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( music ) ( music ) we live in an interconnected , an increasingly globalized world . thanks to international jet travel , people and the diseases they carry can be in any city on the planet in a matter of hours . and once a virus touches down , sometimes all it takes is one sneeze to spread the infection throughout the community . when humans were hunter-gatherers , roaming the wild savannas , we were never in one place long enough , and settlements were not large enough to sustain the transmission of infectious microbes . but with the advent of the agricultural revolution 10,000 years ago , and the arrival of permanent settlements in the middle east , people began living side-by-side with animals , facilitating the spread of bacteria and viruses between cattle and humans . epidemics and pandemics come in many shapes and forms . in 2010 , for instance , a devastating earthquake struck haiti , forcing thousands of people into temporary refugee camps . within weeks , the camps had become breeding grounds for cholera , a bacteria spread by contaminated water , triggering a country-wide epidemic . but the most common cause of epidemics are viruses , such as measles , influenza and hiv . and when they go global , we call them pandemics . pandemics have occurred throughout human history , some have left scars on the tissue and bone of their victims , while evidence for others comes from preserved dna . for instance , scientists have recovered dna from the bacteria that transmits tuberculosis from the remains of ancient egyptian mummies . and in 2011 , scientists investigating a plague pit in the city of london were able to reconstruct the genome of yersinia pestis , the bacterium responsible for the black death of the 14th century . it is thought the plague originated in china in around 1340 , spreading west along the silk road , the caravan route running from mongolia to the crimea . in 1347 , the plague reached the mediterranean , and by 1400 , it had killed in excess of 34 million europeans , earning it the title , the great mortality . it was later historians who called it the black death . however , by far the greatest pandemic killer is influenza . flu is constantly circulating between the southern and northern hemispheres . in north america and europe , seasonal flus occur every autumn and winter . as the majority of children and adults will have been exposed to the virus in previous seasons , these illnesses are usually mild . however , every 20 to 40 years or so the virus undergoes a dramatic mutation . usually this occurs when a wild flu virus circulating in ducks and farm poultry meets a pig virus , and they exchange genes . this process is known as antigenic shift and has occurred throughout human history . the first recorded pandemic occurred in 1580 . the 18th and 19th centuries saw at least six further pandemics . in terms of mortality , none can compare with the great flu pandemic of 1918 . the first indication of the pandemic came in the spring , when american troops in northern france began complaining of chills , headaches and fever . then , the following september , at a u.s. army barracks near boston , soldiers started collapsing on parade , prompting their removal to the camp infirmary . as a surgeon there recalled , two hours after admission , they had the mahogany spots over the cheekbones and a few hours later you can begin to see the cyanosis extending from their ears and spreading all over the face . it is only a matter of a few hours then until death comes , and it is simply a struggle for air until they suffocate . on the s.s. leviathan , a huge american transport en route to bordeaux , sick men hemorrhaged blood from their noses , turning the decks between their bunks slick with bodily fluids . meanwhile , british soldiers returning from northern france on furlough introduced the flu to dover and other channel ports , from where the virus was carried by rail to london . by the time the pandemic had run its course in april 1919 , an estimated 675,000 americans and 230,000 britons were dead . in india alone , some 10 million were killed , and worldwide the death toll was an astonishing 50 million . but that was then . today , planes can transport viruses to any country on the globe in a fraction of the time it took in 1918 . in february 2003 , for instance , a chinese doctor arrived at the metropole hotel in hong kong feeling unwell . unknown to him , he was harboring a new animal-origin virus called sars , short for severe acute respiratory syndrome . within 24 hours of checking into room 913 , sixteen other guests had been infected , and over the following days five boarded planes to overseas destinations , spreading the virus to vietnam , singapore and canada . flights between hong kong , toronto and other international cities were quickly grounded and thanks to other emergency measures , a pandemic was averted . by the time the outbreak was over four months later , sars had infected 29 countries worldwide and more than 1,000 people were dead . for all that the virus was rapidly contained , however , there was little that could be done about the alarming news reports carried by cable news channels and the internet . as bloggers added to the hysteria by spreading unfounded conspiracy theories , tourism in hong kong and other affected cities ground to a halt , costing businesses more than 10 billion u.s. dollars . one business , however , did very well . above all , sars was a reminder that pandemics have always been associated with panic . if history teaches us anything , it 's that while pandemics may start small , their impacts can be as dramatic as wars and natural disasters . the difference today is that science gives us the ability to detect pandemics right at the very beginning and to take action to mitigate their impacts before they spread too widely . ( music )
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pandemics have occurred throughout human history , some have left scars on the tissue and bone of their victims , while evidence for others comes from preserved dna . for instance , scientists have recovered dna from the bacteria that transmits tuberculosis from the remains of ancient egyptian mummies . and in 2011 , scientists investigating a plague pit in the city of london were able to reconstruct the genome of yersinia pestis , the bacterium responsible for the black death of the 14th century .
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scientists have extracted from human remains which of the following infectious agents ?
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so my name is kakani katija , and i 'm a bioengineer . i study marine organisms in their natural environment . and what i want to point out , and at least you can see this in this visualization , is that the ocean environment is a dynamic place . what you 're seeing are the kinds of currents , as well as the whirls , that are left behind in the ocean because of tides or because of winds . and imagine a marine organism as living in this environment , and they 're trying to undergo their entire lives while dealing with currents like these . but what i also want to point out is that small organisms also create small fluid motions , as well . and it 's these fluid motions that i study . and we can think about them like being footprints . so this is my dog kieran , and take a look at her footprints . footprints provide a lot of information . not only do they tell us what kind of organism left them , they might also tell us something about when that organism was there , but also what kind of behavior , were they running or were they walking ? and so terrestrial organisms , like my cute dog kieran , might be leaving footprints behind in dirt or in sand , but marine organisms leave footprints in the form of what we call wake structures , or hydrodynamic signatures , in fluid . now imagine , it 's really hard to see these kinds of structures because fluid is transparent . however , if we add something to the fluid , we get a completely different picture . and you can see that these footprints that marine organisms create are just dynamic . they are constantly changing . and marine organisms also have the ability to sense these signatures . they can also inform decisions , like whether or not they want to continue following a signature like this to find a mate or to find food , or maybe avoid these signatures to avoid being eaten . so imagine the ability to be able to not only see or visualize these kinds of signatures , but to also measure them . this is the engineering side of what i do . and so what i 've done is i actually took a laboratory technique and miniaturized it and basically shrunk it down into the use of underwater housings to make a device that a single scuba diver can use . and so a single scuba diver can go anywhere from the surface to 40 meters , or 120 feet deep , to measure the hydrodynamic signatures that organisms create . before i begin , i want to immerse you into what these kinds of measurements require . so in order to work , we actually dive at night , and this is because we 're trying to minimize any interactions between the laser and sunlight and we 're diving in complete darkness because we do not want to scare away the organisms we 're trying to study . and then once we find the organisms we 're interested in , we turn on a green laser . and this green laser is actually illuminating a sheet of fluid , and in that fluid , it 's reflecting off of particles that are found everywhere in the ocean . and so as an animal swims through this laser sheet , you can see these particles are moving over time , and so we actually risk our lives to get this kind of data . what you 're going to see is that on the left these two particles images that shows the displacement of fluid over time , and using that data , you can actually extract what the velocity of that fluid is , and that 's indicated by the vector plots that you see in the middle . and then we can use that data to answer a variety of different questions , not only to understand the rotational sense of that fluid , which you see on the right , but also estimate something about energetics , or the kinds of forces that act on these organisms or on the fluid , and also evaluate swimming and feeding performance . we 've used this technique on a variety of different organisms , but remember , there 's an issue here . we 're only able to study organisms that a scuba diver can reach . and so before i finish , i want to tell you what the next frontier is in terms of these kinds of measurements . and with collaborators at monterey bay aquarium research institute , we 're developing instrumentation to go on remotely opperated vehicles so we can study organisms anywhere from the surface down to 4000 meters , or two and a half miles . and so we can answer really interesting questions about this organism , this is a larvacean , that creates a feeding current and forces fluids through their mucus house and extracts nutrients . and then this animal , this is a siphonophore , and they can get to lengths about half the size of a football field . and they 're able to swim vertically in the ocean by just creating jet propulsion . and then finally we can answer these questions about how swarming organisms , like krill , are able to affect mixing on larger scales . and this is actually one of the most interesting results so far that we 've collected using the scuba diving device in that organisms , especially when they 're moving in mass , are able to generate mixing at levels that are equivalent to some other physical processes that are associated with winds and tides . but before i finish , i want to leave you all with a question because i think it 's important to keep in mind that technologies today that we take for granted started somewhere . it was inspired from something . so imagine scientists and engineers were inspired by birds to create airplanes . and something we take for granted , flying from san francisco to new york , is something that was inspired by an organism . and as we 're developing these new technologies to understand marine organisms , what we want to do is answer this question : how will marine organisms inspire us ? will they allow us to develop new underwater technologies , like underwater vehicles that look like a jellyfish ? i think it 's a really exciting time in ocean exploration because now we have the tools available to answer this kind of question , and with the help of you guys at some point , you can apply these tools to answer this kind of question and also develop technologies of the future . thank you .
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and so what i 've done is i actually took a laboratory technique and miniaturized it and basically shrunk it down into the use of underwater housings to make a device that a single scuba diver can use . and so a single scuba diver can go anywhere from the surface to 40 meters , or 120 feet deep , to measure the hydrodynamic signatures that organisms create . before i begin , i want to immerse you into what these kinds of measurements require .
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how may the hydrodynamic signatures of a swimming tuna vary from a swimming jellyfish ?
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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 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 .
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suzanne simard compares forests to human ________ .
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translator : andrea mcdonough reviewer : bedirhan cinar i am going to start with a challenge . i want you to imagine each of these two scenes in as much detail as you can . scene number one : `` they gave us a hearty welcome . '' well , who are the people who are giving a hearty welcome ? what are they wearing ? what are they drinking ? ok , scene two : `` they gave us a cordial reception . '' how are these people standing ? what expressions are on their faces ? what are they wearing and drinking ? fix these pictures in your mind 's eye and then jot down a sentence or two to describe them . we 'll come back to them later . now on to our story . in the year 400 c.e . the celts in britain were ruled by romans . this had one benefit for the celts : the romans protected them from the barbarian saxon tribes of northern europe . but then the roman empire began to crumble , and the romans withdrew from britain . with the romans gone , the germanic tribes , the angles , saxons , jutes , and frisians quickly sailed across the water , did away with the celts , and formed kingdoms in the british isles . for several centuries , these tribes lived in britain , and their germanic language , anglo saxon , became the common language , what we call old english . although modern english speakers may think old english sounds like a different language , if you look and listen closely , you 'll find many words that are recognizable . for example , here is what the lord 's prayer looks like in old english . at first glance , it may look unfamiliar , but update the spelling a bit , and you 'll see many common english words . so the centuries passed with britains happily speaking old english , but in the 700 's , a series of viking invasions began , which continued until a treaty split the island in half . on one side were the saxons . on the other side were the danes who spoke a language called old norse . as saxons fell in love with their cute danish neighbors and marriages blurred the boundaries , old norse mixed with old english , and many old norse words like freckle , leg , root , skin , and want are still a part of our language . 300 years later , in 1066 , the norman conquest brought war again to the british isles . the normans were vikings who settled in france . they had abandoned the viking language and culture in favor of a french lifestyle , but they still fought like vikings . they placed a norman king on the english throne and for three centuries , french was the language of the british royalty . society in britain came to have two levels : french-speaking aristocracy and old english-speaking peasants . the french also brought many roman catholic clergymen with them who added latin words to the mix . old english adapted and grew as thousands of words flowed in , many having to do with government , law , and aristocracy . words like council , marriage , sovereign , govern , damage , and parliament . as the language expanded , english speakers quickly realized what to do if they wanted to sound sophisticated : they would use words that had come from french or latin . anglo saxon words seemed so plain like the anglo saxon peasants who spoke them . let 's go back to the two sentences you thought about earlier . when you pictured the hearty welcome , did you see an earthy scene with relatives hugging and talking loudly ? were they drinking beer ? were they wearing lumberjack shirts and jeans ? and what about the cordial reception ? i bet you pictured a far more classy and refined crowd . blazers and skirts , wine and caviar . why is this ? how is it that phrases that are considered just about synonymous by the dictionary can evoke such different pictures and feelings ? `` hearty '' and `` welcome '' are both saxon words . `` cordial '' and `` reception '' come from french . the connotation of nobility and authority has persisted around words of french origin . and the connotation of peasantry , real people , salt of the earth , has persisted around saxon words . even if you never heard this history before , the memory of it persists in the feelings evoked by the words you speak . on some level , it 's a story you already knew because whether we realize it consciously or only subconsciously , our history lives in the words we speak and hear .
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so the centuries passed with britains happily speaking old english , but in the 700 's , a series of viking invasions began , which continued until a treaty split the island in half . on one side were the saxons . on the other side were the danes who spoke a language called old norse . as saxons fell in love with their cute danish neighbors and marriages blurred the boundaries , old norse mixed with old english , and many old norse words like freckle , leg , root , skin , and want are still a part of our language . 300 years later , in 1066 , the norman conquest brought war again to the british isles .
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what were the factors that enabled the old norse and saxon languages to mix , rather than one replacing the other ?
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o polônio foi outro elemento descoberto por madame curie , a madame curie ela polonesa , mas fez boa parte da pesquisa , se não toda , em paris . polônio é um nome por causa da polônia polônio é um elemento que tem sido não muito importante , até a invenção da bomba atômica , e o polônio tornou-se um material absolutamente crucial pq é usado , ou foi usado , como um gatilho no centro da bomba atômica original . uma das dificuldades é que tem uma meia-vida muito curta . se vc tem um pedaço de polônio , metade dele decai em 138 dias se vc mantém por muito tempo , ele se vai , ou quase todo se vai , e portanto , no início da produção de bombas atômicas , das de hiroshima e nagasaki , o fator limitante na produção de bombas era a produção de polônio para o gatilho . em vez do enriquecimento de urânio ou plutônio , que eram usados para as bombas . bem recentemente o polônio teve uma nova notoriedade , pq foi usado neste caso trágico de envenenamento . no qual uma grande dose de polônio foi dado a um infeliz cidadão russo , que visitava a inglaterra . e ainda não está claro de onde veio o polônio . mas é um material bem pouco comum . e difícil para alguém comum encontrar . se for ingerido , pq decai muito rápido , a radioatividade pode causar todo tipo de efeitos desagradáveis . e , novamente , é provavelmente venenoso ele mesmo . traduzido por prof. dr. luís brudna
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bem recentemente o polônio teve uma nova notoriedade , pq foi usado neste caso trágico de envenenamento . no qual uma grande dose de polônio foi dado a um infeliz cidadão russo , que visitava a inglaterra . e ainda não está claro de onde veio o polônio .
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the russian dissident alexander litvinenko was apparently poisoned with a lethal dose of polonium . do you know which isotope of polonium was added to litvinenko ’ s meal to kill him ?
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to many , one of the coolest things about `` game of thrones '' is that the inhabitants of the dothraki sea have their own real language . and dothraki came hot on the heels of the real language that the na'vi speak in `` avatar , '' which , surely , the na'vi needed when the klingons in `` star trek '' have had their own whole language since 1979 . and let 's not forget the elvish languages in j.r.r . tolkien 's `` lord of the rings '' trilogy , especially since that was the official grandfather of the fantasy conlangs . `` conlang '' is short for `` constructed language . '' they 're more than codes like pig latin , and they 're not just collections of fabricated slang like the nadsat lingo that the teen hoodlums in `` a clockwork orange '' speak , where `` droog '' from russian happens to mean `` friend . '' what makes conlangs real languages is n't the number of words they have . it helps , of course , to have a lot of words . dothraki has thousands of words . na'vi started with 1,500 words . fans on websites have steadily created more . but we can see the difference between vocabulary alone and what makes a real language from a look at how tolkien put together grand old elvish , a conlang with several thousands words . after all , you could memorize 5,000 words of russian and still be barely able to construct a sentence . a four-year-old would talk rings around you . that 's because you have to know how to put the words together . that is , a real language has grammar . elvish does . in english , to make a verb past , you add an `` -ed . '' wash , washed . in elvish , `` wash '' is `` allu '' and `` washed '' is `` allune . '' real languages also change over time . there 's no such thing as a language that 's the same today as it was a thousand years ago . as people speak , they drift into new habits , shed old ones , make mistakes , and get creative . today , one says , `` give us today our daily bread . '' in old english , they said , `` urne gedaeghwamlican hlaf syle us todaeg . '' things change in conlangs , too . tolkien charted out ancient and newer versions of elvish . when the first elves awoke at cuiviénen , in their new language , the word for `` people '' was `` kwendi , '' but in the language of one of the groups that moved away , teleri , over time , `` kwendi '' became `` pendi , '' with the `` k '' turning into a `` p. '' and just like real languages , conlangs like elvish split off into many . when the romans transplanted latin across europe , french , spanish , and italian were born . when groups move to different places , over time , their ways of speaking grow apart , just like everything else about them . thus , latin 's word for hand was `` manus , '' but in french , it became `` main , '' while in spain it became `` mano . '' tolkien made sure elvish did the same kind of thing . while that original word `` kwendi '' became `` pendi '' among the teleri , among the avari , who spread throughout middle earth , it became `` kindi '' when the `` w '' dropped out . the elvish varieties tolkien fleshed out the most are quenya and sindarin , and their words are different in the same way french and spanish are . quenya has `` suc '' for `` drink , '' sindarin has `` sog . '' and as you know , real languages are messy . that 's because they change , and change has a way of working against order , just like in a living room or on a bookshelf . real languages are never perfectly logical . that 's why tolkien made sure that elvish had plenty of exceptions . lots of verbs are conjugated in ways you just have to know . take even the word `` know . '' in the past , it 's `` knew , '' which is n't explained by any of the rules in english . oh well . in elvish , `` know '' is `` ista , '' but `` knew '' is `` sinte . '' oh well . the truth is , though , that elvish is more a sketch for a real language than a whole one . for tolkien , elvish was a hobby rather than an attempt to create something people could actually speak . much of the elvish the characters in the `` lord of the rings '' movies speak has been made up since tolkien by dedicated fans of elvish based on guesses as to what tolkien would have constructed . that 's the best we can do for elvish because there are no actual elves around to speak it for us . but the modern conlangs go further . dothraki , na'vi , and klingon are developed enough that you can actually speak them . here 's a translation of `` hamlet '' into klingon , although performing it would mean getting used to pronouncing `` k '' with your uvula , that weird , cartoony thing hanging in the back of your throat . believe it or not , you actually do that in plenty of languages around the world , like eskimo ones . pronouncing elvish is much easier , though . so , let 's take our leave for now from this introduction to conlangs in elvish and the other three conlangs discussed with a heartfelt quad-conlangual valedictory : `` a na marie ! '' `` hajas ! '' na'vi 's `` kiyevame ! '' `` qapla ! '' and `` goodbye ! ''
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in old english , they said , `` urne gedaeghwamlican hlaf syle us todaeg . '' things change in conlangs , too . tolkien charted out ancient and newer versions of elvish .
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conlangs are :
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hunger claws at your grumbling belly . it tugs at your intestines , which begin to writhe , aching to be fed . being hungry generates a powerful , often unpleasant physical sensation that 's almost impossible to ignore . after you 've reacted by gorging on your morning pancakes , you start to experience an opposing force , fullness , but how does your body actually know when you 're full ? the sensation of fullness is set in motion as food moves from your mouth down your esophagus . once it hits your stomach , it gradually fills the space . that causes the surrounding muscular wall to stretch , expanding slowly like a balloon . a multitude of nerves wrapped intricately around the stomach wall sense the stretching . they communicate with the vagus nerve up to the brainstem and hypothalamus , the main parts of the brain that control food intake . but that 's just one input your brain uses to sense fullness . after all , if you fill your stomach with water , you wo n't feel full for long . your brain also takes into account chemical messengers in the form of hormones produced by endocrine cells throughout your digestive system . these respond to the presence of specific nutrients in your gut and bloodstream , which gradually increase as you digest your food . as the hormones seep out , they 're swept up by the blood and eventually reach the hypothalamus in the brain . over 20 gastrointestinal hormones are involved in moderating our appetites . one example is cholecystokinin , which is produced in response to food by cells in the upper small bowel . when it reached the hypothalamus , it causes a reduction in the feeling of reward you get when you eat food . when that occurs , the sense of being satiated starts to sink in and you stop eating . cholecystokinin also slows down the movement of food from the stomach into the intestines . that makes your stomach stretch more over a period of time , allowing your body to register that you 're filling up . this seems to be why when you eat slowly , you actually feel fuller compared to when you consume your food at lightning speed . when you eat quickly , your body does n't have time to recognize the state it 's in . once nutrients and gastrointestinal hormones are present in the blood , they trigger the pancreas to release insulin . insulin stimulates the body 's fat cells to make another hormone called leptin . leptin reacts with receptors on neuron populations in the hypothalamus . the hypothalamus has two sets of neurons important for our feeling of hunger . one set produces the sensation of hunger by making and releasing certain proteins . the other set inhibits hunger through its own set of compounds . leptin inhibits the hypothalamus neurons that drive food intake and stimulates the neurons that suppress it . by this point , your body has reached peak fullness . through the constant exchange of information between hormones , the vagus nerve , the brainstem , and the different portions of hypothalamus , your brain gets the signal that you 've eaten enough . researchers have discovered that some foods produce more long-lasting fullness than others . for instance , boiled potatoes are ranked as some of the most hunger-satisfying foods , while croissants are particularly unsatisfying . in general , foods with more protein , fiber , and water tend to keep hunger at bay for longer . but feeling full wo n't last forever . after a few hours , your gut and brain begin their conversation again . your empty stomach produces other hormones , such as ghrelin , that increase the activity of the hunger-causing nerve cells in the hypothalamus . eventually , the growling beast of hunger is reawakened . luckily , there 's a dependable antidote for that .
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they communicate with the vagus nerve up to the brainstem and hypothalamus , the main parts of the brain that control food intake . but that 's just one input your brain uses to sense fullness . after all , if you fill your stomach with water , you wo n't feel full for long .
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how does cholecystokinin affect our sense of fullness ?
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in 1800 , the explorer alexander von humboldt witnessed a swarm of electric eels leap out of the water to defend themselves against oncoming horses . most people thought the story so unusual that humboldt made it up . but fish using electricity is more common than you might think ; and yes , electric eels are a type of fish . underwater , where light is scarce , electrical signals offer ways to communicate , navigate , and find—plus , in rare cases , stun—prey . nearly 350 species of fish have specialized anatomical structures that generate and detect electrical signals . these fish are divided into two groups , depending on how much electricity they produce . scientists call the first group the weakly electric fish . structures near their tails called electric organs produce up to a volt of electricity , about two-thirds as much as a aa battery . how does this work ? the fish 's brain sends a signal through its nervous system to the electric organ , which is filled with stacks of hundreds or thousands of disc-shaped cells called electrocytes . normally , electrocytes pump out sodium and potassium ions to maintain a positive charge outside and negative charge inside . but when the nerve signal arrives at the electrocyte , it prompts the ion gates to open . positively charged ions flow back in . now , one face of the electrocyte is negatively charged outside and positively charged inside . but the far side has the opposite charge pattern . these alternating charges can drive a current , turning the electrocyte into a biological battery . the key to these fish 's powers is that nerve signals are coordinated to arrive at each cell at exactly the same time . that makes the stacks of electrocytes act like thousands of batteries in series . the tiny charges from each one add up to an electrical field that can travel several meters . cells called electroreceptors buried in the skin allow the fish to constantly sense this field and the changes to it caused by the surroundings or other fish . the peter ’ s elephantnose fish , for example , has an elongated chin called a schnauzenorgan that 's riddled in electroreceptors . that allows it to intercept signals from other fish , judge distances , detect the shape and size of nearby objects , and even determine whether a buried insect is dead or alive . but the elephantnose and other weakly electric fish do n't produce enough electricity to attack their prey . that ability belongs to the strongly electric fish , of which there are only a handful of species . the most powerful strongly electric fish is the electric knife fish , more commonly known as the electric eel . three electric organs span almost its entire two-meter body . like the weakly electric fish , the electric eel uses its signals to navigate and communicate , but it reserves its strongest electric discharges for hunting using a two-phased attack that susses out and then incapacitates its prey . first , it emits two or three strong pulses , as much as 600 volts . these stimulate the prey 's muscles , sending it into spasms and generating waves that reveal its hiding place . then , a volley of fast , high-voltage discharges causes even more intense muscle contractions . the electric eel can also curl up so that the electric fields generated at each end of the electric organ overlap . the electrical storm eventually exhausts and immobilizes the prey , and the electric eel can swallow its meal alive . the other two strongly electric fish are the electric catfish , which can unleash 350 volts with an electric organ that occupies most of its torso , and the electric ray , with kidney-shaped electric organs on either side of its head that produce as much as 220 volts . there is one mystery in the world of electric fish : why do n't they electrocute themselves ? it may be that the size of strongly electric fish allows them to withstand their own shocks , or that the current passes out of their bodies too quickly . some scientists think that special proteins may shield the electric organs , but the truth is , this is one mystery science still has n't illuminated .
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that ability belongs to the strongly electric fish , of which there are only a handful of species . the most powerful strongly electric fish is the electric knife fish , more commonly known as the electric eel . three electric organs span almost its entire two-meter body .
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what is one way the electric eel can increase the intensity of the electric charge it delivers to its prey ?
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you and a fellow castaway are stranded on a desert island playing dice for the last banana . you 've agreed on these rules : you 'll roll two dice , and if the biggest number is one , two , three or four , player one wins . if the biggest number is five or six , player two wins . let 's try twice more . here , player one wins , and here it 's player two . so who do you want to be ? at first glance , it may seem like player one has the advantage since she 'll win if any one of four numbers is the highest , but actually , player two has an approximately 56 % chance of winning each match . one way to see that is to list all the possible combinations you could get by rolling two dice , and then count up the ones that each player wins . these are the possibilities for the yellow die . these are the possibilities for the blue die . each cell in the chart shows a possible combination when you roll both dice . if you roll a four and then a five , we 'll mark a player two victory in this cell . a three and a one gives player one a victory here . there are 36 possible combinations , each with exactly the same chance of happening . mathematicians call these equiprobable events . now we can see why the first glance was wrong . even though player one has four winning numbers , and player two only has two , the chance of each number being the greatest is not the same . there is only a one in 36 chance that one will be the highest number . but there 's an 11 in 36 chance that six will be the highest . so if any of these combinations are rolled , player one will win . and if any of these combinations are rolled , player two will win . out of the 36 possible combinations , 16 give the victory to player one , and 20 give player two the win . you could think about it this way , too . the only way player one can win is if both dice show a one , two , three or four . a five or six would mean a win for player two . the chance of one die showing one , two , three or four is four out of six . the result of each die roll is independent from the other . and you can calculate the joint probability of independent events by multiplying their probabilities . so the chance of getting a one , two , three or four on both dice is 4/6 times 4/6 , or 16/36 . because someone has to win , the chance of player two winning is 36/36 minus 16/36 , or 20/36 . those are the exact same probabilities we got by making our table . but this does n't mean that player two will win , or even that if you played 36 games as player two , you 'd win 20 of them . that 's why events like dice rolling are called random . even though you can calculate the theoretical probability of each outcome , you might not get the expected results if you examine just a few events . but if you repeat those random events many , many , many times , the frequency of a specific outcome , like a player two win , will approach its theoretical probability , that value we got by writing down all the possibilities and counting up the ones for each outcome . so , if you sat on that desert island playing dice forever , player two would eventually win 56 % of the games , and player one would win 44 % . but by then , of course , the banana would be long gone .
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now we can see why the first glance was wrong . even though player one has four winning numbers , and player two only has two , the chance of each number being the greatest is not the same . there is only a one in 36 chance that one will be the highest number .
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based on the rules stated in the `` battle for the banana '' , what percentage chance does contestant two have of winning ?
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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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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 .
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is decomposition inevitable ? back up your answer with three pieces of evidence .
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translator : andrea mcdonough reviewer : bedirhan cinar so as an astronomer , when i look at the sky with other people , they always ask me , `` what is your favorite place in the universe ? what is your favorite galaxy ? what is your favorite planet ? '' my answer is earth . that 's right . this is a very special place , even for an astronomer . we look at a lot of places , but there 's only one that we know of in the whole universe that we can live on . it 's an amazing planet , there is an amazing number of things happening , some of them , you are hearing about it today . that 's the only place in the universe where we know that there is life , so that makes it extremely special . what i 'm going to talk to you about is this great adventure in astronomy that is happening where we are actually actively looking for other places like this . it 's impossible to imagine the number of possibilities , what happens on those other planets that can be habitable . so that 's what i 'm going to tell you about . so , the first thing we have to think of is , well , what makes a planet habitable ? and , the easiest thing to do is to look at our own solar system . we have multiple examples . the first thing we learn is that size matters . we ca n't have a planet that 's too small or too big . if we look at a planet that is too small , it does n't have an atmosphere . the moon , technically not a planet , but a good example for this , is too small , it does n't hold an atmosphere . jupiter - very , very big - and it actually is mostly composed of gas , it has no surface you can stand on . the earth is just right . the second thing that we learned is that the planet has to be at the right distance from its star . if the planet is too close to its star , it 's too hot . that 's the case for venus . here i have a picture that was taken by a spacecraft that landed on venus , and the surface , although it 's rocky and quite familiar to us compared to earth , it 's really too hot . at the opposite end , if a planet is too far from the star , it is too cold . that 's the case for mars . so , we need to look for planets that are at the right distance from their star and also of the right size . so , one other thing , you know , you might think , `` oh , this is really hard because the planet has to be just right . it only happened once in our solar system . '' but when you look at the sky at night , and here 's a video that i took actually from hawaii , a dark place where you can see a lot of stars , the first thing you notice is that there are a lot of stars . so , the odds are in our favor , even if a small fraction of the stars have habitable planets . there are a lot of stars . on a moonless night , in a dark site , if you count the stars in the sky and you count five stars per second , it would take you 15 minutes to count all of the stars in the sky . that is a tiny fraction of the stars in our galaxy . if you count all the stars in our galaxy , and you also count at five stars per second , it would take you more than 1,000 years to count all the stars in our galaxy . and then , if you manage to count the galaxies in the universe , if you count five galaxies per second , it would take you also more than 1,000 years to count all of the galaxies in the universe . so the numbers are just astronomical , there 's a lot of opportunities for exoplanets . there has to be a large number of exoplanets along which there are , on which there could be life . so this is very exciting . so let 's imagine that maybe only 1 in 100 stars has the right kind of planet , and i think this is pessimistic . if you could visit one of those planets per second , it 'll take you sixty years to actually visit all of them in our galaxy alone . that 's , i think , one second is not enough to study them . so , there 's a few hundred of us in this room . if we divided the task and each of us basically took a couple of minutes to study each planet , it would take us a life time to do this . meet back again and tell those amazing stories of what we would have seen in maybe some ted senior event . so , why is it hard ? why do n't we have pictures of exoplanets with aliens on them ? well , here 's an example . this is a picture that was taken by the cassinni spacecraft as it was orbiting saturn . it 's actually behind saturn , so what you see is the sun that is blocked by saturn . and if you look very , in detail , if you have very sharp eyesight , you will see all of us . we 're all on that picture . here is where we are . um , so that 's what earth starts to look like when we look at it from far away . now , we have to do the same thing around other stars , and the planet is very close to the star . so this is zooming in to us . all of us are on that little dot at the time the picture was taken . so , what i work on is inventing optics , tricks to actually do this , to take images of planets around those other stars . this is my easiest coronagraph . we call this optic tricks , `` coronagraph '' . this is the easiest one i ever built . i just put my thumb in front of the sun and then you can see things around it . that 's what we 're trying to do , but we need to do it much better than what i did in this picture . and , there are two things we need to do : we need a much better eye , call them telescopes , and we need more fancy , clever ways to do it than putting a thumb . so as an example , one of the projects i work on is for the subaru telescope , which you can see here in this picture . it 's a very large telescope , so i replace my eye by a large telescope . and , the other thing that we do is the coronagraph is not just a stupid thumb , it 's this very complicated thing that 's shown in that picture that i would love to have time to tell you about . just to give you a sense for size , this arrow points to a door on the side of the telescope , and if you have very sharp eyes , you can see that there is a railing going around the telescope , so it 's a really big eye . so , i think the most exciting thing for me is actually to look at the night sky , to see all these stars and wonder , `` well , are there people on planets around those stars ? '' because there must be amazing things happening around those stars that we do n't know yet . during your life time , we will start to actually figure out those things . and the most exciting thing for me is to think about , maybe , beings on those stars looking back at our star and wondering the same thing . so i think the future will be extremely exciting because we are starting to figure out those things and amazing range of possibilities is , i think , even wider than our imagination . thank you .
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if you count all the stars in our galaxy , and you also count at five stars per second , it would take you more than 1,000 years to count all the stars in our galaxy . and then , if you manage to count the galaxies in the universe , if you count five galaxies per second , it would take you also more than 1,000 years to count all of the galaxies in the universe . so the numbers are just astronomical , there 's a lot of opportunities for exoplanets .
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if you counted all the galaxies in the universe at five galaxies per second , how long would it take you to count all the galaxies ?
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we already know that the world is made of things , things like cats and macaroni salad , and macaroni salad is made of things like mayo and mustard and celery , which are all made of molecules . as we 'll see , these molecules are made of the same stuff , just mixed together in different ways . let 's go back to our macaroni salad . we 've already unmixed things physically as much as we can . now , we 'll go further and unmix things chemically by breaking some bonds . many larger , complex molecules are just a bunch of smaller molecules bonded together like building blocks . here , again , macaroni salad provides a nice example . if you look at the pasta , you 'll notice it 's made of a lot of this stuff , starch , which is this molecule , otherwise known as amylose . turns out , if you break some bonds , amylose is made up of smaller molecules of glucose , a simple sugar . if you take a bunch of these same glucose molecules and rearrange them in a different way , you get cellulose , which is what plants are made of . so , while this piece of pasta made of amylose and this wooden spoon made of cellulose look vastly different , they 're both essentially made of the same molecules , just stuck together differently . this type of breaking apart and recombining is what goes on when you digest food . the complex proteins found in the foods we eat , like carrots and eggs , ca n't be used by our bodies because we are not carrots or chickens . what we can use are the smaller molecules that make up these proteins , the amino acids . during digestion , our bodies break these proteins up into their amino acids so they can be rearranged and put back together to make human proteins . but let 's keep breaking bonds . all molecules are made up of atoms bonded together . if some molecules are building blocks , atoms are the building blocks of the building blocks . and you 'll notice that with the molecules from macaroni salad , the same six types of atoms keep showing up : carbon , hydrogen , oxygen , nitrogen , phosphorus , and sulfur , or chonps . there 's a few others , but the big six is what macaroni salad is made of . if we went a step further , we could use these same atoms , recombine them , and make other stuff like gasoline or sulfuric acid , methane , and nylon . it 's all made from the same elements that make up macaroni salad . so , to recap , everything is made of atoms . they are the stuff that things are made of . atoms are grouped together in different ways to form molecules . these molecules are constantly being combined , broken apart , and recombined . they get thrown into mixtures , separated , remixed over and over and over again . the stuff that things are made of is always in flux ; it 's always changing . macaroni salad is only macaroni salad for a short time . you eat it , some of it becomes part of you , the rest eventually goes into the ocean and gets eaten by other animals that die , and after millions of years , they turn into oil , which is where gasoline comes from . and that 's why gasoline and macaroni salad are not that different - they 're both made of the same stuff , just one tastes better .
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now , we 'll go further and unmix things chemically by breaking some bonds . many larger , complex molecules are just a bunch of smaller molecules bonded together like building blocks . here , again , macaroni salad provides a nice example .
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many larger complex molecules are just ________ .
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he was one of the most fearsome warlords who ever lived , waging an unstoppable conquest across the eurasian continent . but was genghis khan a vicious barbarian or a unifier who paved the way for the modern world ? we 'll see in `` history vs. genghis khan . '' `` order , order . now who 's the defendant today ? khan ! '' `` i see your honor is familiar with genghis khan , the 13th century warlord whose military campaigns killed millions and left nothing but destruction in their wake . '' `` objection . first of all , it 's pronounced genghis kahn . '' `` really ? '' `` in mongolia , yes . regardless , he was one of the greatest leaders in human history . born temüjin , he was left fatherless and destitute as a child but went on to overcome constant strife to unite warring mongol clans and forge the greatest empire the world had seen , eventually stretching from the pacific to europe 's heartland . '' `` and what was so great about invasion and slaughter ? northern china lost 2/3 of its population . '' `` the jin dynasty had long harassed the northern tribes , paying them off to fight each other and periodically attacking them . genghis khan was n't about to suffer the same fate as the last khan who tried to unite the mongols , and the demographic change may reflect poor census keeping , not to mention that many peasants were brought into the khan 's army . '' `` you can pick apart numbers all you want , but they wiped out entire cities , along with their inhabitants . '' `` the khan preferred enemies to surrender and pay tribute , but he firmly believed in loyalty and diplomatic law . the cities that were massacred were ones that rebelled after surrendering , or killed as ambassadors . his was a strict understanding of justice . '' `` multiple accounts show his army 's brutality going beyond justice : ripping unborn children from mothers ' wombs , using prisoners as human shields , or moat fillers to support siege engines , taking all women from conquered towns -- '' `` enough ! how barbaric ! '' `` is that really so much worse than other medieval armies ? '' `` that does n't excuse genghis khan 's atrocities . '' `` but it does make genghis khan unexceptional for his time rather than some bloodthirsty savage . in fact , after his unification of the tribes abolished bride kidnapping , women in the mongol ranks had it better than most . they controlled domestic affairs , could divorce their husbands , and were trusted advisors . temüjin remained with his first bride all his life , even raising her possibly illegitimate son as his own . '' `` regardless , genghis khan 's legacy was a disaster : up to 40 million killed across eurasia during his descendents ' conquests . 10 % of the world population . that 's not even counting casualties from the black plague brought to europe by the golden horde 's siege of kaffa . '' `` surely that was n't intentional . '' `` actually , when they saw their own troops dying of the plague , they catapulted infected bodies over the city walls . '' `` blech . '' `` the accounts you 're referencing were written over a hundred years after the fact . how reliable do you think they are ? plus , the survivors reaped the benefits of the empire genghis khan founded . '' `` benefits ? '' `` the mongol empire practiced religious tolerance among all subjects , they treated their soldiers well , promoted based on merit , rather than birth , established a vast postal system , and inforced universal rule of law , not to mention their contribution to culture . '' `` you mean like hulagu khan 's annihilation of baghdad , the era 's cultural capital ? libraries , hospitals and palaces burned , irrigation canals buried ? '' `` baghdad was unfortunate , but its kalif refused to surrender , and hulagu was later punished by berke khan for the wanton destruction . it was n't mongol policy to destroy culture . usually they saved doctors , scholars and artisans from conquered places , and transferred them throughout their realm , spreading knowledge across the world . '' `` what about the devastation of kievan rus , leaving its people in the dark ages even as the renaissance spread across western europe ? '' `` western europe was hardly peaceful at the time . the stability of mongol rule made the silk road flourish once more , allowing trade and cultural exchange between east and west , and its legacy forged russia and china from warring princedoms into unified states . in fact , long after the empire , genghis khan 's descendants could be found among the ruling nobility all over eurasia . '' `` not surprising that a tyrant would inspire further tyrants . '' `` careful what you call him . you may be related . '' `` what ? '' `` 16 million men today are descended from genghis khan . that 's one in ever 200 . '' for every great conqueror , there are millions of conquered . whose stories will survive ? and can a leader 's historical or cultural signifigance outweigh the deaths they caused along the way ? these are the questions that arise when we put history on trial .
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now who 's the defendant today ? khan ! '' `` i see your honor is familiar with genghis khan , the 13th century warlord whose military campaigns killed millions and left nothing but destruction in their wake . ''
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how did genghis khan ’ s uniting the tribes improve the status of mongol women ?
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a toothpaste brand claims their product will destroy more plaque than any product ever made . a politician tells you their plan will create the most jobs . we 're so used to hearing these kinds of exaggerations in advertising and politics that we might not even bat an eye . but what about when the claim is accompanied by a graph ? afterall , a graph is n't an opinion . it represents cold , hard numbers , and who can argue with those ? yet , as it turns out , there are plenty of ways graphs can mislead and outright manipulate . here are some things to look out for . in this 1992 ad , chevy claimed to make the most reliable trucks in america using this graph . not only does it show that 98 % of all chevy trucks sold in the last ten years are still on the road , but it looks like they 're twice as dependable as toyota trucks . that is , until you take a closer look at the numbers on the left and see that the figure for toyota is about 96.5 % . the scale only goes between 95 and 100 % . if it went from 0 to 100 , it would look like this . this is one of the most common ways graphs misrepresent data , by distorting the scale . zooming in on a small portion of the y-axis exaggerates a barely detectable difference between the things being compared . and it 's especially misleading with bar graphs since we assume the difference in the size of the bars is proportional to the values . but the scale can also be distorted along the x-axis , usually in line graphs showing something changing over time . this chart showing the rise in american unemployment from 2008 to 2010 manipulates the x-axis in two ways . first of all , the scale is inconsistent , compressing the 15-month span after march 2009 to look shorter than the preceding six months . using more consistent data points gives a different picture with job losses tapering off by the end of 2009 . and if you wonder why they were increasing in the first place , the timeline starts immediately after the u.s. 's biggest financial collapse since the great depression . these techniques are known as cherry picking . a time range can be carefully chosen to exclude the impact of a major event right outside it . and picking specific data points can hide important changes in between . even when there 's nothing wrong with the graph itself , leaving out relevant data can give a misleading impression . this chart of how many people watch the super bowl each year makes it look like the event 's popularity is exploding . but it 's not accounting for population growth . the ratings have actually held steady because while the number of football fans has increased , their share of overall viewership has not . finally , a graph ca n't tell you much if you do n't know the full significance of what 's being presented . both of the following graphs use the same ocean temperature data from the national centers for environmental information . so why do they seem to give opposite impressions ? the first graph plots the average annual ocean temperature from 1880 to 2016 , making the change look insignificant . but in fact , a rise of even half a degree celsius can cause massive ecological disruption . this is why the second graph , which show the average temperature variation each year , is far more significant . when they 're used well , graphs can help us intuitively grasp complex data . but as visual software has enabled more usage of graphs throughout all media , it 's also made them easier to use in a careless or dishonest way . so the next time you see a graph , do n't be swayed by the lines and curves . look at the labels , the numbers , the scale , and the context , and ask what story the picture is trying to tell .
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but what about when the claim is accompanied by a graph ? afterall , a graph is n't an opinion . it represents cold , hard numbers , and who can argue with those ?
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how can graphs present an opinion ?
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you 're standing at the ready inside the goal when suddenly , you feel an intense itch on the back of your head . we 've all experienced the annoyance of an inconvenient itch , but have you ever pondered why we itch in the first place ? the average person experiences dozens of individual itches each day . they can be triggered by all sorts of things , including allergic reactions , dryness , and even some diseases . and then there are the mysterious ones that pop up for no reason at all , or just from talking about itching . you 're scratching your head right now , are n't you ? anyhow , let 's take one of the most common sources : bug bites . when a mosquito bites you , it releases a compound into your body called an anticoagulant that prevents your blood from clotting . that compound , which we 're mildly allergic to , triggers the release of histamine , a chemical that makes our capillaries swell . this enables increased blood flow , which helpfully accelerates the body 's immune response to this perceived threat . that explains the swelling , and it 's the same reason pollen can make your eyes puff up . histamine also activates the nerves involved in itching , which is why bug bites make you scratch . but the itchy sensation itself is n't yet fully understood . in fact , much of what we do know comes from studying the mechanics of itching in mice . researchers have discovered that itch signals in their skin are transmitted via a subclass of the nerves that are associated with pain . these dedicated nerves produce a molecule called natriuretic polypetide b , which triggers a signal that 's carried up the spinal cord to the brain , where it creates the feeling of an itch . when we scratch , the action of our fingernails on the skin causes a low level pain signal that overrides the itching sensation . it 's almost like a distraction , which creates the sensation of relief . but is there actually an evolutionary purpose to the itch , or is it simply there to annoy us ? the leading theory is that our skin has evolved to be acutely aware of touch so that we 're equipped to deal with risks from the outside world . think about it . our automatic scratching response would dislodge anything harmful that 's potentially lurking on our skin , like a harmful sting , a biting insect , or the tendrils of a poisonous plant . this might explain why we do n't feel itching inside our bodies , like in our intestines , which is safe from these external threats , though imagine how maddening that would be . in some people , glitches in the pathways responsible for all of this can cause excessive itching that can actually harm their health . one extreme example is a psychological condition called delusory parasitosis where people believe their bodies are infested with mites or fleas scurrying over and under their skin , making them itch incessantly . another phenomenon called phantom itching can occur in patients who 've had amputations . because this injury has so severely damaged the nervous system , it confuses the body 's normal nerve signaling and creates sensations in limbs that are no longer there . doctors are now finding ways to treat these itching anomalies . in amputees , mirrors are used to reflect the remaining limb , which the patient scratches . that creates an illusion that tricks the brain into thinking the imaginary itch has been satisfied . oddly enough , that actually works . researchers are also searching for the genes involved in itching and developing treatments to try and block the pathway of an itch in extreme cases . if having an unscratchable itch feels like your own personal hell , dante agreed . the italian poet wrote about a section of hell where people were punished by being left in pits to itch for all eternity .
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our automatic scratching response would dislodge anything harmful that 's potentially lurking on our skin , like a harmful sting , a biting insect , or the tendrils of a poisonous plant . this might explain why we do n't feel itching inside our bodies , like in our intestines , which is safe from these external threats , though imagine how maddening that would be . in some people , glitches in the pathways responsible for all of this can cause excessive itching that can actually harm their health .
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what is one of the real-world threats that itching could warn us about ?
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translator : tom carter reviewer : bedirhan cinar she 's only a few feet away . the closer he gets , the more nervous he becomes , the budding zit on his nose growing bigger and bigger until it practically eclipses his face . she looks at him hovering nearby , sees the massive zit , and giggles . he slumps away , feeling sick . stress can sure make a mess , and it happens to both teens and adults . but how does it happen ? let 's rewind to before the zit , to before justin even sees his crush . already late for school , justin got to class just in time to hear the teacher say `` pop quiz . '' he had n't done his homework the night before , and felt more unprepared than the ambushed world war ii soldiers he was supposed to write about . a sudden rush of panic swept over his body , leaving him with sweaty palms , a foggy mind and a racing heart . he stumbled out of class in a daze , and ran straight into his all-time crush , spiking up his stress . stress is a general biological response to a potential danger . in primitive caveman terms , stress can make you fight for your life , or run for your life , if , for example , you 're confronted by a hungry saber-tooth tiger . special chemicals called stress hormones run through your body , giving you more oxygen and power to run away from danger or to face it and fight for your life , hence the term `` fight or flight . '' but when you do n't fight , or take flight , you face the plight . when we 're taking final exams , sitting in traffic or pondering pollution , we internalize stress . it all begins in the brain . the hypothalamus , the master controller of your hormones , releases something called corticotropin-releasing hormone . this triggers the pituitary gland , a pea-sized gland found at the base of the brain , to release adrenocorticotropic hormone which then stimulates the adrenal gland sitting on top of the kidneys to release cortisol , the major stress hormone . these natural chemicals are a great help when you need to run away quickly , or do superhuman feats of courage , but when you 're simply sitting , these stress hormones collect in the body and affect your overall health . stress hormones increase inflammation in the body , suppress the immune system , which makes you more susceptible to infection by acne-causing bacteria , and can even increase oil production in the skin . and this is the perfect storm for forming a pimple . cortisol is a major stress hormone involved in making skin cells churn out oily lipids from special glands called sebaceous glands . but when there 's too much of these oily lipids , called sebum , they can plug up the swollen , inflamed pores and trap the pesky , acne-causing bacteria inside , where they set up house and thrive . add a dash of inflammatory neuropeptides released by the nervous system when you 're -- well , nervous -- and angry zits follow . to make matters worse , justin is a boy , meaning he 's got more testosterone than girls . testosterone is another hormone that increases oil production in the skin . so , his already oily skin , together with a boost in oil and inflammation from stress , is the perfect environment for bacteria to swell , swell , swell up into a major zit . so what could 've justin done to avoid the big pimple ? stressful situations are unavoidable . but we can try to change our responses so that we 're not so stressed in the end . and had he been confident in approaching her , she might not have noticed the pimple , or he might not have had one .
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these natural chemicals are a great help when you need to run away quickly , or do superhuman feats of courage , but when you 're simply sitting , these stress hormones collect in the body and affect your overall health . stress hormones increase inflammation in the body , suppress the immune system , which makes you more susceptible to infection by acne-causing bacteria , and can even increase oil production in the skin . and this is the perfect storm for forming a pimple . cortisol is a major stress hormone involved in making skin cells churn out oily lipids from special glands called sebaceous glands . but when there 's too much of these oily lipids , called sebum , they can plug up the swollen , inflamed pores and trap the pesky , acne-causing bacteria inside , where they set up house and thrive .
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a pimple is indeed not simple . although we focused on the stress component , which increases inflammation and oil production , describe a few other components that lead to the development of an actual pimple . ( video hint : “ cortisol is a major stress hormone involved in ... ” )
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[ music ] for thousands of years , humans , and plants and animals long before that , have been using frozen “ sky water ” to keep warm . which sort of doesn ’ t make sense . because snow is cool . you might even say it ’ s… ice cold . yeeaahhhhh ! no one knows for sure who built the first igloo , but with the right fit and the right physics , snow can actually warm you better than the inside of a tauntaun . `` you 'll be ok , luke ! '' so , how can something cold keep you cozy ? [ music ] the vast , frozen arctic is one of the most forbidding environments on our planet , yet , the inuit have managed to live there for about 5,000 years . out on the pack ice , winter temperatures reach 50 degrees below zero , and when it ’ s that cold , surviving means finding shelter . it ’ s not an area known for its forests , so nomadic hunters learned to build with the only thing available : snow . eskimo languages really do have dozens and dozens of different words for snow , because there are a lot of different types , and the type of snow you choose can dictate whether your igloo keeps you warm , or turns you into a homo sapiensicle . to understand this , we need to know a little something about being cold . when your body temperature starts to plummet – you ’ re feeling heat leave you . cold can ’ t move into your body – in fact , there is no such thing as cold . where have i heard that before ? oh , right ! think of heat as an actual quantity of stuff : . the more you give away , the colder you feel . this trading of heat can happen three different ways : by convection , conduction , and radiation . all three are at play in an igloo . a person inside will radiate body heat , which moves around the igloo by convection , and is lost through the walls by conduction . this is exactly what happens in your house . living insulation does the same thing . fatty tissues like blubber help stop heat transfer in whales and seals , but for animals who don ’ t have as much junk in the trunk , they cover themselves in air . sea otter fur , for example , is about a thousand times denser than human hair . it ’ s snuggly stuff `` this is the softest thing i 've ever felt in my life . you are adorable ! '' …but the secret to its insulation power is in its texture . otter fur is spiky , so it traps insulating air molecules . and that is exactly what snowflakes do . powdery , fresh snow can be up to 95 % trapped air . this makes it an excellent insulator , but the same way you have to pack it in your hands to make a snowball , it isn ’ t dense enough to build with . solid ice , on the other hand , makes a good windbreaker , but it ’ s too heavy to lift . inuit hunters took the goldilocks approach : the secret to good igloo snow is somewhere in the middle . traditional igloo blocks aren ’ t molded , they ’ re cut out of the ground . that tightly-packed ground snow is dense enough to hold up , but because it still has far more air pockets than a block of ice , it ’ s light , and still a pretty good insulator . as usual , animals figured this one out long before humans . polar bears , groundhogs , even birds like grouse all make snow burrows to stay warm . and even before that , plants were tucking into snow to avoid death by freezing . during the warm months , heat energy from the sun builds up in soil , and just like the the roof above your head , a deep covering of snow prevents that heat from escaping onward and upward . this snowy blanket above stops ice crystals from forming inside plant roots , and shoots , and seeds . not freezing to death is a pretty good motivator for any animal to get crafty , but our big primate brains took it one step further with igloos . their engineering maximizes warmth and stability . cartoon igloos look like flat-bottomed half-spheres , but in reality , they ’ re neither of those things ! if you were to slice a real igloo in half , you ’ d see a shape called a catenary . this gradually sloping shape is the same one that would form if you held a chain from both ends and let it droop . a catenary arch distributes weight more evenly than a half circle , without bulging or buckling . in fact it ’ s one of the most stable arches in nature , so sound that we still use it today . inside , snow houses are carved in different levels . the hot air rises , and the cold air sinks down into the lower part , and away from where you would eat , sleep , and chill . to boot , body heat melts the innermost layer of the walls , strengthening the barrier between you , your airy snow-block insulation , and the frigid great beyond . when you live in an igloo , you act as a living furnace . over time , the temperature in your icy abode can hover some 40-60 degrees above the surrounding air , but bring a friend to your igloo party , and you ’ ll get warmer , faster . stay cozy , and stay curious ! `` hey , you remember that thing i said about eskimos having all those different words for snow ? well our friends from idea channel made a video about that . here 's an idea , you should go check it out . it 's pretty cool . ''
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[ music ] for thousands of years , humans , and plants and animals long before that , have been using frozen “ sky water ” to keep warm . which sort of doesn ’ t make sense . because snow is cool .
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which of these techniques is not used to make an igloo warmer ?
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how does the difference between point 0000000398 and point 00000000398 cause one to have red eyes after swimming ? to answer this , we first need a way of dealing with rather small numbers , or in some cases extremely large numbers . this leads us to the concept of logarithms . well , what are logarithms ? let 's take the base number , b , and raise it to a power , p , like 2 to the 3rd power , and have it equal a number n. we get an exponential equation : b raised to the p power , equals n. in our example , that 'd be 2 raised to the 3rd power , equals 8 . the exponent p is said to be the logarithm of the number n. most of the time this would be written : `` log , base b , of a number equals p , the power . '' this is starting to sound a bit confusing with all the variables , so let 's show this with an example . what is the value of log base 10 of 10,000 ? the same question could be asked using exponents : `` 10 raised to what power is 10,000 ? '' well , 10 to the 4th is 10,000 . so , log base 10 of 10,000 must equal 4 . this example can also be completed very simply on a scientific calculator . log base 10 is used so frequently in the sciences that it has the honor of having its own button on most calculators . if the calculator will figure out logs for me , why study them ? just a quick reminder : the log button only computes logarithms of base 10 . what if you want to go into computer science and need to understand base 2 ? so what is log base 2 of 64 ? in other words , 2 raised to what power is 64 ? well , use your fingers . 2 , 4 , 8 , 16 , 32 , 64 . so log base 2 of 64 must equal 6 . so what does this have to do with my eyes turning red in some swimming pools and not others ? well , it leads us into an interesting use of logarithms in chemistry : finding the ph of water samples . ph tells us how acidic or basic a sample is , and can be calculated with the formula : ph equals negative log base 10 of the hydrogen ion concentration , or h plus . we can find the ph of water samples with hydrogen ion concentration of point 0000000398 and point 00000000398 quickly on a calculator . punch : negative log of each of those numbers , and you 'll see the ph 's are 7.4 and 8.4 . since the tears in our eyes have a ph of about 7.4 , the h plus concentration of .0000000398 will feel nice on your eyes , but the ph of 8.4 will make you feel itchy and red . it 's easy to remember logarithms `` log base b of some number n equals p '' by repeating : `` the base raised to what power equals the number ? '' `` the base raised to what power equals the number ? '' so now we know logarithms are very powerful when dealing with extremely small or large numbers . logarithms can even be used instead of eyedrops after swimming .
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to answer this , we first need a way of dealing with rather small numbers , or in some cases extremely large numbers . this leads us to the concept of logarithms . well , what are logarithms ?
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mathematics is more than just something you learn in school . it can help us know about our bodies and our surroundings . in the video , kelly talks about using logarithms to determine what makes our eyes red after opening them underwater . what are other examples of ways mathematics can help us figure out these kinds of problems ?
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the story goes something like this : a royal , rich or righteous individual , who otherwise happens to be a lot like us , makes a mistake that sends his life , and the lives of those around him , spiraling into ruin . sound familiar ? this is the classic story pattern for greek tragedy . for thousands of years , we 've spun spellbinding tales that fit this pattern , and modern storytellers around the world continue to do so . three critical story components influenced by aristotle 's `` poetics '' help us understand the allure . first , the tragic hero should be elevated in rank and ability , but also relatable . perhaps he is a king , or extraordinary in some other way . but because you and i are neither unusually good nor unusually bad , neither is the hero . and he has one particular tragic flaw , or hamartia , something like ambition , tyranny , stubbornness , or excess pride that causes him to make a critical mistake . and from that mistake comes disaster and downfall . as an example of these elements in action , let 's look to sophocles 's `` oedipus rex , '' about a man who does n't know he was adopted , and is warned by an oracle that he 's destined to murder his father and marry his mother . in trying to escape this fate , he kills a man who wo n't get out of his way at a crossroad . he then cleverly answers the riddle of the monstrous sphynx , freeing the kingdom of thebes from a plague . he marries the widowed queen and becomes king . but after he finds out that the murdered man was his father , and the queen he married is his mother , oedipus gouges out his eyes and retreats into the wilderness . at the beginning of his story , oedipus is elevated in ability , and he 's elevated in rank . he 's neither unusually evil nor saintly . he 's relatable . notice the height of the fall . once a king , but now homeless and blind . it 's more tragic , after all , if a king falls from a tall throne than if a jester falls off his step stool . oedipus 's tragic flaw is hubris , or excessive pride , and it causes him to attempt to avoid the fate prophesied for him , which is exactly what makes it happen . he 's a particularly unlucky soul because his mistake of killing his father and marrying his mother is done in complete ignorance . of course , these narrative principles transcend classic greek tragedy . in shakespeare 's canon , we see hamlet 's indecisiveness lead to a series of bad decisions , or perhaps non-decisions , that culminate in the death of almost every character in the play , and macbeth 's ambition catapults him to the top before sending him careening to his grave . even modern pop culture staples like `` game of thrones '' and `` the dark knight '' resonate with the tropes aristotle identified over 2000 years ago . so what 's the point of all of this suffering ? according to aristotle , and many scholars since , a good tragedy can evoke fear and pity in the audience : fear of falling victim to the same or similar catastrophe , and pity for the height of the hero 's downfall . ideally , after watching these tragic events unfold , we experience catharsis , a feeling of relief and emotional purification . not everyone agrees why this happens . it may be that empathizing with the hero allows us to experience and release strong emotions that we keep bottled up , or maybe it just lets us forget about our own problems for a little while . but regardless of how you feel when you watch poor oedipus , never has there been a more salient reminder that no matter how bad things get , at least you did n't kill your father and marry your mother .
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sound familiar ? this is the classic story pattern for greek tragedy . for thousands of years , we 've spun spellbinding tales that fit this pattern , and modern storytellers around the world continue to do so .
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what ancient text has influenced our understanding of tragedy ?
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will winning the lottery make you happier ? imagine winning a multi-million dollar lottery tomorrow . if you 're like many of us , you 'd be ecstatic , unable to believe your good luck . but would that joy still be there a few years later ? maybe not . a famous study of 22 lottery winners showed that months after winning , their average reported levels of happiness had increased no more than that of a control group who had n't won the lottery . some were actually unhappier than they had been before winning . and later studies have confirmed that our emotional well-being , how often and how intensely we feel things like joy , sorrow , anxiety , or anger , do n't seem to improve with wealth or status beyond a certain point . this has to do with a phenomenon known as hedonic adaptation , or the hedonic treadmill . it describes our tendency to adapt to new situations to maintain a stable emotional equilibrium . when it comes to feeling happy , most of us seem to have a base level that stays more or less constant throughout our existence . of course , the novelty of better food , superior vacations , and more beautiful homes can at first make you feel like you 're walking on air , but as you get used to those things , you revert to your default emotional state . that might sound pretty gloomy , but hedonic adaptation makes us less emotionally sensitive to any kind of change , including negative ones . the study with the lottery winners also looked at people who had suffered an accident that left them paralyzed . when asked several months after their accidents how happy they were , they reported levels of happiness approaching their original baseline . so while the hedonic treadmill may inhibit our enjoyment of positive changes , it seems to also enable our resilience in recovering from adversity . there are other reasons that winning the lottery may not make us happier in the long run . it can be difficult to manage large sums of money , and some lottery winners wind up spending or losing it all quickly . it can also be socially isolating . some winners experience a deluge of unwelcome requests for money , so they wind up cutting themselves off from others . and wealth may actually make us meaner . in one study , participants played a rigged game of monopoly where the experimenters made some players rich quickly . the wealthy players started patronizing the poorer players and hogging the snacks they were meant to share . but just because a huge influx of cash is n't guaranteed to bring joy into your life does n't mean that money can never make us happier . findings show that we adapt to extrinsic and material things , like a new car or a bigger house , much faster than we do to novel experiences , like visiting a new place or learning a new skill . so by that reasoning , the more you spend money on experiences rather than things , the happier you 'd be . and there 's another way to turn your money into happiness : spend it on other people . in one study , participants were given some money and were either asked to spend it on themselves or on someone else . later that evening , researchers called up these participants and asked them how happy they were . the happiness levels of those who had spent the money on others were significantly greater than that of those who had spent it on themselves . and that seems to be true around the world . another study examined the generosity of over 200,000 people from 136 countries . in over 90 % of these countries , people who donated tended to be happier than those who did n't . but this may all be easier said than done . let 's say a million dollars falls into your lap tomorrow . what do you do with it ?
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so by that reasoning , the more you spend money on experiences rather than things , the happier you 'd be . and there 's another way to turn your money into happiness : spend it on other people . in one study , participants were given some money and were either asked to spend it on themselves or on someone else .
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you have received a large sum of money , the best way to ensure your happiness is to :
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translator : andrea mcdonough reviewer : bedirhan cinar picture this : your friend and you are watching a sitcom and a sassy sidekick walks into a room , carrying a four-tiered wedding cake . he trips , falls , and face-plants into the cake . your friend doubles over with laughter and says , `` it 's so ridiculous ! so ironic ! '' well , quick , what do you do ? do you laugh along with the laugh track and let this grievous misinterpretation of irony go ? or , do you throw caution to the wind and explain the true meaning of irony ? if you 're me , you choose the latter . unfortunately , irony has been completely misunderstood . we tend to throw out that term whenever we see something funny or coincidental . and while many examples of true irony can be funny , that is not the driving factor of being ironic . a situation is only ironic if what happens is the exact opposite of what was expected . if you expect a , but get b , then you have irony . let 's take the slap-stick cake situation as an example . when someone walks in precariously balancing something that should n't be carried alone , trips , falls , and makes a mess , it is funny , but it 's not ironic . in fact , you probably expect someone who is single-handedly carrying a huge cake to trip . when he does , reality aligns with expectations , and so that is not irony . but what if the sassy sidekick walked in wearing a gold medal that he 'd won at the cake walking event at the atlanta olympics in 1996 ? what if that sidekick was a professional cake carrier ? then , maybe there would have been a reasonable expectation that he would have been more skilled when carrying a ridiculously large cake . then , when that reasonable expectation was not met by the tripping sidekick , irony would have been exemplified . another example . a senior citizen texting and blogging . the common and reasonable expectation of more mature men and women is that they do n't like or know technology , that they have a hard time turning on a computer , or that they have the old brick cell phones from the 1980s . one should not expect them to be connected , high-tech , or savvy enough to text or to be blogging , which must seem like some sort of newfangled thing that `` back in my day , '' they never had . so when granny pulls out her smart phone to post pictures of her dentures or her grandkids , irony ensues . reasonable expectations of the situation are not met . that is irony . so while the cake dropper might not be ironic , there are all kinds of situations in life that are . go out , and find those true examples of irony .
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reasonable expectations of the situation are not met . that is irony . so while the cake dropper might not be ironic , there are all kinds of situations in life that are .
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why do people enjoy irony ?
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translator : andrea mcdonough reviewer : bedirhan cinar deep in the jungles of vietnam , soldiers from both sides battled heat exhaustion and each other for nearly 20 long years . but the key to communist victory was n't weapons or stamina , it was a dirt road . the ho chi minh trail , winding through vietnam , laos , and cambodia , started as a simple network of dirt roads and blossomed into the centerpiece of the winning north vietnamese strategy during the vietnam war , supplying weapons , troops , and psychological support to the south . the trail was a network of tracks , dirt roads , and river crossings that threaded west out of north vietnam and south along the truong son mountain range between vietnam and laos . the journey to the south originally took six months . but , with engineering and ingenuity , the vietnamese expanded and improved the trail . towards the end of war , as the main roads detoured through laos , it only took one week . here is how it happened . in 1959 , as relations deteriorated between the north and the south , a system of trails was constructed in order to infiltrate soldiers , weapons , and supplies into south vietnam . the first troops moved in single-file along routes used by local ethnic groups , and broken tree branches at dusty crossroads were often all that indicated the direction . initially , most of the communist cadres who came down the trail were southerners by birth who had trained in north vietnam . they dressed like civilian peasants in black , silk pajamas with a checkered scarf . they wore ho chi minh sandals on their feet , cut from truck tires , and carried their ration of cooked rice in elephants ' intestines , a linen tube hung around the body . the conditions were harsh and many deaths were caused by exposure , malaria , and amoebic dysentery . getting lost , starving to death , and the possibility of attacks by wild tigers or bears were constant threats . meals were invariably just rice and salt , and it was easy to run out . fear , boredom , and homesickness were the dominant emotions . and soldiers occupied their spare time by writing letters , drawing sketches , and drinking and smoking with local villagers . the first troops down the trail did not engage in much fighting . and after an exhausting six month trip , arriving in the south was a real highlight , often celebrated by bursting into song . by 1965 , the trip down the trail could be made by truck . thousands of trucks supplied by china and russia took up the task amidst ferocious b-52 bombing and truck drivers became known as pilots of the ground . as traffic down the trail increased , so did the u.s. bombing . they drove at night or in the early morning to avoid air strikes , and watchmen were ready to warn drivers of enemy aircraft . villages along the trail organized teams to guarantee traffic flow and to help drivers repair damage caused by air attacks . their catch cries were , `` everything for our southern brothers ! '' and , `` we will not worry about our houses if the vehicles have not yet gotten through . '' some families donated their doors and wooden beds to repair roads . vietnamese forces even used deception to get the u.s. aircraft to bomb mountainsides in order to make gravel for use in building and maintaining roads . the all-pervading red dust seeped into every nook and cranny . the ho chi minh trail had a profound impact on the vietnam war and it was the key to hanoi 's success . north vietnamese victory was not determined by the battlefields , but by the trail , which was the political , strategic , and economic lynchpin . americans recognized its achievement , calling the trail , `` one of the great achievements in military engineering of the 20th century . '' the trail is a testimony to the strength of will of the vietnamese people , and the men and women who used the trail have become folk heros .
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the trail was a network of tracks , dirt roads , and river crossings that threaded west out of north vietnam and south along the truong son mountain range between vietnam and laos . the journey to the south originally took six months . but , with engineering and ingenuity , the vietnamese expanded and improved the trail .
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the journey on the trail to south vietnam originally took how many months ?
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you might have seen this symbol before , whether it 's as a temporary tattoo or at a chinese temple . it 's called the yin-yang symbol . it comes from taoism , a religion born in china and it has far more meaning than you probably realize . the yin is the dark swirl , and the yang is the light one , and each side has a dot of the opposite color , which gives a clue to the meaning of yin and yang . everything contains the seed of its opposite . darth vadar has the seed of goodness , and luke has the potential to follow his father to the dark side . like luke and his father , yin and yang are not total opposites , they are relative to each other . taoists believe that the universe is made up of energies , vibrations , and matter , which behave differently in different contexts . something can be yin or yang depending on , well , depending on lots of things . so , while wheat that 's growing is yang , when it 's being reaped , it 's yin . a wave 's crest is yang , and the trough is yin . villages on the sunny side of a valley in china have names like liuyang or shiyang , but on the shady side , for example , of the yangtze river valley , there 's jiangyin . the brake is yin to the gas pedal 's yang . an eggshell is yang , the egg inside is yin . you think you 're getting it ? yang is harder , stronger , brighter , and faster , but one can turn into the other or are two sides of the same coin . the sunbeams are yang in comparison to the shadows . the pitch is yang , the catch is yin . the yang starts an action , and the yin receives it , completes it . yin is the inside space of a cup ; it would n't be a cup without it . yang is the cup . the coffee 's heat , however , is yang , and its blackness is yin . yang goes berserk sometimes , but there 's some very powerful yins , too , if they do n't quite go berserk . yin is the darker swirl , the female , but there is a white dot in it . and yang is the lighter , the male , but it has a black dot . water flowing calmly in a river is yin , but when it goes over the waterfall , it 's very yang . toothpicks are yin compared with a telephone pole . the back of a person is more yin than the front . the top of a person is the yang end . taoism teaches that there is a power in the universe . it 's higher , deeper , and truer than any other force . they call it the tao . it means the way . like the force in star wars , the tao has two sides . unlike other religions where the higher power is all good , and perhaps has an all-evil rival , taoism teaches that we need to learn from both yin and yang . and unlike religions with gods that are personal , the higher power in taoism is not . taoists believe that living in harmony with the way , a person will not have to fight against the universe 's natural flow . so , for example , listen more , argue less . be ready to back up or undo something , and you will make even faster progress . do n't worry about being the best , be who you are . live simply . complications take you away from the tao . `` the wise person is flexible , '' taoists say . learning to use the tao is what taoism is all about , and that 's why you should know your yin from your yang .
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you might have seen this symbol before , whether it 's as a temporary tattoo or at a chinese temple . it 's called the yin-yang symbol . it comes from taoism , a religion born in china and it has far more meaning than you probably realize .
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from its beginning as a seed to the moment you bite into it , an apple is the result of quite a journey . trace the yin and yang influences in the growth of a piece of fruit : soil , rain , sunshine , photosynthesis , flowering , the tree itself , and anything else you can think of .
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hey , vsauce . michael here . the earth is spinning and we are spinning along with it . but what if the earth suddenly stopped spinning ? well , first of all , you would gain weight . but that would be the least of your worries . the spin of our planet is important and literally giving you the time of your life . at the equator , the surface of earth , and everything on it , is spinning around at 465 meters per second . as you move closer to the poles you do n't have to move as quickly to complete earths daily rotation . here in san francisco , the earth is driving me east at 368 meters per second . if i could float above the surface independent of the earth 's rotation , the earth would spin underneath me this quickly . pretty cool . but , of course , when i jump straight up into the air , the earth does n't move underneath me because i continued to spin with it . we are all spinning with the earth and that is why slamming on a set of magical planetary breaks that caused everything classically called earth to stop spinning would be catastrophic . immediately everything that was n't earth , and was n't safely at the poles , would continue moving , as it had been , and be flung due east at more than a thousand miles an hour . you would n't be flung into space because escape velocity is 24,800 mph but your body would instantly become a 9.5 inch caliber bullet . well , really more of a supersonic tumbleweed . because the atmosphere would more gradually slow down , people in airplanes , assuming they could navigate the resulting storms , might have a better chance of surviving . astronauts aboard the iss would fare even better . but it is unlikely that anyone would be waiting for them down on the ground . runways would just be entrances to the new planet-sized graveyard , created by the no longer spinning earth . people really really near the poles might be okay but only at first . gusts of wind , as fast as those near an atomic bomb detonation , would blast , pass the surface and up into the sky forming worldwide storms of unprecedented magnitude . the friction alone , caused by the now stopped earth colliding with these winds , would be enough to cause massive fires , unparalleled erosion and damage to anything strong enough to stay put after the initial braking . the sun would seem to freeze in the sky as days became not 24 hours long but 365 days long . without spinning innards , earth 's protective magnetic field would cease to exist and we would be dosed with deadly amounts of ionising radiation from the sun . the oceans would surge onto land in tsunamis kilometers high and wash over nearly all dry land , before migrating to the poles , where gravity is stronger , no longer held to the ocean basins by the inertia earth 's spin gave them , until earth itself , no longer bulging an extra 42 kilometers around its equator , because of its rotation slowly compressed into a more perfect sphere than it is now . possibly allowing the oceans to eventually return somewhat . that is what would occur if it actually happened . it wo n't actually happen but woah , its rotation is slowing down . more on that later . first , if the earth really is spinning so quickly , why ca n't we feel it ? why does n't the earth 's rotation make us dizzy ? well , lucky for us , the change in velocity is just too gradual . the earth is too huge . it 's like driving in a car that takes 6 hours and six thousand miles to make one left turn . it 's not sudden enough to register with our senses . but that change in velocity is real and it makes us way less , because of inertia . on our spinning planet your velocity is constantly changing but always tangential to the circular path you were being dragged along . now , because inertia is a property of matter , which includes your body , without a force acting upon us we would slowly leave the surface of earth . luckily , the earth is exerting a force on us . a center-seeking , centripetal force , delivered by gravity . the centripetal force required to keep you along a circular path with earth is subtracted from earth 's total gravitational pull on you . the remaining force simply pushes you down , toward the centre of the earth - it gives you weight . at the equator , if the earth did n't spin , and no centripetal force was required to keep you with the earth , you would weigh 0.3 percent more than you currently do . if earth spun you around 17 times faster than it currently does , all of its gravitational force would go toward centripetal force fighting against your inertia and you would be weightless . so here 's a diet idea . hope that the earth starts spinning faster and go back for guilt-free seconds . seconds . we know exactly how long a second is . the outermost electron of an atom of cesium 133 is alone . when the atom is undisturbed , only the nucleus interacts with this outermost electron , tickling it regularly and rapidly between two levels . after 9,192,631,770 oscillations between those two levels , one second has passed . exactly . that is literally the definition of a second . we can measure and count those oscillations . it 's how atomic clocks work . making atomic clocks , the most accurate measurement device ever built by humans , to measure anything . we ca n't define a second more simply , as say , 1/60th of 1/60th of 1/24th of a day because of earth 's spin . it 's too irregular . little changes in the distribution of mass on earth , caused by earthquakes or melting ice or man-made dams or technically even you walking up stairs or downstairs , cause earth 's rotational speed to change . like a figure skater moving their arms further away from or closer to their bodies . now add on top of that the fact that tides , caused by the moon , drag against earth 's rotation and you wind up with an unstable rotation speed that is predominately slowing down . now , these changes are incredibly incredibly slight , but over time they add up . in 140 million years , a day on earth will not be 24 hours long , it will be 25 . that might not sound like much but in order to do important things , like deliver accurate gps information , we need a more accurate timekeeping device than that . so , as a solution scientists keep the pace of seconds using atomic clocks , tai time . and other scientists measure the changing speed of earth 's rotation by observing distant stars and quasars . now , every few months they find out just how behind or ahead earth is running , and if it 's getting too close to being a second off , they decide to add or subtract the second from the current year . the result is the time used almost everywhere , including your phone : utc . since this system began in 1972 25 leap seconds have been added . what this means is that clock time is , and has to be , a manufactured product with upgrades and tune ups administered periodically , after defects are noticed . the time we give to now and the future is only ever approximate . that 's weird but it 's also entirely not weird . as demetrios matsakis , the chief scientist of time services for the us naval observatory puts it , `` we save lives and we end lives . we add time and we can take time away , but in both cases we do so without completely understanding exactly what life is , or what time is . '' regardless , thank you for spending some of yours with me ... and as always , thanks for watching .
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the earth is spinning and we are spinning along with it . but what if the earth suddenly stopped spinning ? well , first of all , you would gain weight .
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if the earth suddenly stopped spinning , which of the following would occur ?
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you may know that it takes light a zippy eight minutes to reach us from the surface of the sun , so how long do you think it takes light to travel from the sun 's core to its surface ? a few seconds or a minute at most ? well , oddly enough , the answer is many thousands of years . here 's why . photons are produced by the nuclear reactions deep in the core of our sun . as the photons flow out of the core , they interact with matter and lose energy , becoming longer wavelength forms of light . they start out as gamma rays in the core , but end up as x-rays , ultraviolet or visible light as they near the surface . however , that journey is neither simple nor direct . upon being born , each photon travels at a speed of 300,000 kilometers per second until it collides with a proton and is diverted in another direction , acting like a bullet ricocheting off of every charged particle it strikes . the question of how far this photon gets from the center of the sun after each collision is known as the random walk problem . the answer is given by this formula : distance equals step size times the square root of the number of steps . so if you were taking a random walk from your front door with a one meter stride each second , it would take you a million steps and eleven days just to travel one kilometer . so then how long does it take for a photon generated in the center of the sun to reach you ? we know the mass of the sun and can use that to calculate the number of protons within it . let 's assume for a second that all the sun 's protons are evenly spread out , making the average distance between them about 1.0 x 10^-10 meters . to random walk the 690,000 kilometers from the core to the solar surface would then require 3.9 x 10^37 steps , giving a total travel time of 400 billion years . hmm , that ca n't be right . the sun is only 4.6 billion years old , so what went wrong ? two things : the sun is n't actually of uniform density and photons will miss quite a few protons between every collision . in actuality , a photon 's energy , which changes over the course of its journey , determines how likely it is to interact with a proton . on the density question , our models show that the sun has a hot core , where the fusion reactions occur . surrounding that is the radiative zone , followed by the convective zone , which extends all the way to the surface . the material in the core is much denser than lead , while the hot plasma near the surface is a million times less dense with a continuum of densities in between . and here 's the photon-energy relationship . for a photon that carries a small amount of energy , a proton is effectively huge , and it 's much more likely to cause the photon to ricochet . and for a high-energy photon , the opposite is true . protons are effectively tiny . photons start off at very high energies compared to when they 're finally radiated from the sun 's surface . now when we use a computer and a sophisticated solar interior model to calculate the random walk equation with these changing quantities , it spits out the following number : 170,000 years . future discoveries about the sun may refine this number further , but for now , to the best of our understanding , the light that 's hitting your eyes today spent 170,000 years pinballing its way towards the sun 's surface , plus eight miniscule minutes in space . in other words , that photon began its journey two ice ages ago , around the same time when humans first started wearing clothes .
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however , that journey is neither simple nor direct . upon being born , each photon travels at a speed of 300,000 kilometers per second until it collides with a proton and is diverted in another direction , acting like a bullet ricocheting off of every charged particle it strikes . the question of how far this photon gets from the center of the sun after each collision is known as the random walk problem .
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what do fast moving photons collide with to get diverted in another direction ?
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in 1956 , during a diplomatic reception in moscow , soviet leader nikita khrushchev told western bloc ambassadors , `` my vas pokhoronim ! '' his interpreter rendered that into english as , `` we will bury you ! '' this statement sent shockwaves through the western world , heightening the tension between the soviet union and the us who were in the thick of the cold war . some believe this incident alone set east/west relations back a decade . as it turns out , khrushchev 's remark was translated a bit too literally . given the context , his words should have been rendered as , `` we will live to see you buried , '' meaning that communism would outlast capitalism , a less threatening comment . though the intended meaning was eventually clarified , the initial impact of khrushchev 's apparent words put the world on a path that could have led to nuclear armageddon . so now , given the complexities of language and cultural exchange , how does this sort of thing not happen all the time ? much of the answer lies with the skill and training of interpreters to overcome language barriers . for most of history , interpretation was mainly done consecutively , with speakers and interpreters making pauses to allow each other to speak . but after the advent of radio technology , a new simultaneous interpretations system was developed in the wake of world war ii . in the simultaneous mode interpreters instantaneously translate a speaker 's words into a microphone while he speaks . without pauses , those in the audience can choose the language in which they want to follow . on the surface , it all looks seamless , but behind the scenes , human interpreters work incessantly to ensure every idea gets across as intended . and that is no easy task . it takes about two years of training for already fluent bilingual professionals to expand their vocabulary and master the skills necessary to become a conference interpreter . to get used to the unnatural task of speaking while they listen , students shadow speakers and repeat their every word exactly as heard in the same language . in time , they begin to paraphrase what is said , making stylistic adjustments as they go . at some point , a second language is introduced . practicing in this way creates new neural pathways in the interpreter 's brain , and the constant effort of reformulation gradually becomes second nature . over time and through much hard work , the interpreter masters a vast array of tricks to keep up with speed , deal with challenging terminology , and handle a multitude of foreign accents . they may resort to acronyms to shorten long names , choose generic terms over specific , or refer to slides and other visual aides . they can even leave a term in the original language , while they search for the most accurate equivalent . interpreters are also skilled at keeping aplomb in the face of chaos . remember , they have no control over who is going to say what , or how articulate the speaker will sound . a curveball can be thrown at any time . also , they often perform to thousands of people and in very intimidating settings , like the un general assembly . to keep their emotions in check , they carefully prepare for an assignment , building glossaries in advance , reading voraciously about the subject matter , and reviewing previous talks on the topic . finally , interpreters work in pairs . while one colleague is busy translating incoming speeches in real time , the other gives support by locating documents , looking up words , and tracking down pertinent information . because simultaneous interpretation requires intense concentration , every 30 minutes , the pair switches roles . success is heavily dependent on skillful collaboration . language is complex , and when abstract or nuanced concepts get lost in translation , the consequences may be catastrophic . as margaret atwood famously noted , `` war is what happens when language fails . '' conference interpreters of all people are aware of that and work diligently behind the scenes to make sure it never does .
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while one colleague is busy translating incoming speeches in real time , the other gives support by locating documents , looking up words , and tracking down pertinent information . because simultaneous interpretation requires intense concentration , every 30 minutes , the pair switches roles . success is heavily dependent on skillful collaboration .
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which of the following is not true with regard to conference ( simultaneous ) interpretation ?
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so here we have a sample of cobalt . now i have got lots and lots of different samples of cobalt in my drawer , so this is cobalt sponge . cobalt is , in many ways , similar to iron . it can form magnets . so this cobalt has been generated from a solution and it ’ s been made in very , very finely dispersed so it has a very large surface area . it ’ s very good for doing catalytic reactions . the magnets that you use in colour televisions , for the loud speakers , contain cobalt . you need to use cobalt in the magnets in the colour television or the old sort of colour television not the ones with lcd screens because the magnetic fields from larger magnets could affect the electron guns and so spoil the colours so you need a very small magnet on your loud speaker or the colours all go funny . cobalt sponge absorbs lots and lots of gas for perhaps hydrogenation . many years ago , in the 1970s , when there was a civil war in africa in the region katanga where cobalt is mined , there was a shortage of cobalt and the production of colour televisions stopped for some considerable time until the production restarted . so you can see it flows in the bottle . so i have another sample of cobalt and that is simply a foil . so again that is a very nice malleable tin-type foil ; very , very good structures .
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cobalt is , in many ways , similar to iron . it can form magnets . so this cobalt has been generated from a solution and it ’ s been made in very , very finely dispersed so it has a very large surface area .
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as pete explains , the perfect form for a catalyst to promote chemical reactions is as a very fine powder . why would this be ?
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twenty-one grams . that is the mass of all of the electrons in your body if , like me , you weigh about 70 kilograms . now all of the mass comes from the higgs mechanism , which means that as your electrons are traveling through space time , they interact with the higgs field and it is that that gives them their mass . it slows them down and stops them from traveling at the speed of light . but most of your mass doesn ’ t come from the higgs mechanism . and neither does all of this stuff that you see around you . the mass is coming from somewhere quite different and that is because most of your mass and most of this mass comes from neutrons and protons and they are not fundamental particles . they are made of constituent particles called quarks . now the theory that describes quarks and their interactions with each other through gluons is called quantum chromo dynamics . and chromo is the greek word for color . so in some way these objects are meant to carry the color charge . but they are much , much smaller than the wavelength of visible light , so there is no way that they are actually colored , but it is a useful analogy that helps us think about how they interact and the particles that they can make up . now the rules are pretty simple . in order for a particle to exist , it must be colorless or white , like this house . now you can accomplish that in two different ways . you could make three quarks in where each one is a different color , red , green and blue , so overall they combine to produce white . or you could use a quark and an anti quark where one is a color like green and the other is its anti color , say , magenta . now what i would like to do on this little patch of beach behind me is simulate how quarks actually bind together and form different particles . now for this you need to remember that in the last video we talked about how empty space is not truly empty . so the beach here is has these undulations in it which represent the fluctuations in the gluon field . but you have to imagine this beach sort of rippling and these bumps coming and going . now that is really important , because to get rid of those fluctuations actually takes energy . and this is an important part of binding the quarks together . the existence of quarks actually suppresses the gluon fluctuations and creates what is called a flux tube , an area where there is really nothing in the vacuum and that is in between this quark and the anti quark . and that pairs them up and creates what is called a meson , the quark , anti quark pair . what is interesting about that flux tube is that as these quarks become more separated , the flux tube remains the same diameter and the same sort of depth of suppression of the field , which means that the force does n't actually increase . it is not like a spring . it is not like an elastic band . the force is the same that is pulling these quarks back together . but you are putting more work in as you move these quarks and anti quarks further apart . and so for a time people thought : well , these quarks are always going t be confined , however far you move them . you are just going to get a really long flux tube . but what actually happens is you that you put in enough energy that you can actually create a quark , anti quark pair . > > nevertheless , the quarks are still combined . you can never see an individual quark , because if you try to pull it out , you put so much energy into the situation that another quark , anti quark pair will be created . > > now to form a proton , we are going to need an up quark , another up quark and a down quark . now the standard model of a proton that you have probably seen involves these quarks bounded together by little gluon springs that go between them . > > we know that that picture is totally wrong now . even in the best sense you might have hoped that you would see flux tubes around the edge of the triangle . but we know that , in fact , they don ’ t do that . that you get these y shaped flex tubes . > > the crazy thing about a proton is that there may be more than three quarks there . you see , you can have additional quark , anti quark pairs pop in and out of existence . so at any given time there could be five or seven or nine , any odd number of quarks could make up a proton . so this is what a proton actually looks like . you can see that the quarks like to sit on those lumps in the gluon field . and you can see the two up quarks and a down quark , but there is also a strange quark and an anti strange quark , which is strange , because you don ’ t normally think of these quarks being inside a proton , but they can be at any particular point in time . and you can also see that these quarks have cleared out the vacuum . and you can see that there is kind of these flux tubes which are the areas where the gluon field has been suppressed . and that is really what is binding these quarks together . > > that is the strong force that binds quarks into the heart of the proton . > > it is intrinsically related to the fact that clearing out those fluctuations has more energy than where they are . > > that is right . it costs energy to clear the vacuum . > > so where is the mass of the proton really coming from ? well , of course , the constituent quarks do interact with the higgs field and that gives them a small amount of mass . but if you add up the mass of all the quarks in the proton it would only account for about one percent of its total mass . so where is the rest of the mass coming from ? the answer is : energy . you know , einstein ’ s famous equation : e equals mc squared . well , that says we have got a lot of energy for just a little bit of a mass . but if you rearrange the equation you can see that we can get an amount of mass if there is lots of energy there . and that is really where most of the mass of the proton is coming from . it is from the fact that there are these energy fluctuations in the gluon field and the quarks are interacting with those gluons . that is where your mass is coming from . it is coming from the energy that is in there . you know , einstein talked about , well , if i had a hot cup of tea , it would actually have a slightly greater mass than the same cup of tea when cold . and he was right . i mean , you can ’ t measure it with a cup of tea , but most of your mass you owe to e equals mc squared , you owe to the fact that your mass is packed with energy , because of the interactions between the quarks and these gluon fluctuations in that gluon field . i think it is extraordinary , because what we think of as ordinarily empty space , you know , that turns out to be the thing that gives us all most of our mass . i really want to thank audible.com for supporting this episode of veritasium . in case you don ’ t know , audble.com is a leading provider of audio books with over 100,000 titles in all areas of literature including fiction , non fiction and periodicals . you know , one of my favorite books is by james gleick . it is called the information : a history , a theory , a flood . and if you head on over to audible.com/veritasium you can download it right now for free . or you could pick another book of your choosing . you know , it is great to have support from people like audible , because that allows me to keep this content for you for free . so please go check it out .
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well , of course , the constituent quarks do interact with the higgs field and that gives them a small amount of mass . but if you add up the mass of all the quarks in the proton it would only account for about one percent of its total mass . so where is the rest of the mass coming from ?
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if you had the same mass as the host of this video , and you added up the mass of all of your electrons , how many grams of electrons would you have ?
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selenium . so selenium is an element that ’ s quite like sulphur . but , sulphur has its common form in s8 rings whereas selenium exists in its more common form as long chains of selenium atoms and if you shine light on these chains they start conducting electricity . so selenium was the material that was used in the early photo cells for things like burglar alarms and doors that open themselves and so on . so here is a sample of selenium and we ’ re going to unpack it from the box here . and it ’ s in the form of a shot . selenium has a number of other applications and perhaps the one that amuses me most is that it ’ s used in shampoos . some people , as you know , get dandruff which is caused by bacteria on their scalp and if you use a compound which is a ring , which is a mixture of sulphur and selenium , this can be added to shampoo and will act as a bactericide and will kill bacteria that cause dandruff . so let ’ s see what comes out . i can hear it and here you can see the selenium , wonderful black compound . beautiful element , again this is a mineral which is useful for us and in fact many people often take selenium as an additive to their diet . however you have to be careful because the compounds that make our sweat smell are sulphur compounds , so if you get selenium into the body then you make similar compounds of selenium but which smell much worse . and so it is said that people get off the bus when selenium chemists get on . and tellurium is even worse still .
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selenium . so selenium is an element that ’ s quite like sulphur .
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what is the main difference between the naturally occurring forms of sulfur and selenium ?
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what if you could only see one color ? imagine , for instance , that you could only see things that were red and that everything else was completely invisible to you . as it turns out , that 's how you live your life all the time because your eyes can only see a minuscule part of the full spectrum of light . different kinds of light are all around you everyday but are invisible to the human eye , from the radio waves that carry your favorite songs , to the x-rays doctors use to see inside of you , to the microwaves that heat up your food . in order to understand how these can all be light , we 'll need to know a thing or two about what light is . light is electromagnetic radiation that acts like both a wave and a particle . light waves are kind of like waves on the ocean . there are big waves and small waves , waves that crash on the shore one right after the other , and waves that only roll in every so often . the size of a wave is called its wavelength , and how often it comes by is called its frequency . imagine being a boat in that ocean , bobbing up and down as the waves go by . if the waves that day have long wavelengths , they 'll make you bob only so often , or at a low frequency . if the waves , instead , have short wavelengths , they 'll be close together , and you 'll bob up and down much more often , at a high frequency . different kinds of light are all waves , they just have different wavelengths and frequencies . if you know the wavelength or frequency of a wave of light , you can also figure out its energy . long wavelengths have low energies , while short wavelengths have high energies . it 's easy to remember if you think about being in that boat . if you were out sailing on a day with short , choppy waves , you 'd probably be pretty high energy yourself , running around to keep things from falling over . but on a long wavelength sea , you 'd be rolling along , relaxed , low energy . the energy of light tells us how it will interact with matter , for example , the cells of our eyes . when we see , it 's because the energy of light stimulates a receptor in our eye called the retina . our retina are only sensitive to light with a very small range in energy , and so we call that range of light visible light . inside our retina are special receptors called rods and cones . the rods measure brightness , so we know how much light there is . the cones are in charge of what color of light we see because different cones are sensitive to different energies of light . some cones are more excited by light that is long wavelength and low energy , and other cones are more excited by short wavelength , high-energy light . when light hits our eye , the relative amount of energy each cone measures signals our brain to perceive colors . the rainbow we perceive is actually visible light in order of its energy . at one side of the rainbow is low-energy light we see as red , and at the other side is high-energy light we see as blue . if light shines on us that has an energy our retina ca n't measure , we wo n't be able to see it . light that is too short wavelength or high energy gets absorbed by the eye 's surface before it can even get to the retina , and light that is too long wavelength does n't have enough energy to stimulate our retina at all . the only thing that makes one kind of light different from another is its wavelength . radio waves have long wavelengths , while x-rays have short wavelengths . and visible light , the kind you can actually see , is somewhere in between . even though our eyes ca n't detect light outside of the visible range , we can build special detectors that are stimulated by these other wavelengths of light , kind of like digital eyes . with these devices , we can measure the light that is there , even though we ca n't see it ourselves . so , take a step back and think about all of this for a moment . even though they seem different , the warmth you feel from a crackling fire is the same as the sun shining on you on a beautiful day , the same as ultraviolet light you put on sunscreen to protect yourself from , the same thing as your tv , your radio , and your microwave . now , those examples are all things here on earth , things you experience in your everyday life , but here 's something even more amazing . our universe gives off the full spectrum of light , too . when you think of the night sky , you probably think of being able to see the stars shining with your own eyes , but that 's just visible light , which you now know is only a tiny part of the full spectrum . if we had to draw the universe and could only use visible light , it would be like having only one crayon -- pretty sad . to see the universe in its full spectrum , we need to have the right eyes , and that means using special telescopes that can help us see beyond visible light . you 've probably heard of the hubble space telescope and seen its beautiful pictures taken in visible and ultraviolet light . but you might not know that there are 20 space telescopes in orbit , missions that can each see part of the full spectrum of light . with telescopes acting as our virtual eyes , both in space and here on earth , we can see some amazing things . and the coolest thing of all , no matter the wavelength or energy , the light that we see out in the distant universe is the same thing as the light that we can experience and study here on earth . so , since we know the physics of how x-ray , ultraviolet light , or microwaves work here , we can study the light of a distant star or galaxy and know what kinds of things are happening there too . so , as you go about your daily life , think beyond what your eyes can and ca n't see . knowing just a little bit about the natural world can help you perceive the full spectrum around you all the time .
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different kinds of light are all waves , they just have different wavelengths and frequencies . if you know the wavelength or frequency of a wave of light , you can also figure out its energy . long wavelengths have low energies , while short wavelengths have high energies .
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explain the differences in wavelength and frequency .
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translator : tom carter reviewer : bedirhan cinar every minute of every day , you breathe without even thinking about it . your body does it on its own , from the day you 're born until the day you die . you have muscles contract to bring oxygen , a gas , into your lungs , which is then transferred by your bloodstream to every cell in your body . gases are strange . we ca n't see them , but we know they 're there because we can feel them . what we experience as wind is really trillions and trillions of gas molecules slamming into your body . and it feels good , right ? science is based on observation . unfortunately , we can not observe gases with our eyes -- they 're too small . we have to use our other senses to make observations and draw conclusions . observations are then compiled , and we create a model . no , not that kind of model . a model is a way scientists describe the properties of physical phenomena . first , gases always move in a straight line . we do n't really have anything to demonstrate this with because gravity always pulls objects down . so imagine a bullet fired from a gun , and that bullet goes on at a constant speed in a perfectly straight line . that would be like a gas molecule . second , gases are so small , they occupy no volume on their own . as a group they do , blow up any balloon and you can see how that volume changes . but single gases have no volume compared to other forms of matter . rather than calculating such a small amount of matter , we just call it zero for simplicity . third , if gas molecules collide , and they do -- remember , these are assumptions -- their energy remains constant . an easy way to demonstrate this is by dropping a soccer ball with a tennis ball balanced on top . because the soccer ball is bigger , it has more potential energy , and the energy from the larger ball is transferred to the smaller tennis ball and it flies away when that energy is transferred . the total energy stays the same . gases work the same way . if they collide , smaller particles will speed up , larger particles will slow down . the total energy is constant . fourth , gases do not attract one another , and they do n't like to touch . but remember rule three . in reality , they do collide . finally , gases have energy that is proportional to the temperature . the higher the temperature , the higher the energy the gases have . the crazy thing is that at the same temperature , all gases have the same energy . it does n't depend on the type of gas , just the temperature that gas is at . keep in mind this is a model for the way gas particles behave , and based on our observations , gases always move in straight lines . they 're so small , that they 're not measurable on their own , and they do n't interact with one another . but if they do bump into one another , that energy is transferred from one particle to another , and the total amount never changes . temperature has a major effect , and in fact , all gases at the same temperature have the same average energy . whew ! i need to go catch my breath .
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so imagine a bullet fired from a gun , and that bullet goes on at a constant speed in a perfectly straight line . that would be like a gas molecule . second , gases are so small , they occupy no volume on their own .
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most hot air balloons are round . yes , you can have some other shapes like this one , but its shape is still rounded . using the assumptions , explain why a square hot air balloon would be hard to make .
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imagine setting sail from hawaii in a canoe . your target is a small island thousands of kilometers away in the middle of the pacific ocean . that 's a body of water that covers more than 160 million square kilometers , greater than all the landmasses on earth combined . for thousands of years , polynesian navigators managed voyages like this without the help of modern navigational aids . ancient polynesians used the sun , moon , stars , planets , ocean currents , and clouds as guides that allowed them to see the ocean as a series of pathways rather than an obstacle . their voyages began around 1500 b.c . when the people who would settle polynesia first set sail from southeast asia . early polynesians eventually settled a vast area of islands spread over 40 million square kilometers of the pacific ocean . some historians believe the voyagers moved from place to place to avoid overpopulation . others , that they were driven by war . voyages became less frequent by around 1300 a.d. as polynesian societies became more rooted in specific locations . during the voyaging period , successful journeys depended on a number of factors : well-built canoes , the skill of navigators , and weather being some of the biggest . voyages relied on sturdy wa'a kaulua , or double-hulled canoes , which were powered by sails and steered with a single large oar . canoe building involved the whole community , bringing together the navigators , canoe builders , priests , chanters , and hula dancers . navigators were keen observers of the natural world . they were abundantly familiar with trade wind-generated ocean swells , which typically flow northeast or southeast . by day , navigators could identify direction by the rocking motion of their canoes caused by these swells . but sunrise and sunset were even more useful . the sun 's position indicated east and west and created low light on the ocean that made it possible to see swells directly . at night , navigators used something called a star compass , which was n't a physical object , but rather a sort of mental map . they memorized the rising and setting points of stars and constellations at different times of the year . they used those to divide the sky into four quadrants , subdivided into 32 houses , with the canoe in the middle . so , for example , when they saw the star pira ‘ atea rising from the ocean , they knew that to be northeast . they had some other tricks , too . the earth 's axis points towards hokupa'a , or the north star , so called because it 's the one fixed point in the sky as the earth rotates and always indicates north . however , it 's not visible south of the equator , so navigators there could use a constellation called newe , or the southern cross , and some mental tricks to estimate where south is . for instance , draw a line through these two stars , extend it 4.5 times , and draw another line from there to the horizon . that 's south . but the sky also contains navigational aids much closer to earth , the clouds . besides being useful weather cues , under the right conditions , they can indicate landmasses . for instance , the lagoons of pacific atolls can actually be seen reflected on the underside of clouds , if you know what to look for . and high masses of clouds can indicate mountainous islands . once navigators neared their destination , other clues , such as the flight patterns of birds , floating debris or vegetation , and types of fish in the area helped determine the proximity of land . for example , the manu-o-ku had a known flight range of 190 kilometers , and could be followed back to shore . so how do we know all of this ? partially through evidence in petroglyphs , written observations of european explorers , and polynesian oral traditions . but also by trying them out for ourselves . in 2017 , a voyaging canoe called hokulea completed a worldwide voyage using only these techniques . if that seems remarkable , remember the ancient polynesians , who through close study and kinship with nature , were able to forge these paths across an unfathomably vast , vibrant living ocean .
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navigators were keen observers of the natural world . they were abundantly familiar with trade wind-generated ocean swells , which typically flow northeast or southeast . by day , navigators could identify direction by the rocking motion of their canoes caused by these swells . but sunrise and sunset were even more useful .
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how did the navigator use ocean swells to determine direction ?
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this is a crystal of sugar . if you press on it , it will actually generate its own electricity . how can this simple crystal act like a tiny power source ? because sugar is piezoelectric . piezoelectric materials turn mechanical stress , like pressure , sound waves , and other vibrations into electricity and vice versa . this odd phenomenon was first discovered by the physicist pierre curie and his brother jacques in 1880 . they discovered that if they compressed thin slices of certain crystals , positive and negative charges would appear on opposite faces . this difference in charge , or voltage , meant that the compressed crystal could drive current through a circuit , like a battery . and it worked the other way around , too . running electricity through these crystals made them change shape . both of these results , turning mechanical energy into electrical , and electrical energy into mechanical , were remarkable . but the discovery went uncelebrated for several decades . the first practical application was in sonar instruments used to detect german submarines during world war i. piezoelectric quartz crystals in the sonar 's transmitter vibrated when they were subjected to alternating voltage . that sent ultrasound waves through the water . measuring how long it took these waves to bounce back from an object revealed how far away it was . for the opposite transformation , converting mechanical energy to electrical , consider the lights that turn on when you clap . clapping your hands send sound vibrations through the air and causes the piezo element to bend back and forth . this creates a voltage that can drive enough current to light up the leds , though it 's conventional sources of electricity that keep them on . so what makes a material piezoelectric ? the answer depends on two factors : the materials atomic structure , and how electric charge is distributed within it . many materials are crystalline , meaning they 're made of atoms or ions arranged in an orderly three-dimensional pattern . that pattern has a building block called a unit cell that repeats over and over . in most non-piezoelectric crystalline materials , the atoms in their unit cells are distributed symmetrically around a central point . but some crystalline materials do n't possess a center of symmetry making them candidates for piezoelectricity . let 's look at quartz , a piezoelectric material made of silicon and oxygen . the oxygens have a slight negative charge and silicons have a slight positive , creating a separation of charge , or a dipole along each bond . normally , these dipoles cancel each other out , so there 's no net separation of charge in the unit cell . but if a quartz crystal is squeezed along a certain direction , the atoms shift . because of the resulting asymmetry in charge distribution , the dipoles no longer cancel each other out . the stretched cell ends up with a net negative charge on one side and a net positive on the other . this charge imbalance is repeated all the way through the material , and opposite charges collect on opposite faces of the crystal . this results in a voltage that can drive electricity through a circuit . piezoelectric materials can have different structures . but what they all have in common is unit cells which lack a center of symmetry . and the stronger the compression on piezoelectric materials , the larger the voltage generated . stretch the crystal , instead , and the voltage will switch , making current flow the other way . more materials are piezoelectric than you might think . dna , bone , and silk all have this ability to turn mechanical energy into electrical . scientists have created a variety of synthetic piezoelectric materials and found applications for them in everything from medical imaging to ink jet printers . piezoelectricity is responsible for the rhythmic oscillations of the quartz crystals that keep watches running on time , the speakers of musical birthday cards , and the spark that ignites the gas in some barbecue grill lighters when you flick the switch . and piezoelectric devices may become even more common since electricity is in high demand and mechanical energy is abundant . there are already train stations that use passengers ' footsteps to power the ticket gates and displays and a dance club where piezoelectricity helps power the lights . could basketball players running back and forth power the scoreboard ? or might walking down the street charge your electronic devices ? what 's next for piezoelectricity ?
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in most non-piezoelectric crystalline materials , the atoms in their unit cells are distributed symmetrically around a central point . but some crystalline materials do n't possess a center of symmetry making them candidates for piezoelectricity . let 's look at quartz , a piezoelectric material made of silicon and oxygen .
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why are regular crystalline materials ( with a center of symmetry in their structure ) not capable of exhibiting piezoelectricity ?
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light : it 's the fastest thing in the universe , but we can still measure its speed if we slow down the animation , we can analyze light 's motion using a space-time diagram , which takes a flipbook of animation panels , and turns them on their side . in this lesson , we 'll add the single experimental fact that whenever anyone measures just how fast light moves , they get the same answer : 299,792,458 meters every second , which means that when we draw light on our space-time diagram , it 's world line always has to appear at the same angle . but we saw previously that speed , or equivalently world line angles , change when we look at things from other people 's perspective . to explore this contradiction , let 's see what happens if i start moving while i stand still and shine the laser at tom . first , we 'll need to construct the space-time diagram . yes , that means taking all of the different panels showing the different moments in time and stacking them up . from the side , we see the world line of the laser light at its correct fixed angle , just as before . so far , so good . but that space-time diagram represents andrew 's perspective . what does it look like to me ? in the last lesson , we showed how to get tom 's perspective moving all the panels along a bit until his world line is completely vertical . but look carefully at the light world line . the rearrangement of the panels means it 's now tilted over too far . i 'd measure light traveling faster than andrew would . but every experiment we 've ever done , and we 've tried very hard , says that everyone measures light to have a fixed speed . so let 's start again . in the 1900s , a clever chap named albert einstein worked out how to see things properly , from tom 's point of view , while still getting the speed of light right . first , we need to glue together the separate panels into one solid block . this gives us our space-time , turning space and time into one smooth , continuous material . and now , here is the trick . what you do is stretch your block of space-time along the light world line , then squash it by the same amount , but at right angles to the light world line , and abracadabra ! tom 's world line has gone vertical , so this does represent the world from his point of view , but most importantly , the light world line has never changed its angle , and so light will be measured by tom going at the correct speed . this superb trick is known as a lorentz transformation . yeah , more than a trick . slice up the space-time into new panels and you have the physically correct animation . i 'm stationary in the car , everything else is coming past me and the speed of light works out to be that same fixed value that we know everyone measures . on the other hand , something strange has happened . the fence posts are n't spaced a meter apart anymore , and my mom will be worried that i look a bit thin . but that 's not fair . why do n't i get to look thin ? i thought physics was supposed to be the same for everyone . yes , no , it is , and you do . all that stretching and squashing of space-time has just muddled together what we used to think of separately as space and time . this particular squashing effect is known as lorentz contraction . okay , but i still do n't look thin . no , yes , you do . now that we know better about space-time , we should redraw what the scene looked like to me . to you , i appear lorentz contracted . oh but to you , i appear lorentz contracted . yes . uh , well , at least it 's fair . and speaking of fairness , just as space gets muddled with time , time also gets muddled with space , in an effect known as time dilation . no , at everyday speeds , such as tom 's car reaches , actually all the effects are much , much smaller than we 've illustrated them . oh , yet , careful experiments , for instance watching the behavior of tiny particles whizzing around the large hadron collider confirmed that the effects are real . and now that space-time is an experimentally confirmed part of reality , we can get a bit more ambitious . what if we were to start playing with the material of space-time itself ? we 'll find out all about that in the next animation .
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in this lesson , we 'll add the single experimental fact that whenever anyone measures just how fast light moves , they get the same answer : 299,792,458 meters every second , which means that when we draw light on our space-time diagram , it 's world line always has to appear at the same angle . but we saw previously that speed , or equivalently world line angles , change when we look at things from other people 's perspective . to explore this contradiction , let 's see what happens if i start moving while i stand still and shine the laser at tom .
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why doesn ’ t sliding the panels to change perspective work when we have light in the picture ?
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`` hi , bob . '' `` morning , kelly . the tulips looks great . '' have you ever wondered how your dog experiences the world ? here 's what she sees . not terribly interesting . but what she smells , that 's a totally different story . and it begins at her wonderfully developed nose . as your dog catches the first hints of fresh air , her nose 's moist , spongy outside helps capture any scents the breeze carries . the ability to smell separately with each nostril , smelling in stereo , helps to determine the direction of the smell 's source so that within the first few moments of sniffing , the dog starts to become aware of not just what kind of things are out there but also where they 're located . as air enters the nose , a small fold of tissue divides it into two separate folds , one for breathing and one just for smelling . this second airflow enters a region filled with highly specialized olfactory receptor cells , several hundred millions of them , compaired to our five million . and unlike our clumsy way of breathing in and out through the same passage , dogs exhale through slits at the side of their nose , creating swirls of air that help draw in new odor molecules and allow odor concentration to build up over mulitple sniffs . but all that impressive nasal architecture would n't be much help without something to process the loads of information the nose scoops up . and it turns out that the olfactory system dedicated to proessing smells takes up many times more relative brain area in dogs than in humans . all of this allows dogs to distinguish and remember a staggering variety of specific scents at concentrations up to 100 million times less than what our noses can detect . if you can smell a spritz of perfume in a small room , a dog would have no trouble smelling it in an enclosed stadium and distinguishing its ingredients , to boot . and everything in the street , every passing person or car , any contents of the neighbor 's trash , each type of tree , and all the birds and insects in it has a distinct odor profile telling your dog what it is , where it is , and which direction it 's moving in . besides being much more powerful than ours , a dog 's sense of smell can pick up things that ca n't even be seen at all . a whole separate olfactory system , called the vomeronasal organ , above the roof of the mouth , detects the hormones all animals , including humans , naturally release . it lets dogs identify potential mates , or distinguish between friendly and hostile animals . it alerts them to our various emotional states , and it can even tell them when someone is pregnant or sick . because olfaction is more primal than other senses , bypassing the thalamus to connect directly to the brain structures involving emotion and instinct , we might even say a dog 's perception is more immediate and visceral than ours . but the most amazing thing about your dog 's nose is that it can traverse time . the past appears in tracks left by passersby , and by the warmth of a recently parked car where the residue of where you 've been and what you 've done recently . landmarks like fire hydrants and trees are aromatic bulletin boards carrying messages of who 's been by , what they 've been eating , and how they 're feeling . and the future is in the breeze , alerting them to something or someone approaching long before you see them . where we see and hear something at a single moment , a dog smells an entire story from start to finish . in some of the best examples of canine-human collaboration , dogs help us by sharing and reacting to those stories . they can respond with kindness to people in distress , or with aggression to threats because stress and anger manifest as a cloud of hormones recognizable to the dog 's nose . with the proper training , they can even alert us to invisible threats ranging from bombs to cancer . as it turns out , humanity 's best friend is not one who experiences the same things we do , but one whose incredible nose reveals a whole other world beyond our eyes .
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but what she smells , that 's a totally different story . and it begins at her wonderfully developed nose . as your dog catches the first hints of fresh air , her nose 's moist , spongy outside helps capture any scents the breeze carries . the ability to smell separately with each nostril , smelling in stereo , helps to determine the direction of the smell 's source so that within the first few moments of sniffing , the dog starts to become aware of not just what kind of things are out there but also where they 're located . as air enters the nose , a small fold of tissue divides it into two separate folds , one for breathing and one just for smelling .
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dogs can smell separately with each nostril . this is an advantage . why ? choose the answers from the following list : a. they can exhale out one nostril and inhale in the other b. they can determine what is out there c. it allows them to keep their nose moist and spongy d. they can determine the location of the smell
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you have about 20,000 genes in your dna . they encode the molecules that make up your body , from the keratin in your toenails , to the collagen at the tip of your nose , to the dopamine surging around inside your brain . other species have genes of their own . a spider has genes for spider silk . an oak tree has genes for chlorophyll , which turns sunlight into wood . so where did all those genes come from ? it depends on the gene . scientists suspect that life started on earth about 4 billion years ago . the early life forms were primitive microbes with a basic set of genes for the basic tasks required to stay alive . they passed down those basic genes to their offspring through billions of generations . some of them still do the same jobs in our cells today , like copying dna . but none of those microbes had genes for spider silk or dopamine . there are a lot more genes on earth today than there were back then . it turns out that a lot of those extra genes were born from mistakes . each time a cell divides , it makes new copies of its dna . sometimes it accidentally copies the same stretch of dna twice . in the process , it may make an extra copy of one of its genes . at first , the extra gene works the same as the original one . but over the generations , it may pick up new mutations . those mutations may change how the new gene works , and that new gene may duplicate again . a surprising number of our mutated genes emerged more recently ; many in just the past few million years . the youngest evolved after our own species broke off from our cousins , the apes . while it may take over a million years for a single gene to give rise to a whole family of genes , scientists are finding that once the new genes evolve , they can quickly take on essential functions . for example , we have hundreds of genes for the proteins in our noses that grab odor molecules . the mutations let them grab different molecules , giving us the power to perceive trillions of different smells . sometimes mutations have a bigger effect on new copies of genes . they may cause a gene to make its protein in a different organ , or at a different time of life , or the protein may start doing a different job altogether . in snakes , for example , there 's a gene that makes a protein for killing bacteria . long ago , the gene duplicated and the new copy mutated . that mutation changed the signal in the gene about where it should make its protein . instead of becoming active in the snake 's pacreas , it started making this bacteria-killing protein in the snake 's mouth . so when the snake bit its prey , this enzyme got into the animal 's wound . and when this protein proved to have a harmful effect , and helped the snake catch more prey , it became favored . so now what was a gene in the pancreas makes a venom in the mouth that kills the snake 's prey . and there are even more incredible ways to make a new gene . the dna of animals and plants and other species contain huge stretches without any protein coding genes . as far as scientists can tell , its mostly random sequences of genetic gibberish that serve no function . these stretches of dna sometimes mutate , just like genes do . sometimes those mutations turn the dna into a place where a cell can start reading it . suddenly the cell is making a new protein . at first , the protein may be useless , or even harmful , but more mutations can change the shape of the protein . the protein may start doing something useful , something that makes an organism healthier , stronger , better able to reproduce . scientists have found these new genes at work in many parts of animal bodies . so our 20,000 genes have many origins , from the origin of life , to new genes still coming into existence from scratch . as long as life is here on earth , it will be making new genes .
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at first , the protein may be useless , or even harmful , but more mutations can change the shape of the protein . the protein may start doing something useful , something that makes an organism healthier , stronger , better able to reproduce . scientists have found these new genes at work in many parts of animal bodies .
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how may we have evolved to be able to smell more odors ? choose the best description .
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translator : andrea mcdonough reviewer : bedirhan cinar in physics , the concepts of work and power help us understand and explain lots of things in our universe . let 's start with work . positive work is the energy we put into a system , and negative work is energy that is transferred out . think of positive work as money being added to your bank account , and negative work as money taken out . in the metric system , work and energy are measured in joules . as an example , let 's take a beautiful , old , mechanical grandfather clock . we transfer energy into the clock when we turn the crank to raise the heavy metal cylinders inside the clock . when we do this , we are doing positive work , adding energy to the clock , and that energy is stored as gravitational potential energy . we can calculate the amount of work done by multiplying the force we apply times the distance over which we apply the force . to raise the metal cylinders , we need to apply a force equal to their weight . that is , equal to the force of gravity pulling downward on the cylinders . these cylinders weight 300 newtons , which is pretty heavy , about as much as a small child , and if we lift them 1/2 meter , then we do 300 newtons times 1/2 meter or 150 joules of work . power is the rate at which energy is transferred . when we say rate , we mean the amount of energy transferred per unit of time . in the metric system , power is measured in joules per second , or watts . the term watt goes back to james watt , who came up with the concept of horsepower to measure the amount of power produced by a typical work horse . james watt was a producer of industrial steam engines , and he wanted his potential customers to be able to make comparisons between his steam engines and a familiar quanity , the power they could get from a working horse . it was such a useful idea that the metric system unit for power , the watt , is named after james watt . following in james watt 's footsteps , let 's compare the amount of power it takes to run this grandfather clock to the power we 'd need to run a bright , 100-watt light bulb . we can measure the power a person uses to wind the clock by dividing the amount of work they did by the time it took them to do it . if it takes 1 minute , or 60 seconds , to lift the weights , then they are doing 150 joules divided by 60 seconds , or 2.5 joules per second of work . they are adding energy to the clock in the rate of 2.5 watts . you would need about 40 times as much to run a bright , 100-watt light bulb . before we let the clock run , the energy is stored as gravitational potential energy of the cylinders . it 's like your bank account when you have just deposited money . but if we let the clock run , the cylinders slowly move downward . energy is leaving the clock . in fact , when the cylinders get to the bottom , all the energy that we put in will have left . so how much power does the clock use ? that is , how many joules of energy per second leave the clock if it takes 5 days for the cylinders to return to their original position ? we can figure this out because we already know how much work we did when we lifted the cylinders : 150 joules . but this time , it took 5 days rather than a minute . five days is 5 times 24 times 60 times 60 again or 432,000 seconds . so we divide the work done by the time and find the answer of about 0.00035 joules per second , or about 0.35 milliwatts . that 's a tiny amount of power . this clock uses so little power that you could run almost 300,000 clocks using the same power it takes to run one 100-watt light bulb . that 's right , you could run a clock in every house in a medium sized city with that much power . that 's a pretty amazing conclusion and it took knowledge of work and power to figure it out .
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when we do this , we are doing positive work , adding energy to the clock , and that energy is stored as gravitational potential energy . we can calculate the amount of work done by multiplying the force we apply times the distance over which we apply the force . to raise the metal cylinders , we need to apply a force equal to their weight .
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how can you calculate the amount of work done by a force on an object ?
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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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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 .
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the pies were each 10.5cm across and there were 400 of them . what is the biggest circle possible which could have its circumference and diameter simultaneously covered with pies ?
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translator : tom carter reviewer : bedirhan cinar you step into an elevator . it starts going down , fast . what would happen if you jumped right when it started going down ? would the ceiling hit your head ? ouch ! do you stay suspended in the air while the elevator plummets down ? let 's examine the elevator problem one step at a time . first , consider a scale . you know , the kind of scale you weigh yourself on . when you step on a scale to weigh yourself , there are two forces involved . one , gravity pulls you down . two , the scale pushes you up . what ? you did n't know a scale could push ? of course it can ! if it did n't push up on you , you would go crashing through the floor . this upward push is called the normal force and yes , it is normally there . since you 're just standing there on the scale , you 're not moving . therefore , you 're not accelerating . newton 's second law of motion -- net force equals mass times acceleration -- tells us that if the acceleration equals zero , the net force must equal zero . which means that the force of gravity pulling you down must be equal to the force of the scale pushing you up . now let 's suppose you 're standing on that scale in an elevator . at first , the elevator is standing still , so you and the scale are standing still . the two forces on you are equal and opposite . you can read how hard the scale is pushing by looking at it . we call that your weight . then , the elevator starts falling down . you and the scale are in the elevator , so you are falling down too , faster and faster . that means you are accelerating downward . now there is a net force in the same direction as the acceleration -- down . since gravity has n't changed , that must mean the scale is n't pushing up as hard . so the scale is reading a smaller number . the faster the elevator accelerates , the less the scale pushes up . what if you jumped ? would you stop falling ? would the elevator hit your head ? well , what 's pulling the elevator down ? gravity . is gravity pulling on you ? of course . so your relative position in the elevator will stay the same . the ceiling will only hit you if you can jump up to the ceiling . now consider : what would happen if the elevator accelerated upward and , even more frightening , if someone snuck in and cut the cable holding the elevator , what would happen then ? think about it .
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would you stop falling ? would the elevator hit your head ? well , what 's pulling the elevator down ? gravity .
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given what you now know about elevator physics , what do you think would happen if you were on a scale in an elevator that was ascending rapidly ?
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with social media sites being used by ⅓ of the entire world , they ’ ve clearly had an major influence on society . but what about our bodies ? here are 5 crazy ways that social media and the internet are affecting your brain right now ! can ’ t log off ? surprisingly , 5-10 % of internet users are actually unable to control how much time they spend online . though it ’ s a psychological addiction as opposed to a substance addiction , brain scans of these people actually show a similar impairment of regions that those with drug dependence have . specifically , there is a clear degradation of white matter in the regions that control emotional processing , attention and decision making . because social media provides immediate rewards with very little effort required , your brain begin to rewire itself , making you desire these stimulations . and you begin to crave more of this neurological excitement after each interaction . sounds a little like a drug , right ? we also see a shift when looking at multi-tasking . you might think that those who use social media or constantly switch between work and websites are better at multitasking , but studies have found that when comparing heavy media users to others , they perform much worse during task switching tests . increased multi-tasking online reduces your brains ability to filter out interferences , and can even make it harder for your brain to commit information to memory . like when your phone buzzes in the middle of productive work . or wait ... did it even buzz ? phantom vibration syndrome is a relatively new psychological phenomenon where you think you felt your phone go off , but it didn ’ t . in one study , 89 % of test subjects said they experienced this at least once every two weeks . it would seem that our brains now perceive an itch as an actual vibration from our phone . as crazy as it seems , technology has begun to rewire our nervous systems - and our brains are being triggered in a way they never have been before in history . social media also triggers a release of dopamine - the feel good chemical . using mri scans , scientist found that the reward centres in people ’ s brains are much more active when they are talking about their own views , as opposed to listening to others . not so surprising - we all love talking about ourselves right ? but it turns out that while 30-40 % of face-to-face conversations involve communicating our own experiences , around 80 % of social media communication is self involved . the same part of your brain related to orgasms , motivation and love are stimulated by your social media use - and even more so when you know you have an audience . our body is physiologically rewarding us for talking about ourselves online ! but it ’ s not all so self involved . in fact , studies on relationships have found that partners tend to like each other more if they meet for the first time online rather than with a face to face interaction . whether it ’ s because people are more anonymous or perhaps more clear about their future goals , there is a statistical increase in successful partnerships that started online . so while the internet has changed our verbal communication with increased physical separation , perhaps the ones that matter most end up even closer . speaking of social media , we had you ask us questions on twitter , instagram , facebook , tumblr , google+ and every other social platform we could find and did a q & amp ; amp ; a video over on asapthought ! so if you feel getting some insider info on asapscience and behind the scenes , check it out with the link in the description ! got a burning question you want answered ? ask it in the comments or on facebook and twitter . we also finally got a po box , for all of you amazing science lovers who have requested to send us mail or other stuff over the years . and we ’ d love to hear from all of you ! so feel free use the address on the screen or in the description box . and subscribe for more weekly science videos !
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with social media sites being used by ⅓ of the entire world , they ’ ve clearly had an major influence on society . but what about our bodies ?
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social media sites are used by 3/4 of the population of the entire world .
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i 'll begin today by sharing a poem written by my friend from malawi , eileen piri . eileen is only 13 years old , but when we were going through the collection of poetry that we wrote , i found her poem so interesting , so motivating . so i 'll read it to you . she entitled her poem `` i 'll marry when i want . '' ( laughter ) `` i 'll marry when i want . my mother ca n't force me to marry . my father can not force me to marry . my uncle , my aunt , my brother or sister , can not force me to marry . no one in the world can force me to marry . i 'll marry when i want . even if you beat me , even if you chase me away , even if you do anything bad to me , i 'll marry when i want . i 'll marry when i want , but not before i am well educated , and not before i am all grown up . i 'll marry when i want . '' this poem might seem odd , written by a 13-year-old girl , but where i and eileen come from , this poem , which i have just read to you , is a warrior 's cry . i am from malawi . malawi is one of the poorest countries , very poor , where gender equality is questionable . growing up in that country , i could n't make my own choices in life . i could n't even explore personal opportunities in life . i will tell you a story of two different girls , two beautiful girls . these girls grew up under the same roof . they were eating the same food . sometimes , they would share clothes , and even shoes . but their lives ended up differently , in two different paths . the other girl is my little sister . my little sister was only 11 years old when she got pregnant . it 's a hurtful thing . not only did it hurt her , even me . i was going through a hard time as well . as it is in my culture , once you reach puberty stage , you are supposed to go to initiation camps . in these initiation camps , you are taught how to sexually please a man . there is this special day , which they call `` very special day '' where a man who is hired by the community comes to the camp and sleeps with the little girls . imagine the trauma that these young girls go through every day . most girls end up pregnant . they even contract hiv and aids and other sexually transmitted diseases . for my little sister , she ended up being pregnant . today , she 's only 16 years old and she has three children . her first marriage did not survive , nor did her second marriage . on the other side , there is this girl . she 's amazing . ( laughter ) ( applause ) i call her amazing because she is . she 's very fabulous . that girl is me . ( laughter ) when i was 13 years old , i was told , you are grown up , you have now reached of age , you 're supposed to go to the initiation camp . i was like , `` what ? i 'm not going to go to the initiation camps . '' you know what the women said to me ? `` you are a stupid girl . stubborn . you do not respect the traditions of our society , of our community . '' i said no because i knew where i was going . i knew what i wanted in life . i had a lot of dreams as a young girl . i wanted to get well educated , to find a decent job in the future . i was imagining myself as a lawyer , seated on that big chair . those were the imaginations that were going through my mind every day . and i knew that one day , i would contribute something , a little something to my community . but every day after refusing , women would tell me , `` look at you , you 're all grown up . your little sister has a baby . what about you ? '' that was the music that i was hearing every day , and that is the music that girls hear every day when they do n't do something that the community needs them to do . when i compared the two stories between me and my sister , i said , `` why ca n't i do something ? why ca n't i change something that has happened for a long time in our community ? '' that was when i called other girls just like my sister , who have children , who have been in class but they have forgotten how to read and write . i said , `` come on , we can remind each other how to read and write again , how to hold the pen , how to read , to hold the book . '' it was a great time i had with them . nor did i just learn a little about them , but they were able to tell me their personal stories , what they were facing every day as young mothers . that was when i was like , 'why ca n't we take all these things that are happening to us and present them and tell our mothers , our traditional leaders , that these are the wrong things ? '' it was a scary thing to do , because these traditional leaders , they are already accustomed to the things that have been there for ages . a hard thing to change , but a good thing to try . so we tried . it was very hard , but we pushed . and i 'm here to say that in my community , it was the first community after girls pushed so hard to our traditional leader , and our leader stood up for us and said no girl has to be married before the age of 18 . ( applause ) in my community , that was the first time a community , they had to call the bylaws , the first bylaw that protected girls in our community . we did not stop there . we forged ahead . we were determined to fight for girls not just in my community , but even in other communities . when the child marriage bill was being presented in february , we were there at the parliament house . every day , when the members of parliament were entering , we were telling them , `` would you please support the bill ? '' and we do n't have much technology like here , but we have our small phones . so we said , `` why ca n't we get their numbers and text them ? '' so we did that . it was a good thing . ( applause ) so when the bill passed , we texted them back , `` thank you for supporting the bill . '' ( laughter ) and when the bill was signed by the president , making it into law , it was a plus . now , in malawi , 18 is the legal marriage age , from 15 to 18 . ( applause ) it 's a good thing to know that the bill passed , but let me tell you this : there are countries where 18 is the legal marriage age , but do n't we hear cries of women and girls every day ? every day , girls ' lives are being wasted away . this is high time for leaders to honor their commitment . in honoring this commitment , it means keeping girls ' issues at heart every time . we do n't have to be subjected as second , but they have to know that women , as we are in this room , we are not just women , we are not just girls , we are extraordinary . we can do more . and another thing for malawi , and not just malawi but other countries : the laws which are there , you know how a law is not a law until it is enforced ? the law which has just recently passed and the laws that in other countries have been there , they need to be publicized at the local level , at the community level , where girls ' issues are very striking . girls face issues , difficult issues , at the community level every day . so if these young girls know that there are laws that protect them , they will be able to stand up and defend themselves because they will know that there is a law that protects them . and another thing i would say is that girls ' voices and women 's voices are beautiful , they are there , but we can not do this alone . male advocates , they have to jump in , to step in and work together . it 's a collective work . what we need is what girls elsewhere need : good education , and above all , not to marry whilst 11 . and furthermore , i know that together , we can transform the legal , the cultural and political framework that denies girls of their rights . i am standing here today and declaring that we can end child marriage in a generation . this is the moment where a girl and a girl , and millions of girls worldwide , will be able to say , `` i will marry when i want . '' ( applause ) thank you . ( applause )
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i was going through a hard time as well . as it is in my culture , once you reach puberty stage , you are supposed to go to initiation camps . in these initiation camps , you are taught how to sexually please a man .
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what are women who reach puberty stage in malawi traditionally taught at “ orientation camps ” ?
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sunken relics , ghostly shipwrecks , and lost cities . these are n't just wonders found in fictional adventures . beneath the ocean 's surface , there are ruins where people once roamed and shipwrecks loaded with artifacts from another time . this is the domain of underwater archaeology , where researchers discover and study human artifacts that slipped into the sea . they 're not on a treasure hunt . underwater archaeology reveals important information about ancient climates and coastlines , it tells us how humans sailed the seas , and what life was like millennia ago . so what exactly can we find ? at shallow depths mingled in with modern-day items , we 've discovered all sorts of ancient artifacts . this zone contains evidence of how our ancestors fished , how they repaired their ships , disposed of their trash , and even their convicted pirates , who were buried below the tide line . and it 's not just our recent history . 800,000-year old footprints were found along the shore in norfolk , britain . in these shallow depths , the remains of sunken cities also loom up from the sea floor , deposited there by earthquakes , tsunamis , and earth 's sinking plates . almost every sunken city can be found at these shallow depths because the sea level has changed little in the several thousand years that city-building civilizations have existed . for instance , in shallow waters off the coast of italy lies baia , a roman seaside town over 2,000 years old . there , it 's possible to swim among the ruins of structures built by rome 's great families , senators , and emperors . and then there are shipwrecks . as ships grow too old for use , they 're usually abandoned near shore in out-of-the-way places like estuaries , rivers , and shallow bays . archaeologists use these like a timeline to map a harbor 's peaks and declines , and to get clues about the historic art of shipbuiding . at roskilde in denmark , for example , five purposefully sunken vessels reveal how vikings crafted their fearsome long ships 1,000 years ago . when we descend a bit further , we reach the zone where the deepest human structures lie , like ancient harbor walls and quays . we also see more shipwrecks sunk by storms , war , and collisions . we 're still excavating many of these wrecks today , like blackbeard 's ship , which is revealing secrets about life as an 18th century pirate . but past 50 feet , there are even deeper , better preserved shipwrecks , like the wreck at antikythera , which sank during the 1st century bc . when it was discovered , it contained statues , trade cargo , and also the earliest known computer , a mysterious device called the antikythera mechanism that kept track of astronomical changes and eclipses . today , it gives archaeologists vital information about the knowledge possessed by the ancient greeks . it is in this zone that we also begin to find aircraft and submarines , such as those from the world wars . plunging as deep as 200 feet , we can find some of the earliest and rarest signs of human history . prior to 5,000 years ago , there was a lot more dry land because glaciers trapped much of the water that now forms the sea . our ancestors spread across these lands , and so on the sea floor , we find their camps , stone tools , and the bones of animals they hunted . these sites give us invaluable knowledge about our ancestor 's migration patterns , hunting methods , and technologies . in the deepest zone , no human has ever walked . this area has been submerged since well before mankind evolved . the only artifacts we find are those that have drifted down from above , like nasa 's saturn v rocket engines at 14,000 feet , and the deepest shipwrecks . the ocean is like a huge underwater museum that constantly adds to our knowledge about humanity . with only a fraction of it explored , discoveries are sure to continue long into the future .
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these sites give us invaluable knowledge about our ancestor 's migration patterns , hunting methods , and technologies . in the deepest zone , no human has ever walked . this area has been submerged since well before mankind evolved .
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only ships and aircraft are the only types of sites found in the deepest ocean zone . why ?
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space : it 's where things happen . time : it 's when things happen . we can measure where things are and when things take place , but in modern physics , we realize when and where are actually part of the same question . because when it comes to understanding the universe , we need to replace three-dimensional space plus time with a single concept : four-dimensional space-time . we 'll explore and explain space-time in this series of animations . animations ? yeah . well , we 're not very animated are we ? sure we are ! look , i can go from here to here . whoa ! how 'd you get from here to there ? how fast did you go ? did you run ? walk ? did you even go in a straight line ? ah ! to answer that , you 'll need to make our cartoon physics look more like physics physics . you 'll need more panels . more panels , please ! okay , in each panel , andrew 's in a slightly different place . so i can see each one records where andrew is at a different time . that 's great . but it would be easier to see what 's going on if we could cut out all the hundreds of panels and stack them up like a flip book . right , now let 's flip through the book so that we can see one panel after another getting through 24 in every second . see ! i told you it was an animation . now you can see me walking along . drawing all those panels and putting them into a flip book is just one way of recording the way i 'm moving . it 's how animation , or even movies , work . as it turns out , at my walking speed , it takes two seconds to get past each fence post , and they 're spaced four meters apart . so we can calculate my velocity -- how fast i 'm moving through space - - is two meters per second . but i could 've worked that out from the panels without flipping through them . from the edge of the flip book , you can see all of the copies of the fence posts and all of the copies of andrew and he 's in a slightly different place in each one . now we can predict everything that will happen to andrew when we flip through 24 pages every second , including his speed of motion , just by looking . no need to flip through at all . the edge of this flip book is known as a space-time diagram of andrew 's journey through , you guessed it , space and time . we call the line that represents andrew 's journey his world line . if i jog instead of walking , i might be able to get past a fence post every second . he 's not very athletic . anyway , when we look at this new flip book from the edge , we can do the same analysis as before . the world line for andrew jogging is more tilted over than the world line for andrew walking . we can tell he 's going twice as fast as before without flipping the panels . but here 's the clever bit . in physics , it 's always good to view things from other perspectives . after all , the laws of physics should be the same for everyone or no one will obey them . so let 's rethink our cartoon and have the camera follow andrew jogging along as the fence posts approach and pass behind him . still viewing it as a flip book of panels , we do n't need to redraw anything . we simply move all of the cutout frames slightly until andrew 's tilted world line becomes completely vertical . to see why , let 's flip it . yes , now i 'm stationery , just jogging on the spot , in the center of the panel . on the edge of the flip book , my world line was going straight upwards . the fence posts are coming past me . it 's now their world lines that are tilted . this rearrangement of the panels is known as a galilean transformation , and it lets us analyze physics from someeone else 's perspective . in this case , mine . after all , it 's always good to see things from other points of view , especially when the viewers are moving at different speeds . so long as the speeds are n't too high . if you 're a cosmic ray moving at the speed of light , our flip book of your point of view falls apart . to stop that from happening , we 'll have to glue panels together . instead of a stack of separate panels , we 'll need a solid block of space-time , which we 'll come to in the next animation .
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in this case , mine . after all , it 's always good to see things from other points of view , especially when the viewers are moving at different speeds . so long as the speeds are n't too high .
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it is useful to do this and examine how the world looks to objects moving at different steady speeds because :
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so molybdenum is an element which is essential to life and most organisms beginning with you and me and going down to bacteria have enzymes that contain molybdenum . one of the most important enzymes is so called nitrogenase which is an enzyme that will turn nitrogen into ammonia , and nitrogenase is found in various bacteria that live in the roots of plants like beans . so the beans , via these bacteria , can absorb nitrogen into the atmosphere and turn it into a form that we can digest and we need that nitrogen so that we can make the proteins in our body . so without molybdenum nothing could live .
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so molybdenum is an element which is essential to life and most organisms beginning with you and me and going down to bacteria have enzymes that contain molybdenum . one of the most important enzymes is so called nitrogenase which is an enzyme that will turn nitrogen into ammonia , and nitrogenase is found in various bacteria that live in the roots of plants like beans . so the beans , via these bacteria , can absorb nitrogen into the atmosphere and turn it into a form that we can digest and we need that nitrogen so that we can make the proteins in our body .
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what is the most important enzyme that contains molybdenum , found in various bacteria that are associated with bean plants ?
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james joyce 's `` ulysses '' is widely considered to be both a literary masterpiece and one of the hardest works of literature to read . it inspires such devotion that once a year on a day called bloomsday , thousands of people all over the world dress up like the characters , take to the streets , and read the book aloud . and some even make a pilgrimage to dublin just to visit the places so vividly depicted in joyce 's opus . so what is it about this famously difficult novel that inspires so many people ? there 's no one simple answer to that question , but there are a few remarkable things about the book that keep people coming back . the plot , which transpires over the course of a single day , is a story of three characters : stephen dedalus , reprised from joyce 's earlier novel , `` a portrait of the artist as a young man '' ; leopold bloom , a half-jewish advertising canvasser for a dublin newspaper ; and bloom 's wife molly , who is about to embark on an affair . stephen is depressed because of his mother 's recent death . meanwhile , bloom wanders throughout the city . he goes to a funeral , his work , a pub , and so on , avoiding going home because molly is about to begin her affair . where it really starts to get interesting , though , is how the story 's told . each chapter is written in a different style . 15 is a play , 13 is like a cheesy romance novel , 12 is a story with bizarre , exaggerated interruptions , 11 uses techniques , like onomatopoeia , repetitions , and alliteration to imitate music , and 14 reproduces the evolution of english literary prose style , from its beginnings in anglo-saxon right up to the 20th century . that all culminates in the final chapter which follows molly 's stream of consciousness as it spools out in just eight long paragraphs with almost no punctuation . the range of styles joyce uses in `` ulysses '' is one of the things that makes it so difficult , but it also helps make it enjoyable . and it 's one of the reasons that the book has held up as one of the key texts of literary modernism , a movement characterized by overturning traditional modes of writing . joyce fills his narrative gymnastic routines with some of the most imaginative use of language you 'll find anywhere . take , for instance , `` the figure seated on a large boulder at the foot of a round tower was that of a broadshouldered deepchested stronglimbed frankeyed redhaired freelyfreckled shaggybearded widemouthed largenosed longheaded deepvoiced barekneed brawnyhanded hairlegged ruddyfaced sinewyarmed hero . '' here , joyce exaggerates the description of a mangy old man in a pub to make him seem like an improbably gigantesque hero . it 's true that some sections are impenetrably dense at first glance , but it 's up to the reader to let their eyes skim over them or break out a shovel and dig in . and once you start excavating the text , you 'll find the book to be an encyclopedic treasure trove . it 's filled with all manner of references and allusions from medieval philosophy to the symbolism of tattoos , and from dante to dublin slang . as suggested by the title , some of these allusions revolve around homer 's `` odyssey . '' each chapter is named after a character or episode from the `` odyssey , '' but the literary references are often coy , debatable , sarcastic , or disguised . for example , homer 's odysseus , after an epic 20-year-long journey , returns home to ithaca and reunites with his faithful wife . in contrast , joyce 's bloom wanders around dublin for a day and returns home to his unfaithful wife . it 's a very funny book . it has highbrow intellectual humor , if you have the patience to track down joyce 's references , and more lowbrow dirty jokes . those , and other sexual references , were too much for some . in the u.s. , the book was put on trial , banned , and censored before it had even been completed because it was originally published as a serial novel . readers of `` ulysses '' are n't just led through a variety of literary styles . they 're also given a rich and shockingly accurate tour of a specific place at a time : dublin in 1904 . joyce claimed that if dublin were to be destroyed , it could be recreated from the pages of this book . while such a claim is not exactly true , it does show the great care that joyce took in precisely representing details , both large and small , of his home city . no small feat considering he wrote the entire novel while living outside of his native ireland . it 's a testament to joyce 's genius that `` ulysses '' is a difficult book . some people find it impenetrable without a full book of annotations to help them understand what joyce is even talking about . but there 's a lot of joy to be found in reading it , more than just unpacking allusions and solving puzzles . and if it 's difficult , or frustrating , or funny , that 's because life is all that , and more . responding to some criticism of `` ulysses , '' and there was a lot when it was first published , joyce said that if `` ulysses '' is n't worth reading , then life is n't worth living .
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no small feat considering he wrote the entire novel while living outside of his native ireland . it 's a testament to joyce 's genius that `` ulysses '' is a difficult book . some people find it impenetrable without a full book of annotations to help them understand what joyce is even talking about . but there 's a lot of joy to be found in reading it , more than just unpacking allusions and solving puzzles .
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how could `` ulysses '' have been censored before joyce had even finished writing it ?
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if you 're ever walking down the street and come across an oddly stretched out image , like this , you 'll have an opportunity to see something remarkable , but only if you stand in exactly the right spot . that happens because these works employ a technique called anamorphosis . anamorphosis is a special case of perspective art , where artists represent realistic three-dimensional views on two-dimensional surfaces . though it 's common today , this kind of perspective drawing has only been around since the italian renaissance . ancient art often showed all figures on the same plane , varying in size by symbolic importance . classical greek and roman artists realized they could make objects seem further by drawing them smaller , but many early attempts at perspective were inconsistent or incorrect . in 15th century florence , artists realized the illusion of perspective could be achieved with higher degrees of sophistication by applying mathematical principles . in 1485 , leonardo da vinci manipulated the mathematics to create the first known anamorphic drawing . a number of other artists later picked up the technique , including hans holbein in `` the ambassadors . '' this painting features a distorted shape that forms into a skull as the viewer approaches from the side . in order to understand how artists achieve that effect , we first have to understand how perspective drawings work in general . imagine looking out a window . light bounces off objects and into your eye , intersecting the window along the way . now , imagine you could paint the image you see directly onto the window while standing still and keeping only one eye open . the result would be nearly indistinguishable from the actual view with your brain adding depth to the 2-d picture , but only from that one spot . standing even just a bit off to the side would make the drawing lose its 3-d effect . artists understand that a perspective drawing is just a projection onto a 2-d plane . this allows them to use math to come up with basic rules of perspective that allow them to draw without a window . one is that parallel lines , like these , can only be drawn as parallel if they 're parallel to the plane of the canvas . otherwise , they need to be drawn converging to a common point known as the vanishing point . so that 's a standard perspective drawing . with an anamorphic drawing , like `` the ambassadors , '' directly facing the canvas makes the image look stretched and distorted , but put your eye in exactly the right spot way off to the side , and the skull materializes . going back to the window analogy , it 's as if the artist painted onto a window positioned at an angle instead of straight on , though that 's not how renaissance artists actually created anamorphic drawings . typically , they draw a normal image onto one surface , then use a light , a grid , or even strings to project it onto a canvas at an angle . now let 's say you want to make an anamorphic sidewalk drawing . in this case , you want to create the illusion that a 3-d image has been added seamlessly into an existing scene . you can first put a window in front of the sidewalk and draw what you want to add onto the window . it should be in the same perspective as the rest of the scene , which might require the use of those basic rules of perspective . once the drawing 's complete , you can use a projector placed where your eye was to project your drawing down onto the sidewalk , then chalk over it . the sidewalk drawing and the drawing on the window will be nearly indistinguishable from that point of view , so viewers ' brains will again be tricked into believing that the drawing on the ground is three-dimensional . and you do n't have to project onto a flat surface to create this illusion . you can project onto multiple surfaces , or assemble a jumble of objects , that from the right point of view , appears to be something else entirely . all over the planet , you can find solid surfaces giving way to strange , wonderful , or terrifying visions . from your sidewalk to your computer screen , these are just some of the ways that math and perspective can open up whole new worlds .
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ancient art often showed all figures on the same plane , varying in size by symbolic importance . classical greek and roman artists realized they could make objects seem further by drawing them smaller , but many early attempts at perspective were inconsistent or incorrect . in 15th century florence , artists realized the illusion of perspective could be achieved with higher degrees of sophistication by applying mathematical principles . in 1485 , leonardo da vinci manipulated the mathematics to create the first known anamorphic drawing . a number of other artists later picked up the technique , including hans holbein in `` the ambassadors . ''
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how do artists physically create anamorphisms ?
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most of us think of the sun as our friend . it helps plants grow , keeps us warm , and who does n't love to lie on the beach on a sunny day ? but for all of it 's good qualities , the sun can also be harmful in large amounts . that 's why we invented sunscreen . the purpose of sunscreen is to shield the body from the sun 's ultraviolet rays , which have several harmful effects , including sunburn , aging , and skin cancer promotion . these rays are separated by their different wave lengths , into types such as uva and uvb , which exert a variety of effects in the skin due to the absorption patterns of chromophores , the parts of the molecules responsible for their color . the primary two chromophores are hemoglobin , found in our red blood cells , and melanin , which gives our skin its pigment . we know that uvb rays cause the skin to burn . the role of uva rays is less well understood and appears to have an effect on our tanning response , carcinogenesis , and aging . so , how does the sunscreen protect us from these rays ? there are two basic types of sunscreen , physical and chemical blockers . physical blockers , like zinc oxide or titanium dioxide , reflect the sun 's rays by acting as a physical barrier . if you 've seen lifeguards with noses covered in white , then you know what this looks like . the same ingredients are primary components of diaper creams , where the goal is also to create a physical barrier . historically , they have n't always been easy to apply and were conspicuously visible on the skin , but new formulations have made this less of an issue . chemical blockers , on the other hand , absorb the sun 's rays . they deteriorate more quickly than physical sunscreens because their ability to absorb the sun diminishes . generally , these are more transparent when rubbed on the skin , but some people develop allergric reactions to some of the chemicals . regardless of the type of sunscreen , all are subjected to testing to determine their sunburn protection factor , or spf . this is essentially a measure of the protection that the sunscreen will provide from uvb rays before one begins to burn . but even if you do n't burn , you still need to use sunscreen because unless you live in a cave , you 're not immune to the effects of the sun . it is true that darker skinned people and those who tan easily have more built-in protection from sunburns , but they are still vulnerable to the effects of uva . children under the age of six months , on the other hand , should have almost no sun exposure as their protective mechanisms are not fully functioning , and their skin is more likely to absorb any sunscreen that is applied . wearing sunscreen helps protect against the development of all three types of skin cancer : basal cell carcinoma , squamous cell carcinoma , and melanoma . on a daily basis , the dna in your cells is developing mutations and errors that are generally handled by machinery within your cells , but ultraviolet rays from the sun lead to mutations that the cell may not be able to overcome , leading to uncontrolled growth and eventual skin cancer . the scariest thing about this is that usually you ca n't even see it happening until its too late . but if these concrete risks to your health are not enough to convince you to use sunscreen , there are aesthetic reasons as well . along with cigarette smoking , sun damage is the leading cause of premature aging . photoaging from chronic sun exposure leads to a loss of elasticity in the skin , in other words , making it look saggy . take a look at this truck driver who 's left side was chronically exposed to the sun and notice the difference . this is an important point . car windows block uvb , the burn rays , but not uva , the aging rays . it is recommended to use sunscreen daily , but you should pay special attention before prolonged sun exposure or when at the beach or among snow since the reflectivity of water and ice amplifies the sun 's rays . for these cases , apply about an ounce fifteen to thirty minutes before you go out and once again soon after you get outside . after that , you should reapply it every two to three hours , especially after swimming or sweating . otherwise you should wear protective clothing with ultraviolet protection factor , or upf . stay in shaded areas , such as under trees or an umbrella , and avoid the sun at the peak hours of 10 a.m. to 4 p.m. and what 's the best kind of sunscreen ? everyone will have their preference , but look for the following things : broad spectra , spf of at least 30 , and water-resistant . a light moisturizer with spf 30 should be good for daily use . take note if you decide to use a spray . they take several coats to effectively cover your skin , like painting a wall with a spray can versus a paint brush . so , enjoy the sun , but enjoy it with sunscreen .
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most of us think of the sun as our friend . it helps plants grow , keeps us warm , and who does n't love to lie on the beach on a sunny day ?
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people with darker skin produce more pigment that offers them additional protection against the sun . this appears to have a relationship to geography and evolution . why do you think this might be ?
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translator : andrea mcdonough reviewer : bedirhan cinar let 's talk about the facts of life . you remember that conversation you had when you were a kid about sex or drugs with your parents or some trusted adult ? probably not because it 's a myth . you do n't talk to kids about that stuff . it 's just so embarrassing . and , hey , maybe that 's ok. we 've been outsourcing the facts of life for decades . we spend billions of dollars on it . so , why talk to kids when you can just turn on the tv ? i learned about drugs from an egg and a frying pan : `` this is drugs , and this is your brain on drugs . pssssssss . any questions ? '' yeah , actually , i did . but it 's not about questions . it 's about data . in the 1980 's when i was growing up , those data were terrifying parents : 1 % of high school seniors had try heroin , 12 % hallucinogens , 12 % tranquilizers , 17 % cocaine , 26 % stimulants , and over 50 % of us had tried marijuana . it was an epidemic ! at least , that 's what they told us . and marijuana was the gateway drug , leading to all the harder stuff . of course , 92 % of us were drinking alcohol , and that was killing more of us than all drugs combined . but , nevermind , it 's legal . so we declared war on drugs ! nancy reagan was our general . all drugs will kill you , so just say , `` no ! '' just say , `` no ! '' to pot . just say , `` no ! '' to cocaine . just say , `` no ! '' to everything . so simple ! if you want to save kids , you have to scare the hell out of them ! and we spent ridiculous amounts of money doing that . soon that war on drugs spread to become a war on sex . we were pushing abstinence on kids to fight aids . and when all the data finally came home , guess what : completely ineffective . we love big solutions to big problems , do n't we ? what if the facts of life do n't work that way ? what if the experience of having that conversation ca n't be mass-produced ? what if it ca n't be scaled up ? well , that would be very frustrating for everyone in this industry , would n't it ? and , many of them are really trying to help . who , then ? us . we have to talk to kids . openly and honestly . but are we ready to be honest ? i do n't think so . we mythologize childhood . mine was in stone mountain , georgia , a completely typical 1980 's american suburb . for the parents , a wholesome paradise of bridge parties and tennis games . for us kids , we were all working on a secret research project , and our laboratory was in the woods after school , under the covers during sleep-overs , really , any opportunity we could take to peel off our clothes and investigate . what were these things , bodies ? what do they do ? we had to figure them out and that 's childhood . it 's not just fun and games , it 's actually a manhattan project of nakedness . and then you walk into your first class in middle school , and the bomb goes off . you are not just a body any more . oh no , now you are grotesque . that 's when the suffering really starts . so , yeah , talk to kids . but if you are not honest about your own experiences first , everything you say smells like bullshit . do n't worry , you can practice and you should start by talking to the one kid you definitely know : you . what kind of kid were you ? what troubled you ? for me , it was age 13 . that was the worst year . i was obsessively curious about sex and also deeply ashamed by it . it was n't my only problem , of course , not by a long shot , but it was the beginning of a downward spiral . and my bad luck was to hit bottom while watching `` the wall '' by pink floyd , which is a bad idea for a miserable 13-year old high on weed . so , that night , for whatever reason , it seemed like good idea to shave off my eyebrows , and then try to kill myself by swallowing all the pills in the bathroom , which was not at all fatal , but everyone noticed the eyebrows . and that made middle school extra fun . so , what was your low point ? and if you could build a time machine to travel back and talk to that kid , what would you say to yourself ? for me , it was easy . all i really needed was someone to reassure me that somehow i was a normal part of the universe . but i did n't feel like i could talk to anyone . and yet weirdly , i fully expected a time traveler to materialize at any time because i was a geek . i did n't know if it would be my unborn son or a t-101 cyborg . but either one would be awesome ! hey , it 's me , yourself from the future , in the year 2012 . i have crucial information for you , but not about the future , about the past , a billion years in the past , when this planet was covered with nothing but cells and all they did was fight , eat , and divide ; fight , eat , and divide . except for one . and that 's your ancestor . this cell enslaved other ones , but master and slave became one . and then those cells invented sex , and then they invented the first bodies with each cell doing a different job , some smelling , some moving , some eating . and the job of sex went to a special cell called the gamete . and those bodies became giant . the distance to the next body was vast so they had to swim . most would be lost and die so they were mass-produced . soon the oceans were a non-stop riot of sex and death until 500 million years ago , when the first beast crawled onto land . land is hard because bodies are heavy . and the sun kills gametes . to keep them safe , so deep inside of a body , the mother builds a tiny ocean . outside are events of unimaginable violence . whole new forms of life are being created only to be wiped away . millions of years are flashing by . but in here , it 's always the same . peace . just peace . maybe we will never know why , but of all the possible bodies that have appeared on this planet , it was this one , bilaterally symmetric , warm-blooded , bigger than a mouse , smaller than a horse , 2 legs , 10 toes , no tail , big brain , language , technology , and civilization rising and falling for thousands of years . and here you are , a 13-year old human perplexed and embarrassed about sex . that 's what i came here to tell you : we do n't know why sex evolved nor why it persists . why do n't we just clone ourselves like all life did a billion years ago ? it 's so much more efficient . we would all have babies , no mates . it could be that children who are genetically different from each other are protected from disease . and that is still our best guess . so be comforted to know that even in the distant future , in the year 2012 , we still do n't know what sex is for . it is perplexing . you should n't be embarrassed by it . sex is a beautiful puzzle . and without it , you simply would not be here . by the way , be nice to your little sister . she 's your best friend . you 'll see .
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we mythologize childhood . mine was in stone mountain , georgia , a completely typical 1980 's american suburb . for the parents , a wholesome paradise of bridge parties and tennis games .
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what substance was most commonly used amongst teenagers in the 1980 's ?
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this is tungsten , i think . tungsten is a very hard and heavy element . it has a number of very important uses . it is used in the filament of light bulbs , the ordinary sort of light bulbs because it has more or less the highest boiling point of any element and therefore you can use it as the filament and it can get very hot without very much evaporation on to the walls . if you add iodine in the gas around the bulb you can run it at even higher temperatures , the so called quartz halogen lamps and sometimes you see these in up-market cars . yes , it ’ s tungsten . so this is tungsten . tungsten is used as an element material to form the very , very fine wire that we may have used in old-style electric light bulbs . it is a really quite wonderful metal and it is actually used in nature . but here we have a really quite beautiful sample . this is a single crystal of tungsten which is mounted . tungsten carbide , the compound of tungsten and carbon is used in the very tip , the balls in the tip of a biro pen or ball point pen . really quite amazing . i have got some other tungsten here somewhere and in fact here is a very fine wire of tungsten and this is precisely the material which was used in the formation of very early electric light bulbs . a really quite amazing metal . there is also quite a nice book by oliver sacks , who is an englishman who now lives in america , called uncle tungsten . there are not many books that have chemical names in the title and this is a story of his childhood and how chemistry really had a big effect on him . that ’ s lovely .
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a really quite amazing metal . there is also quite a nice book by oliver sacks , who is an englishman who now lives in america , called uncle tungsten . there are not many books that have chemical names in the title and this is a story of his childhood and how chemistry really had a big effect on him . that ’ s lovely .
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what is the title of the book that the professor showed in the video ?
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as we walk through our daily environments , we 're surrounded by exotic creatures that are too small to see with the naked eye . we usually imagine these microscopic organisms , or microbes , as asocial cells that float around by themselves . but in reality , microbes gather by the millions to form vast communities known as biofilms . natural biofilms are like miniature jungles filled with many kinds of microbes from across the web of life . bacteria and archaea mingle with other microbes like algae , fungi , and protozoa , forming dense , organized structures that grow on almost any surface . when you pad across a river bottom , touch the rind of an aged cheese , tend your garden soil , or brush your teeth , you 're coming into contact with these invisible ecosystems . to see how biofilms come about , let 's watch one as it develops on a submerged river rock . this type of biofilm might begin with a few bacteria swimming through their liquid environment . the cells use rotating flagella to propel towards the surface of the rock , which they attach to with the help of sticky appendages . then , they start producing an extracellular matrix that holds them together as they divide and reproduce . before long , microcolonies arise , clusters of cells sheathed in this slimy , glue-like material . microcolonies grow to become towers , while water channels flow around them , functioning like a basic circulatory system . but why do microbes build such complex communities when they could live alone ? for one thing , microbes living in a biofilm are rooted in a relatively stable microenvironment where they may have access to a nutrient source . there 's also safety in numbers . out in the deep , dark wilderness of the microbial world , isolated microbes face serious risks . predators want to eat them , immune systems seek to destroy them , and there are physical dangers , too , like running out of water and drying up . however , in a biofilm , the extracellular matrix shields microbes from external threats . biofilms also enable interactions between individual cells . when microbes are packed against each other in close proximity , they can communicate , exchange genetic information , and engage in cooperative and competitive social behaviors . take the soil in your garden , home to thousands of bacterial species . as one species colonizes a plant root , its individual cells might differentiate into various subpopulations , each carrying out a specific task . matrix producers pump out the extracellular goo , swimmers assemble flagella and are free to move about or migrate , and spore-formers produce dormant , tough endospores that survive starvation , temperature extremes , and harmful radiation . this phenomenon is called division of labor . ultimately , it gives rise to a sophisticated system of cooperation that 's somewhat like a multicellular organism in itself . but because biofilms often contain many different microbes that are n't closely related to each other , interactions can also be competitive . bacteria launch vicious attacks on their competitors by secreting chemicals into the environment , or by deploying molecular spears to inject nearby cells with toxins that literally blow them up . in the end , competition is all about resources . if one species eliminates another , it keeps more space and food for itself . although this dramatic life cycle occurs beyond the limits of our vision , microbial communities provide humans and other species with tangible , and sometimes even delicious , benefits . microbes make up a major fraction of the biomass on earth and play a critical role within the global ecosystem that supports all larger organisms , including us . they produce much of the oxygen we breath , and are recruited to clean up environmental pollution , like oil spills , or to treat our waste water . not to mention , biofilms are normal and flavor enhancing parts of many of the foods we enjoy , including cheese , salami , and kombucha . so the next time you brush your teeth , bite into that cheese rind , sift through garden soil , or skip a river stone , look as close as you can . imagine the microbial jungles all around you waiting to be discovered and explored .
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microcolonies grow to become towers , while water channels flow around them , functioning like a basic circulatory system . but why do microbes build such complex communities when they could live alone ? for one thing , microbes living in a biofilm are rooted in a relatively stable microenvironment where they may have access to a nutrient source .
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in natural environments , most microbes live :
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hey , vsauce . michael here . when you call customer service and hear this `` to ensure quality service your call may be monitored or recorded '' , they 're not kidding . over the last year the marchex institute analysed more than 600,000 recorded phone conversations americans made to businesses in the united states . turns out , people from ohio were the most likely to use curse words - the 'a ' word , the 'f ' word and the 's ' word . washington state residents were the least likely to use bad words . but what makes a word bad ? oh , be careful because etymologically speaking even the word 'bad ' can be considered a bad word . it began in old english as a derogatory term for an effeminate man . eighty percent of swear words overheard in public in 1986 , 1997 and 2006 were essentially the same . one third of all counts included the top two - the 'f ' word and the 's ' word . slate 's brilliant lexicon valley podcast purported that these 10 words makeup about 0.7 % of the average english speakers daily vocabulary , which means socially unacceptable words are used almost as often as socially descriptive words . first person plural pronouns account for about 1 % of the words we say everyday . when a bad word is bleeped , it is covered with a 1 kilohertz sine wave , which sounds like this . son of a ... by the way , the symbols and squiggles that are used to represent a bad word have a name . they 're called grawlixes . they were named by mort walker in his seminal `` the lexicon of comicana . '' he names a lot of things but most of them show stuff , they do n't hide stuff . why the need to hide bad words , especially if we all pretty much know what 's being said ? well , there is no one single reason bad words are bad . steven pinker in his excellent lecture on the topic delineates five types of swearing . first of all , some words are bad on purpose . they are created and/or used with the intent to hurt others . he calls this `` abusive swearing . '' using words to insult , humiliate , objectify or marginalise disfavoured people . now , if that this disfavoured person is god , we 're talking about supernatural swearing , which was particularly taboo in victorian times . it was believed that casually or vainly referring to god would physically injure god himself , literally . so , at the time people were forced to come up with euphemisms , like `` zounds ! '' and `` gadzooks ! `` , which originally meant `` god 's wounds ! '' and `` god 's hooks ! `` , referring to the nails driven through the hands of jesus . historically , swear words often came from things we were afraid of , things we perceived as dangerous , stronger than us and mercurial . such as death , disease and infirmity , sex and sexually transmitted diseases , as well as body fluids , germy , gross effluvia . words for those gross things became gross and bad in and of themselves , uncouth to speak . but not all words for gross things are socially unacceptable , which brings us to pinker 's second type of swearing - emphatic swearing . emphatic swearing is where the taboo-ness of bad words becomes quite practical . you would n't usually use those words but when you really want to convey that your current emotions matter more to you than proper social conduct , you can use them . dysphemism . a euphemism is kind , acceptable word that allows you to talk about something unpleasant while simultaneously letting everyone know you totally get that it 's unpleasant and want to respect that . for instance , if you want to be professional , you would n't say s*** . you might say 'defecate ' . if , on the other hand , you really want to drive home just how unpleasant the experience was , dysphemisms can help out a lot . it was n't a bag of canine defecation you found on your front porch , it was a s*** bag of hot dog s*** . both of these words refer to pretty much the same thing but they have different levels of social acceptability and that 's very helpful . it means word choice allows us to not only refer to things in the real world but also to how we feel about them . if both these words had the same level of social acceptance we might even have to find new , badder words so as not to lose the power language currently has to express emotion , repulsion and disgust . but when it comes to two words referring to the same thing , but with different levels of social acceptance , who decides which one 's good and which one 's bad ? well , historically , many of the bad words we use today are the result of class differences . in medieval england , the lower-class saxons spoke a germanic tongue while the upper-class normans spoke a language related to french and latin . english , as we know it today , contains many consequences of their differences . the lower class worked with animals and from them we get animal names . the upper class only ate the animals , which is where the names of the meat come from . today 's swear words are similar . defecation stems from fancy pants latin , whereas the less classy s*** is germanic . there 's also idiomatic swearing , where nothing is being emphasized . no dysphemism is meant ; instead , it 's an easygoing type of swearing that shows an atmosphere is casual . bad words can be used , we 're all close here . it 's okay to swear , we 're all cool . cathartic swearing is a bit different . it gives us `` lalochezia , '' the medical term for the relief swearing provides when you 're in pain . in the brain , swearing seems to involve different regions than regular language , which may explain why people with aphasia caused by brain damage struggle to comprehend or construct spoken words but yet are fluent at swearing . or why people with coprolalia control normal language just fine , but involuntarily utter profanity , an obscene words . it turns out swearing may be centralized in the limbic system , along with the motions . many animals make automatic noises when in pain or threat to startle or intimidate attackers , or to let others know what 's going on . in humans , bad words are great for this purpose . their taboo-ness makes them special . people would n't use them otherwise , so they are great alarms . swearing is changing . some bad words are being used more and more frequently . of the seven words , george carlin said you could never say on television . today , every second 22 of them are sent out on twitter . so , what will swearing look like in the future ? it probably wo n't go away altogether , it 's too useful . but the words we do n't like will likely change . history has shown that as disease becomes less scary and sex and the supernatural more personal , words related to them become less taboo and more common ; whereas words that were common in the past are increasingly unpleasant . perhaps , in the future , spurt not by runaway political correctness but by wider knowledge , words like `` schizo '' , `` mental '' , `` aspy '' , or even `` depressed '' will take the square stage . or as john mcwhorter ventured , words centered around class and the gap between opportunity and disadvantage will become more taboo . salt of the earth , trash , chav , pikey , urban as a pejorative . when mckay hatch started a `` no cussing club '' at his school , his campaign became the target of so many online jokes and insults for being lame or anti-free speech . on his book , he literally subtitled his own name `` the most cyberbullied kid in the world . '' people care about this stuff . is it censorship to tell us what we can and can not say or is it a safety seal , ensuring certain dysphemisms do n't get worn down to a quotidian bluntness like every other word ? or is that badness of bad words a boundary , a moving boundary of we reject - sometimes arbitrary , sometimes irrational , but always moving in the direction of acceptance moving forward ? crime and inequality have existed ever since they could . but when n.w.a released a reaction , in the form of a song with bad word in the title , `` f*** the police '' , the federal bureau of investigations released a statement against the song . it was the only time , up until then and since , the fbi has ever issued an official statement about a work of art . bad words have power . if you wan na push for change you 'll need something to push . if everything 's fine , nothing 's cool . so , bad words are the precipitate of a larger reaction - the process of us slowly becoming what we want to become . that 's some deep s*** . and as always , thanks for watching .
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using words to insult , humiliate , objectify or marginalise disfavoured people . now , if that this disfavoured person is god , we 're talking about supernatural swearing , which was particularly taboo in victorian times . it was believed that casually or vainly referring to god would physically injure god himself , literally .
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what was the most taboo type of swearing during the victorian era ?
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a boy named prince tamino runs through a dark wood pursued by a dragon . just as it rears up to devour him , three mysterious ladies appear and slay the dragon with their fierce battle cry . so begins wolfgang amadeus mozart 's `` die zauberflöte , '' or `` the magic flute . '' this fantasy singspiel , a type of folk opera with music and dialogue , premiered in 1791 in vienna . though it may seem like a childish fairytale , this intricate opera is full of subversive symbolism , and it 's now regarded as one of the most influential operas in history . tamino 's run in with the dragon is only the start of his journey . the three women summon their leader , the queen of the night . she , in turn , sends tamino on a quest to rescue her daughter pamina from the evil sorcerer , sarastro . and to help him on his journey , she gives him the titular magic flute . tamino eventually finds pamina at sarastro 's temple , but behind enemy lines , tamino and pamina learn that they 're on the wrong side . the queen of night actually wants to plunge the world into darkness . everything tamino thought he knew was wrong , filling him with doubt and confusion . so , a new quest begins for tamino and pamina . they must pass three trials of wisdom , and only then can the day vanquish the night . helped by the flute 's magic power , the two youths overcome these trials and the queen 's attempts to sabotage them . they 're finally initiated into the temple having restored balance to the kingdom . many elements in this peculiar fairytale were inspired by mozart 's involvement in freemasonry , a network of fraternal organizations throughout europe . much of their history , symbolism , and ritual came from the middle ages . but the freemasons of mozart 's time were also influenced by 18th century european ideals - rationalism , humanism , and skepticism towards traditional authorities , like monarchy and the church . the symbols of freemasonry and these ideals of the enlightenment are found throughout the opera . if this sounds like a conspiracy theory , that 's because it sort of was at the time , but it 's now taken quite seriously and has been the subject of considerable scholarly publication . for example , some mozart scholars believe the queen of the night symbolizes maria theresa , the empress of the holy roman empire who opposed freemasonry and banned it in austria . while there continues to be debate as to the specific meaning , interpretation , and location of these masonic references , scholars agree that they 're there and are fully intentional . one of these symbols is the number three , which represented balance and order to freemasons . now the number three is , of course , easy to find in any work of storytelling , but it 's particularly prominent in `` the magic flute '' : three trials , three ladies , three spirits , and three doors , much of the music is written in e-flat major , which has three flats in its key signature , and historically , masonic rituals began with three knocks . the opera references them by opening with three majestic chords complete with dramatic pauses . those chords , which reoccur throughout the opera , serve another purpose . they capture the dramatic arc of the opera in miniature . the first chord , e-flat major , is in its most natural root position , simple and unadorned . it echoes the child-like prince tamino , who , in his naiveté , accepts everything the queen and her ladies say without question . the second chord is c minor , a sour sonority that mirrors tamino 's sadness and doubt in the middle of the opera . that 's when his world and notions of good and evil get turned on their heads . and good and evil are just two of the opera 's extreme opposites . it features some of the highest and lowest notes in opera , day and night , simple hummable melodies and complicated forward-looking music . the opera 's central theme concerns balancing these extremes to achieve perfect harmony . to reflect this , the final chord in the opening restores musical order . it returns to the triumphant e-flat major , the same chord it started with but inverted , meaning mozart moved the bottom note to the top . although it retains its original harmony , the chord sounds higher , pointing towards enlightenment . that 's similar to tamino , who in passing his trials restores balance to the kingdom while growing stronger , wiser , and more complete .
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just as it rears up to devour him , three mysterious ladies appear and slay the dragon with their fierce battle cry . so begins wolfgang amadeus mozart 's `` die zauberflöte , '' or `` the magic flute . '' this fantasy singspiel , a type of folk opera with music and dialogue , premiered in 1791 in vienna .
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enlightenment is symbolized within the `` magic flute . '' how ?
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now and then i think of what i learned in high school like ap bio and british literature is that igneous or metamorphic ? i do n't need to write a nine bic and i 'll admit i do n't know shit about millard fillmore why did i have to learn this stuff ? it is never common -- had they never used it for nothing ? why did we have to read the scarlet letter ? puritans are boring even when one is a slut there 's actually one thing i still know eli whitney he invented the cotton gin definitely do not need that , though now it 's just a study that i used to know now it 's just a study that i used to know now and then i think of all the things i 've taught you every handout with a far side cartoon apropo you do n't want to live that way forgetting every word i say you said you 'd never let it go i guess mnemonic devices just were n't enough for you though you really freaking pissed me off i worked so hard to teach you something , now you do n't know nothing what does the comment symbolize ? or anything beyond the first three digits of pi and what about sohcahtoa or asexual reproduction of a protozoa i guess you did n't need that though now it 's just a study that you used to know a study i used to know now it 's just a study that you used to know i used to know a study
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now and then i think of what i learned in high school like ap bio and british literature is that igneous or metamorphic ? i do n't need to write a nine bic and i 'll admit i do n't know shit about millard fillmore why did i have to learn this stuff ?
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art assignment : what can you remember from high school ? imagine using a large blank paper to create an illustrated mindmap of the subjects you studied and what you remember from those classes . how big a paper would you need and how long would it take to get most of the way through it ( 80 % done ) ?
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you probably already know everything is made up of little tiny things called atoms or even that each atom is made up of even smaller particles called protons , neutrons and electrons . and you 've probably heard that atoms are small . but i bet you have n't ever thought about how small atoms really are . well , the answer is that they are really , really small . so you ask , just how small are atoms ? to understand this , let 's ask this question : how many atoms are in a grapefruit ? well , let 's assume that the grapefruit is made up of only nitrogen atoms , which is n't at all true , but there are nitrogen atoms in a grapefruit . to help you visualize this , let 's blow up each of the atoms to the size of a blueberry . and then how big would the grapefruit have to be ? it would have to be the same size of -- well , actually , the earth . that 's crazy ! you mean to say that if i filled the earth with blueberries , i would have the same number of nitrogen atoms as a grapefruit ? that 's right ! so how big is the atom ? well , it 's really , really small ! and you know what ? it gets even more crazy . let 's now look inside of each atom -- and thus the blueberry , right ? -- what do you see there ? in the center of the atom is something called the nucleus , which contains protons and neutrons , and on the outside , you 'd see electrons . so how big is the nucleus ? if atoms are like blueberries in the earth , how big would the nucleus be ? you might remember the old pictures of the atom from science class , where you saw this tiny dot on the page with an arrow pointing to the nucleus . well , those pictures , they 're not drawn to scale , so they 're kind of wrong . so how big is the nucleus ? so if you popped open the blueberry and were searching for the nucleus ... you know what ? it would be invisible . it 's too small to see ! ok. let 's blow up the atom -- the blueberry -- to the size of a house . so imagine a ball that is as tall as a two-story house . let 's look for the nucleus in the center of the atom . and do you know what ? it would just barely be visible . so to get our minds wrapped around how big the nucleus is , we need to blow up the blueberry , up to the size of a football stadium . so imagine a ball the size of a football stadium , and right smack dab in the center of the atom , you would find the nucleus , and you could see it ! and it would be the size of a small marble . and there 's more , if i have n't blown your mind by now . let 's consider the atom some more . it contains protons , neutrons and electrons . the protons and neutrons live inside of the nucleus , and contain almost all of the mass of the atom . way on the edge are the electrons . so if an atom is like a ball the size of a football stadium , with the nucleus in the center , and the electrons on the edge , what is in between the nucleus and the electrons ? surprisingly , the answer is empty space . ( wind noise ) that 's right . empty ! between the nucleus and the electrons , there are vast regions of empty space . now , technically there are some electromagnetic fields , but in terms of stuff , matter , it is empty . remember this vast region of empty space is inside the blueberry , which is inside the earth , which really are the atoms in the grapefruit . ok , one more thing , if i can even get more bizarre . since virtually all the mass of an atom is in the nucleus -- now , there is some amount of mass in the electrons , but most of it is in the nucleus -- how dense is the nucleus ? well , the answer is crazy . the density of a typical nucleus is four times 10 to the 17th kilograms per meter cubed . but that 's hard to visualize . ok , i 'll put it in english units . 2.5 times 10 to the 16th pounds per cubic feet . ok , that 's still kind of hard to figure . ok , here 's what i want you to do . make a box that is one foot by one foot by one foot . now let 's go and grab all of the nuclei from a typical car . now , cars on average weigh two tons . how many cars ' nuclei would you have to put into the box to have your one-foot-box have the same density of the nucleus ? is it one car ? two ? how about 100 ? nope , nope and nope . the answer is much bigger . it is 6.2 billion . that is almost equal to the number of people in the earth . so if everyone in the earth owned their own car -- and they do n't -- ( cars honking ) and we put all of those cars into your box ... that would be about the density of a nucleus . so i 'm saying that if you took every car in the world and put it into your one-foot box , you would have the density of one nucleus . ok , let 's review . the atom is really , really , really small . think atoms in a grapefruit like blueberries in the earth . the nucleus is crazy small . now look inside the blueberry , and blow it up to the size of a football stadium , and now the nucleus is a marble in the middle . the atom is made up of vast regions of empty space . that 's weird . the nucleus has a crazy-high density . think of putting all those cars in your one-foot box . i think i 'm tired .
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ok , let 's review . the atom is really , really , really small . think atoms in a grapefruit like blueberries in the earth .
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come up with your own analogy as to the size of an atom . do some proportions to determine how you could describe how small an atom is .
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at about six o'clock in the morning on september 14 , 2015 , scientists witnessed something no human had ever seen : two black holes colliding . both about 30 times as massive as our sun , they had been orbiting each other for millions of years . as they got closer together , they circled each other faster and faster . finally , they collided and merged into a single , even bigger , black hole . a fraction of a second before their crash , they sent a vibration across the universe at the speed of light . and on earth , billions of years later , a detector called the laser interferometer gravitational wave observatory , or ligo for short , picked it up . the signal only lasted a fifth of a second and was the detector 's first observation of gravitational waves . what are these ripples in space ? the answer starts with gravity , the force that pulls any two objects together . that 's the case for everything in the observable universe . you 're pulling on the earth , the moon , the sun , and every single star , and they 're pulling on you . the more mass something has , the stronger its gravitational pull . the farther away the object , the lower its pull . if every mass has an effect on every other mass in the universe , no matter how small , then changes in gravity can tell us about what those objects are doing . fluctuations in the gravity coming from the universe are called gravitational waves . gravitational waves move out from what caused them , like ripples on a pond , getting smaller as they travel farther from their center . but what are they ripples on ? when einstein devised his theory of relativity , he imagined gravity as a curve in a surface called space-time . a mass in space creates a depression in space-time , and a ball rolling across a depression will curve like it 's being attracted to the other mass . the bigger the mass , the deeper the depression and the stronger the gravity . when the mass making the depression moves , that sends out ripples in space-time . these are gravitationl waves . what would a gravitational wave feel like ? if our bodies were sensitive enough to detect them , we 'd feel like we were being stretched sideways while being compressed vertically . and in the next instant , stretched up and down while being compressed horizontally , sideways , then up and down . this back and forth would happen over and over as the gravitational wave passed right through you . but this happens on such a minute scale that we ca n't feel any of it . so we 've built detectors that can feel it for us . that 's what the ligo detectors do . and they 're not the only ones . there are gravitational wave detectors spread across the world . these l-shaped instruments have long arms , whose exact length is measured with lasers . if the length changes , it could be because gravitational waves are stretching and compressing the arms . once the detectors feel a gravitational wave , scientists can extract information about the wave 's source . in a way , detectors like ligo are big gravitational wave radios . radio waves are traveling all around you , but you ca n't feel them or hear the music they carry . it takes the right kind of detector to extract the music . ligo detects a gravitational wave signal , which scientists then study for data about the object that generated it . they can derive information , like its mass and the shape of its orbit . we can also hear gravitational waves by playing their signals through speakers , just like the music a radio extracts from radio waves . so those two black holes colliding sounds like this . scientists call this slide whistle-like noise a chirp , and it 's the signature of any two objects orbiting into each other . the black hole collision was just one example of what gravitational waves can tell us . other high-energy astronomical events will leave gravitational echoes , too . the collapse of a star before it explodes in a supernova , or a very dense neutron stars colliding . every time we create a new tool to look at space , we discover something we did n't expect , something that might revolutionize our understanding of the universe . ligo 's no different . in the short time it 's been on , ligo 's already revealed surprises , like that black holes collide more often than we ever expected . it 's impossible to say , but exciting to imagine , what revelations may now be propagating across space towards our tiny blue planet and its new way of perceiving the universe .
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the bigger the mass , the deeper the depression and the stronger the gravity . when the mass making the depression moves , that sends out ripples in space-time . these are gravitationl waves .
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which of the following statements is false about space-time ?
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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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squirrels and voles peek out of penthouse burrows . and the top predator ? the mighty wandering salamander !
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what is the top predator in the ancient coast redwood canopy ?
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probability is an area of mathematics that is everywhere . we hear about it in weather forecasts , like there 's an 80 % chance of snow tomorrow . it 's used in making predictions in sports , such as determining the odds for who will win the super bowl . probability is also used in helping to set auto insurance rates and it 's what keeps casinos and lotteries in business . how can probability affect you ? let 's look at a simple probability problem . does it pay to randomly guess on all 10 questions on a true/ false quiz ? in other words , if you were to toss a fair coin 10 times , and use it to choose the answers , what is the probability you would get a perfect score ? it seems simple enough . there are only two possible outcomes for each question . but with a 10-question true/ false quiz , there are lots of possible ways to write down different combinations of ts and fs . to understand how many different combinations , let 's think about a much smaller true/ false quiz with only two questions . you could answer `` true true , '' or `` false false , '' or one of each . first `` false '' then `` true , '' or first `` true '' then `` false . '' so that 's four different ways to write the answers for a two-question quiz . what about a 10-question quiz ? well , this time , there are too many to count and list by hand . in order to answer this question , we need to know the fundamental counting principle . the fundamental counting principle states that if there are a possible outcomes for one event , and b possible outcomes for another event , then there are a times b ways to pair the outcomes . clearly this works for a two-question true/ false quiz . there are two different answers you could write for the first question , and two different answers you could write for the second question . that makes 2 times 2 , or , 4 different ways to write the answers for a two-question quiz . now let 's consider the 10-question quiz . to do this , we just need to extend the fundamental counting principle a bit . we need to realize that there are two possible answers for each of the 10 questions . so the number of possible outcomes is 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 , times 2 . or , a shorter way to say that is 2 to the 10th power , which is equal to 1,024 . that means of all the ways you could write down your ts and fs , only one of the 1,024 ways would match the teacher 's answer key perfectly . so the probability of you getting a perfect score by guessing is only 1 out of 1,024 , or about a 10th of a percent . clearly , guessing is n't a good idea . in fact , what would be the most common score if you and all your friends were to always randomly guess at every question on a 10-question true/ false quiz ? well , not everyone would get exactly 5 out of 10 . but the average score , in the long run , would be 5 . in a situation like this , there are two possible outcomes : a question is right or wrong , and the probability of being right by guessing is always the same : 1/2 . to find the average number you would get right by guessing , you multiply the number of questions by the probability of getting the question right . here , that is 10 times 1/2 , or 5 . hopefully you study for quizzes , since it clearly does n't pay to guess . but at one point , you probably took a standardized test like the sat , and most people have to guess on a few questions . if there are 20 questions and five possible answers for each question , what is the probability you would get all 20 right by randomly guessing ? and what should you expect your score to be ? let 's use the ideas from before . first , since the probability of getting a question right by guessing is 1/5 , we would expect to get 1/5 of the 20 questions right . yikes - that 's only four questions ! are you thinking that the probability of getting all 20 questions correct is pretty small ? let 's find out just how small . do you recall the fundamental counting principle that was stated before ? with five possible outcomes for each question , we would multiply 5 times 5 times 5 times 5 times ... well , we would just use 5 as a factor 20 times , and 5 to the 20th power is 95 trillion , 365 billion , 431 million , 648 thousand , 625 . wow - that 's huge ! so the probability of getting all questions correct by randomly guessing is about 1 in 95 trillion .
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clearly , guessing is n't a good idea . in fact , what would be the most common score if you and all your friends were to always randomly guess at every question on a 10-question true/ false quiz ? well , not everyone would get exactly 5 out of 10 .
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on a ten-question true-false quiz , what would be your average score in the long run if you randomly guessed on every question ?
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it 's a good day to be a pirate . amaro and his four mateys , bart , charlotte , daniel , and eliza have struck gold : a chest with 100 coins . but now , they must divvy up the booty according to the pirate code . as captain , amaro gets to propose how to distribute the coins . then , each pirate , including amaro himself , gets to vote either yarr or nay . if the vote passes , or if there 's a tie , the coins are divided according to plan . but if the majority votes nay , amaro must walk the plank and bart becomes captain . then , bart gets to propose a new distribution and all remaining pirates vote again . if his plan is rejected , he walks the plank , too , and charlotte takes his place . this process repeats , with the captain 's hat moving to daniel and then eliza until either a proposal is accepted or there 's only one pirate left . naturally , each pirate wants to stay alive while getting as much gold as possible . but being pirates , none of them trust each other , so they ca n't collaborate in advance . and being blood-thirsty pirates , if anyone thinks they 'll end up with the same amount of gold either way , they 'll vote to make the captain walk the plank just for fun . finally , each pirate is excellent at logical deduction and knows that the others are , too . what distribution should amaro propose to make sure he lives ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 if we follow our intuition , it seems like amaro should try to bribe the other pirates with most of the gold to increase the chances of his plan being accepted . but it turns out he can do much better than that . why ? like we said , the pirates all know each other to be top-notch logicians . so when each votes , they wo n't just be thinking about the current proposal , but about all possible outcomes down the line . and because the rank order is known in advance , each can accurately predict how the others would vote in any situation and adjust their own votes accordingly . because eliza 's last , she has the most outcomes to consider , so let 's start by following her thought process . she 'd reason this out by working backwards from the last possible scenario with only her and daniel remaining . daniel would obviously propose to keep all the gold and eliza 's one vote would not be enough to override him , so eliza wants to avoid this situation at all costs . now we move to the previous decision point with three pirates left and charlotte making the proposal . everyone knows that if she 's outvoted , the decision moves to daniel , who will then get all the gold while eliza gets nothing . so to secure eliza 's vote , charlotte only needs to offer her slightly more than nothing , one coin . since this ensures her support , charlotte does n't need to offer daniel anything at all . what if there are four pirates ? as captain , bart would still only need one other vote for his plan to pass . he knows that daniel would n't want the decision to pass to charlotte , so he would offer daniel one coin for his support with nothing for charlotte or eliza . now we 're back at the initial vote with all five pirates standing . having considered all the other scenarios , amaro knows that if he goes overboard , the decision comes down to bart , which would be bad news for charlotte and eliza . so he offers them one coin each , keeping 98 for himself . bart and daniel vote nay , but charlotte and eliza grudgingly vote yarr knowing that the alternative would be worse for them . the pirate game involves some interesting concepts from game theory . one is the concept of common knowledge where each person is aware of what the others know and uses this to predict their reasoning . and the final distribution is an example of a nash equilibrium where each player knows every other players ' strategy and chooses theirs accordingly . even though it may lead to a worse outcome for everyone than cooperating would , no individual player can benefit by changing their strategy . so it looks like amaro gets to keep most of the gold , and the other pirates might need to find better ways to use those impressive logic skills , like revising this absurd pirate code .
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one is the concept of common knowledge where each person is aware of what the others know and uses this to predict their reasoning . and the final distribution is an example of a nash equilibrium where each player knows every other players ' strategy and chooses theirs accordingly . even though it may lead to a worse outcome for everyone than cooperating would , no individual player can benefit by changing their strategy .
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explain why everyone votes the way they do in the final distribution .
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imagine the brain could reboot , updating its withered and damaged cells with new , improved units . that may sound like science fiction , but it 's a potential reality scientists are investigating right now . will our brains one day be able to self-repair ? it 's well known that embryonic cells in our young developing brains produce new neurons , the microscopic units that make up the brain 's tissue . those newly generated neurons migrate to various parts of the developing brain , making it self-organize into different structures . but until recently , scientists thought cell production came to an abrupt halt soon after this initial growth , leading them to conclude that neurological diseases , like alzheimer 's and parkinson 's , and damaging events , like strokes , are irreversible . but a series of recent discoveries has revealed that adult brains actually do continue to produce new cells in at least three specialized locations . this process , known as neurogenesis , involves dedicated brain cells , called neural stem cells and progenitor cells , which manufacture new neurons or replace the old ones . the three regions where neurogenesis has been discovered are the dentate gyrus , associated with learning and memory , the subventricular zone , which may supply neurons to the olfactory bulb for communication between the nose and brain , and the striatum , which helps manage movement . scientists do n't yet have a good grasp on exactly what role neurogenesis plays in any of these regions , or why they have this ability that 's absent from the rest of the brain , but the mere presence of a mechanism to grown new neurons in the adult brain opens up an amazing possibility . could we harness that mechanism to get the brain to heal its scars similar to how new skin grows to patch up a wound , or a broken bone stitches itself back together ? so here 's where we stand . certain proteins and other small molecules that mimick those proteins can be administered to the brain to make neural stem cells and progenitor cells produce more neurons in those three locations . this technique still needs improvement so that the cells reproduce more efficiently and more cells survive . but research shows that progenitor cells from these areas can actually migrate to places where injury has occurred and give rise to new neurons there . and another promising possible approach is to transplant healthy human neural stem cells , which are cultured in a laboratory , to injured tissue , like we can do with skin . scientists are currently experimenting to determine whether transplanted donor cells can divide , differentiate and successfully give rise to new neurons in a damaged brain . they 've also discovered that we might be able to teach other kinds of brain cells , such as astrocytes or oligodendrocytes to behave like neural stem cells and start generating neurons , too . so , a couple of decades from now will our brains be able to self-repair ? we ca n't say for sure , but that has become one of the major goals of regenerative medicine . the human brain has 100 billion neurons and we 're still figuring out the wiring behind this huge biological motherboard . but everyday , research on neurogenesis brings us closer to that reboot switch .
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but until recently , scientists thought cell production came to an abrupt halt soon after this initial growth , leading them to conclude that neurological diseases , like alzheimer 's and parkinson 's , and damaging events , like strokes , are irreversible . but a series of recent discoveries has revealed that adult brains actually do continue to produce new cells in at least three specialized locations . this process , known as neurogenesis , involves dedicated brain cells , called neural stem cells and progenitor cells , which manufacture new neurons or replace the old ones . the three regions where neurogenesis has been discovered are the dentate gyrus , associated with learning and memory , the subventricular zone , which may supply neurons to the olfactory bulb for communication between the nose and brain , and the striatum , which helps manage movement .
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which cells in the adult brain produce new neurons ?
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in 1861 , two scientists got into a very brainy argument . specifically , they had opposing ideas of how speech and memory operated within the human brain . ernest aubertin , with his localistic model , argued that a particular region or the brain was devoted to each separate process . pierre gratiolet , on the other hand , argued for the distributed model , where different regions work together to accomplish all of these various functions . the debate they began reverberated throughout the rest of the century , involving some of the greatest scientific minds of the time . aubertin and his localistic model had some big names on his side . in the 17th century , rené descartes had assigned the quality of free will and the human soul to the pineal gland . and in the late 18th century , a young student named franz joseph gall had observed that the best memorizers in his class had the most prominent eyes and decided that this was due to higher development in the adjacent part of the brain . as a physician , gall went on to establish the study of phrenology , which held that strong mental faculties corresponded to highly developed brain regions , observable as bumps in the skull . the widespread popularity of phrenology throughout the early 19th century tipped the scales towards aubertin 's localism . but the problem was that gall had never bothered to scientifically test whether the individual brain maps he had constructed applied to all people . and in the 1840 's , pierre flourens challenged phrenology by selectively destroying parts of animal brains and observing which functions were lost . flourens found that damaging the cortex interfered with judgement or movement in general , but failed to identify any region associated with one specific function , concluding that the cortex carried out brain functions as an entire unit . flourens had scored a victory for gratiolet , but it was not to last . gall 's former student , jean-baptiste bouillaud , challenged flourens ' conclusion , observing that patients with speech disorders all had damage to the frontal lobe . and after paul broca 's 1861 autopsy of a patient who had lost the power to produce speech , but not the power to understand it , revealed highly localized frontal lobe damage , the distributed model seemed doomed . localism took off . in the 1870 's , karl wernicke associated part of the left temporal lobe with speech comprehension . soon after , eduard hitzig and gustav fritsch stimulated a dog 's cortex and discovered a frontal lobe region responsible for muscular movements . building on their work , david ferrier mapped each piece of cortex associated with moving a part of the body . and in 1909 , korbinian brodmann built his own cortex map with 52 separate areas . it appeared that the victory of aubertin 's localistic model was sealed . but neurologist karl wernicke had come up with an interesting idea . he reasoned that since the regions for speech production and comprehension were not adjacent , then injuring the area connecting them might result in a special type of language loss , now known as receptive aphasia . wernicke 's connectionist model helped explain disorders that did n't result from the dysfunction of just one area . modern neuroscience tools reveal a brain more complex than gratiolet , aubertin , or even wernicke imagined . today , the hippocampus is associated with two distinct brain functions : creating memories and processing location in space . we also now measure two kinds of connectivity : anatomical connectivity between two adjoining regions of cortex working together , and functional connectivity between separated regions working together to accomplish one process . a seemingly basic function like vision is actually composed of many smaller functions , with different parts of the cortex representing shape , color and location in space . when certain areas stop functioning , we may recognize an object , but not see it , or vice versa . there are even different kinds of memory for facts and for routines . and remembering something like your first bicycle involves a network of different regions each representing the concept of vehicles , the bicycle 's shape , the sound of the bell , and the emotions associated with that memory . in the end , both gratiolet and aubertin turned out to be right . and we still use both of their models to understand how cognition happens . for example , we can now measure brain activity on such a fine time scale that we can see the individual localized processes that comprise a single act of remembering . but it is the integration of these different processes and regions that creates the coherent memory we experience . the supposedly competing theories prove to be two aspects of a more comprehensive model , which will in turn be revised and refined as our scientific techologies and methods for understanding the brain improve .
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in 1861 , two scientists got into a very brainy argument . specifically , they had opposing ideas of how speech and memory operated within the human brain . ernest aubertin , with his localistic model , argued that a particular region or the brain was devoted to each separate process .
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are the brain areas responsible for carrying out the production and comprehension of speech the same or different ? how do we know ?
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on a december afternoon in chicago during the middle of world war ii , scientists cracked open the nucleus at the center of the uranium atom and turned nuclear mass into energy over and over again . they did this by creating for the first time a chain reaction inside a new engineering marvel : the nuclear reactor . since then , the ability to mine great amounts of energy from uranium nuclei has led some to bill nuclear power as a plentiful utopian source of electricity . a modern nuclear reactor generates enough electricity from one kilogram of fuel to power an average american household for nearly 34 years . but rather than dominate the global electricity market , nuclear power has declined from an all-time high of 18 % in 1996 to 11 % today . and it 's expected to drop further in the coming decades . what happened to the great promise of this technology ? it turns out nuclear power faces many hurdles , including high construction costs and public opposition . and behind these problems lie a series of unique engineering challenges . nuclear power relies on the fission of uranium nuclei and a controlled chain reaction that reproduces this splitting in many more nuclei . the atomic nucleus is densely packed with protons and neutrons bound by a powerful nuclear force . most uranium atoms have a total of 238 protons and neutrons , but roughly one in every 140 lacks three neutrons , and this lighter isotope is less tightly bound . compared to its more abundant cousin , a strike by a neutron easily splits the u-235 nuclei into lighter , radioactive elements called fission products , in addition to two to three neutrons , gamma rays , and a few neutrinos . during fission , some nuclear mass transforms into energy . a fraction of the newfound energy powers the fast-moving neutrons , and if some of them strike uranium nuclei , fission results in a second larger generation of neutrons . if this second generation of neutrons strike more uranium nuclei , more fission results in an even larger third generation , and so on . but inside a nuclear reactor , this spiraling chain reaction is tamed using control rods made of elements that capture excess neutrons and keep their number in check . with a controlled chain reaction , a reactor draws power steadily and stably for years . the neutron-led chain reaction is a potent process driving nuclear power , but there 's a catch that can result in unique demands on the production of its fuel . it turns out , most of the neutrons emitted from fission have too much kinetic energy to be captured by uranium nuclei . the fission rate is too low and the chain reaction fizzles out . the first nuclear reactor built in chicago used graphite as a moderator to scatter and slow down neutrons just enough to increase their capture by uranium and raise the rate of fission . modern reactors commonly use purified water as a moderator , but the scattered neutrons are still a little too fast . to compensate and keep up the chain reaction , the concentration of u-235 is enriched to four to seven times its natural abundance . today , enrichment is often done by passing a gaseous uranium compound through centrifuges to separate lighter u-235 from heavier u-238 . but the same process can be continued to highly enrich u-235 up to 130 times its natural abundance and create an explosive chain reaction in a bomb . methods like centrifuge processing must be carefully regulated to limit the spread of bomb-grade fuel . remember , only a fraction of the released fission energy goes into speeding up neutrons . most of the nuclear power goes into the kinetic energy of the fission products . those are captured inside the reactor as heat by a coolant , usually purified water . this heat is eventually used to drive an electric turbine generator by steam just outside the reactor . water flow is critical not only to create electricity , but also to guard against the most dreaded type of reactor accident , the meltdown . if water flow stops because a pipe carrying it breaks , or the pumps that push it fail , the uranium heats up very quickly and melts . during a nuclear meltdown , radioactive vapors escape into the reactor , and if the reactor fails to hold them , a steel and concrete containment building is the last line of defense . but if the radioactive gas pressure is too high , containment fails and the gasses escape into the air , spreading as far and wide as the wind blows . the radioactive fission products in these vapors eventually decay into stable elements . while some decay in a few seconds , others take hundreds of thousands of years . the greatest challenge for a nuclear reactor is to safely contain these products and keep them from harming humans or the environment . containment does n't stop mattering once the fuel is used up . in fact , it becomes an even greater storage problem . every one to two years , some spent fuel is removed from reactors and stored in pools of water that cool the waste and block its radioactive emissions . the irradiated fuel is a mix of uranium that failed to fission , fission products , and plutonium , a radioactive material not found in nature . this mix must be isolated from the environment until it has all safely decayed . many countries propose deep time storage in tunnels drilled far underground , but none have been built , and there 's great uncertainty about their long-term security . how can a nation that has existed for only a few hundred years plan to guard plutonium through its radioactive half-life of 24,000 years ? today , many nuclear power plants sit on their waste , instead , storing them indefinitely on site . apart from radioactivity , there 's an even greater danger with spent fuel . plutonium can sustain a chain reaction and can be mined from the waste to make bombs . storing spent fuel is thus not only a safety risk for the environment , but also a security risk for nations . who should be the watchmen to guard it ? visionary scientists from the early years of the nuclear age pioneered how to reliably tap the tremendous amount of energy inside an atom - as an explosive bomb and as a controlled power source with incredible potential . but their successors have learned humbling insights about the technology 's not-so-utopian industrial limits . mining the subatomic realm makes for complex , expensive , and risky engineering .
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the greatest challenge for a nuclear reactor is to safely contain these products and keep them from harming humans or the environment . containment does n't stop mattering once the fuel is used up . in fact , it becomes an even greater storage problem . every one to two years , some spent fuel is removed from reactors and stored in pools of water that cool the waste and block its radioactive emissions . the irradiated fuel is a mix of uranium that failed to fission , fission products , and plutonium , a radioactive material not found in nature . this mix must be isolated from the environment until it has all safely decayed .
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it is apparent that the spent radioactive fuel of nuclear reactors needs to be safely stored here on earth , however the radioactive lifetimes of the fuel products may long outlast the lifetime of social and political creations like states and nations . what new challenges for international cooperation might this unique storage problem pose ?
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we 've all seen movies about terrible insects from outer space or stories of abduction by little green men , but the study of life in the universe , including the possibility of extraterrestrial life , is also a serious , scientific pursuit . astrobiology draws on diverse fields , such as physics , biology , astronomy , and geology , to study how life was formed on earth , how it could form elsewhere , and how we might detect it . many ancient religions described other worlds inhabited by known human beings , but these are more like mythical realms or parallel universes than other planets existing in the same physical world . it is only within the last century that scientists have been able to seriously undertake the search for extraterrestrial life . we know that at the most basic level organisms on earth need three things : liquid water , a source of energy , and organic , carbon-based material . we also know that the earth is just the right distance from the sun , so as not to be either frozen or molten . so , planets within such a habitable range from their own stars may be able to support life . but while we used to think that life could only exist in such earth-like environments , one of the most amazing discoveries of astrobiology has been just how versatile life is . we now know that life can thrive in some of the most extreme environments that 'd be fatal for most known organisms . life is found everywhere , from black smoke of hydrothermal vents in the dark depths of earth 's oceans , to bubbling , hot , acidic springs on the flanks of volcanoes , to high up in the atmosphere . organisms that live in these challenging environments are called extremophiles , and they can survive at extremes of temperature , pressure , and radiation , as well as salinity , acidity , and limited availability of sunlight , water , or oxygen . what is most remarkable about these extremophiles is that they are found thriving in environments that mimic those on alien worlds . one of the most important of these worlds is our red and dusty neighbor , mars . today , astrobiologists are exploring places where life might once have existed on mars using nasa 's curiosity rover . one of these is gale crater , an impact crater created when a meteor hit the surface of mars nearly 3.8 billions years ago . evidence from orbit suggest past traces of water , which means the crater might once have supported life . planets are not the only places astrobiologists are looking at . for example , europa , one of the moons of jupiter , and enceladus and titan , two of saturn 's moons , are all exciting possibilities . although these moons are extremely cold and two are covered in thick ice , there is evidence of liquid oceans beneath the shell . could life be floating around in these oceans , or could it be living around black smoker vents at the bottom ? titan is particularly promising as it has an atmosphere and earth-like lakes , seas , and rivers flowing across the surface . it is very cold , however , too cold for liquid water , so these rivers may instead be flowing with liquid hydrocarbons such as methane and ethane . these are composed of hydrogen , and , more importantly , carbon , which is the basic building block of all life as we know it . so , could life be found in these lakes ? although instruments are being designed to study these distant worlds , it takes many years to build them and even longer to get them where they need to be . in the meantime , astrobiologists work in our own natural laboratory , the earth , to learn about all the weird and wonderful forms of life that can exist and to help us one day answer one of humanity 's oldest questions : are we alone ?
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planets are not the only places astrobiologists are looking at . for example , europa , one of the moons of jupiter , and enceladus and titan , two of saturn 's moons , are all exciting possibilities . although these moons are extremely cold and two are covered in thick ice , there is evidence of liquid oceans beneath the shell .
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the moons of enceladus and titan orbit which planet ?
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the term modern art sounds like it means art that is popular at the moment , but in fact , modern art is a style that originated over 150 years ago , and includes artists that by now have attained classic status , such as picasso , matisse , and gauguin . and what 's even more ironic is that the movement they pioneered , considered revolutionary and even scandalous at the time , was inspired largely by an object of a traditional and ancient design . as far back as the renaissance , the primary european art movements emphasized conventional representation and adherence to classical forms . but that began to change in the late 19th century as artists like van gogh and cézanne expanded the boundaries of painting . soon , a movement arose that sought to create an entirely new style of art , and one way of doing so was to look beyond western civilization . for example , paul gauguin moved to the island of tahiti in the 1890s . there , he found inspiration in the island 's inhabitants , landscape , and culture to create artwork that intertwined european themes and polynesian lore . others looked the cultures of the islamic world , but the most influential inspiration would come from sub-saharan africa . as european empires expanded deeper into the african continent , its artifacts and artworks made their way into the hands of museums and collectors . one such collector was henri matisse , who showed his friend picasso a mask he had acquired made by the dan tribe of the ivory coast . the mask awoke picasso 's curiosity , leading him to visit the trocadéro ethnographic museum in paris in 1907 . founded to house acquisitions from colonial conquests , the museum boasted a collection of african art , with stylized figures and masks made of wood and decorated with simple colors and materials . the visit was a revelation for picasso , who proclaimed that african masks were what painting was all about . at this time , picasso had been working on a painting of five nude women in a style that would later come to be known as cubism . and while three of these ladies show facial features found in ancient iberian art , a nod to picasso 's spanish heritage , the faces of the two on the right closely resemble african masks . created in 1907 after hundreds of sketches and studies , `` les demoiselles d'avignon '' has been considered the first truly 20th century masterpiece , breaking with many previously held notions in art . it was at once aggressive and abstract , distorted yet primal in its raw geometry , a new artistic language with new forms , colors , and meanings . and these avant-garde qualities caused a sensation when the painting was first exhibited almost ten years later . the public was shocked , critics denounced it as immoral , and even picasso 's own friends were simultaneously surprised , offended , and mesmerized at his audacity . more artists soon followed in picasso 's footsteps . constantin brâncuși and amedeo modigliani in paris , as well as the german expressionists , all drew on the aesthetics of african sculptures in their work . others looked to a different continent for their inspiration . british sculptor henry moore based many of his semi-abstract bronze sculptures on a replica of a chacmool , a distinctive reclining statue from the toltec-maya culture . pre-columbian art was also a major influence for josef albers . he created a series of compositions , such as the geometrical series homage to the square , that were inspired by pyramids and local art he encountered on his frequent visits to mexico . inspiration from ancient cultures initiated one of the most revolutionary movements in art history , but were these artists playing the role of explorers or conquistadors , appropriating ideas and profiting from cultures they considered primitive ? questions like this deserve scrutiny , as artists continue to redefine standards . perhaps not too long from now , the bold innovations of modern art will seem like stale orthodoxies , ready to be overturned by a new set of radical trailblazers drawing inspiration from another unlikely source .
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the term modern art sounds like it means art that is popular at the moment , but in fact , modern art is a style that originated over 150 years ago , and includes artists that by now have attained classic status , such as picasso , matisse , and gauguin . and what 's even more ironic is that the movement they pioneered , considered revolutionary and even scandalous at the time , was inspired largely by an object of a traditional and ancient design .
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name the artist who was a precursor of modern art .
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( music ) ( music ) we live in an interconnected , an increasingly globalized world . thanks to international jet travel , people and the diseases they carry can be in any city on the planet in a matter of hours . and once a virus touches down , sometimes all it takes is one sneeze to spread the infection throughout the community . when humans were hunter-gatherers , roaming the wild savannas , we were never in one place long enough , and settlements were not large enough to sustain the transmission of infectious microbes . but with the advent of the agricultural revolution 10,000 years ago , and the arrival of permanent settlements in the middle east , people began living side-by-side with animals , facilitating the spread of bacteria and viruses between cattle and humans . epidemics and pandemics come in many shapes and forms . in 2010 , for instance , a devastating earthquake struck haiti , forcing thousands of people into temporary refugee camps . within weeks , the camps had become breeding grounds for cholera , a bacteria spread by contaminated water , triggering a country-wide epidemic . but the most common cause of epidemics are viruses , such as measles , influenza and hiv . and when they go global , we call them pandemics . pandemics have occurred throughout human history , some have left scars on the tissue and bone of their victims , while evidence for others comes from preserved dna . for instance , scientists have recovered dna from the bacteria that transmits tuberculosis from the remains of ancient egyptian mummies . and in 2011 , scientists investigating a plague pit in the city of london were able to reconstruct the genome of yersinia pestis , the bacterium responsible for the black death of the 14th century . it is thought the plague originated in china in around 1340 , spreading west along the silk road , the caravan route running from mongolia to the crimea . in 1347 , the plague reached the mediterranean , and by 1400 , it had killed in excess of 34 million europeans , earning it the title , the great mortality . it was later historians who called it the black death . however , by far the greatest pandemic killer is influenza . flu is constantly circulating between the southern and northern hemispheres . in north america and europe , seasonal flus occur every autumn and winter . as the majority of children and adults will have been exposed to the virus in previous seasons , these illnesses are usually mild . however , every 20 to 40 years or so the virus undergoes a dramatic mutation . usually this occurs when a wild flu virus circulating in ducks and farm poultry meets a pig virus , and they exchange genes . this process is known as antigenic shift and has occurred throughout human history . the first recorded pandemic occurred in 1580 . the 18th and 19th centuries saw at least six further pandemics . in terms of mortality , none can compare with the great flu pandemic of 1918 . the first indication of the pandemic came in the spring , when american troops in northern france began complaining of chills , headaches and fever . then , the following september , at a u.s. army barracks near boston , soldiers started collapsing on parade , prompting their removal to the camp infirmary . as a surgeon there recalled , two hours after admission , they had the mahogany spots over the cheekbones and a few hours later you can begin to see the cyanosis extending from their ears and spreading all over the face . it is only a matter of a few hours then until death comes , and it is simply a struggle for air until they suffocate . on the s.s. leviathan , a huge american transport en route to bordeaux , sick men hemorrhaged blood from their noses , turning the decks between their bunks slick with bodily fluids . meanwhile , british soldiers returning from northern france on furlough introduced the flu to dover and other channel ports , from where the virus was carried by rail to london . by the time the pandemic had run its course in april 1919 , an estimated 675,000 americans and 230,000 britons were dead . in india alone , some 10 million were killed , and worldwide the death toll was an astonishing 50 million . but that was then . today , planes can transport viruses to any country on the globe in a fraction of the time it took in 1918 . in february 2003 , for instance , a chinese doctor arrived at the metropole hotel in hong kong feeling unwell . unknown to him , he was harboring a new animal-origin virus called sars , short for severe acute respiratory syndrome . within 24 hours of checking into room 913 , sixteen other guests had been infected , and over the following days five boarded planes to overseas destinations , spreading the virus to vietnam , singapore and canada . flights between hong kong , toronto and other international cities were quickly grounded and thanks to other emergency measures , a pandemic was averted . by the time the outbreak was over four months later , sars had infected 29 countries worldwide and more than 1,000 people were dead . for all that the virus was rapidly contained , however , there was little that could be done about the alarming news reports carried by cable news channels and the internet . as bloggers added to the hysteria by spreading unfounded conspiracy theories , tourism in hong kong and other affected cities ground to a halt , costing businesses more than 10 billion u.s. dollars . one business , however , did very well . above all , sars was a reminder that pandemics have always been associated with panic . if history teaches us anything , it 's that while pandemics may start small , their impacts can be as dramatic as wars and natural disasters . the difference today is that science gives us the ability to detect pandemics right at the very beginning and to take action to mitigate their impacts before they spread too widely . ( music )
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but with the advent of the agricultural revolution 10,000 years ago , and the arrival of permanent settlements in the middle east , people began living side-by-side with animals , facilitating the spread of bacteria and viruses between cattle and humans . epidemics and pandemics come in many shapes and forms . in 2010 , for instance , a devastating earthquake struck haiti , forcing thousands of people into temporary refugee camps .
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why are epidemics and pandemics a relatively recent phenomenon in human history ?
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the most basic function of bodily fat is self-storage of food reserves . in prehistoric times , natural selection favored genotypes that could endure harsh conditions by stocking the most fat . with chronic malnutrition being the norm for most of human history , genetics evolved to favor fat storage . so when did body fat become problematic ? the negative impacts of being overweight were not even noted in medical literature until as late as the 18th century . then , technological advances coupled with public health measures resulted in the betterment of the quantity , quality , and variety of food . sustained abundance of good food enabled a healthier population to boom economically . output increased , and with it , leisure time and waistlines . by the mid 19th century , being excessively overweight , or obese , was recognized as a cause of ill health , and another century later , declared deadly . what is the distinction between being overweight and being obese ? a calculation called the bmi breaks it down for us . for example , if someone weighs 65 kilgorams and is 1.5 meters tall , they have a bmi of about 29 . obesity is a condition of excess body fat that occurs when a person 's bmi is above 30 , just over the overweight range of 25 to 29.9 . while bmi can be a helpful estimate of healthy weight , actual body fat percentage can only really be determined by also considering information like waist circumference and muscle mass . athletes , for instance , have a naturally higher bmi . so how does a person become obese ? at its most basic , obesity is caused by energy imbalance . if the energy input from calories is greater than the energy output from physical activity , the body stores the extra calories as fat . in most cases , this imbalance comes from a combination of circumstances and choices . adults should be getting at least 2.5 hours of exercise each week , and children a whole hour per day . but globally , one in four adults and eight out of ten adolescents are n't active enough . calorie-dense processed foods and growing portion sizes coupled with pervasive marketing lead to passive overeating . and scarce resources , and a lack of access to healthy , affordable foods creates an even greater risk in disadvantaged communities . yet , our genetic makeup also plays a part . studies on families and on separated twins have shown a clear causal hereditary relationship to weight gain . recent studies have also found a link between obesity and variations in the bacteria species that live in our digestive systems . no matter the cause , obesity is an escalating global epidemic . it substantially raises the probability of diseases , like diabetes , heart disease , stroke , high blood pressure , and cancer . it affects virtually all ages , genders , and socioeconomic groups in both developed and developing countries . with a 60 % rise in child obesity globally over just two decades , the problem is too significant to ignore . once a person is obese , the climb to recovery becomes progressively steeper . hormonal and metabolic changes reduce the body 's response to overeating . after losing weight , a formerly overweight person burns less calories doing the same exercises as a person who is naturally the same weight , making it much more difficult to shed the excess fat . and as people gain weight , damage to signaling pathways makes it increasingly difficult for the brain to measure food intake and fat storage . there is , however , some evidence that well-monitored , long-term changes in behavior can lead to improvements in obesity-related health issues . and weight loss from sustained lifestyle changes , or invasive treatments like bariatric surgery , can improve insulin resistance and decrease inflammation . what was once an advantage for survival is now working against us . as the world 's population continues to slow down and get bigger , moving and consciously eating our way towards a healthier weight is essential to our overall well-being . and with the epidemic affecting every country in the world for different socioeconomic reasons , obesity can not be seen as an isolated issue . more global measures for prevention are essential to manage the weight of the world .
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recent studies have also found a link between obesity and variations in the bacteria species that live in our digestive systems . no matter the cause , obesity is an escalating global epidemic . it substantially raises the probability of diseases , like diabetes , heart disease , stroke , high blood pressure , and cancer .
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describe the role that access to healthy food plays in the obesity epidemic , and why some populations might be at a disadvantage .
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what lights up the screen that you 're looking at right now ? trace back the battery chargers and power cords and you 'll end up at an electrical outlet , providing easy , safe access to reliable electricity . but beyond that outlet , the picture gets messier . it takes a lot of fuel to heat our homes , preserve our food , and our power our gadgets around the clock . and for 40 % of the world , that fuel is cheap , plentiful , and it 's called coal . but coal also releases pollutants into the air , like sulfur dioxide , nitrogen oxides , soot , and toxic metals , like mercury . these cause environmental damage , like acid rain , and serious health problems . in fact , in 1952 , coal burning caused such heavy smog in london that pedestrians could n't even see their feet , and thousands of people died from ill health . since then , many countries have deployed technology to remove most of these pollutants before they reach the air . but now we have a new air pollution problem on our hands , one that does n't show up in a cloud of dark smog , but in rising seas , floods , and heat waves . it 's global climate change , and again , the main culprit is coal . it 's responsible for 44 % of global carbon dioxide emissions , which trap the sun 's heat in the earth 's atmosphere , instead of letting it escape . so now the question is how do we remove that bad stuff as well ? that 's the idea behind cleaner coal . creating cleaner coal is really about trying to contain its ill effects with the help of special technologies that make the end product more acceptable . just like the most intriguing superheroes often have their own dark powers to overcome , so we can try and keep coal 's negative forces in check . but why do n't we just exterminate coal if it takes that much effort to clean it up ? simply , coal is extremely valuable to us , and it 's easy to come by . compressed underground for ages , coal holds chemical energy from plants that were fed from by the sun hundreds of millions of years ago , long before humans evolved . that makes coal energy dense , meaning it can be burned 'round the clock . it 's also cheap , if you ignore the pollution costs , and should last us through the end of the 21st century . we 've already got all the infrastructure in place for harnessing its power , and globally , although countries are making a move towards energy from cleaner and more renewable sources , there 's no sign yet that coal use is slowing down . in fact , as of 2012 , over 1000 new coal plants have been proposed , mostly in china and india . since for the time being coal is here to stay , experts say that if we want to reduce its emissions ' impact on the atmosphere , and slow down climate change , we 'll have to think of creative ways of reducing coal 's destructive power . to do that , we need to strip it of its foul forces , all that toxic carbon dioxide that causes havoc in the atmosphere . then , we need to store the co2 somewhere else . this mission is called carbon capture and sequestration , or ccs . and as if carbon dioxide were some evil genie we did n't want to escape , once it has been separated from coal , we 've devised ways to banish it underground . we can do this by injecting it deep into the earth , or by placing it deep under the ocean 's surface . stripping away coal 's negative elements can happen in three ways . first , and most commonly , as coal burns , the exhaust gas can be mixed with a compound called monoethanolamine . like a forceful power-stripping magnet , this compound bonds to the co2 , yanking it out of the gas stream so it can be stored separately underground . another method is to relieve coal of its co2 before it even has a chance to be released as exhaust . in this process , steam and oxygen swoop in to the rescue to convert coal into a special product called syngas , made up of carbon monoxide and hydrogen and some co2 . zap that with some water vapor , and the carbon monoxide gets converted into carbon dioxide , which can be isolated . the leftover hydrogen gas is then used as energy to generate electricity , so there 's an added bonus . a third technique exposes coal to pure oxygen , instead of burning it in air . this creates exhaust gas with higher concentrations of carbon dioxide , which makes it easy to isolate and to banish to the chasms below . all this can reduce emissions at a power plant by up to 90 % , but as with any superhero struggling with their destructive powers , it takes a lot of effort to switch over from the dark side . so these positive pollution-busting forces , although they 're available , have barely been used in commercial power plants because they cost a lot . but ultimately , the bigger problem is that in most parts of the world , it 's still too easy and much cheaper to keep emitting carbon dioxide , and that makes it tempting to completely ignore coal 's dark side . in this case , the most powerful force for good is regulation , the rules that can restrict the amount of carbon dioxide emitted from power plants , and make energy companies around the world wary of what they put into the air . until then , every time you turn on a screen or flick a light switch , coal is lurking in the background , carrying its dark powers with it wherever it goes .
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the leftover hydrogen gas is then used as energy to generate electricity , so there 's an added bonus . a third technique exposes coal to pure oxygen , instead of burning it in air . this creates exhaust gas with higher concentrations of carbon dioxide , which makes it easy to isolate and to banish to the chasms below .
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what features of coal and coal-burning make it responsible for such a large proportion of carbon dioxide emissions ?
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`` beauty is a curse , '' psyche thought as she looked over the cliff 's edge where she 'd been abandoned by her father . she 'd been born with the physical perfection so complete that she was worshipped as a new incarnation of venus , the goddess of love . but real-life human lovers were too intimidated even to approach her . when her father asked for guidance from the oracle of apollo , the god of light , reason , and prophecy . he was told to abandon his daughter on a rocky crag where she would marry a cruel and savage serpent-like winged evil . alone on the crag , psyche felt zephyr the west wind gently lifting her into the air . it set her down before a palace . `` you are home , '' she heard an unseen voice say . `` your husband awaits you in the bedroom , if you dare to meet him . '' she was brave enough , psyche told herself . the bedroom was so dark that she could n't see her husband . but he did n't feel serpent-like at all . his skin was soft , and his voice and manner were gentle . she asked him who he was , but he told her this was the one question he could never answer . if she loved him , she would not need to know . his visits continued night after night . before long , psyche was pregnant . she rejoiced , but was also conflicted . how could she raise her baby with a man she 'd never seen ? that night , psyche approached her sleeping husband holding an oil lamp . what she found was the god cupid who sent gods and humans lusting after each other with the pinpricks of his arrows . psyche dropped her lamp , burning cupid with hot oil . he said he 'd been in love with psyche ever since his jealous mother , venus , asked him to embarrass the young woman by pricking her with an arrow . but taken with psyche 's beauty , cupid used the arrow on himself . he did n't believe , however , that gods and humans could love as equals . now that she knew his true form , their hopes for happiness were dashed , so he flew away . psyche was left in despair until the unseen voice returned and told her that it was indeed possible for her and cupid to love each other as equals . encouraged , she set out to find him . but venus intercepted psyche and said she and cupid could only wed if she completed a series of impossible tasks . first , psyche was told to sort a huge , messy pile of seeds in a single night . just as she was abandoning hope , an ant colony took pity on her and helped with the work . successfully passing the first trial , psyche next had to bring venus the fleece of the golden sheep , who had a reputation for disemboweling stray adventurers , but a river god showed her how to collect the fleece the sheep had snagged on briars , and she succeeded . finally , psyche had to travel to the underworld and convince proserpina , queen of the dead , to put a drop of her beauty in a box for venus . once again , the unseen voice came to psyche 's aide . it told her to bring barley cakes for cerberus , the guard dog to the underworld and coins to pay the boatman , charon to ferry her across the river styx . with her third and final task complete , psyche returned to the land of the living . just outside venus 's palace , she opened the box of proserpina 's beauty , hoping to keep some for herself . but the box was filled with sleep , not beauty , and psyche collapsed in the road . cupid , now recovered from his wounds , flew to his sleeping bride . he told her he 'd been wrong and foolish . her fearlessness in the face of the unknown proved that she was more than his equal . cupid gave psyche amborsia , the nectar of the gods , making her immortal . shortly after , psyche bore their daughter . they named her pleasure , and she , cupid , and psyche , whose name means soul , have been complicating people 's love lives ever since .
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shortly after , psyche bore their daughter . they named her pleasure , and she , cupid , and psyche , whose name means soul , have been complicating people 's love lives ever since .
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cupid makes people fall in love with each other :
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so this is a sample of ruthenium sponge . so the ruthenium metal has been precipitated to form very fine particles . so here we will just open the box i am rather ashamed that i made a big mistake about the name of ruthenium . i thought it referred to somewhere in middle europe perhaps in czechoslovakia whereas ruthenium actually comes from ruthenia which is the latin translation for the country that is now called russia and , in fact , the element ruthenium was first discovered in russia in the city of kazan . why would that be a particular cause of shame for you ? well , because my father was born in russia and therefore to get something connected to russia wrong is a bit embarrassing . the ruthenium is a very , very reactive metal especially when it is formed in this very fine sponge type material . ruthenium was actually discovered relatively early in the middle of the 19th century . there is some discussion , whether in fact the swedish chemist berzelius analysed something that contained ruthenium and missed it or not , but i am not quite sure about that . but the reason why i am interested in this is because i did my doctorate with a supervisor and if you look at his supervisor and then that ö then go back one supervisor after another you eventually get to the swedish chemist berzelius who was my great , great , great , great , great , great , great supervisor and you will find that most of the chemists now working in the world were related to just a few pioneering chemists in the 18th century . so the ruthenium is very finely divided and if i tip it you can see in the bottom of the vial very fine powders but again because of the particle size this is really dark , very black , very nice sample of ruthenium very useful for catalytic chemistry . it is as a catalyst that ruthenium is particularly famous . ruthenium itself if you look at a lump of the metal is a kind of silvery colour . this is a sample of ruthenium as a catalyst . now because it is an expensive metal the ruthenium is just distributed as a very thin layer on silica . silica is like sand and you can see that this finely divided ruthenium looks black . they are very finely divided so it has a large surface area so the molecules can come in and react it . and my students were using this catalyst to react an organic compound , that is one with carbon and hydrogen and to get it to react with more hydrogen and so they lent me this catalyst so i could show it to you . there are other ruthenium catalysts which dissolve in the solution that you are trying to get the reaction to go . and there is a very famous catalyst named after the american chemist bob grubbs , who won the nobel prize about 4 years ago , and his catalyst does a reaction which most people even some chemists had not heard of called which is called metathesis in which double bonds between two carbon atoms are broken and joined together in a different way . and you can use this for all sorts of things you can make plastics out of oils ; you can make new sorts of wax ; you can make a really great sort of wax that has oxygen atoms in it ; and if you use this for candles then the oxygen atoms make fragrance molecules dissolve much better than in ordinary wax . so you can have a christmas candle which , when you light it , smells of christmas pudding or smells of alcohol or vanilla or whatever spice you want . you canít do that with an ordinary wax but this ruthenium catalyst opens up all sorts of things so that is why he got the nobel prize . he got the nobel prize because he made nice smelling candles ? no , he got the nobel prize because he invented the catalyst that opened up all sorts of reactions that otherwise could not be done . bob grubbs compound has ruthenium and his is the most widely used and it is now used in a whole series of industrial processes . this is another compound of ruthenium which you can see is a rather nice red colour and it has the rather unromantic name of ruthenium bpy three times or chemists who use it call it rubpy . and the point about this compound is that it absorbs light well and it is very stable , you can shine light on it , very intense light for a long time and the compound does not decompose , it does not change . but what it can do when you shine light is that you can move electrons around inside the compound and this compound and ones like it are being used by people to try and capture the light from the sun - capture solar energy
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bob grubbs compound has ruthenium and his is the most widely used and it is now used in a whole series of industrial processes . this is another compound of ruthenium which you can see is a rather nice red colour and it has the rather unromantic name of ruthenium bpy three times or chemists who use it call it rubpy . and the point about this compound is that it absorbs light well and it is very stable , you can shine light on it , very intense light for a long time and the compound does not decompose , it does not change .
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what is the abbreviated name of the red coordination complex that the professor calls tris ( bipyridine ) ruthenium ( ii ) dichloride ?
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so the last time we tried to film chlorine experiments we found that the chlorine cylinder itself had a slight problem , it was seized here . but the stig has acquired another cylinder of chlorine . so you know what this means , it means that we feel duty-bound to increase the intensity of our chlorine video and show you some chemistry with chlorine . chlorine is an element that many people have heard of . it ’ s a greenish-yellow gas which consists of , the gas consists of two chlorine atoms bonded together so it ’ s cl2 and it ’ s much heavier than air . incredibly reactive , incredibly poisonous , not a very nice compound at all . ok so neil is about to open the cylinder of chlorine to allow some of the chlorine gas to leak through the pipe into the , to the flask in the fume hood . chlorine sits in the right-hand side of the periodic table in the halogens in group , well , some people say seven , some people say seventeen . really what that says is that chlorine wants another electron to get that noble gas configuration and it will move heaven and earth to get that electron ! so during the first world war it was used as a chemical weapon . the gas could spread across the battlefields and when it came to the trenches , which were holes in the ground , it would fall into the trenches and fill them up . you can see the yellow colour against the white background on the paper , so now we ’ re starting to fill that flask with chlorine ; it ’ s quite dense , so it will stick to the bottom of the flask it ’ s not like a light gas like hydrogen or helium , it won ’ t come upwards . so now you can see the colour in that chlorine is really quite intense . it wasn ’ t a terribly good weapon because it could quite easily , if the wind changed direction , it could blow the gas back to the people who were letting it out . so we ’ ll just put a stopper in to contain the gas while we prepare the rest of the experiment . chlorine is quite corrosive , it reacts with water to make an acid , hcl , hydrochloric acid which can attack people ’ s lungs . the lungs generate fluid , they fill up with fluid and quickly the person drowns in their own fluid . it also corrodes things very easily so all the metal fittings on people ’ s battle dress , the brass buttons , brass buckles , all went green as well . but it ’ s not a terribly effective weapon but when people weren ’ t expecting any sort of chemical weapon it must have been terrifying . ok so we have a small amount of aluminium here which we put on the end of a wire . we ’ re gon na heat the aluminium in that flame and then we ’ re gon na put the hot aluminium into the flask of chlorine , then hopefully we ’ ll see , the chlorine will react with the aluminium and we ’ ll get very rapid formation of aluminium trichloride , alcl3 . the british army created whole regiments of gas soldiers who were all trained chemists , who were sent out to handle these cylinders of gas . and on the german side in the first world war , fritz haber , the inventor of the haber process to make ammonia became very keen on chemical weapons and he was the chief proponent . his wife was really furious about this and in fact shot herself with his revolver , killed herself , the day before he was due to go back to the front . and he , it was said that this was because she objected to his work on chemical weapons . though at the same time there were rumours that he was having an affair with another woman , so there may have been other factors at play as well . so , let ’ s heat up our aluminium . ok , so it ’ s nice and warm , all over . and then we ’ ll drop it or add it into the chlorine glass . now instantly we are seeing aluminium trichloride coming out of the top and reacting with moisture in the air . so now you can see the reaction is getting very intense and we are seeing a flame in the bottom . so the aluminium is being consumed as it ’ s reacting , oxidising strongly in that chlorine-rich air . chlorine is found all over the world , the sea contains sodium chloride , and there are huge deposits of sodium chloride in salt lakes where lakes have dried out , such as in some parts of the states , where you , united states , where you have salt lakes where people can race cars and things across the flat surface and in other parts of the world . all of the aluminium has been consumed now by the chlorine : a very , very rapid reaction . there are many areas , such as in the north of england , in the county of cheshire and also in salzburg in austria , where there are prehistoric deposits of salt from prehistoric salt lakes , which can now be mined really quite easily , and there , so salt and chlorine is a very common element . it ’ s made from sodium chloride solution by electrolysis , by passing an electric current , and it ’ s a very energy intensive process . one percent of the uk ’ s electricity was used , at one time , for making chlorine from sodium chloride , and the chlorine is used particularly for making the plastic pvc . while we got chlorine here , we thought we ’ d do a couple of reactions . so we ’ ve got some chlorine in this flask and you can see the nice yellow colour and i thought what we ’ d try and do now is do a competition reaction again or a reaction with iron . so now the iron , we ’ re gon na heat the iron , this is iron wool which you might use for treating wood , and we ’ re gon na heat that until it ’ s warm and put it in the chlorine , the chlorine will oxidise it to iron chloride . chlorine will react with all sorts of metals . you can make salt by burning the metal sodium in chlorine , and if you put in other metals like aluminium or iron they will also react . aluminium reacts to form aluminium trichloride which is the salt of aluminium and iron will similarly react to form iron chloride , and most metals but not all of them will react with chlorine : lead will not for example . but it is really quite a reactive gas . so really rapid reaction there as the hot iron starts to react with the chlorine to form iron chloride . very , very exothermic again and i think , yes this is very hot , we might have to move it off the paper . so what happens in all of these reactions is that the chlorine removes an electron from the metal to make the chloride ion cl- , and the chloride ion is perfectly innocuous , you can drink , you can eat chloride , whereas chlorine itself is very poisonous . oh it ’ s warm , it ’ s not too hot to touch its like picking up a mug of warm tea or warm coffee . but you can see again the products of the chemical reaction have precipitated out across the flask , and now if i remove the…wire again i can see that all of the iron has been consumed again instantly . the moment that it got into that chlorine-rich flask ; very , very rapid reaction , very , very reactive with chlorine .
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so now the iron , we ’ re gon na heat the iron , this is iron wool which you might use for treating wood , and we ’ re gon na heat that until it ’ s warm and put it in the chlorine , the chlorine will oxidise it to iron chloride . chlorine will react with all sorts of metals . you can make salt by burning the metal sodium in chlorine , and if you put in other metals like aluminium or iron they will also react .
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chlorine reacts with almost all metals , but according to the professor , which one does not react with chlorine ?
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on august 21 , 2017 the shadow of the moon will pass from the west coast to the east coast of the u.s. our blue sky will turn black as night and fill with stars , and there will be a hole in the sky where the sun used to be , surrounded by the fiery ring of the sun 's corona , a total eclipse of the sun . this will truly be a historic event . accounts of solar eclipses date way back on the written record . the early mesopotamians wrote that the sun was put to shame during the solar eclipse of the 14th century b.c.e . and it may have started the sun worship of the egyptian pharaoh akhenaten . ancient chinese astrologers paid with their lives if they failed to predict the solar eclipse and portend the fate of their emperors whose symbol was the sun . the earliest date of a specific event in human history , a battle between the armies of lydia and media , occurred on may 28 , 535 b.c.e . when a solar eclipse caused the soldiers to lay down their arms and declare a truce . so how does it happen ? during a total solar eclipse , the moon moves between the earth and the sun . when this happens , the disc of the moon appears to perfectly cover the disc of the sun even though the sun is much larger than the moon . but how is this possible ? the sun is 400 times bigger than the moon , but by sheer coincidence , the moon is 390 times closer to earth . size and distance cancel each other out so that the moon and sun appear to be almost the exactly same size . every time the moon orbits the earth , once every 27.3 days , it has to pass between the earth and the sun , a stage called the new moon phase . and every time it passes , the new moon has a chance to block out the sun . most of the time , the moon passes a little above or a little below the sun , but if they align perfectly , the shadow of the moon will make a narrow path across earth and those in the shadows will see a total solar eclipse . just like on night side of the earth , the sky during a total eclipse is black and filled with stars . but while the moon perfectly covers the surface of the sun , it does n't block out the sun 's outer atmosphere , its corona , which appears as a fiery ring around the dark disc of the moon . solar eclipses occur several times a year , but most often they are partial eclipses where the moon does n't quite line up with the sun . and , when the moon and sun are perfectly aligned , the moon is usually too far from earth in its orbit to completely cover the sun , creating an annular eclipse . during an annular or partial eclipse , the sky remains bright . even on those rare occasions of a total eclipse , the moon 's shadow is most likely to fall on the 70 % of earth that is covered by water , and few people , if any , will see it . the eclipse of 2017 will be remarkable on a larger scale because the moon is slowly moving away from earth . if a furry ancestor of ours had bothered to look up during a solar eclipse a hundred million years ago , it would n't have seen the fiery corona of the sun . it would have just been dark . eventually , the moon will have moved too far from earth to completely cover the disc of the sun . it is only during our little wink of earth 's history that the moon is at just the right distance to cause a total solar eclipse yet not block the sun 's corona . so on august 21 , 2017 , when the moon exactly lines up with the sun and the moon is close enough to the earth , its shadow will cross the u.s. and , if you happen to be in its narrow path , you will witness one of the most awe-inspiring sights in the universe . but , as incredible as this event will be , total eclipses are one of the most dangerous as well . only specially tinted filters , specifically designed to observe the sun , should be used . the eclipse might put the sun to shame , but even a shamed sun can seriously damage your eyes .
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during an annular or partial eclipse , the sky remains bright . even on those rare occasions of a total eclipse , the moon 's shadow is most likely to fall on the 70 % of earth that is covered by water , and few people , if any , will see it . the eclipse of 2017 will be remarkable on a larger scale because the moon is slowly moving away from earth .
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the width of your pinky finger held at arms length will appear to be about twice the width of the full moon . how can this be true for people with very large pinky fingers and for people with very small pinky fingers ? ( if it helps , draw a diagram to help you answer the question )
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when a team of archaeologists recently came across some 15,000 year-old human remains , they made an interesting discovery . the teeth of those ancient humans were riddled with holes . their cavities were caused by the same thing that still plagues us today , specific tiny microbes that live in our mouths . these microbes are with us soon after birth . we typically pick them up as babies from our mothers ' mouths . and as our teeth erupt , they naturally begin to accumulate communities of bacteria . depending on what we eat , and specifically how much sugar we consume , certain microbes can overpopulate and cause cavities . diets high in sugary foods cause an explosion of bacteria called mutans streptococci in our mouths . like humans , these microorganisms love sugar , using it as a molecular building block and energy source . as they consume it , the bacteria generate byproducts in the form of acids , such as lactic acid . mutans streptococci are resistant to this acid , but unfortunately , our teeth are n't . while each human tooth is coated in a hardy , protective layer of enamel , it 's no match for acid . that degrades the armor over time , leaching away its calcium minerals . gradually , acid wears down a pathway for bacteria into the tooth 's secondary layer called the dentin . since blood vessels and nerves in our teeth are enclosed deep within , at this stage , the expanding cavity does n't hurt . but if the damage extends beyond the dentin , the bacterial invasion progresses causing excruciating pain as the nerves become exposed . without treatment , the whole tooth may become infected and require removal all due to those sugar-loving bacteria . the more sugar our food contains , the more our teeth are put at risk . those cavemen would hardly have indulged in sugary treats , however , so what caused their cavities ? in meat-heavy diets , there would have been a low-risk of cavities developing because lean meat contains very little sugar , but that 's not all our early human ancestors ate . cavemen would also have consumed root vegetables , nuts , and grains , all of which contain carbohydrates . when exposed to enzymes in the saliva , carbohydrates get broken down into simpler sugars , which can become the fodder for those ravenous mouth bacteria . so while ancient humans did eat less sugar compared to us , their teeth were still exposed to sugars . that does n't mean they were unable to treat their cavities , though . archaeological remains show that about 14,000 years ago , humans were already using sharpened flint to remove bits of rotten teeth . ancient humans even made rudimentary drills to smooth out the rough holes left behind and beeswax to plug cavities , like modern-day fillings . today , we have much more sophisticated techniques and tools , which is fortunate because we also need to contend with our more damaging , sugar-guzzling ways . after the industrial revolution , the human incidence of cavities surged because suddenly we had technological advances that made refined sugar cheaper and accessible . today , an incredible 92 % of american adults have had cavities in their teeth . some people are more susceptible to cavities due to genes that may cause certain weaknesses , like softer enamel , but for most , high sugar consumption is to blame . however , we have developed other ways of minimizing cavities besides reducing our intake of sugar and starch . in most toothpastes and many water supplies , we use tiny amounts of fluoride . that strengthens teeth and encourages the growth of enamel crystals that build up a tooth 's defenses against acid . when cavities do develop , we use tooth fillings to fill and close off the infected area , preventing them from getting worse . the best way to avoid a cavity is still cutting down on sugar intake and practicing good oral hygiene to get rid of the bacteria and their food sources . that includes regular tooth brushing , flossing , and avoiding sugary , starchy , and sticky foods that cling to your teeth between meals . gradually , the population of sugar-loving microbes in your mouth will decline . unlike the cavemen of yesteryear , today we have the knowledge required to avert a cavity calamity . we just need to use it .
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without treatment , the whole tooth may become infected and require removal all due to those sugar-loving bacteria . the more sugar our food contains , the more our teeth are put at risk . those cavemen would hardly have indulged in sugary treats , however , so what caused their cavities ?
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which food type contains very little sugar ?
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translator : tom carter reviewer : bedirhan cinar the periodic table is instantly recognizable . it 's not just in every chemistry lab worldwide , it 's found on t-shirts , coffee mugs , and shower curtains . but the periodic table is n't just another trendy icon . it 's a massive slab of human genius , up there with the taj mahal , the mona lisa , and the ice cream sandwich -- and the table 's creator , dmitri mendeleev , is a bonafide science hall-of-famer . but why ? what 's so great about him and his table ? is it because he made a comprehensive list of the known elements ? nah , you do n't earn a spot in science valhalla just for making a list . besides , mendeleev was far from the first person to do that . is it because mendeleev arranged elements with similar properties together ? not really , that had already been done too . so what was mendeleev 's genius ? let 's look at one of the first versions of the periodic table from around 1870 . here we see elements designated by their two-letter symbols arranged in a table . check out the entry of the third column , fifth row . there 's a dash there . from that unassuming placeholder springs the raw brilliance of mendeleev . that dash is science . by putting that dash there , dmitri was making a bold statement . he said -- and i 'm paraphrasing here -- y'all have n't discovered this element yet . in the meantime , i 'm going to give it a name . it 's one step away from aluminum , so we 'll call it eka-aluminum , `` eka '' being sanskrit for one . nobody 's found eka-aluminum yet , so we do n't know anything about it , right ? wrong ! based on where it 's located , i can tell you all about it . first of all , an atom of eka-aluminum has an atomic weight of 68 , about 68 times heavier than a hydrogen atom . when eka-aluminum is isolated , you 'll see it 's a solid metal at room temperature . it 's shiny , it conducts heat really well , it can be flattened into a sheet , stretched into a wire , but its melting point is low . like , freakishly low . oh , and a cubic centimeter of it will weigh six grams . mendeleev could predict all of these things simply from where the blank spot was , and his understanding of how the elements surrounding it behave . a few years after this prediction , a french guy named paul emile lecoq de boisbaudran discovered a new element in ore samples and named it gallium after gaul , the historical name for france . gallium is one step away from aluminum on the periodic table . it 's eka-aluminum . so were mendeleev 's predictions right ? gallium 's atomic weight is 69.72 . a cubic centimeter of it weighs 5.9 grams . it 's a solid metal at room temperature , but it melts at a paltry 30 degrees celcius , 85 degrees fahrenheit . it melts in your mouth and in your hand . not only did mendeleev completely nail gallium , he predicted other elements that were unknown at the time : scandium , germanium , rhenium . the element he called eka-manganese is now called technetium . technetium is so rare it could n't be isolated until it was synthesized in a cyclotron in 1937 , almost 70 years after dmitri predicted its existence , 30 years after he died . dmitri died without a nobel prize in 1907 , but he wound up receiving a much more exclusive honor . in 1955 , scientists at uc berkeley successfully created 17 atoms of a previously undiscovered element . this element filled an empty spot in the perodic table at number 101 , and was officially named mendelevium in 1963 . there have been well over 800 nobel prize winners , but only 15 scientists have an element named after them . so the next time you stare at a periodic table , whether it 's on the wall of a university classroom or on a five-dollar coffee mug , dmitri mendeleev , the architect of the periodic table , will be staring back .
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not really , that had already been done too . so what was mendeleev 's genius ? let 's look at one of the first versions of the periodic table from around 1870 .
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what did dmitri mendeleev do that set him apart ?
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translator : andrea mcdonough reviewer : bedirhan cinar you believe that the sun is much larger than the earth , that the earth is a roughly spherical planet that rotates on its axis every 24 hours and it revolves around the sun once every 365 days . you believe that you were born on a particular date , that you were born to two human parents and that each of your human parents was born on an earlier date . you believe that other human beings have thoughts and feelings like you do and that you are not surrounded by humanoid robots . you believe all of these things and many more , not on the basis of direct observation , which ca n't , by itself , tell you very much about the relative size and motion of the sun and the earth , or about your own family history , or about what goes on in the minds of other humans . instead , these beliefs are mostly based on what you 've been told . without spoken and written testimonies , human beings could not pass on knowledge from one person to another , let alone from one generation to another . we would know much , much less about the world around us . so learning about a topic by asking an expert on that topic , or appealing to authority , helps us gain knowledge , but , it does n't always . even the most highly respected authorities can turn out to be wrong . occasionally this happens because a highly respected authority is dishonest and claims to know something that she or he really does n't know . sometimes it happens just because they make a mistake . they think they know when they do n't know . for example , a number of respected economists did not expect the financial collapse of 2008 . they turned out to be wrong . maybe they were wrong because they were overlooking some important evidence . maybe they were wrong because they were misinterpreting some of the evidence they had noticed . or maybe they were wrong simply because they were reasoning carelessly from the total body of their evidence . but whatever the reason , they turned out to be wrong and many people who trusted their authority ended up losing lots of money , losing lots of other people 's money , on account of that misplaced trust . so while appealing to authority can sometimes provide us with valuable knowledge , it also can sometimes be the cause of monumental errors . it 's important to all of us to be able to distinguish those occasions on which we can safely and reasonably trust authority from those occasions on which we ca n't . but how do we do that ? in order to do that , nothing is more useful than an authority 's track record on a particular topic . if someone turns out to perform well in a given situation much of the time , then it 's likely that he or she will continue to perform well in that same situation , at least in the near term . and this generalization holds true of the testimony of authorities as much as of anything else . if someone can consistently pick winners in both politics and baseball , then we should probably trust him or her to keep on picking winners in both politics or baseball , though maybe not in other things where his or her track record may be less stellar . if other forecasters have a poorer track record on those same two topics , then we should n't trust them as much . so whenever you 're considering whether to trust the testimony of some authority , the first question to ask yourself is , `` what 's their track record on this topic ? '' and notice that you can apply the very same lesson to yourself . your instincts tell you that you 've just met mr . right , but what sort of track record do your instincts have on topics like this one ? have your instincts proven themselves to be worthy of your trust ? just as we judge other people 's testimony by their track record , so , too , we can judge our own instincts by their track record . and this brings us one step closer to an objective view of ourselves and our relation to the world around us .
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occasionally this happens because a highly respected authority is dishonest and claims to know something that she or he really does n't know . sometimes it happens just because they make a mistake . they think they know when they do n't know .
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you are deciding whether or not to marry hugo . although you love many things about hugo , there are other things that you don ’ t like ( e.g . hugo can sometimes make insensitive jokes , and he sometimes acts inappropriately around your family ) , and you doubt that those things can be changed . how would you go about making your decision ? would you ask others for advice ? why or why not ?
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the year was 1816 . europe and north america had just been through a devastating series of wars , and a slow recovery seemed to be underway , but nature had other plans . after two years of poor harvests , the spring brought heavy rains and cold , flooding the rivers and causing crop failures from the british isles to switzerland . while odd-colored snow fell in italy and hungary , famine , food riots and disease epidemics ensued . meanwhile , new england was blanketed by a strange fog that would not disperse as the ground remained frozen well into june . in what came to be known as `` the year without a summer , '' some thought the apocalypse had begun . a mood captured in lord byron 's poem `` darkness '' : `` i had a dream which was not all a dream . the bright sun was extinguish 'd , and the stars did wander darkling in the eternal space , rayless , and pathless , and the icy earth swung blind and blackening in the moonless air ; morn came and went -- and came , and brought no day . '' they had no way of knowing that the real source of their misfortunes had occurred a year ago thousands of miles away . the 1815 eruption of mount tambora on the indonesian island of sumbawa was what is known as a supervolcano , characterized by a volume of erupted material , many times greater than that of ordinary volcanoes . and while the popular image of volcanic destruction is molten rock engulfing the surrounding land , far greater devastation is caused by what remains in the air . volcanic ash , dispersed by wind , can blanket the sky for days , while toxic gases , such as sulfur dioxide , react in the stratosphere , blocking out solar radiation and drastically cooling the atmosphere below . the resulting volcanic winter , along with other effects such as acid rain , can effect multiple continents , disrupting natural cycles and annihilating the plant life on which other organisms , including humans , depend . releasing nearly 160 cubic kilometers of rock , ash and gas , the mount tambora eruption was the largest in recorded history , causing as many as 90,000 deaths . but previous eruptions have been even more deadly . the 1600 eruption of peru 's huaynaputina is likely to have triggered the russian famine , that killed nearly two million , while more ancient eruptions have been blamed for major world events , such as the fall of the chinese xia dynasty , the disappearance of the minoan civilization , and even a genetic bottleneck in human evolution that may have resulted from all but a few thousand human beings being wiped out 70,000 years ago . one of the most dangerous types of supervolcano is an explosive caldera , formed when a volcanic mountain collapses after an eruption so large that the now-empty magma chamber can no longer support its weight . but though the above-ground volcano is gone , the underground volcanic activity continues . with no method of release , magma and volcanic gases continue to accumulate and expand underground , building up pressure until a massive and violent explosion becomes inevitable . and one of the largest active volcanic calderas lies right under yellowstone national park . the last time it erupted , 650,000 years ago , it covered much of north america in nearly two meters of ash and rock . scientists are currently monitoring the world 's active volcanoes , and procedures for predicting eruptions , conducting evacuations and diverting lava flows have improved over the years . but the massive scale and global reach of a supervolcano means that for many people there would be nowhere to run . fortunately , the current data shows no evidence of such an eruption occurring in the next few thousand years . but the idea of a sudden and unavoidable civilization-destroying apocalypse caused by events half a globe away will remain a powerful and terrifying vision . less fictional than we would like to believe . `` the winds were withered in the stagnant air , and the clouds perish 'd ; darkness had no need of aid from them -- she was the universe . '' - lord byron
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scientists are currently monitoring the world 's active volcanoes , and procedures for predicting eruptions , conducting evacuations and diverting lava flows have improved over the years . but the massive scale and global reach of a supervolcano means that for many people there would be nowhere to run . fortunately , the current data shows no evidence of such an eruption occurring in the next few thousand years .
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which of the following strategies would avoid all of the devastating effects of a supervolcano ?
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sunscreen comes in many forms , each with its own impacts on your body and the environment . with so many options , how do you choose which sunscreen is best for you ? to answer that question , we first have to understand how sunscreens work . sunlight is composed of electromagnetic waves and is our primary source of ultraviolet radiation , which has a shorter wavelength than visible light and carries more energy . uva , uvb , and uvc are classified according to their wavelengths . short wavelength uvc never reaches the earth 's surface , but uvb and uva do . medium wavelength uvb rays can enter the skin 's superficial layers and long length uva rays can penetrate into the deeper layers . uvb in small amounts actually helps us make vitamin d , which enables our bodies to build and maintain strong bones . however , prolonged exposure to uva and uvb can damage dna , age your skin , and promote the development of potentially deadly skin cancer . sunscreen protects your skin either physically by deflecting uv rays with an inorganic blocker like zinc oxide or titanium dioxide , or chemically by using carbon-based compounds to absorb uv photons that are then harmlessly dissipated as heat . so , what differentiates one sunscreen from another ? when we choose a sunscreen , we can compare application method , the spf , and the active ingredients . sprays can be convenient to put on , especially when you 're wet , but a recent study found that most people do n't apply a thick enough layer to get full protection . and the possible health risks of inhaling sunscreen compounds from a spray cloud might make you consider reaching for that bottle of lotion instead . opt for a sunscreen with an spf of at least 15 , although 30 is better . spf is a nonlinear scale of how much uvb radiation is needed to give protected skin a sunburn . spf 15 does a pretty good job by blocking 93 % of uvb rays . you get a slight increase as spf goes up , with spf 30 blocking 97 % , and 50 blocking 98 % . spf is based on the quantity of solar exposure . so how much time you have before you start to burn really depends on a long list of factors , including your genetics , and when , where , and how you spend your time in the sun . even though us marketed sunscreens have been deemed safe by the fda , scientists are still researching the effects of many active ingredients on the human body . so if you 're worried about potential irritants , look for mineral-based formulas with zinc oxide or titanium dioxide . even though they may go on a bit thick at first , they 're less irritating than carbon-based chemical sunscreens . these mineral-based sunscreens are preferential for the environment , too . if you plan on catching rays while splashing in a river or the ocean , keep in mind that carbon-based chemical sunscreens can harm marine life . take coral reefs , for example . although they cover less than 1 % of the earth 's underwater surface , they 're home to nearly 25 % of all fish species , making them the most diverse and productive marine ecosystems . research shows that carbon-based chemical sunscreen ingredients , like oxybenzone , butylparaben , octinoxate , and 4mbc contribute to a stress condition called coral bleaching in corals , which are living creatures . exposure to these organic compounds results in the death of the coral 's symbiotic algae . in addition to providing a reliable food source , these algae give coral their brilliant rainbow of colors . without them , corals turn a bleached white and are susceptible to disease and possibly death . and once the coral dies , the entire reef ecosystem is not far behind . so you 're now ready to make an informed choice when picking out your next sunscreen . spf is clearly labeled on the front . on the back under `` active ingredients , '' you can find whether zinc oxide , titanium dioxide , and those coral-harming components are present . taking a bit more time to check can be well worth it for both you and the environment .
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so , what differentiates one sunscreen from another ? when we choose a sunscreen , we can compare application method , the spf , and the active ingredients . sprays can be convenient to put on , especially when you 're wet , but a recent study found that most people do n't apply a thick enough layer to get full protection .
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between spray and lotions , based on recent studies , which is a better application method ?
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translator : andrea mcdonough reviewer : bedirhan cinar blue whales are the largest animals that have ever roamed the planet . they 're at least two times as big as the biggest dinosaurs , `` that 's big ! '' the length of a basketball court , and as heavy as 40 african elephants . if that 's not enough to make you marvel , here 's something that will . they 're grown to this enormous size by feeding exclusively on tiny shrimp-like creatures called krill that are no bigger than your little finger . in many ways , the sheer size of krill seems to have driven the evolution of the blue whale . see , krill are so small but are found in dense patches . for increased efficiency , blue whales have evolved to use a feeding strategy called lunge feeding . basically , the whale accelerates towards a prey patch and opens its mouth wide . to increase the capacity , its mouth expands . the special , accordion-like blubber layer that extends from its snout to its belly button enables the whale to engulf large quantities of prey-laden water . with each giant gulp , the whale takes in 125 % of its body weight in water and krill . the whale must then expel the water while retaining the yummy krill . to do this , it uses its baleen , the comb-like structure made of the same stuff our nails and hair are made of , and its tongue . it 's pretty crazy that the blue whale 's heart is as big as a small car , a child could crawl through its arteries , its tongue weighs as much as an elephant , but its esophagus is so small , the whale could choke on a loaf of bread . these whales are really not designed to feed on anything larger than krill . it 's estimated that blue whales eat four tons of krill per day . because of the incredible design , each dive provides the blue whale with 90 times as much energy as is used . every mouthful of krill provides almost 480,000 calories , the same amount you get from eating 1,900 hamburgers . but , why are blue whales so big ? blue whales are considerably larger than the largest living land animal , the elephant . the heavier an animal is , the greater its relative surface area . as weight increases , there 's a point at which the legs of that animal would simply collapse . that explains why elephants do n't stand on the delicate legs of a horse . they need legs shaped like stout pedestals to hold their bodies up against gravity . in water , the situation is quite different . buoyancy counteracts the gravitational pull on the body and their great bulk is therefore partially supported by the water . so , the ocean is a great place for species that want to grow bigger . the other secret to their size is their diet . by evolving such a huge mouth , the whale 's have specialized to catch enormous quantities of highly abundant and nutritious prey , which provides the energy needed to grow so big . but , now maybe you 're wondering why blue whales are n't any bigger ? after all , the ocean sounds like nirvana for any growing beast . well , while lunge feeding may have allowed blue whales to become the biggest animal to have ever roamed the planet , by enabling them to feed efficiently in dense prey patches , it is n't cost free . scientists compared all the costs involved with lunge feeding to the energy gained from the krill they eat . what they found is that when the whale 's body increases in size , the energy that body demands rises faster than the extra energy they get from their food . feeding whales needs 15 times the energy required to remain still and 5 times more energy than used when swimming . calculations show that the largest a lunge feeder can grow is 33 meters , pretty much blue whale size . turns out blue whales have a lot to thank krill for : neat , evolutionary adaptations that would not have been possible if krill were not so small . it 's incredible that these tiny creatures have allowed blue whales to really push the limits of size on our planet . makes you wonder if that old adage , `` you are what you eat , '' really does apply in blue whale world .
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translator : andrea mcdonough reviewer : bedirhan cinar blue whales are the largest animals that have ever roamed the planet . they 're at least two times as big as the biggest dinosaurs , `` that 's big ! '' the length of a basketball court , and as heavy as 40 african elephants .
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blue whales are the largest animals to have ever lived on the planet . they are at least ________ the biggest dinosaurs .
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for some , it 's a serious sport . for others , just a way to let loose . but despite its casual association with fun and sun , surfing has a richer and deeper history than many realize . what we today call surfing originated in the polynesian islands of the pacific ocean . we know from various accounts that wave riding was done throughout the polynesian pacific , as well as in west africa and peru . but it was in the hawaiian archipelago in particular that surfing advanced the most , was best documented , and , unlike elsewhere in polynesia , persisted . and for the people of hawaii , wave sliding was not just a recreational activity , but one with spiritual and social significance . like much of hawaiian society , nearly every aspect of surfing was governed by a code of rules and taboos known as kapu . hawaiians made offerings when selecting a tree to carve , prayed for waves with the help of a kahuna , or an expert priest , and gave thanks after surviving a perilous wipeout . certain surf breaks were strickly reserved for the elite . but it was n't just a solemn affair . surfers competed and wagered on who could ride the farthest , the fastest , or catch the biggest wave with superior skill , granting respect , social status , and romantic success . though it was later called the sport of kings , hawaiian men and women of all ages and social classes participated , riding surfboards shaped from koa , breadfruit , or wiliwili trees . many hawaiians road alaia boards , which were thin , midsized , and somewhat resemble today 's shortboards . some mounted paipo boards , short , round-nosed boards on which riders typically lay on their stomachs . but only chieftains could ride the massive olo boards , twice as long as today 's longboards . unlike most modern surfboards , all boards were finless , requiring surfers to drag their hands or feet to turn . we do n't know exactly when wave sliding was invented , but we know that it had already been practiced in polynesia for centuries by the time it was described in 1777 by william anderson , a surgeon on captain cook 's ship `` resolution . '' although anderson was in awe , most of the american christian missionaries who arrived in hawaii several decades later regarded surfing as sinful , and they discouraged it , along with other aspects of native culture . the biggest threat to surfing , however , was the threat to the natives themselves . by 1890 , new illnesses introduced by europeans and americans had decimated the hawaiian people , leaving fewer than 40,000 from a pre-contact population that may have exceeded 800,000 . at the same time , foreign influence grew with white settlers overthrowing the native monarchy in 1893 , and the u.s. annexing the islands five years later . the end of hawaii 's independence coincided with surfing 's native-led revival , a revival soon exploited by the american colonizers . but first , some hawaiians took surfing overseas . in 1907 , george freeth , the so-called hawaiian wonder , traveled to the west coast and gave surfing demonstrations in southern california . then in 1914 , olympic swimmer duke kahanamoku made his way to australia and new zealand , gliding across the southern pacific waves and attracting rapt audiences wherever he went . shortly before freeth went to california , a south carolinian named alexander hume ford moved to hawaii . after learning to surf , he became a champion of the pastime . but ford may have had unsavory reasons for his enthusiastic efforts to boost the sport . like many settlers , he wanted hawaii to become a u.s. state but was worried about its non-white majority of natives and asian workers . ford thus promoted surfing to attract white americans to hawaii , first as tourists , then as residents . he was helped by numerous writers and filmmakers . ford 's demographic plan would fail miserably . hawaii became a state in 1959 and remains the most racially diverse state in the country . but the promotion of surfing was a far greater success . today , surfing is a multi-billion dollar global industry , with tens of millions of enthusiasts worldwide . and though relatively few of these surfers are aware of the once-crucial wave chants or board carving rituals , hawaiians continue to preserve these traditions nearly washed away by history 's waves .
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in 1907 , george freeth , the so-called hawaiian wonder , traveled to the west coast and gave surfing demonstrations in southern california . then in 1914 , olympic swimmer duke kahanamoku made his way to australia and new zealand , gliding across the southern pacific waves and attracting rapt audiences wherever he went . shortly before freeth went to california , a south carolinian named alexander hume ford moved to hawaii .
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duke kahanamoku helped to spread surf culture after making his way to _____________ in 1914 .
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grammatical tense is how languages talk about time without explicitly naming time periods by , instead , modifying verbs to specify when action occurs . so how many different tenses are there in a language like english ? at first , the answer seems obvious : there 's past , present , and future . but thanks to something called grammatical aspect , each of those time periods actually divides further . there are four kinds of aspect . in the continuous or progressive aspect , the actions are still happening at the time of reference . the perfect aspect describes actions that are finished . the perfect progressive aspect is a combination , describing a completed part of a continuous action . and finally , there 's the simple aspect , the basic form of the past , present , and future tense where an action is not specified as continuous or discreet . that 's all a little hard to follow , so let 's see how it works in action . let 's say your friends tell you they went on a secret naval mission to collect evidence of a mysterious sea creature . the tense sets the overall frame of reference in the past , but within that , there are many options . your friends might say a creature attacked their boat , that 's the past simple , the most general aspect , which gives no further clarification . they were sleeping when it happened , a continuous process underway at that point . they might also tell you they had departed from nantucket to describe an action completed even earlier . that 's an example of the past perfect . or that they had been sailing for three weeks , something that was ongoing up until that point . in the present , they tell you that they still search for the creature today , their present simple activity . perhaps they are preparing for their next mission continuously as they speak . and they have built a special submarine for it , a completed achievement . plus , if they have been researching possible sightings of the creature , it 's something they 've been doing for a while and are still doing now making it present perfect progressive . so what does this next mission hold ? you know it still has n't happened because they will depart next week , the future simple . your friends will be searching for the elusive creature , an extended continuous undertaking . they tell you the submarine will have reached uncharted depths a month from now . that 's a confident prediction about what will be achieved by a specific point in the future , a point at which they will have been voyaging for three weeks in the future perfect progressive . the key insight to all these different tenses is that each sentence takes place in a specific moment , whether it 's past , present , or future . the point of aspects is that they tell you as of that moment the status of the action . in total , they give us twelve possibilities in english . what about other languages ? some , like french , swahili , and russian take a similar approach to english . others describe and divide time differently . some have fewer grammatical tenses , like japanese , which only distinguishes past from non-past , buli and tukang basi , which only distinguish future from non-future , and mandarin chinese with no verb tenses at all , only aspect . on the other hand , languages like yagwa split past tense into multiple degrees , like whether something happened hours , weeks , or years ago . in others , tenses are intertwined with moods that can convey urgency , necessity , or probability of events . this makes translation difficult but not impossible . speakers of most languages without certain tenses can express the same ideas with auxiliary words , like would or did , or by specifying the time they mean . are the variations from language to language just differents ways of describing the same fundamental reality ? or do their diverse structures reflect different ways of thinking about the world and even time itself ? and if so , what other ways of conceiving time may be out there ?
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grammatical tense is how languages talk about time without explicitly naming time periods by , instead , modifying verbs to specify when action occurs . so how many different tenses are there in a language like english ? at first , the answer seems obvious : there 's past , present , and future .
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how many tense-aspect forms are there in english ?
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85 % of the matter in our universe is a mystery . we do n't know what it 's made of , which is why we call it dark matter . but we know it 's out there because we can observe its gravitational attraction on galaxies and other celestial objects . we 've yet to directly observe dark matter , but scientists theorize that we may actually be able to create it in the most powerful particle collider in the world . that 's the 27 kilometer-long large hadron collider , or lhc , in geneva , switzerland . so how would that work ? in the lhc , two proton beams move in opposite directions and are accelerated to near the speed of light . at four collision points , the beams cross and protons smash into each other . protons are made of much smaller components called quarks and gluons in most ordinary collisions , the two protons pass through each other without any significant outcome . however , in about one in a million collisions , two components hit each other so violently , that most of the collision energy is set free producing thousands of new particles . it 's only in these collisions that very massive particles , like the theorized dark matter , can be produced . the collision points are surrounded by detectors containing about 100 million sensors . like huge three-dimensional cameras , they gather information on those new particles , including their trajectory , electrical charge , and energy . once processed , the computers can depict a collision as an image . each line is the path of a different particle , and different types of particles are color-coded . data from the detectors allows scientists to determine what each of these particles is , things like photons and electrons . now , the detectors take snapshots of about a billion of these collisions per second to find signs of extremely rare massive particles . to add to the difficulty , the particles we 're looking for may be unstable and decay into more familiar particles before reaching the sensors . take , for example , the higgs boson , a long-theorized particle that was n't observed until 2012 . the odds of a given collision producing a higgs boson are about one in 10 billion , and it only lasts for a tiny fraction of a second before decaying . but scientists developed theoretical models to tell them what to look for . for the higgs , they thought it would sometimes decay into two photons . so they first examined only the high-energy events that included two photons . but there 's a problem here . there are innumerable particle interactions that can produce two random photons . so how do you separate out the higgs from everything else ? the answer is mass . the information gathered by the detectors allows the scientists to go a step back and determine the mass of whatever it was that produced two photons . they put that mass value into a graph and then repeat the process for all events with two photons . the vast majority of these events are just random photon observations , what scientists call background events . but when a higgs boson is produced and decays into two photons , the mass always comes out to be the same . therefore , the tell-tale sign of the higgs boson would be a little bump sitting on top of the background . it takes billions of observations before a bump like this can appear , and it 's only considered a meaningful result if that bump becomes significantly higher than the background . in the case of the higgs boson , the scientists at the lhc announced their groundbreaking result when there was only a one in 3 million chance this bump could have appeared by a statistical fluke . so back to the dark matter . if the lhc 's proton beams have enough energy to produce it , that 's probably an even rarer occurrence than the higgs boson . so it takes quadrillions of collisions combined with theoretical models to even start to look . that 's what the lhc is currently doing . by generating a mountain of data , we 're hoping to find more tiny bumps in graphs that will provide evidence for yet unknown particles , like dark matter . or maybe what we 'll find wo n't be dark matter , but something else that would reshape our understanding of how the universe works entirely . that 's part of the fun at this point . we have no idea what we 're going to find .
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but scientists developed theoretical models to tell them what to look for . for the higgs , they thought it would sometimes decay into two photons . so they first examined only the high-energy events that included two photons .
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the higgs boson was discovered by detecting its decay into :
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the heisenberg uncertainty principle is one of a handful of ideas from quantum physics to expand into general pop culture . it says that you can never simultaneously know the exact position and the exact speed of an object and shows up as a metaphor in everything from literary criticism to sports commentary . uncertainty is often explained as a result of measurement , that the act of measuring an object 's position changes its speed , or vice versa . the real origin is much deeper and more amazing . the uncertainty principle exists because everything in the universe behaves like both a particle and a wave at the same time . in quantum mechanics , the exact position and exact speed of an object have no meaning . to understand this , we need to think about what it means to behave like a particle or a wave . particles , by definition , exist in a single place at any instant in time . we can represent this by a graph showing the probability of finding the object at a particular place , which looks like a spike , 100 % at one specific position , and zero everywhere else . waves , on the other hand , are disturbances spread out in space , like ripples covering the surface of a pond . we can clearly identify features of the wave pattern as a whole , most importantly , its wavelength , which is the distance between two neighboring peaks , or two neighboring valleys . but we ca n't assign it a single position . it has a good probability of being in lots of different places . wavelength is essential for quantum physics because an object 's wavelength is related to its momentum , mass times velocity . a fast-moving object has lots of momentum , which corresponds to a very short wavelength . a heavy object has lots of momentum even if it 's not moving very fast , which again means a very short wavelength . this is why we do n't notice the wave nature of everyday objects . if you toss a baseball up in the air , its wavelength is a billionth of a trillionth of a trillionth of a meter , far too tiny to ever detect . small things , like atoms or electrons though , can have wavelengths big enough to measure in physics experiments . so , if we have a pure wave , we can measure its wavelength , and thus its momentum , but it has no position . we can know a particles position very well , but it does n't have a wavelength , so we do n't know its momentum . to get a particle with both position and momentum , we need to mix the two pictures to make a graph that has waves , but only in a small area . how can we do this ? by combining waves with different wavelengths , which means giving our quantum object some possibility of having different momenta . when we add two waves , we find that there are places where the peaks line up , making a bigger wave , and other places where the peaks of one fill in the valleys of the other . the result has regions where we see waves separated by regions of nothing at all . if we add a third wave , the regions where the waves cancel out get bigger , a fourth and they get bigger still , with the wavier regions becoming narrower . if we keep adding waves , we can make a wave packet with a clear wavelength in one small region . that 's a quantum object with both wave and particle nature , but to accomplish this , we had to lose certainty about both position and momentum . the positions is n't restricted to a single point . there 's a good probability of finding it within some range of the center of the wave packet , and we made the wave packet by adding lots of waves , which means there 's some probability of finding it with the momentum corresponding to any one of those . both position and momentum are now uncertain , and the uncertainties are connected . if you want to reduce the position uncertainty by making a smaller wave packet , you need to add more waves , which means a bigger momentum uncertainty . if you want to know the momentum better , you need a bigger wave packet , which means a bigger position uncertainty . that 's the heisenberg uncertainty principle , first stated by german physicist werner heisenberg back in 1927 . this uncertainty is n't a matter of measuring well or badly , but an inevitable result of combining particle and wave nature . the uncertainty principle is n't just a practical limit on measurment . it 's a limit on what properties an object can have , built into the fundamental structure of the universe itself .
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both position and momentum are now uncertain , and the uncertainties are connected . if you want to reduce the position uncertainty by making a smaller wave packet , you need to add more waves , which means a bigger momentum uncertainty . if you want to know the momentum better , you need a bigger wave packet , which means a bigger position uncertainty .
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if you want to make a smaller wave packet , you need to :
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translator : andrea mcdonough reviewer : bedirhan cinar what is a cartoon really ? many of us love cartoons , most of us grew up reading them or having them read to us . the fact is , cartoons have been around a long time . there are all kinds of cartoons : strip comics , comic books , political cartoons , single-panel cartoons , graphic novels , web comics , animation , caricature , there is something for everyone . no matter the form them come in , cartoons elicit all kinds of emotions from the viewer - happiness , sadness , anger , hilarity , calm - and can transmit ideas in an instant . cartoons are a universal medium enjoyed and understood around the world and across borders . this is why they have survived so long as an art form . but how can a medium that is on the surface so simple have so much influence and at times be so meaningful ? let 's look at what a cartoon is . it starts with an idea . the idea can be verbal , written in words , or it can be visual . a visual idea is simply a picture , a drawing , a doodle . these ideas come from a variety of places . cartoonists might find the idea from observing life , reading a newspaper , trawling online . it can come from a sentence someone said or a single word heard on television . cartoonists are like sponges ; they soak up people , places , mannerisms , clothing , and behavior . sometimes they might jot them down in a little black book that they carry around with them . other times , it is just soaked up into the cartoonist 's brain only to be squeezed out later when she is sitting at her drawing table . not only does a cartoonist have to be aware of what she is seeing visually , but she has to listen to herself think . in other words , take the incoming information and select it , shape it , and then use it for a cartoon . now that you have an idea , or something you think could be good for a cartoon , it 's time to shape it . a cartoon is like a staged play . a cartoonist is playwright , director , stage designer , choreographer , and costume designer . a cartoon has characters , a set , dialogue , even if one line , and a backstory . the characters must be dressed to fit the idea , speak in a way that is natural and forwards the idea or gives the punchline . nothing should be in the cartoon that is not absolutely necessary for the advancement of the idea . the image and words have to < i > dance < /i > together in a way that makes sense . it could be a graceful dance , or an awkward dance , if that is part of the humor or idea . and then the execution . some cartoonists sketch the idea with pencil then ink it with pen using a light box . others visualize the image in their head and draw directly on the paper in pen . different kinds of pens are used : felt-tip , mechanical pen , or a crow quill . paper can be light-weight or heavy-bond . many cartoonists add gray tone , called a wash , by using black watercolor and a brush . others use a soft pencil for the tone . color is usually created by using watercolor . a finished cartoon can then be scanned and adjusted , and the caption can be added on the computer with photoshop . new technologies are emerging for the cartoonist 's use in creating her cartoon . photoshop can serve as a tool for color and image . some may draw directly on a tablet with a stylus . the choices at this stage of creation work in tandem with the idea , and often when the final caption is added , it gets adjusted yet again . but , little is left to chance , except , perhaps , some of the watercolor . all these elements function in concert with one another . it 's almost like a dance of words , ideas , and images that work together in order to make the cartoon a timeless , resilient work of art .
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many of us love cartoons , most of us grew up reading them or having them read to us . the fact is , cartoons have been around a long time . there are all kinds of cartoons : strip comics , comic books , political cartoons , single-panel cartoons , graphic novels , web comics , animation , caricature , there is something for everyone .
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cartoons are considered an art form specific to one time and generation .
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what 's the definition of comedy ? thinkers and philosophers from plato and aristotle to hobbes , freud , and beyond , including anyone misguided enough to try to explain a joke , have pondered it , and no one has settled it . you 're lucky you found this video to sort it out . to define comedy , you should first ask why it seems comedy defies definition . the answer 's simple . comedy is the defiance of definition because definitions sometimes need defiance . consider definition itself . when we define , we use language to set borders around a thing that we 've perceived in the whirling chaos of existence . we say what the thing means and fit that in a system of meanings . chaos becomes cosmos . the universe is translated into a cosmological construct of knowledge . and let 's be honest , we need some logical cosmic order , otherwise we 'd have pure chaos . chaos can be rough , so we build a thing that we call reality . now think about logic and logos , that tight knot connecting a word and truth . and let 's jump back to thinking about what 's funny , because some people say it 's real simple : truth is funny . it 's funny because it 's true . but that 's simplistic . plenty of lies are funny . comedic fiction can be funny . made-up nonsense jibberish is frequently hilarious . for instance , florp -- hysterical ! and plenty of truths are n't funny . two plus two truly equals four , but i 'm not laughing just because that 's the case . you can tell a true anecdote , but your date may not laugh . so , why are some untruths and only some truths funny ? how do these laughable truths and untruths relate to that capital-t truth , the cosmological reality of facts and definitions ? and what makes any of them funny ? there 's a frenchman who can help , another thinker who did n't define comedy because he expressly did n't want to . henri bergson 's a french philosopher who prefaced his essay on laughter by saying he would n't define `` the comic '' because it 's a living thing . he argued laughter has a social function to destroy mechanical inelasticity in people 's attitudes and behavior . someone doing the same thing over and over , or building up a false image of themself and the world , or not adapting to reality by just noticing the banana peel on the ground -- this is automatism , ignorance of one 's own mindless rigidity , and it 's dangerous but also laughable and comic ridicule helps correct it . the comic is a kinetic , vital force , or elan vital , that helps us adapt . bergson elaborates on this idea to study what 's funny about all sorts of things . but let 's stay on this . at the base of this concept of comedy is contradiction between vital , adaptive humanity and dehumanized automatism . a set system that claims to define reality might be one of those dehumanizing forces that comedy tends to destroy . now , let 's go back to aristotle . not poetics , where he drops a few thoughts on comedy , no , metaphysics , the fundamental law of non-contradiction , the bedrock of logic . contradictory statements are not at the same time true . if a is an axiomatic statement , it ca n't be the case that a and the opposite of a are both true . comedy seems to live here , to subsist on the illogic of logical contradiction and its derivatives . we laugh when the order we project on the world is disrupted and disproven , like when the way we all act contradicts truths we do n't like talking about , or when strange observations we all make in the silent darkness of private thought are dragged into public by a good stand-up , and when cats play piano , because cats that are also somehow humans disrupt our reality . so , we do n't just laugh at truth , we laugh at the pleasurable , edifying revelation of flaws , incongruities , overlaps , and outright conflicts in the supposedly ordered system of truths we use to define the world and ourselves . when we think too highly of our thinking , when we think things are true just because we all say they 're logos and stop adapting , we become the butt of jokes played on us by that wacky little trickster , chaos . comedy conveys that destructive , instructive playfulness , but has no logical definition because it acts upon our logic paralogically from outside its finite borders . far from having a definite definition , it has an infinite infinition . and the infinition of comedy is that anything can be mined for comedy . thus , all definitions of reality , especially those that claim to be universal , logical , cosmic , capital-t truth become laughable .
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and let 's jump back to thinking about what 's funny , because some people say it 's real simple : truth is funny . it 's funny because it 's true . but that 's simplistic .
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are things funny if they ’ re true ?
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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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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 .
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how many different combinations of animals , elements and yin/yang are there total in the chinese zodiac ?
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as a wildfire rages through the grasslands , three lions and three wildebeest flee for their lives . to escape the inferno , they must cross over to the left bank of a crocodile-infested river . fortunately , there happens to be a raft nearby . it can carry up to two animals at a time , and needs as least one lion or wildebeest on board to row it across the river . there 's just one problem . if the lions ever outnumber the wildebeest on either side of the river , even for a moment , their instincts will kick in , and the results wo n't be pretty . that includes the animals in the boat when it 's on a given side of the river . what 's the fastest way for all six animals to get across without the lions stopping for dinner ? pause here if you want to figure it out for yourself . answer in : 3 answer in : 2 answer in : 1 if you feel stuck on a problem like this , try listing all the decisions you can make at each point , and the consequences each choice leads to . for instance , there are five options for who goes across first : one wildebeest , one lion , two wildebeest , two lions , or one of each . if one animal goes alone , it 'll just have to come straight back . and if two wildebeest cross first , the remaining one will immediately get eaten . so those options are all out . sending two lions , or one of each animal , can actually both lead to solutions in the same number of moves . for the sake of time , we 'll focus on the second one . one of each animal crosses . now , if the wildebeest stays and the lion returns , there will be three lions on the right bank . bad news for the two remaining wildebeest . so we need to have the lion stay on the left bank and the wildebeest go back to the right . now we have the same five options , but with one lion already on the left bank . if two wildebeest go , the one that stays will get eaten , and if one of each animal goes , the wildebeest on the raft will be outnumbered as soon as it reaches the other side . so that 's a dead end , which means that at the third crossing , only the two lions can go . one gets dropped off , leaving two lions on the left bank . the third lion takes the raft back to the right bank where the wildebeest are waiting . what now ? well , since we 've got two lions waiting on the left bank , the only option is for two wildebeest to cross . next , there 's no sense in two wildebeest going back , since that just reverses the last step . and if two lions go back , they 'll outnumber the wildebeest on the right bank . so one lion and one wildebeest take the raft back leaving us with one of each animal on the left bank and two of each on the right . again , there 's no point in sending the lion-wildebeest pair back , so the next trip should be either a pair of lions or a pair of wildebeest . if the lions go , they 'd eat the wildebeest on the left , so they stay , and the two wildebeest cross instead . now we 're quite close because the wildebeest are all where they need to be with safety in numbers . all that 's left is for that one lion to raft back and bring his fellow lions over one by one . that makes eleven trips total , the smallest number needed to get everyone across safely . the solution that involves sending both lions on the first step works similarly , and also takes eleven crossings . the six animals escape unharmed from the fire just in time and begin their new lives across the river . of course , now that the danger 's passed , it remains to be seen how long their unlikely alliance will last .
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answer in : 3 answer in : 2 answer in : 1 if you feel stuck on a problem like this , try listing all the decisions you can make at each point , and the consequences each choice leads to . for instance , there are five options for who goes across first : one wildebeest , one lion , two wildebeest , two lions , or one of each . if one animal goes alone , it 'll just have to come straight back .
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why can ’ t the first move be two wildebeest going across ?
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this is a crystal of sugar . if you press on it , it will actually generate its own electricity . how can this simple crystal act like a tiny power source ? because sugar is piezoelectric . piezoelectric materials turn mechanical stress , like pressure , sound waves , and other vibrations into electricity and vice versa . this odd phenomenon was first discovered by the physicist pierre curie and his brother jacques in 1880 . they discovered that if they compressed thin slices of certain crystals , positive and negative charges would appear on opposite faces . this difference in charge , or voltage , meant that the compressed crystal could drive current through a circuit , like a battery . and it worked the other way around , too . running electricity through these crystals made them change shape . both of these results , turning mechanical energy into electrical , and electrical energy into mechanical , were remarkable . but the discovery went uncelebrated for several decades . the first practical application was in sonar instruments used to detect german submarines during world war i. piezoelectric quartz crystals in the sonar 's transmitter vibrated when they were subjected to alternating voltage . that sent ultrasound waves through the water . measuring how long it took these waves to bounce back from an object revealed how far away it was . for the opposite transformation , converting mechanical energy to electrical , consider the lights that turn on when you clap . clapping your hands send sound vibrations through the air and causes the piezo element to bend back and forth . this creates a voltage that can drive enough current to light up the leds , though it 's conventional sources of electricity that keep them on . so what makes a material piezoelectric ? the answer depends on two factors : the materials atomic structure , and how electric charge is distributed within it . many materials are crystalline , meaning they 're made of atoms or ions arranged in an orderly three-dimensional pattern . that pattern has a building block called a unit cell that repeats over and over . in most non-piezoelectric crystalline materials , the atoms in their unit cells are distributed symmetrically around a central point . but some crystalline materials do n't possess a center of symmetry making them candidates for piezoelectricity . let 's look at quartz , a piezoelectric material made of silicon and oxygen . the oxygens have a slight negative charge and silicons have a slight positive , creating a separation of charge , or a dipole along each bond . normally , these dipoles cancel each other out , so there 's no net separation of charge in the unit cell . but if a quartz crystal is squeezed along a certain direction , the atoms shift . because of the resulting asymmetry in charge distribution , the dipoles no longer cancel each other out . the stretched cell ends up with a net negative charge on one side and a net positive on the other . this charge imbalance is repeated all the way through the material , and opposite charges collect on opposite faces of the crystal . this results in a voltage that can drive electricity through a circuit . piezoelectric materials can have different structures . but what they all have in common is unit cells which lack a center of symmetry . and the stronger the compression on piezoelectric materials , the larger the voltage generated . stretch the crystal , instead , and the voltage will switch , making current flow the other way . more materials are piezoelectric than you might think . dna , bone , and silk all have this ability to turn mechanical energy into electrical . scientists have created a variety of synthetic piezoelectric materials and found applications for them in everything from medical imaging to ink jet printers . piezoelectricity is responsible for the rhythmic oscillations of the quartz crystals that keep watches running on time , the speakers of musical birthday cards , and the spark that ignites the gas in some barbecue grill lighters when you flick the switch . and piezoelectric devices may become even more common since electricity is in high demand and mechanical energy is abundant . there are already train stations that use passengers ' footsteps to power the ticket gates and displays and a dance club where piezoelectricity helps power the lights . could basketball players running back and forth power the scoreboard ? or might walking down the street charge your electronic devices ? what 's next for piezoelectricity ?
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this creates a voltage that can drive enough current to light up the leds , though it 's conventional sources of electricity that keep them on . so what makes a material piezoelectric ? the answer depends on two factors : the materials atomic structure , and how electric charge is distributed within it .
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what is the necessary condition for a material to be piezoelectric ?
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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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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 .
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sacajawea gave birth to a little boy she named jean baptiste charbonneau but lewis and clark called him :
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so you just strained a muscle and the inflammation is unbearable . you wish you had something ice-cold to dull the pain , but to use an ice pack , you would have had to put it in the freezer hours ago . fortunately , there 's another option . a cold pack can be left at room temperature until the moment you need it , then just snap it as instructed and within seconds you 'll feel the chill . but how can something go from room temperature to near freezing in such a short time ? the answer lies in chemistry . your cold pack contains water and a solid compound , usually ammonium nitrate , in different compartments separated by a barrier . when the barrier is broken , the solid dissolves causing what 's known as an endothermic reaction , one that absorbs heat from its surroundings . to understand how this works , we need to look at the two driving forces behind chemical processes : energetics and entropy . these determine whether a change occurs in a system and how energy flows if it does . in chemistry , energetics deals with the attractive and repulsive forces between particles at the molecular level . this scale is so small that there are more water molecules in a single glass than there are known stars in the universe . and all of these trillions of molecules are constantly moving , vibrating and rotating at different rates . we can think of temperature as a measurement of the average motion , or kinetic energy , of all these particles , with an increase in movement meaning an increase in temperature , and vice versa . the flow of heat in any chemical transformation depends on the relative strength of particle interactions in each of a substance 's chemical states . when particles have a strong mutual attractive force , they move rapidly towards one another , until they get so close , that repulsive forces push them away . if the initial attraction was strong enough , the particles will keep vibrating back and forth in this way . the stronger the attraction , the faster their movement , and since heat is essentially motion , when a substance changes to a state in which these interactions are stronger , the system heats up . but our cold packs do the opposite , which means that when the solid dissolves in the water , the new interactions of solid particles and water molecules with each other are weaker than the separate interactions that existed before . this makes both types of particles slow down on average , cooling the whole solution . but why would a substance change to a state where the interactions were weaker ? would n't the stronger preexisting interactions keep the solid from dissolving ? this is where entropy comes in . entropy basically describes how objects and energy are distributed based on random motion . if you think of the air in a room , there are many different possible arrangements for the trillions of particles that compose it . some of these will have all the oxygen molecules in one area , and all the nitrogen molecules in another . but far more will have them mixed together , which is why air is always found in this state . now , if there are strong attractive forces between particles , the probability of some configurations can change even to the point where the odds do n't favor certain substances mixing . oil and water not mixing is an example . but in the case of the ammonium nitrate , or other substance in your cold pack , the attractive forces are not strong enough to change the odds , and random motion makes the particles composing the solid separate by dissolving into the water and never returning to their solid state . to put it simply , your cold pack gets cold because random motion creates more configurations where the solid and water mix together and all of these have even weaker particle interaction , less overall particle movement , and less heat than there was inside the unused pack . so while the disorder that can result from entropy may have caused your injury in the first place , its also responsible for that comforting cold that soothes your pain .
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your cold pack contains water and a solid compound , usually ammonium nitrate , in different compartments separated by a barrier . when the barrier is broken , the solid dissolves causing what 's known as an endothermic reaction , one that absorbs heat from its surroundings . to understand how this works , we need to look at the two driving forces behind chemical processes : energetics and entropy .
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the breaking of bonds on the molecular level always requires an input of energy . therefore forming bonds always releases energy . based on this , build an explanation for why a reaction would release heat ( exothermic ) and why a reaction would consume heat ( endothermic ) .
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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 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 .
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which activity necessarily involves mental synthesis ( mental synthesis is conscious purposeful prefrontal cortex-controlled imagination ) ?
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today we 're talking about weird materials that we use in space , in robots and in your mouth . i 'm talking about shape memory alloys . like the name says , these are metals that remember different shapes . to understand how these metals work , we 've got to talk about atoms and organizing . let 's talk about atoms first . atoms are tiny bits of matter that you can not see with your eye yet they make up everything in our world , from the chair that you 're sitting on to your cell phone . atoms have some surprising ways of behaving too . we 'll talk about that shortly . now , how big is an atom ? well , imagine pulling one of your hairs out of your head and whittling it like a stick 100,000 times . one of those shavings would be the width of an atom . they 're that small . now let 's talk about atoms and organizing . you may not know this , but atoms arrange themselves similar to the way we humans arrange ourselves . sometimes they sit in rows , like we do on a bus or an airplane . we call that seating arrangement a phase . other times they sit diagonal from each other , sort of like seats in a movie theater or sports stadium . this is another phase . when atoms move from one seating to another this is called a phase change . phase changes are all around us . you may already know about water 's phases : solid , liquid and gas . many other materials have phases like that too . some of them have several solid phases . ok. back to those shape memory alloys we mentioned before . when we say that the metals remember their different shapes , what we 're really saying is they remember different seating arrangements of atoms . when the atoms rearrange , the metal moves from one shape to another . let 's look at a phase change in action . here i have a metal wire that is made out of nickel and titanium . this metal wire is a shape memory alloy , and i 'm going to make it switch between its different shapes using heat from a lighter . watch this . i 'm going to wrap this wire around my finger and then heat it . amazing ! that wire returns to a straight line , when i heat it . let 's try that again . i 'm going to wrap it around my finger , and heat it . yep , that 's still amazing . not only is it amazing , this is weird , because metals generally do n't do that . here 's a paper clip . when i heat it , i get nothing . what we 're seeing is the shape memory wire changing phases when it gets hot . when the wire is cold , atoms are in a diagonal arrangement , like the movie theater seating , we talked about before . we call this a monoclinic arrangement , and scientists will call this phase martensite . when i heated up the wire , the atoms moved into columns like airplane seating . this is a cubic arrangement . scientists will call this phase austenite . so when we added the heat , the atoms shifted positions seamlessly , and they 'll do this forever . they have this coordinated motion , just like members of a tireless marching band . each makes a small shift , but all together those small shifts create a totally different pattern . so that 's pretty cool , but where do we use these materials ? well , if you look in the sky tonight , shape memory alloys are at work - on mars . they 're used to move panels on the mars rover , so that it can study the environment . like our metal straightened when it was heated , the metals holding the panels will move when electrically heated . when we stop heating the shape memory metal , the panel will return back , due to an opposing spring . back on earth , shape memory alloys are used to open up clogged arteries as stents , which are small collapsible springs that force open passages . shape memory alloys are also used to move robots , toy butterflies , teeth in braces , and for a perfect fit every time , shape memory wires are used as underwires in bras . now you know victoria 's secret . by popping a bra into the dryer , it 'll be brand new every time . so whether it 's on mars or in your mouth , small atomic movements can create huge changes , and understanding the way atoms behave allows us to make materials that make our world a better place .
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today we 're talking about weird materials that we use in space , in robots and in your mouth . i 'm talking about shape memory alloys . like the name says , these are metals that remember different shapes .
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artists are always looking for cool new materials to work with . if you were to make a sculpture with shape memory wires and wanted them to change shape , what would you use to do that ?
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energy is all around us , a physical quantity that follows precise natural laws . our universe has a finite amount of it ; it 's neither created nor destroyed but can take different forms , such as kinetic or potential energy , with different properties and formulas to remember . for instance , an led desk lamp 's 6 watt bulb transfers 6 joules of light energy per second . but let 's jump back up into space to look at our planet , its systems , and their energy flow . earth 's physical systems include the atmosphere , hydrosphere , lithosphere , and biosphere . energy moves in and out of these systems , and during any energy transfer between them , some is lost to the surroundings , as heat , light , sound , vibration , or movement . our planet 's energy comes from internal and external sources . geothermal energy from radioactive isotopes and rotational energy from the spinning of the earth are internal sources of energy , while the sun is the major external source , driving certain systems , like our weather and climate . sunlight warms the surface and atmosphere in varying amounts , and this causes convection , producing winds and influencing ocean currents . infrared radiation , radiating out from the warmed surface of the earth , gets trapped by greenhouse gases and further affects the energy flow . the sun is also the major source of energy for organisms . plants , algae , and cyanobacteria use sunlight to produce organic matter from carbon dioxide and water , powering the biosphere 's food chains . we release this food energy using chemical reactions , like combustion and respiration . at each level in a food chain , some energy is stored in newly made chemical structures , but most is lost to the surroundings , as heat , like your body heat , released by your digestion of food . now , as plants are eaten by primary consumers , only about 10 % of their total energy is passed on to the next level . since energy can only flow in one direction in a food chain , from producers on to consumers and decomposers , an organism that eats lower on the food chain , is more efficient than one higher up . so eating producers is the most efficient level at which an animal can get its energy , but without continual input of energy to those producers , mostly from sunlight , life on earth as we know it would cease to exist . we humans , of course , spend our energy doing a lot of things besides eating . we travel , we build , we power all sorts of technology . to do all this , we use sources like fossil fuels : coal , oil , and natural gas , which contain energy that plants captured from sunlight long ago and stored in the form of carbon . when we burn fossil fuels in power plants , we release this stored energy to generate electricity . to generate electricity , heat from burning fossil fuels is used to power turbines that rotate magnets , which , in turn , create magnetic field changes relative to a coil of wire , causing electrons to be induced to flow in the wire . modern civilization depends on our ability to keep powering that flow of electrons . fortunately , we are n't limited to burning non-renewable fossil fuels to generate electricity . electrons can also be induced to flow by direct interaction with light particles , which is how a solar cell operates . other renewable energy sources , such as wind , water , geothermal , and biofuels can also be used to generate electricity . global demand for energy is increasing , but the planet has limited energy resources to access through a complex energy infrastructure . as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important . access to energy impacts health , education , political power , and socioeconomic status . if we improve our energy efficiency , we can use our natural resources more responsibly and improve quality of life for everyone .
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as populations rise , alongside rates of industrialization and development , our energy decisions grow more and more important . access to energy impacts health , education , political power , and socioeconomic status . if we improve our energy efficiency , we can use our natural resources more responsibly and improve quality of life for everyone .
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brainstorm some of the impacts you think your generation ’ s energy consumption is having today and on tomorrow ’ s future generations .
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we like to think of romantic feelings as spontaneous and indescribable things that come from the heart . but it 's actually your brain running a complex series of calculations within a matter of seconds that 's responsible for determining attraction . does n't sound quite as poetic , does it ? but just because the calculations are happening in your brain does n't mean those warm , fuzzy feelings are all in your head . in fact , all five of your senses play a role , each able to vote for , or veto , a budding attraction . the eyes are the first components in attraction . many visual beauty standards vary between cultures and eras , and signs of youth , fertility and good health , such as long lustrous hair , or smooth , scar-free skin , are almost always in demand because they 're associated with reproductive fitness . and when the eyes spot something they like , our instinct is to move closer so the other senses can investigate . the nose 's contribution to romance is more than noticing perfume or cologne . it 's able to pick up on natural chemical signals known as pheromones . these not only convey important physical or genetic information about their source but are able to activate a physiological or behavioral response in the recipient . in one study , a group of women at different points in their ovulation cycles wore the same t-shirts for three nights . after male volunteers were randomly assigned to smell either one of the worn shirts , or a new unworn one , saliva samples showed an increase in testosterone in those who had smelled a shirt worn by an ovulating woman . such a testosterone boost may give a man the nudge to pursue a woman he might not have otherwise noticed . a woman 's nose is particularly attuned to mhc molecules , which are used to fight disease . in this case , opposites attract . when a study asked women to smell t-shirts that had been worn by different men , they preferred the odors of those whose mhc molecules differed from theirs . this makes sense . genes that result in a greater variety of immunities may give offspring a major survival advantage . our ears also determine attraction . men prefer females with high-pitched , breathy voices , and wide formant spacing , correlated with smaller body size . while women prefer low-pitched voices with a narrow formant spacing that suggest a larger body size . and not surprisingly , touch turns out to be crucial for romance . in this experiment , not realizing the study had begun , participants were asked to briefly hold the coffee , either hot or iced . later , the participants read a story about a hypothetical person , and were asked to rate their personality . those who had held the hot cup of coffee perceived the person in the story as happier , more social , more generous and better-natured than those who had held the cup of iced coffee , who rated the person as cold , stoic , and unaffectionate . if a potential mate has managed to pass all these tests , there 's still one more : the infamous first kiss , a rich and complex exchange of tactile and chemical cues , such as the smell of one 's breath , and the taste of their mouth . this magical moment is so critical that a majority of men and women have reported losing their attraction to someone after a bad first kiss . once attraction is confirmed , your bloodstream is flooded with norepinephrine , activating your fight or flight system . your heart beats faster , your pupils dilate , and your body releases glucose for additional energy , not because you 're in danger but because your body is telling you that something important is happening . to help you focus , norepinephrine creates a sort of tunnel vision , blocking out surrounding distractions , possibly even warping your sense of time , and enhancing your memory . this might explain why people never forget their first kiss . the idea of so much of our attraction being influenced by chemicals and evolutionary biology may seem cold and scientific rather than romantic , but the next time you see someone you like , try to appreciate how your entire body is playing matchmaker to decide if that beautiful stranger is right for you .
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the nose 's contribution to romance is more than noticing perfume or cologne . it 's able to pick up on natural chemical signals known as pheromones . these not only convey important physical or genetic information about their source but are able to activate a physiological or behavioral response in the recipient . in one study , a group of women at different points in their ovulation cycles wore the same t-shirts for three nights .
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a chemical messenger emitted from one organism that activates a physiological or behavioral response in another is called what ?
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translator : jessica ruby reviewer : caroline cristal let 's say that it would take you ten minutes to solve this puzzle . how long would it take if you received constant electric shocks to your hands ? longer , right ? because the pain would distract you from the task . well , maybe not ; it depends on how you handle pain . some people are distracted by pain . it takes them longer to complete a task , and they do it less well . other people use tasks to distract themselves from pain , and those people actually do the task faster and better when they 're in pain than when they 're not . some people can just send their mind wandering to distract themselves from pain . how can different people be subjected to the exact same painful stimulus and yet experience the pain so differently ? and why does this matter ? first of all , what is pain ? pain is an unpleasant sensory and emotional experience , associated with actual or potential tissue damage . pain is something we experience , so it 's best measured by what you say it is . pain has an intensity ; you can describe it on a scale from zero , no pain , to ten , the most pain imaginable . but pain also has a character , like sharp , dull , burning , or aching . what exactly creates these perceptions of pain ? well , when you get hurt , special tissue damage-sensing nerve cells , called nociceptors , fire and send signals to the spinal cord and then up to the brain . processing work gets done by cells called neurons and glia . this is your grey matter . and brain superhighways carry information as electrical impulses from one area to another . this is your white matter . the superhighway that carries pain information from the spinal cord to the brain is our sensing pathway that ends in the cortex , a part of the brain that decides what to do with the pain signal . another system of interconnected brain cells called the salience network decides what to pay attention to . since pain can have serious consequences , the pain signal immediately activates the salience network . now , you 're paying attention . the brain also responds to the pain and has to cope with these pain signals . so , motor pathways are activated to take your hand off a hot stove , for example . but modulation networks are also activated that deliver endorphins and enkephalins , chemicals released when you 're in pain or during extreme exercise , creating the runner 's high . these chemical systems help regulate and reduce pain . all these networks and pathways work together to create your pain experience , to prevent further tissue damage , and help you to cope with pain . this system is similar for everyone , but the sensitivity and efficacy of these brain circuits determines how much you feel and cope with pain . this is why some people have greater pain than others and why some develop chronic pain that does not respond to treatment , while others respond well . variability in pain sensitivities is not so different than all kinds of variability in responses to other stimuli . like how some people love roller coasters , but other people suffer from terrible motion sickness . why does it matter that there is variability in our pain brain circuits ? well , there are many treatments for pain , targeting different systems . for mild pain , non-prescription medications can act on cells where the pain signals start . other stronger pain medicines and anesthetics work by reducing the activity in pain-sensing circuits or boosting our coping system , or endorphins . some people can cope with pain using methods that involve distraction , relaxation , meditation , yoga , or strategies that can be taught , like cognitive behavioral therapy . for some people who suffer from severe chronic pain , that is pain that does n't go away months after their injury should have healed , none of the regular treatments work . traditionally , medical science has been about testing treatments on large groups to determine what would help a majority of patients . but this has usually left out some who did n't benefit from the treatment or experienced side effects . now , new treatments that directly stimulate or block certain pain-sensing attention or modulation networks are being developed , along with ways to tailor them to individual patients , using tools like magnetic resonance imaging to map brain pathways . figuring out how your brain responds to pain is the key to finding the best treatment for you . that 's true personalized medicine .
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figuring out how your brain responds to pain is the key to finding the best treatment for you . that 's true personalized medicine .
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how can understanding brain variability help to develop personalized medicine for pain ?
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brady haran : hey there , everyone . today 's video is about richard feynman -- a lot of people 's favorite scientist -- and safe breaking . but i just wanted to point out at the start that most safes , or secure filing cabinets , actually have one dial . and if you 've got a three number combination , for example , you 'll turn that dial in one direction , then the other direction , and then back in the other direction . and that 's how you open it . but the mock up that we 've used in this video -- and it is a mock up , i can assure you . it 's about as far from a safe as you could get . we 've used three dials . that kind of makes things a bit more visual , a bit easier to understand looking at it in that way . but in most cases , the sort of safes we 're talking about will actually be using one dial . i do n't want to get all the safe enthusiasts out there too fired up and angry in the comments section . but for now , here 's professor bowley with his pretend safe and the story of richard feynman and his world war ii safe cracking . professor roger bowley : i 'm talking about feynman and how he managed to crack safes when he was working on the atomic bomb project in los alamos in the early '40s . his wife had died . so early in the 1940s , his wife died . and he was stuck in the middle of los alamos , not able to get out . it was a sort of desert area around there . he was stuck with lots of other theoretical physicists . so he needed something for amusement . and as a hobby , he tried cracking open all the safes in los alamos . now , they had new , purpose built safes with locks on them made by the mosler lock company . you can imagine 100 numbers for this , 100 numbers for that , 100 numbers for that -- a million , a million possible settings . and if you fiddle them around , it 'll take about five seconds to do it . so if you tried to crack it , it will take you about 60 days . on the average , it 'd be 30 days , but 60 days if you screw up and it takes the last one to open it . well , feynman was a group leader . so he was given one of these in his office to keep all the top secret files that he might come up with . so he knew how this worked mechanically , because he fiddled around with it . he 'd just fidget with anything . he wanted to know how it worked . and he found by trial and error , suppose the number should be 20 , it was set at . actually , it started at 25 , and a lot of people did n't change it from 25 , naught , 25 . that was the default . and if he wanted to crack the safe , a lot of times , people left it in the default setting , because it 's the easiest one to remember . suppose he set it at 20 . now , he found that if he tried to set it at 20 and it opened , he could also set it to 21 and it would open , or 22 . there was some slack on this . this was not mechanically perfect . so there was a bit of tolerance , plus or minus 2 on every single number , which meant that if you set it at 20 , it could be 21 or 22 or 19 or 18 -- and the same for this dial and the same for this dial . so now , if you go through all the combinations , you only have to do 3 , 8 , 13 and so on -- every fifth one -- to make sure you cover them all . now , there are only 20 settings for this , 20 for that , and 20 for that . so automatically , that 's gone down , oh , i ca n't do it . can you do it in your head , brady ? it 's really quite difficult . 8,000 different settings -- now , that becomes doable mechanically . it will take you something like 10 hours working solidly overnight . and you could do it . and he could do that . he worked out how to do it . he found out other ways of doing this . he found that most people will set a birthday , an anniversary , some well-defined date that -- i do n't know , the independence day in the united states of america , whatever . and it would not be an ordinary number , because if it 's going to be , say , my birthday , which is the 21st of april if anybody wants to send me presents . there 's the 21st . 04 -- 04 is there . and i 'm born in 1946 , which is down there . so for the top one , which is the days of the month , there are typically 30 days in a month . so let 's suppose there are just 30 and never 31 . 30 days in the month , you would need to set it in six different positions . now , for the months , there 's 12 months in the year , so you may need not two , but three for that . so now , we 've got six settings here , three settings there . and for the year -- well , now , the year , if it 's some date , it 's going to be something in the past . so how long back in the past is somewhat arbitrary . but suppose 45 would do , and then it would be 9 . he was doing it 1942 or '43 or '44 . all right . so the test would be somewhere around there . so 45 is a natural number to look at , because then you do n't have to go back into the previous century . 6 for this one , 3 for this one , and 9 for that one . and you multiply them together . and you get out 162 . so that 's 162 different settings . five seconds for each , 162 -- that 's 800 seconds . it 's about 12 minutes . so he could go in and if somebody had chosen one of those dates , instead of having 8,000 , he 's got 162 . and he can do it in 12 minutes . on the average , it will be six minutes , because he might be reach it in the first go or he might reach it after 12 minutes . but he would only require 12 minutes . so he would go in and make a big fuss of going into the office and say , i 'm not going to show the secrets . these are top secret stuff . i do n't want everybody to know my secrets . and he 'd carry in a bag with tools -- screwdrivers , picks , all sorts of things that people would think you crack safes with -- shut the door , and in 12 minutes , he would do it . he 'd take a magazine in with him . sometimes , he 'd get it done straight away and he 'd do some exercise and wait for 20 minutes just to make everybody believe it was tough work doing this . and then he 'd come out with a bit of sweat on his brow , saying , that was hard work . so those were the main techniques that he used . 162 means that this is n't safe and using your birthday or anniversary is not safe . but after that , he learned another trick . and he got the number down to 20 . out of all these million , there were 20 . and it turns out that if you open the safe and leave it open , and there 's a little draw on the bottom . and he goes into somebody else 's office . he chats to them . and the safe is open . he fiddles with all the knobs . and after two years of practice , he got these two sorted out by fiddling around with the knobs when the safe was open in somebody else 's office . he 'd go back afterwards -- and they do n't realize he 's been doing this -- and writes down these two numbers in a little book and says such and such . so by the end of the war , he could go into anybody 's office . he 's got the last two numbers . there are 20 settings . it takes him a minute and a half to open the safe , or less . so he really has to spin it up . he has a reputation of safe cracking . and everybody thinks he knows how to use picks . but he 's just used human nature , the tolerance of all this , and deviousness , just to show how clever he was . he was doing it just to show how clever he was . he was obnoxious . he would like to be one up on everybody else . but there was a security problem there . and the guy who he shared a room with was the guy who gave the secrets of the bomb to the russians , which is klaus fuchs . he was a roomie of his . brady haran : but for all his showing off about safe breaking , it turns out the real spy was in the room with him . professor roger bowley : yes . but i do n't -- well , yes . when you look at this , now that we live in worlds where you have a little security code for everything , this seems unbelievably primitive -- phone hacking and everything else going on . but people were n't -- if you 're a scientist , you 're not really looking at the other guy next door and wondering whether he 's letting all your secrets out .
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it 's about as far from a safe as you could get . we 've used three dials . that kind of makes things a bit more visual , a bit easier to understand looking at it in that way .
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how many total combinations are possible when you account for all three locks ?
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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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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 .
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if matt had rounded the circumference and diameter to the nearest whole pie , what would his answer have been for pi ?
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depression is the leading cause of disability in the world . in the united states , close to 10 % of adults struggle with depression . but because it 's a mental illness , it can be a lot harder to understand than , say , high cholesterol . one major source of confusion is the difference between having depression and just feeling depressed . almost everyone feels down from time to time . getting a bad grade , losing a job , having an argument , even a rainy day can bring on feelings of sadness . sometimes there 's no trigger at all . it just pops up out of the blue . then circumstances change , and those sad feelings disappear . clinical depression is different . it 's a medical disorder , and it wo n't go away just because you want it to . it lingers for at least two consecutive weeks , and significantly interferes with one 's ability to work , play , or love . depression can have a lot of different symptoms : a low mood , loss of interest in things you 'd normally enjoy , changes in appetite , feeling worthless or excessively guilty , sleeping either too much or too little , poor concentration , restlessness or slowness , loss of energy , or recurrent thoughts of suicide . if you have at least five of those symptoms , according to psychiatric guidelines , you qualify for a diagnosis of depression . and it 's not just behavioral symptoms . depression has physical manifestations inside the brain . first of all , there are changes that could be seen with the naked eye and x-ray vision . these include smaller frontal lobes and hippocampal volumes . on a more microscale , depression is associated with a few things : the abnormal transmission or depletion of certain neurotransmitters , especially serotonin , norepinephrine , and dopamine , blunted circadian rhythms , or specific changes in the rem and slow-wave parts of your sleep cycle , and hormone abnormalities , such as high cortisol and deregulation of thyroid hormones . but neuroscientists still do n't have a complete picture of what causes depression . it seems to have to do with a complex interaction between genes and environment , but we do n't have a diagnostic tool that can accurately predict where or when it will show up . and because depression symptoms are intangible , it 's hard to know who might look fine but is actually struggling . according to the national institute of mental health , it takes the average person suffering with a mental illness over ten years to ask for help . but there are very effective treatments . medications and therapy complement each other to boost brain chemicals . in extreme cases , electroconvulsive therapy , which is like a controlled seizure in the patient 's brain , is also very helpful . other promising treatments , like transcranial magnetic stimulation , are being investigated , too . so , if you know someone struggling with depression , encourage them , gently , to seek out some of these options . you might even offer to help with specific tasks , like looking up therapists in the area , or making a list of questions to ask a doctor . to someone with depression , these first steps can seem insurmountable . if they feel guilty or ashamed , point out that depression is a medical condition , just like asthma or diabetes . it 's not a weakness or a personality trait , and they should n't expect themselves to just get over it anymore than they could will themselves to get over a broken arm . if you have n't experienced depression yourself , avoid comparing it to times you 've felt down . comparing what they 're experiencing to normal , temporary feelings of sadness can make them feel guilty for struggling . even just talking about depression openly can help . for example , research shows that asking someone about suicidal thoughts actually reduces their suicide risk . open conversations about mental illness help erode stigma and make it easier for people to ask for help . and the more patients seek treatment , the more scientists will learn about depression , and the better the treatments will get .
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and it 's not just behavioral symptoms . depression has physical manifestations inside the brain . first of all , there are changes that could be seen with the naked eye and x-ray vision .
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what do you call a specialized cell that transmits nerve impulses in the brain ?
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ralph waldo emerson is the father of american literature . in a series of strikingly original essays , written in the mid-nineteenth century , he fundamentally changed the way that america saw its cultural and artistic possibilities , and he enabled a separation from transatlantic literary traditions . `` we have listened too long ... '' , he wrote , `` ... to the courtly muses of europe . '' emerson 's abjection of cultural traditions brought about what one contemporary called : `` america 's intellectual declaration of independence . '' and he established generational conflict and transformation as commanding ideas in american literature . emerson himself hardly seemed destined to fit a revolutionary mold . he was born in 1803 , the son of a boston preacher , and was descended from a line of new england ministers that went back to the bedrock of seventeenth-century puritanism . when his father died in 1811 , his mother took in boarders to pay the rent . still , she sent her son to harvard in 1817 , and then harvard divinity school to train for the priesthood in 1825 . as a young man , emerson was strongly influenced by a remarkable aunt of his : mary moody emerson , who though self-taught , had read everything from shakespeare to the romantics and it formed a unique religious perspective based on piety nature and literature , that would resonate powerfully in the life and work of her nephew . so when emerson was ordained in 1829 , marrying the love of his life ellen tucker in the same year , he was already unsatisfied with the formal nature of new england religious orthodoxy . when ellen died of tuberculosis just two years later , he resigned from the church and soon after embarked on a trip to europe . leaving on christmas day 1832 , two crucial things happened to emerson on that tour of europe . in paris , he went to the famous `` jardin des plantes '' , a botanical and zoological garden . there he had an epiphany . writing in his journal that : `` i feel the centipede in me , the cayman , carp , eagle and fox ... ... i am moved by strange sympathies . i say continually : i will be a naturalist . `` . emerson 's insight was that nature is in us , a part of us , and not just its higher forms , but in all its grotesquerie and wildness . the second thing that happened on that tour , was that emerson met the english romantic poets : samuel taylor coleridge and william wordsworth , and found them rather ordinary , dry and conservative men . the insight that emerson drew from this , was that if great men could be so ordinary , why should not ordinary men be great ? as he would write a few years later , meek young men grow up in libraries , believing it their duty , to accept the views which cicero , locke , bacon have given . forgetful that cicero , locke and bacon were only young men in libraries when they wrote these books . emerson had found two ideas that would guide his life 's work . that man and nature are one and that everyone can recognize that they are a uniquely , significant human being . on his return to america in 1833 , emerson became a professional lecturer giving talks on natural history and literature in halls around new england . he remarried and had several children , presenting a stolid , bourgeois appearance to the world . but his inner life was full of turbulence and originality . in his 1836 essay , `` nature '' , emerson outlined the germ of a new philosophy , a key element of this , was the importance of american originality . in its opening lines , emerson wrote : `` our age is retrospective , it builds the sepulchres of the fathers . it writes biographies , histories and criticism . the foregoing generations beheld god and nature face to face ; we , through their eyes . why should not we also enjoy an original relation to the universe ? `` . america , needed to stop looking back to its european heritage and start looking about it self . no past moment was more important , than the present moment . no tradition was more important , than novelty . no generation , was better than the current generation . everything that matters is here now insisted emerson , and that here was : america . this was an extension of emerson 's ideas , about the significance of the individual that came under the heading of what he called `` self-reliance '' . everywhere emerson looked , he saw people leading lives that were based on tradition , that were limited by religious forms and social habits . no one could be themselves , emerson thought , because they were all too busy being what they were supposed to be . emerson wanted to get rid of each of these burdens : the past , religion and social forms , so that each person could find out who they truly were . as he put it : `` history is an impertinence and an injury ; our religion , we have not chosen , but society has chosen for us ... and ... ... society everywhere is in conspiracy against the manhood of every one of its members . '' we must , he argued , live from within trusting nothing but our own intuitions . for , as he concluded ... ... nothing is at last sacred but the integrity of your own mind . this leaves open a vital question : what is your nature ... ... once you 've rid yourself of history , tradition and religion ? what can be said is that it is n't necessarily self-indulgence , haterism or narcissism . rather , it 's the surrender to that force which emerson recognized back in the jardin des plantes . an obedience to nature itself . by nature , emerson seem to mean the natural world : plants , animals , rocks and sky , but what he really meant was god . emerson was a `` pantheist '' . that is , someone who believe that god exists in every part of creation , from the smallest grain of sand to the stars . but also crucially that the divine spark is in each of us . in following ourselves , we are therefore not merely being fickle or selfish , we are rather , releasing a divine will , that history , society and organized religion normally hide from us . the individual as emerson writes `` is a god in ruins '' . but we have it within us , by casting off all custom to rebuild ourselves emerson makes this pantheist connection , explicit in what are perhaps his most famous lines . `` crossing a bear common , in snow puddles at twilight under a clouded sky , without having in my thoughts any occurrence of special good fortune , i 've enjoyed a perfect exhilaration . i am glad to the brink of fear , standing on the bare ground , my head bathed by the blythe air and uplifted into infinite space , all mean egotism vanishes ... ... i become a transparent eyeball ... ... i am nothing ... ... i see all . the currents of the universal being circulate through me ... ... i am part or particle of god ! in the romantic tradition on which emerson draws , it is the sublime , great mountains , rushing torrance , dark forests , which releases the inner vision as we find ourselves in all of them . for emerson , it 's a perfectly dull walk across an ordinary common on a dark winter 's evening that brings him , to the brink of fear . emerson 's god , is in the snow puddles too . stood there on the common , he disappears , becoming nothing as the currents of god flow through him . what is left is just , a transparent eyeball . such transcendent moments are rare , but they reveal an essential connection between nature , god and man . they are one . they also give emerson a proper sense of each individual 's importance , as a part of god . transcendentalism became the name of the movement that grew up around emerson , at this time . another aspect of the epiphany that was to have a profound effect on american literature , was the emphasis on the value of the ordinary . what emerson put forward in essays like `` the american scholar '' and `` the poet '' , was that the american every day , was a proper subject for literature . this was because for emerson , the transcendentalist god is everywhere , and it 's the poet 's job to reveal this . `` there is no object ... '' , he wrote , `` ... so foul that intense light will not make it beautiful . '' `` ... even a corpse has its own beauty . '' this coming from a man who had opened his first wife 's tomb a year after her death ... ... to take a look ! the great american writers , who followed emerson , were liberated by his work to look around and write about what they saw and how they lived , transforming the everyday into a vital symbol of something higher and more elusive . henry david thoreau 's two years at walden pond , became a book that showed the cosmos reflected in the depths of the waters of a mere pond . the poet walt whitman said : `` i was simmering , simmering , simmering ... ... emerson brought me to a boil . '' emily dickinson heard a fly and could write of the other side of death . the novelist herman melville , took a whaling voyage , and made it an allegory of american imperialism and the defiance of nature . in the 20th century , the american critic harold bloom looked back at emerson 's originality and saw in it the origin of : `` the strong tradition of american poets . '' from robert frost and wallace stevens to john ashbery , emerson 's legacy to american literature and culture and indeed to the world , was one of ceaseless invention and forward momentum . as he put it : `` i unsettle all things ... ... no facts are to me sacred , none are profane ... ... i simply experiment an endless seeker with no past at my back . '' people of paul pronouncing his name if you do n't speak german it 's not at all obvious how you 're supposed to say it a safe bet is to start with a hard was a great check writer who has come to own a part of the human emotional spectrum which we can now call the casket desk and which thanks to him where
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by nature , emerson seem to mean the natural world : plants , animals , rocks and sky , but what he really meant was god . emerson was a `` pantheist '' . that is , someone who believe that god exists in every part of creation , from the smallest grain of sand to the stars .
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according to emerson , where did he experience his first pantheistic revelations ?
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diabetes mellitus has been a scourge of the developed world with an estimated 400,000,000 people worldwide suffering from this disease , and 50 % more predicted within twenty years . its early symptoms , which include increased thirst and large volumes of urine , were recognized as far back as 1500 bce in egypt . while the term diabetes , meaning `` to pass through , '' was first used in 250 bce by the greek physician apollonius of memphis , type 1 and type 2 diabetes , associated respectively with youth and obesity , were identified as separate conditions by indian physicians somewhere in the 5th century ce . but despite the disease being known , a diagnosis of diabetes in a human patient would remain tantamount to a death sentence until the early 20th century , its causes unknown . what changed this dire situation was the help of humanity 's longtime animal partner : canis lupus familiaris , domesticated from grey wolves thousands of years ago . in 1890 , the german scientists von mering and minkowski demonstrated that removing a dog 's pancreas caused it to develop all the signs of diabetes , thus establishing the organ 's central role in the disease . but the exact mechanism by which this occurred remained a mystery until 1920 , when a young canadian surgeon named frederick banting and his student , charles best , advanced the findings of their german colleagues . working under professor macleod at the university of toronto , they confirmed that the pancreas was responsible for regulating blood glucose , successfully treating diabetic dogs by injecting them with an extract they had prepared from pancreas tissue . by 1922 , the researchers working with biochemist james collip were able to develop a similar extract from beef pancreas to first treat a 14-year-old diabetic boy , followed by six additional patients . the manufacturing process for this extract , now known as insulin , was eventually turned over to a pharmaceutical company that makes different types of injectable insulin to this day . banting and macleod received the nobel prize for medicine in 1923 for their discovery . but banting chose to share his portion with charles best , for his help in the initial studies involving dogs . but while medical experimentation on animals remains controversial , in this case at least , it was not just a matter of exploiting dogs for human needs . dogs develop diabetes at the rate of two cases per 1,000 dogs , almost the same as that of humans under 20 . most canine cases are of type 1 diabetes , similar to the type that young children develop following immune system destruction of the pancreas , and genetic studies have shown that the dog disease has many similar hallmarks of the human disease . this has allowed veterinarians to turn the tables , successfully using insulin to treat diabetes in man 's best friend for over 60 years . many dog owners commit to managing their dogs ' diabetes with insulin injected twice daily , regimented feedings , and periodic blood measurements using the same home-testing glucose monitors used by human patients . and if the purified pig insulin commonly used for dogs fails to work for a particular dog , the vet may even turn to a formulation of human insulin , bringing the process full circle . after all that dogs have done for us throughout the ages , including their role in a medical discovery that has saved countless human lives , using that same knowledge to help them is the least we could do .
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but while medical experimentation on animals remains controversial , in this case at least , it was not just a matter of exploiting dogs for human needs . dogs develop diabetes at the rate of two cases per 1,000 dogs , almost the same as that of humans under 20 . most canine cases are of type 1 diabetes , similar to the type that young children develop following immune system destruction of the pancreas , and genetic studies have shown that the dog disease has many similar hallmarks of the human disease .
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dogs suffer from type ___ diabetes mellitus at about the same rate as human patients less than 20 years old .
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it 's often said that despite humanity 's many conflicts , we all bleed the same blood . it 's a nice thought but not quite accurate . in fact , our blood comes in a few different varieties . our red blood cells contain a protein called hemoglobin that binds to oxygen , allowing the cells to transport it throughout the body . but they also have another kind of complex protein on the outside of the cell membrane . these proteins , known as antigens , communicate with white blood cells , immune cells that protect against infection . antigens serve as identifying markers , allowing the immune system to recognize your body 's own cells without attacking them as foreign bodies . the two main kinds of antigens , a and b , determine your blood type . but how do we get four blood types from only two antigens ? well , the antigens are coded for by three different alleles , varieties of a particular gene . while the a and b alleles code for a and b antigens , the o allele codes for neither , and because we inherit one copy of each gene from each parent , every individual has two alleles determining blood type . when these happen to be different , one overrides the other depending on their relative dominance . for blood types , the a and b alleles are both dominant , while o is recessive . so a and a gives you type a blood , while b and b gives you type b . if you inherit one of each , the resulting codominance will produce both a and b antigens , which is type ab . the o allele is recessive , so either of the others will override it when they 're paired , resulting in either type a or type b . but if you happen to inherit two os , instructions will be expressed that make blood cells without the a or the b antigen . because of these interactions , knowing both parents ' blood types lets us predict the relative probability of their children 's blood types . why do blood types matter ? for blood transfusions , finding the correct one is a matter of life and death . if someone with type a blood is given type b blood , or vice versa , their antibodies will reject the foreign antigens and attack them , potentially causing the transfused blood to clot . but because people with type ab blood produce both a and b antigens , they do n't make antibodies against them , so they will recognize either as safe , making them universal recipients . on the other hand , people with blood type o do not produce either antigen , which makes them universal donors , but will cause their immune system to make antibodies that reject any other blood type . unfortunately , matching donors and recipients is a bit more complicated due to additional antigen systems , particular the rh factor , named after the rhesus monkeys in which it was first isolated . rh+ or rh- refers to the presence or absence of the d antigen of the rh blood group system . and in addition to impeding some blood transfusions , it can cause severe complications in pregnancy . if an rh- mother is carrying an rh+ child , her body will produce rh antibodies that may cross the placenta and attack the fetus , a condition known as hemolytic disease of the newborn . some cultures believe blood type to be associated with personality , though this is not supported by science . and though the proportions of different blood types vary between human populations , scientists are n't sure why they evolved ; perhaps as protection against blood born diseases , or due to random genetic drift . finally , different species have different sets of antigens . in fact , the four main blood types shared by us apes seem paltry in comparison to the thirteen types found in dogs .
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for blood transfusions , finding the correct one is a matter of life and death . if someone with type a blood is given type b blood , or vice versa , their antibodies will reject the foreign antigens and attack them , potentially causing the transfused blood to clot . but because people with type ab blood produce both a and b antigens , they do n't make antibodies against them , so they will recognize either as safe , making them universal recipients .
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let 's say your name is gilligan , you 've survived a shipwreck and you 're stranded on a desert island . you happen to have been stranded with a medical doctor that has a limited stock of medical supplies . one of your shipmates is in desperate need of a blood transfusion but does n't know his blood type . you do know your blood type . how could you type his blood with your knowledge and limited medical supplies ?
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if you visit a museum with a collection of modern and contemporary art , you 're likely to see works that sometimes elicit the response , `` my cat could make that , so how is it art ? '' a movement called abstract expressionism , also known as the new york school , gets this reaction particularly often . abstract expressionism started in 1943 and developed after the end of world war ii . it 's characterized by large , primarily abstract paintings , all-over compositions without clear focal points , and sweeping swaths of paint embodying and eliciting emotions . the group of artists who are considered abstract expressionists includes barnett newman with his existential zips , willem de kooning , famous for his travestied women , helen frankenthaler , who created soak-stains , and others . but perhaps the most famous , influential , and head-scratching one was jackson pollock . most of his paintings are immediately recognizable . they feature tangled messes of lines of paint bouncing around in every direction on the canvas . and sure , these fields of chaos are big and impressive , but what 's so great about them ? did n't he just drip the paint at random ? ca n't anyone do that ? well , the answer to these questions is both yes and no . while pollock implemented a technique anyone is technically capable of regardless of artistic training , only he could have made his paintings . this paradox relates to his work 's roots in the surrealist automatic drawings of andré masson and others . these surrealists supposedly drew directly from the unconscious to reveal truths hidden within their minds . occasionally , instead of picturing something and then drawing it , they let their hands move automatically and would later tease out familiar figures that appeared in the scribbles . and after pollock moved away from representation , he made drip , or action , paintings following a similar premise , though he developed a signature technique and never looked for images or messages hidden in the works . first , he took the canvas off of the easel and laid it on the floor , a subversive act in itself . then , in a controlled dance , he stepped all around the canvas , dripping industrial paint onto it from stirrers and other tools , changing speed and direction to control how the paint made contact with the surface . these movements , like the surrealist scribbles , were supposedly born out of pollock 's subconscious . but unlike the surrealists , whose pictures represented the mind 's hidden contents , pollock 's supposedly made physical manifestations of his psyche . his paintings are themselves signatures of his mind . in theory , anyone could make a painting that is an imprint of their mind . so why is pollock so special ? well , it 's important to remember that while anyone could have done what he did , he and the rest of the new york school were the ones who actually did it . they destroyed conventions of painting that had stood for centuries , forcing the art world to rethink them entirely . but one last reason why jackson pollock 's work has stayed prominent stems from the specific objects he made , which embody fascinating contradictions . for instance , while pollock 's process resulted in radically flat painted surfaces , the web of painted lines can create the illusion of an infinite layered depth when examined up close . and the chaos of this tangled mess seems to defy all control , but it 's actually the product of a deliberate , though not pre-planned , process . these characteristics made pollock into a celebrity , and within art history , they also elevated him to the mythified status of the genius artist as hero . so rather than evening the playing field for all creative minds , his work unfortunately reinforced a long-standing elitist aspect of art . elitist , innovative , whatever you choose to call it , the history embedded in abstract expressionism is one that no cat , however talented , can claim .
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but one last reason why jackson pollock 's work has stayed prominent stems from the specific objects he made , which embody fascinating contradictions . for instance , while pollock 's process resulted in radically flat painted surfaces , the web of painted lines can create the illusion of an infinite layered depth when examined up close . and the chaos of this tangled mess seems to defy all control , but it 's actually the product of a deliberate , though not pre-planned , process .
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when examined up close , pollock ’ s paintings :
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translator : andrea mcdonough reviewer : bedirhan cinar a couple of years ago i started using twitter , and one of the things that really charmed me about twitter is that people would wake up in the morning and they would say , `` good morning ! '' which i thought , i 'm a canadian , so i was a little bit , i liked that politeness . and so , i 'm also a giant nerd , and so i wrote a computer program that would record 24 hours of everybody on twitter saying , `` good morning ! '' and then i asked myself my favorite question , `` what would that look like ? '' well , as it turns out , i think it would look something like this . right , so we 'd see this wave of people saying , `` good morning ! '' across the world as they wake up . now the green people , these are people that wake up at around 8 o'clock in the morning , who wakes up at 8 o'clock or says , `` good morning ! '' at 8 ? and the orange people , they say , `` good morning ! '' around 9 . and the red people , they say , `` good morning ! '' around 10 . yeah , more at 10 's than , more at 10 's than 8 's . and actually if you look at this map , we can learn a little bit about how people wake up in different parts of the world . people on the west coast , for example , they wake up a little bit later than those people on the east coast . but that 's not all that people say on twitter , right ? we also get these really important tweets , like , `` i just landed in orlando ! ! [ plane sign , plane sign ] '' or , or , `` i just landed in texas [ exclamation point ] ! '' or `` i just landed in honduras ! '' these lists , they go on and on and on , all these people , right ? so , on the outside , these people are just telling us something about how they 're traveling . but we know the truth , do n't we ? these people are show-offs ! they are showing off that they 're in cape town and i 'm not . so i thought , how can we take this vanity and turn it into utility ? so using a similar approach that i did with `` good morning , '' i mapped all those people 's trips because i know where they 're landing , they just told me , and i know where they live because they share that information on their twitter profile . so what i 'm able to do with 36 hours of twitter is create a model of how people are traveling around the world during that 36 hours . and this is kind of a prototype because i think if we listen to everybody on twitter and facebook and the rest of our social media , we 'd actually get a pretty clear picture of how people are traveling from one place to the other , which is actually turns out to be a very useful thing for scientists , particularly those who are studying how disease is spread . so , i work upstairs in the new york times , and for the last two years , we 've been working on a project called , `` cascade , '' which in some ways is kind of similar to this one . but instead of modeling how people move , we 're modeling how people talk . we 're looking at what does a discussion look like . well , here 's an example . this is a discussion around an article called , `` the island where people forget to die '' . it 's about an island in greece where people live a really , really , really , really , really , really long time . and what we 're seeing here is we 're seeing a conversation that 's stemming from that first tweet down in the bottom , left-hand corner . so we get to see the scope of this conversation over about 9 hours right now , we 're going to creep up to 12 hours here in a second . but , we can also see what that conversation looks like in three dimensions . and that three-dimensional view is actually much more useful for us . as humans , we are really used to things that are structured as three dimensions . so , we can look at those little off-shoots of conversation , we can find out what exactly happened . and this is an interactive , exploratory tool so we can go through every step in the conversation . we can look at who the people were , what they said , how old they are , where they live , who follows them , and so on , and so on , and so on . so , the times creates about 6,500 pieces of content every month , and we can model every single one of the conversations that happen around them . and they look somewhat different . depending on the story and depending on how fast people are talking about it and how far the conversation spreads , these structures , which i call these conversational architectures , end up looking different . so , these projects that i 've shown you , i think they all involve the same thing : we can take small pieces of data and by putting them together , we can generate more value , we can do more exciting things with them . but so far we 've only talked about twitter , right ? and twitter is n't all the data . we learned a moment ago that there is tons and tons , tons more data out there . and specifically , i want you to think about one type of data because all of you guys , everybody in this audience , we , we , me as well , are data-making machines . we are producing data all the time . every single one of us , we 're producing data . somebody else , though , is storing that data . usually we put our trust into companies to store that data , but what i want to suggest here is that rather than putting our trust in companies to store that data , we should put the trust in ourselves because we actually own that data . right , that is something we should remember . everything that someone else measures about you , you actually own . so , it 's my hope , maybe because i 'm a canadian , that all of us can come together with this really valuable data that we 've been storing , and we can collectively launch that data toward some of the world 's most difficulty problems because big data can solve big problems , but i think it can do it the best if it 's all of us who are in control . thank you .
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we can look at who the people were , what they said , how old they are , where they live , who follows them , and so on , and so on , and so on . so , the times creates about 6,500 pieces of content every month , and we can model every single one of the conversations that happen around them . and they look somewhat different .
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about how much content does the new york times create every month ?
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