's glycerol . now , you can think of that as the backbone that holds the rest of the molecule together . the three long chains on the right are called fatty acids , and it 's subtle differences in the structures of these chains that determine whether a fat is , let 's say , solid or liquid ; whether or not it goes rancid quickly ; and , most importantly , how good or how bad it is for you . let 's take a look at some of these differences . one is length . fatty acids can be short or long . another , more important difference is the type of bond between the carbon atoms . some fatty acids have only single bonds . others have both single and double bonds . fatty acids with only single bonds are called saturated , and those with one or more double bonds are called unsaturated . now , most unsaturated fats are good for you , while saturated fats are bad for you in excess . for saturated fats , the story pretty much ends there but not for unsaturated fats . the double bonds in these molecules have a kind of weird property ; they 're rigid . so , that means there are two ways to arrange every double bond . the first is like this , where both hydrogens are on same side and both carbons are on the same side . the second way is like this . now the hydrogens and carbons are on opposite sides of the double bond . now , even though both of these molecules are made up of exactly the same building blocks , they are two completely different substances , and they behave completely differently inside of us . the configuration on the left is called cis , which you 've probably never heard of . the one of the right is called trans , and you probably have heard of trans fats before . they do n't go rancid , they 're more stable during deep frying , and they can change the texture of foods in ways that other fats just ca n't . they 're also terrible for your health , by far worse than saturated fat , even though technically they 're a type of unsaturated fat . now , i know that seems crazy , but your body does n't care what a molecule looks like on paper . all that matters is the 3-d shape where the molecule fits , where it does n't , and what pathways it interferes with . so , how do you know if a food has trans fat in it ? well , the only sure way to know is if you see the words , `` partially hydrogenated '' in the ingredients list . do n't let nutrition labels or advertising fool you . the fda allows manufacturers to claim that their products contain `` 0 '' grams of trans fat even if they actually have up to half a gram per serving . but there are no hard and fast rules about how small a serving can be , and , that means , you 'll have to rely on seeing those key words , partially hydrogenated , because that 's how trans fats are made , by partially hydrogenating unsaturated fats . so , let 's go back to our olive oil and pancake mix from before . olive oil is 100 % fat . pancake mix is only 11 % fat . but olive oil is mostly unsaturated fat , and it has no trans fat at all . on the other hand , more than half the fat in pancake mix is either saturated or trans fat . and , so , even though olive oil has 10 times as much fat as pancake mix , it 's healthy for you , whereas pancake mix is not . now , i 'm not trying to pick on pancake mix . there are lots of foods with this type of fat profile . the point is this : it 's not how much fat you eat , it 's what kind of fat . and what makes a particular fat healthy or unhealthy is its shape .
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fatty acids with only single bonds are called saturated , and those with one or more double bonds are called unsaturated . now , most unsaturated fats are good for you , while saturated fats are bad for you in excess . for saturated fats , the story pretty much ends there but not for unsaturated fats . the double bonds in these molecules have a kind of weird property ; they 're rigid .
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partial hydrogenation of cis ( healthy ) fats results in trans fats . what do you think full hydrogenation of unsaturated fats results in ? draw out the structures of the different types of fats ; this will help you reason through the problem .
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translator : andrea mcdonough reviewer : jessica ruby mysteries of vernacular : earwig , an insect , generally classified within the order < i > dermaptera < /i > . the common name of the insects we know as earwigs is exactly that , common , and is based mainly in folklore . it 's rumored that these so-called earwigs crawl into your ear at night and tunnel into your brain , but this is false . sure , an earwig may , on rare occasion , climb into the ear of an unsuspecting sleeper , but , really , who can blame them ? ear canals are warm and dark , the perfect home for a creepy-crawly like this one . the important thing to remember is that even if an earwig found its way into your ear , it would never eat through your eardrum . despite the erroneous origins of these trumped-up folk tales , they 've been in place a long time . the word earwig comes from the old english word earwicga , a compound of ear , meaning ear , of course , and wigca . scholars believe that wigca shares a root with words like wiggle and wag , and that it most likely referred to a creature that moves quickly . unfortunately for this innocent little insect , even its scientific name gives it a bad rap . because of the large , pencil-like cerci on the tail and of its abdomen , scientists associate earwigs with a pair of scissors , calling them < i > forficula auricularia < i > , literally little scissors of the ear .
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ear canals are warm and dark , the perfect home for a creepy-crawly like this one . the important thing to remember is that even if an earwig found its way into your ear , it would never eat through your eardrum . despite the erroneous origins of these trumped-up folk tales , they 've been in place a long time .
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even if an earwig found its way into your ear , it would never :
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translator : andrea mcdonough reviewer : jessica ruby mysteries of vernacular inaugurate : to begin or introduce a system , policy , or period or to admit someone formally into public office . the word inaugurate probably begins with the latin word avis , meaning bird . in ancient rome , avis was combined with the latin verb garrire , to talk . the two words together made augur , literally one who talks to birds . figuratively , however , augur was the name given to a specific religious official , a type of soothsayer or prophet , who foretold events by studying the behavior of birds . no major decision was made without the augur 's consultation . he would analyze flight patterns and direction , bird calls , and general bird activities , and then use these signs to interpret the will of the gods . from augur comes the verb inaugurare , to see omens from the flight of birds , and , then later , to consecrate or act when such omens are favorable . roman officials could only be installed in office when the avian omens were auspicious . centuries later , the word was eventually transmuted into english as inaugurate . along the way , it lost its veneer of superstition and was admitted formally into the jargon of politics .
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roman officials could only be installed in office when the avian omens were auspicious . centuries later , the word was eventually transmuted into english as inaugurate . along the way , it lost its veneer of superstition and was admitted formally into the jargon of politics .
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what happens when a word is transmuted into another language ?
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translator : andrea mcdonough reviewer : bedirhan cinar it is only in the last 100 or so years that human kind has understood that the nucleus of the chemical elements is not always fixed . it can change spontaneously from one element to another . the name for this process is radioactivity . you probably already know something about the nucleus : it 's much tinier than the atom , it 's made of particles called protons and neutrons , there are electrons orbiting around it . and though the atoms can share or swap electrons when they bond together , the nuclei themselves never change . right ? well , no . certain nuclei are not stable in that way . this means they may change suddenly , spontaneously . the radioactive nucleus flings out a small particle and transforms into another element , just like that . for example , the carbon nucleus can eject a fast-moving electron and turn into a nitrogen nucleus . there are two different particles that can be emitted from radioactive nuclei , but never together . the very fast electron is known as a beta particle . if you know a little bit about electrons , you may be thinking , `` what was the electron doing in the nucleus in the first place ? '' the answer is there is a neutron in nucleus spontaneously changed into a proton , which stayed behind , and the electron flew out as a beta particle . this is not what chemistry has taught us to expect . the nucleus is supposed to be stable . neutrons do n't change into protons . except , sometimes they do ! the other particle it emits spontaneously from an unstable nucleus is alpha . an alpha particle is 8,000 times more massive than beta , and it 's a bit slower . alpha is made from two protons and two neutrons . if we trap all those alpha particles together , we get helium gas . alpha is a helium nucleus . like the beta particle , you would not have expected a heavier nucleus to throw out helium . but again , it happens , and the nucleus becomes a new element . so , is radioactivity useful or just dangerous ? wherever you are sitting , it is quite likely that there is a device nearby which contains a source of alpha particles : a smoke detector . the source is radioactive americium . you are totally safe from these alpha particles , which can not travel more than a few centimeters in air . beta particles penetrate much farther through materials than alpha can . radioactive atoms are used in medicine as traces , to show where chemicals travel in the patient . beta particles are emitted and have enough energy to emerge from the body and be detected . there is a third type of nuclear radiation : gamma , which is not a particle at all . it is an electromagnetic wave , like microwaves , or light , but it is actually 1,000 times more energentic than visible light . gamma rays may pass right through your body . gamma is used to zap the bacteria in fruit to increase its shelf life , or in radiotherapy to kill cancer cells . radioactive substances get hot , and this heat can be used to generate power . this heat has been brought to you since space probes , and , in the past , in pacemakers for hearts . the more abruptly nuclear radiation is slowed down , the more damage it does to the atoms it hits . this is called ionization . alpha causes the most ionization as it crashes into other atoms and gamma the least . in humans , the most serious effect of radiation is the damage that it can cause to our dna . although alpha can not penetrate your skin , if you inhale or injest a radioactive nucleus , the health consequences can be severe . radioactivity is both useful and deadly , but it is all around us as a background to the natural world .
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this means they may change suddenly , spontaneously . the radioactive nucleus flings out a small particle and transforms into another element , just like that . for example , the carbon nucleus can eject a fast-moving electron and turn into a nitrogen nucleus . there are two different particles that can be emitted from radioactive nuclei , but never together . the very fast electron is known as a beta particle .
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a radioactive nucleus :
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[ music ] science is coming . [ music ] the game of thrones universe is one of the most brilliantly complex and utterly frustrating fictional universes ever created . but it is a fictional universe , and the only rule of a fictional universe is that it is self-consistent . it does n't have to agree with our science , or logic , or even our commonly agreed-upon moral code that says killing people is not a good thing . there is only one god in that universe , and his name is gurm . but despite that , many things in game of thrones can be linked to the real , actual world , drawing inspiration as if through the thirsty roots of a weirwood tree . many of these connections are interpreted by fans , but some have been verified by the bearded one himself . there are the many competing religious philosophies , the many , many , many similarities to real-life historical characters or the fact that they look like us ? but we are not going to be talking about those ... here 's where i would give you a spoilers warning , but . . . come on . you clicked on this . spoilers are coming . why are the seasons so crazy ? in the game of thrones universe winters and summers are known to last years at a time and apparently show up when they damn well please . we know that the summer/winter cycle normally averages around 5 or 6 years apiece , and as the story begins the most recent summer has stretched to nearly ten years . on earth , seasons are caused by our axial tilt leaning one side of earth toward or away from the sun during our annual trip around it , but george 's world is n't so predictable . the maesters of the citadel are the geeks of westeros , who are supposed to calculate when the next polar doom will arrive . westeros is n't an industrial society , but the architecture , metallurgy , and medicine we see in the known world suggests that these guys are a fairly scientific bunch . many theories have attempted to explain the reason for these seasons , but most of them collapse faster than a greyjoy 's loyalty . we know that the westeros-ian world has a moon , and that it used to have two . maybe their moon is n't as large as ours so the planet 's axis , unstabilized by lunar gravity , wobbles like a broken top . but , according to astronomers , moons do n't stabilize planets , rather a moonless planet should spin more evenly than one with a moon . then what if its orbit , instead of a nearly circular ellipse , like ours , was extremely elongated ? well that does n't work either . while it could cause extreme seasons , they 'd still show up on a regular schedule . even complex combinations of orbital stretches and wobbles , like earth 's milankovitch cycles , could be predicted by any society that knows basic algebra . well , then maybe it 's tugged on by the gravity of a neighboring planet , or its sun has a variable output . george r.r . martin did write his first novel about a planet falling away from its parent star . it 's most likely that the game of thrones planet . . . it needs a name . planet hodor ! lives in a very strange solar system , around a pair of stars . last april , a group of graduate students from johns hopkins university published a paper showing that if the world of game of thrones was subject to the complex dynamics of three celestial bodies orbiting each other , predicting a planet 's seasons would be impossible . this has interesting implications for tatooine . . ? of course , it could also be due to magic , which is cheating . and what about that world anyway ? at the amazing planetary science blog generation anthropocene , miles traer and mike osborne have constructed a detailed geologic history of westeros stretching back more than 500 million years into the fictional past . they determined that , since the north is cold enough to maintain a wall of ice , which we 'll come back to , year-round , it must be near this planet 's arctic circle , and since the south is warm enough to be covered by deserts , which primarily exist near earth 's 30th parallel that planet hodor has a radius of 4,297 miles or about 10 % wider than earth . we know that the first men crossed into westeros on a land bridge near dorne , and like africa and south america , the coastlines of westeros and essos seem to fit like puzzle pieces . they were probably unzipped beginning 25 million years ago by a spreading rift , like the one in the middle of our atlantic ocean . and 40 million years ago , westeros was likely covered by a huge ice sheet , which retreated as glaciers , cutting the great valleys south of winterfell and the riverlands between harrenhal and the twins . the description of the jagged black mountains sounds a lot like our own rocky mountains , which were born around 60-80 million years ago . this would also mark the birth of the mountains of the moon and the high westerlands , as north and south westeros smashed together just like the fault beneath the himalayas . that violent uplift is what exposed all that lannister gold from its origin deep within the crust . that era also would have borne the iron islands . . . but we have a different iron to talk about . valyrian steel was an alloy forged in the ancient empire of the valyrians , lighter and stronger than regular steel , and whose secrets were lost during the great doom , when volcanoes torched valyria , and its dragons , into charcoal . that valyrian steel was forged with dragon fire , which is not actually a thing , but it 's almost certainly a reference to damscus steel , an ancient steel alloy developed in india around 300 bc . like valyrian steel , the secrets of its forgery were lost to history forever . speaking of dragon fire . . . what if dragons could exist ? how could a living thing breathe flames ? my buddy kyle hill came up with an interesting theory . like the tiny bombardier beetle , dragons could secrete reactive `` hypergolic '' chemicals that , when mixed , react violently and shoot out of an orifice like rocket fuel . and if dragons chewed on certain rocks and metals , which i imagine are like cupcakes to them , they could coat their teeth in minerals , creating a spark with rows of deadly knife-like flint and steel . unfortunately , our idea of a fire-breathing flying dragon is about to come crashing back down to earth , because physics . as bran stark found out the hard way , gravity seems to work in westeros just like it does here . and that means the mother of dragons ' kids are grounded . the largest bird that ever lived was the giant teratorn , with a wingspan of 7 meters . not big enough . dragons are probably more like pterosaurs . but even the largest of those , quetzalcoatlus , maxed out at 11 meters from wingtip to wingtip and 250 kg . but daenarys ' dragons are bigger than that by the time they hit puberty , and dragon lore says they never stop growing . even with a pterosaur 's hollow bones , ability to gallop on all fours to take off and huge stretchy wings , even hodor could figure out that the dragons do n't work . unless , yeah . . . magic . the wall ? wo n't work . a sheer cliff of solid ice stacked 700 feet tall would melt at the bottom under its own weight and would fall apart unless it was sloped wildfire ? works . `` greek fire '' was an ancient precursor to napalm made from petroleum , sulfur , saltpeter and was the most potent weapon of its time . add a little trimethyl borate , and you 've got a flaming death that 's ready for st. patrick 's day . milk of poppy ? works . our opiate drugs from morphine to vicodin to even heroin are all derived from the poppy plant . dire wolf ? works . the extinct canis dirus was the largest wolf to ever exist , covering north and south america , thousands have been found in the la brea tar pits alone . of course , the universe of game of thrones would live . . . or die . . . just fine whether or not it agrees with our science . but by combining the two , as raymond chandler said , the truth of art keeps science from becoming inhuman , and the truth of science keeps art from becoming ridiculous what do you think ? does bringing science into a fantasy story kill the wonder like a guest at the red wedding ? or does it help the fictional world . . . truly `` exist '' in our own ? i think it makes the story richer than a lannister . let me know what you think in the comments . and remember , a hanson always pay their debts . subscribe , and i will pay you back with a new video every week . valar morcurious .
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at the amazing planetary science blog generation anthropocene , miles traer and mike osborne have constructed a detailed geologic history of westeros stretching back more than 500 million years into the fictional past . they determined that , since the north is cold enough to maintain a wall of ice , which we 'll come back to , year-round , it must be near this planet 's arctic circle , and since the south is warm enough to be covered by deserts , which primarily exist near earth 's 30th parallel that planet hodor has a radius of 4,297 miles or about 10 % wider than earth . we know that the first men crossed into westeros on a land bridge near dorne , and like africa and south america , the coastlines of westeros and essos seem to fit like puzzle pieces .
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on earth , deserts are usually located near what line of latitude ( either north or south ) ?
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sugar is playing hide and seek with you . you 'd think it would be pretty easy for you to win , considering all the sugar in sodas , ice cream , candy , and big white bags labeled sugar . people get about half of their added sugars from those drinks and treats , so it might seem like sugar is hiding in plain sight , but like someone in the witness protection program , the other half is hidden in places you 'd least suspect . check the ingredients on ketchup , bologna , spaghetti sauce , soy milk , sports drinks , fish sticks , and peanut butter . you 'll find sugar hiding in most of those products . in fact , you 'll find added sugars in three-quarters of the more than 600,000 items available in grocery stores . but how is sugar hiding ? ca n't you just look on food labels ? it 's not that easy . just like your friend robert might go by bob , robby , rob , bobby , or roberto , added sugar has a lot of aliases . and by a lot , we do n't mean five or six , try fifty-six . there 's brown rice syrup , barley malt , demerara , florida crystals , muscovado , and , of course , high fructose corn syrup , sometimes called hfcs , or corn sugar . even sugar 's tricky nicknames have nicknames . grape or apple concentrate has the same effects on your body as its 55 sugary twins . and even though organic evaporated cane juice sounds healthy , when you evaporate it , you get sugar ! chemically speaking , it 's all the same . and even trickier , when multiple added types of sugars are used in one type of product , they get buried down in a long list of ingredients , so the sugar content might appear to be okay , but when you add them all together , sugar can be the single biggest ingredient . currently , the fda does n't suggest a recommended daily limit for sugar , so it 's hard to tell if this 65 grams in a bottle of soda is a little or a lot . but the world health organization recommends limiting sugar to just 5 % of your total calories , or about 25 grams per day . so , 65 grams is well over twice that amount . but just what is sugar ? what 's the difference between glucose and fructose ? well , both are carbohydrates with the same chemical composition of carbon , hydrogen , and oxygen . but they have very different structures and behave quite differently in our bodies . glucose is the best source of energy for nearly all organisms on earth . it can be metabolized by all organs in the body . fructose , on the other hand , is metabolized primarily in the liver , and when your liver gets overloaded with sweet , sweet fructose , the excess is metabolized to fat . fresh fruits actually contain fructose , but it 's naturally occurring and does n't cause an overload because the fiber in fruit slows its absorption . this gives your liver the time it needs to do its job . it 's sugar that makes cookies chewy and candy crunchy . it even turns bread crust a beautiful , golden brown . it 's also a great preservative ; it does n't spoil or evaporate , so the foods it 's added to are easier to store and ship long distances and tend to be cheaper . that 's why sugar is hiding everywhere . actually , it might be easier to list the foods that added sugar is n't hiding in , things like : vegetables , eggs , meats , fish , fruit , raw nuts , even your kitchen sink . simply choosing water over soda , juices , and sports drinks is a great way to avoid hidden added sugar . at the very least , try to pay attention to food labels , so you can keep your sugar intake at a healthy level . because in this game of hide and seek , every time you do n't find added sugar , you win !
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in fact , you 'll find added sugars in three-quarters of the more than 600,000 items available in grocery stores . but how is sugar hiding ? ca n't you just look on food labels ? it 's not that easy .
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which is not a reason that the food industry uses to add sugar to food ?
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translator : tom carter reviewer : bedirhan cinar imagine a microscopic-sized ladder contained in the part of our brain that we 'll label our subconscious . the ladder of inference , which was first proposed by harvard professor chris argyris , is the basis of this model . every time we interact with someone , that experience enters the ladder at the bottom . that same experience zips up the ladder in the blink of an eye , exiting at the top . this process happens thousands of times a day without us knowing it . let 's focus on what happens on each rung of the ladder . on the first rung , we have the raw data and observations of our experience . this is very similar to what someone watching a video recording of our experience would see . moving up to the second rung , we filter in specific information and details from our experience . we unknowingly filter based on our preferences , tendencies , and many other aspects that we believe are important . on to the third rung . we assign meaning to the information we have filtered through . this is where we start to interpret what our information is telling us . on our fourth rung , a very crucial thing happens . we develop assumptions based on the meaning we created on the previous rung , and we start to blur the distinction between what is fact and what is story . on the fifth rung , we develop conclusions based on our assumptions . this is also where our emotional reactions are created . on the sixth rung , we adjust our beliefs about the world around us , including the person or people involved in our experience of the moment . on the seventh and final rung , we take action based on our adjusted beliefs . still with me ? great ! let 's take a real-life example and run it up the ladder to see how this all works . have you ever been cut off in a parking lot , signal light on as you steer toward your coveted spot , only to slam on your brakes at the last minute as someone pulls in front of you and steals your spot away ? imagine that experience and notice all of the data and observations landing on the first rung of your ladder . now let 's watch what we pay attention to on the second rung . who cares that it 's sunny out and the birds are chirping ? the 50 % off sign outside of your favorite store is meaningless . you filter in the sensation of your grip tightening on the wheel , you feel your blood pressure rise , you hear the squeal of your brakes , and you notice the expression on the face of the other driver as he pulls in front of you and quickly looks away . time for our third rung . ever since you were young , your parents taught you the importance of waiting in line and taking your turn . you live and die by the rule of first come , first served . and now this guy has just stolen your spot . what gives ? up to the fourth rung we go . watch closely as our assumptions take over and our story creates itself . `` that stupid jerk , did n't his parents teach him anything ? how could he not see my signal light ? he must never pay attention ! why does he think he 's more important than anyone else ? '' jumping quickly to the fifth rung , we conclude that this guy is heartless , inconsiderate , he needs to be taught a lesson and put in his place . we feel angry , frustrated , vindictive , justified . on our sixth rung , we adjust our beliefs based on the experience . `` that 's the last time i give in ! next time someone tries to cut me off , tires will be smoking on the pavement as i squeal past them into my spot . '' and finally our last rung : we take action . we back up , pull up behind his car , honk our horn , and roll down our window to scream a few choice words as well . now imagine , he walks over quickly , apologizing . his wife , who 's almost due with their first baby , called him from inside the mall to say she is in labor and needs to get to the hospital immediately . we 're momentarily shocked , apologize profusely , and wish him luck as he rushes toward the entrance . what just happened here ? what changed ? why is this so significant ? in our parking lot example , our beliefs were short-circuited by the ladder of the other individual . `` my wife is in labor , i need to get there quick , there 's a parking spot . whew ! oh , jeez , i cut someone off . i 'd better apologize quickly so they do n't think i 'm a jerk . '' but what if we were able to short-circuit our ladders ourselves ? proactively , by choice ? guess what ? we can ! let 's return to our unique human function of free will . next time you notice yourself reacting to your experience , pay focused attention to your ladder . ask yourself what beliefs are at play , where do they come from ? what data and observations did you filter in as a result of your beliefs , and why ? are your assumptions valid and supported by facts ? would a different set of assumptions create different feelings , and result in new and better conclusions and actions ? we all have our own unique ladder . be mindful of yours , and help others to see theirs .
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translator : tom carter reviewer : bedirhan cinar imagine a microscopic-sized ladder contained in the part of our brain that we 'll label our subconscious . the ladder of inference , which was first proposed by harvard professor chris argyris , is the basis of this model . every time we interact with someone , that experience enters the ladder at the bottom .
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who first proposed the ladder of inference ?
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what does the french revolution have to do with the time nasa accidentally crashed a $ 200 million orbiter into the surface of mars ? actually , everything . that crash happened due to an error in converting between two measurement systems , u.s. customary units and their s.i , or metric , equivalence . so what 's the connection to the french revolution ? let 's explain . for the majority of recorded human history , units like the weight of a grain or the length of a hand were n't exact and varied from place to place . and different regions did n't just use varying measurements . they had completely different number systems as well . by the late middle ages , the hindu-arabic decimal system mostly replaced roman numerals and fractions in europe , but efforts by scholars like john wilkins to promote standard decimal-based measures were less successful . with a quarter million different units in france alone , any widespread change would require massive disruption . and in 1789 , that disruption came . the leaders of the french revolution did n't just overthrow the monarchy . they sought to completely transform society according to the rational principles of the enlightenment . when the new government took power , the academy of sciences convened to reform the system of measurements . old standards based on arbitrary authority or local traditions were replaced with mathematical and natural relationships . for example , the meter , from the greek word for measure , was defined as 1/10,000,000 between the equator and north pole . and the new metric system was , in the words of the marquis de condorcet , `` for all people , for all time . '' standardizing measurements had political advantages for the revolutionaries as well . nobles could no longer manipulate local units to extract more rent from commoners , while the government could collect taxes more efficiently . and switching to a new republican calendar with ten-day weeks reduced church power by eliminating sundays . adoption of this new system was n't easy . in fact , it was a bit of a mess . at first , people used new units alongside old ones , and the republican calendar was eventually abandoned . when napoléon bonaparte took power , he allowed small businesses to use traditional measurements redefined in metric terms . but the metric system remained standard for formal use , and it spread across the continent , along with france 's borders . while napoléon 's empire lasted eight years , its legacy endured far longer . some european countries reverted to old measurements upon independence . others realized the value of standardization in an age of international trade . after portugal and the netherlands switched to metric voluntarily , other nations followed , with colonial empires spreading the system around the world . as france 's main rival , britain had resisted revolutionary ideas and retained its traditional units . but over the next two centuries , the british empire slowly transitioned , first approving the metric system as an optional alternative before gradually making it offical . however , this switch came too late for thirteen former colonies that had already gained independence . the united states of america stuck with the english units of its colonial past and today remains one of only three countries which have n't fully embraced the metric system . despite constant initiatives for metrication , many americans consider units like feet and pounds more intuitive . and ironically , some regard the once revolutionary metric system as a symbol of global conformity . nevertheless , the metric system is almost universally used in science and medicine , and it continues to evolve according to its original principles . for a long time , standard units were actually defined by carefully maintained physical prototypes . but thanks to improving technology and precision , these objects with limited access and unreliable longevity are now being replaced with standards based on universal constants , like the speed of light . consistent measurements are such an integral part of our daily lives that it 's hard to appreciate what a major accomplishment for humanity they 've been . and just as it arose from a political revolution , the metric system remains crucial for the scientific revolutions to come .
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old standards based on arbitrary authority or local traditions were replaced with mathematical and natural relationships . for example , the meter , from the greek word for measure , was defined as 1/10,000,000 between the equator and north pole . and the new metric system was , in the words of the marquis de condorcet , `` for all people , for all time . ''
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the word meter derives from a greek word that means :
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what is consciousness ? can an artificial machine really think ? does the mind just consist of neurons in the brain , or is there some intangible spark at its core ? for many , these have been vital considerations for the future of artificial intelligence . but british computer scientist alan turing decided to disregard all these questions in favor of a much simpler one : can a computer talk like a human ? this question led to an idea for measuring aritificial intelligence that would famously come to be known as the turing test . in the 1950 paper , `` computing machinery and intelligence , '' turing proposed the following game . a human judge has a text conversation with unseen players and evaluates their responses . to pass the test , a computer must be able to replace one of the players without substantially changing the results . in other words , a computer would be considered intelligent if its conversation could n't be easily distinguished from a human 's . turing predicted that by the year 2000 , machines with 100 megabytes of memory would be able to easily pass his test . but he may have jumped the gun . even though today 's computers have far more memory than that , few have succeeded , and those that have done well focused more on finding clever ways to fool judges than using overwhelming computing power . though it was never subjected to a real test , the first program with some claim to success was called eliza . with only a fairly short and simple script , it managed to mislead many people by mimicking a psychologist , encouraging them to talk more and reflecting their own questions back at them . another early script parry took the opposite approach by imitating a paranoid schizophrenic who kept steering the conversation back to his own preprogrammed obsessions . their success in fooling people highlighted one weakness of the test . humans regularly attribute intelligence to a whole range of things that are not actually intelligent . nonetheless , annual competitions like the loebner prize , have made the test more formal with judges knowing ahead of time that some of their conversation partners are machines . but while the quality has improved , many chatbot programmers have used similar strategies to eliza and parry . 1997 's winner catherine could carry on amazingly focused and intelligent conversation , but mostly if the judge wanted to talk about bill clinton . and the more recent winner eugene goostman was given the persona of a 13-year-old ukrainian boy , so judges interpreted its nonsequiturs and awkward grammar as language and culture barriers . meanwhile , other programs like cleverbot have taken a different approach by statistically analyzing huge databases of real conversations to determine the best responses . some also store memories of previous conversations in order to improve over time . but while cleverbot 's individual responses can sound incredibly human , its lack of a consistent personality and inability to deal with brand new topics are a dead giveaway . who in turing 's day could have predicted that today 's computers would be able to pilot spacecraft , perform delicate surgeries , and solve massive equations , but still struggle with the most basic small talk ? human language turns out to be an amazingly complex phenomenon that ca n't be captured by even the largest dictionary . chatbots can be baffled by simple pauses , like `` umm ... '' or questions with no correct answer . and a simple conversational sentence , like , `` i took the juice out of the fridge and gave it to him , but forgot to check the date , '' requires a wealth of underlying knowledge and intuition to parse . it turns out that simulating a human conversation takes more than just increasing memory and processing power , and as we get closer to turing 's goal , we may have to deal with all those big questions about consciousness after all .
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in other words , a computer would be considered intelligent if its conversation could n't be easily distinguished from a human 's . turing predicted that by the year 2000 , machines with 100 megabytes of memory would be able to easily pass his test . but he may have jumped the gun .
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what does the turing test directly measure ?
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as the story goes , the legendary marksman william tell was forced into a cruel challenge by a corrupt lord . william 's son was to be executed unless william could shoot an apple off his head . william succeeded , but let 's imagine two variations on the tale . in the first variation , the lord hires a bandit to steal william 's trusty crossbow , so he is forced to borrow an inferior one from a peasant . however , the borrowed crossbow is n't adjusted perfectly , and william finds that his practice shots cluster in a tight spread beneath the bullseye . fortunately , he has time to correct for it before it 's too late . variation two : william begins to doubt his skills in the long hours before the challenge and his hand develops a tremor . his practice shots still cluster around the apple but in a random pattern . occasionally , he hits the apple , but with the wobble , there is no guarantee of a bullseye . he must settle his nervous hand and restore the certainty in his aim to save his son . at the heart of these variations are two terms often used interchangeably : accuracy and precision . the distinction between the two is actually critical for many scientific endeavours . accuracy involves how close you come to the correct result . your accuracy improves with tools that are calibrated correctly and that you 're well-trained on . precision , on the other hand , is how consistently you can get that result using the same method . your precision improves with more finely incremented tools that require less estimation . the story of the stolen crossbow was one of precision without accuracy . william got the same wrong result each time he fired . the variation with the shaky hand was one of accuracy without precision . william 's bolts clustered around the correct result , but without certainty of a bullseye for any given shot . you can probably get away with low accuracy or low precision in everyday tasks . but engineers and researchers often require accuracy on microscopic levels with a high certainty of being right every time . factories and labs increase precision through better equipment and more detailed procedures . these improvements can be expensive , so managers must decide what the acceptable uncertainty for each project is . however , investments in precision can take us beyond what was previously possible , even as far as mars . it may surprise you that nasa does not know exactly where their probes are going to touch down on another planet . predicting where they will land requires extensive calculations fed by measurements that do n't always have a precise answer . how does the martian atmosphere 's density change at different elevations ? what angle will the probe hit the atmosphere at ? what will be the speed of the probe upon entry ? computer simulators run thousands of different landing scenarios , mixing and matching values for all of the variables . weighing all the possibilities , the computer spits out the potential area of impact in the form of a landing ellipse . in 1976 , the landing ellipse for the mars viking lander was 62 x 174 miles , nearly the area of new jersey . with such a limitation , nasa had to ignore many interesting but risky landing areas . since then , new information about the martian atmosphere , improved spacecraft technology , and more powerful computer simulations have drastically reduced uncertainty . in 2012 , the landing ellipse for the curiosity lander was only 4 miles wide by 12 miles long , an area more than 200 times smaller than viking 's . this allowed nasa to target a specific spot in gale crater , a previously un-landable area of high scientific interest . while we ultimately strive for accuracy , precision reflects our certainty of reliably achieving it . with these two principles in mind , we can shoot for the stars and be confident of hitting them every time .
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computer simulators run thousands of different landing scenarios , mixing and matching values for all of the variables . weighing all the possibilities , the computer spits out the potential area of impact in the form of a landing ellipse . in 1976 , the landing ellipse for the mars viking lander was 62 x 174 miles , nearly the area of new jersey . with such a limitation , nasa had to ignore many interesting but risky landing areas . since then , new information about the martian atmosphere , improved spacecraft technology , and more powerful computer simulations have drastically reduced uncertainty .
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what is a 'landing ellipse ' ?
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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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`` 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 . ''
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how did ptolemy ’ s execution of pompey inadvertently help cleopatra come to power ?
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modern computers are revolutionizing our lives , performing tasks unimaginable only decades ago . this was made possible by a long series of innovations , but there 's one foundational invention that almost everything else relies upon : the transistor . so what is that , and how does such a device enable all the amazing things computers can do ? well , at their core , all computers are just what the name implies , machines that perform mathematical operations . the earliest computers were manual counting devices , like the abacus , while later ones used mechanical parts . what made them computers was having a way to represent numbers and a system for manipulating them . electronic computers work the same way , but instead of physical arrangements , the numbers are represented by electric voltages . most such computers use a type of math called boolean logic that has only two possible values , the logical conditions true and false , denoted by binary digits one and zero . they are represented by high and low voltages . equations are implemented via logic gate circuits that produce an output of one or zero based on whether the inputs satisfy a certain logical statement . these circuits perform three fundamental logical operations , conjunction , disjunction , and negation . the way conjunction works is an `` and gate '' provides a high-voltage output only if it receives two high-voltage inputs , and the other gates work by similar principles . circuits can be combined to perform complex operations , like addition and subtraction . and computer programs consist of instructions for electronically performing these operations . this kind of system needs a reliable and accurate method for controlling electric current . early electronic computers , like the eniac , used a device called the vacuum tube . its early form , the diode , consisted of two electrodes in an evacuated glass container . applying a voltage to the cathode makes it heat up and release electrons . if the anode is at a slightly higher positive potential , the electrons are attracted to it , completing the circuit . this unidirectional current flow could be controlled by varying the voltage to the cathode , which makes it release more or less electrons . the next stage was the triode , which uses a third electrode called the grid . this is a wire screen between the cathode and anode through which electrons could pass . varying its voltage makes it either repel or attract the electrons emitted by the cathode , thus , enabling fast current-switching . the ability to amplify signals also made the triode crucial for radio and long distance communication . but despite these advancements , vacuum tubes were unreliable and bulky . with 18,000 triodes , eniac was nearly the size of a tennis court and weighed 30 tons . tubes failed every other day , and in one hour , it consumed the amount of electricity used by 15 homes in a day . the solution was the transistor . instead of electrodes , it uses a semiconductor , like silicon treated with different elements to create an electron-emitting n-type , and an electron absorbing p-type . these are arranged in three alternating layers with a terminal at each . the emitter , the base , and the collector . in this typical npn transistor , due to certain phenomena at the p-n interface , a special region called a p-n junction forms between the emitter and base . it only conducts electricity when a voltage exceeding a certain threshold is applied . otherwise , it remains switched off . in this way , small variations in the input voltage can be used to quickly switch between high and low-output currents . the advantage of the transistor lies in its efficiency and compactness . because they do n't require heating , they 're more durable and use less power . eniac 's functionality can now be surpassed by a single fingernail-sized microchip containing billions of transistors . at trillions of calculations per second , today 's computers may seem like they 're performing miracles , but underneath it all , each individual operation is still as simple as the flick of a switch .
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tubes failed every other day , and in one hour , it consumed the amount of electricity used by 15 homes in a day . the solution was the transistor . instead of electrodes , it uses a semiconductor , like silicon treated with different elements to create an electron-emitting n-type , and an electron absorbing p-type .
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when does a transistor ‘ conduct ’ ?
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suppose you placed a camera at a fixed position , took a picture of the sky at the same time everyday for an entire year and overlayed all of the photos on top of each other . what would the sun look like in that combined image ? a stationary dot ? a circular path ? neither . oddly enough , it makes this figure eight pattern , known as the sun 's analemma , but why ? the earth 's movement creates a few cycles . first of all , it rotates on its axis about once every 24 hours , producing sunrises and sunsets . at the same time , it 's making a much slower cycle , orbiting around the sun approximately every 365 days . but there 's a twist . relative to the plane of its orbit , the earth does n't spin with the north pole pointing straight up . instead , its axis has a constant tilt of 23.4 degrees . this is known as the earth 's axial tilt , or obliquity . a 23-degree tilt may not seem important , but it 's the main reason that we experience different seasons . because the axis remains tilted in the same direction while the earth makes its annual orbit , there are long periods each year when the northern half of the planet remains tilted toward the sun while the southern half is tilted away and vice versa , what we experience as summer and winter . during summer in a given hemisphere , the sun appears higher in the sky , making the days longer and warmer . once a year , the sun 's declination , the angle between the equator and the position on the earth where the sun appears directly overhead reaches its maximum . this day is known as the summer solstice , the longest day of the year , and the one day where the sun appears highest in the sky . so the earth 's axial tilt partially explains why the sun changes positions in the sky and the analemma 's length represents the full 46.8 degrees of the sun 's declination throughout the year . but why is it a figure eight and not just a straight line ? this is due to another feature of the earth 's revolution , its orbital eccentricity . the earth 's orbit around the sun is an ellipse , with its distance to the sun changing at various points . the corresponding change in gravitational force causes the earth to move fastest in january when it reaches its closest point to the sun , the perihelion , and the slowest in july when it reaches its farthest point , the aphelion . the earth 's eccentricity means that solar noon , the time when the sun is highest in the sky , does n't always occur at the same point in the day . so a sundial may be as much as sixteen minutes ahead or fourteen minutes behind a regular clock . in fact , clock time and sun time only match four times a year . the analemma 's width represents the extent of this deviation . so how did people know the correct time years ago ? for most of human history , going by the sun 's position was close enough . but during the modern era , the difference between sundials and mechanical clocks became important . the equation of time , introduced by ptolemy and later refined based on the work of johannes kepler , converts between apparent solar time and the mean time we 've all come to rely on . globes even used to have the analemma printed on them to allow people to determine the difference between clock time and solar time based on the day of the year . just how the analemma appears depends upon where you are . it will be tilted at an angle depending on your latitude or inverted if you 're in the southern hemisphere . and if you 're on another planet , you might find something completely different . depending on that planet 's orbital eccentricity and axial tilt , the analemma might appear as a tear drop , oval , or even a straight line .
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this is due to another feature of the earth 's revolution , its orbital eccentricity . the earth 's orbit around the sun is an ellipse , with its distance to the sun changing at various points . the corresponding change in gravitational force causes the earth to move fastest in january when it reaches its closest point to the sun , the perihelion , and the slowest in july when it reaches its farthest point , the aphelion .
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the earth moves around the sun ___________ .
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( music ) everything is everywhere these days . check out the supermarket -- orange juice from china , nuts from india , swordfish from japan , lagers from czechoslovakia , scores of european cheeses . you name it , it 's there . not when i was growing up . you 'd never taste a range of french cheeses or bohemian lager beer . at least , you could n't unless you were very rich and could go anywhere when the fancy took you . all that has changed . but it 's not just foods . got an iphone ? everyone knows it was invented and designed at cupertino in california , but who knows where the complex bits and pieces of its innards are made or assembled ? apple does n't say . the industry credits china , japan , germany , south korea and , of course , the united states itself . just think for a moment of the trillions of parts and finished goods moving cheaply around the world every second , a small portion by air , but most by sea . we call it globalization , but the man who basically made globalization a reality in our lives is too little known . this is his story . the story of the man who makes your day . in the great depression of the '30s , when millions of americans were out of work , worse than now , malcolm mclean was a 24-year-old truck driver . he got a job to take cotton bales from fayetteville in north carolina all the way to a pier in hoboken , new jersey for shipping overseas . he was glad of the work , but when he arrived he got bored out of his mind , sitting in his truck waiting and waiting and waiting on the docks as the worker ants muscled crates and bundles off other trucks and into slings that lifted the goods into the hold of the ship . on board the ship itself , with much yelling and arm waving , the stevedores then unloaded each sling and saw its contents placed in a designated position in the hold . malcolm was n't just bored , he was fuming . his income depended on getting back to north carolina to pick up more loads in his truck . out of the frustration , inspiration struck . would n't it be great , he thought , if my trailer could be lifted and placed on the ship without its cotton bales being touched . yes , it would be great . it would be revolutionary . for centuries , general non-bulk cargo had been shipped in the process he watched . it was called break bulk shipping . boxes , bales , crates handled piece by piece . what malcolm envisaged would have saved him only a day , but it would have saved everyone else something like two weeks in loading and unloading the ship . on average , it was eight days to haul and distribute break bulk shipments in the hold , plus another eight days at the other end to retrieve and distribute . all that time would have been saved if malcolm mclean could have just driven his truck onto the ship and at the other end , driven it off . well , today that concept is a reality . the concept that occurred to malcolm is known as containerization . it has done more than just save a great deal of time . it 's the reason why we have a thriving global marketplace , offering us that infinite variety of things , and it 's the reason we can move cargo from remote parts of the world at minimal cost . malcolm had his idea in 1937 . the 24-year-old truck driver sitting in his truck in hoboken was 40 before he did anything about it . by then , he 'd built his one truck into a big trucking company . he borrowed money from an enterprising vice president at citibank in new york , and set about designing the steel boxes and the decks of the ships to carry them stacked one on top of another . a lot of people thought he was crazy . inventors always attract armies of naysayers who can never remember how critical they were . for our part , we should remember malcolm mclean . his first container ship , the ideal x , sailed from shed 154 at marsh street , port newark with 58 well-filled boxes . it was the beginning of the container era , shrinking our world and enlarging human choice .
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inventors always attract armies of naysayers who can never remember how critical they were . for our part , we should remember malcolm mclean . his first container ship , the ideal x , sailed from shed 154 at marsh street , port newark with 58 well-filled boxes .
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what did mclean want to ship overseas ?
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in the winter of 1995 , scientists pointed the hubble telescope at an area of the sky near the big dipper , a spot that was dark and out of the way of light pollution from surrounding stars . the location was apparently empty , and the whole endeavor was risky . what , if anything , was going to show up ? over ten consecutive days , the telescope took close to 150 hours of exposure of that same area . and what came back was nothing short of spectacular : an image of over 1,500 distinct galaxies glimmering in a tiny sliver of the universe . now , let 's take a step back to understand the scale of this image . if you were to take a ballpoint pen and hold it at arm 's length in front of the night sky , focusing on its very tip , that is what the hubble telescope captured in its first deep field image . in other words , those 3,000 galaxies were seen in just a tiny speck of the universe , approximately one two-millionth of the night sky . to put all this in perspective , the average human measures about 1.7 meters . with earth 's diameter at 12,700 kilometers , that 's nearly 7.5 million humans lined up head to toe . the apollo 8 astronauts flew a distance of 380,000 kilometers to the moon . and our relatively small sun has a diameter of about 1.4 million kilometers , or 110 times the earth 's diameter . a step further , the milky way holds somewhere between 100 to 400 billion stars , including our sun . and each glowing dot of a galaxy captured in the deep field image contains billions of stars at the very least . almost a decade after taking the deep field image , scientists adjusted the optics on the hubble telescope and took another long exposure over a period of about four months . this time , they observed 10,000 galaxies . half of these galaxies have since been analyzed more clearly in what 's known as the extreme deep field image , or xdf . by combining over ten years of photographs , the xdf shows galaxies so distant that they 're only one ten-billionth the brightness that the human eye can perceive . so , what can we learn about the universe from the deep field images ? in a study of the universe , space and time are inextricably linked . that 's because of the finite speed of light . so the deep field images are like time machines to the ancient universe . they reach so far into space and time that we can observe galaxies that existed over 13 billion years ago . this means we 're looking at the universe as it was less than a billion years after the big bang , and it allows scientists to research galaxies in their infancy . the deep field images have also shown that the universe is homogeneous . that is , images taken at different spots in the sky look similar . that 's incredible when we think about how vast the universe is . why would we expect it to be the same across such huge distances ? on the scale of a galaxy , let alone the universe , we 're smaller than we can readily comprehend , but we do have the capacity to wonder , to question , to explore , to investigate , and to imagine . so the next time you stand gazing up at the night sky , take a moment to think about the enormity of what is beyond your vision , out in the dark spaces between the stars .
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and each glowing dot of a galaxy captured in the deep field image contains billions of stars at the very least . almost a decade after taking the deep field image , scientists adjusted the optics on the hubble telescope and took another long exposure over a period of about four months . this time , they observed 10,000 galaxies .
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how many months did hubble spend gathering the images ( exposures ) used to create the hubble deep field image ?
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to human eyes , the world at night is a formless canvas of grey . many nocturnal animals , on the other hand , experience a rich and varied world bursting with details , shapes , and colors . what is it , then , that separates moths from men ? moths and many other nocturnal animals see at night because their eyes are adapted to compensate for the lack of light . all eyes , whether nocturnal or not , depend on photoreceptors in the retina to detect light particles , known as photons . photoreceptors then report information about these photons to other cells in the retina and brain . the brain sifts through that information and uses it to build up an image of the environment the eye perceives . the brighter the light is , the more photons hit the eye . on a sunny day , upwards of 100 million times more photons are available to the eye than on a cloudy , moonless night . photons are n't just less numerous in darkness , but they also hit the eye in a less reliable way . this means the information that photoreceptors collect will vary over time , as will the quality of the image . in darkness , trying to detect the sparse scattering of randomly arriving photons is too difficult for the eyes of most daytime animals . but for night creatures , it 's just a matter of adaptation . one of these adaptations is size . take the tarsier , whose eyeballs are each as big as its brain , giving it the biggest eyes compared to head size of all mammals . if humans had the same brain to eye ratio , our eyes would be the size of grapefruits . the tarsier 's enlarged orbs have n't evolved to make it cuter , however , but to gather as much light as possible . bigger eyes can have larger openings , called pupils , and larger lenses , allowing for more light to be focused on the receptors . while tarsiers scan the nocturnal scene with their enormous peepers , cats use gleaming eyes to do the same . cats ' eyes get their shine from a structure called the tapetum lucidum that sits behind the photoreceptors . this structure is made from layers of mirror-like cells containing crystals that send incoming light bouncing back towards the photoreceptors and out of the eye . this results in an eerie glow , and it also gives the photoreceptors a second chance to detect photons . in fact , this system has inspired the artificial cats ' eyes we use on our roads . toads , on the other hand , have adapted to take it slow . they can form an image even when just a single photon hits each photoreceptor per second . they accomplish this with photoreceptors that are more than 25 times slower than human ones . this means toads can collect photons for up to four seconds , allowing them to gather many more than our eyes do at each visual time interval . the downside is that this causes toads to react very slowly because they 're only receiving an updated image every four seconds . fortunately , they 're accustomed to targeting sluggish prey . meanwhile , the night is also buzzing with insects , such as hawk moths , which can see their favorite flowers in color , even on a starlit night . they achieve this by a surprising move - getting rid of details in their visual perception . information from neighboring photoreceptors is grouped in their brains , so the photon catch of each group is higher compared to individual receptors . however , grouping photoreceptors loses details in the image , as fine details require a fine grid of photoreceptors , each detecting photons from one small point in space . the trick is to balance the need for photons with the loss of detail to still find their flowers . whether eyes are slow , enormous , shiny , or coarse , it 's the combination of these biological adaptations that gives nocturnal animals their unique visual powers . imagine what it might be like to witness through their eyes the world that wakes up when the sun goes down .
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fortunately , they 're accustomed to targeting sluggish prey . meanwhile , the night is also buzzing with insects , such as hawk moths , which can see their favorite flowers in color , even on a starlit night . they achieve this by a surprising move - getting rid of details in their visual perception .
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seeing at night is problematic , because there are :
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some people ca n't see the forest for the trees , but before stephen sillett , no one could see or even imagine the forest in the trees . stephen was an explorer of new worlds from the start . he spent his boyhood in harrisburg , pennsylvania reading tolkien and playing dungeons and dragons with his brother scott . but when the sillett family visited their grandparent 's cabin near gettysburg , their grandmother helen poe sillett , would take the boys into the nearby mountains and forests to bird-watch . they called grandma sillett poe , and she taught the boys to identify songbirds , plants and even lichens , creatures that often look like splotches of carpet glued to the shady sides of rocks and tree trunks . looking upwards , both boys found their callings . scott became a research scientist specializing in migratory birds . stephen was more interested in the trees . the tangle of branches and leaves attracted his curiosity . what could be hidden up there ? by the time stephen was in college , that curiosity pulled him skyward to the tallest trees on earth : the ancient coast redwoods of northern california . rising from trunks up to 20 feet in diameter , redwoods can grow up to 380 feet , or 38 stories , over a 2,000 year lifetime . but no one had thought to investigate the crowns of these natural skyscrapers . were there more than just branches up there ? stephen decided to find out firsthand . in 1987 , stephen , his brother scott and his friend marwood drove from reed college in oregon to prairie creek redwoods state park in northern california . deep inside the park , stephen picked the tallest redwood he could find . its lowest branches were almost 100 feet up , far beyond his reach . but he saw a younger , shorter redwood growing next to the target tree . with a running start , he leapt and grabbed the lowest branch , pulled himself up and scurried upwards . he was free climbing without ropes or a harness , one misstep meant death . but up he went , and when he reached the peak , he swayed and leapt across the gap of space onto a branch of the target tree and into a world never seen before . his buddy marwood followed him up , and the two young men free climbed high into the redwood 's crown . stephen came across lichens like grandma poe had shown him as a boy . he noticed that the higher he went , the thicker the branches were , not the case with most trees . he found moist mats of soil many inches thick , made from fallen needles , bark , other plant debris and dust from the sky piled on the tops of the large branches . he even found reiterations : new redwood tree trunks growing out from the main trunk . the redwood had cloned itself . when stephen reached the pinnacle , he rested on a platform of crisscrossing branches and needles . growing in the soil mat was a huckleberry bush with ripe berries ! he ate some and waited for his friend . stephen had discovered a new world hundreds of feet above the ground . his climb led to more excursions , with safety equipment , thank goodness , up other ancient redwoods as he mapped and measured the architecture of branches and additional trunks in the canopy of an entire grove . stephen became an expert in the ecology of the tallest trees on earth and the rich diversity of life in their crowns , aerial ecosystems no one had imagined . there are ferns , fungi and epiphytic trees normally found at ground level like douglas firs , hemlocks and tan oaks whose roots had taken hold in the rich wet soil mats . invertebrates such as ants , bumblebees , mites , beetles , earthworms and aquatic crustacean copepods make their homes alongside flowering plants like rhododendrons , currant and elderberry bushes . ospreys , spotted owls , and jays search the canopy for food . even the marbled murrelet , a pacific seabird , flies many miles from the ocean to nest there . squirrels and voles peek out of penthouse burrows . and the top predator ? the mighty wandering salamander ! sillett 's research has changed how we think about tall trees , and bolstered the case for their conservation , not just as impressive individual organisms but as homes to countless other species . so when you look up into the branches and leaves of a tree , ask , `` what else is up there ? '' a new world might be just out of reach . so leap for it .
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in 1987 , stephen , his brother scott and his friend marwood drove from reed college in oregon to prairie creek redwoods state park in northern california . deep inside the park , stephen picked the tallest redwood he could find . its lowest branches were almost 100 feet up , far beyond his reach .
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what did stephen observe on the tops of large branches inside the crown ?
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have you ever walked into a grocery store and wondered where all those variety of apples came from ? you might find snapdragon , pixie crunch , cosmic crisp , jazz , or ambrosia next to the more familiar red delicious and granny smith . these delightfully descriptive names belong to just a handful of the over 7,500 apple varieties in the world . this huge diversity exists largely because of humanity 's efforts to bear new fruit . fruit breeding is a way to fulfill the expectations of farmers and consumers who seek specific qualities in an apple . on the one hand , farmers may want them to be disease-resistant and to store well . on the other , consumers are swayed by appearance , taste , and novelty . so , breeders have to consider everything from how well apples grow in certain climates to their color , taste , and size . and sometimes finding the perfect fit means breeding something new . to create apples with desirable characteristics , breeders first need to find parent apples that carry those characteristics . once the parents have been selected , they have to wait until the trees bloom in the spring . the breeder takes the pollen from one bloom , called the father , and transfers it by hand to the other parent bloom , called the mother , through a process called cross-pollination . once the mother bloom turns into an apple , the seeds are collected and then planted . it takes about five years for these seeds to grow into trees that produce apples , but because of the way traits are inherited , all of the seedlings produced will have different sets of genes and characteristics . this means that to achieve a desired quality , it takes a lot of offspring , not to mention patience on the breeder 's part . when a seedling does bear fruit with the desired qualities , it 's selected for further evaluation . of the original crossed seedlings , about one in every 5,000 makes it to this prestigious stage . they 're then sent to new farms where breeders can assess how various climates and soil types affect the plant 's growth . the fruit of the seedling and its many clones must then be collected and sampled to ensure consistency . breeders study about 45 traits in an apple , like the texture and firmness of the flesh , when it ripens , how sugary its juice is , and how long it stays fresh . over several years , they weed out all the bad apples , selecting only those whose fruits are the best . these exclusive plants officially form the cultivar , or new apple variety . to ensure an exact copy of this cultivar , all apple trees must be grafted from the original seedling . branches , called scion wood , are cut from the original tree and grown to generate more scion wood . segments of these trees are then grafted onto root stalk - that 's the lower section of another tree that 's been chosen from a different cultivar for its superior roots and growing ability . finally , this fusion creates a new apple tree with the desired qualities . each new plant takes up to four years before it starts producing the fruit we eat . apple breeding may be a difficult art , but it 's accessible to all : universities , companies , and even individuals can create new cultivars . but to fully own an apple , the breeder faces a final challenge - naming the fruit . after a cultivar is patented , a breeder chooses a name for its trademark . that final step grants them long-lasting rights over the apple and its clones . that name must be completely original , and the catchier , the better , of course . with over 7,500 varieties and counting , that 's why we have apples called pink lady , sweet tango , kiku , and evercrisp . the more we work with nature 's bounty to breed new cultivars , the more creative and delectable these names will become .
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so , breeders have to consider everything from how well apples grow in certain climates to their color , taste , and size . and sometimes finding the perfect fit means breeding something new . to create apples with desirable characteristics , breeders first need to find parent apples that carry those characteristics . once the parents have been selected , they have to wait until the trees bloom in the spring .
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who can create new varieties of apples ?
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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 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 .
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suppose that a cell has a mutation in one of its brca1 genes that inactivates the gene . what will this do to the rate at which the cell divides ?
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translator : andrea mcdonough reviewer : bedirhan cinar i got in my first car accident when i was sixteen . i had just gotten my license and i was driving home when a car pulled into the intersection and bang ! it hit me . it had happened that quick . bang ! but when i play that memory back , it does n't take two seconds . i see the tires of the car rolling through the stop sign , i have time to think , `` you know , i think that car is going to hit me . '' i see the right-hand corner of the hood crumple up like tin foil , i see the red paint flake off and drift off into the air , i can see all of that , like it 's happening in slow motion . in my memory , that experience takes ten seconds . but why ? why did that memory play back longer than the actual time it took ? this is an interesting phenomenon and it 's not just for car accidents , a roller coaster , or a first kiss . these events seem to take longer than they actually take . but why ? and when it comes to writing about that experience , how do i get that peculiar feeling across ? how do i slow down time as a writer ? to get the answer , we have to visit hollywood . you see , the way filmmakers create slow motion will tell us a lot about how writers can create slow motion . first , let 's remember how film works . when the camera turns on , it 's not recording motion , it 's taking lots and lots of individual pictures . then when those pictures are played back in the projector , they blend together and create the appearance of motion , like a flip book . so , let 's imagine that a camera man needs to film his actress skipping through a field of daisies in regular motion . ready , action . she skips across the field , he records it , and ... cut . let 's say for the sake of easy math that our camera man took 50 pictures , 50 little frames on that length of film . now , let 's take that film and play it back at the rate of 50 frames per 5 seconds . this rate is constant , the projector will always go at the same speed . it 's easy , we got 50 frames , so our film takes 5 seconds . she skips across the field ... ... and cut ! so , then , how do we slow down time in film ? how do we create slow motion ? maybe this is a surprise , but we do n't take less pictures , we take more pictures . ready , action ! she skips across the field , he records it , and cut . now we have a lot of film , a long length , let 's say 100 frames long . now , when we play it back , it takes a longer time to get through , and there 's the actress in slow motion . skipping through the field of daisies ! which brings us now to writing . when you 're writing a narrative , you may want to use slow motion in one of your scenes . it 's a cool effect , just like it is in hollywood , and it draws the reader 's attention to important moments . well , here 's how you do it . you see , when we read , our brain makes the words into pictures and the pictures blend into action . so what we read is what we see in the time it takes us to read it . for example , imagine you 're writing a narrative about your game-winning free throw in the championship game . here 's a moment as a writer that you might want to slow down time to really capture the second-by-second tension produced by the scene . you concentrate , you put the pencil to paper , you really want to slow down time , you write , `` i shot the ball in the hoop . time slowed down . then we won . '' to read that , takes two seconds ; therefore , your reader imagines a scene that takes two seconds . ball goes up , comes down , done . see , even though you wrote , `` time slowed down , '' you did n't achieve that effect for your reader . just saying it does n't make it happen . now , let 's take what we make about film , time slows down with more pictures , and try again . this time write a lot more . `` i bent my knees and held the ball loosely . letting the ball bounce on the floor once more , i gathered my thoughts . this was the moment . my right arm extended as i released the ball with a gentle flick , it rotated slightly as it arched toward the rim . i held my breath . the ball nudged the back rim , falling through the net with a gentle , satisfying swish . and the crowd exploded from their seats . '' see , we just slowed down time through our writing . the bottom line is this : there are moments in life that take longer than they actually take . when you 're planning out your narrative , think about those moments , those snippets of life that took longer than the watch : the moment of hearing bad news , the moment of hearing good news , the moment of exhilaration when you realize you hit the jump , or the moment when you realize you are n't going to land it . once you identify these moments in your narrative , you can use this effect of slow motion when you write . just remember , it 's not enough to say , `` time slowed down '' and it 's not enough to throw a couple adjectives in a sentence and call it done either . descriptive writing is good writing , that 's true . but if you want to express the feeling of slow motion in life , you have to actually take up more physical space on the page , use more film so to speak . in doing so , you will create tension and keep your reader interested . and that way , the next time you write , you 'll control the camera of your own writing .
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you concentrate , you put the pencil to paper , you really want to slow down time , you write , `` i shot the ball in the hoop . time slowed down . then we won . ''
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what 's an example of how time slowed down in literature ? what do you think made this effective ?
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in 1997 , in a game between france and brazil , a young brazilian player named roberto carlos set up for a 35 meter free kick . with no direct line to the goal , carlos decided to attempt the seemingly impossible . his kick sent the ball flying wide of the players , but just before going out of bounds , it hooked to the left and soared into the goal . according to newton 's first law of motion , an object will move in the same direction and velocity until a force is applied on it . when carlos kicked the ball , he gave it direction and velocity , but what force made the ball swerve and score one of the most magnificent goals in the history of the sport ? the trick was in the spin . carlos placed his kick at the lower right corner of the ball , sending it high and to the right , but also rotating around its axis . the ball started its flight in an apparently direct route , with air flowing on both sides and slowing it down . on one side , the air moved in the opposite direction to the ball 's spin , causing increased pressure , while on the other side , the air moved in the same direction as the spin , creating an area of lower pressure . that difference made the ball curve towards the lower pressure zone . this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful . but curving the ball with the precision needed to both bend around the wall and back into the goal is difficult . too high and it soars over the goal . too low and it hits the ground before curving . too wide and it never reaches the goal . not wide enough and the defenders intercept it . too slow and it hooks too early , or not at all . too fast and it hooks too late . the same physics make it possible to score another apparently impossible goal , an unassisted corner kick . the magnus effect was first documented by sir isaac newton after he noticed it while playing a game of tennis back in 1670 . it also applies to golf balls , frisbees and baseballs . in every case , the same thing happens . the ball 's spin creates a pressure differential in the surrounding air flow that curves it in the direction of the spin . and here 's a question . could you theoretically kick a ball hard enough to make it boomerang all the way around back to you ? sadly , no . even if the ball did n't disintegrate on impact , or hit any obstacles , as the air slowed it , the angle of its deflection would increase , causing it to spiral into smaller and smaller circles until finally stopping . and just to get that spiral , you 'd have to make the ball spin over 15 times faster than carlos 's immortal kick . so good luck with that .
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that difference made the ball curve towards the lower pressure zone . this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful .
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in which of these sports can one not observe the magnus effect ?
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your favorite band is great at playing music , but not so great at being organized . they keep misplacing their instruments on tour , and it 's driving their manager mad . on the day of the big concert , the band wakes up to find themselves tied up in a windowless , soundproof practice room . their manager explains what 's happening . outside , there are ten large boxes . each contains one of your instruments , but do n't be fooled by the pictures - they 've been randomly placed . i 'm going to let you out one at a time . while you 're outside , you can look inside any five boxes before security takes you back to the tour bus . you ca n't touch the instruments or in any way communicate what you find to the others . no marking the boxes , shouting , nothing . if each one of you can find your own instrument , then you can play tonight . otherwise , the label is dropping you . you have three minutes to think about it before we start . the band is in despair . after all , each musician only has a 50 % chance of finding their instrument by picking five random boxes . and the chances that all ten will succeed are even lower - just 1 in 1024 . but suddenly , the drummer comes up with a valid strategy that has a better than 35 % chance of working . can you figure out what it was ? pause the video on the next screen if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 here 's what the drummer said : everyone first open the box with the picture of your instrument . if your instrument is inside , you 're done . otherwise , look at whatever 's in there , and then open the box with that picture on it . keep going that way until you find your instrument . the bandmates are skeptical , but amazingly enough , they all find what they need . and a few hours later , they 're playing to thousands of adoring fans . so why did the drummer 's strategy work ? each musician follows a linked sequence that starts with the box whose outside matches their instrument and ends with the box actually containing it . note that if they kept going , that would lead them back to the start , so this is a loop . for example , if the boxes are arranged like so , the singer would open the first box to find the drums , go to the eighth box to find the bass , and find her microphone in the third box , which would point back to the first . this works much better than random guessing because by starting with the box with the picture of their instrument , each musician restricts their search to the loop that contains their instrument , and there are decent odds , about 35 % , that all of the loops will be of length five or less . how do we calculate those odds ? for the sake of simplicity , we 'll demonstrate with a simplified case , four instruments and no more than two guesses allowed for each musician . let 's start by finding the odds of failure , the chance that someone will need to open three or four boxes before they find their instrument . there are six distinct four-box loops . one fun way to count them is to make a square , put an instrument at each corner , and draw the diagonals . see how many unique loops you can find , and keep in mind that these two are considered the same , they just start at different points . these two , however , are different . we can visualize the eight distinct three-box loops using triangles . you 'll find four possible triangles depending on which instrument you leave out , and two distinct paths on each . so of the 24 possible combinations of boxes , there are 14 that lead to faliure , and ten that result in success . that computational strategy works for any even number of musicians , but if you want a shortcut , it generalizes to a handy equation . plug in ten musicians , and we get odds of about 35 % . what if there were 1,000 musicians ? 1,000,000 ? as n increases , the odds approach about 30 % . not a guarantee , but with a bit of musician 's luck , it 's far from hopeless . hi everybody , if you liked this riddle , try solving these two .
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one fun way to count them is to make a square , put an instrument at each corner , and draw the diagonals . see how many unique loops you can find , and keep in mind that these two are considered the same , they just start at different points . these two , however , are different . we can visualize the eight distinct three-box loops using triangles .
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how many different possibilities are there to arrange 10 instruments in 10 boxes ?
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ok , so thulium is a very expensive lanthanide . it ’ s very expensive because it ’ s very hard to separate it from its neighbours . the lanthanides from the left to right undergo this contraction where they get smaller and smaller and over on the right-hand-side at this point that they are all of a very similar size . now we can separate them now but it is quite difficult to do and therefore quite expensive , so thulium is not used very often . however thulium , as well as being able to obtain the plus-3 oxidation state , it is also one of those ones which can obtain the plus-2 oxidation state , which means that chemists are now beginning to find uses for it which they hadn ’ t expected before . so you may see the use of thulium increase in years to come . because it ’ s very hard to isolate because it ’ s of a very similar size to its neighbours , it took a guy called charles james , in 1911 , a famous 15,000 times of recrystalization to isolate thulium in a pure , albeit as a chloride , but a pure nonetheless , compound for the first time .
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however thulium , as well as being able to obtain the plus-3 oxidation state , it is also one of those ones which can obtain the plus-2 oxidation state , which means that chemists are now beginning to find uses for it which they hadn ’ t expected before . so you may see the use of thulium increase in years to come . because it ’ s very hard to isolate because it ’ s of a very similar size to its neighbours , it took a guy called charles james , in 1911 , a famous 15,000 times of recrystalization to isolate thulium in a pure , albeit as a chloride , but a pure nonetheless , compound for the first time .
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regarding its oxidation states , why is the use of thulium likely to increase in years to come ?
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have you ever heard the sound of frogs calling at night ? for hundreds of millions of years , this croaking lullaby has filled the nighttime air . but recent studies suggest that these frogs are in danger of playing their final note . over the past few decades , amphibian populations have been rapidly disappearing worldwide . nearly one-third of the world 's amphibian species are endanger of extinction , and over 100 species have already disappeared . but do n't worry , there 's still hope . before we get into how to save the frogs , let 's start by taking a look at why they 're disappearing and why it 's important to keep them around . habitat destruction is the number one problem for frog populations around the world . there are seven billion humans on the planet , and we compete with frogs for habitat . we build cities , suburbs , and farms on top of frog habitat and chop forests and drain the wetlands that serve as home for numerous amphibian populations . climate change alters precipitation levels , drying up ponds , streams , and cloud forests . as the earth 's human population continues to grow , so will the threats amphibians face . there are a variety of other factors contributing to the frogs ' decline . over-harvesting for the pet and food trade results in millions of frogs being taken out of the wild each year . invasive species , such as non-native trout and crawfish , eat native frogs . humans are facilitating the spread of infectious diseases by shipping over 100 million amphibians around the world each year for use as food , pets , bait , and in laboratories and zoos , with few regulations or quarantines . one of these diseases , chytridiomycosis , has driven stream-dwelling amphibian populations to extinction in africa , australia , europe , and north , central , and south america . on top of all these problems , we add hundreds of millions of kilograms of pesticides to our ecosystems each year . and these chemicals are easily absorbed through amphibians ' permeable skin , causing immunosuppression , or a weakened immune system , and developmental deformities . okay , so why are these little green guys worth keeping around ? frogs are important for a multitude of reasons . they 're an integral part of the food web , eating flies , ticks , mosquitoes , and other disease vectors , thus , protecting us against malaria , dengue fever , and other illnesses . tadpoles keep waterways clean by feeding on algae , reducing the demand on our community 's filtration systems and keeping our cost of water low . frogs serve as a source of food for birds , fish , snakes , dragonflies , and even monkeys . when frogs disappear , the food web is disturbed , and other animals can disappear as well . amphibians are also extremely important in human medicine . over ten percent of the nobel prizes in physiology and medicine have gone to researchers whose work depended on amphibians . some of the antimicrobial peptides on frog skin can kill hiv , some act as pain killers , and others serve as natural mosquito repellents . many discoveries await us if we can save the frogs , but when a frog species disappears , so does any promise it holds for improving human health . fortunately , there are lots of ways you can help , and the best place to start is by improving your ecological footprint and day-to-day actions . the next time you listen to that nighttime lullaby , do n't think of it as just another background noise , hear it as a call for help , sung in perfect croaking harmony .
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over the past few decades , amphibian populations have been rapidly disappearing worldwide . nearly one-third of the world 's amphibian species are endanger of extinction , and over 100 species have already disappeared . but do n't worry , there 's still hope .
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where do frogs live in your part of the world ? search the web to find a list of species living in your geographical area . maybe you can find some friends or local scientists and go to a local wetland ( be safe ! ) .
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in 1796 , thomas jefferson received a box of bones he could n't identify . a long , sharp claw reminded him of a lion , but the arm bones suggested a larger animal , one about three meters long . thinking it might be huge unknown species of north american lion , jefferson warned explorers lewis and clark to keep an eye out for this mysterious predator . but jefferson 's box of bones did n't come from a lion . they came from an extinct giant sloth . prehistoric ground sloths first appeared around 35 million years ago . dozens of species lived across north , central and south america , alongside other ancient creatures like mastodons and giant armadillos . some ground sloths , like the megalonychid , were cat-sized , but many were massive . jefferson 's sloth , megalonyx , weighed about a ton , and that was small compared to megatherium , which could reach six metric tons , as much as an elephant . they ambled through the forests and savannas using their strong arms and sharp claws to uproot plants and climb trees , grazing on grasses , leaves , and prehistoric avocados . in fact , we might not have avocados today if not for the giant sloths . smaller animals could n't swallow the avocado 's huge seed , but the sloths could , and they spread avocado trees far and wide . ground sloths flourished for millions of years , but around 10,000 years ago , they started disappearing along with the western hemisphere 's other giant mammals . researchers think that ground sloths could have been pushed out by an oncoming ice age , or competition with other species , maybe humans , who arrived in the region around the time most of the sloths went extinct . some of the smaller sloths did survive and migrated to the treetops . today , there are six species left living in the rainforest canopies of central and south america . hanging out in the trees is a good way to avoid predators , and there are plenty of leaves to eat . but this diet has its drawbacks . animals extract energy from food and use that energy to move around , maintain their body temperature , keep their organs working , and all the other activities necessary for survival . but leaves do n't contain much energy , and that which they do have is tough to extract . most herbivores supplement a leafy diet with higher energy foods like fruit and seeds . but sloths , especially three-toed sloths , rely on leaves almost exclusively . they 've evolved finely tuned strategies for coping with this restricted diet . first , they extract as much energy from their food as possible . sloths have a multi-chambered stomach that takes up a third of their body , and depending on the species , they can spend five to seven days , or even weeks , processing a meal . the other piece of the puzzle is to use as little energy as possible . one way sloths do this is , of course , by not moving very much . they spend most of their time eating , resting , or sleeping . they descend from the canopy just once a week for a bathroom break . when sloths do move , it 's not very fast . it would take a sloth about five minutes to cross an average neighborhood street . this unhurried approach to life means that sloths do n't need very much muscle . in fact , they have about 30 % less muscle mass than other animals their size . sloths also use less energy to keep themselves warm because their body temperature can fluctuate by about five degrees celsius , less than a cold-blooded reptile , but more than most mammals . these physical and behavioral adaptations minimize the sloth 's energy expenditure , or metabolic rate . three-toed sloths have the slowest metabolism of any mammal . the giant panda is second slowest , and two-toed sloths come in third . moving slowly has allowed sloths to thrive in their treetop habitat . but it 's also made the sloths themselves a great habitat for other organisms , including algae , which provides a little extra camouflage , and maybe even a snack . sloths may not be giant anymore , but that does n't make them any less remarkable .
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in 1796 , thomas jefferson received a box of bones he could n't identify . a long , sharp claw reminded him of a lion , but the arm bones suggested a larger animal , one about three meters long .
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thomas jefferson received a box of giant ground sloth bones he couldn ’ t identify . he initially thought they were from a :
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hi there , i ’ m john green , this is crash course : world history and today we ’ re going to talk about islam , which like christianity and judaism grew up on the east coast of the mediterranean but unlike christianity and judaism is not terribly well understood in the west . for instance , you probably know what this is and what this is , you probably don ’ t know what that is . google it . mr. green mr. green why do you think people know so little about islamic history ? did you just ask an interesting non-annoying question , me from the past ? i think we don ’ t know about early islamic history because we don ’ t learn about it , me from the past , because we don ’ t learn about it , because we ’ re taught that our history is the story of christianity in europe , when in fact our history is the story of people on the planet , so let ’ s try to learn something today . [ theme music ] so in less than 200 years islam went from not existing to being the religious and political organizing principal of one of the largest empires in the world . and that story begins in the 7th century ce when the angel gabriel appeared to muhammad , a 40-ish guy who made his living as a caravan trader and told him to begin reciting the word of god . initially , this freaked muhammad out , as , you know , it would—but then his wife and a couple of other people encouraged him and slowly he came to accept the mantle as prophet . a few things to know about the world islam entered : first , muhammad ’ s society was intensely tribal . he was a member of the quraysh tribe , living in mecca and tribal ties were extremely important . also , at the time , the arabian peninsula was like this crazy religious melting pot . like most tribal arabs worshipped gods very similar to the mesopotamian gods you ’ ll remember from episode 3 . and by the time of muhammad , cult statutes of many of those gods had been collected in his hometown of mecca in this temple-like structure called the kaaba . but arabia was also a home for monotheisms like christianity and judaism , even a bit of zoroastrianism . so the message that there was only god wouldn ’ t have been like as surprising to muhammad as it was , for instance , to abraham . also , and this will become very important , the northern part of arabia was sandwiched between the byzantine empire and the persian sassanian empire—and you ’ ll remember , those guys were always fighting . they were like snowboarders and skiers , or like the westboro baptist church and everyone else . at its core , islam is what we call a radical reforming religion—just like jesus and moses sought to restore abrahamic monotheism after what they perceived as straying , so too did muhammad . muslims believe that god sent muhammad as the final prophet to bring people back to the one true religion , which involves the worship of , and submission to , a single and all-powerful god . the quran also acknowledges abraham and moses and jesus among others as prophets , but it ’ s very different from the hebrew and christian bibles : for one thing it ’ s much less narrative , but also its the written record of the revelations muhammad received—which means its not written from the point of view of people , it is seen as the actual word of god . the quran is a really broad-ranging text , but it returns again and again to a couple themes . one is strict monotheism and the other is the importance of taking care of those less fortunate than you . the quran , says of the good person spends his substance—however much he himself may cherish it—upon his near of kin , and the orphans , and the needy , and the wayfarer , and the beggars , and for the freeing of human beings from bondage . these revelations also radically increased the rights of women and orphans , which was one of the reasons why mohammad ’ s tribal leaders weren ’ t that psyched about them . to talk more about islamic faith and practice , let ’ s go to the thought bubble . the five pillars of islam are the basic acts considered obligatory , at least by sunni muslims . first is the shahada or the profession of the faith : there is no god but god and muhammad is god ’ s prophet , which is sometimes translated as “ there is no god but allah and muhammad is allah ’ s prophet ” , which tries to make muslims sound other and ignores the fact that the arabic word for god—whether you are christian or jewish or muslim—is allah . second , salat , or ritual prayer five times a day—at dawn , noon , afternoon , sunset , and late evening—which are obligatory unless you haven ’ t hit puberty , are too sick , or are menstruating . keep it pg , thought bubble . third , sawm , the month-long fast during the month of ramadan , in which muslims do not eat or drink or smoke cigarettes during daylight hours . since ramadan is a lunar-calendar month , it moves around the seasons , and obviously it ’ s most fun during the winter , when days are shorter , and least fun during the summer , when days are both long and hot . fourth is zakat , or almsgiving , in which non-poor muslims are required to give a percentage of their income to the poor , and lastly hajj , the pilgrimage to mecca that muslims must try to fulfill at least once in their lives , provided they are healthy and have enough money . and there ’ s also more to understanding islam than just knowing the quran . like judaism with its talmud , and christianity with its lives of saints and writings of church fathers , islam has supplementary sacred texts , chief among which is the hadith , a collection of sayings and stories about the prophet . thanks thought bubble . oh , it ’ s time for the open letter ? magic . an open letter to the 72 virgins . oh , but first let ’ s check what ’ s in the secret compartment . huh , it ’ s andre the giant . did you know that andre the giant died a virgin- is a fact that i made up ? dear 72 virgins , hey there , it ’ s me , john green . did you know that not all hadiths were created equal ? some sayings of the prophet are really well sourced . like for instance , a good friend or a relative heard the prophet say something and then it ended up as a hadith . but some hadiths are terribly sourced like , not to be irreverent , but some of it is like middle school gossip ; like rachel told rebekah that her sister ’ s brother ’ s friend kissed justin bieber on the face . and the vast majority of muslims don ’ t treat terribly sourced hadiths as scripture . and the idea that you go to heaven and get 72 virgins is not in the quran ; it ’ s in a terribly sourced hadith so it is my great regret to inform you , 72 virgins , that in the eyes of almost all muslims you do not exist . best wishes , john green one more thing about islam : like christianity and judaism , it has a body of law . you might have heard of it - it ’ s called sharia . although we tend to think of sharia as this single set of laws that all muslims follow , that ’ s ridiculous ; there are numerous competing interpretations of sharia , just as there are within any legal tradition . so people who embraced this worldview were called muslims , because they submitted to the will of god , and they became part of the umma , or community of believers . this would be a good moment for an uma thurman joke , but sadly she is no longer famous . i ’ m sorry if you ’ re watching this , uma thurman . being part of the umma trumped all other ties , including tribal ties , which got muhammad into some trouble and brings us , at last , back to history . so as muhammad ’ s following in mecca grew , the umma aroused the suspicion of the most powerful tribe , the quraysh . and it didn ’ t matter that muhammad himself was born into the quraysh tribe because he wouldn ’ t shut up about how there was only one god , which was really bad news to the quraysh tribe because they managed the pilgrimage trade in mecca , and if all those gods were false , it would be a disaster economically . —although come to think of it , in the end the meccan pilgrimage business turned out just fine . so the quraysh forced muhammad and his followers out of mecca in 622 ce , and they headed to yithrab , also known as medina . this journey , also know as the hijra , is so important that it marks year 0 in the islamic calendar . in medina , muhammad severed the religion ’ s ties to judaism , turning the focus of prayer away from jerusalem to mecca . also in medina , the islamic community started to look a lot more like a small empire than like a church . like , jesus never had a country to run . but muhammad did almost from the beginning . and in addition to being an important prophet , he was a good general and in 630 , the islamic community took back mecca . they destroyed the idols in the kabaa , and soon islam was as powerful a political force in the region as it was a religious one . and it ’ s because the political and religious coexisted from the beginning , that there ’ s no separate tradition of civic and religious law like there is in christianity and judaism . very different from judaism and even from christianity—which you ’ ll remember debated very different from judaism and even from christianity—which you ’ ll remember debated for generations whether to be inclusive . —and more importantly than separating islam from other monotheisms , that really separated islam from the tribalism in arabia . so then when muhammad died in 632 ce , there wasn ’ t a religious vacuum left behind : muhammad was the final prophet , the revelation of the quran would continue to guide the umma throughout their lives . but the community did need a political leader , a caliph . and the first caliph was abu bakr , muhammad ’ s father-in-law , who was not without his opponents : many people wanted ali , muhammad ’ s son-in-law , to lead the community . and although he did become the fourth caliph , that initial disagreement — to radically oversimplify because we only have ten minutes — began the divide between the two of the major sects of islam : suuni and shi ’ a . and even today , sunnis muslims believe abu bakr was rightly elected the first caliph and shi ’ a muslims believe it should ’ ve been ali . to sunnis , the first four caliphs—abu bakr , umar , uthman , and ali— are known as the rightly guided caliphs , and many of the conservative movements in the islamic world today are all about trying to restore the islamic world to those glory days , which—like most glory days—were not unambiguously glorious . abu bakr stabilized the community after muhammad ’ s death , and began the process of recording the quran in writing , and started the military campaigns against the byzantine and sassanian empires that within 116 years would allow the islamic empire to go from this to this . his successor umar was both an uncommonly good general and a brilliant administrator but like so many other great men , he proved terrible at avoiding assassination . which led to the caliphate of uthman , who standardized the quran and continued both his predecessor ’ s tradition of conquest and his predecessor ’ s tradition of getting assassinated . then ali finally got his turn at caliph , but his ascension was very controversial , and it ultimately led to a civil war . which eventually led to the emergence of uthman ’ s tribe , the umayyads , as the dynasty ruling over an ever-expanding islamic empire for more than a hundred years . it ’ s common to hear that in these early years islam quote spread by the sword , and that ’ s partly true , unless you are — wait for it — the mongols . actually , as usual , the truth is more complicated : many people , including the mongols but also including lots of people in central and east asia , embraced islam without any military campaigns . and in fact , the quran says that religion must not be an act of compulsion , but this much is true : the early islamic empire was really good at winning wars . and situated as they were between two very wealthy empires—the byzantines and the sassanians—there was plenty to fight for . first to fall was the sassanians , the last non-muslim successor to the persian empire . they were relatively easy pickings because they ’ d been fighting the byzantines for like 300 years and were super tired . also they ’ d been recently struck by plague . plague , man , i ’ m telling you ; it ’ s like the red tortoise shell of history . but in those early days they did pry away some valuable territory like egypt and the holy land and eventually they got into spain . where various muslim dynasties would entrench themselves until being expelled in 1492 . but as a good as they were at making war , it ’ s still tempting to chalk up the arabs ’ success to , you know , the will of god . and certainly a lot of the people they conquered felt that way . wars in this part of the world didn ’ t just pit people against each other , they also pitted their gods against each other . so while the islamic empire didn ’ t require its subjects to convert to islam , their stunning successes certainly convinced a lot of people that this monotheism thing was legit . once again , john green proving super hip to the slang of today ’ s young ’ ns . also , you paid lower taxes if you converted , and just as taxes on cigarettes lead to people not wanting to smoke , taxes on worshiping your idols lead to people not wanting to worship them anymore . so in a period of time that was , historically speaking , both remarkably recent and remarkably short , a small group of people from an area of the world with no natural resources managed to create one of the great empires of the world and also one of its great religions . and that very fact may be why people of western european descent remain largely ignorant about this period . not only were the muslims great conquerors , they spawned an explosion of trade and learning that lasted hundreds of years . they saved many of the classical texts that form the basis of the “ western canon ” while europe was ignoring them and they paved the way for the renaissance . while it ’ s important to remember that much of the world between spain and the indus river wasn ’ t arabized , most of it was so thoroughly islamized that these days we can ’ t think of the world we now call the middle east without thinking of it as islamic . perhaps the greatest testimony to islam ’ s power to organize peoples lives and their communities is that , in egypt , 5 times a day millions of people turn away from the pyramids and toward mecca . egypt , birthplace to one of the longest continuous cultures the world has ever known , is now the largest arab country in the world . next week we ’ ll talk about the dark ages . spoiler alert : they were darkest in the evening . thanks for watching and we ’ ll see you next time . crash course is produced and directed by stan muller , our script supervisor is danica johnson . the show is written by my high school history teacher raoul meyer and myself and our graphics team is thought bubble . last week ’ s phrase of the week was “ they might be giants ” . if you want to guess this week ’ s phrase of the week or suggest future ones you can do so in comments where you can also ask questions about today ’ s video that our team of historians will endeavor to answer . thank you so much for watching and as they say in my hometown , don ’ t forget to be awesome .
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perhaps the greatest testimony to islam ’ s power to organize peoples lives and their communities is that , in egypt , 5 times a day millions of people turn away from the pyramids and toward mecca . egypt , birthplace to one of the longest continuous cultures the world has ever known , is now the largest arab country in the world . next week we ’ ll talk about the dark ages .
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which of the following is the largest arab country in the world ?
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in 1997 , in a game between france and brazil , a young brazilian player named roberto carlos set up for a 35 meter free kick . with no direct line to the goal , carlos decided to attempt the seemingly impossible . his kick sent the ball flying wide of the players , but just before going out of bounds , it hooked to the left and soared into the goal . according to newton 's first law of motion , an object will move in the same direction and velocity until a force is applied on it . when carlos kicked the ball , he gave it direction and velocity , but what force made the ball swerve and score one of the most magnificent goals in the history of the sport ? the trick was in the spin . carlos placed his kick at the lower right corner of the ball , sending it high and to the right , but also rotating around its axis . the ball started its flight in an apparently direct route , with air flowing on both sides and slowing it down . on one side , the air moved in the opposite direction to the ball 's spin , causing increased pressure , while on the other side , the air moved in the same direction as the spin , creating an area of lower pressure . that difference made the ball curve towards the lower pressure zone . this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful . but curving the ball with the precision needed to both bend around the wall and back into the goal is difficult . too high and it soars over the goal . too low and it hits the ground before curving . too wide and it never reaches the goal . not wide enough and the defenders intercept it . too slow and it hooks too early , or not at all . too fast and it hooks too late . the same physics make it possible to score another apparently impossible goal , an unassisted corner kick . the magnus effect was first documented by sir isaac newton after he noticed it while playing a game of tennis back in 1670 . it also applies to golf balls , frisbees and baseballs . in every case , the same thing happens . the ball 's spin creates a pressure differential in the surrounding air flow that curves it in the direction of the spin . and here 's a question . could you theoretically kick a ball hard enough to make it boomerang all the way around back to you ? sadly , no . even if the ball did n't disintegrate on impact , or hit any obstacles , as the air slowed it , the angle of its deflection would increase , causing it to spiral into smaller and smaller circles until finally stopping . and just to get that spiral , you 'd have to make the ball spin over 15 times faster than carlos 's immortal kick . so good luck with that .
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this phenomenon is called the magnus effect . this type of kick , often referred to as a banana kick , is attempted regularly , and it is one of the elements that makes the beautiful game beautiful . but curving the ball with the precision needed to both bend around the wall and back into the goal is difficult .
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can a banana kick be performed on the moon ?
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what keeps us healthy and happy as we go through life ? if you were going to invest now in your future best self , where would you put your time and your energy ? there was a recent survey of millennials asking them what their most important life goals were , and over 80 percent said that a major life goal for them was to get rich . and another 50 percent of those same young adults said that another major life goal was to become famous . ( laughter ) and we 're constantly told to lean in to work , to push harder and achieve more . we 're given the impression that these are the things that we need to go after in order to have a good life . pictures of entire lives , of the choices that people make and how those choices work out for them , those pictures are almost impossible to get . most of what we know about human life we know from asking people to remember the past , and as we know , hindsight is anything but 20/20 . we forget vast amounts of what happens to us in life , and sometimes memory is downright creative . but what if we could watch entire lives as they unfold through time ? what if we could study people from the time that they were teenagers all the way into old age to see what really keeps people happy and healthy ? we did that . the harvard study of adult development may be the longest study of adult life that 's ever been done . for 75 years , we 've tracked the lives of 724 men , year after year , asking about their work , their home lives , their health , and of course asking all along the way without knowing how their life stories were going to turn out . studies like this are exceedingly rare . almost all projects of this kind fall apart within a decade because too many people drop out of the study , or funding for the research dries up , or the researchers get distracted , or they die , and nobody moves the ball further down the field . but through a combination of luck and the persistence of several generations of researchers , this study has survived . about 60 of our original 724 men are still alive , still participating in the study , most of them in their 90s . and we are now beginning to study the more than 2,000 children of these men . and i 'm the fourth director of the study . since 1938 , we 've tracked the lives of two groups of men . the first group started in the study when they were sophomores at harvard college . they all finished college during world war ii , and then most went off to serve in the war . and the second group that we 've followed was a group of boys from boston 's poorest neighborhoods , boys who were chosen for the study specifically because they were from some of the most troubled and disadvantaged families in the boston of the 1930s . most lived in tenements , many without hot and cold running water . when they entered the study , all of these teenagers were interviewed . they were given medical exams . we went to their homes and we interviewed their parents . and then these teenagers grew up into adults who entered all walks of life . they became factory workers and lawyers and bricklayers and doctors , one president of the united states . some developed alcoholism . a few developed schizophrenia . some climbed the social ladder from the bottom all the way to the very top , and some made that journey in the opposite direction . the founders of this study would never in their wildest dreams have imagined that i would be standing here today , 75 years later , telling you that the study still continues . every two years , our patient and dedicated research staff calls up our men and asks them if we can send them yet one more set of questions about their lives . many of the inner city boston men ask us , `` why do you keep wanting to study me ? my life just is n't that interesting . '' the harvard men never ask that question . ( laughter ) to get the clearest picture of these lives , we do n't just send them questionnaires . we interview them in their living rooms . we get their medical records from their doctors . we draw their blood , we scan their brains , we talk to their children . we videotape them talking with their wives about their deepest concerns . and when , about a decade ago , we finally asked the wives if they would join us as members of the study , many of the women said , `` you know , it 's about time . '' ( laughter ) so what have we learned ? what are the lessons that come from the tens of thousands of pages of information that we 've generated on these lives ? well , the lessons are n't about wealth or fame or working harder and harder . the clearest message that we get from this 75-year study is this : good relationships keep us happier and healthier . period . we 've learned three big lessons about relationships . the first is that social connections are really good for us , and that loneliness kills . it turns out that people who are more socially connected to family , to friends , to community , are happier , they 're physically healthier , and they live longer than people who are less well connected . and the experience of loneliness turns out to be toxic . people who are more isolated than they want to be from others find that they are less happy , their health declines earlier in midlife , their brain functioning declines sooner and they live shorter lives than people who are not lonely . and the sad fact is that at any given time , more than one in five americans will report that they 're lonely . and we know that you can be lonely in a crowd and you can be lonely in a marriage , so the second big lesson that we learned is that it 's not just the number of friends you have , and it 's not whether or not you 're in a committed relationship , but it 's the quality of your close relationships that matters . it turns out that living in the midst of conflict is really bad for our health . high-conflict marriages , for example , without much affection , turn out to be very bad for our health , perhaps worse than getting divorced . and living in the midst of good , warm relationships is protective . once we had followed our men all the way into their 80s , we wanted to look back at them at midlife and to see if we could predict who was going to grow into a happy , healthy octogenarian and who was n't . and when we gathered together everything we knew about them at age 50 , it was n't their middle age cholesterol levels that predicted how they were going to grow old . it was how satisfied they were in their relationships . the people who were the most satisfied in their relationships at age 50 were the healthiest at age 80 . and good , close relationships seem to buffer us from some of the slings and arrows of getting old . our most happily partnered men and women reported , in their 80s , that on the days when they had more physical pain , their mood stayed just as happy . but the people who were in unhappy relationships , on the days when they reported more physical pain , it was magnified by more emotional pain . and the third big lesson that we learned about relationships and our health is that good relationships do n't just protect our bodies , they protect our brains . it turns out that being in a securely attached relationship to another person in your 80s is protective , that the people who are in relationships where they really feel they can count on the other person in times of need , those people 's memories stay sharper longer . and the people in relationships where they feel they really ca n't count on the other one , those are the people who experience earlier memory decline . and those good relationships , they do n't have to be smooth all the time . some of our octogenarian couples could bicker with each other day in and day out , but as long as they felt that they could really count on the other when the going got tough , those arguments did n't take a toll on their memories . so this message , that good , close relationships are good for our health and well-being , this is wisdom that 's as old as the hills . why is this so hard to get and so easy to ignore ? well , we 're human . what we 'd really like is a quick fix , something we can get that 'll make our lives good and keep them that way . relationships are messy and they 're complicated and the hard work of tending to family and friends , it 's not sexy or glamorous . it 's also lifelong . it never ends . the people in our 75-year study who were the happiest in retirement were the people who had actively worked to replace workmates with new playmates . just like the millennials in that recent survey , many of our men when they were starting out as young adults really believed that fame and wealth and high achievement were what they needed to go after to have a good life . but over and over , over these 75 years , our study has shown that the people who fared the best were the people who leaned in to relationships , with family , with friends , with community . so what about you ? let 's say you 're 25 , or you 're 40 , or you 're 60 . what might leaning in to relationships even look like ? well , the possibilities are practically endless . it might be something as simple as replacing screen time with people time or livening up a stale relationship by doing something new together , long walks or date nights , or reaching out to that family member who you have n't spoken to in years , because those all-too-common family feuds take a terrible toll on the people who hold the grudges . i 'd like to close with a quote from mark twain . more than a century ago , he was looking back on his life , and he wrote this : `` there is n't time , so brief is life , for bickerings , apologies , heartburnings , callings to account . there is only time for loving , and but an instant , so to speak , for that . '' the good life is built with good relationships . thank you . ( applause )
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if you were going to invest now in your future best self , where would you put your time and your energy ? there was a recent survey of millennials asking them what their most important life goals were , and over 80 percent said that a major life goal for them was to get rich . and another 50 percent of those same young adults said that another major life goal was to become famous .
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when millennials were polled about their life goals , what did 80 % of them claim to be a major life goal ?
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`` we are hurtling toward the day when climate change could be irreversible . '' `` rising sea levels already altering this nation ’ s coast . '' `` china ’ s capital is choking in its worst pollution of the year . '' `` 5 % of species will become extinct . '' `` sea levels rising , glaciers melting . '' okay . enough . i get it . it ’ s not like i don ’ t care about polar bears and melting ice caps . i ’ m a conservation scientist , so of course i care . i ’ ve dedicated my entire career to this . but over the years , one thing has become clear to me : we need to change the way we talk about climate change . this doom-and-gloom messaging just isn ’ t working ; we seem to want to tune it out . and this fear , this guilt , we know from psychology is not conducive to engagement . it 's rather the opposite . it makes people passive , because when i feel fearful or guilt-full , i will withdraw from the issue and try to think about something else that makes me feel better . and with a problem this overwhelming , it ’ s pretty easy to just turn away and kick the can down the road . somebody else can deal with it . so it ’ s no wonder that scientists and policymakers have been struggling with this issue too . so i like to say that climate change is the policy problem from hell . you almost could n't design a worse problem as a fit with our underlying psychology or the way our institutions make decisions . many americans continue to think of climate change as a distant problem : distant in time , that the impacts wo n't be felt for a generation or more ; and distant in space , that this is about polar bears or maybe some developing countries . again , it ’ s not like we don ’ t care about these things — it ’ s just such a complicated problem . but the thing is , we ’ ve faced enormous , scary climate issues before . remember the hole in the ozone layer ? as insurmountable as that seemed in the 1970s and ’ 80s , we were able to wrap our heads around that and take action . people got this very simple , easy to understand , concrete image of this protective layer around the earth , kind of like a roof , protecting us , in this case , from ultraviolet light , which by the way has the direct health consequence of potentially giving you skin cancer . okay , so now you 've got my attention . and so then they came up with this fabulous term , the “ ozone hole. ” terrible problem , great term . people also got a concrete image of how we even ended up with this problem . for decades , chlorofluorocarbons , or cfcs , were the main ingredient in a lot of products , like aerosol spray cans . then scientists discovered that cfcs were actually destroying the atmospheric ozone . people could look at their own hairspray and say , “ do i want to destroy the planet because of my hairspray ? i mean , god no. ” and so what 's interesting is that sales of hairspray and those kinds of products and underarm aerosols started dropping quite dramatically . people listened to scientists and took action . now scientists predict that the hole in the ozone layer will be healed around 2050 . that ’ s actually pretty amazing . and while stopping the use of one product is actually pretty easy , climate change caused by greenhouse gases … that ’ s much trickier . because the sources are more complicated , and for the most part , they ’ re totally invisible . right now , there is co2 pouring out of tailpipes , there is co2 pouring out of buildings , there is co2 pouring out of smokestacks , but you ca n't see it . the fundamental cause of this problem is largely invisible to most of us . i mean , if co2 was black , we would have dealt with this issue a long time ago . so co2 touches every part of our lives — our cars , the places we work , the food we eat . for now , let ’ s just focus on one thing : our energy use . how do we make that visible ? that was the initial goal of ucla ’ s engage project , one of the nation ’ s largest behavioral experiments in energy conservation . what we 're trying to do is to figure out how to frame information about electricity usage so that people save energy and conserve electricity . the idea is that electricity is relatively invisible to people . the research team outfitted part of a student housing complex with meters that tracked real-time usage of appliances and then sent them weekly reports . so you can see how much energy the stove used versus the dishwasher or the fridge . we realized , because of this project , the fridge was like the monster . so lucky for them , their landlord upgraded their fridge to an energy-efficient one . they also learned other energy-saving tips , like unplugging their dishwasher when not in use and air-drying their clothes during the summer months . and researchers , in turn , discovered where people were willing to cut back . the engage project wanted to know what types of messaging could motivate people to change their behavior . we wanted to see over time over a year and with repeated messages , how do people , behave ? how does that impact the consumer behavior ? and what we found is that it 's very different . some households were sent personalized emails with their energy bill about how they could save money ; others learned how their energy usage impacted the environment and children ’ s health . those who received messages about saving money did nothing . it was totally ineffective because electricity is relatively cheap . but emails sent that linked the amount of pollutants produced to rates of childhood asthma and cancer — well , those led to an 8 % drop in energy use , and 19 % in households with kids . now , in a separate study , researchers brought social competition into the mix . first , they hung posters around a dorm building to publicly showcase how students were really doing : red dots for energy wasters , green for those doing a good job , and a shiny gold star for those going above and beyond . this social pressure approach led to a 20 % reduction in energy use . this strategy was also used at paulina ’ s complex , and it definitely brought out her competitive streak . for me , the competition was what motivated me , because seeing your apartment number and telling you that you are doing at the average , but you are not the best , was like , why ? i ’ m doing everything you are telling me to do . i always wanted the gold star , because it was like , “ oh , my god , i want to be like the less consumption of energy in the whole building. ” and psychology studies have proved this . we are social creatures , and as individualistic as we can be , turns out we do care about how we compare to others . and yes , we do like to be the best . some people don ’ t want to say , oh , i 'm like the average . no , my usage is different and i want to be able to act on it . and people can act on it because with these meters , they can now see their exact impact . a company called opower is playing with this idea of social competition . they work with over 100 utility companies to provide personalized energy reports to millions of customers around the world . now consumers can not only see their energy use but how it compares to their neighbors ’ . like the ucla study found , this subtle social pressure encourages consumers to save energy . it ’ s been so effective that in 2016 , opower was able to generate the equivalent of two terawatt-hours of electricity savings . that ’ s enough to power every home in miami for more than a year . and they ’ re not alone . even large companies are tapping into behavioral science to move the dial . virgin atlantic airways gave a select group of pilots feedback on their fuel use . over the course of a year , they collectively saved over 6,800 tons of fuel by making some simple changes : adjusting their altitudes , routes , and speed reduced their carbon dioxide emissions by over 21,000 tons . these behavioral “ nudges ” do seem to be advancing how we as a society deal with some pretty complicated climate change issues , but it turns out we ’ re just getting started . there is no “ quick fix. ” we need people changing their companies , changing their business models , changing the products and services they provide . this is about broader-scale change . and part of this change includes embracing what makes us human . that it can ’ t just be a guilt trip about dying polar bears or driving around in gas guzzlers . we need to talk about our wins , as well — like how we ’ re making progress , really being aware of our energy use , and taking advantage of that competitive spirit we all have in order to really move us from a state of apathy to action . global warming is by far the biggest issue of our time . climate lab is a new series from vox and the university of california , and we ’ ll be exploring some surprising ways we can tackle this problem . if you want to learn more , head to climate.universityofcalifornia.edu .
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the fundamental cause of this problem is largely invisible to most of us . i mean , if co2 was black , we would have dealt with this issue a long time ago . so co2 touches every part of our lives — our cars , the places we work , the food we eat .
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why does the researcher believe that if co2 was black we would have dealt with it by now ?
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spray-painted subway cars , tagged bridges , mural-covered walls . graffiti pops up boldly throughout our cities . it can make statements about identity , art , empowerment , and politics , while simultaneously being associated with destruction . and , it turns out , it 's nothing new . graffiti , or the act of writing or scribbling on public property , has been around for thousands of years . and across that span of time , it 's raised the same questions we debate now : is it art ? is it vandalism ? in the 1st century bce , romans regularly inscribed messages on public walls , while oceans away , mayans were prolifically scratching drawings onto their surfaces . and it was n't always a subversive act . in pompeii , ordinary citizens regularly marked public walls with magic spells , prose about unrequited love , political campaign slogans , and even messages to champion their favorite gladiators . some , including the greek philosopher plutarch , pushed back , deeming graffiti ridiculous and pointless . but it was n't until the 5th century that the roots of the modern concept of vandalism were planted . at that time , a barbaric tribe known as the vandals swept through rome , pillaging and destroying the city . but it was n't until centuries later that the term vandalism was actually coined in an outcry against the defacing of art during the french revolution . and as graffiti became increasingly associated with deliberate rebellion and provocativeness , it took on its vandalist label . that 's part of the reason why , today , many graffiti artists stay underground . some assume alternate identities to avoid retribution , while others do so to establish comradery and make claim to territory . beginning with the tags of the 1960s , a novel overlap of celebrity and anonymity hit the streets of new york city and philadelphia . taggers used coded labels to trace their movements around cities while often alluding to their origins . and the very illegality of graffiti-making that forced it into the shadows also added to its intrigue and growing base of followers . the question of space and ownership is central to graffiti 's history . its contemporary evolution has gone hand in hand with counterculture scenes . while these movements raised their anti-establishment voices , graffiti artists likewise challenged established boundaries of public property . they reclaimed subway cars , billboards , and even once went so far as to paint an elephant in the city zoo . political movements , too , have used wall writing to visually spread their messages . during world war ii , both the nazi party and resistance groups covered walls with propaganda . and the berlin wall 's one-sided graffiti can be seen as a striking symbol of repression versus relatively unrestricted public access . as the counterculture movements associated with graffiti become mainstream , does graffiti , too , become accepted ? since the creation of so-called graffiti unions in the 1970s and the admission of select graffiti artists into art galleries a decade later , graffiti has straddled the line between being outside and inside the mainstream . and the appropriation of graffiti styles by marketers and typographers has made this definition even more unclear . the once unlikely partnerships of graffiti artists with traditional museums and brands , have brought these artists out of the underground and into the spotlight . although graffiti is linked to destruction , it 's also a medium of unrestricted artistic expression . today , the debate about the boundary between defacing and beautifying continues . meanwhile , graffiti artists challenge common consensus about the value of art and the degree to which any space can be owned . whether spraying , scrawling , or scratching , graffiti brings these questions of ownership , art , and acceptability to the surface .
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and as graffiti became increasingly associated with deliberate rebellion and provocativeness , it took on its vandalist label . that 's part of the reason why , today , many graffiti artists stay underground . some assume alternate identities to avoid retribution , while others do so to establish comradery and make claim to territory .
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why might some graffiti artists prefer to stay anonymous or underground ?
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translator : andrea mcdonough reviewer : bedirhan cinar the brain is the center of all of our thoughts , dreams , emotions , and memories . it 's what makes us who we are . but , there is still a lot that we do n't know about the brain . scientists have worked for years on trying to understand the human brain using techniques like eeg and fmri , where we scan the brain from the outside . but what if we could look inside the brains of humans and watch them as they work ? well , now we can by looking at the brains of people who are already going through surgery for clinical reasons , like curing epilepsy . epilepsy is a disease in which a faulty part of the brain starts working spontaneously for no apparent reason . it 's like an earthquake but inside your head . there 's no way to know in advance when a seizure will occur , so the patients are always at risk of unexpectedly losing control . there are drugs that treat epilepsy , but these do n't always work . some patients who do n't respond well to the drugs can undergo a different treatment where the faulty part in their brain , the part that starts the seizures , is surgically removed . the challenge is knowing which part to take out . how do you figure out which bit of the brain is faulty ? in order to find the exact location of the seizure onset , doctors embed electrodes directly into the patient 's brain around the suspected seizure center . the patient then stays in the hospital for a few days , waiting to have a seizure with the electrodes constantly recording the activity inside his or her brain . yes , now we want the patient to have a seizure so doctors can use the embedded electrodes to measure it and learn exactly where its origin was . after doctors are sure where the seizures come from in the brain , they can take the electrodes out . now they know what part of the brain they can remove in order to cure the patient . these brain electrodes can tell us more than just where the seizures happen . based on where the doctors place the electrodes in the brain , we can ask questions about what the brain does . sometimes we find one cell that starts bursting in activity every time the patient sees a particular picture , for example , a picture of marilyn monroe . see , every time the patient sees marilyn monroe , some specific cells fire in the brain . you can now know when the patient is thinking of marilyn monroe just by listening to these cells fire . when we find one or a few of these cells with each patient , we can then do all kinds of fancy things . for example , we can connect the recording electrode to a cursor on a screen and have the patient move the cursor left or right just by thinking of things . this can help people who lost the ability to move their hands , like people with spinal cord injuries or wounded soldiers , by having them control a prosthetic arm directly with their brain . our brain is a brilliant device which can make predictions about the future . for example , we can all know which word will appear at the end of this ... sentence . the brain can solve complicated problems , imagine the entire universe , and grasp concepts such as infinity or unicorns . the brain produces complex emotions like love or jealousy , it 's what makes us creative and curious , and it can even contemplate about itself . and the brain is the organ we use to study the brain . i think that the brain is the most beautiful organ in our body , but then i ask myself , `` which organ is making me think that ? ''
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the brain produces complex emotions like love or jealousy , it 's what makes us creative and curious , and it can even contemplate about itself . and the brain is the organ we use to study the brain . i think that the brain is the most beautiful organ in our body , but then i ask myself , `` which organ is making me think that ? ''
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do you think it 's right or wrong to use the newest technology to manipulate the brain in order to make everyone `` normal '' ?
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mysteries of vernacular : yankee , a new england resident or , more generally , a person who lives in or is from the united states . though the origin of yankee is uncertain , this all-american word most likely descended from the dutch moniker janke , a diminutive meaning little jan , or little john . in the 17th century , janke was the common nickname of dutch sailors , pirates in particular . a dutch pirate ship operating in the west indies was even called the yankee . over the years , yankee transformed from a pirate 's nickname into a general term of contempt . in 1758 , british general james wolfe used yankee as a pejorative term for the colonists under his supervision . but the insult was n't limited to soldiers . yankee quickly came to mean new englander , and by the 1780s , it was used to look down upon any american . during the revolution , colonists co-opted yankee and transformed it into a mark of national honor . the civil war , however , intensified the derisive definition when it was used by southerners to mock members of the union . today , it carries much less emotion , unless , of course , we 're talking about baseball .
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but the insult was n't limited to soldiers . yankee quickly came to mean new englander , and by the 1780s , it was used to look down upon any american . during the revolution , colonists co-opted yankee and transformed it into a mark of national honor .
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how did the offending use of yankee spread so quickly ?
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imagine you 're watching a runaway trolley barreling down the tracks straight towards five workers who ca n't escape . you happen to be standing next to a switch that will divert the trolley onto a second track . here 's the problem . that track has a worker on it , too , but just one . what do you do ? do you sacrifice one person to save five ? this is the trolley problem , a version of an ethical dilemma that philosopher philippa foot devised in 1967 . it 's popular because it forces us to think about how to choose when there are no good choices . do we pick the action with the best outcome or stick to a moral code that prohibits causing someone 's death ? in one survey , about 90 % of respondents said that it 's okay to flip the switch , letting one worker die to save five , and other studies , including a virtual reality simulation of the dilemma , have found similar results . these judgments are consistent with the philosophical principle of utilitarianism which argues that the morally correct decision is the one that maximizes well-being for the greatest number of people . the five lives outweigh one , even if achieving that outcome requires condemning someone to death . but people do n't always take the utilitarian view , which we can see by changing the trolley problem a bit . this time , you 're standing on a bridge over the track as the runaway trolley approaches . now there 's no second track , but there is a very large man on the bridge next to you . if you push him over , his body will stop the trolley , saving the five workers , but he 'll die . to utilitarians , the decision is exactly the same , lose one life to save five . but in this case , only about 10 % of people say that it 's ok to throw the man onto the tracks . our instincts tell us that deliberately causing someone 's death is different than allowing them to die as collateral damage . it just feels wrong for reasons that are hard to explain . this intersection between ethics and psychology is what 's so interesting about the trolley problem . the dilemma in its many variations reveal that what we think is right or wrong depends on factors other than a logical weighing of the pros and cons . for example , men are more likely than women to say it 's okay to push the man over the bridge . so are people who watch a comedy clip before doing the thought experiment . and in one virtual reality study , people were more willing to sacrifice men than women . researchers have studied the brain activity of people thinking through the classic and bridge versions . both scenarios activate areas of the brain involved in conscious decision-making and emotional responses . but in the bridge version , the emotional response is much stronger . so is activity in an area of the brain associated with processing internal conflict . why the difference ? one explanation is that pushing someone to their death feels more personal , activating an emotional aversion to killing another person , but we feel conflicted because we know it 's still the logical choice . trolleyology has been criticized by some philosophers and psychologists . they argue that it does n't reveal anything because its premise is so unrealistic that study participants do n't take it seriously . but new technology is making this kind of ethical analysis more important than ever . for example , driver-less cars may have to handle choices like causing a small accident to prevent a larger one . meanwhile , governments are researching autonomous military drones that could wind up making decisions of whether they 'll risk civilian casualties to attack a high-value target . if we want these actions to be ethical , we have to decide in advance how to value human life and judge the greater good . so researchers who study autonomous systems are collaborating with philosophers to address the complex problem of programming ethics into machines , which goes to show that even hypothetical dilemmas can wind up on a collision course with the real world .
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and in one virtual reality study , people were more willing to sacrifice men than women . researchers have studied the brain activity of people thinking through the classic and bridge versions . both scenarios activate areas of the brain involved in conscious decision-making and emotional responses .
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the classic and bridge versions of the problem both activate regions of the brain associated with :
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translator : andrea mcdonough reviewer : bedirhan cinar nearly every one of your science classes starts off with the scientific method . you recognize this ? ask a question , form a hypothesis , perform an experiment , collect data , draw conclusions , and then memorize a bunch of facts . this is really boring ! science is not a simple recipe in a cookbook , and learning is not memorizing facts for tests . yet , that is exactly what we do . we have to change this ! we have to look at how curiosity can ultimately benefit society by looking towards tomorrow , by going through a path from involvement to imagination to invention to innovation . and i 'd like to illustrate this by telling you the real story about how we discovered how geckos stick . first you need to get involved . you need to do curiosity-driven research yourself . we know that learning by being an active researcher is the best way to learn . imagine being in my lab and trying to discover how geckos stick . `` here is one of our subjects . this is a crested gecko . we are going to put the gecko on glass and we 're going to use a high speed camera that can capture up to 1,000 pictures in one second . there he goes . ok , record it . there 's the animal 's toes . '' `` so how do their feet stick and unstick so quickly ? '' how < i > do < /i > they do this ? we wonder , it 's kind of crazy , right ? it 's hard to believe . well it turns out , it was already known that the geckos have hairy toes , and those hairs are really small compared to your hair , and the little tips at the end are even smaller . well , my student tanya , who is not much older than some of you when she did this , a sophomore undergraduate , tried to figure this out , and we told that her that in order to do this , you 'd have to measure the force of a single hair . though we kind of only did this jokingly because these hairs are so small , we did n't think it was possible . but tanya did n't know that , and she went on to build the simplest , most beautiful measurement device ever . here it is : she took one of those tiny little hairs and put it on to a probe , and then she began pushing it into the metal beam . now she was very frustrated for months - it did n't stick . but she had figured out she had to orient it just like the gecko grabs on , and then it worked ! and there 's the little split ends grabbing the beam in that little window . and then she did something magical : for the first time ever , she measured the force of a single gecko hair that allowed her to discover a completely new way to stick to something , something no human has ever known before . they have hairy little toes , huge numbers of hairs , and each hair has the worst case of split ends possible , 100 to 1,000 nano-tips that an animal has on one hair , and 2 billion total , and they do n't stick by glue , or by suction , or by velcro . it was discovered that they stick by inter-molecular forces alone , by van der waals forces , and you 'll learn this in chemistry and physics , if you take it . it 's unbelievable ! it 's a whole new way of thinking about making an adhesive ! well , this is n't the end of the story , there are still mysteries . why are the gecko 's feet looking like this ? they have bizarre toes and we do n't know why . if you go into a museum and look at each gecko species , you see they have all different hairs , different lengths , and thicknesses , and patterns . why ? i do n't know ! but you should come to berkeley and help me figure this out . it 's just about right , so , apply . but it 's a mystery . there is even more stuff that is unknown . this tarantula also has hairs and can stick this way , too , but recently it was found that they also can secrete silk from their feet , not just their behind , like you know they do . and even more recently , my graduate student ann showed that all spiders can secrete glue , and we know nothing about this glue except it was around way before this guy , millions of years before . so do n't stop at the discovery , next imagine the possible uses for society . here is the first human supported by a gecko-inspired adhesive . this is my former graduate student , kellar autumn , who is professor at lewis and clark , offering his second born child for the test . and she 's a very good sport about it ! now imagine all the things you could make from this , not only adhesives , but products in sports , and biomedicine , technology , robotics , toys , automotive , fashion , clothes , and yes , even hair pieces . i swear to you , we got a call from michael jackson 's hairdresser about hair pieces before he passed away . who would have guessed from studying geckos ? ! ? next , invent a game-changing technology , device , or product . like my engineering colleague at berkeley , ron fearing , did when he made one of the first synthetic , self-cleaning dry adhesives after the simplest version that you see in animals . believe it or not , right now , because of this work , you can make your own synthetic gecko nano-tape by nano-molding with just a few parts , and here 's the recipe that we can give you . it 's been incredible since we made this discovery of all the papers and the work and the different ways to make it , it 's emerging into a billion dollar industry . and who would have imagined that it started because we were curious about how geckos can run up walls . next you need to innovate , create a business that ultimately benefits society . did you know that there are 6 million people per year that have chronic wounds , 2 million develop an infection , and infections account for 100,000 hospital deaths ? imagine if you could build a company that could produce a gecko-inspired band-aid that would remove the pain and suffering . just a simple invention . if you look at the last three great earthquakes , over 700,000 people were trapped and lost their lives . imagine the company that made a search-and-rescue robot inspired from a gecko that could move anywhere and quickly find individuals that have been trapped , that sometimes survive as long as two weeks . there is a gecko-inspired robot , stickybot , from the stanford group , that can grab on to any surface . now we ran our own , for ted , mini bio-inspired design challenge to get you to think about these kinds of products . we have a winner . here 's the winner . the winner came up with this design called stickyseat . really clever . it 's a seat that is not only comfortable , but it aids a seat belt , if you were in an accident , in terms of keeping your seat and moving . this is brilliant ! we did n't think about this , although we might think about patenting it now , but there is a winner for this , and the winner , and you ca n't , you ca n't make up something like this , the winner 's name is harry . where 's harry ? harry , come here , we have a prize for you . where 's harry ? harry ! come here ! we have a crested gecko for you that has very cool hairs on it . congratulations for harry ! excellent job ! so do n't worry , if you missed out on this , it 's ok because we are doing another design challenge working with the san diego zoo . they 're developing a best ideas project in san diego , but it 's going to go national . and i 'll leave you with a fact that you should keep being curious because curiosity-based research leads to the biggest benefits , as we showed you in our example , and you < i > can < /i > make a difference < i > now < /i > because like tanya , you do n't know what ca n't be done . thank you .
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we know that learning by being an active researcher is the best way to learn . imagine being in my lab and trying to discover how geckos stick . `` here is one of our subjects . this is a crested gecko .
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what did anne , one of robert full 's graduate students , discover about spiders ?
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they say that if walls could talk , each building would have a story to tell , but few would tell so many fascinating stories in so many different voices as the hagia sophia , or holy wisdom . perched at the crossroads of continents and cultures , it has seen massive changes from the name of the city where it stands , to its own structure and purpose . and today , the elements from each era stand ready to tell their tales to any visitor who will listen . even before you arrive at the hagia sophia , the ancient fortifications hint at the strategic importance of the surrounding city , founded as byzantium by greek colonists in 657 bce . and successfully renamed as augusta antonia , new rome and constantinople as it was conquered , reconquered , destroyed and rebuilt by various greek , persian and roman rulers over the following centuries . and it was within these walls that the first megale ekklesia , or great church , was built in the fourth century . though it was soon burned to the ground in riots , it established the location for the region 's main religious structure for centuries to come . near the entrance , the marble stones with reliefs are the last reminders of the second church . built in 415 ce , it was destroyed during the nika riots of 532 when angry crowds at a chariot race nearly overthrew the emperor , justinian the first . having barely managed to retain power , he resolved to rebuild the church on a grander scale , and five years later , the edifice you see before you was completed . as you step inside , the stones of the foundation and walls murmur tales from their homelands of egypt and syria , while columns taken from the temple of artemis recall a more ancient past . runic inscriptions carved by the vikings of the emperor 's elite guard carry the lore of distant northern lands . but your attention is caught by the grand dome , representing the heavens . reaching over 50 meters high and over 30 meters in diameter and ringed by windows around its base , the golden dome appears suspended from heaven , light reflecting through its interior . beneath its grandiose symbolism , the sturdy reinforcing corinthian columns , brought from lebanon after the original dome was partially destroyed by an earthquake in 558 ce , quietly remind you of its fragility and the engineering skills such a marvel requires . if a picture is worth a thousand words , the mosaics from the next several centuries have the most to say not only about their biblical themes , but also the byzantine emperors who commissioned them , often depicted along with christ . but beneath their loud and clear voices , one hears the haunting echoes of the damaged and missing mosaics and icons , desecrated and looted during the latin occupation in the fourth crusade . within the floor , the tomb inscription of enrico dandolo , the venetian ruler who commanded the campaign , is a stark reminder of those 57 years that hagia sophia spent as a roman catholic church before returning to its orthodox roots upon the byzantine reconquest . but it would not remain a church for long . weakened by the crusades , constantinople fell to the ottomans in 1453 and would be known as istanbul thereafter . after allowing his soldiers three days of pillage , sultan mehmed the second entered the building . though heavily damaged , its grandeur was not lost on the young sultan who immediately rededicated it to allah , proclaiming that it would be the new imperial mosque . the four minarets built over the next century are the most obvious sign of this era , serving as architectural supports in addition to their religious purpose . but there are many others . ornate candle holders relate suleiman 's conquest of hungary , while giant caligraphy discs hung from the ceiling remind visitors for the first four caliphs who followed muhammad . though the building you see today still looks like a mosque , it is now a museum , a decision made in 1935 by kemal ataturk , the modernizing first president of turkey following the ottoman empire 's collapse . it was this secularization that allowed for removal of the carpets hiding the marble floor decorations and the plaster covering the christian mosaics . ongoing restoration work has allowed the multiplicity of voices in hagia sophia 's long history to be heard again after centuries of silence . but conflict remains . hidden mosaics cry out from beneath islamic calligraphy , valuable pieces of history that can not be uncovered without destroying others . meanwhile , calls sound from both muslim and christian communities to return the building to its former religious purposes . the story of the divine wisdom may be far from over , but one can only hope that the many voices residing there will be able to tell their part for years to come .
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it was this secularization that allowed for removal of the carpets hiding the marble floor decorations and the plaster covering the christian mosaics . ongoing restoration work has allowed the multiplicity of voices in hagia sophia 's long history to be heard again after centuries of silence . but conflict remains .
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which of the following statements about the hagia sophia is not true ?
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they call me the tornado chaser . when the wind is up and conditions are right , i get in my car and follow violent storms . `` crazy , '' you say ? perhaps , but really i chase these sky beasts to learn about them . i want to share with you what i know . tornadoes are rapidly rotating columns of air that form inside storms that connect with the ground via a funnel of cloud . when that happens , they tear across the earth , posing a huge threat to life and property . because of this , there 's a great deal of research into these phenomena , but the truth is , there 's still a lot we do n't know about how tornadoes form . the conditions that may give rise to one tornado wo n't necessarily cause another . but we have learned a lot since people first started recording tornadoes , like how to recognize the signs when one is brewing in the sky . are you coming along for the ride ? tornadoes begin with a thunderstorm but not just any thunderstorm . these are especially powerful , towering thunderstorms called supercells . reaching up to over 50,000 feet , they bring high force winds , giant hailstones , sometimes flooding and great flashes of lightning , too . these are the kinds of storms that breed tornadoes , but only if there are also very specific conditions in place , clues that we can measure and look out for when we 're trying to forecast a storm . rising air is the first ingredient needed for a tornado to develop . any storm is formed when condensation occurs , the byproducts of the clouds . condensation releases heat , and heat becomes the energy that drives huge upward drafts of air . the more condensation and the bigger the storm clouds grow , the more powerful those updrafts become . in supercells , this rising airmass is particularly strong . as the air climbs , it can change direction and start to move more quickly . finally , at the storm 's base , if there is a lot of moisture , a huge cloud base develops , giving the tornado something to feed off later , if it gets that far . when all these things are in place , a vortex can develop enclosed by the storm , and forming a wide , tall tube of spinning air that then gets pulled upwards . we call this a mesocyclone . outside , cool , dry , sinking air starts to wrap around the back of this mesocyclone , forming what 's known as a rear flank downdraft . this unusual scenario creates a stark temperature difference between the air inside the mesocyclone , and the air outside , building up a level of instability that allows a tornado to thrive . then , the mesocyclone 's lower part becomes tighter , increasing the speed of the wind . if , and that 's a big if , this funnel of air moves down into that large , moist cloud base at the bottom of the parent storm , it sucks it in and turns it into a rotating wall of cloud , forming a link between the storm that created it and the earth . the second that tube of spinning cloud touches the ground , it becomes a tornado . most are small and short-lived , producing winds of 65-110 miles per hour , but others can last for over an hour , producing 200 mile per hour winds . they are beautiful but terrifying , especially if you or your town is in its path . in that case , no one , not even tornado chasers like me , enjoy watching thing unfold . just like everything , however , tornadoes do come to an end . when the temperature difference disappears and conditions grow more stable , or the moisture in the air dries up , the once fierce parent storm loses momentum and draws its tornado back inside . even so , meteorologists and storm chasers like me will remain on the lookout , watching , always watching to see if the storm releases its long rope again .
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when the temperature difference disappears and conditions grow more stable , or the moisture in the air dries up , the once fierce parent storm loses momentum and draws its tornado back inside . even so , meteorologists and storm chasers like me will remain on the lookout , watching , always watching to see if the storm releases its long rope again .
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what are some important reasons why you should not “ storm chase ? ”
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so this is mercury . it ’ s a liquid metal , it is one of the , well , one liquid metal at this temperature . there are a couple of liquid metals in a little bit more exotic places in the world like spain or perhaps africa . but mercury is the chemical formula hg , the best way to remember the formula for mercury is like h.g . wells . hg , mercury , comes out of a well . mercury is one of the few elements that is liquid at room temperature or is the only metal that is liquid at room temperature unless you live in a very hot country , it is also very dense . and it has been known again since very early times . mercury is very poisonous . it is a really fantastic liquid . it was really used for making scientific instruments like barometers and thermometers , you know , and it ’ s really quite a beautiful metal . i really love it , when i was in school we used to but it on the bench and play football with it . you know , lots of people don ’ t like us to do that anymore , but what i will do is to pour a little bit of the liquid metal into this beaker so we can see the properties and you can see that it is really nice . flows , just like a liquid , it forms really quite nice balls . and you can see the really quite high meniscus forming around the mercury . it can get into the human body particularly in the brain where it gives signs of madness . it used to be used in the uk for making hats . i am not quite sure what they did with mercury to make hats , but this is where the expression , “ mad as a hatter ” came from , because the people making hats breathed in mercury vapour and this caused them to show signs of madness . so here we can slosh it around a little bit but we have got to be very careful that we don ’ t slosh it too much because it is extremely dense and heavy and it is very , very easy to go through the middle or the bottom of the glass bottle itself . tell me why you aren ’ t touching it with your hands ? well mercury it is associated with toxicity especially for the salts , so you know we like to try and minimise the contact with the mercury and the mercury salts as much as possible really , just so that we could be very careful with our health and safety . there was a tragic case in japan in the 1950s , when mercury got into the sea from chemical emissions from factories , and the organisms on the bottom of the sea turned them into , the mercury metal , into a compound that could be absorbed by the fish , particularly the shellfish , and then the fishermen and the people living the round this minamata bay , starting eating these things got large amounts of mercury in their brain . and i can ’ t remember the number but several thousand people got very ill and many of them died , so mercury in the environment is quite a serious problem . it is also an interesting point that mercury has been used for making chlorine by putting electric current thought solutions of salt and it is gradually being replaced . but unlike chemicals you can ’ t get rid of an element , so if you have mercury you can ’ t burn it or destroy it in any way . and so , there are problems now , what to do with the mercury that people no longer want . but it is a really beautiful element , really fantastic . it is used very often in electric chemistry , because you can form very , very good electrical contact with mercury . and in fact , many people that may have old telephones or old bells , you know the door bells which we have on our front door , inside the ‘ bing-bong ’ , is a mercury-activated switch which turns on the magnet and off the magnet very , very quickly . it is really beautiful . mercury has an interesting property that it will very easily form alloys which are called amalgams . my teeth and probably many of your teeth are filled with so called silver amalgam which is a mixture of mercury and silver which when it is freshly mixed is like a paste . but when the dentist pushes it into your tooth it then hardens and , all being well , it does not come out or at least does not come out for a number of years . but amalgams are not very strong . and many years ago when i worked at another university , mercury was being stolen from the university , from the chemistry department and nobody knew who was stealing it . until one day the window cleaner was walking out of the building and the bottom fell out of his bucket , because he had been stealing mercury by pouring it into the bottom…pouring it into his bucket and hiding it below the dirty water . and the mercury started to amalgamate with the metal of the bucket , it was a metal bucket , and eventually , the bucket could no longer hold the weight of the mercury and it suddenly fell out and the mercury all came off .
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it used to be used in the uk for making hats . i am not quite sure what they did with mercury to make hats , but this is where the expression , “ mad as a hatter ” came from , because the people making hats breathed in mercury vapour and this caused them to show signs of madness . so here we can slosh it around a little bit but we have got to be very careful that we don ’ t slosh it too much because it is extremely dense and heavy and it is very , very easy to go through the middle or the bottom of the glass bottle itself .
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what is the chemical reason for the mad hatter ’ s behavior in `` alice in wonderland , '' which explains the phrase `` mad as a hatter ? ''
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translator : andrea mcdonough reviewer : jessica ruby how do you get from point a to point b ? why not spice it up with homemade special effects ? a film is simply a series of images played in sequence to create the illusion of motion . if you manipulate those images , crazy things can happen . we used a tablet and one of the many stop motion apps out there . how do you get from point a to point b ? we started off by taking a bunch of pictures of celeste in place . then , just like stop motion animation , the character is moved just a bit before the next picture is taken , which , in this case , creates a sliding effect . here we use the oldest trick in the book . by alternating between photos of celeste on-screen and off-screen , we 've made her childhood dream of teleportation a reality . with a little creativity , there are a million ways you can used homemade special effects to make something as simple as getting from point a to point b much more fun . if you 're at a loss for ideas , try finding inspiration in your surroundings , like the refrigerator and your coat rack . you can even try incorporating everyday objects from around your house , like , say , umbrellas or binder clips . wherever there is an object , there is an opportunity to make it come to life . when humans are used in stop motion animation , that 's called pixilation , a term coined in the mid-twentieth century , well before the word pixel was a part of our vocabulary . but these sorts of special effects are as old as the art of film making , and thanks to today 's technologies , can be reproduced in your very own kitchen . moving an object from point a to point b is a fundamental principle of animation . to learn more about the process and the tools we used , visit the `` dig deeper '' section on ed.ted.com .
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we used a tablet and one of the many stop motion apps out there . how do you get from point a to point b ? we started off by taking a bunch of pictures of celeste in place .
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which is not an example of “ how to get from point a to point b '' shown in the video ?
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there 's a common misconception that if you like to meticulously organize your things , keep your hands clean , or plan out your weekend to the last detail , you might have ocd . in fact , ocd , which stands for obsessive compulsive disorder , is a serious psychiatric condition that is frequently misunderstood by society and mental health professionals alike . so let 's start by debunking some myths . myth one : repetitive or ritualistic behaviors are synonymous with ocd . as its name suggests , obsessive compulsive disorder has two aspects : the intrusive thoughts , images , or impulses , known as obsessions , and the behavioral compulsions people engage in to relieve the anxiety the obsessions cause . the kinds of actions that people often associate with ocd , like excessive hand washing , or checking things repeatedly , may be examples of obsessive or compulsive tendencies that many of us exhibit from time to time . but the actual disorder is far more rare and can be quite debilitating . people affected have little or no control over their obsessive thoughts and compulsive behaviors , which tend to be time consuming and interfere with work , school or social life to the point of causing significant distress . this set of diagnostic criteria is what separates people suffering from ocd from those who may just be a bit more meticulous or hygiene obsessed than usual . myth two : the main symptom of ocd is excessive hand washing . although hand washing is the most common image of ocd in popular culture , obsessions and compulsions can take many different forms . obsessions can manifest as fears of contamination and illness , worries about harming others , or preoccupations with numbers , patterns , morality , or sexual identity . and compulsions can range from excessive cleaning or double checking , to the fastidious arrangement of objects , or walking in predetermined patterns . myth three : individuals with ocd do n't understand that they are acting irrationally . many individuals with ocd actually understand the relationship between their obsessions and compulsions quite well . being unable to avoid these thoughts and actions despite being aware of their irrationality is part of the reason why ocd is so distressing . ocd sufferers report feeling crazy for experiencing anxiety based on irrational thoughts and finding it difficult to control their responses . so what exactly causes ocd ? the frustrating answer is we do n't really know . however , we have some important clues . ocd is considered a neurobiological disorder . in other words , research suggests that ocd sufferers brains are actually hardwired to behave in a certain fashion . research has implicated three regions of the brain variously involved in social behavior and complex cognitive planning , voluntary movement , and emotional and motivational responses . the other piece of the puzzle is that ocd is associated with low levels of serotonin , a neurotransmitter that communicates between brain structures and helps regulate vital processes , such as mood , aggression , impulse control , sleep , appetite , body temperature and pain . but are serotonin and activity in these brain regions the sources of ocd or symptoms of an unknown underlying cause of the disorder . we probably wo n't know until we have a much more intimate understanding of the brain . the good news is there are effective treatments for ocd , including medications , which increase serotonin in the brain by limiting its reabsorption by brain cells , behavioral therapy that gradually desensitizes patients to their anxieties , and in some cases , electroconvulsive therapy , or surgery , when ocd does n't respond to other forms of treatment . knowing that your own brain is lying to you while not being able to resist its commands can be agonizing . but with knowledge and understanding comes the power to seek help , and future research into the brain may finally provide the answers we 're looking for .
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we probably wo n't know until we have a much more intimate understanding of the brain . the good news is there are effective treatments for ocd , including medications , which increase serotonin in the brain by limiting its reabsorption by brain cells , behavioral therapy that gradually desensitizes patients to their anxieties , and in some cases , electroconvulsive therapy , or surgery , when ocd does n't respond to other forms of treatment . knowing that your own brain is lying to you while not being able to resist its commands can be agonizing .
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conducting in vivo exposures in behavior therapy can often be difficult for those with ocd . can you think of some of the barriers to treatment ? are there other ways that individuals can face their fears ?
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so you see a few cubes sitting in an art gallery , and you think to yourself , `` this is the greatest hoax that anyone has ever pulled off . '' you immediately walk away , discouraged by the wide gulf between what you hope for when you walk into a museum and what they 've presented to you . how did we get here ? how could these cubes that the artist did n't even make with their own hands be important ? this is the case for minimalism . first off , we 're not talking about minimalism as a general sensibility or the life-changing magic of tidying up . we 're talking about the art of a particular moment in time . namely , the 1960s , when all of a sudden , there was a lot of geometric , abstract art . some of it was painting by artists like frank stella and ellsworth kelly , but most of it was sculpture by artists like donald judd , carl andre , dan flavin , anne truitt , robert morris , tony smith , ronald bladen , and sol lewitt . art critics called it abc art , object art , primary structures , and cool art , but the term minimalism prevailed . these artists never called their art minimalist , by the way , nor did they like the term , or the implication that the work was so reductive that it was minimally art . but minimalism was a rejection of what came before . specifically , abstract expressionism , which dominated the art market in the 1950s . these new artists wanted to remove expression completely , remove emotion , empty the work of idiosyncratic gesture , make it resistant to biographical reading . their hard-edged , basic shapes and forms avoided allusion , metaphor , and overt symbolism . the forms were often repeated , one thing after another in regular , non-hierarchical arrangements , rejecting compositional balancing . no artist hemming and hawing over the canvas here . the objects were impersonal , many of them machine-made , fabricated from new and industrial materials . sometimes this entailed ready-made units , like andre 's bricks , or flavin 's fluorescent tubes . they did n't want you to ooh and ah , or admire the handling of paint . as lewitt once said , `` it is best that the basic unit `` be deliberately uninteresting . '' robert morris wrote that he could hear a resounding no at the time . `` no to transcendence and spiritual values , `` heroic scale , anguished decisions , `` historicizing narrative , valuable artifact , `` intelligent structure , interesting visual experience . '' but what they were saying yes to was a new and startling realness . abandoning the pedestal to dismantle the separation between you and the art . judd claimed these works are neither painting nor sculpture , but instead specific objects occupying real space . these objects are n't pointing to anything or referencing anything . andre called his work a kind of plastic poetry , in which elements are combined to produce space . so there is no illusion of space , it just is space . minimalism had its haters from the start . in 1967 , art critic michael fried attacked the work for being theatrical . for him it was an object in a room that had presence before a viewer , but it did not have what good art has , which is presentness , or , `` an instant of aesthetic experience `` which occurs in no real space or time at all . '' but fried really just ended up affirming exactly what the artists were trying to do : proving how radical it really was . despite its detractors , minimalism became all the rage . this geometric , unadorned style flowed throughout the worlds of fashion , theater , and design . in short , it was cool . and then because these artists were never trying to be minimalist to begin with , they moved on to other things and other kinds of art had its day . but minimalism changed things . for centuries , art had been trying to trick you , convince you that the hunk of rock was something other than a hunk of rock . but not this . you feel like there 's got ta be some secret to it , but there is n't . there 's nothing to interpret . this is what it is . it was n't supposed to look like art of the past , and it was n't supposed to function like it either . with minimalism , meaning does n't rest inside the object , waiting to be unlocked . the meaning is in the context , and exists in your interaction with it . but minimalism is a resistant lover . it 's just not that into you . it encourages observation , but does n't draw you in , and it was never trying to . remember , these objects were supposed to be emptied of prevention , of mastery , of the usual seduction between art and viewer , and of the grand , glorious traditions that preceded them . but the fetishization and commodification of minimalist art has complicated and polluted these ideas . what 's less real than million-dollar plywood boxes ? and yet , for me at least , minimalist art can still impart a strong feeling , a feeling for space , light , for presence and absence . you 're aware of your own body in the gallery as you 've never been before . you notice that your position in the room shapes your perception of the thing . you appreciate the architecture and the spareness , and in a world filled with complexity and information and lots and lots of stuff , this is a balm . this is a world more simplified than the actual world is , and that i can appreciate .
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remember , these objects were supposed to be emptied of prevention , of mastery , of the usual seduction between art and viewer , and of the grand , glorious traditions that preceded them . but the fetishization and commodification of minimalist art has complicated and polluted these ideas . what 's less real than million-dollar plywood boxes ?
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how does the commodification and fetishization of minimalist art undermine its initial goals and values ?
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you probably know the feeling . your phone utters its final plaintive `` bleep '' and cuts out in the middle of your call . in that moment , you may feel more like throwing your battery across the room than singing its praises , but batteries are a triumph of science . they allow smartphones and other technologies to exist without anchoring us to an infernal tangle of power cables . yet even the best batteries will diminish daily , slowly losing capacity until they finally die . so why does this happen , and how do our batteries even store so much charge in the first place ? it all started in the 1780s with two italian scientists , luigi galvani and alessandro volta , and a frog . legend has it that as galvani was studying a frog 's leg , he brushed a metal instrument up against one of its nerves , making the leg muscles jerk . galvani called this animal electricity , believing that a type of electricity was stored in the very stuff of life . but volta disagreed , arguing that it was the metal itself that made the leg twitch . the debate was eventually settled with volta 's groundbreaking experiment . he tested his idea with a stack of alternating layers of zinc and copper , separated by paper or cloth soaked in a salt water solution . what happened in volta 's cell is something chemists now call oxidation and reduction . the zinc oxidizes , which means it loses electrons , which are , in turn , gained by the ions in the water in a process called reduction , producing hydrogen gas . volta would have been shocked to learn that last bit . he thought the reaction was happening in the copper , rather than the solution . none the less , we honor volta 's discovery today by naming our standard unit of electric potential `` the volt . '' this oxidation-reduction cycle creates a flow of electrons between two substances and if you hook a lightbulb or vacuum cleaner up between the two , you 'll give it power . since the 1700s , scientists have improved on volta 's design . they 've replaced the chemical solution with dry cells filled with chemical paste , but the principle is the same . a metal oxidizes , sending electrons to do some work before they are regained by a substance being reduced . but any battery has a finite supply of metal , and once most of it has oxidized , the battery dies . so rechargeable batteries give us a temporary solution to this problem by making the oxidation-reduction process reversible . electrons can flow back in the opposite direction with the application of electricity . plugging in a charger draws the electricity from a wall outlet that drives the reaction to regenerate the metal , making more electrons available for oxidation the next time you need them . but even rechargeable batteries do n't last forever . over time , the repetition of this process causes imperfections and irregularities in the metal 's surface that prevent it from oxidizing properly . the electrons are no longer available to flow through a circuit and the battery dies . some everyday rechargeable batteries will die after only hundreds of discharge-recharge cycles , while newer , advanced batteries can survive and function for thousands . batteries of the future may be light , thin sheets that operate on the principles of quantum physics and last for hundreds of thousands of charge cycles . but until scientists find a way to take advantage of motion to recharge your cell battery , like cars do , or fit solar panels somewhere on your device , plugging your charger into the wall , rather than expending one battery to charge another is your best bet to forestall that fatal `` bleep . ''
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plugging in a charger draws the electricity from a wall outlet that drives the reaction to regenerate the metal , making more electrons available for oxidation the next time you need them . but even rechargeable batteries do n't last forever . over time , the repetition of this process causes imperfections and irregularities in the metal 's surface that prevent it from oxidizing properly .
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why do rechargeable batteries eventually lose their ability to be recharged ?
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there was a time before our ancestors smashed flint and steel together , when they felt the cold lack of fire in their lives . but anthropologists theorize that early hominids relied on lightning to cause forest fires , from which they could collect coals and burning sticks . fire gave them the ability to cook food and clear land , and became central in many rituals and traditions . so instead of seeing forest fires as an exclusively bad thing , ancient humans may have learned to appreciate them . yet , it was n't just humans who benefitted from these natural phenomena . even as they destroy trees , fires also help the forest themselves , however counterintuitive that seems . in fact , several forest species , such as select conifers , need fire to survive . but how can fire possibly create life in addition to destroying it ? the answer lies in the way that certain forests grow . in the conifer-rich forests of western north america , lodgepole pines constantly seek the sun . their seeds prefer to grow on open sunny ground , which pits saplings against each other as each tries to get more light by growing straighter and faster than its neighbors . over time , generations of slender , lofty lodgepoles form an umbrella-like canopy that shades the forest floor below . but as the trees ' pine cones mature to release their twirling seeds , this signals a problem for the lodgepoles ' future . very few of these seeds will germintate in the cool , sunless shade created by their towering parents . these trees have adapted to this problem by growing two types of cones . there are the regular annual cones that release seeds spontaneously , and another type called serotinous cones , which need an environmental trigger to free their seeds . serotinous cones are produced in thousands , and are like waterproofed time capsules sealed with resinous pitch . many are able to stay undamaged on the tree for decades . cones that fall to the ground can be viable for several years , as well . but when temperatures get high enough , the cones pop open . let 's see that in action . once it 's gotten started , a coniferous forest fire typically spreads something like this . flames ravage the thick understory provided by species like douglas fir , a shade-tolerant tree that 's able to thrive under the canopy of lodgepole pines . the fire uses these smaller trees as a step ladder to reach the higher canopy of old lodgepole pines . that ignites a tremendous crown fire reaching temperatures of up to 2400 degrees fahrenheit . that 's well more than the 115-140 degrees that signal the moment when serotinous seeds can be freed . at those temperatures , the cones burst open , releasing millions of seeds , which are carried by the hot air to form new forests . after the fire , carbon-rich soils and an open sunlit landscape help lodgepole seeds germinate quickly and sprout in abundance . from the death of the old forest comes the birth of the new . fires are also important for the wider ecosystem as a whole . without wildfires to rejuvenate trees , key forest species would disappear , and so would the many creatures that depend on them . and if a fire-dependent forest goes too long without burning , that raises the risk of a catastrophic blaze , which could destroy a forest completely , not to mention people 's homes and lives . that 's why forest rangers sometimes intentionally start controlled burns to reduce fuels in order to keep the more dangerous wildfires at bay . they may be frightening and destructive forces of nature , but wildfires are also vital to the existence of healthy boreal forest ecosystems . by coming to terms with that , we can protect ourselves from their more damaging effects while enabling the forests , like the legendary phoenix , to rise reborn from their own ashes .
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once it 's gotten started , a coniferous forest fire typically spreads something like this . flames ravage the thick understory provided by species like douglas fir , a shade-tolerant tree that 's able to thrive under the canopy of lodgepole pines . the fire uses these smaller trees as a step ladder to reach the higher canopy of old lodgepole pines .
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douglas fir trees thrive beneath the umbrella of the taller lodgepoles because they are _________ .
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your cell phone is mainly made of plastics and metals . it 's easy to appreciate the inventive process by which those elements are made to add up to something so useful and entertaining . but there 's another story we do n't hear about as much . how did we get our raw ingredients in the first place from the chaotic tangle of materials that is nature ? the answer is a group of clever hacks known as separation techniques . they work by taking advantage of the fundamental properties of things to disentangle them from each other . simple separation techniques apply to many physical scenarios , like separating cream from milk , extracting water from soil , or even sifting out flecks of gold from river sand . but not all mixtures are so easy to unravel . in some of those cases , we can exploit the differences between physical properties within a mixture , like particle size , density , or boiling point to extract what 's required . take petroleum , a mixture of different types of hydrocarbons . some of these are valuable as fuels , and others make good raw materials for generating electric power . to separate them , experts rely on one important feature : different hydrocarbons boil at different temperatures . during the boiling process , each type vaporizes at a precise point , then gets separately funneled into a container and collected as a liquid as it cools . separation techniques also take us to the sea . in some drought-stricken countries , the ocean is the only available water source . but of course , humans ca n't drink salt water . one way to get around this problem is to remove salt from sea water with reverse osmosis , a process that separates water 's ingredients by size . a membrane with pores bigger than water particles , but smaller than salt particles , only lets fresh water pass through , transforming what was once undrinkable into a life saver . meanwhile in the medical world , blood tests are a vital tool for evaluating a person 's health , but doctors typically ca n't examine blood samples until they 've separated the solid blood cells from the liquid plasma they 're dissolved in . to do that , a powerful rotational force is exerted on the test tube , causing heavier substances with higher density , like blood cells , to move away from the rotational axis . meanwhile , lighter substances with lower density , like plasma , move to its center . the tube 's contents divide clearly , and the blood cells and liquid plasma can be tested independently . but sometimes , unlike oil , seawater , and blood , the parts of mixtures that we want to separate share the same physical properties . in these cases , the only way to isolate ingredients is by chemical separation , a complex process that relies on unique interactions between components within a mixture and another material . one of these methods is chromatography , a tool forensic scientists use to examine crime scenes . they dissolve gathered evidence in a gas , and can monitor and analyze the ingredients as they separate and move at varying speeds due to their unique chemical properties . that information then tells scientists precisely what was present at the scene , often helping to identify the culprit . separation techniques are not just about industry , infrastructure , medicine , and justice . one of the most technically ambitious projects in human history is a separation technique aimed at answering the fundamental question , `` what is the universe made of ? '' by accelerating particles to extremely high speeds and smashing them into each other , we can break them into their constituent parts ever so briefly . and if we succeed at that , what 's next ? is there a most elementary particle ? and if so , what 's it made of ?
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in these cases , the only way to isolate ingredients is by chemical separation , a complex process that relies on unique interactions between components within a mixture and another material . one of these methods is chromatography , a tool forensic scientists use to examine crime scenes . they dissolve gathered evidence in a gas , and can monitor and analyze the ingredients as they separate and move at varying speeds due to their unique chemical properties .
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chromatography works by :
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[ music playing ] my goal is to not actually do any measurements other than using pie . so the entire thing is going to pie based . we get the circumference in the exact number of pies -- give or take -- we get the diameter in number of pies . divide one by the other , we get pi . [ music playing ] pi was historically rarely calculated this way , because it 's notoriously inaccurate to try and get -- i know , we 're idiots -- it 's notoriously inaccurate to try and calculate pi by measuring a circle . [ music playing ] to get any kind of accuracy on our final answer we have to be as precise as we can be . [ music playing ] this is a mild problem , because i want to go from the very edge of the circle . but as you can see , i 've positioned all the pies exactly on the line as if they 're little mini tangents . so i 'm going to have to move these two out and then i can start doing the diameter exactly on the circumference there , like that . [ music playing ] so that 's 84 and 1/3 . 264 and 2/3 pies around , we have the diameter , is 84 and 1/3 pie . to get pi , we just divide the circumference by the diameter . ok , and if we actually work out what that is , it equals -- that 's pretty good . pi from pies , we got 3.13834 , which is approximately 3.14 . so using pies , we 've got pi to be 3.14 . i am a very happy man right now . with the diameter , and if i know that ratio , i can just measure the diameter . that 's the easy bit to measure . the center point will be my pen , and the outside will be the chalk . so the pies , in theory , are a fairly consistent size . so they 're all -- yeah they 're about the same . ok. [ music playing ]
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pi from pies , we got 3.13834 , which is approximately 3.14 . so using pies , we 've got pi to be 3.14 . i am a very happy man right now .
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even with more of the circular pies , why would it have been impossible to cover the area of the circle with them and calculate pi using the area of a circle formula area = pi * r^2 ?
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do you have a friend or a sibling that 's always competing with you to see who 's the fastest ? our alien friends bleebop and mark are having the same debate with their custom-built rockets , and they 've asked us to be the judge of a space race to their moon . the only problem is that they are starting from different asteroids . bleebop is on an asteroid 240 miles from the moon , and mark is on one 150 miles away . do n't worry , it 's not rocket science . solving this equation is as simple as dirt . we can decide who the winner is using the d=rt formula , or dirt . this stands for distance equals rate times time . in the case of bleebop and mark , we will only know the distance they traveled and the time it took for them to get to the finish line . it 'll be up to us to find the rate and who is faster . let 's turn to the race now and see what information we get . three , two , one , blast off ! bleebop and mark 's rockets go zipping across the galaxy towards their moon , dodging clunky meteorites and loopy space buggies . after a few close calls with a wandering satellite , mark arrives first in two hours , and bleebop gets there one hour later . looks like mark has the faster rocket , but let 's check out the results with our dirt equation . begin by setting up a chart . make four columns and three rows . use dirt to remember what to fill in . each rocket will have information for distance , rate , and time . mark 's rocket went 150 miles , we do n't know the rate , and he got there in 2 hours . bleebop 's rocket went 240 miles , we do n't know the rate , and the time is 1 hour after mark , or 3 hours . because we do n't know mark or bleebop 's rate , that number is going to be a variable in each equation , which we 'll represent with x . we 'll solve the equation for the variable to find its value . mark finished first , so start with his rocket . remembering dirt , write down d=rt . 150 miles equals x times 2 hours . divide both sides by 2 hours . this will leave x isolated on the right side of the equation . 150 miles divided by 2 hours is 75 miles over 1 hour . mark 's rate is 75 miles per hour . that 's what mph means . it 's the amount of miles over one hour . still think mark is faster ? let 's set up the same equation for bleebop and see . d=rt 240 miles equals x times 3 hours . divide both sides by 3 hours . this will leave x isolated on the right side of the equation . 240 miles divided by 3 hours is 80 miles over 1 hour . bleebop 's rate is 80 miles per hour . wow , even though bleebop got there one hour later , it turns out he had the faster rocket . mark seems pretty upset , but with aliens , you can never really tell . thanks to dirt , you now know how to calculate distance , rate , and time . in what other situations can you use the distance formula ? you do n't even need to be watching a space race . as long as you know two pieces of information for the formula d=rt , you can calculate any moving vehicle or object . now , the next time you 're in a car , you can let your friends know exactly when you 'll be arriving , how fast you 're going , or the distance you 'll travel . it 's as simple as dirt .
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thanks to dirt , you now know how to calculate distance , rate , and time . in what other situations can you use the distance formula ? you do n't even need to be watching a space race . as long as you know two pieces of information for the formula d=rt , you can calculate any moving vehicle or object .
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how would you be able to predict the outcome of a bike race between two people if you knew the distance of the race and how fast each person was able to ride ?
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you 've been stranded thousands of miles from home with no money or possessions . such a predicament would make many people despair and curse their awful fate . but for zeno of cyprus , it became the foundation of his life 's work and legacy . the once wealthy merchant lost everything when he was shipwrecked in athens around 300 bce . with not much else to do , he wandered into a book shop , became intrigued by reading about socrates , and proceeded to seek out and study with the city 's noted philosophers . as zeno began educating his own students , he originated the philosophy known as stoicism , whose teachings of virtue , tolerance , and self-control have inspired generations of thinkers and leaders . the name stoicism comes from the stoa poikile , the decorated public colonnade where zeno and his disciples gathered for discussion . today , we colloquially use the word stoic to mean someone who remains calm under pressure and avoids emotional extremes . but while this captures important aspects of stoicism , the original philosophy was more than just an attitude . the stoics believed that everything around us operates according to a web of cause and effect , resulting in a rational structure of the universe , which they called logos . and while we may not always have control over the events affecting us , we can have control over how we approach things . rather than imagining an ideal society , the stoic tries to deal with the world as it is while pursuing self-improvement through four cardinal virtues : practical wisdom , the ability to navigate complex situations in a logical , informed , and calm manner ; temperance , the exercise of self-restraint and moderation in all aspects of life ; justice , treating others with fairness even when they have done wrong ; and courage , not just in extraordinary circumstances , but facing daily challenges with clarity and integrity . as seneca , one of the `most famous roman stoics wrote , `` sometimes , even to live is an act of courage . '' but while stoicism focuses on personal improvement , it 's not a self-centered philosophy . at a time when roman laws considered slaves as property , seneca called for their humane treatment and stressed that we all share the same fundamental humanity . nor does stoicism encourage passivity . the idea is that only people who have cultivated virtue and self-control in themselves can bring positive change in others . one of the most famous stoic writers was also one of rome 's greatest emperors . over the course of his 19-year reign , stoicism gave marcus aurelius the resolve to lead the empire through two major wars , while dealing with the loss of many of his children . centuries later , marcus 's journals would guide and comfort nelson mandela through his 27-year imprisonment during his struggle for racial equality in south africa . after his release and eventual victory , mandela stressed peace and reconciliation , believing that while the injustices of the past could n't be changed , his people could confront them in the present and seek to build a better , more just future . stoicism was an active school of philosophy for several centuries in greece and rome . as a formal institution , it faded away , but its influence has continued to this day . christian theologians , such as thomas aquinas , have admired and adopted its focus on the virtues , and there are parallels between stoic ataraxia , or tranquility of mind , and the buddhist concept of nirvana . one particularly influential stoic was the philosopher epictetus who wrote that suffering stems not from the events in our lives , but from our judgements about them . this has resonated strongly with modern psychology and the self-help movement . for example , rational emotive behavioral therapy focuses on changing the self-defeating attitudes people form about their life circumstances . there 's also viktor frankl 's logotherapy . informed by frankl 's own time as a concentration camp prisoner , logotherapy is based on the stoic principle that we can harness our will power to fill our lives with meaning , even in the bleakest situations .
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such a predicament would make many people despair and curse their awful fate . but for zeno of cyprus , it became the foundation of his life 's work and legacy . the once wealthy merchant lost everything when he was shipwrecked in athens around 300 bce .
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why is it that practicing virtue , i.e. , trying to live with moral integrity , is a key to a life well lived ?
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what 's your sign ? in western astrology , it 's a constellation determined by when your birthday falls in the calendar . but according to the chinese zodiac , or shēngxiào , it 's your shǔxiàng , meaning the animal assigned to your birth year . and of the many myths explaining these animal signs and their arrangement , the most enduring one is that of the great race . as the story goes , yù dì , or jade emperor , ruler of the heavens , wanted to devise a way to measure time , so he organized a race . the first twelve animals to make it across the river would earn a spot on the zodiac calendar in the order they arrived . the rat rose with the sun to get an early start , but on the way to the river , he met the horse , the tiger , and the ox . because the rat was small and could n't swim very well , he asked the bigger animals for help . while the tiger and horse refused , the kind-hearted ox agreed to carry the rat across . yet , just as they were about to reach the other side , the rat jumped off the ox 's head and secured first place . the ox came in second , with the powerful tiger right behind him . the rabbit , too small to battle the current , nimbly hopped across stones and logs to come in fourth . next came the dragon , who could have flown directly across , but stopped to help some creatures she had encountered on the way . after her came the horse , galloping across the river . but just as she got across , the snake slithered by . the startled horse reared back , letting the snake sneak into sixth place . the jade emperor looked out at the river and spotted the sheep , the monkey , and the rooster all atop a raft , working together to push it through the weeds . when they made it across , the trio agreed to give eighth place to the sheep , who had been the most comforting and harmonious of them , followed by the monkey and the rooster . next came the dog , scrambling onto the shore . he was a great swimmer , but frolicked in the water for so long that he only managed to come in eleventh . the final spot was claimed by the pig , who had gotten hungry and stopped to eat and nap before finally waddling across the finish line . and so , each year is associated with one of the animals in this order , with the cycle starting over every 60 years . why 60 and not twelve ? well , the traditional chinese calendar is made up of two overlapping systems . the animals of the zodiac are associated with what 's called the twelve earthly branches , or shí'èrzhī . another system , the ten heavenly stems , or tiāngān , is linked with the five classical elements of metal , xīn , wood , mù , water , shuǐ , fire , huǒ , and earth , tǔ . each element is assigned yīn or yáng , creating a ten-year cycle . when the twelve animals of the earthly branches are matched with the five elements plus the yīn or the yáng of the heavenly stems , it creates 60 years of different combinations , known as a sexagenary cycle , or gānzhī . so someone born in 1980 would have the sign of yáng metal monkey , while someone born in 2007 would be yīn fire pig . in fact , you can also have an inner animal based on your birth month , a true animal based on your birth date , and a secret animal based on your birth hour . it was the great race that supposedly determined which animals were enshrined in the chinese zodiac , but as the system spread through asia , other cultures made changes to reflect their communities . so if you consult the vietnamese zodiac , you may discover that you 're a cat , not a rabbit , and if you 're in thailand , a mythical snake called a naga replaces the dragon . so whether or not you place stock in what the zodiac says about you as an individual , it certainly reveals much about the culture it comes from .
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as the story goes , yù dì , or jade emperor , ruler of the heavens , wanted to devise a way to measure time , so he organized a race . the first twelve animals to make it across the river would earn a spot on the zodiac calendar in the order they arrived . the rat rose with the sun to get an early start , but on the way to the river , he met the horse , the tiger , and the ox .
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how did the emperor decide the order of the zodiac signs ?
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in many ways , our memories make us who we are , helping us remember our past , learn and retain skills , and plan for the future . and for the computers that often act as extensions of ourselves , memory plays much the same role , whether it 's a two-hour movie , a two-word text file , or the instructions for opening either , everything in a computer 's memory takes the form of basic units called bits , or binary digits . each of these is stored in a memory cell that can switch between two states for two possible values , 0 and 1 . files and programs consist of millions of these bits , all processed in the central processing unit , or cpu , that acts as the computer 's brain . and as the number of bits needing to be processed grows exponentially , computer designers face a constant struggle between size , cost , and speed . like us , computers have short-term memory for immediate tasks , and long-term memory for more permanent storage . when you run a program , your operating system allocates area within the short-term memory for performing those instructions . for example , when you press a key in a word processor , the cpu will access one of these locations to retrieve bits of data . it could also modify them , or create new ones . the time this takes is known as the memory 's latency . and because program instructions must be processed quickly and continuously , all locations within the short-term memory can be accessed in any order , hence the name random access memory . the most common type of ram is dynamic ram , or dram . there , each memory cell consists of a tiny transistor and a capacitor that store electrical charges , a 0 when there 's no charge , or a 1 when charged . such memory is called dynamic because it only holds charges briefly before they leak away , requiring periodic recharging to retain data . but even its low latency of 100 nanoseconds is too long for modern cpus , so there 's also a small , high-speed internal memory cache made from static ram . that 's usually made up of six interlocked transistors which do n't need refreshing . sram is the fastest memory in a computer system , but also the most expensive , and takes up three times more space than dram . but ram and cache can only hold data as long as they 're powered . for data to remain once the device is turned off , it must be transferred into a long-term storage device , which comes in three major types . in magnetic storage , which is the cheapest , data is stored as a magnetic pattern on a spinning disc coated with magnetic film . but because the disc must rotate to where the data is located in order to be read , the latency for such drives is 100,000 times slower than that of dram . on the other hand , optical-based storage like dvd and blu-ray also uses spinning discs , but with a reflective coating . bits are encoded as light and dark spots using a dye that can be read by a laser . while optical storage media are cheap and removable , they have even slower latencies than magnetic storage and lower capacity as well . finally , the newest and fastest types of long-term storage are solid-state drives , like flash sticks . these have no moving parts , instead using floating gate transistors that store bits by trapping or removing electrical charges within their specially designed internal structures . so how reliable are these billions of bits ? we tend to think of computer memory as stable and permanent , but it actually degrades fairly quickly . the heat generated from a device and its environment will eventually demagnetize hard drives , degrade the dye in optical media , and cause charge leakage in floating gates . solid-state drives also have an additional weakness . repeatedly writing to floating gate transistors corrodes them , eventually rendering them useless . with data on most current storage media having less than a ten-year life expectancy , scientists are working to exploit the physical properties of materials down to the quantum level in the hopes of making memory devices faster , smaller , and more durable . for now , immortality remains out of reach , for humans and computers alike .
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and because program instructions must be processed quickly and continuously , all locations within the short-term memory can be accessed in any order , hence the name random access memory . the most common type of ram is dynamic ram , or dram . there , each memory cell consists of a tiny transistor and a capacitor that store electrical charges , a 0 when there 's no charge , or a 1 when charged .
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what is the common feature between dram and sram ?
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me , myself , and i . you may be tempted to use these words interchangeably because they all refer to the same thing , but in fact , each one has a specific role in a sentence . `` i '' is a subject pronoun , `` me '' is an object pronoun , and `` myself '' is a reflexive or intensive pronoun . so what does that reveal about where each word belongs ? let 's start with the difference between subject and object . imagine the subject as the actor in a sentence and the object as the word that is acted upon . `` i invited her but she invited me . '' the object can also be the object of a preposition . `` she danced around me , while he shimmied up to me . '' in some languages , like latin and russian , most nouns have different forms that distinguish subjects from objects . however , in english , that 's only true of pronouns . but so long as you know how to distinguish subjects from objects , you can figure out what belongs where . and when you encounter a more complicated sentence , say one that involves multiple subjects or objects , and you 're not sure whether to use `` i '' or `` me , '' just temporarily eliminate the other person , and once again distinguish subject from object . here 's another . you would n't say , `` me heard gossip , '' but sub in `` i '' and you 're good to go . then what about `` myself ? '' this grand character is often substituted for `` me '' and `` i '' because it seems more impressive . `` please tell jack or myself '' may sound elegant , but in fact , `` me '' is the right pronoun here . so where should you use `` myself '' ? in its function as a reflexive pronoun , `` myself '' only works if it 's the object of a sentence whose subject is `` i . '' `` i consider myself the most important pronoun at this year 's party . '' `` myself '' can also add emphasis as an intensive pronoun . `` i , myself , have heard others agree . '' the sentence works without it , but that extra pronoun gives it oomph . to check if `` myself '' belongs in a sentence , simply ensure that there 's also an `` i '' that it 's reflecting or intensifying . so that 's `` me , '' `` myself , '' and `` i , '' ever ready to represent you , yourself , and you .
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`` i , myself , have heard others agree . '' the sentence works without it , but that extra pronoun gives it oomph . to check if `` myself '' belongs in a sentence , simply ensure that there 's also an `` i '' that it 's reflecting or intensifying .
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in a sentence :
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many of us have hundreds of things on our minds at any moment , often struggling to keep track of everything we need to do . but fortunately , there 's one important thing we do n't have to worry about remembering : breathing . when you breathe , you transport oxygen to the body 's cells to keep them working and clear your system of the carbon dioxide that this work generates . breathing , in other words , keeps the body alive . so , how do we accomplish this crucial and complex task without even thinking about it ? the answer lies in our body 's respiratory system . like any machinery , it consists of specialized components , and requires a trigger to start functioning . here , the components are the structures and tissues making up the lungs , as well as the various other respiratory organs connected to them . and to get this machine moving , we need the autonomic nervous system , our brain 's unconscious control center for the vital functions . as the body prepares to take in oxygen-rich air , this system sends a signal to the muscles around your lungs , flattening the diaphragm and contracting the intercostal muscles between your ribs to create more space for the lungs to expand . air then wooshes into your nose and mouth , through your trachea , and into the bronchi that split at the trachea 's base , with one entering each lung . like tree branches , these small tubes divide into thousands of tinier passages called bronchioles . it 's tempting to think of the lungs as huge balloons , but instead of being hollow , they 're actually spongy inside , with the bronchioles running throughout the parenchyma tissue . at the end of each bronchiole is a little air sack called an alveolus , wrapped in capillaries full of red blood cells containing special proteins called hemoglobin . the air you 've breathed in fills these sacks , causing the lungs to inflate . here is where the vital exchange occurs . at this point , the capillaries are packed with carbon dioxide , and the air sacks are full of oxygen . but due to the basic process of diffusion , the molecules of each gas want to move to a place where there 's a lower concentration of their kind . so as oxygen crosses over to the capillaries , the hemoglobin grabs it up , while the carbon dioxide is unloaded into the lungs . the oxygen-rich hemoglobin is then transported throughout the body via the bloodstream . but what do our lungs do with all that carbon dioxide ? exhale it , of course . the autonomic nervous system kicks in again , causing the diaphragm to ball up , and the intercostal muscles to relax , making the chest cavities smaller and forcing the lungs to compress . the carbon dioxide-rich air is expelled , and the cycle begins again . so that 's how these spongy organs keep our bodies efficiently supplied with air . lungs inhale and exhale between 15 and 25 times a minute , which amounts to an incredible 10,000 liters of air each day . that 's a lot of work , but do n't sweat it . your lungs and your autonomic nervous system have got it covered .
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the oxygen-rich hemoglobin is then transported throughout the body via the bloodstream . but what do our lungs do with all that carbon dioxide ? exhale it , of course .
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how do the lungs get rid of all the co2 they 've picked up from the blood ?
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imagine , for a second , a duck teaching a french class , a ping-pong match in orbit around a black hole , a dolphin balancing a pineapple . you probably have n't actually seen any of these things , but you could imagine them instantly . how does your brain produce an image of something you 've never seen ? that may not seem hard , but that 's only because we 're so used to doing it . it turns out that this is actually a complex problem that requires sophisticated coordination inside your brain . that 's because to create these new , weird images , your brain takes familiar pieces and assembles them in new ways , like a collage made from fragments of photos . the brain has to juggle a sea of thousands of electrical signals getting them all to their destination at precisely the right time . when you look at an object , thousands of neurons in your posterior cortex fire . these neurons encode various characteristics of the object : spiky , fruit , brown , green , and yellow . this synchronous firing strengthens the connections between that set of neurons , linking them together into what 's known as a neuronal ensemble , in this case the one for pineapple . in neuroscience , this is called the hebbian principle , neurons that fire together wire together . if you try to imagine a pineapple later , the whole ensemble will light up , assembling a complete mental image . dolphins are encoded by a different neuronal ensemble . in fact , every object that you 've seen is encoded by a neuronal ensemble associated with it , the neurons wired together by that synchronized firing . but this principle does n't explain the infinite number of objects that we can conjure up in our imaginations without ever seeing them . the neuronal ensemble for a dolphin balancing a pineapple does n't exist . so how come you can imagine it anyway ? one hypothesis , called the mental synthesis theory , says that , again , timing is key . if the neuronal ensembles for the dolphin and pineapple are activated at the same time , we can perceive the two separate objects as a single image . but something in your brain has to coordinate that firing . one plausible candidate is the prefrontal cortex , which is involved in all complex cognitive functions . prefrontal cortex neurons are connected to the posterior cortex by long , spindly cell extensions called neural fibers . the mental synthesis theory proposes that like a puppeteer pulling the strings , the prefrontal cortex neurons send electrical signals down these neural fibers to multiple ensembles in the posterior cortex . this activates them in unison . if the neuronal ensembles are turned on at the same time , you experience the composite image just as if you 'd actually seen it . this conscious purposeful synchronization of different neuronal ensembles by the prefrontal cortex is called mental synthesis . in order for mental sythesis to work , signals would have to arrive at both neuronal ensembles at the same time . the problem is that some neurons are much farther away from the prefrontal cortex than others . if the signals travel down both fibers at the same rate , they 'd arrive out of sync . you ca n't change the length of the connections , but your brain , especially as it develops in childhood , does have a way to change the conduction velocity . neural fibers are wrapped in a fatty substance called myelin . myelin is an insulator and speeds up the electrical signals zipping down the nerve fiber . some neural fibers have as many as 100 layers of myelin . others only have a few . and fibers with thicker layers of myelin can conduct signals 100 times faster or more than those with thinner ones . some scientists now think that this difference in myelination could be the key to uniform conduction time in the brain , and consequently , to our mental synthesis ability . a lot of this myelination happens in childhood , so from an early age , our vibrant imaginations may have a lot to do with building up brains whose carefully myelinated connections can craft creative symphonies throughout our lives .
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if you try to imagine a pineapple later , the whole ensemble will light up , assembling a complete mental image . dolphins are encoded by a different neuronal ensemble . in fact , every object that you 've seen is encoded by a neuronal ensemble associated with it , the neurons wired together by that synchronized firing .
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what is a neuronal ensemble ?
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the city has just opened its one-of-a-kind fabergé egg museum with a single egg displayed on each floor of a 100-story building . and the world 's most notorious jewel thief already has her eyes on the prize . because security is tight and the eggs are so large , she 'll only get the chance to steal one by dropping it out the window into her waiting truck and repelling down before the police can arrive . all eggs are identical in weight and construction , but each floor 's egg is more rare and valuable than the one below it . while the thief would naturally like to take the priceless egg at the top , she suspects it wo n't survive a 100-story drop . being pragmatic , she decides to settle for the most expensive egg she can get . in the museum 's gift shop , she finds two souvenir eggs , perfect replicas that are perfectly worthless . the plan is to test drop them to find the highest floor at which an egg will survive the fall without breaking . of course , the experiment can only be repeated until both replica eggs are smashed . and throwing souvenirs out the window too many times is probably going to draw the guards ' attention . what 's the least number of tries it would take to guarantee that she find the right floor ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 if you 're having trouble getting started on the solution , it might help to start with a simpler scenario . imagine our thief only had one replica egg . she 'd have a single option : to start by dropping it from the first floor and go up one by one until it breaks . then she 'd know that the floor below that is the one she needs to target for the real heist . but this could require as many as 100 tries . having an additional replica egg gives the thief a better option . she can drop the first egg from different floors at larger intervals in order to narrow down the range where the critical floor can be found . and once the first breaks , she can use the second egg to explore that interval floor by floor . large floor intervals do n't work great . in the worst case scenario , they require many tests with the second egg . smaller intervals work much better . for example , if she starts by dropping the first egg from every 10th floor , once it breaks , she 'll only have to test the nine floors below . that means it 'll take at most 19 tries to find the right floor . but can she do even better ? after all , there 's no reason every interval has to be the same size . let 's say there were only ten floors . the thief could test this whole building with just four total throws by dropping the first egg at floors four , seven , and nine . if it broke at floor four , it would take up to three throws of the second egg to find the exact floor . if it broke at seven , it would take up to two throws with the second egg . and if it broke at floor nine , it would take just one more throw of the second egg . intuitively , what we 're trying to do here is divide the building into sections where no matter which floor is correct , it takes up to the same number of throws to find it . we want each interval to be one floor smaller than the last . this equation can help us solve for the first floor we need to start with in the 100 floor building . there are several ways to solve this equation , including trial and error . if we plug in two for n , that equation would look like this . if we plug in three , we get this . so we can find the first n to pass 100 by adding more terms until we get to our answer , which is 14 . and so our thief starts on the 14th floor , moving up to the 27th , the 39th , and so on , for a maximum of 14 drops . like the old saying goes , you ca n't pull a heist without breaking a few eggs .
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because security is tight and the eggs are so large , she 'll only get the chance to steal one by dropping it out the window into her waiting truck and repelling down before the police can arrive . all eggs are identical in weight and construction , but each floor 's egg is more rare and valuable than the one below it . while the thief would naturally like to take the priceless egg at the top , she suspects it wo n't survive a 100-story drop . being pragmatic , she decides to settle for the most expensive egg she can get .
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suppose the thief had 3 eggs for the experiments . how would this make a difference ( if at all ) ?
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humans have observed comets for thousands of years as their orbits have brought them within visible distance of earth . appearing throughout historical records , these mysterious lights that came out of nowhere and disappeared after a short while were thought to be ill omens of war and famine , or the wrath of gods . but recent research has revealed that comets may be even more deeply connected to humanity and our presence on earth than any of these mythical explanations suggested . when you think of our solar system , you probably imagine the nine , sorry eight , planets orbiting the sun . but beyond neptune , far from the heat of the sun , there is a sparse ring found formed by icy chunks ranging from the size of marbles to that of small planets . and thousands of times farther at the outer reaches of the solar system lies a spherical cloud of small fragments and gases . many of these ancient clumps of stardust are leftovers from the formation of the solar system 4.6 billion years ago , while some of the most distant may even come from a neighboring system . but sometimes the gravity from passing planets or stars pulls them toward our sun , beginning a journey that can take up to millions of years . as the frozen object travels further into the solar system , the sun grows from a distant spark to an inferno , melting the ice for the first time in billions of years . gas and steam eject dust into space , forming a bright surrounding cloud , called a coma , that can grow even larger than the sun itself . meanwhile , the intense stream of high-energy particles constantly emitted by the sun , known as the solar wind , blows particles away from the comet 's core , forming a trail of debris up to millions of miles long . the ice , gas and dust reflect light glowing brightly . a comet is born , now orbiting the sun along with the rest of the objects in our solar system . but as the comet travels through the solar system , the solar wind tears apart and recombines molecules into various compounds . in some of the compounds that scientists found , first in the rubble left by a meteorite that disintegrated above northern canada , and then in samples collected by a space craft from a passing comet 's tail , were nothing less important than amino acids . coming together to form proteins according to the instructs encoded in dna , these are the main active components in all living cells , from bacteria to blue whales . if comets are where these building blocks of life were first formed , then they are the ultimate source of life on earth , and , perhaps , some of the other places they visited as well . we know that planets orbit nearly every star in the night sky , with one in five having a planet similar to earth in size and temperature . if earth-like planets and the molecules found in dna are not anomalies , we may be only one example of what 's possible when a planet under the right conditions is seeded with organic molecules by a passing comet . so , rather than an omen of death , the comet that first brought amino acids to earth could have been a portent of life , a prediction of a distant future , where creatures of stardust would return to space to find the mysteries of where they came from .
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humans have observed comets for thousands of years as their orbits have brought them within visible distance of earth . appearing throughout historical records , these mysterious lights that came out of nowhere and disappeared after a short while were thought to be ill omens of war and famine , or the wrath of gods . but recent research has revealed that comets may be even more deeply connected to humanity and our presence on earth than any of these mythical explanations suggested . when you think of our solar system , you probably imagine the nine , sorry eight , planets orbiting the sun .
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ancient people viewed comets as omens of ______
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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 .
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brca1 belongs to a class of genes called _________ .
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oh , excuse me ! have you ever yawned because somebody else yawned ? you are n't especially tired , yet suddenly your mouth opens wide and a big yawn comes out . this phenomenon is known as contagious yawning . and while scientists still do n't fully understand why it happens , there are many hypotheses currently being researched . let 's take a look at a few of the most prevalent ones , beginning with two physiological hypotheses before moving to a psychological one . our first physiological hypothesis states that contagious yawning is triggered by a specific stimulus , an initial yawn . this is called fixed action pattern . think of fixed action pattern like a reflex . your yawn makes me yawn . similar to a domino effect , one person 's yawn triggers a yawn in a person nearby that has observed the act . once this reflex is triggered , it must run its course . have you ever tried to stop a yawn once it has begun ? basically impossible ! another physiological hypothesis is known as non-conscious mimicry , or the chameleon effect . this occurs when you imitate someone 's behavior without knowing it , a subtle and unintentional copycat maneuver . people tend to mimic each other 's postures . if you are seated across from someone that has their legs crossed , you might cross your own legs . this hypothesis suggests that we yawn when we see someone else yawn because we are unconsciously copying his or her behavior . scientists believe that this chameleon effect is possible because of a special set of neurons known as mirror neurons . mirror neurons are a type of brain cell that responds equally when we perform an action as when we see someone else perform the same action . these neurons are important for learning and self-awareness . for example , watching someone do something physical , like knitting or putting on lipstick , can help you do those same actions more accurately . neuroimaging studies using fmri , functional magnetic resonance imaging , show us that when we seem someone yawn or even hear their yawn , a specific area of the brain housing these mirror neurons tends to light up , which , in turn , causes us to respond with the same action : a yawn ! our psychological hypothesis also involves the work of these mirror neurons . we will call it the empathy yawn . empathy is the ability to understand what someone else is feeling and partake in their emotion , a crucial ability for social animals like us . recently , neuroscientists have found that a subset of mirror neurons allows us to empathize with others ' feelings at a deeper level . ( yawn ) scientists discovered this empathetic response to yawning while testing the first hypothesis we mentioned , fixed action pattern . this study was set up to show that dogs would enact a yawn reflex at the mere sound of a human yawn . while their study showed this to be true , they found something else interesting . dogs yawned more frequently at familiar yawns , such as from their owners , than at unfamiliar yawns from strangers . following this research , other studies on humans and primates have also shown that contagious yawning occurs more frequently among friends than strangers . in fact , contagious yawning starts occurring when we are about four or five years old , at the point when children develop the ability to identify others ' emotions properly . still , while newer scientific studies aim to prove that contagious yawning is based on this capacity for empathy , more research is needed to shed light on what exactly is going on . it 's possible that the answer lies in another hypothesis altogether . the next time you get caught in a yawn , take a second to think about what just happened . were you thinking about a yawn ? did someone near you yawn ? was that person a stranger or someone close ? and are you yawning right now ? ( yawn ) ( lip smacking )
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you are n't especially tired , yet suddenly your mouth opens wide and a big yawn comes out . this phenomenon is known as contagious yawning . and while scientists still do n't fully understand why it happens , there are many hypotheses currently being researched .
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research shows that contagious yawning starts when we are about
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throughout the history of mankind , three little words have sent poets to the blank page , philosophers to the agora , and seekers to the oracles : `` who am i ? '' from the ancient greek aphorism inscribed on the temple of apollo , `` know thyself , '' to the who 's rock anthem , `` who are you ? '' philosophers , psychologists , academics , scientists , artists , theologians and politicians have all tackled the subject of identity . their hypotheses are widely varied and lack significant consensus . these are smart , creative people , so what 's so hard about coming up with the right answer ? one challenge certainly lies with the complex concept of the persistence of identity . which you is who ? the person you are today ? five years ago ? who you 'll be in 50 years ? and when is `` am '' ? this week ? today ? this hour ? this second ? and which aspect of you is `` i '' ? are you your physical body ? your thoughts and feelings ? your actions ? these murky waters of abstract logic are tricky to navigate , and so it 's probably fitting that to demonstrate the complexity , the greek historian plutarch used the story of a ship . how are you `` i '' ? as the tale goes , theseus , the mythical founder king of athens , single-handedly slayed the evil minotaur at crete , then returned home on a ship . to honor this heroic feat , for 1000 years athenians painstakingly maintained his ship in the harbor , and annually reenacted his voyage . whenever a part of the ship was worn or damaged , it was replaced with an identical piece of the same material until , at some point , no original parts remained . plutarch noted the ship of theseus was an example of the philosophical paradox revolving around the persistence of identity . how can every single part of something be replaced , yet it still remains the same thing ? let 's imagine there are two ships : the ship that theseus docked in athens , ship a , and the ship sailed by the athenians 1000 years later , ship b . very simply , our question is this : does a equal b ? some would say that for 1000 years there has been only one ship of theseus , and because the changes made to it happened gradually , it never at any point in time stopped being the legendary ship . though they have absolutely no parts in common , the two ships are numerically identical , meaning one and the same , so a equals b . however , others could argue that theseus never set foot on ship b , and his presence on the ship is an essential qualitative property of the ship of theseus . it can not survive without him . so , though the two ships are numerically identical , they are not qualitatively identical . thus , a does not equal b . but what happens when we consider this twist ? what if , as each piece of the original ship was cast off , somebody collected them all , and rebuilt the entire original ship ? when it was finished , undeniably two physical ships would exist : the one that 's docked in athens , and the one in some guy 's backyard . each could lay claim to the title , `` the ship of theseus , '' but only would could actually be the real thing . so which one is it , and more importantly , what does this have to do with you ? like the ship of theseus , you are a collection of constantly changing parts : your physical body , mind , emotions , circumstances , and even your quirks , always changing , but still in an amazing and sometimes illogical way , you stay the same , too . this is one of the reasons that the question , `` who am i ? '' is so complex . and in order to answer it , like so many great minds before you , you must be willing to dive into the bottomless ocean of philosophical paradox . or maybe you could just answer , `` i am a legendary hero sailing a powerful ship on an epic journey . '' that could work , too .
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how are you `` i '' ? as the tale goes , theseus , the mythical founder king of athens , single-handedly slayed the evil minotaur at crete , then returned home on a ship . to honor this heroic feat , for 1000 years athenians painstakingly maintained his ship in the harbor , and annually reenacted his voyage .
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what did theseus do in crete before sailing home to athens ?
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in 1796 , thomas jefferson received a box of bones he could n't identify . a long , sharp claw reminded him of a lion , but the arm bones suggested a larger animal , one about three meters long . thinking it might be huge unknown species of north american lion , jefferson warned explorers lewis and clark to keep an eye out for this mysterious predator . but jefferson 's box of bones did n't come from a lion . they came from an extinct giant sloth . prehistoric ground sloths first appeared around 35 million years ago . dozens of species lived across north , central and south america , alongside other ancient creatures like mastodons and giant armadillos . some ground sloths , like the megalonychid , were cat-sized , but many were massive . jefferson 's sloth , megalonyx , weighed about a ton , and that was small compared to megatherium , which could reach six metric tons , as much as an elephant . they ambled through the forests and savannas using their strong arms and sharp claws to uproot plants and climb trees , grazing on grasses , leaves , and prehistoric avocados . in fact , we might not have avocados today if not for the giant sloths . smaller animals could n't swallow the avocado 's huge seed , but the sloths could , and they spread avocado trees far and wide . ground sloths flourished for millions of years , but around 10,000 years ago , they started disappearing along with the western hemisphere 's other giant mammals . researchers think that ground sloths could have been pushed out by an oncoming ice age , or competition with other species , maybe humans , who arrived in the region around the time most of the sloths went extinct . some of the smaller sloths did survive and migrated to the treetops . today , there are six species left living in the rainforest canopies of central and south america . hanging out in the trees is a good way to avoid predators , and there are plenty of leaves to eat . but this diet has its drawbacks . animals extract energy from food and use that energy to move around , maintain their body temperature , keep their organs working , and all the other activities necessary for survival . but leaves do n't contain much energy , and that which they do have is tough to extract . most herbivores supplement a leafy diet with higher energy foods like fruit and seeds . but sloths , especially three-toed sloths , rely on leaves almost exclusively . they 've evolved finely tuned strategies for coping with this restricted diet . first , they extract as much energy from their food as possible . sloths have a multi-chambered stomach that takes up a third of their body , and depending on the species , they can spend five to seven days , or even weeks , processing a meal . the other piece of the puzzle is to use as little energy as possible . one way sloths do this is , of course , by not moving very much . they spend most of their time eating , resting , or sleeping . they descend from the canopy just once a week for a bathroom break . when sloths do move , it 's not very fast . it would take a sloth about five minutes to cross an average neighborhood street . this unhurried approach to life means that sloths do n't need very much muscle . in fact , they have about 30 % less muscle mass than other animals their size . sloths also use less energy to keep themselves warm because their body temperature can fluctuate by about five degrees celsius , less than a cold-blooded reptile , but more than most mammals . these physical and behavioral adaptations minimize the sloth 's energy expenditure , or metabolic rate . three-toed sloths have the slowest metabolism of any mammal . the giant panda is second slowest , and two-toed sloths come in third . moving slowly has allowed sloths to thrive in their treetop habitat . but it 's also made the sloths themselves a great habitat for other organisms , including algae , which provides a little extra camouflage , and maybe even a snack . sloths may not be giant anymore , but that does n't make them any less remarkable .
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they ambled through the forests and savannas using their strong arms and sharp claws to uproot plants and climb trees , grazing on grasses , leaves , and prehistoric avocados . in fact , we might not have avocados today if not for the giant sloths . smaller animals could n't swallow the avocado 's huge seed , but the sloths could , and they spread avocado trees far and wide .
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how did giant ground sloths influence the survival and spread of avocados ?
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so we ’ re in the basement of the royal society in london . this is the uk academy of sciences . they have exhibitions here telling people about interesting things about science , and so we have come here because there ’ s a really interesting exhibit relevant to the work of lawrence who was the person after whom the element lawrencium was named after . lawrencium is another one of the elements right at the bottom of the periodic table which are really heavy , very radioactive . they fall to pieces very rapidly . so chemists are very , and physicists are very lucky if they just make a few atoms of this . so there ’ s nothing to tell you about the uses of lawrencium , because nobody ’ s made enough lawrencium to use it for anything , except as the subject of scientific papers and physical measurements . so instead i want to show you here a piece of equipment which is very similar to the sort of equipment that lawrence used when he was doing his pioneering work in berkeley , california , close to san francisco . so let ’ s go along here . lawrence was famous for inventing an instrument called the cyclotron which was for accelerating electrons to very high speeds . it was in fact the precursor of the large hadron collider which everybody ’ s now talking about . but he thought of it i think one day in the library in berkeley , and he imagined to begin with an instrument that was literally as big as my two hands here , a few inches across , and his idea was that if you made a vessel which was quite flat and circular not very high and put in it a big magnetic field the electrons could go round and round and round , and be accelerated to go faster and faster . the idea was that he made one and demonstrated the principle and he patented it and then he built bigger and bigger and bigger machines and as he made them , not only did the disc get bigger , but at the same time the magnet got bigger as well . and the final magnet that he made in berkeley , which was installed just before the second world war , was so large that a large part of his research group could sit between the poles of the magnet and it ’ s so heavy that the magnet is still there to this day . but come and look over here . this is a cyclotron that was built in cambridge . the first thing that strikes you is that it doesn ’ t look very exciting . it ’ s two copper discs , which are not actually connected together and the voltage is switched between one disc and the other so as the electron goes round when it gets to the end of one you switch the voltage so it goes on being accelerated and it goes round and round , and as it goes round in a magnetic field the faster it goes the bigger the circle . so it goes round and round and round in a larger and larger circle until the end it flies out of one of these tubes . i think again that it is important to say that some of these historic physics experiments , which are so important to both chemistry and physics , were done with equipment that really looks surprisingly simple and it is the really clever ideas that have been so important to physics and chemistry rather than always having enormously complicated apparatus . sometimes to take these ideas to their full extreme you do need complicated apparatus but that ’ s not the starting point . well i ’ ve read quite a bit about him . he was meant to be a very egotistical person and a real control freak , but my father-in-law worked in lawrence ’ s research group . when he was an english undergraduate he was sent to america during the second world war to work in lawrence ’ s group on the enrichment of uranium isotopes . that is , concentrating uranium-235 , the less-common isotope which was the basis for the atom bomb that was dropped on hiroshima . so john keane , my father-in-law , worked in the research group , i don ’ t know exactly what he did , but it ’ s really quite a sobering thought that during the second world war some of the brightest scientists had to work on these terrible projects really in order to save their countries . and let us hope that these such things never happen again .
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so chemists are very , and physicists are very lucky if they just make a few atoms of this . so there ’ s nothing to tell you about the uses of lawrencium , because nobody ’ s made enough lawrencium to use it for anything , except as the subject of scientific papers and physical measurements . so instead i want to show you here a piece of equipment which is very similar to the sort of equipment that lawrence used when he was doing his pioneering work in berkeley , california , close to san francisco .
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lawrencium is a radioactive element and all of its isotopes are unstable . what is the half-life of the longest-lived lawrencium isotope ?
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so today we ’ re going to look at bromine . so this is bromine , it ’ s a small sample , about 2 or 3 grammes . bromine is a red liquid . there are not many elements that are actually liquid : caesium , mercury , gallium and bromine . it ’ s this beautiful red colour and it has an unpleasant smell . bromine comes from the greek word bromos which means stench , a really horrible smell . in fact this bromine probably comes from near where i did my degree because in europe , the second , well the largest producer of bromine in europe is the octale company which is based on amlwch on anglesey which is where i went last weekend . so it ’ s a nice sample . we ’ re going to get it out of this bottle now because it ’ s sealed in because it ’ s obviously very , very volatile as a liquid and we ’ re going to cut the glass , get it out and look at its chemistry . thanks neil . bromine is also quite a common element in the world . it is found in sea water as bromide , it ’ s also found particularly in the dead sea between israel and jordan where there are very concentrated solutions of bromide . so you can make bromine just by bubbling chlorine into a solution of bromide like dead sea water and the chlorine displaces the bromine and forms chloride and the bromine just comes out as red fumes which you can catch . so neil ’ s now using a glass knife to open the ampoule and he ’ s going to pour the liquid bromine into this small evaporating dish inside our fume hood . now instantly you can see the vapour of the bromine coming off . you see all those really nice orange fumes which are coming off from the liquid and then they ’ re being drawn away by our fume hood . bromine has a number of uses , it is particularly used in plastics as an additive to try and make them less flammable . if you ’ re watching your videos on a screen which has a plastic surround almost certainly that surround will contain bromine to make it less flammable . bromine itself is strongly oxidising so we thought we ’ d do an oxidation reaction today . and that reaction is to take another element and here we have aluminium , simple aluminium foil , like you wrap your dinner in , and we ’ re now going to put some small amounts of aluminium foil into the bromine liquid . so we put it in and it generally takes a few moments for this reaction to start but as i said , the aluminium is strongly oxidising . it oxidises and generates aluminium tribromide . which is a beautiful nice material but it ’ s a strongly exothermic reaction . so let ’ s see what happens . this may initiate . it is also an unusual element because elements have different isotopes these are the same form of the element but with different numbers of neutrons in the atoms so they weigh different amounts . usually you get one isotope that is very common and another one that is only a small amount . bromine is unusual because it has two isotopes 79 and 81 which have almost equal quantities in nature so that they have approximately 51 % of one and 49 % of the other which is really quite unusual . so here we see the exothermic oxidation and formation of aluminium tribromide . so the reaction is strongly exothermic which means it gives out energy and that energy then evaporates off excess bromine which you can see coming off as a vapour . a wonderful exothermic reaction : very , very fast , very , very rapid forming aluminium tribromide . bromine is quite dangerous but it is less dangerous than chlorine because it ’ s a liquid at room temperature . chlorine is a gas so if you let out chlorine it disperses everywhere . with bromine it is a heavy gas which can disperse rather more slowly . so now as the reaction cools down we can see that the volume of bromine is significantly reduced . reacts with water quite well .
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thanks neil . bromine is also quite a common element in the world . it is found in sea water as bromide , it ’ s also found particularly in the dead sea between israel and jordan where there are very concentrated solutions of bromide . so you can make bromine just by bubbling chlorine into a solution of bromide like dead sea water and the chlorine displaces the bromine and forms chloride and the bromine just comes out as red fumes which you can catch .
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bromine is found in seawater as bromide , but where in the world can you find very concentrated solutions of bromide ?
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using the word shakespeare within any classroom in the 21st century has become almost as dangerous for teachers as putting balloons in a toaster . after uttering this simple word , the common teacher is met with a mass of groans , moans , devastated looks , and the occasional chair tossed in his or her direction . but shakespearean works are not boring , confusing , long and painful plays written more than 400 years ago . they 're adventures relating to the extremities of human nature : love , hate , jealousy , zealous ambition , fear , mistrust , deception , and murder . we owe much of our own language to his invention . he invented over 2,000 words for use in his plays , which still remain in the oxford english dictionary . words like `` countless '' and `` assassination '' as well as phrases like `` one fell swoop , '' `` foul play , '' and even `` to be in a pickle '' all originated from william 's brilliant brain . and there are many echoes of shakespeare 's romantic language too . if you read < em > romeo and juliet < /em > , you 'll come across sentences like , `` she doth teach the torches to burn bright , '' and , `` so shows a snowy dove trooping with crows . '' both are quite clever metaphors , suggesting that juliet is both exceptionally beautiful and far moreso than anyone else . `` for thou art as glorious to this night , being o'er my head , as is a winged messenger of heaven , '' is a simile suggesting angelic qualities of the lady in question . this is not too different from today 's comments like , `` hey , beautiful ! '' and , `` you 're the hottest girl in the room . '' shakespeare also uses slightly more complex metaphors to describe the intentions of a mischievous man . for instance , `` this holy shrine , the gentle sin is this : my lips , two blushing pilgrims , ready stand to smooth that rough touch with a tender kiss , '' essentially means , `` i wish to kiss you . '' such male intentions were not limited to simple pecks on the cheek either . an intentional ambiguity was often used as a cheeky means to proposition marriage or a more intimate relationship . therefore , instead of viewing shakespearean works as out-dated , boring , and unhelpful , start reading today and discover the best ways to get the one you love to love you back .
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after uttering this simple word , the common teacher is met with a mass of groans , moans , devastated looks , and the occasional chair tossed in his or her direction . but shakespearean works are not boring , confusing , long and painful plays written more than 400 years ago . they 're adventures relating to the extremities of human nature : love , hate , jealousy , zealous ambition , fear , mistrust , deception , and murder .
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shakespeare ’ s plays were written in the ________ .
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i ’ ve invited you all here today because i wanted to talk to you about some ugly stereotypes that are going around . i ’ ve been hearing a lot of unfair , unseemly , and unscientific generalizations being made lately . and they mostly have to do with sex . and your hormones . people have a nasty habit of equating “ hormones ” with a particular set of behaviors and conditions , most of which have to do with reproduction , or sexual development , or acts that include what my brother john has referred to as “ skoodilypooping. ” for example , people will say that “ hormones ” are why kevin has zits , and is being all moody , or why hannah , who ’ s three months pregnant , just cried watching a commercial for car insurance -- which , let ’ s be honest , i do that too . now , i ’ m not saying that hormones aren ’ t at the root of sexual attraction , or zits , or occasional bouts of extreme emotion , because they are . that ’ s just not all that they do . not even close . when people talk about “ hormones ” in the contexts that i just mentioned , what really they mean is `` sex hormones . '' but sex hormones are just one kind of hormone that you have coursing through your body right now . in fact , there are at least 50 different types of these chemical messengers at work in your body at this very minute , but only a very few of them have anything at all to do with sex . the truth is , from birth to death , just about every cell and function in your body is under your hormones ’ constant influence . they ’ re floating through your blood , regulating your metabolism , your sleep cycle , your response to stress , and the general and incredibly important overall homeostasis that keeps you not dead . some hormones are just there to make other hormones trigger even more hormones -- in a kind of chemical relay race that biologists refer to , rather elegantly , as “ cascades. ” these hormones run through you no matter what your mood is , or whether you have zits . so the reality is : we ’ re all hormonal ... all of the time . ok , to begin to understand our hormones -- and the endocrine system that produces , releases , and re-absorbs them -- we have to step back and take a broad view . not just by emphasizing that sex hormones aren ’ t the only hormones you have -- but also by looking at how your hormones interact with your other organ systems . because , if anything , your body has two bosses -- two complementary systems that are constantly shouting instructions over each other , to all of your bits and pieces . both your endocrine system and your nervous system are constantly trafficking information around your corpus , gathering intel , making demands , controlling your every move . they just have totally different ways of doing it . your nervous system uses lightning-fast electrochemical action potentials , delivered by an expressway made of neurons to specific cells and organs . but your endocrine system prefers a slower , wider stream of data . it secretes hormones that travel through your blood -- not through neurons -- so they move more slowly , but they also produce widespread effects that last a whole lot longer than an action potential . now , compared to your heart or brain or other , arguably more glamorous organs , your endocrine system ’ s organs and glands are kinda small and lumpy . they ’ re also rogues -- instead of being all nestled together like in your other organ systems , these guys are scattered all over the place , from your brain to your throat , to your kidneys , to your genitals . a gland is a just any structure that makes and secretes a hormone . and the master gland in your body is the pituitary , which produces many hormones that signal other glands -- like the thyroid , parathyroid , adrenal , and pineal glands -- to make their own hormones . the endocrine system also includes a few organs -- like the gonads , the pancreas , and the placenta in pregnant women -- all of which have some other non-hormonal functions and are made up of multiple tissue types . and technically the hypothalamus in your brain is in the endocrine club too , since in addition to all of its busy brain duties , it does produce and release hormones . so , thanks to these glands and organs , you ’ ve got all these hormones diffusing through your blood , doing all sorts of different things , but the thing to remember about them is that a hormone can only trigger a reaction in specific cells -- their so-called target cells -- that have the right receptors for it . so , just like some keys can open many locks , while others only work with one , so too can the hormone-target-cell relationship either be widespread or localized . you ’ re probably gon na want an example of that . so , your thyroid -- at the bottom of your throat -- produces the hormone thyroxine , which stimulates metabolism and binds to receptors in most of the cells in your body . but your pituitary -- which is nestled all comfy under your brain -- produces follicle-stimulating hormone , which helps regulate growth and triggers sexual maturity , and it only targets specific cells in the ovaries and testes . so how do hormones bind to their target cells ? well , chemically , most hormones are either made of amino acids -- including their more complex structures like peptides or proteins -- or they ’ re derived from lipids , like cholesterol . and this is key , because a hormone ’ s chemical structure determines if it ’ s water soluble , like most amino acid-based ones are , or lipid soluble , like steroids are . solubility is important because your cell membranes are made of lipids . that means that water soluble ones can ’ t get across them . so target cells for those kinds of hormones have receptors for them on the outside of their membranes . lipid-soluble hormones , on the other hand , can just basically glide right through that cell membrane , so their receptor sites are inside their target cells . either way , when a target cell is activated , the hormone alters its activity , by either increasing or decreasing some of its functions -- usually with the goal of maintaining your body ’ s homeostasis in one way or another . so , if hormones are keeping your body in balance , what ’ s putting your body out of balance ? i don ’ t know -- could i interest you in some pie ? if you have a couple of nice , generous helpings of strawberry-rhubarb pie -- and just to make things interesting , let ’ s say they ’ re a la mode -- your blood glucose level is gon na go through the roof . and the pancreas regulates your blood sugar by releasing two different hormones -- insulin and glucagon . once you have a belly full of that pie , beta cells in your pancreas release insulin , which helps lower your blood sugar by increasing the rate at which your cells store the sugar either as glycogen or as fat for later use . now , let ’ s say you ’ ve done the opposite : you ’ ve eaten no pie -- you ’ re pie-less -- in fact , you ’ ve eaten nothing for hours . if your blood sugar drops too low , then alpha cells in the pancreas will instead send out glucagon , which helps raise your blood sugar levels , in part by decreasing the storage of sugar in your cells , and triggering their release of glucose back into the blood . lots of different endocrine-related illnesses -- like diabetes or hyperthyroidism -- tend to be the result of either hyper ( too much ) or hypo ( too little ) secretion of certain hormones , which throw your homeostasis off balance . but there are lots of more common -- and less obvious -- ways your hormones can get out of balance , not because of some disorder , but because these signaling chemicals are just caught up in a chain reaction , which can take a while to subside . some hormones just exist to control other hormones , which in turn control still more hormones . so as soon as one starts to trickle out , you can pretty quickly wind up with a cascade on your hands . you ’ ve got a few different hormone cascades going on at any given moment , but one of the big ones -- one that ’ s really worth understanding -- is the hypothalamic-pituitary-adrenal axis , or the hpa axis , because you don ’ t want to have to say that every time . this is a complex series of interactions between three glands that ultimately regulates lots of your body ’ s daily processes , like digestion , sexuality , immune response , and how you handle stress . and it ’ s complex not just because of all the glands involved -- it ’ s also one of the more crucial instances of your endocrine system coordinating with your nervous system . specifically , it ’ s behind that fight-or-flight response that everybody keeps talking about . the hpa axis is essentially the endocrine system ’ s companion to the sympathetic nervous system . the sympathetic system , in times of high stress , does things like speed up your heart rate and direct blood away from the digestive organs and to the muscles . but many of the other effects of the stress response are carried out by your endocrine system . and getting your nervous and endocrine systems to work together in times of crisis is where the hypothalamus comes in . it ’ s the hub of where the two systems meet -- it keeps tabs on what ’ s going on all over your body , analyzing your blood for signs that something might be off . so , let ’ s revisit our fight-or-flight scene from a few lessons ago -- the old burning house scenario . so you ’ re sleeping , dreaming about petting pandas with emma watson or whatever , when the smoke alarm goes off . well , action potentials in your brain trigger neurons in your hypothalamus to release the peptide hormone crh , or corticotropin releasing hormone . the crh makes the very short trip through the bloodstream to the anterior pituitary gland , where , because it ’ s water soluble , it binds to receptors on the outside of its target cells . there , it triggers the release of adrenocorticotropic hormone , or acth . the acth travels -- again through the bloodstream -- to the adrenal cortices of the adrenal glands on top of your kidneys . when the acth binds to receptors on cells in an adrenal cortex , it triggers the release of a frenzy of different freak-out compounds known as glucocorticoid and mineralcorticoid hormones . typically these guys help us deal with day-to-day stress by keeping our blood sugar and blood pressure balanced . but under major stress -- like waking up in a burning building stress -- these hormones , like cortisol , cause the classic fight-or-flight response : ramping up your blood pressure , dumping glucose into your bloodstream , shutting down non-emergency services like your immune system and sperm and egg development . and guess what ? now that all these stress hormones are pulsing through your blood , the hypothalamus back in the brain senses them . and because its job is to monitor and maintain balance whenever possible , it then stops secreting crh , which -- eventually -- causes the other glands to stop secreting their panic hormones . now , because this element of the stress response is hormonal rather than electrical , it comes on more slowly than the nervous system part , and it takes longer to subside , too , as those stress hormones linger in the blood before being broken down by enzymes . so . we ’ re a long way from teenage crushes and zits and crying over commercials at this point , aren ’ t we ? as a life-long owner of hormones , i hope you ’ ll join me in dispelling the stereotypes that surround these powerful and important chemicals , and give them the respect they rightly deserve . today we looked at the endocrine system , and how it uses glands to produce hormones . these hormones are either amino-acid based and water soluble , or steroidal and lipid-soluble , and may target many types of cells or just turn on specific ones . we also touched on hormone cascades , and how the hpa axis effects your stress response . thank you to our headmaster of learning , thomas frank , and to all of our patreon patrons who help make crash course possible through their monthly contributions . if you like crash course and you want to help us keep making free educational content for the whole world , you can go to patreon.com/crashcourse . crash course is filmed in the doctor cheryl c. kinney crash course studio . this episode was written by kathleen yale , edited by blake de pastino , and our consultant is dr. brandon jackson . it was directed by nicholas jenkins , the editor is nicole sweeney , the script supervisor was stefan chin , our sound designer is michael aranda and the graphics team is thought café .
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so you ’ re sleeping , dreaming about petting pandas with emma watson or whatever , when the smoke alarm goes off . well , action potentials in your brain trigger neurons in your hypothalamus to release the peptide hormone crh , or corticotropin releasing hormone . the crh makes the very short trip through the bloodstream to the anterior pituitary gland , where , because it ’ s water soluble , it binds to receptors on the outside of its target cells .
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what hormone does the thyroid produce and what function does that hormone serve ?
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would mathematics exist if people did n't ? since ancient times , mankind has hotly debated whether mathematics was discovered or invented . did we create mathematical concepts to help us understand the universe around us , or is math the native language of the universe itself , existing whether we find its truths or not ? are numbers , polygons and equations truly real , or merely ethereal representations of some theoretical ideal ? the independent reality of math has some ancient advocates . the pythagoreans of 5th century greece believed numbers were both living entities and universal principles . they called the number one , `` the monad , '' the generator of all other numbers and source of all creation . numbers were active agents in nature . plato argued mathematical concepts were concrete and as real as the universe itself , regardless of our knowledge of them . euclid , the father of geometry , believed nature itself was the physical manifestation of mathematical laws . others argue that while numbers may or may not exist physically , mathematical statements definitely do n't . their truth values are based on rules that humans created . mathematics is thus an invented logic exercise , with no existence outside mankind 's conscious thought , a language of abstract relationships based on patterns discerned by brains , built to use those patterns to invent useful but artificial order from chaos . one proponent of this sort of idea was leopold kronecker , a professor of mathematics in 19th century germany . his belief is summed up in his famous statement : `` god created the natural numbers , all else is the work of man . '' during mathematician david hilbert 's lifetime , there was a push to establish mathematics as a logical construct . hilbert attempted to axiomatize all of mathematics , as euclid had done with geometry . he and others who attempted this saw mathematics as a deeply philosophical game but a game nonetheless . henri poincaré , one of the father 's of non-euclidean geometry , believed that the existence of non-euclidean geometry , dealing with the non-flat surfaces of hyperbolic and elliptical curvatures , proved that euclidean geometry , the long standing geometry of flat surfaces , was not a universal truth , but rather one outcome of using one particular set of game rules . but in 1960 , nobel physics laureate eugene wigner coined the phrase , `` the unreasonable effectiveness of mathematics , '' pushing strongly for the idea that mathematics is real and discovered by people . wigner pointed out that many purely mathematical theories developed in a vacuum , often with no view towards describing any physical phenomena , have proven decades or even centuries later , to be the framework necessary to explain how the universe has been working all along . for instance , the number theory of british mathematician gottfried hardy , who had boasted that none of his work would ever be found useful in describing any phenomena in the real world , helped establish cryptography . another piece of his purely theoretical work became known as the hardy-weinberg law in genetics , and won a nobel prize . and fibonacci stumbled upon his famous sequence while looking at the growth of an idealized rabbit population . mankind later found the sequence everywhere in nature , from sunflower seeds and flower petal arrangements , to the structure of a pineapple , even the branching of bronchi in the lungs . or there 's the non-euclidean work of bernhard riemann in the 1850s , which einstein used in the model for general relativity a century later . here 's an even bigger jump : mathematical knot theory , first developed around 1771 to describe the geometry of position , was used in the late 20th century to explain how dna unravels itself during the replication process . it may even provide key explanations for string theory . some of the most influential mathematicians and scientists of all of human history have chimed in on the issue as well , often in surprising ways . so , is mathematics an invention or a discovery ? artificial construct or universal truth ? human product or natural , possibly divine , creation ? these questions are so deep the debate often becomes spiritual in nature . the answer might depend on the specific concept being looked at , but it can all feel like a distorted zen koan . if there 's a number of trees in a forest , but no one 's there to count them , does that number exist ?
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one proponent of this sort of idea was leopold kronecker , a professor of mathematics in 19th century germany . his belief is summed up in his famous statement : `` god created the natural numbers , all else is the work of man . '' during mathematician david hilbert 's lifetime , there was a push to establish mathematics as a logical construct .
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what mathematician believed that `` god created the natural numbers ... all else is the work of man '' ?
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among the great poets of literary history , certain names like homer , shakespeare , milton , and whitman are instantly recognizable . however , there 's an early 20th century great french poet whose name you may not know : guillaume apollinaire . he was a close friend and collaborator of artists like picasso , rousseau , and chagall . he coined the term surrealism , and he was even suspected of stealing the mona lisa in 1911 . during his short lifetime , he created poetry that combined text and image in a way that seemingly predicted an artistic revolution to come . in the late 19th and early 20th century paris , the low-rent districts of montmartre and montparnasse were home to every kind of starving artist . it was all they could afford . these painters , writers , and intellectuals , united in their artistic passion and counterculture beliefs , made up france 's bohemian subculture . and their works of art , literature , and intellect would shake up the world . at the turn of the 20th century , within this dynamic scene , art critic , poet , and champion of the avant-garde , guillaume apollinaire was a well-known fixture . as an art critic , apollinaire explained the cubist and surrealist movements to the world , and rose to the defense of many young artists in the face of what was often a xenophobic and narrow-minded public . as a poet , apollinaire was passionate about all forms of art and a connoisseur of medieval literature , especially calligraphy and illuminated initials . as a visionary , apollinaire saw a gap between two artistic institutions . on one side was the popular , highly lauded traditional art forms of the time . on the other , the forms of artistic expression made possible through surrealism , cubism , and new inventions , like the cinema and the phonograph . within that divide , through the creation of his most important contribution to poetry , the calligram , guillaume apollinaire built a bridge . apollinaire created the calligram as a poem picture , a written portrait , a thoughts drawing , and he used it to express his modernism and his desire to push poetry beyond the normal bounds of text and verse and into the 20th century . some of his calligrams are funny , like the `` lettre-océan . '' some of them are dedicated to his young dead friends , like `` la colombe poignardée et le jet d'eau . '' some of them are the expression of an emotional moment , as is `` il pleut '' : `` it 's raining women 's voices as if they had died even in memory , and it 's raining you as well , marvellous encounters of my life , o little drops . those rearing clouds begin to neigh a whole universe of auricular cities . listen if it rains while regret and disdain weep to an ancient music . listen to the bonds fall off which hold you above and below . '' each calligram is intended to allow readers to unchain themselves from the regular experience of poetry , and feel and see something new . `` lettre-océan '' is first an image to be seen before even the words are read . text-only elements combine with words in shapes and forms . two circular forms , one locked in a square , the other , morph beyond the page in the shape of a spiral . together they create a picture that hints towards cubism . then on closer reading of the text , the descriptive words within suggest the image of an aerial view of the eiffel tower . they give tribute to electromagnetic waves of the telegraph , a new form of communication at the time . undoubtedly , the deeply layered artistic expressions in apollinaire 's calligrams are not just a brilliant display of poetic prowess from a master of the form . each calligram itself is also a snapshot in time , encapsulating the passion , the excitement , and the anticipation of all the bohemian artists of paris , including apollinaire , most of whom are well ahead of their time , and with their innovative work , eagerly grasping for the future .
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among the great poets of literary history , certain names like homer , shakespeare , milton , and whitman are instantly recognizable . however , there 's an early 20th century great french poet whose name you may not know : guillaume apollinaire . he was a close friend and collaborator of artists like picasso , rousseau , and chagall .
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guillaume apollinaire wanted to push the “ quest of another reality. ” this is not defined by science and reason , so he created a new word :
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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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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 .
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are there particularly important crops that you think should be protected especially from the effects of colony collapse disorder ?
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our story is about a girl named iris . iris is very sensitive . ( bird cawing ) so much that she is always in tears . she cries when she 's sad , when she 's happy , ( godzilla roars ) and even tears up when things just get to her . she has special lacrimal glands to make new tears and special tubes , called lacrimal puncta , to drain old ones away . and she cries so much that she goes through ten ounces of tears per day , thirty gallons a year ! in fact , if you look closely , you 'll see that she 's crying a little bit all the time . the basal tears that iris constantly produces form a thin coating of three layers that cover her and keep dirt and debris away . right next to iris is the mucus layer , which keeps the whole thing fastened to her . on top of it is the aqueous layer , which keeps iris hydrated , repels invasive bacteria , and protects her skin , or cornea , from damage . and , finally , there is the lipid layer , an oily outer film that keeps the surface smooth for iris to see through , and prevents the other layers from evaporating . normally , iris goes about her day without really noticing the basal tears doing their thing . that 's kind of their whole point . but one day , she meets a girl named onion . iris is immediately smitten . onion looks gorgeous in her bright purple jacket , and she smells terrific . so , iris invites onion to her house for dinner . but when she comes in and takes off her jacket , something terrible happens . you see , when onion 's jacket is removed , a chemical reaction happens , converting the sulfoxides that make her smell so great into sulfenic acid , which then becomes a nasty substance with a long name : syn-propanethial s-oxide . the gas stings iris , and suddenly , she ca n't help it , she starts weeping uncontrollably . these reflex tears are different from the basal tears that iris is used to . because they 're designed to wash away harmful substances , or particles , they 're released in much larger amounts , and their aqueous layer contains more antibodies to stop any microorganisms that may be trying to get in , as well . both iris and onion are devastated . they know they ca n't continue their relationship if iris is going to hurt and cry every time onion takes off her jacket . so , they decide to break up . as onion walks out the door , iris stops crying . and immediately starts again . only now , she 's not crying reflex tears but emotional tears . when someone is either too sad or too happy , it feels like a loss of control , which can be dangerous . so , emotional tears are sent in to stabilize the mood as quickly as possible , along with other physical reactions , such as an increased heart rate and slower breathing . but scientists still are n't sure exactly how or why the tears themselves are helpful . they may be a social mechanism to elicit sympathy or show submission . but some studies have also found that emotional tears contain higher levels of stress hormones , such as acth and enkephalin , an endorphin and natural pain killer . in this case , emotional tears are also directly calming iris down , as well as signaling her emotional state to others . sorry things did n't work out with onion , iris , but do n't worry . as long as you have all three kinds of tears working to keep you balanced and healthy , it will get better . you 'll see .
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the basal tears that iris constantly produces form a thin coating of three layers that cover her and keep dirt and debris away . right next to iris is the mucus layer , which keeps the whole thing fastened to her . on top of it is the aqueous layer , which keeps iris hydrated , repels invasive bacteria , and protects her skin , or cornea , from damage . and , finally , there is the lipid layer , an oily outer film that keeps the surface smooth for iris to see through , and prevents the other layers from evaporating . normally , iris goes about her day without really noticing the basal tears doing their thing .
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why does the lipid layer exist ?
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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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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 .
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when was colony collapse disorder found to affect over half the commercial hives in the united states ?
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translator : andrea mcdonough reviewer : bedirhan cinar as any current or past geometry student knows , the father of geometry was euclid , a greek mathematician who lived in alexandria , egypt , around 300 b.c.e . euclid is known as the author of a singularly influential work known as `` elements . '' you think your math book is long ? euclid 's `` elements '' is 13 volumes full of just geometry . in `` elements , '' euclid structured and supplemented the work of many mathematicians that came before him , such as pythagoras , eudoxus , hippocrates and others . euclid laid it all out as a logical system of proof built up from a set of definitions , common notions , and his five famous postulates . four of these postulates are very simple and straightforward , two points determine a line , for example . the fifth one , however , is the seed that grows our story . this fifth mysterious postulate is known simply as the parallel postulate . you see , unlike the first four , the fifth postulate is worded in a very convoluted way . euclid 's version states that , `` if a line falls on two other lines so that the measure of the two interior angles on the same side of the transversal add up to less than two right angles , then the lines eventually intersect on that side , and therefore are not parallel . '' wow , that is a mouthful ! here 's the simpler , more familiar version : `` in a plane , through any point not on a given line , only one new line can be drawn that 's parallel to the original one . '' many mathematicians over the centuries tried to prove the parallel postulate from the other four , but were n't able to do so . in the process , they began looking at what would happen logically if the fifth postulate were actually not true . some of the greatest minds in the history of mathematics ask this question , people like ibn al-haytham , omar khayyam , nasir al-din al-tusi , giovanni saccheri , jános bolyai , carl gauss , and nikolai lobachevsky . they all experimented with negating the parallel postulate , only to discover that this gave rise to entire alternative geometries . these geometries became collectively known as non-euclidean geometries . we 'll leave the details of these different geometries for another lesson . the main difference depends on the curvature of the surface upon which the lines are constructed . turns out euclid did not tell us the entire story in `` elements , '' and merely described one possible way to look at the universe . it all depends on the context of what you 're looking at . flat surfaces behave one way , while positively and negatively curved surfaces display very different characteristics . at first these alternative geometries seemed strange , but were soon found to be equally adept at describing the world around us . navigating our planet requires elliptical geometry while the much of the art of m.c . escher displays hyperbolic geometry . albert einstein used non-euclidean geometry as well to describe how space-time becomes warped in the presence of matter , as part of his general theory of relativity . the big mystery is whether euclid had any inkling of the existence of these different geometries when he wrote his postulate . we may never know , but it 's hard to believe he had no idea whatsoever of their nature , being the great intellect that he was and understanding the field as thoroughly as he did . maybe he did know and he wrote the postulate in such a way as to leave curious minds after him to flush out the details . if so , he 's probably pleased . these discoveries could never have been made without gifted , progressive thinkers able to suspend their preconceived notions and think outside of what they 've been taught . we , too , must be willing at times to put aside our preconceived notions and physical experiences and look at the larger picture , or we risk not seeing the rest of the story .
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the fifth one , however , is the seed that grows our story . this fifth mysterious postulate is known simply as the parallel postulate . you see , unlike the first four , the fifth postulate is worded in a very convoluted way .
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which of the following mathematicians is not known for having worked on negating the parallel postulate ?
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you 're the realm 's greatest mathematician , but ever since you criticized the emperor 's tax laws , you 've been locked in the dungeon with only a marker to count the days . but one day , you 're suddenly brought before the emperor who looks even angrier than usual . one of his twelve governors has been convicted of paying his taxes with a counterfeit coin which has already made its way into the treasury . as the kingdom 's greatest mathematician , you 've been granted a chance to earn your freedom by identifying the fake . before you are the twelve identical looking coins and a balance scale . you know that the false coin will be very slightly lighter or heavier than the rest . but the emperor 's not a patient man . you may only use the scale three times before you 'll be thrown back into the dungeon . you look around for anything else you can use , but there 's nothing in the room - just the coins , the scale , and your trusty marker . how do you identify the counterfeit ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 obviously you ca n't weigh each coin against all of the others , so you 'll have to weigh several coins at the same time by splitting the stack into multiple piles then narrowing down where the false coin is . start by dividing the twelve coins into three equal piles of four . placing two of these on the scale gives us two possible outcomes . if the two sides balance , all eight coins on the scale are real , and the fake must be among the remaining four . so how do you keep track of these results ? that 's where the marker comes in . mark the eight authentic coins with a zero . now , take three of them and weigh them against three unmarked coins . if they balance , the remaining unmarked coin must be the fake . if they do n't , draw a plus on the three unmarked coins if they 're heavier or a minus if they 're lighter . now , take two of the newly marked coins and weigh them against each other . if they balance , the third coin is fake . otherwise , look at their marks . if they are plus coins , the heavier one is the imposter . if they are marked with minus , it 's the lighter one . but what if the first two piles you weigh do n't balance ? mark the coins on the heavier side with a plus and those on the lighter side with a minus . you can also mark the remaining four coins with zeros since you know the fake one is already somewhere on the scale . now , you 'll need to think strategically so you can remove all remaining ambiguity in just two more weighings . to do this , you 'll need to reassemble the piles . one method is to replace three of the plus coins with three of the minus coins , and replace those with three of the zero coins . > from here , you have three possibilities . if the previously heavier side of the scale is still heavier , that means either the remaining plus coin on that side is actually the heavier one , or the remaining minus coin on the lighter side is actually the lighter one . choose either one of them , and weigh it against one of the regular coins to see which is true . if the previously heavier side became lighter , that means one of the three minus coins you moved is actually the lighter one . weigh two of them against each other . if they balance , the third is counterfeit . if not , the lighter one is . similarly , if the two sides balanced after your substitution , then one of the three plus coins you removed must be the heavier one . weigh two of them against each other . if they balance , the third one is fake . if not , then it 's the heavier one . the emperor nods approvingly at your finding , and the counterfeiting lord takes your place in the dungeon .
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if they balance , the third coin is fake . otherwise , look at their marks . if they are plus coins , the heavier one is the imposter . if they are marked with minus , it 's the lighter one .
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if you know that among four otherwise identical coins one is heavier than the others , what is the minimum number of weighs you would need to uncover the single counterfeit coin ?
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if you 've ever floated on an ocean swell , you 'll know that the sea moves constantly . zoom out , and you 'll see the larger picture : our earth , covered by 71 percent water , moving in one enormous current around the planet . this intimidating global conveyor belt has many complicated drivers , but behind it all is a simple pump that moves water all over the earth . the process is called thermohaline circulation , and it 's driven by a basic concept : the concentration gradient . let 's leave the ocean for one moment and imagine we 're in an empty room with lots of roombas sardined together in one corner . turn them all on at once and the machines glide outwards bumping into and away from each other until the room is filled with an evenly spaced distribution . the machines have moved randomly towards equilibrium , a place where the concentration of a substance is equally spread out . that 's what happens along a concentration gradient , as substances shift passively from a high , or squashed , concentration , to a lower , more comfortable one . how does this relate to ocean currents and thermohaline circulation ? thermo means temperature , and haline means salt because in the real world scenario of the sea , temperature and salinity drive the shift from high to low concentrations . let 's put you back in the ocean to see how this works . snap ! you 're transformed into a molecule of surface water , off the temperate coast of new york surrounded by a zillion rowdy others . here , the sun 's rays act as an energizer that set you and the other water molecules jostling about , bouncing off each other like the roombas did . the more you spread out , the less concentrated the water molecules at the surface become . through this passive motion , you move from a high to a lower concentration . let 's suspend the laws of physics for a moment , and pretend that your molecular self can plunge deep down into the water column . in these colder depths , the comparative lack of solar warmth makes water molecules sluggish , meaning they can sit quite still at high concentrations . no jostling here . but seeking relief from the cramped conditions they 're in , they soon start moving upwards towards the roomier situation at the surface . this is how temperature drives a shift of water molecules from high to low concentrations , towards equilibrium . but sea water is made up of more than just h2o . there are a great deal of salt ions in it as well . and like you , these guys have a similar desire for spacious real estate . as the sun warms the sea , some of your fellow water molecules evaporate from the surface , increasing the ration of salt to h2o . the crowded salt ions left behind notice that lower down , salt molecules seem to be enjoying more space . and so an invasion begins , as they too move downwards in the water column . in the polar regions , we see how this small local process effects global movement . in the arctic and antarctic , where ice slabs decorate the water 's surface , there 's little temperature difference between surface and deeper waters . it 's all pretty cold . but salinity differs , and in this scenario , that 's what triggers the action . here , the sun 's rays melt surface ice , depositing a new load of water molecules into the sea . that not only increases the proximity between you and other water molecules , leaving you vying for space again , but it also conversely dilutes the concentration of salt ions . so , down you go , riding along the concentration gradient towards more comfortable conditions . for salt ions , however , their lower concentration at the surface , acts like an advertisement to the clamoring masses of salt molecules below who begin their assent . in both temperate and polar regions , this passive motion along a concentration gradient , can get a current going . and that is the starting point of the global conveyor called thermohaline circulation . this is how a simple concept becomes the mechanism underlying one of the largest and most important systems on our planet . and if you look around , you 'll see it happening everywhere . turn on a light , and it 's there . concentration gradients govern the flow of electricity , allowing electrons squashed together in one space to travel to an area of lower concentration when a channel is opened , which you do by flipping a switch . right now , in fact , there 's some gradient action going on inside you as you breath air into your lungs letting the concentrated oxygen in that air move passively out of your lungs and into your blood stream . we know that the world is filled with complex physical problems , but sometimes the first step towards understanding them can be simple . so when you confront the magnitude of the ocean 's currents , or have to figure out how electricity works , remember not to panic . understanding can be as simple as flipping a switch .
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but seeking relief from the cramped conditions they 're in , they soon start moving upwards towards the roomier situation at the surface . this is how temperature drives a shift of water molecules from high to low concentrations , towards equilibrium . but sea water is made up of more than just h2o .
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are water molecules in cold water moving rapidly ?
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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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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 .
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you would need 7 million times more people than are currently on earth in order to what ?
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translator : andrea mcdonough reviewer : bedirhan cinar when we think about learning , we often picture students in a classroom or lecture hall , books open on their desks , listening intently to a teacher or professor in the front of the room . but in psychology , learning means something else . to psychologists , learning is a long-term change in behavior that 's based on experience . two of the main types of learning are called classical conditioning and operant , or instrumental , conditioning . let 's talk about classical conditioning first . in the 1890 's , a russian physiologist named ivan pavlov did some really famous experiments on dogs . he showed dogs some food and rang a bell at the same time . after a while , the dogs would associate the bell with the food . they would learn that when they heard the bell , they would get fed . eventually , just ringing the bell made the dogs salivate . they learned to expect food at the sound of a bell . you see , under normal conditions , the sight and smell of food causes a dog to salivate . we call the food an unconditioned stimulus , and we call salivation the unconditioned response . nobody trains a dog to salivate over some steak . however , when we pair an unconditioned stimulus like food with something that was previously neutral , like the sound of a bell , that neutral stimulus becomes a conditioned stimulus . and so classical conditioning was discovered . we see how this works with animals , but how does it work with humans ? in exactly the same way . let 's say that one day you go to the doctor to get a shot . she says , `` do n't worry , this wo n't hurt a bit , '' and then gives you the most painful shot you 've ever had . a few weeks later you go to the dentist for a check-up . he starts to put a mirror in your mouth to examine your teeth , and he says , `` do n't worry , this wo n't hurt a bit . '' even though you know the mirror wo n't hurt , you jump out of the chair and run , screaming from the room . when you went to get a shot , the words , `` this wo n't hurt a bit , '' became a conditioned stimulus when they were paired with pain of the shot , the unconditioned stimulus , which was followed by your conditioned response of getting the heck out of there . classical conditioning in action . operant conditioning explains how consequences lead to changes in voluntary behavior . so how does operant conditioning work ? there are two main components in operant conditioning : reinforcement and punishment . reinforcers make it more likely that you 'll do something again , while punishers make it less likely . reinforcement and punishment can be positive or negative , but this does n't mean good and bad . positive means the addition of a stimulus , like getting dessert after you finish your veggies , and negative means the removal of a stimulus , like getting a night of no homework because you did well on an exam . let 's look at an example of operant conditioning . after eating dinner with your family , you clear the table and wash the dishes . when you 're done , your mom gives you a big hug and says , `` thank you for helping me . '' in this situation , your mom 's response is positive reinforcement if it makes you more likely to repeat the operant response , which is to clear the table and wash the dishes . operant conditioning is everywhere in our daily lives . there are n't many things we do that have n't been influenced at some point by operant conditioning . we even see operant conditioning in some extraordinary situations . one group of scientists showed the power of operant conditioning by teaching pigeons to be art connoisseurs . using food as a positive reinforcer , scientists have taught pigeons to select paintings by monet over those by picasso . when showed works of other artists , scientists observed stimulus generalization as the pigeons chose the impressionists over the cubists . maybe next they 'll condition the pigeons to paint their own masterpieces .
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translator : andrea mcdonough reviewer : bedirhan cinar when we think about learning , we often picture students in a classroom or lecture hall , books open on their desks , listening intently to a teacher or professor in the front of the room . but in psychology , learning means something else . to psychologists , learning is a long-term change in behavior that 's based on experience . two of the main types of learning are called classical conditioning and operant , or instrumental , conditioning .
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to psychologists , learning is :
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why do humans drink so much milk ? and given that all mammals lactate , why do we favor certain types of milk over others ? milk is the first thing we drink , and thanks to developments in the production and variety of dairy products , it can take on countless forms for our dietary and sensory well-being . milk 's primary function is as a complete source of nutrition for newborns . in fact , since it has all of the vital nutrients for development and growth , proteins , carbohydrates , fats , vitamins and minerals , and water , milk is the only thing a baby even needs to ingest for the first six months of life . the unique makeup of milk can vary depending on factors like species , diet , and location . reindeer of the arctic circle , for example , make energy-dense milk that 's about 20 % fat , roughly five times more than human or cow 's milk , to help their young survive the harsh , freezing climate . so how is milk made ? in the uniquely mammalian process of lactation , a special class of milk-secreting cells known as mammocytes line up in a single layer around pear-shaped alveoli . those cells absorb all of the building blocks of milk , then synthesize tiny droplets of fat on structures called smooth endoplasmic reticula . the droplets combine with each other and other molecules and are then expelled and stored in spaces between cells . mammary glands eventually secrete the milk through the breasts , udders , or , in the rare case of the platypus , through ducts in the abdomen . although this process is typically reserved for females , in some species , like dayak fruit bats , goats , and even cats , males can also lactate . milk drinkers worldwide consume dairy from buffalo , goats , sheeps , camels , yaks , horses , and cows . almost all of these species are ruminants , a type of mammal with four-chambered stomachs that yield large quantities of milk . of these , cows were the most easily domesticated and produce a milk that is both easily separated into cream and liquid and has a similar fat content to human milk . in their natural environment , mammals secrete milk on call for immediate consumption by their young . but with the demands of thirsty consumers , the dairy industry has enlisted methods to step up production , enhance shelf life , and provide a variety of milk products . in the dairy , centrifugation machines spin milk at high speeds , forcing less dense fats to separate from the liquid and float up . after being skimmed off , this fat , known as butterfat , can be used in dairy products like butter , cream , and cheese . or it can be later added back to the liquid in varying proportions to yield different fat content milks . full fat milk , sometimes referred to as whole milk , has 3.25 % butterfat added compared to 1-2 % for low and reduced fat milk , and less than half a percent for skim milk . to stop reseparation of the fat from the water , or creaming , the mixture undergoes the high-energy pressurized process of homogenization . before milk hits the shelves , it 's also typically heat treated to reduce its level of microbes , a government-sanctioned process that raw milk enthusiasts argue may reduce milk 's nutritional worth . milk spoilage is started by microbes , which consume and break down the nutrients in milk . that process causes butterfat to clump together , leading to a visually unpleasant product . and the byproducts of the microbes ' consumption are compounds that taste and smell nasty . but there 's a bigger problem . raw milk can carry microbes that are the sources of deadly diseases , so in order to kill as many of those microbes as possible , and keep milk fresh longer , we use a technique called pasteurization . one version of this process involves exposing milk to about 30 seconds of high heat . another version , called ultra-high temperature processing , or ultra pasteurization , blasts the milk with considerably higher temperatures over just a few seconds . uht milk boasts a much longer shelf life , up to twelve months unrefrigerated , compared to pasteurized milk 's two weeks in the fridge . that 's because the higher temperatures of uht processing inactivate far more microbes . yet the higher processing temperatures may adversely affect the nutritional and sensory properties of the milk . ultimately , that choice lies in the consumer 's taste and need for convenience . fortunately , there are many choices available in an industry that produces in excess of 840 million tons of products each year .
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or it can be later added back to the liquid in varying proportions to yield different fat content milks . full fat milk , sometimes referred to as whole milk , has 3.25 % butterfat added compared to 1-2 % for low and reduced fat milk , and less than half a percent for skim milk . to stop reseparation of the fat from the water , or creaming , the mixture undergoes the high-energy pressurized process of homogenization .
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milk is produced by all mammals , and the composition of the milk that each mammal produces varies . for example , reindeer ’ s milk has 20 % fat in comparison to the 5 % fat in cow ’ s milk . what are the reasons for these differences ?
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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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try to measure a circle . the diameter and radius are easy , they 're just straight lines you can measure with a ruler .
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which parts of a circle are easy to measure and why ?
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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 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 .
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a single tree can be linked to ________ .
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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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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 .
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true or false : to this day , no one has been able to prove that they have telekinetic powers .
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