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in the 1950s , a group of ranchers in idaho were baffled when their sheep gave birth to lambs with a singular deformity . mystified by these cyclops sheep , they called in scientists from the u.s. department of agriculture to investigate . the researchers hypothesized that the pregnant ewes had snacked on poisonous birth defect-causing plants . they collected the local flora and fed samples to lab rats , but struggled to replicate the effect . so they decided to directly observe the sheep with one scientist even living with the herd for three summers . after a decade of trial and error , the scientists finally found the culprit , wild corn lilies . the lilies contained an active molecule with six connected rings that they named cyclopamine in reference to the cyclops sheep . they did n't know exactly how cyclopamine caused the defect but told ranchers to steer clear . it took about four decades before a team of biologists , led by professor philip beachy , stumbled upon the answer . his lab was studying a specific gene found in many species , from mice to humans , called the hedgehog gene . it was named by two scientists , who later shared the noble prize for their work , who found that mutating this gene in fruit flies produced pointy spikes like a hedgehog . beachy and his colleagues performed genetic modifications to turn off the hedgehog genes in mice . this resulted in severe defects in the development of their brains , organs , and eyes or , rather , eye . then while perusing a textbook , beachy came across photos of the cyclops sheep and realized what had eluded scientists for four decades . something must have gone awry involving the hedgehog gene . let 's take a step back . genes contain instructions that tell cells what to do and when to do it , and they communicate their directives using proteins . the hedgehog gene itself tells cells to release a so-called hedgehog protein , which kicks off a complex series of cellular signals . here 's how it works in normal healthy development . hedgehog protein latches on to a protein called patched . that inhibits , or holds , patched back , allowing another protein called smoothened to freely signal the cells , telling them where to go and what kind of tissues to become . cyclopamine , say in the form of a delicious corn lily , interrupts this pathway by binding onto smoothened . that locks smoothened up so that it 's unable to send the signals needed to mold the brain into two hemispheres , and form fingers or separate eyes . so even though the hedgehog protein is still doing its job of keeping the way clear for smoothened , cyclopamine blocks smoothened from passing along its chemical message . that settled the science behind the one-eyed sheep , but beachy and his team caught the glimmer of another more beneficial connection . they noted that uncontrolled activation of the smoothened protein was associated with a human syndrome . it 's known as basal cell nevus syndrome , and it predisposes people to certain cancers . the scientists proposed putting cyclopamine 's smoothened binding powers to good use as a treatment for these cancers , as long as the patient was n't pregnant . unfortunately , researchers eventually found that cyclopamine causes negative side effects , and its chemical properties make it difficult to work with . but they did discover that closely related molecules are safe and effective , and two of these drugs were approved in 2012 and 2015 as skin cancer medicines . when those farmers first saw the cyclops sheep , they could have chalked it up to a freak genetic mutation and walked away . instead , their decision to investigate turned a mystery into medicine showing that sometimes there 's more than meets the eye .

in the 1950s , a group of ranchers in idaho were baffled when their sheep gave birth to lambs with a singular deformity . mystified by these cyclops sheep , they called in scientists from the u.s. department of agriculture to investigate . the researchers hypothesized that the pregnant ewes had snacked on poisonous birth defect-causing plants .

if you were a scientist called in to investigate the cyclops sheep , what questions would you ask the ranchers ?

in this short video , we 're going to show you how we constructed and animated a pop-up book to explain earth 's tectonic plates . the supercontinent pangaea broke apart 200,000,000 years ago , but the pieces have n't stopped shifting . although with animation we can show this movement easily with drawings , we thought it 'd be more interesting to depict gigantic sliding slabs of rock using a tangible object that also moves and shifts . and the pop-up book idea was born . ( music ) to make your own pop-up book , you 'll need some basic paper tools , such as scissors , an x-acto knife , glue , double-sided scotch tape , a ruler , a bone folder or other creasing tool , and , of course , some paper . for this lesson , we first determined the visual style by making illustrations and deciding on the overall design , colors , shapes and elements we wanted on each page , or spread . you can have more detailed illustrations , but we wanted to illustrate this lesson simply by playing with shapes and colors . when you visualize your pop-up and choose a visual style , you will want to make a bunch of good old pencil sketches on paper and plan each movement for each spread . plan as much as you can : all the basic shapes and how they connect and how you want them to move , which parts you want to pop-up first . challenge yourself , and explore multiple possibilities of how your main element on the spread can pop up . for the next step , make a mock-up spread and see if your masterful paper engineering ideas translate from a sketch to the actual prototype . instead of using fancy paper , start with the cheap stuff and allow yourself to make mistakes and adjustments . this prototype lets you see how your preliminary sketches will come to life . you will want to first draw all individual parts on a single sheet , including all your main pieces , all the supporting pieces and the folds . you may be surprised that there are only two types of folds that can make your elements pop up the way you want : a step fold and a v-fold . here , you can see how we used a step fold to make each layer of the earth step out . then , cut all your individual elements and assemble using glue or double-sided scotch tape . ( music ) through trial and error , make sure that all the elements , shapes and placements are moving the way you imagined , and that they fold properly when closed and opened . ( music ) once your prototype is tested and complete , you can proceed to making the final product in color . draw or paint on your main pop-up elements as you see fit . for this lesson , we decided to just play with simple shapes in different colors to create the world of shifting continents we imagined . ( music ) when we were planning each spread , we knew we wanted some elements to move independently of the typical pop-up book using slight manipulations and animations . we had to plan well , but also use a few tricks . as always , when you 're making stop-motion , you may have to be creative and use all sorts of unusual tools and props to achieve the effect that you want . in this shot , the birds had to fly across and off the edge of the book , so we used fun-tak to move the clouds across the page . once they left the page , they had to be trimmed to get the illusion they flew off . when the pages of the book close at the end , we had to flip each page , supporting it in each position long enough to be photographed as an individual frame . we used binder clips , wedges , fun-tak , and almost every handy little thing you can think of . once all the individual frames were photographed , we put them all together and composited to make our pop-up book look like it 's moving on its own . so now , think of a special occasion where you can surprise someone with your own unique pop-up card , or an entire story that you want to tell , and start plotting the ins and outs of your pop-up book .

although with animation we can show this movement easily with drawings , we thought it 'd be more interesting to depict gigantic sliding slabs of rock using a tangible object that also moves and shifts . and the pop-up book idea was born . ( music ) to make your own pop-up book , you 'll need some basic paper tools , such as scissors , an x-acto knife , glue , double-sided scotch tape , a ruler , a bone folder or other creasing tool , and , of course , some paper .

what artistic elements play key roles in creating a pop-up book ?

they say the pen is mightier than the sword , and authorities have often agreed . from outlawed religious tracts and revolutionary manifestos to censored and burned books , we know the potential power of words to overturn the social order . but as strange as it may seem , some numbers have also been considered dangerous enough to ban . our distant ancestors long counted objects using simple tally marks . but as they developed agriculture and began living together in larger groups , this was no longer enough . as numbers grew more complex , people began not just using them , but thinking about what they are and how they work . and by 600 b.c.e . in ancient greece , the study of numbers was well-developed . the mathematician pythagoras and his school of followers found numerical patterns in shapes , music , and the stars . for them , mathematics held the deepest secrets of the universe . but one pythagorean named hippasus discovered something disturbing . some quantities , like the diagonal of a square with sides of length one could n't be expressed by any combination of whole numbers or fractions , no matter how small . these numbers , which we call irrational numbers , were perceived as a threat to the pythagorean 's notion of a perfect universe . they imagined a reality that could be described with rational , numerical patterns . historians write that hippasus was exhiled for publicizing his findings , while legends claim he was drowned as punishment from the gods . while irrational numbers upset philosophers , later mathematical inventions would draw attention from political and religious authorities , as well . in the middle ages , while europe was still using roman numerals , other cultures had developed positional systems that included a symbol for zero . when arab travelers brought this system to the bustling maritime cities of italy , its advantages for merchants and bankers was clear . but the authorities were more wary . hindu-arabic numerals were considered easier to forge or alter , especially since they were less familiar to customers than to merchants . and the concept of zero opened the door to negative numbers and the recording of debt at a time when moneylending was regarded with suspicion . in the 13th century , florence banned the use of hindu-arabic numerals for record keeping . and though they soon proved too useful to ignore , controversies over zero and negative numbers continued for a long time . negative numbers were dismissed as absurd well into the 19th century . and prominent mathematicians , like gerolamo cardano , avoided using zero , even though it would have made it much easier to find solutions to cubic and the quartic equations . even today it 's illegal to use some numbers for different reasons . some are banned because of what they represent . for example , governments have prohibited the display of numbers that have symbolic meaning , such as the date of a revolution or connections to oppositional political figures or parties . other numbers are potentially illegal because of the information they carry . just about any information , whether text , image , video , or executable programs can be translated into a string of numbers . but this means that protected information , whether copyrights , proprietary materials , or state secrets can also be represented as numbers , so possessing or publishing these numbers may be treated as a criminal offense . this idea gathered attention in 2001 when code that could be used to decrypt dvds was widely shared and distributed in the form of a large prime number . the idea of illegal numbers may sound absurd , but like words , written numbers are a way of expressing concepts and information . and in a world where calculations and algorithms shape more and more of our lives , the mathematician 's pencil grows stronger by the day .

these numbers , which we call irrational numbers , were perceived as a threat to the pythagorean 's notion of a perfect universe . they imagined a reality that could be described with rational , numerical patterns . historians write that hippasus was exhiled for publicizing his findings , while legends claim he was drowned as punishment from the gods .

what is a rational number ?

humans know the surprising prick of a needle , the searing pain of a stubbed toe , and the throbbing of a toothache . we can identify many types of pain and have multiple ways of treating it . but what about other species ? how do the animals all around us experience pain ? it 's important that we find out . we keep animals as pets , they enrich our environment , we farm many species for food , and we use them in experiments to advance science and human health . animals are clearly important to us , so it 's equally important that we avoid causing them unnecessary pain . for animals that are similar to us , like mammals , it 's often obvious when they 're hurting . but there 's a lot that is n't obvious , like whether pain relievers that work on us also help them . and the more different an animal is from us , the harder it is to understand their experience . how do you tell whether a shrimp is in pain ? a snake ? a snail ? in vertebrates , including humans , pain can be split into two distinct processes . in first , nerves and the skin sense something harmful and communicate that information to the spinal cord . there , motor neurons activate movements that make us rapidly jerk away from the threat . this is the physical recognition of harm called nociception , and nearly all animals , even those with very simple nervous systems , experience it . without this ability , animals would be unable to avoid harm and their survival would be threatened . the second part is the conscious recognition of harm . in humans , this occurs when the sensory neurons in our skin make a second round of connections via the spinal cord to the brain . there , millions of neurons in multiple regions create the sensations of pain . for us , this is a very complex experience associated with emotions like fear , panic , and stress , which we can communicate to others . but it 's harder to know exactly how animals experience this part of the process because most them ca n't show us what they feel . however , we get clues from observing how animals behave . wild , hurt animals are known to nurse their wounds , make noises to show their distress , and become reclusive . in the lab , scientists have discovered that animals like chickens and rats will self-administer pain-reducing drugs if they 're hurting . animals also avoid situations where they 've been hurt before , which suggests awareness of threats . we 've reached the point that research has made us so sure that vertebrates recognize pain that it 's illegal in many countries to needlessly harm these animals . but what about other types of animals like invertebrates ? these animals are n't legally protected , partly because their behaviors are harder to read . we can make good guesses about some of them , like oysters , worms , and jellyfish . these are examples of animals that either lack a brain or have a very simple one . so an oyster may recoil when squirted with lemon juice , for instance , because of nociception . but with such a simple nervous system , it 's unlikely to experience the conscious part of pain . other invertebrate animals are more complicated , though , like the octopus , which has a sophisticated brain and is thought to be one of the most intelligent invertebrate animals . yet , in many countries , people continue the practice of eating live octopus . we also boil live crawfish , shrimp , and crabs even though we do n't really know how they 're affected either . this poses an ethical problem because we may be causing these animals unnecessary suffering . scientific experimentation , though controversial , gives us some clues . tests on hermit crabs show that they 'll leave an undesirable shell if they 're zapped with electricity but stay if it 's a good shell . and octopi that may originally curl up an injured arm to protect it will risk using it to catch prey . that suggests that these animals make value judgements around sensory input instead of just reacting reflexively to harm . meanwhile , crabs have been known to repeatedly rub a spot on their bodies where they 've received an electric shock . and even sea slugs flinch when they know they 're about to receive a noxious stimulus . that means they have some memory of physical sensations . we still have a lot to learn about animal pain . as our knowledge grows , it may one day allow us to live in a world where we do n't cause pain needlessly .

we 've reached the point that research has made us so sure that vertebrates recognize pain that it 's illegal in many countries to needlessly harm these animals . but what about other types of animals like invertebrates ? these animals are n't legally protected , partly because their behaviors are harder to read .

what behaviors have researchers measured in invertebrates after injury ? are these similar or different to those observed in vertebrate animals ?

would you believe that walruses , rattlesnakes , and parakeets all once lived in the same house ? let 's go back about 350 million years . look around . steamy swamps and rain forests of horsetails and ferns cover the region . amphibians are the dominant land vertebrates . they range in size from newts to crocodiles . and all require water to do their egg laying . if they do n't go to the water , their shell-less , jelly-like eggs will dry out . because of this hazard , they spend most of their time living in or near fresh water . that is , until a breakthrough in evolution changes everything : the amniotic egg . the amniotic egg is shelled , waterproof , and can be laid on dry land . it is produced by the amniotes , a new group of animals named after their revolutionary egg . the first amniote is a tetrapod , a four-legged animal , resembling a small lizard . while some amphibians can walk around on land and bury their eggs in wet soil or highly humid areas , nothing before the amniotes has the ability to lay its eggs on completely dry land . because of this evolved egg , the amniotes are the first animals with the ability to live a fully terrestrial life . but , despite their move inland , the amniotes have not abandoned their pond-dwelling upbringing . in fact , the amniotic egg brings the pond with them by enclosing the aquatic environment within its shell . this is achieved by four main upgrades that are unique to amniotic eggs . let 's take a closer look . the first development is the most obvious : the egg 's protective shell . it 's tough but flexible , and has a leathery surface , still seen in reptile eggs today . the shell protects the eggs from predators , bacteria , damage , and drying out . but , unlike the walls of a fish tank , the shell of the amniotic egg is porous , allowing oxygen to pass through so that the growing amniote inside does n't suffocate . the next two developments are two separate membranes that work together like a pair of lungs . they bring oxygen into the embryo while removing carbon dioxide . the first is the chorion , which is the protective layer that oxygen passes through after entering the shell 's tiny pores . you may recognize the chorion as the thin skin you peel away on a hard boiled egg . think of this waterproof membrane as the in and out doors of the egg . it 's the entrance for oxygen and exit for carbon dioxide . the membrane working with the chorion is the allantois . if the chorion is the doors , then the allantois is essentially the lobby of the building . it directs the oxygen and carbon dioxide while simultaneously storing unneeded waste from the embryo . the chorion and the allantois make sure the embryo has everything it needs and gets rid of anything it does n't . the last and perhaps the most important development is the amnion , the membrane for which the egg is named . the amnion is also contained within the chroion and holds the fluid in which the embryo floats . because it has left the watery world of the amphibians , the amnion is necessary for preventing the embryo from drying out . it is the transportable pond that allows the amniote to lay the egg on dry land . its fluid also protects the embryo from any collisions or rough landings , like a shock absorber on your bike or car . together , the shell and these four membranes create a safe , watery environment for the embryo to grow and develop . the new amniote offspring will continue the process of vertebrate evolution as it explores new land away from the water . they will spend the next million years splitting into two distinct groups : the synapsids and sauropsids . synapsida is the group of animals that contain mammals , while sauropsida is the group that contains reptiles , birds , and dinosaurs . these two amniotic groups collectively contain the walruses , rattlesnakes , and parakeets we know today . like a family reunion , with relatives of every shape and size , coming together from different corners of the earth , these animals can all call one place home : the amniotic egg .

in fact , the amniotic egg brings the pond with them by enclosing the aquatic environment within its shell . this is achieved by four main upgrades that are unique to amniotic eggs . let 's take a closer look .

the chorion of amniotic eggs functions in :

in 1962 , a cave explorer named michel siffre started a series of experiments where he isolated himself underground for months without light or clocks . he attached himself to electrodes that monitored his vital signs and kept track of when he slept and ate . when siffre finally emerged , the results of his pioneering experiments revealed that his body had kept to a regular sleeping-waking cycle . despite having no external cues , he fell asleep , woke up , and ate at fixed intervals . this became known as a circadian rhythm from the latin for `` about a day . '' scientists later found these rhythms affect our hormone secretion , how our bodies process food , and even the effects of drugs on our bodies . the field of sciences studying these changes is called chronobiology . being able to sense time helps us do everything from waking and sleeping to knowing precisely when to catch a ball that 's hurtling towards us . we owe all these abilities to an interconnected system of timekeepers in our brains . it contains the equivalent of a stopwatch telling us how many seconds elapsed , a clock counting the hours of the day , and a calendar notifying us of the seasons . each one is located in a different brain region . siffre , stuck in his dark cave , relied on the most primitive clock in the suprachiasmatic nucleus , or scn of the hypothalamus . here 's the basics of how we think it works based on fruitfly and mouse studies . proteins known as clk , or clock , accumulate in the scn throughout the day . in addition to activating genes that tell us to stay awake , they make another protein called per . when enough per accumulates , it deactivates the gene that makes clk , eventually making us fall asleep . then , clock falls low , so per concentrations also drop again , allowing clk to rise , starting the cycle over . there are other proteins involved , but our day and night cycle may be driven in part by this seesaw effect between clk by day and per by night . for more precision , our scns also rely on external cues like light , food , noise , and temperature . we called these zeitgebers , german for `` givers of time . '' siffre lacked many of these cues underground , but in normal life , they fine tune our daily behavior . for instance , as natural morning light filters into our eyes , it helps wake us up . traveling through the optic nerve to the scn , it communicates what 's happening in the outside world . the hypothalamus then halts the production of melatonin , a hormone that triggers sleep . at the same time , it increases the production of vasopressin and noradrenaline throughout the brain , which help control our sleep cycles . at about 10 am , the body 's rising temperature drives up our energy and alertness , and later in the afternoon , it also improves our muscle activity and coordination . bright screens at night can confuse these signals , which is why binging on tv before bed makes it harder to sleep . but sometimes we need to be even more precise when telling the time , which is where the brain 's internal stopwatch chimes in . one theory for how this works involves the fact that communication between a given pair of neurons always takes roughly the same amount of time . so neurons in our cortex and other brain areas may communicate in scheduled , predictable loops that the cortex uses to judge with precision how much time has passed . that creates our perception of time . in his cave , siffre made a fascinating additional discovery about this . every day , he challenged himself to count up to 120 at the rate of one digit per second . over time , instead of taking two minutes , it began taking him as long as five . life in the lonely , dark cave had warped siffre 's own perception of time despite his brain 's best efforts to keep him on track . this makes us wonder what else influences our sense of time . and if time is n't objective , what does that mean ? could each of us be experiencing it differently ? only time will tell .

so neurons in our cortex and other brain areas may communicate in scheduled , predictable loops that the cortex uses to judge with precision how much time has passed . that creates our perception of time . in his cave , siffre made a fascinating additional discovery about this .

how can light perception at night affect our neurotransmitters ?

tellurium is , is quite a nice element here . i shall pick it up carefully . tellurium . you ’ ve never had anything to do with this ? nothing to do with it in my life . so this is a new one for me . this is tellurium powder . so let ’ s see what ’ s inside the vial . so as we open it and tap out the glass vial . this one is going to be stubborn . this bell shape here is a sample of tellurium . the reason…shall i hold it for you ? … so , a sample of tellurium . i ’ m slightly cagey about touching this because as i think i explained with selenium that , if you ingest tellurium into the body it can get into your sweat and make you smell enough to really drive people mad . and these crystals like this one can be cut up and mounted into a piece of apparatus like this . so a chemist won ’ t deal with all the elements on the periodic table in his career normally . no , no , very few chemists will deal with more than perhaps a handful of different elements . so this is the tellurium and this is , again , this is very high standard material . 3 grams of the tellurium material and you can see it ’ s a very dark powder at the bottom of the vial . it was used in this piece of apparatus to shine in an infrared laser that ’ s like a heat ray at one frequency and it came out as twice the frequency . so you can use it to change the effect of the lasers . unfortunately the guy doing it didn ’ t make a very good job of it and you can see he ’ s completely burnt the surface of this piece of tellurium . so the main use of tellurium is as components like this for laser optics and it ’ s not widely used in the chemical industry or similar areas .

i shall pick it up carefully . tellurium . you ’ ve never had anything to do with this ?

tellurium was named after ...

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 .

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 .

which is not a form of light ?

there are some shark species that seem to do okay in aquariums . you ’ ll see a lot of nurse sharks , zebra sharks , some reef sharks and sand tiger sharks . but not the great white . for decades , aquariums have tried to contain the world ’ s largest predatory fish . institutions like marineland , seaworld and the steinhart aquarium repeatedly took in white sharks during the 1970s , 80s and 90s , at times drawing huge crowds . but they never lasted long . some needed help swimming . none of them would eat . the longest one lasted was just 16 days . a 1984 report by the steinhart aquarium put it this way : `` in most cases it could be said that all these captive sharks were merely in the process of dying , with some taking longer than others . '' they had constructed an elaborate transport tank with a harness and iv fluids , but still couldn ’ t keep the sharks alive . it wasn ’ t until 2004 that the monterey bay aquarium proved that it was possible to keep white sharks for at least six months . it took a massive effort , and no one ’ s done it since . jon hoech : our approach was one of sort of a systematic , logical sequence of things leading up to our success and it started with designing a tank . the monterey bay aquarium had a million gallon , egg-shaped tank , 35 feet deep , designed for open-ocean animals like tuna and sharks . so you need a big tank . you also need a small shark . adult great whites reach 15 feet on average . the monterey bay aquarium nabbed one in 2004 that was 4 feet , 4 inches , less than a year old . that made it easier to move and easier to keep . jon hoech : when they ’ re young they feed on fish . and as they get older they transition to feeding more on mammals . and so we were targeting the age bracket where we knew we were more able to feed their natural diet . and once they collected the shark , they didn ’ t take it straight to the aquarium . instead , the monterey bay team set up a 4 million gallon pen right there in the ocean . that way they could monitor the shark and see if it would feed before they moved it into a transport tank to travel from southern california where the sharks were born up to the aquarium . sharks , like all fish , need to have water continually passing through their gills in order to get oxygen . most species can open and close their mouths to pump the water through . but white sharks and a couple dozen other species don ’ t do that . to breathe , they have to move forward through the water with their mouths open . that ’ s why white sharks start to weaken as soon as they ’ re caught in a net . and that ’ s why they needed a custom built transport tank with mobile life support . jon hoech : everything from oxygen sensors and video cameras and lighting and filtration systems that were needed for what turned out to roughly be 9 to 11 hour transport time . aquarium attendance jumped 30 percent while the shark was on display . after 6 and a half months , they decided to release it because it had killed 2 other sharks . over the next 6 years , the aquarium displayed 5 more baby white sharks - some they paid fishermen to hand over , some they caught themselves . their stays ranged from just 11 days up to 5 months . the monterey bay aquarium had succeeded in doing what no one else could . but it did take a toll on the sharks . they developed visible sores from bumping into the sides of the tank . sean van sommeran : we actually snuck in with photographers and took pictures of the sharks as they were beginning to attrit and fail due to the constant scraping against the walls basically . as we viewed it , it was a vase of flowers that would be kept for the visitors . historically , aquariums kept sharks that lived near the seabed or near reefs . that makes sense - it ’ s easier to recreate those habitats in a tank . but in recent decades , aquariums have wanted to bring in bigger , more pelagic sharks , those that spend time roaming the open ocean . they ’ ve even been able to exhibit the largest shark in the world , the whale shark , if they have a big enough tank . but pelagic sharks are used to being able to swim long distances without obstructions , changing directions only as they please . so the faster-moving sharks like the white shark , mako shark , and blue shark , they have trouble with walls when they ’ re put in a tank . that ’ s what was happening with the monterey bay aquarium ’ s sixth white shark in 2011 . they decided to release it after 55 days and its tracking tag revealed that the shark died shortly after being released . they ’ re not sure why . but since then , they haven ’ t tried bring in another great white shark . jon hoech : it ’ s just a very very very resource intensive program and we felt like we had accomplished our goal of introducing the general public to a live white shark . it took a huge , carefully planned system to keep a white shark alive . and even then , the sharks didn ’ t quite fit there . we can ’ t seem to stop trying though . earlier this year , an 11.5-foot great white shark was taken to an aquarium in okinawa , japan after getting caught in a fisherman 's net . it was the only adult white shark ever to be put on display , and within 3 days it was dead . i wanted show you a great resource online called the biodiversity heritage library - it ’ s the product of a couple dozen museums and libraries all agreeing to scan millions of pages from books related to biodiversity . they ’ ve got a bunch of great albums on flickr , including one that 's all about sharks . some of these go back to the 16th and 17th centuries , back when the naturalists used to call sharks “ sea dogs ” which is funny because as we now know sharks were roaming the oceans for about 300 million years before the first mammals showed up .

there are some shark species that seem to do okay in aquariums . you ’ ll see a lot of nurse sharks , zebra sharks , some reef sharks and sand tiger sharks . but not the great white . for decades , aquariums have tried to contain the world ’ s largest predatory fish .

name at least two reasons why it is preferable for aquariums to try to capture and display young ( as opposed to adolescent or full-grown ) great white sharks .

yeah . hey it 's me destin , welcome back to smarter every day . so i 've seen enough videos on the internet of a mantis shrimp punching to have a good idea of what 's going on , but i do n't understand it , like at the mechanical level . so today on smarter every day my sister has volunteered to model three seemingly unrelated objects to help us understand this a little bit better . but first , let 's go to james cook university and watch one punch in slow motion . ok where are we going ? -we 're gon na we 're gon na go to a place called yorkeys knob . - shut up ! - that 's the name of it . - to get some crabs . - we 're not ! - from yorkeys knob . ( destin ) [ laughs ] i was hoping i could use that.. but ... i ca n't . - it 's true , the place is called yorkeys knob . ( destin ) you were n't lying . so yorkeys knob , now i have to find crabs . - that one . that 's a good one . grab that one . got him ? -got him . - there you go . crabs in test tubes . ( destin ) i have to say , i 've never seen that before . - it works . it 'll be cool . so what we 'll do is we 'll take one of the test tubes with the crab in it , we 'll put the test tube down here which will keep the crab there . he 'll come out and go.. bang.. hit the crab and smash the test tube . ( destin ) really ? so the mantis shrimp is.. it 's a peacock mantis shrimp . - yep . - look at that joker . it 's pretty awesome . hey do n't they see more colors than any other animal ? - yeah . they 've got incredible vision and their eyes are setup in parts of three . so the top bits look in a different part from the middle , which look at a different part from the bottom . - kind of like the fovea on our eyes is different from.. - yeah . - ok. - out we come . move little crab . [ loud click ] - bang ! - it triggered . - pull him out . [ bang ] [ breaking glass ] ( destin ) yeah , that 's crazy . so let 's back it up and watch again and you 'll notice that there 's a cavitation bubble generated at the exact point of impact . ok first of all , a mantis shrimp is n't even a shrimp . it 's actually a stomatopod . we call it a shrimp because it kinda looks like it , but we also call it a mantis because it 's similar to a preying mantis with its forearms . they have similar hunting strategies . dr seymour says that punch is so fast that it ca n't be accomplished by muscle movement alone , there has to be something else going on , which brings up sheila patek . believe it or not , dr patek has determined that the shape of this potato chip is the secret to the punch of the mantis shrimp . seriously . this shape is called a hyperbolic paraboloid , and if you 've ever taken calculus you 've seen it . it 's basically a saddle shape and they 're super strong . this saddle is located on top of the smasher , and the stomatopod uses his muscles to compress it like a spring and he holds it back with a latch mechanism . he then releases this potential energy and it drives the club forward at a much higher velocity than would be possible with muscle alone . so the next time you eat one of these remember there 's another animal eating with the same shape you are , only he 's doing it at the bottom of the ocean and he 's got that shape integrated into the top of his arm . if you 've ever played with a vice clamp before , you 've seen this type of mechanism . you can slowly clamp down on the tool , which uses a cam-over action to lock it in place , and if you have it set right and squeeze it hard , you store mechanical strain energy . when you trip the latch the energy 's released and the arm flies forward real fast , but think about this . mantis shrimp use their little clubber to break open shells that are really hard right ? so why does the shell break and the club does n't ? let 's watch another clip . this is dr seymour feeding a crab to the stomatopod except this time there 's no test tube . - it 's flicking the.. it 's flicking the rock . ohhhh ! - did you get it ? - dunno , might have . - ohhhh i feel for that crab . [ laughs ] [ bang ] ( destin ) watch again closer and see if you can see the saddle release the energy . - look at that . - good grief . snapped it straight in half . we 're talking about serious forces here . in engineering we take two materials and we combine them together into composites to make them stronger . for example plywood is made of many layers of wood with the fibers oriented in two different directions . mantis shrimps however take this to the next level with an organic polymer called chitin . at the wyss institute for biologically inspired engineering at harvard , they determined that these fibers are n't rotated only in two principle directions like plywood , it 's an entire helix , which gives the structure strength in many different directions . these strands are then bonded together in a mineralized matrix which makes the whole thing an incredibly strong smasher . but it gets crazier than that . the team put a section of the smasher in a synchrotron so they could analyze the material makeup . a synchrotron ! that 's like a particle accelerator . this is crazy science . they bombarded it hundreds of times to understand the density and the local orientation of the crystals in the material , and guess what . they found that the crystals near the surface were oriented perpendicular to the impact site and that orientation changed as we move away from the impact site . basically the material changes composition and strength at different locations on the inside . the impact surface is incredibly hard , but the internal structure transitions smoothly to allow the distribution of a huge impulse load throughout the rest of that structure so it can punch stuff all day long without breaking . so instead of a normal composite like plywood , which are identical layers stacked up and glued together , a mantis shrimp club is a variable composite , meaning you can vary the material makeup and the strength orientation wherever you need it . this is an incredibly smart way to design a system . in summary , i want you to love the mantis shrimp . i do n't want you to love it just because of the mechanics of how it throws the punch . not because of the chemistry of the variable composition of the crystalline structure . the optics.. it can see circularly polarized light . this is an incredible , incredible animal , and i want you to think about it every time you eat a chip like this . can you do that for me ? ok i hope you enjoyed learning how mantis shrimp club . it 's all about the hyperbolic paraboloid , or as my cal 3 teacher taught me , hyperbowic pawabawoid . anyway , i 'm destin , you 're getting smarter every day . if you 're interested in supporting the crazy trips i do , please consider supporting on audible . audible.com/smarter . you can get any audiobook you want . ( i apologize if you 're deaf ... it makes no sense for you to support via audible . ) i listened to 20,000 leagues under the sea when i did this series because i wanted to learn more about marine life . jules verne nailed it . 20,000 leagues under the sea , audible.com/smarter . thank you so much for your support . i 'll leave a link in the video description . i 'm destin , you 're getting smarter every day , have a good one . it 's derek ! he video bombed me . [ laugh ] ( destin ) ho ! - [ laughs ] we could bring the lighting down on the chip please . perfect . [ laughs ] that was really dumb . ( destin ) which is why i think i 'm gon na use it .

( destin ) really ? so the mantis shrimp is.. it 's a peacock mantis shrimp . - yep .

how is the mantis shrimp able to to break strong shells and not damage itself ?

where the sidewalk ends , by shel silverstein . there is a place where the sidewalk ends and before the street begins , and there the grass grows soft and white , and there the sun burns crimson bright , and there the moon-bird rests from his flight to cool in the peppermint wind . let us leave this place where the smoke blows black and the dark street winds and bends . past the pits where the asphalt flowers grow we shall walk with a walk that is measured and slow , and watch where the chalk-white arrows go to the place where the sidewalk ends . yes we 'll walk with a walk that is measured and slow , and we 'll go where the chalk-white arrows go , for the children , they mark , and the children , they know the place where the sidewalk ends .

where the sidewalk ends , by shel silverstein . there is a place where the sidewalk ends and before the street begins , and there the grass grows soft and white , and there the sun burns crimson bright , and there the moon-bird rests from his flight to cool in the peppermint wind .

do you think the lego sculptures adequately illustrated the poem ? why or why not ? if not , what do you think would have been a more fitting medium ?

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 .

so far , so good . but that space-time diagram represents andrew 's perspective . what does it look like to me ?

why does light have to appear at the same angle when drawn on a space-time diagram ?

hi , i 'm adam cole . this week we 've got a question from lulu miller , the host of npr 's invisibilia podcast : how old are our bodies actually ? because if you think about how we 're constantly being regenerated our physical matter is being shed and replenished ... what actually remains ? good question , lulu ! well , your hair obviously does n't remain the same and i 'm not just talking about the style each hair on your head is replaced every 2 to 7 years a hundred hairs fall out every day and new ones grow back in their place and look at your fingernails - they 're completely new every six months or so it turns out it 's just a matter of time before almost every part of your body refreshes itself in a similar way the lining of your stomach and intestines gets pretty beat up -- it 's constantly exposed to acid and bile and so those cells get replaced every few days every few weeks , your outer layer of skin is completely renewed every four months you have a fresh army of red blood cells a hundred million new cells are born every minute and a hundred million old cells are destroyed it 's actually the breakdown products of these red blood cells that turn your bruises and urine yellow every 10 years , you 've got a new skeleton a special team of cells breaks down old bone and another builds new bone every 15 years your muscles are refreshed you might think you gain and lose fat cells when you gain and lose weight but the actually just get bigger and smaller over the course of 25 years though , most of them turn over but there are a few things that stick around for your entire life about half of your heart stays with you from birth to death because those cells are replaced very slowly certain parts of your brain add a few new neurons over the course of your life but the vast majority of your neurons developed before you were born it 's the connections between those neurons -- the circuits that store memories -- that are constantly changing and there 's one more part of you that lasts your whole life months before you were born , a little cluster of cells stretched and filled themselves with transparent protein as you grew , even after birth , more and more fibers were added , but that center endured this is your lens the window through which you are watching this video right now and its core has remained the same since the moment you first opened your eyes so how old is your body really ? some of it is brand-new and some of it is as old as you are to learn how scientists figured all this out , check out our post at skunkbear.tumblr.com and listen to invisibilia -- the latest episode is about whether or not personality persists throughout your entire life if you have science questions send them our way and please subscribe to our channel !

good question , lulu ! well , your hair obviously does n't remain the same and i 'm not just talking about the style each hair on your head is replaced every 2 to 7 years a hundred hairs fall out every day and new ones grow back in their place and look at your fingernails - they 're completely new every six months or so it turns out it 's just a matter of time before almost every part of your body refreshes itself in a similar way the lining of your stomach and intestines gets pretty beat up -- it 's constantly exposed to acid and bile and so those cells get replaced every few days every few weeks , your outer layer of skin is completely renewed every four months you have a fresh army of red blood cells a hundred million new cells are born every minute and a hundred million old cells are destroyed it 's actually the breakdown products of these red blood cells that turn your bruises and urine yellow every 10 years , you 've got a new skeleton a special team of cells breaks down old bone and another builds new bone every 15 years your muscles are refreshed you might think you gain and lose fat cells when you gain and lose weight but the actually just get bigger and smaller over the course of 25 years though , most of them turn over but there are a few things that stick around for your entire life about half of your heart stays with you from birth to death because those cells are replaced very slowly certain parts of your brain add a few new neurons over the course of your life but the vast majority of your neurons developed before you were born it 's the connections between those neurons -- the circuits that store memories -- that are constantly changing and there 's one more part of you that lasts your whole life months before you were born , a little cluster of cells stretched and filled themselves with transparent protein as you grew , even after birth , more and more fibers were added , but that center endured this is your lens the window through which you are watching this video right now and its core has remained the same since the moment you first opened your eyes so how old is your body really ? some of it is brand-new and some of it is as old as you are to learn how scientists figured all this out , check out our post at skunkbear.tumblr.com and listen to invisibilia -- the latest episode is about whether or not personality persists throughout your entire life if you have science questions send them our way and please subscribe to our channel !

what is a part of your body that has remained intact since before you were born ?

the dna in just one of your cells gets damaged tens of thousands of times per day . multiply that by your body 's hundred trillion or so cells , and you 've got a quintillion dna errors everyday . and because dna provides the blueprint for the proteins your cells need to function , damage causes serious problems , such as cancer . the errors come in different forms . sometimes nucleotides , dna 's building blocks , get damaged , other times nucleotides get matched up incorrectly , causing mutations , and nicks in one or both strands can interfere with dna replication , or even cause sections of dna to get mixed up . fortunately , your cells have ways of fixing most of these problems most of the time . these repair pathways all rely on specialized enzymes . different ones respond to different types of damage . one common error is base mismatches . each nucleotide contains a base , and during dna replication , the enzyme dna polymerase is supposed to bring in the right partner to pair with every base on each template strand . adenine with thymine , and guanine with cytosine . but about once every hundred thousand additions , it makes a mistake . the enzyme catches most of these right away , and cuts off a few nucleotides and replaces them with the correct ones . and just in case it missed a few , a second set of proteins comes behind it to check . if they find a mismatch , they cut out the incorrect nucleotide and replace it . this is called mismatch repair . together , these two systems reduce the number of base mismatch errors to about one in one billion . but dna can get damaged after replication , too . lots of different molecules can cause chemical changes to nucleotides . some of these come from environmental exposure , like certain compounds in tobacco smoke . but others are molecules that are found in cells naturally , like hydrogen peroxide . certain chemical changes are so common that they have specific enzymes assigned to reverse the damage . but the cell also has more general repair pathways . if just one base is damaged , it can usually be fixed by a process called base excision repair . one enzyme snips out the damaged base , and other enzymes come in to trim around the site and replace the nucleotides . uv light can cause damage that 's a little harder to fix . sometimes , it causes two adjacent nucleotides to stick together , distorting the dna 's double helix shape . damage like this requires a more complex process called nucleotide excision repair . a team of proteins removes a long strand of 24 or so nucleotides , and replaces them with fresh ones . very high frequency radiation , like gamma rays and x-rays , cause a different kind of damage . they can actually sever one or both strands of the dna backbone . double strand breaks are the most dangerous . even one can cause cell death . the two most common pathways for repairing double strand breaks are called homologous recombination and non-homologous end joining . homologous recombination uses an undamaged section of similar dna as a template . enzymes interlace the damaged and undamgaed strands , get them to exchange sequences of nucleotides , and finally fill in the missing gaps to end up with two complete double-stranded segments . non-homologous end joining , on the other hand , does n't rely on a template . instead , a series of proteins trims off a few nucleotides and then fuses the broken ends back together . this process is n't as accurate . it can cause genes to get mixed up , or moved around . but it 's useful when sister dna is n't available . of course , changes to dna are n't always bad . beneficial mutations can allow a species to evolve . but most of the time , we want dna to stay the same . defects in dna repair are associated with premature aging and many kinds of cancer . so if you 're looking for a fountain of youth , it 's already operating in your cells , billions and billions of times a day .

different ones respond to different types of damage . one common error is base mismatches . each nucleotide contains a base , and during dna replication , the enzyme dna polymerase is supposed to bring in the right partner to pair with every base on each template strand .

base mismatches take place :

translator : andrea mcdonough reviewer : bedirhan cinar what does `` going viral '' on the internet really mean , and why does it happen so quickly ? why is a financial institution too big to fail ? how does a virus in africa end up in the united states in a matter of hours ? why are facebook and google such powerful companies at creating global connections ? well , in a word : networks . but what are networks ? everyone knows about their social network , but there are all different kinds of networks you probably have n't thought about . networks are collections of links which combine by specific rules and behaviors if they are alive . we say that networks are alive because they are in constant change . over time , the connections within a network migrate and concentrate in new places , forming evolving structures . how the evolution and concentration of constantly changing connections occurs is the subject of a whole discipline called network theory . we can think of networks as neighborhoods . neighborhoods are defined by maps . a google map demonstrates the relationship between locations in exactly the same fashion a network connects hubs and nodes , using streets as links to connect neighborhoods . the reason a network can expand and evolve so quickly is based upon a mathematical concept called power functions . a power function is a mathematical amplification mechanism , which over specific and very small ranges , accelerates changes logarithmically . that is , a very small change in one parameter produces a huge change in another over a very specific range of values . an example of how network structure emerges is the algorithm used by google . as the number of links around a search term , say `` friends '' , increases , connections begin to form among millions of different searches using the term `` friend '' . what google has cleverly accomplished is a real-time mathematical model for how to predict the emergence of growing connections among billions of search terms . the algorithm google derived collects the number of references to any search object . as references to a search object increase , the number of links also increases , creating a node . as the node increases in size , it eventually becomes a hub , which links to many nodes . networks will continue to emerge as new ways of connecting and creating neighborhoods are defined . perhaps you can begin to see why networks are so powerful . as google continues to collect the billions of daily searches , new clusters of links will rapidly emerge , forming additional and growing networks . despite the logarithmic expansion of your network , the laws of six degrees of separation still apply . therefore , if you explore a close friend or acquaintances in you facebook network , everyone on average will be separated by six individuals or less and a map of your social network will create neighborhoods linked by common connections among friends .

why are facebook and google such powerful companies at creating global connections ? well , in a word : networks . but what are networks ? everyone knows about their social network , but there are all different kinds of networks you probably have n't thought about .

have you experienced any benefits from networks first hand ? what sort of benefits ?

hi there , i ’ m john green , this is crash course : world history and today we ’ re going to talk about islam , which like christianity and judaism grew up on the east coast of the mediterranean but unlike christianity and judaism is not terribly well understood in the west . for instance , you probably know what this is and what this is , you probably don ’ t know what that is . google it . mr. green mr. green why do you think people know so little about islamic history ? did you just ask an interesting non-annoying question , me from the past ? i think we don ’ t know about early islamic history because we don ’ t learn about it , me from the past , because we don ’ t learn about it , because we ’ re taught that our history is the story of christianity in europe , when in fact our history is the story of people on the planet , so let ’ s try to learn something today . [ theme music ] so in less than 200 years islam went from not existing to being the religious and political organizing principal of one of the largest empires in the world . and that story begins in the 7th century ce when the angel gabriel appeared to muhammad , a 40-ish guy who made his living as a caravan trader and told him to begin reciting the word of god . initially , this freaked muhammad out , as , you know , it would—but then his wife and a couple of other people encouraged him and slowly he came to accept the mantle as prophet . a few things to know about the world islam entered : first , muhammad ’ s society was intensely tribal . he was a member of the quraysh tribe , living in mecca and tribal ties were extremely important . also , at the time , the arabian peninsula was like this crazy religious melting pot . like most tribal arabs worshipped gods very similar to the mesopotamian gods you ’ ll remember from episode 3 . and by the time of muhammad , cult statutes of many of those gods had been collected in his hometown of mecca in this temple-like structure called the kaaba . but arabia was also a home for monotheisms like christianity and judaism , even a bit of zoroastrianism . so the message that there was only god wouldn ’ t have been like as surprising to muhammad as it was , for instance , to abraham . also , and this will become very important , the northern part of arabia was sandwiched between the byzantine empire and the persian sassanian empire—and you ’ ll remember , those guys were always fighting . they were like snowboarders and skiers , or like the westboro baptist church and everyone else . at its core , islam is what we call a radical reforming religion—just like jesus and moses sought to restore abrahamic monotheism after what they perceived as straying , so too did muhammad . muslims believe that god sent muhammad as the final prophet to bring people back to the one true religion , which involves the worship of , and submission to , a single and all-powerful god . the quran also acknowledges abraham and moses and jesus among others as prophets , but it ’ s very different from the hebrew and christian bibles : for one thing it ’ s much less narrative , but also its the written record of the revelations muhammad received—which means its not written from the point of view of people , it is seen as the actual word of god . the quran is a really broad-ranging text , but it returns again and again to a couple themes . one is strict monotheism and the other is the importance of taking care of those less fortunate than you . the quran , says of the good person spends his substance—however much he himself may cherish it—upon his near of kin , and the orphans , and the needy , and the wayfarer , and the beggars , and for the freeing of human beings from bondage . these revelations also radically increased the rights of women and orphans , which was one of the reasons why mohammad ’ s tribal leaders weren ’ t that psyched about them . to talk more about islamic faith and practice , let ’ s go to the thought bubble . the five pillars of islam are the basic acts considered obligatory , at least by sunni muslims . first is the shahada or the profession of the faith : there is no god but god and muhammad is god ’ s prophet , which is sometimes translated as “ there is no god but allah and muhammad is allah ’ s prophet ” , which tries to make muslims sound other and ignores the fact that the arabic word for god—whether you are christian or jewish or muslim—is allah . second , salat , or ritual prayer five times a day—at dawn , noon , afternoon , sunset , and late evening—which are obligatory unless you haven ’ t hit puberty , are too sick , or are menstruating . keep it pg , thought bubble . third , sawm , the month-long fast during the month of ramadan , in which muslims do not eat or drink or smoke cigarettes during daylight hours . since ramadan is a lunar-calendar month , it moves around the seasons , and obviously it ’ s most fun during the winter , when days are shorter , and least fun during the summer , when days are both long and hot . fourth is zakat , or almsgiving , in which non-poor muslims are required to give a percentage of their income to the poor , and lastly hajj , the pilgrimage to mecca that muslims must try to fulfill at least once in their lives , provided they are healthy and have enough money . and there ’ s also more to understanding islam than just knowing the quran . like judaism with its talmud , and christianity with its lives of saints and writings of church fathers , islam has supplementary sacred texts , chief among which is the hadith , a collection of sayings and stories about the prophet . thanks thought bubble . oh , it ’ s time for the open letter ? magic . an open letter to the 72 virgins . oh , but first let ’ s check what ’ s in the secret compartment . huh , it ’ s andre the giant . did you know that andre the giant died a virgin- is a fact that i made up ? dear 72 virgins , hey there , it ’ s me , john green . did you know that not all hadiths were created equal ? some sayings of the prophet are really well sourced . like for instance , a good friend or a relative heard the prophet say something and then it ended up as a hadith . but some hadiths are terribly sourced like , not to be irreverent , but some of it is like middle school gossip ; like rachel told rebekah that her sister ’ s brother ’ s friend kissed justin bieber on the face . and the vast majority of muslims don ’ t treat terribly sourced hadiths as scripture . and the idea that you go to heaven and get 72 virgins is not in the quran ; it ’ s in a terribly sourced hadith so it is my great regret to inform you , 72 virgins , that in the eyes of almost all muslims you do not exist . best wishes , john green one more thing about islam : like christianity and judaism , it has a body of law . you might have heard of it - it ’ s called sharia . although we tend to think of sharia as this single set of laws that all muslims follow , that ’ s ridiculous ; there are numerous competing interpretations of sharia , just as there are within any legal tradition . so people who embraced this worldview were called muslims , because they submitted to the will of god , and they became part of the umma , or community of believers . this would be a good moment for an uma thurman joke , but sadly she is no longer famous . i ’ m sorry if you ’ re watching this , uma thurman . being part of the umma trumped all other ties , including tribal ties , which got muhammad into some trouble and brings us , at last , back to history . so as muhammad ’ s following in mecca grew , the umma aroused the suspicion of the most powerful tribe , the quraysh . and it didn ’ t matter that muhammad himself was born into the quraysh tribe because he wouldn ’ t shut up about how there was only one god , which was really bad news to the quraysh tribe because they managed the pilgrimage trade in mecca , and if all those gods were false , it would be a disaster economically . —although come to think of it , in the end the meccan pilgrimage business turned out just fine . so the quraysh forced muhammad and his followers out of mecca in 622 ce , and they headed to yithrab , also known as medina . this journey , also know as the hijra , is so important that it marks year 0 in the islamic calendar . in medina , muhammad severed the religion ’ s ties to judaism , turning the focus of prayer away from jerusalem to mecca . also in medina , the islamic community started to look a lot more like a small empire than like a church . like , jesus never had a country to run . but muhammad did almost from the beginning . and in addition to being an important prophet , he was a good general and in 630 , the islamic community took back mecca . they destroyed the idols in the kabaa , and soon islam was as powerful a political force in the region as it was a religious one . and it ’ s because the political and religious coexisted from the beginning , that there ’ s no separate tradition of civic and religious law like there is in christianity and judaism . very different from judaism and even from christianity—which you ’ ll remember debated very different from judaism and even from christianity—which you ’ ll remember debated for generations whether to be inclusive . —and more importantly than separating islam from other monotheisms , that really separated islam from the tribalism in arabia . so then when muhammad died in 632 ce , there wasn ’ t a religious vacuum left behind : muhammad was the final prophet , the revelation of the quran would continue to guide the umma throughout their lives . but the community did need a political leader , a caliph . and the first caliph was abu bakr , muhammad ’ s father-in-law , who was not without his opponents : many people wanted ali , muhammad ’ s son-in-law , to lead the community . and although he did become the fourth caliph , that initial disagreement — to radically oversimplify because we only have ten minutes — began the divide between the two of the major sects of islam : suuni and shi ’ a . and even today , sunnis muslims believe abu bakr was rightly elected the first caliph and shi ’ a muslims believe it should ’ ve been ali . to sunnis , the first four caliphs—abu bakr , umar , uthman , and ali— are known as the rightly guided caliphs , and many of the conservative movements in the islamic world today are all about trying to restore the islamic world to those glory days , which—like most glory days—were not unambiguously glorious . abu bakr stabilized the community after muhammad ’ s death , and began the process of recording the quran in writing , and started the military campaigns against the byzantine and sassanian empires that within 116 years would allow the islamic empire to go from this to this . his successor umar was both an uncommonly good general and a brilliant administrator but like so many other great men , he proved terrible at avoiding assassination . which led to the caliphate of uthman , who standardized the quran and continued both his predecessor ’ s tradition of conquest and his predecessor ’ s tradition of getting assassinated . then ali finally got his turn at caliph , but his ascension was very controversial , and it ultimately led to a civil war . which eventually led to the emergence of uthman ’ s tribe , the umayyads , as the dynasty ruling over an ever-expanding islamic empire for more than a hundred years . it ’ s common to hear that in these early years islam quote spread by the sword , and that ’ s partly true , unless you are — wait for it — the mongols . actually , as usual , the truth is more complicated : many people , including the mongols but also including lots of people in central and east asia , embraced islam without any military campaigns . and in fact , the quran says that religion must not be an act of compulsion , but this much is true : the early islamic empire was really good at winning wars . and situated as they were between two very wealthy empires—the byzantines and the sassanians—there was plenty to fight for . first to fall was the sassanians , the last non-muslim successor to the persian empire . they were relatively easy pickings because they ’ d been fighting the byzantines for like 300 years and were super tired . also they ’ d been recently struck by plague . plague , man , i ’ m telling you ; it ’ s like the red tortoise shell of history . but in those early days they did pry away some valuable territory like egypt and the holy land and eventually they got into spain . where various muslim dynasties would entrench themselves until being expelled in 1492 . but as a good as they were at making war , it ’ s still tempting to chalk up the arabs ’ success to , you know , the will of god . and certainly a lot of the people they conquered felt that way . wars in this part of the world didn ’ t just pit people against each other , they also pitted their gods against each other . so while the islamic empire didn ’ t require its subjects to convert to islam , their stunning successes certainly convinced a lot of people that this monotheism thing was legit . once again , john green proving super hip to the slang of today ’ s young ’ ns . also , you paid lower taxes if you converted , and just as taxes on cigarettes lead to people not wanting to smoke , taxes on worshiping your idols lead to people not wanting to worship them anymore . so in a period of time that was , historically speaking , both remarkably recent and remarkably short , a small group of people from an area of the world with no natural resources managed to create one of the great empires of the world and also one of its great religions . and that very fact may be why people of western european descent remain largely ignorant about this period . not only were the muslims great conquerors , they spawned an explosion of trade and learning that lasted hundreds of years . they saved many of the classical texts that form the basis of the “ western canon ” while europe was ignoring them and they paved the way for the renaissance . while it ’ s important to remember that much of the world between spain and the indus river wasn ’ t arabized , most of it was so thoroughly islamized that these days we can ’ t think of the world we now call the middle east without thinking of it as islamic . perhaps the greatest testimony to islam ’ s power to organize peoples lives and their communities is that , in egypt , 5 times a day millions of people turn away from the pyramids and toward mecca . egypt , birthplace to one of the longest continuous cultures the world has ever known , is now the largest arab country in the world . next week we ’ ll talk about the dark ages . spoiler alert : they were darkest in the evening . thanks for watching and we ’ ll see you next time . crash course is produced and directed by stan muller , our script supervisor is danica johnson . the show is written by my high school history teacher raoul meyer and myself and our graphics team is thought bubble . last week ’ s phrase of the week was “ they might be giants ” . if you want to guess this week ’ s phrase of the week or suggest future ones you can do so in comments where you can also ask questions about today ’ s video that our team of historians will endeavor to answer . thank you so much for watching and as they say in my hometown , don ’ t forget to be awesome .

but muhammad did almost from the beginning . and in addition to being an important prophet , he was a good general and in 630 , the islamic community took back mecca . they destroyed the idols in the kabaa , and soon islam was as powerful a political force in the region as it was a religious one .

what did the islamic community do in 630 ?

translator : andrea mcdonough reviewer : jessica ruby in all times and places in our history , human beings have wondered , `` where did we come from ? what 's our place in the world ? what happens to us after we die ? '' religions are systems of belief that have developed and evolved over time in response to these and other eternal mysteries , driven by the feeling that some questions can only be answered by faith and based on an intuition that there is something greater than ourselves , a higher power we must answer to , or some source we all spring from and to which we must return . hinduism means the religions of india . it 's not a single religion but rather a variety of related beliefs and spiritual practices . it dates back five millennia to the time of krishna , a man of such virtue that he became known as an avatar of vishnu , an incarnation of the god in human form . he taught that all life follows karma , the law of cause and effect , and our job is to do our duty , or dharma , according to our place in society without worrying how things turn out . when we die , we are reincarnated into a new body . if we followed our dharma and did our proper duty in our past life , we get good karma , which sends our soul upward in the social scale . our rebirth into the next life is thus determined by what we do in this one . the wheel of rebirths is called samsara . it 's possible for a very holy person to lead a life with enough good karma to escape the wheel . this escape is called moksha . hinduism teaches that everything is one . the whole universe is one transcendent reality called brahman , and there 's just one brahman but many gods within it , and their roles , aspects , and forms differ according to various traditions . brahma is the creator , vishnu is the preserver who sometimes takes on human form , and shiva is the transformer , or lord of the dance . durga is the fiercely protective divine mother . ganesha has an elephant head and is the wise patron of success . hinduism is the third largest religion in the world . and although most hindus live in india , they can be found on every continent , one billion strong . now , let 's travel west , across deserts and mountains to the fertile crescent about 4,000 years ago . judaism began with god calling abraham and sarah to leave mesopotamia and migrate to the land of canaan . in return for their faith in the one true god , a revolutionary concept in the polytheistic world of that time , they would have land and many descendants . from this promise came the land of israel and the chosen people , but staying in that land and keeping those people together was going to be very difficult . the israelites were enslaved in egypt , but god freed them with the help of the prophet moses , who received the ten commandments and later hundreds more . they conquered the promised land , but could only keep it for a few hundred years . israel sits at a crossroads through which many armies marched over the centuries . and in the year 70 , the romans destroyed the temple in their capital , jerusalem . so , the religion transformed itself from a temple religion with sacrifices and priests to a religion of the book . because of this , judaism is a faith of symbolism , reverence , and deep meanings tied to the literature of its history . the many sacred scriptures make up the hebrew bible , or tanakh , and hundreds of written discussions and interpretations are contained in an expansive compendium of deeper meanings , called the talmud . jews find rich , symbolic meaning in daily life . at the passover meal , every item on the menu symbolizes an aspect of the escape from slavery . the importance of growing up is emphasized when young people reach the age of bar and bat mitzvah , ceremonies during which they assume responsibility for their actions and celebrate the weaving of their own lives into the faith , history , and texts of the jewish people . there are 14 million jews in the world today , 6 million in israel , which became independent following the horrors of genocide in world war ii , and 5 million in the united states . but now let 's go back 2500 years and return to india where buddhism began with a young prince named siddhartha . on the night he was conceived , his mother , queen maya , is said to have been visited in her sleep by a white elephant who entered her side . ten months later , prince siddartha was born into a life of luxury . venturing forth from his sheltered existence as a young man , he witnessed the human suffering that had been hidden from him and immediately set out to investigate its sources . why must people endure suffering ? must we reincarnate through hundreds of lives ? at first he thought the problem was attachment to material things , so he gave up his possessions . he became a wandering beggar , which he discovered certainly made him no happier . then he overheard a music teacher telling a student , `` do n't tighten the string too much , it will break . but do n't let it go too slack , or it will not sound . '' in a flash , he realized that looking for answers at the extremes was a mistake . the middle way between luxury and poverty seemed wisest . and while meditating under a bodhi tree , the rest of the answer came to him . all of life abounds with suffering . it 's caused by selfish craving for one 's own fulfillment at the expense of others . following an eight-step plan can teach us to reduce that craving , and thus reduce the suffering . on that day , siddhartha became the buddha , the enlightened one . not the only one , but the first one . the buddhist plan is called the eightfold path , and though it is not easy to follow , it has pointed the way for millions to enlightenment , which is what buddhahood means , a state of compassion , insight , peace , and steadfastness . from the time he got up from under that tree to the moment of his death as an old man , the buddha taught people how to become enlightened : right speech , right goals , a mind focused on what is real , and a heart focused on loving others . many buddhists believe in god or gods , but actions are more important than beliefs . there are nearly a billion buddhists in the world today , mostly in east , southeast , and south asia . 2,000 years ago in judaism 's promised land , christianity was born . just as hindus called krishna `` god in human form , '' christians say the same thing about jesus , and christianity grew out of judaism just as buddhism grew out of hinduism . the angel gabriel was sent by the god of abraham to ask a young woman named mary to become the mother of his son . the son was jesus , raised as a carpenter by mary and her husband joseph , until he turned 30 , when he began his public career as the living word of god . less interested in religiousness than in justice and mercy , jesus healed the sick in order to draw crowds and then taught them about his heavenly father -- affectionate , forgiving , and attentive . then , he would invite everyone to a common table to illustrate his kingdom of god , outcasts , sinners , and saints all eating together . he had only three years before his unconventional wisdom got him into trouble . his enemies had him arrested , and he was executed by rome in the standard means by which rabble-rousers were put to death , crucifixion . but shortly after he was buried , women found his tomb empty and quickly spread word , convinced that he had been raised from the dead . the first christians described his resurrected appearances , inspiring confidence that his message was true . the message : love one another as i have loved you . christians celebrate the birth of jesus in december at christmas , and his suffering , death , and resurrection during holy week in the spring . in the ceremony of baptism , a washing away of sin and welcoming into the christian community , recall jesus 's own baptism when he left his life as a carpenter . in the rite of communion , christians eat the bread and drink the wine blessed as the body and blood of jesus , recalling jesus 's last supper . there are two billion christians worldwide , representing almost a third of the world 's people . islam began 1400 years ago with a man of great virtue , meditating in a mountain cave in the arabian desert . the man was muhammad . he was visited by a divine messenger , again the angel gabriel , in arabic , jibril , delivering to him the words of allah , the one god of abraham . in the next few years , more and more messages came , and he memorized and taught them . the verses he recited were full of wise sayings , beautiful rhymes , and mysterious metaphors . but muhammad was a merchant , not a poet . many agreed the verses were indeed the words of god , and these believers became the first muslims . the word muslim means one who surrenders , meaning a person who submits to the will of god . a muslim 's five most important duties are called the five pillars : shahada , muslims declare publicly , there is no other god but allah , and muhammad is his final prophet ; salat , they pray five times a day facing mecca ; zakat , every muslim is required to give 2 or 3 % of their net worth to the poor ; sawm , they fast during daylight hours for the lunar month of ramadan to strengthen their willpower and their reliance on god ; and hajj , once in a lifetime , every muslim who is able must make a pilgrimage to the holy city of mecca , rehearsing for the time when they will stand before god to be judged worthy or unworthy of eternal life with him . the words of god , revealed to the prophet over 23 years , are collected in the quran , which literally translates into `` the recitation . '' muslims believe it to be the only holy book free of human corruption . it 's also considered by many to be the finest work of literature in the arabic language . islam is the world 's second largest religion , practiced by over one and a half billion muslims around the globe . religion has been an aspect of culture for as long as it has existed , and there are countless variations of its practice . but common to all religions is an appeal for meaning beyond the empty vanities and lowly realities of existence , beyond sin , suffering , and death , beyond fear , and beyond ourselves .

and in the year 70 , the romans destroyed the temple in their capital , jerusalem . so , the religion transformed itself from a temple religion with sacrifices and priests to a religion of the book . because of this , judaism is a faith of symbolism , reverence , and deep meanings tied to the literature of its history .

which of the following pairs of founders is considered by `` their '' religion to be god in human form ?

which is correct : `` a dozen eggs is ? '' or `` a dozen eggs are ? '' i remember being in elementary school , and my teachers making a big deal about the unit . and i never really got that , until one day , i was in the grocery store , and i wanted to buy an apple , but i could n't buy one apple . i had to buy a whole bag of apples . so i did . i bought one bag of apples , i took it home , i took one apple out of the bag , and i cut it up . and then i ate one slice . one bag , one apple , one slice . which of these is the real `` one '' ? well , they all are of course , and that 's what my elementary teachers were trying to tell me . because this is the important idea behind whole number place value , decimal place value and fractions . our whole number system depends on being able to change what we count as `` one '' . our whole number system depends on being able to change units . there are two ways to change units . we can compose , and we can partition . when we compose units , we take a bunch of things , we put them together to make a bigger thing , like a dozen eggs . we take 12 eggs , put them together to make a group , and we call that group a dozen . a dozen eggs is a composed unit . other examples of composed units include a deck of cards , a pair of shoes , a jazz quartet and of course , barbie and ken make a couple . but think about a loaf of bread . that 's not a composed unit , because we do n't get a bunch of slices from a bunch of different bakeries and put them together to make a loaf . no , we start with a loaf of bread and we cut it into smaller pieces called slices , so each slice of bread is a partitioned unit . other examples of partitioned units include a square of a chocolate bar , a section of an orange and a slice of pizza . the important thing about units is that once we 've made a new unit , we can treat it just like we did the old unit . we can compose composed units , and we can partition partitioned units . think about toaster pastries . they come in packs of two , and then those packs get put together in sets of four to make a box . so when i buy one box of toaster pastries , am i buying one thing , four things , or eight things ? it depends on the unit . one box , four packs , eight pastries . and when i share a slice of pizza with a friend , we have to cut `` it '' into two smaller pieces . so a box of toaster pastries is composed of composed units , and when i split a slice of pizza , i 'm partitioning a partitioned unit . but what does that have to do with math ? in math , everything is certain . two plus two equals four , and one is just one . but that 's not really right . one is n't always one . here 's why : we start counting at one , and we count up to nine : 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , and then we get to 10 , and in order to write 10 , we write a one and a zero . that one means that we have one group , and the zero helps us remember that it means one group , not one thing . but 10 , just like one , just like a dozen eggs , just like an egg , 10 is a unit . and 10 tens make 100 . so when i think about 100 , it 's like the box of toaster pastries . is 100 one thing , 10 things or 100 things ? and that depends on what `` one '' is , it depends on what the unit is . so think about all the times in math when you write the number one . no matter what place that one is in , no matter how many things that one represents , one is .

we take 12 eggs , put them together to make a group , and we call that group a dozen . a dozen eggs is a composed unit . other examples of composed units include a deck of cards , a pair of shoes , a jazz quartet and of course , barbie and ken make a couple .

what is an example of a composed unit ?

the five fingers of evolution . a thorough understanding of biology requires a thorough understanding of the process of evolution . most people are familiar with the process of natural selection . however , this is just one of five processes that can result in evolution . before we discuss all five of these processes , we should define evolution . evolution is simply change in the gene pool over time . but what is a gene pool ? and for that matter , what is a gene ? before spending any more time on genetics , let us begin with a story . imagine that a boat capsizes , and 10 survivors swim to shore on a deserted island . they are never rescued , and they form a new population that exists for thousands of years . strangely enough , five of the survivors have red hair . red hair is created when a person inherits two copies of the red gene from their parents . if you only have one copy of the gene , you wo n't have red hair . to make this easier , we will assume that the five non-redheads are not carriers of the gene . the initial frequency of the red-hair gene is therefore 50 percent , or 10 of 20 total genes . these genes are the gene pool . the 20 different genes are like cards in a deck that keep getting reshuffled with each new generation . sex is simply a reshuffling of the genetic deck . the cards are reshuffled and passed to the next generation ; the deck remains the same , 50 percent red . the genes are reshuffled and passed to the next generation ; the gene pool remains the same , 50 percent red . even though the population may grow in size over time , the frequency should stay at about 50 percent . if this frequency ever varies , then evolution has occurred . evolution is simply change in the gene pool over time . think about it in terms of the cards . if the frequency of the cards in the deck ever changes , evolution has occurred . there are five processes that can cause the frequency to change . to remember these processes , we will use the fingers on your hands , starting from the little finger and moving to the thumb . the little finger should remind you that the population can shrink . if the population shrinks , then chance can take over . for example , if only four individuals survive an epidemic , then their genes will represent the new gene pool . the next finger is the ring finger . this finger should remind you of mating , because a ring represents a couple . if individuals choose a mate based on their appearance or location , the frequency may change . if redheaded individuals only mate with redheaded individuals , they could eventually form a new population . if no one ever mates with redheaded individuals , these genes could decrease . the next finger is the middle finger . the m in the middle finger should remind you of the m in the word `` mutation . '' if a new gene is added through mutation , it can affect the frequency . imagine a gene mutation creates a new color of hair . this would obviously change the frequency in the gene pool . the pointer finger should remind you of movement . if new individuals flow into an area , or immigrate , the frequency will change . if individuals flow out of an area , or emigrate , then the frequency will change . in science , we refer to this movement as gene flow . all four of the processes represented by our fingers can cause evolution . small population size , non-random mating , mutations and gene flow . however , none of them lead to adaptation . natural selection is the only process that creates organisms better adapted to their local environment . i use the thumb to remember this process . nature votes thumbs up for adaptations that will do well in their environment , and thumbs down to adaptations that will do poorly . the genes for individuals that are not adapted for their environment will gradually be replaced by those that are better adapted . red hair is an example of one of these adaptations . red hair is an advantage in the northern climates , because the fair skin allowed ancestors to absorb more light and synthesize more vitamin d. thumbs up ! however , this was a disadvantage in the more southern climates , where increased uv radiation led to cancer and decreased fertility . thumbs down ! even the thumb itself is an adaptation formed through the process of natural selection . the evolution that we have described is referred to as microevolution , because it refers to a small change . however , this form of evolution may eventually lead to macroevolution , or speciation . every organism on the planet shares ancestry with a single common ancestor . all living organisms on the planet are connected back in time through the process of evolution . take a look at your own hand . it 's an engineering masterpiece that was created by the five processes i just described , over millions and millions of years . can you recall the five main causes of evolution from memory ? if you ca n't , hit rewind and watch that part again . but if you can , give yourself or your neighbor a big five-fingered high five .

even the thumb itself is an adaptation formed through the process of natural selection . the evolution that we have described is referred to as microevolution , because it refers to a small change . however , this form of evolution may eventually lead to macroevolution , or speciation . every organism on the planet shares ancestry with a single common ancestor .

compare and contrast microevolution and macroevolution .

our story is about a girl named iris . iris is very sensitive . ( bird cawing ) so much that she is always in tears . she cries when she 's sad , when she 's happy , ( godzilla roars ) and even tears up when things just get to her . she has special lacrimal glands to make new tears and special tubes , called lacrimal puncta , to drain old ones away . and she cries so much that she goes through ten ounces of tears per day , thirty gallons a year ! in fact , if you look closely , you 'll see that she 's crying a little bit all the time . the basal tears that iris constantly produces form a thin coating of three layers that cover her and keep dirt and debris away . right next to iris is the mucus layer , which keeps the whole thing fastened to her . on top of it is the aqueous layer , which keeps iris hydrated , repels invasive bacteria , and protects her skin , or cornea , from damage . and , finally , there is the lipid layer , an oily outer film that keeps the surface smooth for iris to see through , and prevents the other layers from evaporating . normally , iris goes about her day without really noticing the basal tears doing their thing . that 's kind of their whole point . but one day , she meets a girl named onion . iris is immediately smitten . onion looks gorgeous in her bright purple jacket , and she smells terrific . so , iris invites onion to her house for dinner . but when she comes in and takes off her jacket , something terrible happens . you see , when onion 's jacket is removed , a chemical reaction happens , converting the sulfoxides that make her smell so great into sulfenic acid , which then becomes a nasty substance with a long name : syn-propanethial s-oxide . the gas stings iris , and suddenly , she ca n't help it , she starts weeping uncontrollably . these reflex tears are different from the basal tears that iris is used to . because they 're designed to wash away harmful substances , or particles , they 're released in much larger amounts , and their aqueous layer contains more antibodies to stop any microorganisms that may be trying to get in , as well . both iris and onion are devastated . they know they ca n't continue their relationship if iris is going to hurt and cry every time onion takes off her jacket . so , they decide to break up . as onion walks out the door , iris stops crying . and immediately starts again . only now , she 's not crying reflex tears but emotional tears . when someone is either too sad or too happy , it feels like a loss of control , which can be dangerous . so , emotional tears are sent in to stabilize the mood as quickly as possible , along with other physical reactions , such as an increased heart rate and slower breathing . but scientists still are n't sure exactly how or why the tears themselves are helpful . they may be a social mechanism to elicit sympathy or show submission . but some studies have also found that emotional tears contain higher levels of stress hormones , such as acth and enkephalin , an endorphin and natural pain killer . in this case , emotional tears are also directly calming iris down , as well as signaling her emotional state to others . sorry things did n't work out with onion , iris , but do n't worry . as long as you have all three kinds of tears working to keep you balanced and healthy , it will get better . you 'll see .

and immediately starts again . only now , she 's not crying reflex tears but emotional tears . when someone is either too sad or too happy , it feels like a loss of control , which can be dangerous .

why are emotional tears triggered by happiness as well as sadness ?

translator : andrea mcdonough reviewer : bedirhan cinar mysteries of vernacular miniature , something distinctively smaller than other members of its type or class . miniature traces its roots to the latin , < i > minium < /i > , which meant , `` red lead '' . minium referred , in particular , to a compound of lead used as a pigment in medieval times . in those days , because there were no printing presses , groups of scribes were tasked with painstakingly copying all books by hand . whenever they needed to denote a chapter break or a division of text , scribes would switch from standard black to the red pigment , minium . another important visual device used to increase the prominence of certain portions of text was to set them off with large , ornate , and colorful capital letters , often surrounded by tiny , detailed paintings . the italians began to refer to these elaborate and diminutive paintings as < i > miniatura < /i > , illuminations . because of the necessarily small size of the paintings , miniatura began to be associated with all things wee and spawned to other words with the same base , like the latin < i > minimum < /i > , for least . miniatura was transmuted into english in the 16th century as the word , < i > miniature < /i > , and since that time , it has had the exact same meaning we use today .

because of the necessarily small size of the paintings , miniatura began to be associated with all things wee and spawned to other words with the same base , like the latin < i > minimum < /i > , for least . miniatura was transmuted into english in the 16th century as the word , < i > miniature < /i > , and since that time , it has had the exact same meaning we use today .

the word miniature has changed meanings several times in the past two centuries .

translator : andrea mcdonough reviewer : bedirhan cinar take a look outside a window . what is the season where you are ? how do you know ? most likely , you looked at a tree or plant and noticed details about its leaves and assessed the qualities of sunlight streaming outside . observing the timing of biological events in relation to changes in season and climate is called `` phenology '' . when you notice the daffodil buds are poking through the snow and think spring is on its way , you 're using phenology . when you see leaves turn from green to red , and watch migrating birds fly past , and realize that summer is over , autumn is here , you 're using phenology . literally meaning , `` the science of appearance '' , phenology comes from the greek words `` pheno , '' to show or appear , and `` logos , '' to study . humans have relied on phenology since the time of hunters and gatherers . we 've watched changes in seasons to know when to plant and harvest food and when to track migrating animals . scientists observe and document seasonal changes in nature and look for patterns in the timing of seasonal events . timing of these natural signs has remained consistent until recently . increasing global temperature is causing rhythms of nature to shift . bud burst , the day when a tree or plant 's leaf or flower buds open , is occurring earlier in the year for some species . for every one degree celsius rise in temperature , bud burst happens five days earlier than usual . differences in timing affect not only plants , but the insects and birds that depend on the plants for food . for example , oak trees in the arnhem forest of the netherlands now experience bud burst ten days earlier , as compared to twenty years ago . new oak leaves are a favorite food of winter moth caterpillars . to survive , the caterpillars adapted to the change in the tree 's timing , and now hatch 15 days earlier than before . migrating pied flycatcher birds , however , are n't doing as well . the birds prefer to feed their chicks winter moth caterpillars . the caterpillars are now hatching earlier , but the birds ' chicks are not . this delay is costing the birds a food source . the pied flycatcher population has decreased by up to 90 % in some areas as a result . changes to a seemingly simple event , leaves opening , has ripple effects throughout a food web . earlier bloom times can also have an economic impact . the famed cherry blossoms in washington d.c. are blooming five days earlier than before . since the cherry trees are blooming earlier , the blossoms also fade earlier , frustrating thousands of tourists who visit for the cherry blossom festival . high school marching bands plan all year to attend the parade and perform , surrounded by a majestic white canopy . how disappointing for them to find , well , trees rather than the famous cherry blossoms ! plants and animals react to changes in natural light and temperature . increasing temperatures cause plants to bloom earlier than before , and become out of sync with the insects and birds in a food web . so , the next time you look out your window and notice what season it is , you may be fooled by those blooming trees . think of phenology , then think of how you can play a part to slow climate change .

so , the next time you look out your window and notice what season it is , you may be fooled by those blooming trees . think of phenology , then think of how you can play a part to slow climate change .

how deeply do you think your carbon footprint affects phenology ?

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 .

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 .

we often confuse irony with something _____________ .

imagine a group of people . how big do you think the group would have to be before there 's more than a 50 % chance that two people in the group have the same birthday ? assume for the sake of argument that there are no twins , that every birthday is equally likely , and ignore leap years . take a moment to think about it . the answer may seem surprisingly low . in a group of 23 people , there 's a 50.73 % chance that two people will share the same birthday . but with 365 days in a year , how 's it possible that you need such a small group to get even odds of a shared birthday ? why is our intuition so wrong ? to figure out the answer , let 's look at one way a mathematician might calculate the odds of a birthday match . we can use a field of mathematics known as combinatorics , which deals with the likelihoods of different combinations . the first step is to flip the problem . trying to calculate the odds of a match directly is challenging because there are many ways you could get a birthday match in a group . instead , it 's easier to calculate the odds that everyone 's birthday is different . how does that help ? either there 's a birthday match in the group , or there is n't , so the odds of a match and the odds of no match must add up to 100 % . that means we can find the probability of a match by subtracting the probability of no match from 100 . to calculate the odds of no match , start small . calculate the odds that just one pair of people have different birthdays . one day of the year will be person a 's birthday , which leaves only 364 possible birthdays for person b . the probability of different birthdays for a and b , or any pair of people , is 364 out of 365 , about 0.997 , or 99.7 % , pretty high . bring in person c. the probability that she has a unique birthday in this small group is 363 out of 365 because there are two birthdates already accounted for by a and b . d 's odds will be 362 out of 365 , and so on , all the way down to w 's odds of 343 out of 365 . multiply all of those terms together , and you 'll get the probability that no one shares a birthday . this works out to 0.4927 , so there 's a 49.27 % chance that no one in the group of 23 people shares a birthday . when we subtract that from 100 , we get a 50.73 % chance of at least one birthday match , better than even odds . the key to such a high probability of a match in a relatively small group is the surprisingly large number of possible pairs . as a group grows , the number of possible combinations gets bigger much faster . a group of five people has ten possible pairs . each of the five people can be paired with any of the other four . half of those combinations are redundant because pairing person a with person b is the same as pairing b with a , so we divide by two . by the same reasoning , a group of ten people has 45 pairs , and a group of 23 has 253 . the number of pairs grows quadratically , meaning it 's proportional to the square of the number of people in the group . unfortunately , our brains are notoriously bad at intuitively grasping non-linear functions . so it seems improbable at first that 23 people could produce 253 possible pairs . once our brains accept that , the birthday problem makes more sense . every one of those 253 pairs is a chance for a birthday match . for the same reason , in a group of 70 people , there are 2,415 possible pairs , and the probability that two people have the same birthday is more than 99.9 % . the birthday problem is just one example where math can show that things that seem impossible , like the same person winning the lottery twice , actually are n't unlikely at all . sometimes coincidences are n't as coincidental as they seem .

so it seems improbable at first that 23 people could produce 253 possible pairs . once our brains accept that , the birthday problem makes more sense . every one of those 253 pairs is a chance for a birthday match .

which of the following best describes the approach taken to solve the birthday problem in this video ?

i was a blue-eyed , chubby-cheeked five-year-old when i joined my family on the picket line for the first time . my mom made me leave my dolls in the minivan . i 'd stand on a street corner in the heavy kansas humidity , surrounded by a few dozen relatives , with my tiny fists clutching a sign that i could n't read yet : `` gays are worthy of death . '' this was the beginning . our protests soon became a daily occurrence and an international phenomenon , and as a member of westboro baptist church , i became a fixture on picket lines across the country . the end of my antigay picketing career and life as i knew it , came 20 years later , triggered in part by strangers on twitter who showed me the power of engaging the other . in my home , life was framed as an epic spiritual battle between good and evil . the good was my church and its members , and the evil was everyone else . my church 's antics were such that we were constantly at odds with the world , and that reinforced our otherness on a daily basis . `` make a difference between the unclean and the clean , '' the verse says , and so we did . from baseball games to military funerals , we trekked across the country with neon protest signs in hand to tell others exactly how `` unclean '' they were and exactly why they were headed for damnation . this was the focus of our whole lives . this was the only way for me to do good in a world that sits in satan 's lap . and like the rest of my 10 siblings , i believed what i was taught with all my heart , and i pursued westboro 's agenda with a special sort of zeal . in 2009 , that zeal brought me to twitter . initially , the people i encountered on the platform were just as hostile as i expected . they were the digital version of the screaming hordes i 'd been seeing at protests since i was a kid . but in the midst of that digital brawl , a strange pattern developed . someone would arrive at my profile with the usual rage and scorn , i would respond with a custom mix of bible verses , pop culture references and smiley faces . they would be understandably confused and caught off guard , but then a conversation would ensue . and it was civil -- full of genuine curiosity on both sides . how had the other come to such outrageous conclusions about the world ? sometimes the conversation even bled into real life . people i 'd sparred with on twitter would come out to the picket line to see me when i protested in their city . a man named david was one such person . he ran a blog called `` jewlicious , '' and after several months of heated but friendly arguments online , he came out to see me at a picket in new orleans . he brought me a middle eastern dessert from jerusalem , where he lives , and i brought him kosher chocolate and held a `` god hates jews '' sign . ( laughter ) there was no confusion about our positions , but the line between friend and foe was becoming blurred . we 'd started to see each other as human beings , and it changed the way we spoke to one another . it took time , but eventually these conversations planted seeds of doubt in me . my friends on twitter took the time to understand westboro 's doctrines , and in doing so , they were able to find inconsistencies i 'd missed my entire life . why did we advocate the death penalty for gays when jesus said , `` let he who is without sin cast the first stone ? '' how could we claim to love our neighbor while at the same time praying for god to destroy them ? the truth is that the care shown to me by these strangers on the internet was itself a contradiction . it was growing evidence that people on the other side were not the demons i 'd been led to believe . these realizations were life-altering . once i saw that we were not the ultimate arbiters of divine truth but flawed human beings , i could n't pretend otherwise . i could n't justify our actions -- especially our cruel practice of protesting funerals and celebrating human tragedy . these shifts in my perspective contributed to a larger erosion of trust in my church , and eventually it made it impossible for me to stay . in spite of overwhelming grief and terror , i left westboro in 2012 . in those days just after i left , the instinct to hide was almost paralyzing . i wanted to hide from the judgement of my family , who i knew would never speak to me again -- people whose thoughts and opinions had meant everything to me . and i wanted to hide from the world i 'd rejected for so long -- people who had no reason at all to give me a second chance after a lifetime of antagonism . and yet , unbelievably , they did . the world had access to my past because it was all over the internet -- thousands of tweets and hundreds of interviews , everything from local tv news to `` the howard stern show '' -- but so many embraced me with open arms anyway . i wrote an apology for the harm i 'd caused , but i also knew that an apology could never undo any of it . all i could do was try to build a new life and find a way somehow to repair some of the damage . people had every reason to doubt my sincerity , but most of them did n't . and -- given my history , it was more than i could 've hoped for -- forgiveness and the benefit of the doubt . it still amazes me . i spent my first year away from home adrift with my younger sister , who had chosen to leave with me . we walked into an abyss , but we were shocked to find the light and a way forward in the same communities we 'd targeted for so long . david , my `` jewlicious '' friend from twitter , invited us to spend time among a jewish community in los angeles . we slept on couches in the home of a hasidic rabbi and his wife and their four kids -- the same rabbi that i 'd protested three years earlier with a sign that said , `` your rabbi is a whore . '' we spent long hours talking about theology and judaism and life while we washed dishes in their kosher kitchen and chopped vegetables for dinner . they treated us like family . they held nothing against us , and again i was astonished . that period was full of turmoil , but one part i 've returned to often is a surprising realization i had during that time -- that it was a relief and a privilege to let go of the harsh judgments that instinctively ran through my mind about nearly every person i saw . i realized that now i needed to learn . i needed to listen . this has been at the front of my mind lately , because i ca n't help but see in our public discourse so many of the same destructive impulses that ruled my former church . we celebrate tolerance and diversity more than at any other time in memory , and still we grow more and more divided . we want good things -- justice , equality , freedom , dignity , prosperity -- but the path we 've chosen looks so much like the one i walked away from four years ago . we 've broken the world into us and them , only emerging from our bunkers long enough to lob rhetorical grenades at the other camp . we write off half the country as out-of-touch liberal elites or racist misogynist bullies . no nuance , no complexity , no humanity . even when someone does call for empathy and understanding for the other side , the conversation nearly always devolves into a debate about who deserves more empathy . and just as i learned to do , we routinely refuse to acknowledge the flaws in our positions or the merits in our opponent 's . compromise is anathema . we even target people on our own side when they dare to question the party line . this path has brought us cruel , sniping , deepening polarization , and even outbreaks of violence . i remember this path . it will not take us where we want to go . what gives me hope is that we can do something about this . the good news is that it 's simple , and the bad news is that it 's hard . we have to talk and listen to people we disagree with . it 's hard because we often ca n't fathom how the other side came to their positions . it 's hard because righteous indignation , that sense of certainty that ours is the right side , is so seductive . it 's hard because it means extending empathy and compassion to people who show us hostility and contempt . the impulse to respond in kind is so tempting , but that is n't who we want to be . we can resist . and i will always be inspired to do so by those people i encountered on twitter , apparent enemies who became my beloved friends . and in the case of one particularly understanding and generous guy , my husband . there was nothing special about the way i responded to him . what was special was their approach . i thought about it a lot over the past few years and i found four things they did differently that made real conversation possible . these four steps were small but powerful , and i do everything i can to employ them in difficult conversations today . the first is do n't assume bad intent . my friends on twitter realized that even when my words were aggressive and offensive , i sincerely believed i was doing the right thing . assuming ill motives almost instantly cuts us off from truly understanding why someone does and believes as they do . we forget that they 're a human being with a lifetime of experience that shaped their mind , and we get stuck on that first wave of anger , and the conversation has a very hard time ever moving beyond it . but when we assume good or neutral intent , we give our minds a much stronger framework for dialogue . the second is ask questions . when we engage people across ideological divides , asking questions helps us map the disconnect between our differing points of view . that 's important because we ca n't present effective arguments if we do n't understand where the other side is actually coming from and because it gives them an opportunity to point out flaws in our positions . but asking questions serves another purpose ; it signals to someone that they 're being heard . when my friends on twitter stopped accusing and started asking questions , i almost automatically mirrored them . their questions gave me room to speak , but they also gave me permission to ask them questions and to truly hear their responses . it fundamentally changed the dynamic of our conversation . the third is stay calm . this takes practice and patience , but it 's powerful . at westboro , i learned not to care how my manner of speaking affected others . i thought my rightness justified my rudeness -- harsh tones , raised voices , insults , interruptions -- but that strategy is ultimately counterproductive . dialing up the volume and the snark is natural in stressful situations , but it tends to bring the conversation to an unsatisfactory , explosive end . when my husband was still just an anonymous twitter acquaintance , our discussions frequently became hard and pointed , but we always refused to escalate . instead , he would change the subject . he would tell a joke or recommend a book or gently excuse himself from the conversation . we knew the discussion was n't over , just paused for a time to bring us back to an even keel . people often lament that digital communication makes us less civil , but this is one advantage that online conversations have over in-person ones . we have a buffer of time and space between us and the people whose ideas we find so frustrating . we can use that buffer . instead of lashing out , we can pause , breathe , change the subject or walk away , and then come back to it when we 're ready . and finally ... make the argument . this might seem obvious , but one side effect of having strong beliefs is that we sometimes assume that the value of our position is or should be obvious and self-evident , that we should n't have to defend our positions because they 're so clearly right and good that if someone does n't get it , it 's their problem -- that it 's not my job to educate them . but if it were that simple , we would all see things the same way . as kind as my friends on twitter were , if they had n't actually made their arguments , it would 've been so much harder for me to see the world in a different way . we are all a product of our upbringing , and our beliefs reflect our experiences . we ca n't expect others to spontaneously change their own minds . if we want change , we have to make the case for it . my friends on twitter did n't abandon their beliefs or their principles -- only their scorn . they channeled their infinitely justifiable offense and came to me with pointed questions tempered with kindness and humor . they approached me as a human being , and that was more transformative than two full decades of outrage , disdain and violence . i know that some might not have the time or the energy or the patience for extensive engagement , but as difficult as it can be , reaching out to someone we disagree with is an option that is available to all of us . and i sincerely believe that we can do hard things , not just for them but for us and our future . escalating disgust and intractable conflict are not what we want for ourselves , or our country or our next generation . my mom said something to me a few weeks before i left westboro , when i was desperately hoping there was a way i could stay with my family . people i have loved with every pulse of my heart since even before i was that chubby-cheeked five-year-old , standing on a picket line holding a sign i could n't read . she said , `` you 're just a human being , my dear , sweet child . '' she was asking me to be humble -- not to question but to trust god and my elders . but to me , she was missing the bigger picture -- that we 're all just human beings . that we should be guided by that most basic fact , and approach one another with generosity and compassion . each one of us contributes to the communities and the cultures and the societies that we make up . the end of this spiral of rage and blame begins with one person who refuses to indulge these destructive , seductive impulses . we just have to decide that it 's going to start with us . thank you . ( applause )

this was the beginning . our protests soon became a daily occurrence and an international phenomenon , and as a member of westboro baptist church , i became a fixture on picket lines across the country . the end of my antigay picketing career and life as i knew it , came 20 years later , triggered in part by strangers on twitter who showed me the power of engaging the other .

briefly describe the agenda of the westboro baptist church .

technetium is the first element in the periodic table which is naturally radioactive , so it is the lightest radioactive element and so for a long time very little was known about it . now people are beginning to study it in suitably strong surroundings of ů to contain the radioactivity and they have discovered that the chemistry of technetium is in many ways quite similar to that of rhenium or manganese . and there are a number of medical treatments now which use the radioactivity of technetium in order to trace through the body and look at their emissions to find out about different diseases . and so the chemistry of technetium is becoming more important in the medical role , how to make a compound that you can get into the body safely and quickly so that it can be used for medical purposes .

technetium is the first element in the periodic table which is naturally radioactive , so it is the lightest radioactive element and so for a long time very little was known about it . now people are beginning to study it in suitably strong surroundings of ů to contain the radioactivity and they have discovered that the chemistry of technetium is in many ways quite similar to that of rhenium or manganese .

mendeleev predicted the existence of an element with an atomic mass of 100. what was the name he gave to the undiscovered element that became technetium ?

thousands of years in the making , what began as part of a religious festival honoring the greek god zeus in the rural greek town of olympia has today become the greatest show of sporting excellence on earth . the inception date in 776 bc became the basis for the greek 's earliest calendar , where time was marked in four-year increments called olympiads . what could it be ? why , it 's the olympic games , of course . competition fosters excellence , or so thought the ancient greeks . in addition to sporting events , contests were held for music , singing , and poetry . you can read about them all yourself in classical literary works , like homer 's `` iliad '' and virgil 's `` aeneid . '' even mythical heroes appreciate a good contest every now and then , would n't you say ? for the first thirteen games , the ancient greek olympics featured just one event , the two hundred yard dash . but over time , new exciting contests , like boxing , chariot and mule racing , and even a footrace where the competitors wore a full suit of armor enticed many hopeful champions into the olympic stadium . the combined running , jumping , wrestling , javelin throwing , and hurling the discus events known as the pentathlon inspired world-class competition , and the pankration , a no holds barred fight where only biting and eye-gouging were prohibited , ensured the toughest men were victorious . and victorious they were . nobody tops the local baker coroebus , who 776 bc became the very first olympic champion . and we 'll never forget orsippus of megara , the 720 bc olympic victor tore away his loincloth so he could race unimpeded , inaugurating the ancient greek tradition of competing in the nude . now there 's a winning streak , if ever we 've seen one . but all good things must end . in 391 ad , the christian roman emperor theodosius banned pagan practices , so the world soon bid a fond farewell to the olympic games . but just like those early pankration athletes , you ca n't keep a good one down , and 1500 years later in 1896 , the modern olympic games kicked off in athens , greece . today , the summer and winter olympics bring international world-class athletes together by the thousands , uniting fans by the billions for the world 's foremost sporting competition . citius , altius , fortius . three cheers for the olympics .

citius , altius , fortius . three cheers for the olympics .

what was the date of the first olympics ?

water is virtually eveywhere , from soil moisture and ice caps , to the cells inside our own bodies . depending on factors like location , fat index , age , and sex , the average human is between 55-60 % water . at birth , human babies are even wetter . being 75 % water , they are swimmingly similar to fish . but their water composition drops to 65 % by their first birthday . so what role does water play in our bodies , and how much do we actually need to drink to stay healthy ? the h20 in our bodies works to cushion and lubricate joints , regulate temperature , and to nourish the brain and spinal cord . water is n't only in our blood . an adult 's brain and heart are almost three quarters water . that 's roughly equivalent to the amount of moisture in a banana . lungs are more similar to an apple at 83 % . and even seemingly dry human bones are 31 % water . if we are essentially made of water , and surrounded by water , why do we still need to drink so much ? well , each day we lose two to three liters through our sweat , urine , and bowel movements , and even just from breathing . while these functions are essential to our survival , we need to compensate for the fluid loss . maintaining a balanced water level is essential to avoid dehydration or over-hydration , both of which can have devastating effects on overall health . at first detection of low water levels , sensory receptors in the brain 's hypothalamus signal the release of antidiuretic hormone . when it reached the kidneys , it creates aquaporins , special channels that enable blood to absorb and retain more water , leading to concentrated , dark urine . increased dehydration can cause notable drops in energy , mood , skin moisture , and blood pressure , as well as signs of cognitive impairment . a dehydrated brain works harder to accomplish the same amount as a normal brain , and it even temporarily shrinks because of its lack of water . over-hydration , or hyponatremia , is usually caused by overconsumption of water in a short amount of time . athletes are often the victims of over-hydration because of complications in regulating water levels in extreme physical conditions . whereas the dehydrated brain amps up the production of antidiuretic hormone , the over-hydrated brain slows , or even stops , releasing it into the blood . sodium electrolytes in the body become diluted , causing cells to swell . in severe cases , the kidneys ca n't keep up with the resulting volumes of dilute urine . water intoxication then occurs , possibly causing headache , vomiting , and , in rare instances , seizures or death . but that 's a pretty extreme situation . on a normal , day-to-day basis , maintaining a well-hydrated system is easy to manage for those of us fortunate enough to have access to clean drinking water . for a long time , conventional wisdom said that we should drink eight glasses a day . that estimate has since been fine-tuned . now , the consensus is that the amount of water we need to imbibe depends largely on our weight and environment . the recommended daily intake varies from between 2.5-3.7 liters of water for men , and about 2-2.7 liters for women , a range that is pushed up or down if we are healthy , active , old , or overheating . while water is the healthiest hydrator , other beverages , even those with caffeine like coffee or tea , replenish fluids as well . and water within food makes up about a fifth of our daily h20 intake . fruits and vegetables like strawberries , cucumbers , and even broccoli are over 90 % water , and can supplement liquid intake while providing valuable nutrients and fiber . drinking well might also have various long-term benefits . studies have shown that optimal hydration can lower the chance of stroke , help manage diabetes , and potentially reduce the risk of certain types of cancer . no matter what , getting the right amount of liquid makes a world of difference in how you 'll feel , think , and function day to day .

now , the consensus is that the amount of water we need to imbibe depends largely on our weight and environment . the recommended daily intake varies from between 2.5-3.7 liters of water for men , and about 2-2.7 liters for women , a range that is pushed up or down if we are healthy , active , old , or overheating . while water is the healthiest hydrator , other beverages , even those with caffeine like coffee or tea , replenish fluids as well .

we lose 2 to 3 liters of water each day by doing which of the following ?

mendelevium , which is named after one of the most important people as far as the periodic table is concerned , which is dimitri mendeleev . mendelevium is named after mendeleev , in russia the periodic table is called the mendeleev table , and you can see here on my tie i ’ ve got a picture of mendeleev . it ’ s another element which has absolutely zero use in the real world . he is one of the iconic , iconic , pictures of chemists that most chemists will recognise mendeleev . ah , mendeleev was all to do with how it was discovered to put the periodic table together , for a long time , people knew that there were different elements and that they knew that they had different properties . what they couldn ’ t do , was rationalise those properties and understand why certain elements behaved in a similar manner even though in principle they should have been very different . but mendeleev has another cause of fame ; he is famous in russia because he was the person who worked out the standard for the strength of vodka . so here i have a bottle of russian mendeleev , you ’ ll see it says mendeleev here and vodka , with a periodic table on it , and here ’ s the formula , ethanol plus water , and mendeleev was the person that worked out the standard of 40 % of ethanol in water as being vodka . and in fact it ’ s remarkable the number of experiments you read where people have used 40 % ethanol in water as the solvent for their reaction doubtless because they had a handy bottle of vodka or some similar drink .

mendelevium , which is named after one of the most important people as far as the periodic table is concerned , which is dimitri mendeleev . mendelevium is named after mendeleev , in russia the periodic table is called the mendeleev table , and you can see here on my tie i ’ ve got a picture of mendeleev . it ’ s another element which has absolutely zero use in the real world .

what is the periodic table called in russia ?

the sight of mistletoe may either send you scurrying , or if you have your eye on someone , awaiting an opportunity beneath its snow white berries , but how did the festive christmas tradition of kissing under mistletoe come about ? the long-lived custom intertwines the mythology and biology of this intriguing plant . there are more than 1,000 species of mistletoe , which grows the world over . in fact , the ancient europeans were so captivated by the plant 's unusual growth habits that they included it in their legends and myths . in ancient rome , pliny the elder described how the druid priesthood in ancient england believed that mistletoe was a plant dropped down from heaven by the gods . that explained its unlikely position amongst the high branches of certain trees . they also believed it had powers of healing and bestowing fertility . meanwhile , scandinavian legend told of the plant 's mystical qualities in the story of the god baldr and his adoring mother frigg , goddess of love , marriage , and fertility . frigg loved her son so much that she commanded every plant , animal , and inanimate object to vow they 'd never harm him . in her fervor , however , she overlooked the mistletoe . the mischievous god loki realized this oversight and pierced baldr 's heart with an arrow carved from a mistletoe branch . frigg cried tears of such sadness that they formed the mistletoe 's pearly berries , making the other gods pity her and agree to resurrect baldr . hearing the news , frigg became so overjoyed that she transformed the mistletoe from a symbol of death into one of peace and love . she mandated a one-day truce for all fights , and that everyone embrace beneath its branches when they passed to spread more love into the world . in the 17th century , british colonists arriving in the new world found a different , but very similar looking , species of mistletoe . they applied it to these tales of magic , fertility , and love , spreading the mistletoe-hanging tradition from europe into america . by the 18th century , people in britain had turned this into a christmas tradition , but this custom comes down to more than just human imagination . all of it was inspired by the plant 's intriguing biology . we see mistletoe as a festive decoration , but draped on tree boughs in the wild , it 's known as a partly parasitic plant . mistletoe relies on modified roots called haustoria that penetrate the tree bark and siphon off the water and minerals trees carry up their trunks to colonize nearby trees with its seeds , mistletoe depends on birds and other creatures to do the dispersing . birds that eat the mistletoe 's sticky white berries sometimes get rid of the gluey seeds by wiping them off onto tree bark . or with a bit of luck , they excrete the indigestible seed onto a tree where it germinates and starts to grow . with its resilience and foliage that stays lush even while the surrounding trees lose their leaves , you can see why mistletoe captivated our superstitious ancestors . they saw these as signs of the plant 's magical qualities and fertility . even today , the mistletoe inspires wonder with the diversity of wildlife it supports . more than just a parasite , it 's also known as a keystone species . it 's eaten by a diversity of animals , including deer , elk , squirrels , chipmunks , porcupines , robins , bluebirds , morning doves , and the butterfly genus delias . some mistletoe species produce dense bushes , which are excellent nesting locations for a variety of birds . and despite their parasitic relationship with trees , mistletoes can also help other plants . for instance , juniper sprouts near mistletoe to benefit from the visiting berry-eating birds . through the many benefits it provides , mistletoe influences diversity , and allows ecosystems to flourish . you might even say that for this iconic plant , life imitates legend . in the wild , mistletoe has the power to bring things together , and in our own traditions , we see that happening , too .

she mandated a one-day truce for all fights , and that everyone embrace beneath its branches when they passed to spread more love into the world . in the 17th century , british colonists arriving in the new world found a different , but very similar looking , species of mistletoe . they applied it to these tales of magic , fertility , and love , spreading the mistletoe-hanging tradition from europe into america .

in the new world , the british colonists found :

the evolutionary tango of animal genitalia . can you guess what you 're looking at ? if you answered `` duck vagina , '' you 'd be right . although the bird 's outward appearance may not strike you as especially odd , it uses this strange , intricate , cork-screw shaped contraption to reproduce . we see similarly unbelievable genitalia in insects , mammals , reptiles , fish , spiders , and even snails . apparently , no organs evolve faster and into more variable shapes than those involved in procreation . superficially , it makes sense because evolution works via reproduction . when an animal leaves more offspring , its genes will spread . and since genitalia are an animal 's tools for reproduction , any improvement there will have immediate effect . and yet , what 's the point of having such decorative nether regions ? after all , the function of genitalia seems simple . a penis deposits a bit of sperm and a vagina receives it and delivers it to the egg . a pipette-like thingy on the male and a funnel-like gizmo on the female should do just fine for any animal . and yet , that 's not what we see . the penis of a chicken flea , for example , looks nothing like a pipette , more like an exploded grandfather clock . and the vagina of a featherwing beetle resembles something you 'd find in a dr. seuss book . throughout the animal kingdom , genitalia are very complex things , much more complicated than seems necessary for what they 're meant to do . that 's because genitalia do more than just deposit and receive sperm . many male animals also use the penis as courtship device , like crane flies . in some south american species , males have a tiny washboard and scraper on their penis , which produces a song that reverberates throughout the female 's body when they mate . it 's thought that if female crane flies enjoy this unusual serenade , they 'll allow the male to father their offspring . this way , the genes of the most musical penises spread , leading to rapid evolution of insects ' phalluses . similarly , some beetles have two little drumsticks on either side of the penis . during mating , they 'll rub , slap , or tap the female with these . and some hoofed mammals , like rams and bulls , use a whip-like extension on the penis 's left side to create a sensation during mating . but how can females really choose between males if she can only assess them after mating ? this is where the power of female adaptation comes into play . in fact , insemination is different to conception , and the female genitalia exploit this distinction . for instance , in some dung flies , the vagina contains pockets for separating sperm from different males depending on how appealing they were . males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes . but there are others because genitalia are also where a sexual conflict is played out . a female 's interests are best served if she fertilizes her eggs with the sperm of the best fathers and creates genetic variability amongst her offspring . for a male , on the other hand , this is bad news . for him , it would be best if a female used his sperm to fertilize all of her eggs . so we see cycles of adaptation in an evolutionary arms race to retain control . black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals , and bed bug males bypass a female 's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly . not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them . that allows them to maintain the power to filter out unwanted sperm with their genitalia . and duck vaginas are shaped like a clockwise spiral so that when the male inflates his long , counterclockwise coiled penis into her , and she disapproves , all she needs to do is flex her vaginal muscles and the penis just flubs out . so , genitalia differs so much , not just to fascinate us , but because in every species , they 're the result of a furious evolutionary tango of sex that has been going on for millions of years and will continue for millions of years to come .

black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals , and bed bug males bypass a female 's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly . not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them .

how do male bedbugs fertilize females ?

why do humans drink so much milk ? and given that all mammals lactate , why do we favor certain types of milk over others ? milk is the first thing we drink , and thanks to developments in the production and variety of dairy products , it can take on countless forms for our dietary and sensory well-being . milk 's primary function is as a complete source of nutrition for newborns . in fact , since it has all of the vital nutrients for development and growth , proteins , carbohydrates , fats , vitamins and minerals , and water , milk is the only thing a baby even needs to ingest for the first six months of life . the unique makeup of milk can vary depending on factors like species , diet , and location . reindeer of the arctic circle , for example , make energy-dense milk that 's about 20 % fat , roughly five times more than human or cow 's milk , to help their young survive the harsh , freezing climate . so how is milk made ? in the uniquely mammalian process of lactation , a special class of milk-secreting cells known as mammocytes line up in a single layer around pear-shaped alveoli . those cells absorb all of the building blocks of milk , then synthesize tiny droplets of fat on structures called smooth endoplasmic reticula . the droplets combine with each other and other molecules and are then expelled and stored in spaces between cells . mammary glands eventually secrete the milk through the breasts , udders , or , in the rare case of the platypus , through ducts in the abdomen . although this process is typically reserved for females , in some species , like dayak fruit bats , goats , and even cats , males can also lactate . milk drinkers worldwide consume dairy from buffalo , goats , sheeps , camels , yaks , horses , and cows . almost all of these species are ruminants , a type of mammal with four-chambered stomachs that yield large quantities of milk . of these , cows were the most easily domesticated and produce a milk that is both easily separated into cream and liquid and has a similar fat content to human milk . in their natural environment , mammals secrete milk on call for immediate consumption by their young . but with the demands of thirsty consumers , the dairy industry has enlisted methods to step up production , enhance shelf life , and provide a variety of milk products . in the dairy , centrifugation machines spin milk at high speeds , forcing less dense fats to separate from the liquid and float up . after being skimmed off , this fat , known as butterfat , can be used in dairy products like butter , cream , and cheese . or it can be later added back to the liquid in varying proportions to yield different fat content milks . full fat milk , sometimes referred to as whole milk , has 3.25 % butterfat added compared to 1-2 % for low and reduced fat milk , and less than half a percent for skim milk . to stop reseparation of the fat from the water , or creaming , the mixture undergoes the high-energy pressurized process of homogenization . before milk hits the shelves , it 's also typically heat treated to reduce its level of microbes , a government-sanctioned process that raw milk enthusiasts argue may reduce milk 's nutritional worth . milk spoilage is started by microbes , which consume and break down the nutrients in milk . that process causes butterfat to clump together , leading to a visually unpleasant product . and the byproducts of the microbes ' consumption are compounds that taste and smell nasty . but there 's a bigger problem . raw milk can carry microbes that are the sources of deadly diseases , so in order to kill as many of those microbes as possible , and keep milk fresh longer , we use a technique called pasteurization . one version of this process involves exposing milk to about 30 seconds of high heat . another version , called ultra-high temperature processing , or ultra pasteurization , blasts the milk with considerably higher temperatures over just a few seconds . uht milk boasts a much longer shelf life , up to twelve months unrefrigerated , compared to pasteurized milk 's two weeks in the fridge . that 's because the higher temperatures of uht processing inactivate far more microbes . yet the higher processing temperatures may adversely affect the nutritional and sensory properties of the milk . ultimately , that choice lies in the consumer 's taste and need for convenience . fortunately , there are many choices available in an industry that produces in excess of 840 million tons of products each year .

or it can be later added back to the liquid in varying proportions to yield different fat content milks . full fat milk , sometimes referred to as whole milk , has 3.25 % butterfat added compared to 1-2 % for low and reduced fat milk , and less than half a percent for skim milk . to stop reseparation of the fat from the water , or creaming , the mixture undergoes the high-energy pressurized process of homogenization .

____ ’ s milk is the most widely drank milk throughout the world .

around the globe , there are approximately 60 million people who have been forced to leave their homes to escape war , violence , and persecution . the majority of them have become internally displaced persons , which means they have fled their homes but are still within their own countries . others have crossed a border and sought shelter outside of their own countries . they are commonly referred to as refugees . but what exactly does that term mean ? the world has known refugees for millennia , but the modern definition was drafted in the un 's 1951 convention relating to the status of refugees in response to mass persecutions and displacements of the second world war . it defines a refugee as someone who is outside their country of nationality , and is unable to return to their home country because of well-founded fears of being persecuted . that persecution may be due to their race , religion , nationality , membership in a particular social group , or political opinion , and is often related to war and violence . today , roughly half the world 's refugees are children , some of them unaccompanied by an adult , a situation that makes them especially vulnerable to child labor or sexual exploitation . each refugee 's story is different , and many must undergo dangerous journeys with uncertain outcomes . but before we get to what their journeys involve , let 's clear one thing up . there 's a lot of confusion regarding the difference between the terms `` migrant '' and `` refugee . '' `` migrants '' usually refers to people who leave their country for reasons not related to persecution , such as searching for better economic opportunities or leaving drought-stricken areas in search of better circumstances . there are many people around the world who have been displaced because of natural disasters , food insecurities , and other hardships , but international law , rightly or wrongly , only recognizes those fleeing conflict and violence as refugees . so what happens when someone flees their country ? most refugee journeys are long and perilous with limited access to shelter , water , or food . since the departure can be sudden and unexpected , belongings might be left behind , and people who are evading conflict often do not have the required documents , like visas , to board airplanes and legally enter other countries . financial and political factors can also prevent them from traveling by standard routes . this means they can usually only travel by land or sea , and may need to entrust their lives to smugglers to help them cross borders . whereas some people seek safety with their families , others attempt passage alone and leave their loved ones behind with the hopes of being reunited later . this separation can be traumatic and unbearably long . while more than half the world 's refugees are in cities , sometimes the first stop for a person fleeing conflict is a refugee camp , usually run by the united nations refugee agency or local governments . refugee camps are intended to be temporary structures , offering short-term shelter until inhabitants can safely return home , be integrated to the host country , or resettle in another country . but resettlement and long-term integration options are often limited . so many refugees are left with no choice but to remain in camps for years and sometimes even decades . once in a new country , the first legal step for a displaced person is to apply for asylum . at this point , they are an asylum seeker and not officially recognized as a refugee until the application has been accepted . while countries by and large agree on one definition of refugee , every host country is responsible for examining all requests for asylum and deciding whether applicants can be granted the status of refugee . different countries guidelines can vary substantially . host countries have several duties towards people they have recognized as refugees , like the guarantee of a minimum standard of treatment and non-discrimination . the most basic obligation towards refugees is non-refoulement , a principle preventing a nation from sending an individual to a country where their life and freedom are threatened . in reality , however , refugees are frequently the victims of inconsistent and discriminatory treatment . they 're increasingly obliged to rebuild their lives in the face of xenophobia and racism . and all too often , they are n't permitted to enter the work force and are fully dependent on humanitarian aid . in addition , far too many refugee children are out of school due to lack of funding for education programs . if you go back in your own family history , chances are you will discover that at a certain point , your ancestors were forced from their homes , either escaping a war or fleeing discrimination and persecution . it would be good of us to remember their stories when we hear of refugees currently displaced , searching for a new home .

around the globe , there are approximately 60 million people who have been forced to leave their homes to escape war , violence , and persecution . the majority of them have become internally displaced persons , which means they have fled their homes but are still within their own countries . others have crossed a border and sought shelter outside of their own countries .

what is the difference between refugees and internally displaced persons ( idp ) ?

spray-painted subway cars , tagged bridges , mural-covered walls . graffiti pops up boldly throughout our cities . it can make statements about identity , art , empowerment , and politics , while simultaneously being associated with destruction . and , it turns out , it 's nothing new . graffiti , or the act of writing or scribbling on public property , has been around for thousands of years . and across that span of time , it 's raised the same questions we debate now : is it art ? is it vandalism ? in the 1st century bce , romans regularly inscribed messages on public walls , while oceans away , mayans were prolifically scratching drawings onto their surfaces . and it was n't always a subversive act . in pompeii , ordinary citizens regularly marked public walls with magic spells , prose about unrequited love , political campaign slogans , and even messages to champion their favorite gladiators . some , including the greek philosopher plutarch , pushed back , deeming graffiti ridiculous and pointless . but it was n't until the 5th century that the roots of the modern concept of vandalism were planted . at that time , a barbaric tribe known as the vandals swept through rome , pillaging and destroying the city . but it was n't until centuries later that the term vandalism was actually coined in an outcry against the defacing of art during the french revolution . and as graffiti became increasingly associated with deliberate rebellion and provocativeness , it took on its vandalist label . that 's part of the reason why , today , many graffiti artists stay underground . some assume alternate identities to avoid retribution , while others do so to establish comradery and make claim to territory . beginning with the tags of the 1960s , a novel overlap of celebrity and anonymity hit the streets of new york city and philadelphia . taggers used coded labels to trace their movements around cities while often alluding to their origins . and the very illegality of graffiti-making that forced it into the shadows also added to its intrigue and growing base of followers . the question of space and ownership is central to graffiti 's history . its contemporary evolution has gone hand in hand with counterculture scenes . while these movements raised their anti-establishment voices , graffiti artists likewise challenged established boundaries of public property . they reclaimed subway cars , billboards , and even once went so far as to paint an elephant in the city zoo . political movements , too , have used wall writing to visually spread their messages . during world war ii , both the nazi party and resistance groups covered walls with propaganda . and the berlin wall 's one-sided graffiti can be seen as a striking symbol of repression versus relatively unrestricted public access . as the counterculture movements associated with graffiti become mainstream , does graffiti , too , become accepted ? since the creation of so-called graffiti unions in the 1970s and the admission of select graffiti artists into art galleries a decade later , graffiti has straddled the line between being outside and inside the mainstream . and the appropriation of graffiti styles by marketers and typographers has made this definition even more unclear . the once unlikely partnerships of graffiti artists with traditional museums and brands , have brought these artists out of the underground and into the spotlight . although graffiti is linked to destruction , it 's also a medium of unrestricted artistic expression . today , the debate about the boundary between defacing and beautifying continues . meanwhile , graffiti artists challenge common consensus about the value of art and the degree to which any space can be owned . whether spraying , scrawling , or scratching , graffiti brings these questions of ownership , art , and acceptability to the surface .

political movements , too , have used wall writing to visually spread their messages . during world war ii , both the nazi party and resistance groups covered walls with propaganda . and the berlin wall 's one-sided graffiti can be seen as a striking symbol of repression versus relatively unrestricted public access . as the counterculture movements associated with graffiti become mainstream , does graffiti , too , become accepted ? since the creation of so-called graffiti unions in the 1970s and the admission of select graffiti artists into art galleries a decade later , graffiti has straddled the line between being outside and inside the mainstream .

you are walking along a city street and notice an open wall covered with graffiti , or as you drive through a local town , you notice the railroad overpass has been “ tagged. ” what is your initial response ? has this lesson changed your thoughts about this ? describe some local graffiti you may have seen in your area of the world .

translator : andrea mcdonough reviewer : bedirhan cinar i got in my first car accident when i was sixteen . i had just gotten my license and i was driving home when a car pulled into the intersection and bang ! it hit me . it had happened that quick . bang ! but when i play that memory back , it does n't take two seconds . i see the tires of the car rolling through the stop sign , i have time to think , `` you know , i think that car is going to hit me . '' i see the right-hand corner of the hood crumple up like tin foil , i see the red paint flake off and drift off into the air , i can see all of that , like it 's happening in slow motion . in my memory , that experience takes ten seconds . but why ? why did that memory play back longer than the actual time it took ? this is an interesting phenomenon and it 's not just for car accidents , a roller coaster , or a first kiss . these events seem to take longer than they actually take . but why ? and when it comes to writing about that experience , how do i get that peculiar feeling across ? how do i slow down time as a writer ? to get the answer , we have to visit hollywood . you see , the way filmmakers create slow motion will tell us a lot about how writers can create slow motion . first , let 's remember how film works . when the camera turns on , it 's not recording motion , it 's taking lots and lots of individual pictures . then when those pictures are played back in the projector , they blend together and create the appearance of motion , like a flip book . so , let 's imagine that a camera man needs to film his actress skipping through a field of daisies in regular motion . ready , action . she skips across the field , he records it , and ... cut . let 's say for the sake of easy math that our camera man took 50 pictures , 50 little frames on that length of film . now , let 's take that film and play it back at the rate of 50 frames per 5 seconds . this rate is constant , the projector will always go at the same speed . it 's easy , we got 50 frames , so our film takes 5 seconds . she skips across the field ... ... and cut ! so , then , how do we slow down time in film ? how do we create slow motion ? maybe this is a surprise , but we do n't take less pictures , we take more pictures . ready , action ! she skips across the field , he records it , and cut . now we have a lot of film , a long length , let 's say 100 frames long . now , when we play it back , it takes a longer time to get through , and there 's the actress in slow motion . skipping through the field of daisies ! which brings us now to writing . when you 're writing a narrative , you may want to use slow motion in one of your scenes . it 's a cool effect , just like it is in hollywood , and it draws the reader 's attention to important moments . well , here 's how you do it . you see , when we read , our brain makes the words into pictures and the pictures blend into action . so what we read is what we see in the time it takes us to read it . for example , imagine you 're writing a narrative about your game-winning free throw in the championship game . here 's a moment as a writer that you might want to slow down time to really capture the second-by-second tension produced by the scene . you concentrate , you put the pencil to paper , you really want to slow down time , you write , `` i shot the ball in the hoop . time slowed down . then we won . '' to read that , takes two seconds ; therefore , your reader imagines a scene that takes two seconds . ball goes up , comes down , done . see , even though you wrote , `` time slowed down , '' you did n't achieve that effect for your reader . just saying it does n't make it happen . now , let 's take what we make about film , time slows down with more pictures , and try again . this time write a lot more . `` i bent my knees and held the ball loosely . letting the ball bounce on the floor once more , i gathered my thoughts . this was the moment . my right arm extended as i released the ball with a gentle flick , it rotated slightly as it arched toward the rim . i held my breath . the ball nudged the back rim , falling through the net with a gentle , satisfying swish . and the crowd exploded from their seats . '' see , we just slowed down time through our writing . the bottom line is this : there are moments in life that take longer than they actually take . when you 're planning out your narrative , think about those moments , those snippets of life that took longer than the watch : the moment of hearing bad news , the moment of hearing good news , the moment of exhilaration when you realize you hit the jump , or the moment when you realize you are n't going to land it . once you identify these moments in your narrative , you can use this effect of slow motion when you write . just remember , it 's not enough to say , `` time slowed down '' and it 's not enough to throw a couple adjectives in a sentence and call it done either . descriptive writing is good writing , that 's true . but if you want to express the feeling of slow motion in life , you have to actually take up more physical space on the page , use more film so to speak . in doing so , you will create tension and keep your reader interested . and that way , the next time you write , you 'll control the camera of your own writing .

so , then , how do we slow down time in film ? how do we create slow motion ? maybe this is a surprise , but we do n't take less pictures , we take more pictures .

how do we make slow motion in film ?

interviewer : danica , how are you ? good , good . interviewer : nice to see you , what are you studying right now ? i 'm studying geometry . interviewer : holy cow , look at that . when i was in the ninth grade , i remember studying geometry theorems and saying , `` would n't it be cool to have a theorem named after me ? '' and i had no idea that one day , that would happen . intro winnie cooper ( character ) : hey kevin , hi paul ! paul ( character ) : winnie cooper ? ! winnie cooper was the girl next door . winnie cooper ( character ) : my real name is gwendolyn . she was the love interest , on again and off again of kevin arnold kevin arnold ( character ) : winnie will you go to the dance with me ? winnie cooper ( character ) : dance ? ... i ca n't her parents had a lot of issues . they 're separated and winnie had to move . it was a sort of deep sadness to winnie cooper . and it kind of helped kevin to appreciate his own family sometimes . winnie cooper was very smart . she scored better than -- kevin arnold on the sats . kevin arnold ( character ) : what exactly did you do get on your sats ? winnie cooper ( character ) : 725 verbal , 757 math . yeah . she was smart . clip : `` you fell in love with them five years ago . and you watched them grow up . -- the wonder years , a special one hour final episode . '' any child whose been on a very popular series knows that when it 's over , there 's a difficult period , where there 's a lot of insecurity . you 're so recognized for this one role . and then when that 's over , you start to wonder well , who else would i be if i did n't have this role ? so , i then went to ucla and in my mind i thought , okay , new chapter of my life , i 'm moving on . and of course , i got to the ucla campus and everybody was like `` hey winnie , where 's kevin ? '' it happened over and over and over again and i really just wanted to move on and figure out who i was . i was like , god you guys , this is hard enough , stop . i was going to be a film major . but i decided to take this math class . i was like , `` i do n't know if i can do this . '' i was afraid of it . i was afraid of it . i 'd gotten a five on the ap calculus bc exam , which is the highest score you can get on the most difficult calculus exam offered in high school . and i did n't think i 'd do well ? who did i think would do well ? somebody who looked the part more than me . when i took my first multivariable calculus class , i scored at the top of the class . a hundred and sixty three people . the professor actually graphed the scores on the chalkboard . i 'll never forget it . my score was the twenty two and then two fifteens and then it was nine and below . and i was stunned , i was floored , i could not believe that i 'd done so well . the professor came up to me and said , `` you have a gift in math . -- you should really pursue this . you should be a math major . '' ... .what ? a math major ? '' i thought that a math class in college would be hard enough . a couple days later , in that class , this kid tapped me on the shoulder and said `` excuse me are you that girl ? '' and that question always ends with , `` from tv ? '' or `` who played winnie ? '' he goes , `` excuse me , are n't you that girl who got the 22 ? i was like ... `` yes ... that is me . '' i became a calculus tutor in the department , i excelled in my classes and i loved it . i had the opportunity to co-author a research paper . we proved a new theorem . percolation and gibbs states multiplicity for ferromagnetic ashkin-teller models on z two . also known now as the chayes-mckellar-winn theorem . i discovered that i could be smart and capable and valuable for something that had nothing to do with hollywood . this is me . and it felt great .

interviewer : danica , how are you ? good , good . interviewer : nice to see you , what are you studying right now ?

why does danica say she did n't expect that she would be good at math ?

just a minute ago , this oil helped make a delicious meal possible . but now , it 's just some nasty goop . what should we do with it ? well , the easiest thing would be to pour it down the drain ; that makes it seem like it 's gone , but it 's not really gone . instead , it 's collecting bits of food and other random stuff , producing monstrous , greasy blockages that clog not only your own drain but entire sewage systems , causing flooding and pollution . many places have laws for proper disposal of grease , but we can go one step further . instead of just throwing it away safely , we can turn it into something useful . and if you 're wondering what anyone could possibly want with a bunch of digusting , used cooking oil , the answer is : biodiesel . you 've probably heard of diesel engines . they power farming and construction equipment , trucks , buses , ships , trains , backup generators , and even some cars . most of the fuel that feeds these engines is refined from petroleum , which comes from long-dead dinosaurs and other ancient fossils . but diesel fuel can also be derived from more recently-dead organisms , like plants and animals . and this type of fuel is what we call biodiesel . biodiesel is a biodegradable energy source , made from plant oils or animal fats , that can usually be burned in regular diesel engines . you guessed it , it 's the 'bio ' version of diesel . it 's cleaner than normal diesel , so there has been a push to generate it from crops like soybeans . now , growing plants for fuel , instead of food , comes with its own problems . but fortunately , we already have some oils and fats right here . preparing your used cooking grease for recycling is easy . first , let it cool down to room temperature . then , transfer it to a clean container . you can use any old bottles you have lying around , like milk jugs , as long as they 're completely empty , rinsed , and dried . use a funnel to avoid spills and a sieve to filter out any small food particles . you can even add bacon grease and other animal fats or the excess oil from canned food , like tuna or sardines , just make sure it 's really oil and not brine . so , what happens now that your oil is safely contained ? well , many cities have recycling services that will pick up large amounts of grease from restaurants and other establishments . but there are locations where individuals can drop off their containers , as well . all of this grease will end up at a processing plant , where it can be converted to useable biodiesel . how does this conversion work ? well , all these oils and fats you donated are made up of triglycerides , a glycerol molecule connected to three fatty acid chains . to convert fats to fuel , they react with an alcohol , usually methanol or ethanol , which produces long-chain esters and glycerol . to compare , here are some molecules of regular diesel fuel . now , here are the molecules we created by breaking apart the triglycerides . glycerol is the odd man out , so it 's removed at the end of the process . but look at these esters ! if you squint , their structures look pretty similar to those of the long-chain hydrocarbons in regular diesel . and diesel engines , with a few small modifications , can also be made to squint and burn these esters like regular diesel fuel . et voila ! biodiesel . now , you might be wondering whether all this hassle over recycling used cooking oil is even worth it . after all , how much energy can it possibly generate ? well , if all the grease that new yorkers throw away in one day were converted to jet fuel , it would be enough to power several hundred flights from new york to los angeles . and let 's not forget that using waste oil instead of burning more fossil fuels will limit our negative effects on the environment . recycling used cooking grease turns goop into good . by contributing a little bit , individuals and businesses can help create an alternative , stable source of diesel oil , while protecting the environment and keeping our cities cleaner . and that 's pretty slick .

et voila ! biodiesel . now , you might be wondering whether all this hassle over recycling used cooking oil is even worth it .

it seems a relatively easy task to collect used oil to produce biodiesel , yet most people find it really difficult to take the first step and stop throwing it down the drain . why do you think it is so difficult to change a behavior , and what strategies would you use to help someone to make that change ?

consider throwing a ball straight into the air . can you predict the motion of the ball after it leaves your hand ? sure , that 's easy . the ball will move upward until it gets to some highest point , then it will come back down and land in your hand again . of course , that 's what happens , and you know this because you have witnessed events like this countless times . you 've been observing the physics of everyday phenomena your entire life . but suppose we explore a question about the physics of atoms , like what does the motion of an electron around the nucleus of a hydrogen atom look like ? could we answer that question based on our experience with everyday physics ? definietly not . why ? because the physics that governs the behavior of systems at such small scales is much different than the physics of the macroscopic objects you see around you all the time . the everyday world you know and love behaves according to the laws of classical mechanics . but systems on the scale of atoms behave according to the laws of quantum mechanics . this quantum world turns out to be a very strange place . an illustration of quantum strangeness is given by a famous thought experiment : schrödinger 's cat . a physicist , who does n't particularly like cats , puts a cat in a box , along with a bomb that has a 50 % chance of blowing up after the lid is closed . until we reopen the lid , there is no way of knowing whether the bomb exploded or not , and thus , no way of knowing if the cat is alive or dead . in quantum physics , we could say that before our observation the cat was in a superposition state . it was neither alive nor dead but rather in a mixture of both possibilities , with a 50 % chance for each . the same sort of thing happens to physical systems at quantum scales , like an electron orbiting in a hydrogen atom . the electron is n't really orbiting at all . it 's sort of everywhere in space , all at once , with more of a probability of being at some places than others , and it 's only after we measure its position that we can pinpoint where it is at that moment . a lot like how we did n't know whether the cat was alive or dead until we opened the box . this brings us to the strange and beautiful phenomenon of quantum entanglement . suppose that instead of one cat in a box , we have two cats in two different boxes . if we repeat the schrödinger 's cat experiment with this pair of cats , the outcome of the experiment can be one of four possibilities . either both cats will be alive , or both will be dead , or one will be alive and the other dead , or vice versa . the system of both cats is again in a superposition state , with each outcome having a 25 % chance rather than 50 % . but here 's the cool thing : quantum mechanics tells us it 's possible to erase the both cats alive and both cats dead outcomes from the superposition state . in other words , there can be a two cat system , such that the outcome will always be one cat alive and the other cat dead . the technical term for this is that the states of the cats are entangled . but there 's something truly mindblowing about quantum entanglement . if you prepare the system of two cats in boxes in this entangled state , then move the boxes to opposite ends of the universe , the outcome of the experiment will still always be the same . one cat will always come out alive , and the other cat will always end up dead , even though which particular cat lives or dies is completely undetermined before we measure the outcome . how is this possible ? how is it that the states of cats on opposite sides of the universe can be entangled in this way ? they 're too far away to communicate with each other in time , so how do the two bombs always conspire such that one blows up and the other does n't ? you might be thinking , `` this is just some theoretical mumbo jumbo . this sort of thing ca n't happen in the real world . '' but it turns out that quantum entanglement has been confirmed in real world lab experiments . two subatomic particles entangled in a superposition state , where if one spins one way then the other must spin the other way , will do just that , even when there 's no way for information to pass from one particle to the other indicating which way to spin to obey the rules of entanglement . it 's not surprising then that entanglement is at the core of quantum information science , a growing field studying how to use the laws of the strange quantum world in our macroscopic world , like in quantum cryptography , so spies can send secure messages to each other , or quantum computing , for cracking secret codes . everyday physics may start to look a bit more like the strange quantum world . quantum teleportation may even progress so far , that one day your cat will escape to a safer galaxy , where there are no physicists and no boxes .

everyday physics may start to look a bit more like the strange quantum world . quantum teleportation may even progress so far , that one day your cat will escape to a safer galaxy , where there are no physicists and no boxes .

systems can be entangled even if they are too far apart from each other for communication to explain the effect . in light of this , think of an underlying mechanism that could explain entanglement .

how fast are you moving right now ? that seems like an easy question . the first tempting answer is , `` i 'm not moving . '' upon further reflection , you realize that maybe the earth 's motion counts . so , a second tempting answer is , `` 19 miles/second around the sun . '' but then you recall learning that the sun moves around the center of the milky way galaxy , and the milky way moves within the local group of galaxies , and the local group moves within the virgo cluster , and the virgo cluster moves within ... `` how fast are you moving ? '' is not an easy question . when mission control tells astronauts how fast they 're going , there 's always an assumed standard of rest . at the start of the voyage , speeds are given relative to the launchpad . but later , when the launchpad is just one more arbritrary place down there on earth 's spinning surface , speeds are given relative to the idealized , non-spinning pinpoint center of earth . on their way to the moon , apollo astronauts had a hard time answering the question , `` how fast are you moving ? '' speed away from earth was one thing , and speed toward the moon was quite another . that 's because the earth and the moon move relative to one another . ah , of course ! speed is a relative quantity . when captain kirk ask lieutenant sulu if the starship enterprise has reached a speed of warp 7 , sulu should reply , `` relative to what , captain ? '' such a sassy reply may get subordinate starfleet officers in trouble , but it is the only good answer to the question , `` how fast are you moving ? '' this is basic relatively talking . not fancy einsteinian relativity , but good old fashioned ( and still correct ) galilean relativity . galileo seems to have been the first person to realize that there is no such thing as an absolute speed . speeds are relative . this means that speeds only have meaning when they are referred to a reference frame . presumably that reference frame is itself at rest . but then we have to ask again , `` at rest relative to what ? '' because even the concept of rest has lost any hint of absolute meaning . speed is relative , and rest is relative . earth 's speed is 19 miles/second relative to the sun . the enterprise 's speed is warp 7 relative to the center of the milky way galaxy . your speed is zero relative to your easy chair . but depending on where you sit , it is hundreds of miles/hour relative to earth 's center . when we furrow a brow and ask , `` but how fast is earth really moving ? '' we imagine spaceship earth plowing through the ocean of space as it orbits the sun . but space is not an ocean . it has no substance as water does . space is not a thing ; space is nothing . space is no thing . you can move between two points in space , say between earth and mars , but you ca n't move through space . there 's nothing to move through . it 's like trying to say how much a hole weighs . a hole weighs exactly nothing because a hole is nothing . it 's a void , and so is space . to move relative to nothing is meaningless . the concepts of speed and of rest have only relative meaning . they are absolutely meaningless . they mean something only with respect to arbitrarily chosen , artificial frames of reference . if , someday , you are buckled into your spaceship , and you see from the side window , say , a space station whizz by at constant speed , there is no way to know which of you is really moving . neither of you is really moving because there is no deep reality about constant speed . constant speed in a straight line has only relative meaning , a kind of relative reality . does this mean that all motion is relative ? no ! some motions have only relative meaning , but some motions have absolute meaning , are absolutely real . for example , constant speed is relative , but change in speed is absolute . calling something absolute in science means that arbitrary standards are not used in its measurement . it is unambiguously measurable . when your spaceship fires its engines , your change in speed is beyond doubt . you feel it in your stomach , and your ship 's sensors can measure it . outside your window , the passing space station may seem to be changing speed , but the beings inside the station will not feel it . and no sensors can measure it . you are really changing speed , and they are really are not . there 's something absolutely real about changes in speed . the same goes for rotation . if your spaceship is spinning , you can feel it , and your ship 's sensors can measure it . the space station outside may seem to be going around you , but it is you who feels queasy , not the folks in the space station . you are really spinning , and they really are not . there 's something absolutely real about rotation . so , some motions are relative , and some are not . there is no deep reality about constant speed , but changes in speed are deeply real , and so are rotations . we have to be thoughtful in our analysis of everyday experience in order to identify what is deeply real . since we can be fooled by perceptions as basic as speed , maybe every perception deserves careful scrutiny . this is what inspired einstein to his incredible insights about the speed of light and forward time travel . knowing how to identify what is deeply real is tough and important work . if a police officer ever pulls you over for speeding and asks , & amp ; amp ; quot ; do you know how fast you were going ? & amp ; amp ; quot ; an insightful , though perhaps unwise , reply would be , `` relative to what ? '' and then , as you sit in the backseat of the police car and feel it accelerate toward jail , you can add , & amp ; amp ; quot ; but some things are absolute ! & amp ; amp ; quot ;

no ! some motions have only relative meaning , but some motions have absolute meaning , are absolutely real . for example , constant speed is relative , but change in speed is absolute .

which of these has no hint of absolute meaning , only relative meaning ?

each time you take a step , 200 muscles work in unison to lift your foot , propel it forward , and set it down . it 's just one of the many thousands of tasks performed by the muscular system . this network of over 650 muscles covers the body and is the reason we can blink , smile , run , jump , and stand upright . it 's even responsible for the heart 's dependable thump . first , what exactly is the muscular system ? it 's made up of three main muscle types : skeletal muscle , which attaches via tendons to our bones , cardiac muscle , which is only found in the heart , and smooth muscle , which lines the blood vessels and certain organs , like the intestine and uterus . all three types are made up of muscle cells , also known as fibers , bundled tightly together . these bundles receive signals from the nervous system that contract the fibers , which in turn generates force and motion . this produces almost all the movements we make . some of the only parts of the body whose motions are n't governed by the muscular system are sperm cells , the hair-like cilia in our airways , and certain white blood cells . muscle contraction can be split into three main types . the first two , shortening muscle fibers and lengthening them , generate opposing forces . so the biceps will shorten while the triceps will lengthen or relax , pulling up the arm and making it bend at the elbow . this allows us to , say , pick up a book , or if the muscle relationship is reversed , put it down . this complementary partnership exists throughout the muscular system . the third type of contraction creates a stabilizing force . in these cases , the muscle fibers do n't change in length , but instead keep the muscles rigid . this allows us to grip a mug of coffee or lean against a wall . it also maintains our posture by holding us upright . skeletal muscles form the bulk of the muscular system , make up about 30-40 % of the body 's weight , and generate most of its motion . some muscles are familiar to us , like the pectorals and the biceps . others may be less so , like the buccinator , a muscle that attaches your cheek to your teeth , or the body 's tiniest skeletal muscle , a one-millimeter-long tissue fragment called the stapedius that 's nestled deep inside the ear . wherever they occur , skeletal muscles are connected to the somatic nervous system , which gives us almost complete control over their movements . this muscle group also contains two types of muscle fibers to refine our motions even further , slow-twitch and fast-twitch . fast-twitch fibers react instantly when triggered but quickly use up their energy and tire out . slow-twitch fibers , on the other hand , are endurance cells . they react and use energy slowly so they can work for longer periods . a sprinter will accumulate more fast-twitch muscles in her legs through continuous practice , enabling her to quickly , if briefly , pick up the pace , whereas back muscles contain more slow-twitch muscles to maintain your posture all day . unlike the skeletal muscles , the body 's cardiac and smooth muscles are managed by the autonomic nervous system beyond our direct control . that makes your heart thump roughly 3 billion times over the course of your life , which supplies the body with blood and oxygen . autonomic control also contracts and relaxes smooth muscle in a rhythmic cycle . that pumps blood through the smooth internal walls of blood vessels , enables the intestine to constrict and push food through the digestive system , and allows the uterus to contract when a person is giving birth . as muscles work , they also use energy and produce an important byproduct , heat . in fact , muscle provides about 85 % of your warmth , which the heart and blood vessels then spread evenly across the body via the blood . without that , we could n't maintain the temperature necessary for our survival . the muscular system may be largely invisible to us , but it leaves its mark on almost everything we do , whether it 's the blink of an eye or a race to the finish line .

muscle contraction can be split into three main types . the first two , shortening muscle fibers and lengthening them , generate opposing forces . so the biceps will shorten while the triceps will lengthen or relax , pulling up the arm and making it bend at the elbow .

if our muscles didn ’ t generate opposing forces , in what specific ways would that limit us ?

the first standardized tests that we know of were administered in china over 2,000 years ago during the han dynasty . chinese officials used them to determine aptitude for various government posts . the subject matter included philosophy , farming , and even military tactics . standardized tests continued to be used around the world for the next two millennia , and today , they 're used for everything from evaluating stair climbs for firefighters in france to language examinations for diplomats in canada to students in schools . some standardized tests measure scores only in relation to the results of other test takers . others measure performances on how well test takers meet predetermined criteria . so the stair climb for the firefighter could be measured by comparing the time of the climb to that of all other firefighters . this might be expressed in what many call a bell curve . or it could be evaluated with reference to set criteria , such as carrying a certain amount of weight a certain distance up a certain number of stairs . similarly , the diplomat might be measured against other test-taking diplomats , or against a set of fixed criteria , which demonstrate different levels of language proficiency . and all of these results can be expressed using something called a percentile . if a diplomat is in the 70th percentile , 70 % of test takers scored below her . if she scored in the 30th percentile , 70 % of test takers scored above her . although standardized tests are sometimes controversial , they 're simply a tool . as a thought experiment , think of a standardized test as a ruler . a ruler 's usefulness depends on two things . first , the job we ask it to do . our ruler ca n't measure the temperature outside or how loud someone is singing . second , the ruler 's usefulness depends on its design . say you need to measure the circumference of an orange . our ruler measures length , which is the right quantity , but it has n't been designed with the flexibility required for the task at hand . so , if standardized tests are given the wrong job , or are n't designed properly , they may end up measuring the wrong things . in the case of schools , students with test anxiety may have trouble performing their best on a standardized test , not because they do n't know the answers , but because they 're feeling too nervous to share what they 've learned . students with reading challenges may struggle with the wording of a math problem , so their test results may better reflect their literacy rather than numeracy skills . and students who were confused by examples on tests that contain unfamiliar cultural references may do poorly , telling us more about the test taker 's cultural familiarity than their academic learning . in these cases , the tests may need to be designed differently . standardized tests can also have a hard time measuring abstract characteristics or skills , such as creativity , critical thinking , and collaboration . if we design a test poorly , or ask it to do the wrong job , or a job it 's not very good at , the results may not be reliable or valid . reliability and validity are two critical ideas for understanding standardized tests . to understand the difference between them , we can use the metaphor of two broken thermometers . an unreliable thermometer gives you a different reading each time you take your temperature , and the reliable but invalid thermometer is consistently ten degrees too hot . validity also depends on accurate interpretations of results . if people say results of a test mean something they do n't , that test may have a validity problem . just as we would n't expect a ruler to tell us how much an elephant weighs , or what it had for breakfast , we ca n't expect standardized tests alone to reliably tell us how smart someone is , how diplomats will handle a tough situation , or how brave a firefighter might turn out to be . so standardized tests may help us learn a little about a lot of people in a short time , but they usually ca n't tell us a lot about a single person . many social scientists worry about test scores resulting in sweeping and often negative changes for test takers , sometimes with long-term life consequences . we ca n't blame the tests , though . it 's up to us to use the right tests for the right jobs , and to interpret results appropriately .

the subject matter included philosophy , farming , and even military tactics . standardized tests continued to be used around the world for the next two millennia , and today , they 're used for everything from evaluating stair climbs for firefighters in france to language examinations for diplomats in canada to students in schools . some standardized tests measure scores only in relation to the results of other test takers . others measure performances on how well test takers meet predetermined criteria . so the stair climb for the firefighter could be measured by comparing the time of the climb to that of all other firefighters .

standardized tests are used to measure learning in many countries around the world . what are some other methods that schools might use ? what are the advantages and disadvantages of these other methods ?

`` all men are created equal and they are endowed with the rights to life , liberty and the pursuit of happiness . '' not so fast , mr. jefferson ! these words from the declaration of independence , and the facts behind them , are well known . in june of 1776 , a little more than a year after the war against england began with the shots fired at lexington and concord , the continental congress was meeting in philadelphia to discuss american independence . after long debates , a resolution of independence was approved on july 2 , 1776 . america was free ! and men like john adams thought we would celebrate that date forever . but it was two days later that the gentlemen in congress voted to adopt the declaration of independence , largely written by thomas jefferson , offering all the reasons why the country should be free . more than 235 years later , we celebrate that day as america 's birthday . but there are some pieces of the story you may not know . first of all , thomas jefferson gets the credit for writing the declaration , but five men had been given the job to come up with a document explaining why america should be independent : robert livingston , roger sherman , benjamin franklin and john adams were all named first . and it was adams who suggested that the young , and little known , thomas jefferson join them because they needed a man from the influential virginia delegation , and adams thought jefferson was a much better writer than he was . second , though jefferson never used footnotes , or credited his sources , some of his memorable words and phrases were borrowed from other writers and slightly tweaked . then , franklin and adams offered a few suggestions . but the most important change came after the declaration was turned over to the full congress . for two days , a very unhappy thomas jefferson sat and fumed while his words were picked over . in the end , the congress made a few , minor word changes , and one big deletion . in the long list of charges that jefferson made against the king of england , the author of the declaration had included the idea that george the third was responsible for the slave trade , and was preventing america from ending slavery . that was not only untrue , but congress wanted no mention of slavery in the nation 's founding document . the reference was cut out before the declaration was approved and sent to the printer . but it leaves open the hard question : how could the men , who were about to sign a document , celebrating liberty and equality , accept a system in which some people owned others ? it is a question that would eventually bring the nation to civil war and one we can still ask today .

then , franklin and adams offered a few suggestions . but the most important change came after the declaration was turned over to the full congress . for two days , a very unhappy thomas jefferson sat and fumed while his words were picked over .

according to the narrator , congress eliminated from the declaration a reference to :

translator : marcia de brito reviewer : ariana bleau lugo ( guitar music throughout ) music is a language . both music and verbal languages serve the same purpose . they are both forms of expression . they can be used as a way to communicate with others . they can be read and written . they can make you laugh or cry , think or question , and can speak to one or many . and both can definitely make you move . in some instances , music works better than the spoken word , because it does n't have to be understood to be effective . although many musicians agree that music is a language , it is rarely treated as such . many of us treat it as something that can only be learned by following a strict regimen , under the tutelage of a skilled teacher . this approach has been followed for hundreds of years with proven success , but it takes a long time . too long . think about the first language you learn as a child . more importantly , think about how you learned it . you were a baby when you first started speaking , and even though you spoke the language incorrectly you were allowed to make mistakes . and the more mistakes you made , the more your parents smiled . learning to speak was not something you were sent somewhere to do only a few times a week . and the majority of the people you spoke to were not beginners . they were already proficient speakers . imagine your parents forcing you to only speak to other babies until you were good enough to speak to them . you would probably be an adult before you could carry on a proper conversation . to use a musical term , as a baby , you were allowed to jam with professionals . if we approach music in the same natural way we approached our first language , we will learn to speak it in the same short time it took to speak our first language . proof of this could be seen in almost any family where a child grows up with other musicians in the family . here are a few keys to follow in learning or teaching music . in the beginning , embrace mistakes , instead of correcting them . like a child playing air guitar , there are no wrong notes . allow young musicians to play and perform with accomplished musicians on a daily basis . encourage young musicians to play more than they practice . the more they play the more they will practice on their own . music comes from the musician , not the instrument . and most importantly , remember that a language works best when we have something interesting to say . many music teachers never find out what their students have to say . we only tell them what they are supposed to say . a child speaks a language for years before they even learn the alphabet . too many rules at the onset , will actually slow them down . in my eyes , the approach to music should be the same . after all , music is a language too .

like a child playing air guitar , there are no wrong notes . allow young musicians to play and perform with accomplished musicians on a daily basis . encourage young musicians to play more than they practice . the more they play the more they will practice on their own .

wooten says that beginning musicians should play more than they practice . do you agree ? why or why not ?

you 're facing a giant bowl of energy packed carbon crunchies . one spoonful . two . three . soon , you 're powered up by the energy surge that comes from your meal . but how did that energy get into your bowl ? energy exists in the form of sugars made by the plant your cereal came from , like wheat or corn . as you can see , carbon is the chemical backbone , and plants get their fix of it in the form of carbon dioxide , co2 , from the air that we all breath . but how does a plant 's energy factory , housed in the stroma of the chloroplast , turn a one carbon gas , like co2 , into a six carbon solid , like glucose ? if you 're thinking photosynthesis , you 're right . but photosynthesis is divided into two steps . the first , which stores energy from the sun in the form of adenosine triphosphate , or atp . and the second , the calvin cycle , that captures carbon and turns it into sugar . this second phase represents one of nature 's most sustainable production lines . and so with that , welcome to world 's most miniscule factory . the starting materials ? a mix of co2 molecules from the air , and preassembled molecules called ribulose biphosphate , or rubp , each containing five carbons . the initiator ? an industrious enzyme named rubisco that welds one carbon atom from a co2 molecule with the rubp chain to build an initial six carbon sequence . that rapidly splits into two shorter chains containing three carbons each and called phosphoglycerates , or pgas , for short . enter atp , and another chemical called nicotinamide adenine dinucleotide phosphate , or just nadph . atp , working like a lubricant , delivers energy , while nadph affixes one hydrogen to each of the pga chains , changing them into molecules called glyceraldehyde 3 phosphates , or g3ps . glucose needs six carbons to form , made from two molecules of g3p , which incidentally have six carbons between them . so , sugar has just been manufactured , right ? not quite . the calvin cycle works like a sustainable production line , meaning that those original rubps that kicked things off at the start , need to be recreated by reusing materials within the cycle now . but each rubp needs five carbons and manufacturing glucose takes a whole six . something does n't add up . the answer lies in one phenomenal fact . while we 've been focusing on this single production line , five others have been happening at the same time . with six conveyor belts moving in unison , there is n't just one carbon that gets soldered to one rubp chain , but six carbons soldered to six rubps . that creates 12 g3p chains instead of just two , meaning that all together , 36 carbons exist : the precise number needed to manufacture sugar , and rebuild those rubps . of the 12 g3ps pooled together , two are siphoned off to form that energy rich six carbon glucose chain . the one fueling you via your breakfast . success ! but back on the manufacturing line , the byproducts of this sugar production are swiftly assembled to recreate those six rubps . that requires 30 carbons , the exact number contained by the remaining 10 g3ps . now a molecular mix and match occurs . two of the g3ps are welded together forming a six carbon sequence . by adding a third g3p , a nine carbon chain is built . the first rubp , made up of five carbons , is cast from this , leaving four carbons behind . but there 's no wastage here . those are soldered to a fourth g3p molecule , making a seven carbon chain . added to a fifth g3p molecule , a ten carbon chain is created , enough now to craft two more rubps . with three full rubps recreated from five of the ten g3ps , simply duplicating this process will renew the six rubp chains needed to restart the cycle again . so the calvin cycle generates the precise number of elements and processes required to keep this biochemical production line turning endlessly . and it 's just one of the 100s of cycles present in nature . why so many ? because if biological production processes were linear , they would n't be nearly as efficient or successful at using energy to manufacture the materials that nature relies upon , like sugar . cycles create vital feedback loops that repeatedly reuse and rebuild ingredients crafting as much as possible out of the planet 's available resources . such as that sugar , built using raw sunlight and carbon converted in plant factories to become the energy that powers you and keeps the cycles revolving in your own life .

you 're facing a giant bowl of energy packed carbon crunchies . one spoonful . two .

how many repeats of the calvin cycle are needed to make one glucose molecule ?

[ go project films ] i think that facing death changes people ... which is what happened with me . before this experience , i was a completely different person with a completely different dream . my last dream which was to treat cancer and right now my dream of changing the world in another way . [ welcome to canada ] [ over 4.8 million syrians are refugees living in neighboring countries . ] [ 6.5 million more are displaced within syria . ] [ in november 2015 , the government of canada promised ] [ to resettle 25,000 syrian refugees within 6 months . ] [ the 2400 court motel in vancouver is one of 9 temporary housing sites ] [ for the newly arrived refugees . ] [ may 2016 , vancouver , canada ] staying at the motel is this hard transitional stage . you are homesick and you 're also thinking about remaining family members overseas living under horrendous circumstances . i try my best to introduce the new reality . i try my best to ease the impact of their resettlement process as refugees , as someone who did n't choose to come here , as someone who had to come here . hi , my name is mohammed from immigrant services society of british columbia , iss of bc contacting you regarding your place on craigslist . [ tell me we have three children . ] you 're looking at the two bedroom or the three bedroom ? - two bedroom , two bedroom . - two bedroom ? okay . - oh , two bedroom ? - the two bedroom , yeah . how many people you have ? a family of five people with three small kids . - yeah , that too many . - that is too many ? [ she 's telling you that 's too many people . ] [ okay , tell her thank you ... they are young . ] thank you . i 'm with my clients right now . so i 'm helping him . he wants to share with you , the kids are so small and the ages are ... the place is too small for five people . oh , oh , i see . [ - she 's saying the house is too small to fit five people . ] [ - what about the 3 bedroom ... what 's the rental cost ? ] okay , what about the three bedroom that you have ? $ 3,500 a month . that will be expensive for a new immigrant family . is it possible for you to see the kids and ... i can not accommodate five people in that place . yeah , thank you so much . i 'm sorry . [ the two bedroom house , it 's too small to accommodate five people . ] [ the other house with 3 bedrooms , it 's too expensive , it 's $ 3,500 a month . ] moving to canada is not easy at all . my job is all about providing first language services [ oh my god . ] to the newly arrived refugees . [ we 're going to try and find you another house . ] i 'm the person who welcomes them and i will help them with everything that they will need in their resettlement process . it 's really hard to explain the reality on the ground in syria . it keeps on changing on a daily basis . syrians are just caught up in the middle of this non-sense chaos . many of them have spent many years in refugee camps in neighboring countries trying to just wait for this crazy war to finish . when they realized it 's going to be much longer , this syrian refugee crisis started . [ this is a transitional stage and it 's very difficult . ] [ i was just like you when i came here . ] [ the same reception center , same counselor ] [ and even signed the same papers . ] [ attended the same orientation , and was looking for a house . ] [ so you have been through this before . ] [ the exact same thing . ] [ -i would not encourage you to work right away ] [ -of course not , i need to learn the language first . ] [ excellent thinking . focus on english . ] [ your life starts tomorrow . ] [ god willing , we will start a new life tomorrow . ] before 2011 , before everything has started , we were living a happy life . i was born in al-hasakah , syria , a very peaceful city , a city of so many languages , ethnic components , and religious components with the idea and the notion of accepting others . i was in my fourth year of my medical studies in syria , i was trying my best to become a doctor , and my dream was to treat cancer . my generation was dreaming of having freedom , having some basic things that the average canadian would not think about . [ filmed by mohammed in homs , syria ] we never thought we could have faced such a brutal , barbaric response from your own government , just for gathering in the street and shouting the word `` freedom . '' we were just standing there and surprisingly they started shooting and people started falling ... at that point everyone started running , everyone who had survived it , started running , and some people were just on the ground covered with blood . i 'm calling you regarding clients of mine who are moving to your place tomorrow morning . [ -what 's happening in aleppo is breaking my heart . ] [ -a lot of problems are happening there . ] yeah , because we 're in the middle of , you know , arranging all the transportation needed for all of these families . all righty . thank you so much . [ this boy is dying . ] [ i want my brother . where is my mother and father ? ] [ where is my mom ? ] [ say , `` there is no god but god . '' ] for syrians , it is so normal to open your facebook and see the death of your friend on social media . it is something that is really hard and that is really difficult to accept , to observe , and to even think about . [ there is no power except what lies in god 's hands . ] i 'm about to turn 27 next month . in this small lifetime , i have been arrested three times . i have been in five different detention places . the first thing that they did in the detention center was hanging me from the ceiling . they had handcuffs on my hands like this and they had a chain coming down from the ceiling , and they have hooked that chain to my hands like this , and they kept me like this for three days . after spending three days like this , the actual torture started . they spent so many days practicing all kinds of torture on me , and on other syrian people , in that detention center . i can never forget this old man who was sleeping next to me ... he used to say , `` you see all of this ... one day , all of this will be just a story that you will be telling to other people . '' after 120 days of torture , i was finally released ... i was finally able to see sunlight again . the only thing that i wanted to do is talk to my family . i just wanted to see them but also say goodbye to them ... get the hell out of there and never look back . i took a taxi from damascus to beirut where there was no shelling , no explosions , just a normal life ... three hours away from where i was , from where i was tortured , it was unbelievable for me . iss of bc kingsway . good morning . syrians in lebanon are not allowed to work , are not allowed to go to school . syrians in lebanon are simply not welcomed . the best job that i could find was washing cars from 9 am to 9 pm for $ 20 a day . i was just struggling to have a life . my whole life changed with a single phone call . i pick up the phone , it was this same phone . so i pick up and i was told that , `` this is the canadian embassy calling for mohammed alsaleh , '' i was like , `` yes , speaking . '' so they told me , `` we have an application on your behalf to come to canada , are you interested ? '' and i was like , `` yes , i 'm . '' [ in november 2014 mohammed was granted asylum in canada and arrived in vancouver . ] [ to date thousands of syrian families have arrived in canada . ] each syrian family is thinking about someone who 's left behind ... if it was a brother , if it was a mother , or if it was a father . this is something that i can see among the people that i 'm helping , and this is something that i can relate to on a personal level because of the situation of my family . my family had to illegally cross the border between syria and turkey . they had to crawl in the mud in order to make it to safety . come on , pick up . [ hello . ] [ hello ... hello . ] [ hello , mama . ] [ how are you , mother ? ] [ i swear we miss you . we miss you so much . ] [ me too . i miss you so so much . ] [ shahad , what is this beautiful hair ? ] [ this is the new style , with these bangs . ] [ wow , look , look your hair is so long now . ] when i last saw my family , my youngest sister was seven , right now she is ten , and i do n't know how old would she be when i meet her . it 's really hard to know that you might not be able to meet them . [ look at how my hair looks . ] [ güzel ! güzel like the turkish say . ] [ are you learning turkish ? ] [ a little bit , not much yet . ] [ we try a little bit when we go out , things like that . ] [ -great . ] [ even though we are in turkey , the situation is tough here . ] [ we are always stressed and tired . life is hard here . ] [ what 's important is that you guys are safe and sound ] [ and you are not in danger , ] [ and we do n't have to worry about your life being in danger . ] [ and that 's the most important thing right now , ] [ to let these few months pass while everything is processed and you get here . ] [ god willing , because the situation here is n't comfortable and one does n't feel at home . ] [ -yes , yes . -you always feel like something is missing . ] [ god willing , we will all be together soon here in canada . ] [ that 's what we hope for . hopefully everything will work out . ] [ i miss you so so so much . ] in order for people to get settled and to feel like home , i think the only missing part is time . they just need time . [ speaking foreign language ] [ welcome , welcome to our new house . ] [ a hundred congratulations on the new house , it 's a lovely home . ] [ god bless you , it 's lovely having you all here . ] my first client was a family of 13 people who have just came to canada . [ the best thing you did was to get this property . ] [ here you can play , whatever you want is here . ] i was telling them , `` you 're safe now . one year ago , i was standing exactly where you are and right now i 'm helping you , so do n't worry everything 's going to be fine . '' i want everyone to realize how tremendous , how beautiful it is to offer people a place to call home ... which is something priceless that i really , really appreciate having right now . it 's heart breaking to see the country that you grew up in get destroyed . i 'm one of the ones lucky enough to come back from the dead , to tell their stories , to share their suffering with the rest of the world , which is something that i think is part of my obligation toward syrians and toward canadians . [ mohammed continues to support his family as he works to bring them safely to canada . ] [ according to the un , approximately 250,000 people ] [ have been killed in syria and 13.5 million people are in urgent need of humanitarian assistance . ] [ to date , 29,817 syrian refugees have been welcomed to canada . ] [ 2016 go project films ]

my last dream which was to treat cancer and right now my dream of changing the world in another way . [ welcome to canada ] [ over 4.8 million syrians are refugees living in neighboring countries . ] [ 6.5 million more are displaced within syria . ]

according to the film , approximately how many syrians are refugees living in neighboring countries ?

energy is not easy to define . things have energy , but you ca n't hold a bushel of energy in your hands . you can see what it does , but you ca n't see it directly . there are different types of energy , but the differences between them are manifested only in how they make stuff behave . we do know that the total amount of all the different types of energy in the universe is always the same . and , for chemists , two important types of energy are chemical potential energy and kinetic energy . potential energy is energy waiting to happen . think of a stretched rubber band . if you cut it , all that potential energy gets converted to kinetic energy , which is registered by you as pain . like a stretched rubber band , chemical bonds also store energy , and when those bonds are broken , that potential energy gets converted to other types of energy , like heat or light , or gets used to make different bonds . kinetic energy is the energy of motion , and molecules are always moving . they 're not necessarily going somewhere , though they could be , but they are vibrating , stretching , bending , and/or spinning . take methane , which is four hydrogens attached to a central carbon , as an example . drawn on paper , it 's just a still tetrahedron . but in real life , it 's a jiggling mess . the kinetic energy of molecules is exactly the same type of energy as the energy you have when you 're moving around , except that you can be still and molecules ca n't . if you suck the kinetic energy out of a group of molecules , they 'll move less , but they 'll never fully stop . now , in any group of molecules , some will have more kinetic energy than others . and if we calculate the average kinetic energy of the group , we 'd have a number mathematically related to temperature . so , the more kinetic energy a group of molecules has , the higher its temperature . and that means that on a hot day , the molecules in the air around you are spinning , stretching , bending , and generally shooting around much faster than on a cold day . now , hot and cold , by the way , are relative terms . they 're always used to compare one thing to something else . so , on that hot summer day , the air molecules have more kinetic energy than the molecules in your skin . so , when those air molecules crash into you , they transfer some of their energy to the molecules in your skin , and you feel that as heat . on a cold day , the air molecules have less kinetic energy than the molecules in your skin , so when you crash into those air molecules , you actually transfer some of your kinetic energy to them , and you feel that as cold . you can trace the path of energy around you . try it at your next cookout . you burn charcoal and the release of that chemical potential energy shows up as extreme heat and light . the heat then makes the molecules of your burgers , your hot dogs , or your vegetables vibrate until their own bonds break and new chemical structures are formed . too much heat and you have a charred mess ; just enough and you have dinner . once in your body , the food molecules in your delicious , or charred , dinner get broken down , and the energy released is used to either keep you alive right now or it 's stored for later in different molecules . as night falls , the hot summer air cools and the flow of energy into you slows . then , as the air reaches your skin temperature , for the briefest of moments , the flow stops . and then it starts up again in the opposite direction as energy leaves the warmer surface of your skin to return to the universe around you , that energy , neither created nor destroyed , but ever shape-shifting , the chameleon phoenix of our physical world .

energy is not easy to define . things have energy , but you ca n't hold a bushel of energy in your hands .

if a piece of metal at 70 degrees touches a piece of metal at 40 degrees , ________ .

hi i ’ m john green , this is crash course us history , and today we 're going to tell the story of how a group of plucky english people struck a blow for religious freedom , and founded the greatest , freest and fattest nation the world has ever seen . [ libertage ] these brits entered a barren land containing no people , and quickly invented the automobile , baseball and star trek and we all lived happily ever after . mr. green , mr. green , if it is really that simple , i am so getting an a in this class . oh , me from the past , you 're just a delight . [ theme music ] so most americans grew up hearing that the united states was founded by pasty english people who came here to escape religious persecution . and that 's true of the small proportion of people who settled in the massachusetts bay and created what we now know is new england . but these pilgrims and puritans , there 's a difference , weren ’ t the first people or even the first europeans to come to the only part of the globe we did n't paint over . in fact they weren ’ t the first english people . the first english people came to virginia . off topic but how weird is it that the first permanent english colony in the americas was named not for queen elizabeth ’ s epicness but for her supposed chastity . right anyway , those first english settlers were n't looking for religious freedom , they wanted to get rich . so the first successful english colony in america was founded in jamestown , virginia in 1607 . i say `` successful '' because there were two previous attempts to colonize the region . they were both epic failures . the more famous of which was the colony of roanoke island set up by sir walter raleigh , which is famous because all the colonists disappeared leaving only the word `` croatoan '' on carved into a tree . jamestown was a project of the virginia company , which existed to make money for its investors , something it never did . the hope was that they would find gold in the chesapeake region like the spanish had in south america , so there were a disproportionate number of goldsmiths and jewelers there to fancy up that gold which of course did not exist . anyway , it turns out that jewelers dislike farming -- so much so , that captain john smith who soon took over control of the island once said that they would rather starve than farm . so in the first year , half of the colonists died . 400 replacements came , but , by 1610 , after a gruesome winter called `` the starving time , '' the number of colonists had dwindled to 65 . and eventually word got out that the new world ’ s 1 year survival rate was like 20 % and it became harder to find new colonists . but 1618 , a virginia company hit upon a recruiting strategy called the headright system which offered 50 acres of land for each person that a settler paid to bring over . and this enabled the creation of a number of large estates , which were mostly worked on and populated by indentured servants . indentured servants were n't quite slaves , but they were kind of temporary slaves . like they could be bought and sold and they had to do what their masters commanded . but after seven to ten years of that , if they were n't dead , they were paid their freedom dues which they hoped would allow them to buy farms of their own . sometimes that worked out , but often either the money was n't enough to buy a farm , or else they were too dead to collect it . even more ominously in 1619 , just 12 years after the founding of jamestown , the first shipment of african slaves arrived in virginia . so the colony probably would have continued to struggle along , if they had n't found something that people really loved : tobacco . tobacco had been grown in mexico since at least 1000 bce , but the europeans had never seen it and it proved to be kind of a `` thank you for the small pox ; here 's some lung cancer ” gift from the natives . interestingly king james hated smoking . he called it “ a custom loathsome to the eye and hateful to the nose '' but he loved him some tax revenue , and nothing sells like drugs . by 1624 virginia was producing more than 200,000 pounds of tobacco per year . by the 1680s , more than 30 million pounds per year . tobacco was so profitable the colonists created huge plantations with very little in the way of towns or infrastructure to hold the social order together , a strategy that always works out brilliantly . the industry also structured virginian society . first off , most of the people who came in the 17th century , three-quarters of them , were servants . so virginia became a microcosm of england : a small class of wealthy landowners sitting atop a mass of servants . that sounds kind of dirty but it was mostly just sad . the society was also overwhelmingly male , because male servants were more useful in the tobacco fields , they were the greatest proportion of immigrants . in fact they outnumbered women 5 to 1 . the women who did come over were mostly indentured servants , and if they were to marry , which they often did because they were in great demand , they had to wait until their term of service was up . this meant delayed marriage which meant fewer children which further reduced the number of females . life was pretty tough for these women , but on the upside virginia was kind of a swamp of pestilence , so their husbands often died , and that created a small class of widows or even unmarried women who , because of their special status , could make contracts and own property , so that was good , sort of . ok. a quick word about maryland . maryland was the second chesapeake colony , founded in 1632 , and by now there was no messing around with joint stock companies . maryland was a proprietorship : a massive land grant to a single individual named cecilius calvert . calvert wanted to turn maryland into like a medieval feudal kingdom to benefit himself and his family , and he was no fan of the representational institutions that were developing in virginia . also calvert was catholic , and catholics were welcome in maryland which was n't always the case elsewhere . speaking of which , let 's talk about massachusetts . so jamestown might have been the first english colony , but massachusetts bay is probably better known . this is largely because the colonists who came there were so recognizable for their beliefs and also for their hats . that ’ s right . i ’ m talking about the pilgrims and the puritans . and no , i will not be talking about thanksgiving ... is a lie . i can ’ t help myself . but only to clear up the difference between pilgrims and puritans and also to talk about squanto . god i love me some squanto . let 's go to the thought bubble . most of the english men and women who settled in new england were uber-protestant puritans who believed the protestant church of england was still too catholic-y with its kneeling and incense and extravagantly-hatted archbishops . the particular puritans who , by the way did not call themselves that -- other people did , who settled in new england were called congregationalists because they thought congregations should determine leadership and worship structures , not bishops . the pilgrims were even more extreme . they wanted to separate more or less completely from the church of england . so first they fled to the netherlands , but the dutch were apparently too corrupt for them , so they rounded up investors and financed a new colony in 1620 . they were supposed to land in virginia , but in what perhaps should have been taken as an omen , they were blown wildly off course and ended up in what 's now massachusetts , founding a colony called plymouth . while still on board their ship the mayflower , 41 of the 150 or so colonists wrote and signed an agreement called the mayflower compact , in which they all bound themselves to follow `` just and equal laws '' that their chosen representatives would write-up . since this was the first written framework for government in the us , it 's kind of a big deal . but anyway , the pilgrims had the excellent fortune of landing in massachusetts with 6 weeks before winter , and they had the good sense not to bring very much food with them or any farm animals . half of them died before winter was out . the only reason they did n't all die was that local indians led by squanto gave them food and saved them . a year later , grateful that they had survived mainly due to the help of an alliance with the local chief massasoit , and because the indians had taught them how to plant corn and where to catch fish , the pilgrims held a big feast : the first thanksgiving . thanks thought bubble ! and by the way , that feast was on the fourth thursday in november , not mid-october as is celebrated in some of these green areas we call not america . anyway squanto was a pretty amazing character and not only because he helped save the pilgrims . he found that almost all of his tribe , the patuxet had been wiped out by disease and eventually settled with the pilgrims on the site of his former village and then died ... of disease because it is always ruining everything . so the pilgrims struggled on until 1691 when their colony was subsumed by the larger and much more successful massachusetts bay colony . the massachusetts bay colony was chartered in 1629 by london merchants who , like the founders of the virginia company , hoped to make money . but unlike virginia , the board of directors relocated from england to america , which meant that in massachusetts they had a greater degree of autonomy and self-government than they did in virginia . social unity was also much more important in massachusetts than it was in virginia . the puritans ' religious mission meant that the common good was , at least at first , put above the needs or the rights of the individual . those different ideas in the north and south about the role of government would continue ... until now . oh god . it 's time for the mystery document ? the rules are simple . i read the mystery document which i have not seen before . if i get it right , then i do not get shocked with the shock pen , and if i get it wrong i do . all right . `` we must be knit together in this work as one man , we must entertain each other in brotherly affection , we must be willing to abridge ourselves of our superfluities ( su-per-fluities ? i do n't know ) , for the supply of others necessities , we must uphold a familiar commerce together in all meekness , gentleness , patience and liberality , ... for we must consider that we shall be as a city upon a hill , the eyes of all people are upon us ; so that if we shall deal falsely with our god in this work we have undertaken and so cause him to withdraw his present help from us , we shall be made a story and a byword through the world . '' alright , first thing i noticed : the author of this document is a terrible speller or possibly wrote this before english was standardized . also , a pretty religious individual . and the community in question seems to embrace something near socialism : abridging the superfluous for others ' necessities . also it says that the community should be like a city upon a hill , like a model for everybody . and because of that metaphor , i know exactly where it comes from : the sermon `` a model of christian charity '' by john winthrop . yes ! yes ! no punishment ! this is one of the most important sermons in american history . it shows us just how religious the puritans were , but it also shows us that their religious mission was n't really one of individualism but of collective effort . in other words , the needs of the many outweigh the needs of the few or the one . but this city on a hill metaphor is the basis for one kind of american exceptionalism : the idea that we are so special and so godly that we will be a model to other nations , at least as long , according to winthrop , as we act together . lest you think winthrop ’ s words were forgotten , they did become the centerpiece of ronald reagan ’ s 1989 farewell address . okay so new england towns were governed democratically , but that does n't mean that the puritans were big on equality or that everybody was able to participate in government because no . the only people who could vote or hold office were church members , and to be a full church member you had to be a “ visible saint '' , so really , power stayed in the hands of the church elite . the same went for equality . while it was better than in the chesapeake colonies or england , as equality went ... eh , pretty unequal . as john winthrop declared , `` some must be rich , and some poor . some high , an eminent in power , and dignity ; others mean and in subjection . '' or as historian eric foner put it `` inequality was considered an expression of god 's will and while some liberties applied to all inhabitants , there were separate lists of rights for freemen , women , children and servants . '' there was also slavery in massachusetts . the first slaves were recorded in the colony in 1640 . however , puritans really did foster equality in one sense . they wanted everyone to be able to read the bible . in fact , parents could be punished by the town councils for not properly instructing their children in making them literate . but when roger williams called for citizens to be able to practice any religion they chose , he was banished from the colonies . so was ann hutchinson who argued the church membership should be based on inner grace and not on outward manifestations like church attendance . williams went on to found rhode island , so that worked out fine for him , but hutchinson , who was doubly threatening to massachusetts because she was a woman preaching unorthodox ideas , was too radical and was further banished to westchester , new york where she and her family were killed by indians . finally , somebody who does n't die of disease or starvation . so americans like to think of their country as being founded by pioneers of religious freedom who were seeking liberty from the oppressive english . we 've already seen that 's only partly true . for one thing , puritan ideas of equality and representation were n't particularly equitable or representational . in truth , america was also founded by indigenous people and by spanish settlers , and the earliest english colonies were n't about religion ; they were about money . we 'll see this tension between american mythology and american history again next week and also every week . thanks for watching ; i ’ ll see you next time . crash course is produced and directed by stan muller , our script supervisor is meredith danko , the associate producer is danica johnson , the show is written by my high school history teacher , raoul meyer and myself , and our graphics team is thought bubble . if you have questions about today 's video or really about anything about american history , ask them in comments ; the entire crash course team and many history professionals are there to help you . thanks for watching crash course . please make sure you are subscribed and , as we say in my home town , `` do n't forget to be awesome . ''

and by the way , that feast was on the fourth thursday in november , not mid-october as is celebrated in some of these green areas we call not america . anyway squanto was a pretty amazing character and not only because he helped save the pilgrims . he found that almost all of his tribe , the patuxet had been wiped out by disease and eventually settled with the pilgrims on the site of his former village and then died ... of disease because it is always ruining everything .

who helped the pilgrims that landed in plymouth , massachusetts ?

translator : andrea mcdonough reviewer : jessica ruby mysteries of vernacular : bewilder , to confuse or puzzle completely . the root of the word bewilder can be traced back to the old english word wilde , which was used to refer to something that was in a natural state , uncultivated , or undomesticated . over time , the word wild was often linked to the old english word deor . deor , which was derived from an early indo-european root that meant breathe , was initially used to describe any untamed animal or beast . this eventually morphed into the modern word deer , meaning a ruminant of the family cervidae . the two old english words , when mashed together , became wilderness , meaning a tract of uncultivated land , primarily inhabited by undomesticated beasts . from the word wilderness , the word wilder was born . to wilder someone was to lead him astray or lure him into the woods . in the 1600 's , the prefix be , meaning thoroughly , was compounded with wilder as a way of tacking on a little extra punch . someone who was bewildered was thoroughly lost in the wild . from this winding background , bewilder eventually evolved into our current definition , to be completely confused .

the two old english words , when mashed together , became wilderness , meaning a tract of uncultivated land , primarily inhabited by undomesticated beasts . from the word wilderness , the word wilder was born . to wilder someone was to lead him astray or lure him into the woods . in the 1600 's , the prefix be , meaning thoroughly , was compounded with wilder as a way of tacking on a little extra punch .

what does it mean to wilder someone ?

when i was in fourth grade , my teacher said to us one day : `` there are as many even numbers as there are numbers . '' `` really ? `` , i thought . well , yeah , there are infinitely many of both , so i suppose there are the same number of them . but even numbers are only part of the whole numbers , all the odd numbers are left over , so there 's got to be more whole numbers than even numbers , right ? to see what my teacher was getting at , let 's first think about what it means for two sets to be the same size . what do i mean when i say i have the same number of fingers on my right hand as i do on left hand ? of course , i have five fingers on each , but it 's actually simpler than that . i do n't have to count , i only need to see that i can match them up , one to one . in fact , we think that some ancient people who spoke languages that did n't have words for numbers greater than three used this sort of magic . for instance , if you let your sheep out of a pen to graze , you can keep track of how many went out by setting aside a stone for each one , and putting those stones back one by one when the sheep return , so you know if any are missing without really counting . as another example of matching being more fundamental than counting , if i 'm speaking to a packed auditorium , where every seat is taken and no one is standing , i know that there are the same number of chairs as people in the audience , even though i do n't know how many there are of either . so , what we really mean when we say that two sets are the same size is that the elements in those sets can be matched up one by one in some way . my fourth grade teacher showed us the whole numbers laid out in a row , and below each we have its double . as you can see , the bottom row contains all the even numbers , and we have a one-to-one match . that is , there are as many even numbers as there are numbers . but what still bothers us is our distress over the fact that even numbers seem to be only part of the whole numbers . but does this convince you that i do n't have the same number of fingers on my right hand as i do on my left ? of course not . it does n't matter if you try to match the elements in some way and it does n't work , that does n't convince us of anything . if you can find one way in which the elements of two sets do match up , then we say those two sets have the same number of elements . can you make a list of all the fractions ? this might be hard , there are a lot of fractions ! and it 's not obvious what to put first , or how to be sure all of them are on the list . nevertheless , there is a very clever way that we can make a list of all the fractions . this was first done by georg cantor , in the late eighteen hundreds . first , we put all the fractions into a grid . they 're all there . for instance , you can find , say , 117/243 , in the 117th row and 223rd column . now we make a list out of this by starting at the upper left and sweeping back and forth diagonally , skipping over any fraction , like 2/2 , that represents the same number as one the we 've already picked . we get a list of all the fractions , which means we 've created a one-to-one match between the whole numbers and the fractions , despite the fact that we thought maybe there ought to be more fractions . ok , here 's where it gets really interesting . you may know that not all real numbers -- that is , not all the numbers on a number line -- are fractions . the square root of two and pi , for instance . any number like this is called irrational . not because it 's crazy , or anything , but because the fractions are ratios of whole numbers , and so are called rationals ; meaning the rest are non-rational , that is , irrational . irrationals are represented by infinite , non-repeating decimals . so , can we make a one-to-one match between the whole numbers and the set of all the decimals , both the rationals and the irrationals ? that is , can we make a list of all the decimal numbers ? candor showed that you ca n't . not merely that we do n't know how , but that it ca n't be done . look , suppose you claim you have made a list of all the decimals . i 'm going to show you that you did n't succeed , by producing a decimal that is not on your list . i 'll construct my decimal one place at a time . for the first decimal place of my number , i 'll look at the first decimal place of your first number . if it 's a one , i 'll make mine a two ; otherwise i 'll make mine a one . for the second place of my number , i 'll look at the second place of your second number . again , if yours is a one , i 'll make mine a two , and otherwise i 'll make mine a one . see how this is going ? the decimal i 've produced ca n't be on your list . why ? could it be , say , your 143rd number ? no , because the 143rd place of my decimal is different from the 143rd place of your 143rd number . i made it that way . your list is incomplete . it does n't contain my decimal number . and , no matter what list you give me , i can do the same thing , and produce a decimal that 's not on that list . so we 're faced with this astounding conclusion : the decimal numbers can not be put on a list . they represent a bigger infinity that the infinity of whole numbers . so , even though we 're familiar with only a few irrationals , like square root of two and pi , the infinity of irrationals is actually greater than the infinity of fractions . someone once said that the rationals -- the fractions -- are like the stars in the night sky . the irrationals are like the blackness . cantor also showed that , for any infinite set , forming a new set made of all the subsets of the original set represents a bigger infinity than that original set . this means that , once you have one infinity , you can always make a bigger one by making the set of all subsets of that first set . and then an even bigger one by making the set of all the subsets of that one . and so on . and so , there are an infinite number of infinities of different sizes . if these ideas make you uncomfortable , you are not alone . some of the greatest mathematicians of cantor 's day were very upset with this stuff . they tried to make this different infinities irrelevant , to make mathematics work without them somehow . cantor was even vilified personally , and it got so bad for him that he suffered severe depression , and spent the last half of his life in and out of mental institutions . but eventually , his ideas won out . today , they 're considered fundamental and magnificent . all research mathematicians accept these ideas , every college math major learns them , and i 've explained them to you in a few minutes . some day , perhaps , they 'll be common knowledge . there 's more . we just pointed out that the set of decimal numbers -- that is , the real numbers -- is a bigger infinity than the set of whole numbers . candor wondered whether there are infinities of different sizes between these two infinities . he did n't believe there were , but could n't prove it . candor 's conjecture became known as the continuum hypothesis . in 1900 , the great mathematician david hilbert listed the continuum hypothesis as the most important unsolved problem in mathematics . the 20th century saw a resolution of this problem , but in a completely unexpected , paradigm-shattering way . in the 1920s , kurt gödel showed that you can never prove that the continuum hypothesis is false . then , in the 1960s , paul j. cohen showed that you can never prove that the continuum hypothesis is true . taken together , these results mean that there are unanswerable questions in mathematics . a very stunning conclusion . mathematics is rightly considered the pinnacle of human reasoning , but we now know that even mathematics has its limitations . still , mathematics has some truly amazing things for us to think about .

well , yeah , there are infinitely many of both , so i suppose there are the same number of them . but even numbers are only part of the whole numbers , all the odd numbers are left over , so there 's got to be more whole numbers than even numbers , right ? to see what my teacher was getting at , let 's first think about what it means for two sets to be the same size .

in the lesson we showed how to match the set of positive whole numbers to the set of positive even numbers . show how to match the set of positive whole numbers to the set of all even numbers ( positive , negative and zero ) .

imagine you 're asked to invent something new . it could be whatever you want made from anything you choose in any shape or size . that kind of creative freedom sounds so liberating , does n't it ? or does it ? if you 're like most people , you 'd probably be paralyzed by this task . without more guidance , where would you even begin ? as it turns out , boundless freedom is n't always helpful . in reality , any project is restricted by many factors , such as the cost , what materials you have at your disposal , and unbreakable laws of physics . these factors are called creative constraints , and they 're the requirements and limitations we have to address in order to accomplish a goal . creative constraints apply across professions , to architects and artists , writers , engineers , and scientists . in many fields , constraints play a special role as drivers of discovery and invention . during the scientific process in particular , constraints are an essential part of experimental design . for instance , a scientist studying a new virus would consider , `` how can i use the tools and techniques at hand to create an experiment that tells me how this virus infects the body 's cells ? and what are the limits of my knowledge that prevent me from understanding this new viral pathway ? '' in engineering , constraints have us apply our scientific discoveries to invent something new and useful . take , for example , the landers viking 1 and 2 , which relied on thrusters to arrive safely on the surface of mars . the problem ? those thrusters left foreign chemicals on the ground , contaminating soil samples . so a new constraint was introduced . how can we land a probe on mars without introducing chemicals from earth ? the next pathfinder mission used an airbag system to allow the rover to bounce and roll to a halt without burning contaminating fuel . years later , we wanted to send a much larger rover : curiosity . however , it was too large for the airbag design , so another constraint was defined . how can we land a large rover while still keeping rocket fuel away from the martian soil ? in response , engineers had a wild idea . they designed a skycrane . similar to the claw machine at toy stores , it would lower the rover from high above the surface . with each invention , the engineers demonstrated an essential habit of scientific thinking - that solutions must recognize the limitations of current technology in order to advance it . sometimes this progress is iterative , as in , `` how can i make a better parachute to land my rover ? '' and sometimes , it 's innovative , like how to reach our goal when the best possible parachute is n't going to work . in both cases , the constraints guide decision-making to ensure we reach each objective . here 's another mars problem yet to be solved . say we want to send astronauts who will need water . they 'd rely on a filtration system that keeps the water very clean and enables 100 % recovery . those are some pretty tough constraints , and we may not have the technology for it now . but in the process of trying to meet these objectives , we might discover other applications of any inventions that result . building an innovative water filtration system could provide a solution for farmers working in drought-stricken regions , or a way to clean municipal water in polluted cities . in fact , many scientific advances have occurred when serendipitous failures in one field address the constraints of another . when scientist alexander fleming mistakenly contaminated a petri dish in the lab , it led to the discovery of the first antibiotic , penicillin . the same is true of synthetic dye , plastic , and gunpowder . all were created mistakenly , but went on to address the constraints of other problems . understanding constraints guides scientific progress , and what 's true in science is also true in many other fields . constraints are n't the boundaries of creativity , but the foundation of it .

the next pathfinder mission used an airbag system to allow the rover to bounce and roll to a halt without burning contaminating fuel . years later , we wanted to send a much larger rover : curiosity . however , it was too large for the airbag design , so another constraint was defined .

what was the device used to lower the curiosity rover ?

hey , congratulations ! you 've just won the lottery , only the prize is n't cash or a luxury cruise . it 's a position in your country 's national legislature . and you are n't the only lucky winner . all of your fellow lawmakers were chosen in the same way . this might strike you as a strange way to run a government , let alone a democracy . elections are the epitome of democracy , right ? well , the ancient athenians who coined the word had another view . in fact , elections only played a small role in athenian democracy , with most offices filled by random lottery from a pool of citizen volunteers . unlike the representative democracies common today , where voters elect leaders to make laws and decisions on their behalf , 5th century bc athens was a direct democracy that encouraged wide participation through the principle of ho boulomenos , or anyone who wishes . this meant that any of its approximately 30,000 eligible citizens could attend the ecclesia , a general assembly meeting several times a month . in principle , any of the 6,000 or so who showed up at each session had the right to address their fellow citizens , propose a law , or bring a public lawsuit . of course , a crowd of 6,000 people trying to speak at the same time would not have made for effective government . so the athenian system also relied on a 500 member governing council called the boule , to set the agenda and evaluate proposals , in addition to hundreds of jurors and magistrates to handle legal matters . rather than being elected or appointed , the people in these positions were chosen by lot . this process of randomized selection is know as sortition . the only positions filled by elections were those recognized as requiring expertise , such as generals . but these were considered aristocratic , meaning rule by the best , as opposed to democracies , rule by the many . how did this system come to be ? well , democracy arose in athens after long periods of social and political tension marked by conflict among nobles . powers once restricted to elites , such as speaking in the assembly and having their votes counted , were expanded to ordinary citizens . and the ability of ordinary citizens to perform these tasks adequately became a central feature of the democratice ideology of athens . rather than a privilege , civic participation was the duty of all citizens , with sortition and strict term limits preventing governing classes or political parties from forming . by 21st century standards , athenian rule by the many excluded an awful lot of people . women , slaves and foreigners were denied full citizenship , and when we filter out those too young to serve , the pool of eligible athenians drops to only 10-20 % of the overall population . some ancient philosophers , including plato , disparaged this form of democracy as being anarchic and run by fools . but today the word has such positive associations , that vastly different regimes claim to embody it . at the same time , some share plato 's skepticism about the wisdom of crowds . many modern democracies reconcile this conflict by having citizens elect those they consider qualified to legislate on their behalf . but this poses its own problems , including the influence of wealth , and the emergence of professional politicians with different interests than their constituents . could reviving election by lottery lead to more effective government through a more diverse and representative group of legislatures ? or does modern political office , like athenian military command , require specialized knowledge and skills ? you probably should n't hold your breath to win a spot in your country 's government . but depending on where you live , you may still be selected to participate in a jury , a citizens ' assembly , or a deliberative poll , all examples of how the democratic principle behind sortition still survives today .

could reviving election by lottery lead to more effective government through a more diverse and representative group of legislatures ? or does modern political office , like athenian military command , require specialized knowledge and skills ? you probably should n't hold your breath to win a spot in your country 's government .

are there any features of athenian political practice that disturb you ? why ?

it may sound like a paradox , or some cruel joke , but whatever it is , it 's true . beethoven , the composer of some of the most celebrated music in history , spent most of his career going deaf . so how was he still able to create such intricate and moving compositions ? the answer lies in the patterns hidden beneath the beautiful sounds . let 's take a look at the famous `` moonlight sonata , '' which opens with a slow , steady stream of notes grouped into triplets : one-and-a-two-and-a-three-and-a . but though they sound deceptively simple , each triplet contains an elegant melodic structure , revealing the fascinating relationship between music and math . beethoven once said , `` i always have a picture in my mind when composing and follow its lines . '' similarly , we can picture a standard piano octave consisting of thirteen keys , each separated by a half step . a standard major or minor scale uses eight of these keys , with five whole step intervals and two half step ones . and the first half of measure 50 , for example , consists of three notes in d major , separated by intervals called thirds , that skip over the next note in the scale . by stacking the scale 's first , third and fifth notes , d , f-sharp and a , we get a harmonic pattern known as a triad . but these are n't just arbitrary magic numbers . rather , they represent the mathematical relationship between the pitch frequencies of different notes which form a geometric series . if we begin with the note a3 at 220 hertz , the series can be expressed with this equation , where `` n '' corresponds to successive notes on the keyboard . the d major triplet from the moonlight sonata uses `` n '' values five , nine , and twelve . and by plugging these into the function , we can graph the sine wave for each note , allowing us to see the patterns that beethoven could not hear . when all three of the sine waves are graphed , they intersect at their starting point of 0,0 and again at 0,0.042 . within this span , the d goes through two full cycles , f-sharp through two and a half , and a goes through three . this pattern is known as consonance , which sounds naturally pleasant to our ears . but perhaps equally captivating is beethoven 's use of dissonance . take a look at measures 52 through 54 , which feature triplets containing the notes b and c. as their sine graphs show , the waves are largely out of sync , matching up rarely , if at all . and it is by contrasting this dissonance with the consonance of the d major triad in the preceding measures that beethoven adds the unquantifiable elements of emotion and creativity to the certainty of mathematics , creating what hector berlioz described as `` one of those poems that human language does not know how to qualify . '' so although we can investigate the underlying mathematical patterns of musical pieces , it is yet to be discovered why certain sequences of these patterns strike the hearts of listeners in certain ways . and beethoven 's true genius lay not only in his ability to see the patterns without hearing the music , but to feel their effect . as james sylvester wrote , `` may not music be described as the mathematics of the sense , mathematics as music of the reason ? '' the musician feels mathematics . the mathematician thinks music . music , the dream . mathematics , the working life .

but perhaps equally captivating is beethoven 's use of dissonance . take a look at measures 52 through 54 , which feature triplets containing the notes b and c. as their sine graphs show , the waves are largely out of sync , matching up rarely , if at all . and it is by contrasting this dissonance with the consonance of the d major triad in the preceding measures that beethoven adds the unquantifiable elements of emotion and creativity to the certainty of mathematics , creating what hector berlioz described as `` one of those poems that human language does not know how to qualify . ''

the notes c , e , g form a c major chord . their frequencies are : c ≈ 261.6 hz e ≈ 329.6 hz g ≈ 392.0 hz what is the approximate ratio of c : e : g ?

translator : andrea mcdonough reviewer : bedirhan cinar you look down and see a yellow pencil lying on your desk . your eyes , and then your brain , are collecting all sorts of information about the pencil : its size , color , shape , distance , and more . but , how exactly does this happen ? the ancient greeks were the first to think more or less scientifically about what light is and how vision works . some greek philosophers , including plato and pythagoras , thought that light originated in our eyes and that vision happened when little , invisible probes were sent to gather information about far-away objects . it took over a thousand years before the arab scientist , alhazen , figured out that the old , greek theory of light could n't be right . in alhazen 's picture , your eyes do n't send out invisible , intelligence-gathering probes , they simply collect the light that falls into them . alhazen 's theory accounts for a fact that the greek 's could n't easily explain : why it gets dark sometimes . the idea is that very few objects actually emit their own light . the special , light-emitting objects , like the sun or a lightbulb , are known as sources of light . most of the things we see , like that pencil on your desk , are simply reflecting light from a source rather than producing their own . so , when you look at your pencil , the light that hits your eye actually originated at the sun and has traveled millions of miles across empty space before bouncing off the pencil and into your eye , which is pretty cool when you think about it . but , what exactly is the stuff that is emitted from the sun and how do we see it ? is it a particle , like atoms , or is it a wave , like ripples on the surface of a pond ? scientists in the modern era would spend a couple of hundred years figuring out the answer to this question . isaac newton was one of the earliest . newton believed that light is made up of tiny , atom-like particles , which he called corpuscles . using this assumption , he was able to explain some properties of light . for example , refraction , which is how a beam of light appears to bend as it passes from air into water . but , in science , even geniuses sometimes get things wrong . in the 19th century , long after newton died , scientists did a series of experiments that clearly showed that light ca n't be made up of tiny , atom-like particles . for one thing , two beams of light that cross paths do n't interact with each other at all . if light were made of tiny , solid balls , then you would expect that some of the particles from beam a would crash into some of the particles from beam b . if that happened , the two particles involved in the collision would bounce off in random directions . but , that does n't happen . the beams of light pass right through each other as you can check for yourself with two laser pointers and some chalk dust . for another thing , light makes interference patterns . interference patterns are the complicated undulations that happen when two wave patterns occupy the same space . they can be seen when two objects disturb the surface of a still pond , and also when two point-like sources of light are placed near each other . only waves make interference patterns , particles do n't . and , as a bonus , understanding that light acts like a wave leads naturally to an explanation of what color is and why that pencil looks yellow . so , it 's settled then , light is a wave , right ? not so fast ! in the 20th century , scientists did experiments that appear to show light acting like a particle . for instance , when you shine light on a metal , the light transfers its energy to the atoms in the metal in discrete packets called quanta . but , we ca n't just forget about properties like interference , either . so these quanta of light are n't at all like the tiny , hard spheres newton imagined . this result , that light sometimes behaves like a particle and sometimes behaves like a wave , led to a revolutionary new physics theory called quantum mechanics . so , after all that , let 's go back to the question , `` what is light ? '' well , light is n't really like anything we 're used to dealing with in our everyday lives . sometimes it behaves like a particle and other times it behaves like a wave , but it is n't exactly like either .

well , light is n't really like anything we 're used to dealing with in our everyday lives . sometimes it behaves like a particle and other times it behaves like a wave , but it is n't exactly like either .

explain why light is both a wave and a particle . give one example why is behaves like a wave and then why it behaves like a particle .

translator : andrea mcdonough reviewer : bedirhan cinar this might seem like a far-away place in a far-away land . my house is right there in the middle . this was 1992 l.a . riots . and i remember being 8 years old and looking out there and thinking to myself , `` this is it , this is game over . i 'm done . '' the military came in , the cops came in , and i thought they were going to save us , and for some reason they kept on pointing the guns at my people . so i grew up angry , i grew up mad . i struggled watching my parents pay rent at the end of the month . sometimes they had to take food out of their mouths so that we , my two younger sisters and i , could eat . and the people that i saw taking care of their family and taking care of business were the gang members . so i considered that as a career path , not because they were the ones that , you know , had the girls , had the cars , it was because they were the ones who took care of their families . and i love my family enough to even to consider that as a possibility . but it was n't always bad . if you have n't put two and two together , i 'm a dodgers fan . i like the dodgers even more so because dodgers stadium sits in the middle of the elysian park , one of the biggest parks in l.a. , and i remember going out on the weekends with my family and for la carne asada and sharing our cultura and them taking me on trails and showing me all this amazing stuff that they knew . i grew up , i went to dorsey high school . you might not know dorsey that much , but you might know crenshaw high school . crenshaw and dorsey are rival high schools , but they are more than just rivals in the traditional sense of rival high schools , they are the birth place of the bloods and the crips . so i was in 9th grade detention , and they gave me an ultimatum : they said , `` either you stay in detention , or you go to this thing called eco club . '' and i said , `` what ? ! ? eco club ? forget you ! '' but i took a chance and i went over to eco club . and the first thing that they said was , `` grab a bag of seeds and let 's go out . '' and i picked jalapeños because i wanted to grill salsa for my mom at the end of that . and they tricked me ! then all of a sudden , i started worrying about photosynthesis and the ph balance , and the uv radiation , and all this different stuff that would make my jalapeños grow . at the end of that semester , they gave me an opportunity to go to the teton science schools in wyoming . for a kid who has never been out of south central , to see mountains for the first time , to look up at the night sky and count , i could n't even count , the stars . for the first time in my life at the age of 15 i saw more stars than i could count . i had to pinch myself and look at that shooting star and say , `` no , that 's not the ghetto bird coming up at me . '' and the ghetto bird , you wo n't find in the audobon book , it 's a police helicopter in case you do n't know . and i went back home and i found mentors and friends and family and people who supported me in this , and in 2005 , this guy named richard louv wrote a book called < i > last child in the woods < /i > , and he coined a phrase called `` nature-deficit disorder '' . it 's not a medical term , do n't worry , you do n't have to take drugs for it , it 's an easy fix : all you have to do is get outside . because we have 7 billion people in the world today , but if you were to put all those 7 billion people shoulder-to-shoulder with each other , they could all fit in the city of l.a . it 's not necessarily that we are running out of space , it 's how we are using that space up . the average u.s. teenager now spends somewhere between 40 and 65 hours a week connected to some type of media device , some kind of technology . that 's a full-time job ! we 're not saying that its bad , we 're just saying get out , have fun ! and i got together with some friends and we created this thing called the `` natural leaders network '' . and we wanted to find out how other people are getting outside all over the world . we thought it was just us here in the u.s. , but no , no , it 's all over the world . and we started getting amazing things back : the beaches , the mountains , in the middle of the city , how people got out , just the pure joy of celebrating our connection with nature . and it all started with that one group . i want to give you this new motivation about a new nature movement , and 7 reasons for a new nature movement . you can create your own reasons , but these are 7 reasons that we 're talking about . i 'm going to speed up a little bit because of time . but , take it from these kids , let 's go get outside ! last year i got to climb the grand teton . i went from being that kid from south central realizing that somehow i was connected to those mountains , that my community in south central l.a. was connected to the mountains up there . and it all made sense , the world made sense to me . science , and math , and history , and english , and all the different things that were happening in this world made sense to me because of that . i went out to be the first one to graduate from my family in high school . i 'm the first one . i 'm a national geographic explorer today . i do these amazing talks , and i 'm not telling you these things so i can brag about it , or that i can show off , i 'm telling you these things because if a kid from south central who was about to be a gang member can grow up to be a national geographic explorer and sit here in front of you and address you like i am today , then do n't ever , ever in your life doubt what you can do . at the end of the day , i do what i do because of my family . my family means the world to me and from this day forward , each one of you in this room is part of that family . i want you go to away with that and i 'll leave it with this one quote , which has driven me to this point : `` once social change begins , it can not be reversed . you can not uneducate the person who has learned to read . you can not humiliate the person who feels pride . you can not oppress the people who are not afraid anymore . we have seen the future , and the future is ours . '' it 's your future , it 's our future , so go get 'em !

and the ghetto bird , you wo n't find in the audobon book , it 's a police helicopter in case you do n't know . and i went back home and i found mentors and friends and family and people who supported me in this , and in 2005 , this guy named richard louv wrote a book called < i > last child in the woods < /i > , and he coined a phrase called `` nature-deficit disorder '' . it 's not a medical term , do n't worry , you do n't have to take drugs for it , it 's an easy fix : all you have to do is get outside .

what phrase did richard louv coin in his book , last child in the woods ?

some superheroes can grow to the size of a building at will . that 's very intimidating ! but a scientist must ask where the extra material is coming from . the law of conservation of mass implies that mass can neither be created nor destroyed , which means that our hero 's mass will not change just because his size changes . for instance , when we bake a fluffy sponge cake , even though the resulting delicious treat is much bigger in size than the cake batter that went into the oven , the weight of the cake batter should still equal the weight of the cake plus the moisture that has evaporated . in a chemical equation , molecules rearrange to make new compounds , but all the components should still be accounted for . when our hero expands from 6 feet tall to 18 feet tall , his height triples . galileo 's square cube law says his weight will be 27 - 3 times 3 times 3 equals 27 - times his regular weight since he has to expand in all three dimensions . so , when our superhero transforms into a giant , we are dealing with two possibilities . our hero towering at 18 feet still only weighs 200 pounds , the original weight in this human form . now , option two , our hero weighs 5,400 pounds - 200 pounds times 27 equals 5,400 pounds - when he is 18 feet tall , which means he also weighs 5,400 pounds when he is 6 feet tall . nobody can get in the same elevator with him without the alarm going off . now , option two seems a little more scientifically plausible , but it begs the question , how does he ever walk through the park without sinking into the ground since the pressure he is exerting on the soil is calculated by his mass divided by the area of the bottom of his feet ? and what kind of super socks and super shoes is he putting on his feet to withstand all the friction that results from dragging his 5,400 pound body against the road when he runs ? and can he even run ? and i wo n't even ask how he finds pants flexible enough to withstand the expansion . now , let 's explore the density of the two options mentioned above . density is defined as mass divided by volume . the human body is made out of bones and flesh , which has a relatively set density . in option one , if the hero weighs 200 pounds all the time , then he would be bones and flesh at normal size . when he expands to a bigger size while still weighing 200 pounds , he essentially turns himself into a giant , fluffy teddy bear . in option two , if the hero weighs 5,400 pounds all the time , then he would be bones and flesh at 18 feet with 5,400 pounds of weight supported by two legs . the weight would be exerted on the leg bones at different angles as he moves . bones , while hard , are not malleable , meaning they do not bend , so they break easily . the tendons would also be at risk of tearing . tall buildings stay standing because they have steel frames and do not run and jump around in the jungle . our hero , on the other hand , one landing at a bad angle and he 's down . assuming his bodily function is the same as any mammal 's , his heart would need to pump a large amount of blood throughout his body to provide enough oxygen for him to move 5,400 pounds of body weight around . this would take tremendous energy , which he would need to provide by consuming 27 times 3,000 calories of food every day . now , that is roughly 150 big macs . 27 times 3,000 calculated equals 81,000 calculated slash 550 calories equals 147 . he would n't have time to fight crime because he would be eating all the time and working a 9-to-5 job in order to afford all the food he eats . and what about superheroes who can turn their bodies into rocks or sand ? well , everything on earth is made out of elements . and what defines each element is the number of protons in the nucleus . that is how our periodic table is organized . hydrogen has one proton , helium , two protons , lithium , three protons , and so on . the primary component of the most common form of sand is silicon dioxide . meanwhile , the human body consists of 65 % oxygen , 18 % carbon , 10 % hydrogen , and 7 % of various other elements including 0.002 % of silicon . in a chemical reaction , the elements recombine to make new compounds . so , where is he getting all this silicon necessary to make the sand ? sure , we can alter elements by nuclear fusion or nuclear fission . however , nuclear fusion requires so much heat , the only natural occurrence of this process is in stars . in order to utilize fusion in a short amount of time , the temperature of the area needs to be hotter than the sun . every innocent bystander will be burned to a crisp . rapid nuclear fission is not any better since it often results in many radioactive particles . our hero would become a walking , talking nuclear power plant , ultimately harming every person he tries to save . and do you really want the heat of the sun or a radioactive nuclear plant inside of your body ? now , which superpower physics lesson will you explore next ? shifting body size and content , super speed , flight , super strength , immortality , and invisibility .

and what defines each element is the number of protons in the nucleus . that is how our periodic table is organized . hydrogen has one proton , helium , two protons , lithium , three protons , and so on .

the periodic table is organized by the number of

yeah . hey it 's me destin , welcome back to smarter every day . so i 've seen enough videos on the internet of a mantis shrimp punching to have a good idea of what 's going on , but i do n't understand it , like at the mechanical level . so today on smarter every day my sister has volunteered to model three seemingly unrelated objects to help us understand this a little bit better . but first , let 's go to james cook university and watch one punch in slow motion . ok where are we going ? -we 're gon na we 're gon na go to a place called yorkeys knob . - shut up ! - that 's the name of it . - to get some crabs . - we 're not ! - from yorkeys knob . ( destin ) [ laughs ] i was hoping i could use that.. but ... i ca n't . - it 's true , the place is called yorkeys knob . ( destin ) you were n't lying . so yorkeys knob , now i have to find crabs . - that one . that 's a good one . grab that one . got him ? -got him . - there you go . crabs in test tubes . ( destin ) i have to say , i 've never seen that before . - it works . it 'll be cool . so what we 'll do is we 'll take one of the test tubes with the crab in it , we 'll put the test tube down here which will keep the crab there . he 'll come out and go.. bang.. hit the crab and smash the test tube . ( destin ) really ? so the mantis shrimp is.. it 's a peacock mantis shrimp . - yep . - look at that joker . it 's pretty awesome . hey do n't they see more colors than any other animal ? - yeah . they 've got incredible vision and their eyes are setup in parts of three . so the top bits look in a different part from the middle , which look at a different part from the bottom . - kind of like the fovea on our eyes is different from.. - yeah . - ok. - out we come . move little crab . [ loud click ] - bang ! - it triggered . - pull him out . [ bang ] [ breaking glass ] ( destin ) yeah , that 's crazy . so let 's back it up and watch again and you 'll notice that there 's a cavitation bubble generated at the exact point of impact . ok first of all , a mantis shrimp is n't even a shrimp . it 's actually a stomatopod . we call it a shrimp because it kinda looks like it , but we also call it a mantis because it 's similar to a preying mantis with its forearms . they have similar hunting strategies . dr seymour says that punch is so fast that it ca n't be accomplished by muscle movement alone , there has to be something else going on , which brings up sheila patek . believe it or not , dr patek has determined that the shape of this potato chip is the secret to the punch of the mantis shrimp . seriously . this shape is called a hyperbolic paraboloid , and if you 've ever taken calculus you 've seen it . it 's basically a saddle shape and they 're super strong . this saddle is located on top of the smasher , and the stomatopod uses his muscles to compress it like a spring and he holds it back with a latch mechanism . he then releases this potential energy and it drives the club forward at a much higher velocity than would be possible with muscle alone . so the next time you eat one of these remember there 's another animal eating with the same shape you are , only he 's doing it at the bottom of the ocean and he 's got that shape integrated into the top of his arm . if you 've ever played with a vice clamp before , you 've seen this type of mechanism . you can slowly clamp down on the tool , which uses a cam-over action to lock it in place , and if you have it set right and squeeze it hard , you store mechanical strain energy . when you trip the latch the energy 's released and the arm flies forward real fast , but think about this . mantis shrimp use their little clubber to break open shells that are really hard right ? so why does the shell break and the club does n't ? let 's watch another clip . this is dr seymour feeding a crab to the stomatopod except this time there 's no test tube . - it 's flicking the.. it 's flicking the rock . ohhhh ! - did you get it ? - dunno , might have . - ohhhh i feel for that crab . [ laughs ] [ bang ] ( destin ) watch again closer and see if you can see the saddle release the energy . - look at that . - good grief . snapped it straight in half . we 're talking about serious forces here . in engineering we take two materials and we combine them together into composites to make them stronger . for example plywood is made of many layers of wood with the fibers oriented in two different directions . mantis shrimps however take this to the next level with an organic polymer called chitin . at the wyss institute for biologically inspired engineering at harvard , they determined that these fibers are n't rotated only in two principle directions like plywood , it 's an entire helix , which gives the structure strength in many different directions . these strands are then bonded together in a mineralized matrix which makes the whole thing an incredibly strong smasher . but it gets crazier than that . the team put a section of the smasher in a synchrotron so they could analyze the material makeup . a synchrotron ! that 's like a particle accelerator . this is crazy science . they bombarded it hundreds of times to understand the density and the local orientation of the crystals in the material , and guess what . they found that the crystals near the surface were oriented perpendicular to the impact site and that orientation changed as we move away from the impact site . basically the material changes composition and strength at different locations on the inside . the impact surface is incredibly hard , but the internal structure transitions smoothly to allow the distribution of a huge impulse load throughout the rest of that structure so it can punch stuff all day long without breaking . so instead of a normal composite like plywood , which are identical layers stacked up and glued together , a mantis shrimp club is a variable composite , meaning you can vary the material makeup and the strength orientation wherever you need it . this is an incredibly smart way to design a system . in summary , i want you to love the mantis shrimp . i do n't want you to love it just because of the mechanics of how it throws the punch . not because of the chemistry of the variable composition of the crystalline structure . the optics.. it can see circularly polarized light . this is an incredible , incredible animal , and i want you to think about it every time you eat a chip like this . can you do that for me ? ok i hope you enjoyed learning how mantis shrimp club . it 's all about the hyperbolic paraboloid , or as my cal 3 teacher taught me , hyperbowic pawabawoid . anyway , i 'm destin , you 're getting smarter every day . if you 're interested in supporting the crazy trips i do , please consider supporting on audible . audible.com/smarter . you can get any audiobook you want . ( i apologize if you 're deaf ... it makes no sense for you to support via audible . ) i listened to 20,000 leagues under the sea when i did this series because i wanted to learn more about marine life . jules verne nailed it . 20,000 leagues under the sea , audible.com/smarter . thank you so much for your support . i 'll leave a link in the video description . i 'm destin , you 're getting smarter every day , have a good one . it 's derek ! he video bombed me . [ laugh ] ( destin ) ho ! - [ laughs ] we could bring the lighting down on the chip please . perfect . [ laughs ] that was really dumb . ( destin ) which is why i think i 'm gon na use it .

( destin ) really ? so the mantis shrimp is.. it 's a peacock mantis shrimp . - yep .

how does the hyperbolic parabaloid , located on the top of the mantis shrimp 's arm , help create its strong punches ?

dear mr. president , do you know much about physics ? i mean , you 're the president of the united states : a country with five thousand nuclear weapons , birthplace of the world 's computing and telecommunications industry , home of the first atomic clock and creator of the global positioning system . but chances are , if you just took regular american high school physics , you do n't know one iota about the science behind these things ( no offense ) . that 's because high school physics students across most of america are not required to learn about pretty much any physical phenomena discovered or explained more recently than 1865 . yes , 1865 . that 's the year the civil war ended and well over a decade before albert einstein was even born ! you know what can happen in 150 years , mr. president ? a lot . velcro , for one . but let me list some useful and important ideas of the last 150 years of physics that are n't a required part of most standard us high school physics courses : photons . the structure of atoms . the existence of antimatter . gps . lasers . transistors . diodes and leds . quarks . chaos theory . electron microscopy . mri scanning . the big bang . black holes . star formation . the fact that gravity bends light . the fact that the universe is expanding . the higgs boson and the weak and strong nuclear forces and all the rest of quantum mechanics and relativity and the topic of every single nobel prize in physics since… always . basically , most of the important stuff . i mean , mr. president , imagine if history classes did n't talk about the abolition of slavery , world wars i or ii , the great depression , the rise of the us as a global superpower , the cold war or the civil rights movement or heaven forbid the first african american president . or imagine if biology classes did n't talk about dna , or hormones , or cell reproduction or the modern germ theory of disease or ecology . or if geologists did n't talk about plate tectonics . and computer scientists… well… in 1865 a computer was a person who computed your taxes . now , if you were lucky enough to have an ambitious teacher or take advanced placement physics , then you might have learned about some of einstein 's discoveries of 1905 ! yes ! current events ! but learning about how einstein 's work helped set the stage for a century of amazing developments in our understanding of the universe is not a part of the standard curriculum . so why , mr. president , am i addressing this letter to you ? well , you appoint the secretary of education , for one - and i do believe that high school physics is somewhat related to education . now , maybe your education secretary says , `` ancient physics is already hard to teach to high schoolers . and you want us to teach them modern physics which is even harder ? ! students ca n't really appreciate the beauty of modern physics without fancy college level mathematics . '' rubbish . ever heard of carl sagan ? richard feynman ? or neil degrasse tyson ? these great men have been 100 % committed to the appreciation and dissemination of the awesomeness of the universe . and we should be too . how else are we supposed to foster and find our future brilliant innovators , inventors , and explorers ? how can we expect to educate our citizens for the next century if we do n't teach about the last ? and that 's not to say that we should ignore math , either - on the contrary , math is one of the most beautiful and awesome things in the universe , especially because it allows us to understand the universe . in particular , the last 150 years have borne fruit to perhaps the most drastic changes in our understanding of the universe , ever , and these new ways of thinking and solving problems should be the centerpiece of an education in physics . between you and me , mr. president , i think we 'd better start making physics education more awesome here in the us , otherwise the next carl sagan or richard feynman will come from somewhere with more educational foresight - maybe even , the internet . sincerely , a collection of atoms known as henry ps you 're probably super busy , but if you 'd like to hear about physics education across the atlantic , i highly recommend heading over to brady 's channel , sixty symbols , for a perspective from the uk . i bet you 'll enjoy it .

so why , mr. president , am i addressing this letter to you ? well , you appoint the secretary of education , for one - and i do believe that high school physics is somewhat related to education . now , maybe your education secretary says , `` ancient physics is already hard to teach to high schoolers .

excluding the `` correct '' answer in the last question , are any of the other three options mentioned valid reasons for `` post-1865 '' topics not to be included in high school physics curricula ? pick one of the other three options and explain why it is valid or why it is not . or , if you can think of your own reason , feel free to state it and explain it instead .

they 're everywhere , but you will never see one . trillions of them are flying through you right this second , but you ca n't feel them . these ghost particles are called neutrinos and if we can catch them , they can tell us about the furthest reaches and most extreme environments of the universe . neutrinos are elementary particles , meaning that they ca n't be subdivided into other particles the way atoms can . elementary particles are the smallest known building blocks of everything in the universe , and the neutrino is one of the smallest of the small . a million times less massive than an electron , neutrinos fly easily through matter , unaffected by magnetic fields . in fact , they hardly ever interact with anything . that means that they can travel through the universe in a straight line for millions , or even billions , of years , safely carrying information about where they came from . so where do they come from ? pretty much everywhere . they 're produced in your body from the radioactive decay of potassium . cosmic rays hitting atoms in the earth 's atmosphere create showers of them . they 're produced by nuclear reactions inside the sun and by radioactive decay inside the earth . and we can generate them in nuclear reactors and particle accelerators . but the highest energy neutrinos are born far out in space in environments that we know very little about . something out there , maybe supermassive black holes , or maybe some cosmic dynamo we 've yet to discover , accelerates cosmic rays to energies over a million times greater than anything human-built accelerators have achieved . these cosmic rays , most of which are protons , interact violently with the matter and radiation around them , producing high-energy neutrinos , which propagate out like cosmic breadcrumbs that can tell us about the locations and interiors of the universe 's most powerful cosmic engines . that is , if we can catch them . neutrinos ' limited interactions with other matter might make them great messengers , but it also makes them extremely hard to detect . one way to do so is to put a huge volume of pure transparent material in their path and wait for a neutrino to reveal itself by colliding with the nucleus of an atom . that 's what 's happening in antarctica at icecube , the world 's largest neutrino telescope . it 's set up within a cubic kilometer of ice that has been purified by the pressure of thousands of years of accumulated ice and snow , to the point where it 's one of the clearest solids on earth . and even though it 's shot through with boreholes holding over 5,000 detectors , most of the cosmic neutrinos racing through icecube will never leave a trace . but about ten times a year , a single high-energy neutrino collides with a molecule of ice , shooting off sparks of charged subatomic particles that travel faster through the ice than light does . in a similar way to how a jet that exceeds the speed of sound produces a sonic boom , these superluminal charged particles leave behind a cone of blue light , kind of a photonic boom . this light spreads through icecube , hitting some of its detectors located over a mile beneath the surface . photomultiplier tubes amplify the signal , which contains information about the charged particles ' paths and energies . the data are beamed to astrophysicists around the world who look at the patterns of light for clues about the neutrinos that produced them . these super energetic collisions are so rare that icecube 's scientists give each neutrino nicknames , like big bird and dr. strangepork . icecube has already observed the highest energy cosmic neutrinos ever seen . the neutrinos it detects should finally tell us where cosmic rays come from and how they reached such extreme energies . light , from infrared , to x-rays , to gamma rays , has given us increasingly energetic and continuously surprising views of the universe . we are now at the dawn of the age of neutrino astronomy , and we have no idea what revelations icecube and other neutrino telescopes may bring us about the universe 's most violent , most energetic phenomena .

these super energetic collisions are so rare that icecube 's scientists give each neutrino nicknames , like big bird and dr. strangepork . icecube has already observed the highest energy cosmic neutrinos ever seen . the neutrinos it detects should finally tell us where cosmic rays come from and how they reached such extreme energies . light , from infrared , to x-rays , to gamma rays , has given us increasingly energetic and continuously surprising views of the universe .

cosmic rays are thought to be produced in the same environments as cosmic neutrinos . why ca n't cosmic rays tell us about their origin ?

translator : andrea mcdonough reviewer : bedirhan cinar `` i need a hero ! '' so many people in distress have said this , but why ? what kind of hero do we need and do we even really even need a hero at all ? well , if you look at any piece of literature written for page , script , or stage , the answer is yes ! but , heroes come in all shapes and sizes , depending on what needs to be dealt with . first , you have your epic heroes . epic heroes usually come from a famous family , have super-human strength , are unusually good-looking . they take on challenges that no one else will and succeed . they have great journeys and adventures , some supernatural and some , right here on earth . beowulf does all of this . he travels across the sea with his band of warriors to help another king defeat a supernatural monster that has been terrorizing his kingdom . he defeats the monster and the monster 's mother in an epic battle , and then goes back home and becomes king himself . in his old age , he has one more monster to face , one more threat that he must keep from his people , a dragon . now , being an epic hero , of course he wins , but he is also human , and so he also dies . but he leaves behind stories to inspire others even today . next , we have our tragic heroes . tragic heroes are usually leaders or powerful characters , but the tragic hero is also majorly flawed and that flaw usually leads him down the path to a horrible and tragic death . take the story of oedipus the king , for example . one day , a young man travels to a town called thebes . on the way , he kills a man for not yielding to him on the road in the first documented case of road rage . he also defeats a magical creature and is rewarded by becoming the king of thebes , and thus , marrying their queen . well , that 's not so tragic , right ? wrong ! the queen he just married is actually his birth mother ! oedipus was supposed to have been killed as a child by a servant , but instead he was given to another family . oh , and the man he killed on the road , the previous king of thebes and his dad . so he killed his father and married his mother . now that is quite tragic . not tragic enough for you ? try this one . romeo montague is a guy born into a wealthy family and finds the love of his life at a party , juliet . but , juliet is from a different family that just so happens to hate his family . instead of being patient and working through the family feud , romeo decides he must have his love now , and his impatience leads to bloodshed and death , including his own and juliet 's . moving on to romantic heroes . now these guys might sound like they might have a better love life and chance at happiness , but that 's not always the case . these heroes are emotional and very human . but there is something magical about them . some have a miraculous birth and then are separated from their family . others use enchanted swords or get help from magical beans . they could also reject the expectations of society and adhere to their own code of morality . and in the end , the hero triumphs over evil in an idyllic way , but at great personal , emotional sacrifice . king arthur is a good example of a romantic hero . sure , he became king and married the love of his life , but he was also killed by his son , who was born out of wedlock , and had his wife cheat on him with his best friend . so , although he , too , like beowulf , was a great king , he suffered much more for the greater purpose of society , which makes him more human and relatable to us all . there are different heroes for different situations . sometimes we need the strong warrior to slay the evils of the world . at other times , we need a common person who becomes great so that they can inspire us all to be better . so do we need heroes ? absolutely ! no matter what the time or place , we still need something to believe in . they remind us of the good in each of us , and the need for hope and the importance of knowledge .

at other times , we need a common person who becomes great so that they can inspire us all to be better . so do we need heroes ? absolutely !

according to the end of the video , what is the reason that we need heroes ?

the area surrounding the north pole may seem like a frozen and desolate environment where nothing ever changes . but it is actually a complex and finely balanced natural system , and its extreme location makes it vulnerable to feedback processes that can magnify even tiny changes in the atmosphere . in fact , scientists often describe the arctic as the canary in the coal mine when it comes to predicting the impact of climate change . one major type of climate feedback involves reflectivity . white surfaces , like snow and ice , are very effective at reflecting the sun 's energy back into space , while darker land and water surfaces absorb much more incoming sunlight . when the arctic warms just a little , some of the snow and ice melts , exposing the ground and ocean underneath . the increased heat absorbed by these surfaces causes even more melting , and so on . and although the current situation in the arctic follows the warming pattern , the opposite is also possible . a small drop in temperatures would cause more freezing , increasing the amount of reflective snow and ice . this would result in less sunlight being absorbed , and lead to a cycle of cooling , as in previous ice ages . arctic sea ice is also responsible for another feedback mechanism through insulation . by forming a layer on the ocean 's surface , the ice acts as a buffer between the frigid arctic air and the relatively warmer water underneath . but when it thins , breaks , or melts in any spot , heat escapes from the ocean , warming the atmosphere and causing more ice to melt in turn . both of these are examples of positive feedback loops , not because they do something good , but because the initial change is amplified in the same direction . a negative feedback loop , on the other hand , is when the initial change leads to effects that work in the opposite direction . melting ice also causes a type of negative feedback by releasing moisture into the atmosphere . this increases the amount and thickness of clouds present , which can cool the atmosphere by blocking more sunlight . but this negative feedback loop is short-lived , due to the brief arctic summers . for the rest of the year , when sunlight is scarce , the increased moisture and clouds actually warm the surface by trapping the earth 's heat , turning the feedback loop positive for all but a couple of months . while negative feedback loops encourage stability by pushing a system towards equilibrium , positive feedback loops destabilize it by enabling larger and larger deviations . and the recently increased impact of positive feedbacks may have consequences far beyond the arctic . on a warming planet , these feedbacks ensure that the north pole warms at a faster rate than the equator . the reduced temperature differences between the two regions may lead to slower jet stream winds and less linear atmospheric circulation in the middle latitudes , where most of the world 's population lives . many scientists are concerned that shifts in weather patterns will last longer and be more extreme , with short term fluctuations becoming persistent cold snaps , heat waves , droughts and floods . so the arctic sensitivity does n't just serve as an early warning alarm for climate change for the rest of the planet . its feedback loops can affect us in much more direct and immediate ways . as climate scientists often warn , what happens in the arctic does n't always stay in the arctic .

its feedback loops can affect us in much more direct and immediate ways . as climate scientists often warn , what happens in the arctic does n't always stay in the arctic .

what physical characteristics of the arctic make climate feedbacks possible ?

in 1997 , a french woman named jeanne calment passed away after 122 years and 164 days on this earth , making her the oldest known person in history . her age was so astounding that a millionaire pledged $ 1 million to anyone who could break her record . but in reality , living to this age or beyond is a feat that very few , maybe even no humans , are likely to accomplish . human bodies just are n't built for extreme aging . our capacity is set at about 90 years . but what does aging really mean and how does it counteract the body 's efforts to stay alive ? we know intuitively what it means to age . for some , it means growing up , while for others , it 's growing old . yet finding a strict scientific definition of aging is a challenge . what we can say is that aging occurs when intrinsic processes and interactions with the environment , like sunlight , and toxins in the air , water , and our diets , cause changes in the structure and function of the body 's molecules and cells . those changes in turn drive their decline , and subsequently , the failure of the whole organism . the exact mechanisms of aging are poorly understood . but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role . firstly , as the years pass , our bodies accumulate genetic damage in the form of dna lesions . these occur naturally when the body 's dna replicates , but also in non-dividing cells . organelles called mitochondria are especially prone to this damage . mitochondria produce adenosine triphosphate , or atp , the main energy source for all cellular processes , plus mitochondria regulate many different cell activities and play an important role in programmed cell death . if mitochondrial function declines , then cells and , later on , whole organs , deteriorate , too . other changes are known to occur in the expression patterns of genes , also known as epigenetic alterations , that affect the body 's tissues and cells . genes silenced or expressed only at low levels in newborns become prominent in older people , leading to the development of degenerative diseases , like alzheimer 's , which accelerate aging . even if we could avoid all these harmful genetic alterations , not even our own cells could save us . the fact remains that cellular regeneration , the very stuff of life , declines as we age . the dna in our cells is packaged within chromosomes , each of which has two protective regions at the extremities called telomeres . those shorten every time cells replicate . when telomeres become too short , cells stop replicating and die , slowing the body 's ability to renew itself . with age , cells increasingly grow senescent , too , a process that halts the cell cycle in times of risk , like when cancer cells are proliferating . but the response also kicks in more as we age , halting cell growth and cutting short their ability to replicate . aging also involves stem cells that reside in many tissues and have the property of dividing without limits to replenish other cells . as we get older , stem cells decrease in number and tend to lose their regenerative potential , affecting tissue renewal and maintenance of our organs original functions . other changes revolve around cells ' ability to function properly . as they age , they stop being able to do quality control on proteins , causing the accumulation of damaged and potentially toxic nutrients , leading to excessive metabolic activity that could be fatal for them . intercellular communication also slows , ultimately undermining the body 's functional ability . there 's a lot we do n't yet understand about aging . ultimately , does longer life as we know it come down to diet , exercise , medicine , or something else ? will future technologies , like cell-repairing nanobots , or gene therapy , artificially extend our years ? and do we want to live longer than we already do ? starting with 122 years as inspiration , there 's no telling where our curiosity might take us .

but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role . firstly , as the years pass , our bodies accumulate genetic damage in the form of dna lesions . these occur naturally when the body 's dna replicates , but also in non-dividing cells .

dna lesions involved in aging :

where does all this stuff come from ? this rock ? that cow ? your heart ? not the things themselves , mind you , but what they 're made of : the atoms that are the fabric of all things . to answer that question , we look to the law of conservation of mass . this law says take an isolated system defined by a boundary that matter and energy can not cross . inside this system , mass , a.k.a . matter and energy , can neither be created nor destroyed . the universe , to the best of our knowledge , is an isolated system . but before we get to that , let 's look at a much smaller and simpler one . here we have six carbon atoms , 12 hydrogen atoms , and 18 oxygen atoms . with a little energy , our molecules can really get moving . these atoms can bond together to form familiar molecules . here 's water , and here 's carbon dioxide . we ca n't create or destroy mass . we 're stuck with what we 've got , so what can we do ? ah , they have a mind of their own . let 's see . they 've formed more carbon dioxide and water , six of each . add a little energy , and we can get them to reshuffle themselves to a simple sugar , and some oxygen gas . our atoms are all accounted for : 6 carbon , 12 hydrogen , and 18 oxygen . the energy we applied is now stored in the bonds between atoms . we can rerelease that energy by breaking that sugar back into water and carbon dioxide , and still , same atoms . let 's put a few of our atoms aside and try something a little more explosive . this here is methane , most commonly associated with cow flatulence , but also used for rocket fuel . if we add some oxygen and a little bit of energy , like you might get from a lit match , it combusts into carbon dioxide , water and even more energy . notice our methane started with four hydrogen , and at the end we still have four hydrogen captured in two water molecules . for a grand finale , here 's propane , another combustible gas . we add oxygen , light it up , and boom . more water and carbon dioxide . this time we get three co2s because the propane molecule started with three carbon atoms , and they have nowhere else to go . there are many other reactions we can model with this small set of atoms , and the law of conservation of mass always holds true . whatever matter and energy go into a chemical reaction are present and accounted for when it 's complete . so if mass ca n't be created or destroyed , where did these atoms come from in the first place ? let 's turn back the clock and see . further , further , further , too far . okay , there it is . the big bang . our hydrogen formed from a high-energy soup of particles in the three minutes that followed the birth of our universe . eventually , clusters of atoms accumulated and formed stars . within these stars , nuclear reactions fused light elements , such as hydrogen and helium , to form heavier elements , such as carbon and oxygen . at first glance , these reactions may look like they 're breaking the law because they release an astounding amount of energy , seemingly out of nowhere . however , thanks to einstein 's famous equation , we know that energy is equivalent to mass . it turns out that the total mass of the starting atoms is very slightly more than the mass of the products , and that loss of mass perfectly corresponds to the gain in energy , which radiates out from the star as light , heat and energetic particles . eventually , this star went supernova and scattered its elements across space . long story short , they found each other and atoms from other supernovas , formed the earth , and 4.6 billion years later got scooped up to play their parts in our little isolated system . but they 're not nearly as interesting as the atoms that came together to form you , or that cow , or this rock . and that is why , as carl sagan famously told us , we are all made of star stuff .

not the things themselves , mind you , but what they 're made of : the atoms that are the fabric of all things . to answer that question , we look to the law of conservation of mass . this law says take an isolated system defined by a boundary that matter and energy can not cross .

the law of conservation of mass says that mass can neither be _____ nor _____

there 's a prevailing attitude that art does n't matter in the real world . but the study of art can enhance our perception and our ability to translate to others what we see . those skills are useful . those skills can save lives . doctors , nurses , and law enforcement agents can use painting , sculpture , and photography as tools to improve their visual acuity and communication skills , which are critical during investigations and emergencies . if you 're treating an injury , investigating a crime scene , or trying to describe either of those things to a colleague , art can make you better at it . here , imagine you 're a seasoned cop or a dedicated doctor , but also imagine you are at a museum and let 's look at a painting . rene magritte 's `` time transfixed '' of 1938 depicts a mysterious and complex interior that invites analysis not unlike that required of a patient 's symptoms or the scene of a crime . a miniature train whose origin and destination are unknown is emerging from a fireplace , and the smoke from the locomotive appears to flow up the chimney as if from the fire that is conspicuously absent below . the eeriness of the scene is echoed in the empty living room , enhanced by wood-grain floors and decorative wall moldings to the right of the fireplace . perched atop the mantelpiece are two candlesticks and a clock . behind these objects is a large mirror that reveals an empty interior and only a partial reflection of the objects before it . the juxtaposition of the objects surrounding the moving train raises numerous questions for which there seem to be no apparent answers . did i summarize the painting accurately or leave any details out ? it 's no big deal if you see something else in a painting , but what if we 're both seasoned cops ? i call you for back-up . you show up only to realize the two bank robbing ninjas i 'd mentioned were actually six bank robbing ninjas with lasers . close study of art can train viewers to study thoroughly , analyze the elements observed , articulate them succinctly , and formulate questions to address the seeming inconsistencies . scrutinizing the details of an unfamiliar scene , in this case the work of art , and accurately conveying any observable contradictions is a critically important skill for both people who look at x-rays and those who interrogate suspects . let 's interrogate this painting , shall we ? okay , magritte , that 's quite a little picture you 've painted . but why are n't there any train tracks ? why no fire ? what happened to the candles ? why does n't the fireplace have a little tunnel for the train ? it just comes straight through the wall . and the clock says it 's about quarter to one , but i 'm not sure the light that comes through the window at an angle says it 's just past noontime . what 's this painting all about , anyway ? that 's when you , my trusty partner , hold me back , then i leave . you give magritte a cup of coffee and keep grilling him to see if this painting would hold up in court . viewers can provide a more detailed and accurate description of a situation by articulating what is seen and what is not seen . this is particularly important in medicine . if an illness is evidenced by three symptoms and only two are present in a patient , a medical professional must explicitly state the absence of that third symptom , signifying that the patient may not have the condition suspected . articulating the absence of a specific detail or behavior known as the pertinent negative is as critical as stating the details and behaviors that are present in order to treat the patient . and conspicuous absences are only conspicuous to eyes trained to look for them . art teaches professionals across a wide spectrum of fields not only how to ask more effective questions about what can not be readily answered , but also , and more importantly , how to analyze complex , real world situations from a new and different perspective , ultimately solving difficult problems . intense attention to detail , the ability to take a step back and look differently , we want first responders to have the analytical skills of master art historians at least . art trains us to investigate , and that 's a real world skill if there ever was one .

here , imagine you 're a seasoned cop or a dedicated doctor , but also imagine you are at a museum and let 's look at a painting . rene magritte 's `` time transfixed '' of 1938 depicts a mysterious and complex interior that invites analysis not unlike that required of a patient 's symptoms or the scene of a crime . a miniature train whose origin and destination are unknown is emerging from a fireplace , and the smoke from the locomotive appears to flow up the chimney as if from the fire that is conspicuously absent below .

which of these illustrates an inconsistency in time transfixed ?

there 's a concept that 's crucial to chemistry and physics . it helps explain why physical processes go one way and not the other : why ice melts , why cream spreads in coffee , why air leaks out of a punctured tire . it 's entropy , and it 's notoriously difficult to wrap our heads around . entropy is often described as a measurement of disorder . that 's a convenient image , but it 's unfortunately misleading . for example , which is more disordered - a cup of crushed ice or a glass of room temperature water ? most people would say the ice , but that actually has lower entropy . so here 's another way of thinking about it through probability . this may be trickier to understand , but take the time to internalize it and you 'll have a much better understanding of entropy . consider two small solids which are comprised of six atomic bonds each . in this model , the energy in each solid is stored in the bonds . those can be thought of as simple containers , which can hold indivisible units of energy known as quanta . the more energy a solid has , the hotter it is . it turns out that there are numerous ways that the energy can be distributed in the two solids and still have the same total energy in each . each of these options is called a microstate . for six quanta of energy in solid a and two in solid b , there are 9,702 microstates . of course , there are other ways our eight quanta of energy can be arranged . for example , all of the energy could be in solid a and none in b , or half in a and half in b . if we assume that each microstate is equally likely , we can see that some of the energy configurations have a higher probability of occurring than others . that 's due to their greater number of microstates . entropy is a direct measure of each energy configuration 's probability . what we see is that the energy configuration in which the energy is most spread out between the solids has the highest entropy . so in a general sense , entropy can be thought of as a measurement of this energy spread . low entropy means the energy is concentrated . high entropy means it 's spread out . to see why entropy is useful for explaining spontaneous processes , like hot objects cooling down , we need to look at a dynamic system where the energy moves . in reality , energy does n't stay put . it continuously moves between neighboring bonds . as the energy moves , the energy configuration can change . because of the distribution of microstates , there 's a 21 % chance that the system will later be in the configuration in which the energy is maximally spread out , there 's a 13 % chance that it will return to its starting point , and an 8 % chance that a will actually gain energy . again , we see that because there are more ways to have dispersed energy and high entropy than concentrated energy , the energy tends to spread out . that 's why if you put a hot object next to a cold one , the cold one will warm up and the hot one will cool down . but even in that example , there is an 8 % chance that the hot object would get hotter . why does n't this ever happen in real life ? it 's all about the size of the system . our hypothetical solids only had six bonds each . let 's scale the solids up to 6,000 bonds and 8,000 units of energy , and again start the system with three-quarters of the energy in a and one-quarter in b . now we find that chance of a spontaneously acquiring more energy is this tiny number . familiar , everyday objects have many , many times more particles than this . the chance of a hot object in the real world getting hotter is so absurdly small , it just never happens . ice melts , cream mixes in , and tires deflate because these states have more dispersed energy than the originals . there 's no mysterious force nudging the system towards higher entropy . it 's just that higher entropy is always statistically more likely . that 's why entropy has been called time 's arrow . if energy has the opportunity to spread out , it will .

it continuously moves between neighboring bonds . as the energy moves , the energy configuration can change . because of the distribution of microstates , there 's a 21 % chance that the system will later be in the configuration in which the energy is maximally spread out , there 's a 13 % chance that it will return to its starting point , and an 8 % chance that a will actually gain energy .

given that energy configuration a has 11,460 microstates and energy configuration has 3,820 microstates , how does the probability of energy configuration a occurring compare to the probability of b occurring ?

welcome to the ted-ed beta website tour . i 'm logan smalley , i 'm bedirhan cinar , i 'm jordan reeves , and i 'm stephanie lo . we represent the ted-ed team . we 're going to tell you about how the website is organized , about the lessons that surround each video , how you can customize or flip your own lesson , and how you can measure the lesson 's effect on your class or the world . towards the end of the tour , we 'll reveal one more major feature that directly affects every person viewing this video . let 's get started with the home page . on the home page , you 'll find original ted-ed videos , each is a lesson recorded by an actual educator that 's visualized by a professional animator . you can nominate educators and animators in the `` get involved '' section of the site . the ted-ed library can be browsed through two different lenses . learners can use the `` series '' view to browse videos thematically and based on their own curiosity . and teachers can use the browse by `` subject '' view to find the perfect short video to show in class or to assign as homework . every video on ted-ed is accompanied by a lesson . these lessons do n't replace good teaching , but they can be supplementary resources for students and teachers around the world . let 's look at this one , created by a teacher in the us and an animator in the uk . when you arrive on the lesson page , simply click play ; the video will continue to play as you navigate the lesson 's sections that surround it . in the `` quick quiz '' section , you 'll find multiple-choice questions that check for basic comprehension of the video . you get real-time feedback on your answers and if you get one wrong , you can use the video hint . you 'll find open-answer questions in the `` think '' section . and in the `` dig deeper '' section , you 'll find additional resources for exploring the topic . you can complete the lessons anonymously , but if you log in , you can track your own learning across the site . just visit the `` recent activity '' feed , and you 'll find answers you 've saved to lessons that you 've already started or completed . and now to one of the most powerful features of the ted-ed website : flipping a lesson . flipping a featured lesson allows you to edit each of the lesson 's sections . you can edit the title as it relates to your class . you can use the `` let 's begin '' section to provide instructions or context for the lesson . you can select or deselect any `` quick quiz '' question . in the `` think '' section , you can add your own open-answer questions . and in the `` dig deeper '' section , you can use the resources provided or add your own . when you finish flipping a lesson , it 'll publish to a new and unique url . and because the link is unique , it can measure the progress of any learner you share it with . you can use it to measure participation and accuracy of any individual student 's answers . so that 's how you flip a featured ted-ed video , we 've got one more major feature to tell you about . using the ted-ed platform , you can flip any video from youtube . that means you can create a lesson around any ted talk , any tedx talk , but also any of the other thousands of great educational videos on youtube , including the ones that you yourself could record , upload and flip . and through flipping these lessons , together we 'll create a free and remarkable library of lessons worth sharing .

welcome to the ted-ed beta website tour . i 'm logan smalley , i 'm bedirhan cinar , i 'm jordan reeves , and i 'm stephanie lo .

which feature of the ted-ed website excites you the most ?

cadmium ? yes ok oh yeah , that ’ s some ! that is cool man ! so cadmium is an element which is really quite similar to mercury and the way that most people have seen cadmium is that cadmium sulphide has a very strong orange colour and it is therefore used for dying things yellow or orange . if you look round your house or your parents ’ house , you may easily find a cast iron pot which has , a cooking pot , which has nice orange sides and orange lid and this is using cadmium sulphide as a glaze . so this is a sample which was generated or which was used by some of our researchers in the school of chemistry many years ago and this is a sample of cadmium metal . now it ’ s very interesting because it is stored in this really quite nice box which was perhaps a medication that somebody had bought , but if we open it… it 's also i believe , to colour the plastic pipe that you see in the street for gas pipes and so on . i think it is coloured with a cadmium compound . now in both these applications , even though that cadmium is quite poisonous , that they are so strongly fixed into the materials that it isn ’ t a threat to people . and we can see the lumps of the metallic cadmium . now i am not going to touch the cadmium because we know of some of the issues with toxicity . but it is used very often in batteries , or it was traditionally used in batteries . it is really important that we dispose of our batteries in a correct way .

cadmium ? yes ok oh yeah , that ’ s some !

because cadmium is toxic , we should dispose of used batteries in the correct way . like mercury and lead , why is cadmium especially dangerous , ?

in well-meaning attempts to boost our confidence ahead of challenging moments , people often try to draw our attention to our strengths : our intelligence , our competence , our experience . but this can – curiously – have some awkward consequences . there ’ s a type of under-confidence that arises specifically when we grow too attached to our own dignity and become anxious around any situation that might seem to threaten it . we hold back from challenges in which there is any risk of ending up looking ridiculous which comprises , of course , almost all the most interesting situations . in a foreign city , we might grow reluctant to ask anyone to guide us to the nice bars , because they might think us an ignorant , pitiable , lost tourist . we might long to kiss someone but never let on out of a fear that they could dismiss us as a predatory loser . or at work , we don ’ t apply for a promotion , in case the senior management deems us delusionally arrogant . in a concerted bid never to look foolish , we don ’ t venture very far from our cocoon , and thereby – from time to time at least – miss out on the best opportunities of our lives . at the heart of our under-confidence is a skewed picture of how dignified it is normal for a person to be . we imagine that it might be possible , after a certain age , to place ourselves beyond mockery . we trust that it 's an option to lead a good life without regularly making a complete idiot of ourselves . one of the most charming books ever written in early modern europe is called 'in praise of folly ' by the dutch scholar and philosopher , erasmus . in its pages , erasmus advances a hugely liberating argument . in a warm tone , he reminds us that everyone , however important and learned they might be , is a fool . no one is spared , not even the author . however well-schooled he himself was , erasmus remained – he insists – as much of a nitwit as anyone else : his judgement is faulty , his passions get the better of him , he is prey to superstition and irrational fear , he is shy whenever he has to meet new people , he drops things at elegant dinners . this is deeply cheering , for it means that our own repeated idiocies do n't have to exclude us from the best company . looking like a prick , making blunders and doing bizarre things in the night doesn ’ t render us unfit for society ; it just makes us a bit more like the greatest scholar of the northern european renaissance . there ’ s a similarly uplifting message to be pulled from the work of pieter brueghel . his central work , 'the dutch proverbs , ' presents a comically disenchanted view of human nature . everyone , he suggests , is pretty much deranged : here ’ s a man throwing his money into the river ; there ’ s a soldier squatting on the fire and burning his trousers ; someone is intently bashing his head against a brick wall ; someone else is biting a pillar . importantly , the painting is not an attack on just a few unusually awful people -- it ’ s a picture of parts of all of us . brueghel ’ s and erasmus ’ s work proposes that the way to greater confidence isn ’ t to reassure ourselves of our own dignity -- it ’ s to grow at peace with the inevitable nature of our ridiculousness . we are idiots now , we have been idiots in the past , and we will be idiots again in the future ... and that 's ok . there aren ’ t any other available options for human beings to be . once we learn to see ourselves as already , and by nature , foolish , it really doesn ’ t matter so much if we do one more thing that might make us look a bit stupid . the person we try to kiss could indeed think us ridiculous . the individual we asked directions from in a foreign city might regard us with contempt . but if these people did so , it wouldn ’ t be news to us -- they would only be confirming what we had already gracefully accepted in our hearts long ago : that we , like them – and every other person on the earth – are a nitwit . the risk of trying and failing would have its sting substantially removed . a fear of humiliation would no longer stalk us in the shadows of our minds . we would grow free to give things a go by accepting that failure was the acceptable norm . and every so often , amidst the endless rebuffs we ’ d have factored in from the outset , it would work : we ’ d get a kiss , we ’ d make a friend , we ’ d get a raise . the road to greater confidence begins with a ritual of telling oneself solemnly every morning before heading out for the day , that one is a muttonhead , a cretin , a dumbbell and an imbecile . one or two more acts of folly should , thereafter , not matter very much at all .

we trust that it 's an option to lead a good life without regularly making a complete idiot of ourselves . one of the most charming books ever written in early modern europe is called 'in praise of folly ' by the dutch scholar and philosopher , erasmus . in its pages , erasmus advances a hugely liberating argument . in a warm tone , he reminds us that everyone , however important and learned they might be , is a fool .

what was the central argument of erasmus ' in praise of folly ?

the five fingers of evolution . a thorough understanding of biology requires a thorough understanding of the process of evolution . most people are familiar with the process of natural selection . however , this is just one of five processes that can result in evolution . before we discuss all five of these processes , we should define evolution . evolution is simply change in the gene pool over time . but what is a gene pool ? and for that matter , what is a gene ? before spending any more time on genetics , let us begin with a story . imagine that a boat capsizes , and 10 survivors swim to shore on a deserted island . they are never rescued , and they form a new population that exists for thousands of years . strangely enough , five of the survivors have red hair . red hair is created when a person inherits two copies of the red gene from their parents . if you only have one copy of the gene , you wo n't have red hair . to make this easier , we will assume that the five non-redheads are not carriers of the gene . the initial frequency of the red-hair gene is therefore 50 percent , or 10 of 20 total genes . these genes are the gene pool . the 20 different genes are like cards in a deck that keep getting reshuffled with each new generation . sex is simply a reshuffling of the genetic deck . the cards are reshuffled and passed to the next generation ; the deck remains the same , 50 percent red . the genes are reshuffled and passed to the next generation ; the gene pool remains the same , 50 percent red . even though the population may grow in size over time , the frequency should stay at about 50 percent . if this frequency ever varies , then evolution has occurred . evolution is simply change in the gene pool over time . think about it in terms of the cards . if the frequency of the cards in the deck ever changes , evolution has occurred . there are five processes that can cause the frequency to change . to remember these processes , we will use the fingers on your hands , starting from the little finger and moving to the thumb . the little finger should remind you that the population can shrink . if the population shrinks , then chance can take over . for example , if only four individuals survive an epidemic , then their genes will represent the new gene pool . the next finger is the ring finger . this finger should remind you of mating , because a ring represents a couple . if individuals choose a mate based on their appearance or location , the frequency may change . if redheaded individuals only mate with redheaded individuals , they could eventually form a new population . if no one ever mates with redheaded individuals , these genes could decrease . the next finger is the middle finger . the m in the middle finger should remind you of the m in the word `` mutation . '' if a new gene is added through mutation , it can affect the frequency . imagine a gene mutation creates a new color of hair . this would obviously change the frequency in the gene pool . the pointer finger should remind you of movement . if new individuals flow into an area , or immigrate , the frequency will change . if individuals flow out of an area , or emigrate , then the frequency will change . in science , we refer to this movement as gene flow . all four of the processes represented by our fingers can cause evolution . small population size , non-random mating , mutations and gene flow . however , none of them lead to adaptation . natural selection is the only process that creates organisms better adapted to their local environment . i use the thumb to remember this process . nature votes thumbs up for adaptations that will do well in their environment , and thumbs down to adaptations that will do poorly . the genes for individuals that are not adapted for their environment will gradually be replaced by those that are better adapted . red hair is an example of one of these adaptations . red hair is an advantage in the northern climates , because the fair skin allowed ancestors to absorb more light and synthesize more vitamin d. thumbs up ! however , this was a disadvantage in the more southern climates , where increased uv radiation led to cancer and decreased fertility . thumbs down ! even the thumb itself is an adaptation formed through the process of natural selection . the evolution that we have described is referred to as microevolution , because it refers to a small change . however , this form of evolution may eventually lead to macroevolution , or speciation . every organism on the planet shares ancestry with a single common ancestor . all living organisms on the planet are connected back in time through the process of evolution . take a look at your own hand . it 's an engineering masterpiece that was created by the five processes i just described , over millions and millions of years . can you recall the five main causes of evolution from memory ? if you ca n't , hit rewind and watch that part again . but if you can , give yourself or your neighbor a big five-fingered high five .

the initial frequency of the red-hair gene is therefore 50 percent , or 10 of 20 total genes . these genes are the gene pool . the 20 different genes are like cards in a deck that keep getting reshuffled with each new generation .

microevolution is changes in the frequency of genes in a gene pool . according to this definition what is the smallest biological unit that can evolve ?

one of the great things about science is that when scientists make a discovery , it 's not always in a prescribed manner , as in , only in a laboratory under strict settings , with white lab coats and all sorts of neat science gizmos that go , `` beep ! '' in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get . my case in point : the weird history of the cell theory . there are three parts to the cell theory . one : all organisms are composed of one or more cells . two : the cell is the basic unit of structure and organization in organisms . and three : all cells come from preexisting cells . to be honest , this all sounds incredibly boring until you dig a little deeper into how the world of microscopic organisms , and this theory came to be . it all started in the early 1600s in the netherlands , where a spectacle maker named zacharias janssen is said to have come up with the first compound microscope , along with the first telescope . both claims are often disputed , as apparently he was n't the only bored guy with a ton of glass lenses to play with at the time . despite this , the microscope soon became a hot item that every naturalist or scientist at the time wanted to play with , making it much like the ipad of its day . one such person was a fellow dutchman by the name of anton van leeuwenhoek , who heard about these microscope doohickeys , and instead of going out and buying one , he decided to make his own . and it was a strange little contraption indeed , as it looked more like a tiny paddle the size of a sunglass lens . if he had stuck two together , it probably would have made a wicked set of sunglasses that you could n't see much out of . anyhoo , once leeuwenhoek had his microscope ready , he went to town , looking at anything and everything he could with them , including the gunk on his teeth . yes , you heard right . he actually discovered bacteria by looking at dental scrapings , which , when you keep in mind that people did n't brush their teeth much -- if at all -- back then , he must have had a lovely bunch of bacteria to look at . when he wrote about his discovery , he did n't call them bacteria , as we know them today . but he called them `` animalcules , '' because they looked like little animals to him . while leeuwenhoek was staring at his teeth gunk , he was also sending letters to a scientific colleague in england , by the name of robert hooke . hooke was a guy who really loved all aspects of science , so he dabbled in a little bit of everything , including physics , chemistry and biology . thus it is hooke who we can thank for the term `` the cell , '' as he was looking at a piece of cork under his microscope , and the little chambers he saw reminded him of cells , or the rooms monks slept in in their monasteries . think college dorm rooms , but without the tvs , computers and really annoying roommates . hooke was something of an underappreciated scientist of his day -- something he brought upon himself , as he made the mistake of locking horns with one of the most famous scientists ever , sir isaac newton . remember when i said hooke dabbled in many different fields ? well , after newton published a groundbreaking book on how planets move due to gravity , hooke made the claim that newton had been inspired by hooke 's work in physics . newton , to say the least , did not like that , which sparked a tense relationship between the two that lasted even after hooke died , as quite a bit of hooke 's research -- as well as his only portrait -- was ... misplaced , due to newton . much of it was rediscovered , thankfully , after newton 's time , but not his portrait , as , sadly , no one knows what robert hooke looked like . fast-forward to the 1800s , where two german scientists discovered something that today we might find rather obvious , but helped tie together what we now know as the cell theory . the first scientist was matthias schleiden , a botanist who liked to study plants under a microscope . from his years of studying different plant species , it finally dawned on him that every single plant he had looked at were all made of cells . at the same time , on the other end of germany was theodor schwann , a scientist who not only studied slides of animal cells under the microscope and got a special type of nerve cell named after him , but also invented rebreathers for firefighters , and had a kickin ' pair of sideburns . after studying animal cells for a while , he , too , came to the conclusion that all animals were made of cells . immediately , he reached out via snail mail , as twitter had yet to be invented , to other scientists working in the same field with schleiden , who got back to him , and the two started working on the beginnings of the cell theory . a bone of contention arose between them . as for the last part of the cell theory -- that cells come from preexisting cells -- schleiden did n't exactly subscribe to that thought , as he swore cells came from free-cell formation , where they just kind of spontaneously crystallized into existence . that 's when another scientist named rudolph virchow , stepped in with research showing that cells did come from other cells , research that was actually -- hmm ... how to put it ? -- `` borrowed without permission '' from a jewish scientist by the name of robert remak , which led to two more feuding scientists . thus , from teeth gunk to torquing off newton , crystallization to schwann cells , the cell theory came to be an important part of biology today . some things we know about science today may seem boring , but how we came to know them is incredibly fascinating . so if something bores you , dig deeper . it 's probably got a really weird story behind it somewhere .

in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get . my case in point : the weird history of the cell theory . there are three parts to the cell theory . one : all organisms are composed of one or more cells .

why do you think there were so many heated debates around the development of the cell theory ?

translator : andrea mcdonough reviewer : jessica ruby in the 11th and 12th centuries , most english commoners were illiterate . since they had no way to learn the bible , the clergy came up with an inventive solution : they 'd create plays out of certain bible stories so even people who could n't read could learn them . these were called mystery plays because they revealed the mystery of god 's word . at about the same time , the clergy also developed plays about the saints of the church , called miracle plays . in the beginning , the clergy members acted out bible stories on the steps outside the cathedral . the audience reacted so well that soon they needed to move out to the street around the town square . by building moving carts to put on each play and by lining up one after the other , they could put on cycles of stories , which would take the viewer from genesis to revelation . these movable carts , called pageants , looked like huge boxes on wheels . each was two stories tall . the bottom story was curtained off and was used for costumes , props , and dressing . the top platform was the stage for the performance . spectators assembled in various corners of the town , and the pageant would move around in the cycle until the villagers had seen the entire series . soon , the plays required more actors than the clergy could supply . so , by the 13th century , different guilds were asked to be responsible for acting out different parts of the cycle . the assignments were meant to reflect the guilds ' professions . for example , the carpenter 's guild might put on the story of noah 's ark , and the baker 's guild might put on the last supper . can you imagine what might happen to the story if the butcher 's guild put on the crucifixion of christ ? yes , without the clergy , the plays soon started changing from their true bible stories . by the end of the 14th century , a new form of drama , called the morality play , had evolved . faith , truth , charity , and good deeds all became characters on the stage . and , at the same time , the opposite virtues of falsehood , covetousness , worldly flesh , and the devil became the antagonists . the morality plays were allegorical stories in which these characters battled for the control of the soul . audiences loved the immoral characters , and spectators were encouraged to interact with the actors . throwing rotten food and even getting into scuffles with other spectators became very common . the character of the devil often would roam through the crowds and pull unsuspecting watchers into a hell that was depicted as a dragon 's mouth . the virtuous biblical stories had morphed into crude and sometimes comic stories . the clergy intended to teach against immorality . how ironic , then , that the morality plays actually encouraged vices as more popular than virtues . by the mid-15th century , the church started to outlaw these performances . town charters required that any theater must be built outside the city wall . one of the first theaters was built like a larger version of a pageant , with tiers of gallery seating encircling a grassy area in front of the stage . sound familiar ? a young william shakespeare developed his craft here at the theater that was eventually renamed the globe . the medieval morality play had led to renaissance playwrights who were inspired by the inner struggles and the conscience of man . and that , in essence , is how drama emerged as a literary art form .

these were called mystery plays because they revealed the mystery of god 's word . at about the same time , the clergy also developed plays about the saints of the church , called miracle plays . in the beginning , the clergy members acted out bible stories on the steps outside the cathedral .

in what order were the plays developed ?

everyone knows that stories are made up of words , from short poems to epic novels . but did you know that a single word itself can tell an entire story ? you see , just as we can look at a story 's plot , setting , and characters , we can also study the history of an individual word , where it developed , and the cultures and people who helped shape it . looking into the story of a word is like counting the rings of a tree . newer words , like google or cyborg , have shorter stories . but the older the word , the longer the story and the more it stands to reveal to us not only about itself , but about ourselves and our history . the oldest words in present-day english are those that come from old english , the ancestor of our modern language whose first seeds were planted about 1500 years ago . compared to languages like greek or chinese that date back thousands of years , english is just a sapling in the lexical forest . but the stories of its words often start long before english itself took root . one such word is the familiar word true , as in true stories . let 's take a look . true usually means factual , correct , or faithful to reality . it can also mean exact , properly positioned , upright , or straight . a true friend is loyal , reliable , faithful , and steadfast . the word true is a simple word , and we can add some affixes to grow its family tree with words like truer , truest , truly , truth , and untruth . but if we go in the other direction to look at the roots of true itself , we find even more relatives further up the family tree . the words trust , bethroth , and truce all derive from the same source as true , and these words all denote faithfulness or confidence . a thousand years ago , the word true looked and sounded different than it does today . in several old english dialects , the word treow was a noun that meant good faith or trust , a pledge or a promise . but it also had another definition , tree , and that 's no coincidence . if we trace the roots back even farther , we find that both meanings derive from a common origin , where some of the earliest expressions of the concept of truth were associated with the uprightness of an oak , the steadiness of a silver birch , and the fidelity of an orchard baring fruit year after year . this may sound like a stretch at first , but trees are the oldest living organisms on this planet . some that would have been called treow long ago still stand today . the fortingall yew in scotland is more than 2,000 years old . a californian bristlecone pine is more than 5,000 . and utah 's pando-quaking aspen grove has a single root system that dates back more than 80 millennia . trees have also held a sacred place in many cultures throughout history . the celtic peoples who first inhabited the british isles believed that trees housed deities . and , in fact , the ancient druids take their name from the same ancient root as tree . planting a tree is itself an act of faith and commitment . not only are trees upright and prototypically straight , but they are actual , solid , and real , something you can see and touch . and they are as reliable and steadfast to us today as they were a millennium ago , nurturing us , sheltering us , and providing the pages of our books . philosophers and poets , people in search of the truth , have often sought it in trees . `` what did the tree learn from the earth to be able to talk with the sky ? '' asked pablo neruda . `` a tree falls the way it leans , '' says an old proverb . just as trees mark our landscapes and witness our histories , the stories of words landscape our language , capturing the rains and sunshine of generations and sending roots and branches far and wide . as there is a whole orchard in a single seed , there is a whole story in a single word , and that 's the truth .

the celtic peoples who first inhabited the british isles believed that trees housed deities . and , in fact , the ancient druids take their name from the same ancient root as tree . planting a tree is itself an act of faith and commitment .

which ancient celtic group takes its name from a root meaning 'tree ' ?

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 .

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 .

natron is :

many of the inanimate objects around you probably seem perfectly still . but look deep into the atomic structure of any of them , and you 'll see a world in constant flux . stretching , contracting , springing , jittering , drifting atoms everywhere . and though that movement may seem chaotic , it 's not random . atoms that are bonded together , and that describes almost all substances , move according to a set of principles . for example , take molecules , atoms held together by covalent bonds . there are three basic ways molecules can move : rotation , translation , and vibration . rotation and translation move a molecule in space while its atoms stay the same distance apart . vibration , on the other hand , changes those distances , actually altering the molecule 's shape . for any molecule , you can count up the number of different ways it can move . that corresponds to its degrees of freedom , which in the context of mechanics basically means the number of variables we need to take into account to understand the full system . three-dimensional space is defined by x , y , and z axes . translation allows the molecule to move in the direction of any of them . that 's three degrees of freedom . it can also rotate around any of these three axes . that 's three more , unless it 's a linear molecule , like carbon dioxide . there , one of the rotations just spins the molecule around its own axis , which does n't count because it does n't change the position of the atoms . vibration is where it gets a bit tricky . let 's take a simple molecule , like hydrogen . the length of the bond that holds the two atoms together is constantly changing as if the atoms were connected by a spring . that change in distance is tiny , less than a billionth of a meter . the more atoms and bonds a molecule has , the more vibrational modes . for example , a water molecule has three atoms : one oxygen and two hydrogens , and two bonds . that gives it three modes of vibration : symmetric stretching , asymmetric stretching , and bending . more complicated molecules have even fancier vibrational modes , like rocking , wagging , and twisting . if you know how many atoms a molecule has , you can count its vibrational modes . start with the total degrees of freedom , which is three times the number of atoms in the molecule . that 's because each atom can move in three different directions . three of the total correspond to translation when all the atoms are going in the same direction . and three , or two for linear molecules , correspond to rotations . all the rest , 3n-6 or 3n-5 for linear molecules , are vibrations . so what 's causing all this motion ? molecules move because they absorb energy from their surroundings , mainly in the form of heat or electromagnetic radiation . when this energy gets transferred to the molecules , they vibrate , rotate , or translate faster . faster motion increases the kinetic energy of the molecules and atoms . we define this as an increase in temperature and thermal energy . this is the phenomenon your microwave oven uses to heat your food . the oven emits microwave radiation , which is absorbed by the molecules , especially those of water . they move around faster and faster , bumping into each other and increasing the food 's temperature and thermal energy . the greenhouse effect is another example . some of the solar radiation that hits the earth 's surface is reflected back to the atmosphere . greenhouse gases , like water vapor and carbon dioxide absorb this radiation and speed up . these hotter , faster-moving molecules emit infrared radiation in all directions , including back to earth , warming it . does all this molecular motion ever stop ? you might think that would happen at absolute zero , the coldest possible temperature . no one 's ever managed to cool anything down that much , but even if we could , molecules would still move due to a quantum mechanical principle called zero-point energy . in other words , everything has been moving since the universe 's very first moments , and will keep going long , long after we 're gone .

that 's three degrees of freedom . it can also rotate around any of these three axes . that 's three more , unless it 's a linear molecule , like carbon dioxide .

the movement of any given molecule around its axes is known as :

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 .

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 .

the shape memory wire changes shape mostly by

( music ) esteemed members of the jury , i submit the following words for immediate and violent execution and extraction from our vocabularies , to be locked away forever , if you would prefer . these words i present to you are `` good '' and `` bad . '' these words have served as treacherous liars for eternity . these two words have worked in tandem to produce vague and bland sentences that have crippled the creativity of humanity . these two deceptively tiny words stifle real description and honest communication . look at them , just sitting there on this page , all smug and satisfied with their work . how dare they ? you serve no purpose in our world , and we must rid ourselves of your influence . we must replace these two words with the truth , with phrases that include adequate and sincere adjectives . i 'll offer you `` radiant , '' `` stupefying , '' `` awful , '' `` gut-wrenching . '' these choices create clarity and depth . `` good '' and `` bad '' only provide gray vagueness . we must demand color ! we should even use winding similes and metaphors , where appropriate . we have to do whatever we can and should to make our real sentiments known . `` good '' and `` bad '' will no longer be our go-to words that we rely on when we are too afraid or too languid to express our real thoughts . ladies and gentlemen of the jury , i implore you to deliver a verdict of guilty and send these words to their rightful fate . now imagine a world without these two words . imagine a world where real description is required , digging further into our vocabulary than just a monosyllabic effort to get away with not being honest , impactful , creative . how does my hair look ? good . what is that ? a dull attempt not to be honest ? perhaps my hair looks like a hideous mess of tangles and bald spots . yet someone does not want to be honest , and offers the quick fix `` good , '' to try and mask the truth and send me hurling into the evening with a plop of disorganized tresses . this will not do . perhaps my hair looks like an amazing glossy sculpture that frames my face perfectly , and lends an air of magic to the night . well , `` good '' just does n't cut it . i wo n't take any more of this formless , lifeless description . i will not take these lies , and neither should you . a doctor asks you how you feel . `` i feel bad . '' heresy ! the doctor , based on this paltry report , could conclude that you have brain cancer or the flu or rabies . you owe it to yourself and the possible misdiagnosis of your life to be honest about exactly how you feel . `` i feel like a herd of wombats has taken up in my chest . '' a-ha ! there we have it . an accurate description . now the doctor has some real evidence to work with in order to assist you . we have become addicted to the numbness that `` good '' and `` bad '' have created . we have become linguistic slobs , churning out `` good '' and `` bad '' wherever we are too lazy to allow our minds to communicate with creativity and specification . you look good , you sound bad , this tastes good , the weather looks bad . lie after lie , repeating this verbal gray , this sloshy mush , this fuzzy picture that reflects no real truth . replace them with grittier , exact terms that have been buried in our lexis , waiting to see daylight . no longer does the weather look good or bad , the weather looks ominous or exhilarating . nothing tastes good or bad . it tastes like pillows of sparkles or old shoe and dung . no more of sounding good or bad . you sound like lilting baby laughter or ogres marching to war . dear god , you do not look good or bad . you look like a feathery angel or a morose faun . today , you look at these two words , `` good '' and `` bad , '' examine them closely . because behind their seemingly unassuming visages reside two deceitful offerings that smother the truth . these words are liars . these words must be stopped . remove them from our language so that honesty can return to our communication . ladies and gentlemen , if i say to you that you have been a good jury , you will take the compliment , make your decision and go on about your day . but if i say to you that you are an honorable jury , and that i hope your unshakeable determination to better the vocabulary of humanity will result in finding `` good '' and `` bad '' guilty , you will recognize the ingenuity of this argument and find `` good '' and `` bad '' guilty . ( music )

we have to do whatever we can and should to make our real sentiments known . `` good '' and `` bad '' will no longer be our go-to words that we rely on when we are too afraid or too languid to express our real thoughts . ladies and gentlemen of the jury , i implore you to deliver a verdict of guilty and send these words to their rightful fate .

why does neel suppose we rely on good and bad as go to words to express our thoughts ?

if insects suddenly morphed into large beings , and decided to wage war on us , there 's no doubt that humans would lose . we 'd simply be crushed by their sheer numbers . there are an estimated 10 quintillion individual insects on earth . that 's a one followed by 19 zeroes . so , compared with our population of about 7 billion , these invertebrates outnumber us by more than a billion to one . their astounding numbers exist at the species level , as well . there are more than 60,000 vertebrate species on the planet . but the class of insects contains a million known species , and many others that have n't been classified . in fact , these critters make up approximately 75 % of all animals on earth . so , what 's their secret to success ? insect abundance comes down to many things that together make them some of the most adaptable and resilient creatures , beginning with their impressive ability to breed . many species can produce hundreds of offspring within their lifetimes . most offspring will die , but more than enough will survive into adulthood to reproduce . offspring also mature very rapidly , so the cycle of reproduction resumes quickly , and can occur over and over again in a short time . these numbers mean that as a class , insects harbor a tremendous amount of genetic diversity . the different species contain a wealth of genetic data that give them the necessary adaptations they need to thrive in a range of environments across the planet . even some of the most extreme environments are in bounds ; flat bark beetles can live at -40 degrees fahrenheit , sahara desert ants can venture out when surface temperatures exceed 155 degrees , and some bumblebees can survive 18,000 feet above sea level . insect exoskeletons also work like body armor , protecting insects against the outside world and helping them cope with habitats that other creatures ca n't . even their small size , which we might see as a disadvantage , is something they use to their benefit . because most species are so tiny , millions of insects can inhabit a small space and make use of all the available resources within it . this means they can occupy hundreds of different niches across ecosystems . some insects survive by eating the roots , stems , leaves , seeds , pollen , and nectar of specific plants . others , like wasps , make use of live insects by paralyzing the victims and laying their eggs inside so that when the hatchlings emerge , they can eat their way out and get nourishment . mosquitos and biting flies feed on blood , taking advantage of this unusual resource to ensure their survival . and a whole bunch of other insects have built a niche around feces . flies lay their eggs there , and some beetles even build large balls out of animal dung , which they eat and use as accommodation for their eggs . and then there 's the insects ' mighty power of metamorphosis . this trait not only transforms insects , but also helps them maximize the available resources in an ecosystem . take butterflies . in their larval caterpillar form , they chomp hungrily through leaves at a rapid rate to help them grow and spin cocoons . but when they emerge as butterflies , these insects feed only on flower nectar . metamorphosis means the larvae and adults of one species will never compete for the same resource , so they successfully share an ecological niche without limiting their own success . this process is so efficient that an incredible 86 % of insect species undergo complete metamorphosis . we 're big and they 're small , so it 's easy to forget that these critters are moving in their millions all around us , all the time . but examine almost any patch of ground , and you 're sure to find them there . their numbers are immense , and their success is unmatched . we may have to accept that it 's insects , not us , that are the true conquerors of the planet .

we 'd simply be crushed by their sheer numbers . there are an estimated 10 quintillion individual insects on earth . that 's a one followed by 19 zeroes .

how many insects are there on earth ?

when i was in fourth grade , my teacher said to us one day : `` there are as many even numbers as there are numbers . '' `` really ? `` , i thought . well , yeah , there are infinitely many of both , so i suppose there are the same number of them . but even numbers are only part of the whole numbers , all the odd numbers are left over , so there 's got to be more whole numbers than even numbers , right ? to see what my teacher was getting at , let 's first think about what it means for two sets to be the same size . what do i mean when i say i have the same number of fingers on my right hand as i do on left hand ? of course , i have five fingers on each , but it 's actually simpler than that . i do n't have to count , i only need to see that i can match them up , one to one . in fact , we think that some ancient people who spoke languages that did n't have words for numbers greater than three used this sort of magic . for instance , if you let your sheep out of a pen to graze , you can keep track of how many went out by setting aside a stone for each one , and putting those stones back one by one when the sheep return , so you know if any are missing without really counting . as another example of matching being more fundamental than counting , if i 'm speaking to a packed auditorium , where every seat is taken and no one is standing , i know that there are the same number of chairs as people in the audience , even though i do n't know how many there are of either . so , what we really mean when we say that two sets are the same size is that the elements in those sets can be matched up one by one in some way . my fourth grade teacher showed us the whole numbers laid out in a row , and below each we have its double . as you can see , the bottom row contains all the even numbers , and we have a one-to-one match . that is , there are as many even numbers as there are numbers . but what still bothers us is our distress over the fact that even numbers seem to be only part of the whole numbers . but does this convince you that i do n't have the same number of fingers on my right hand as i do on my left ? of course not . it does n't matter if you try to match the elements in some way and it does n't work , that does n't convince us of anything . if you can find one way in which the elements of two sets do match up , then we say those two sets have the same number of elements . can you make a list of all the fractions ? this might be hard , there are a lot of fractions ! and it 's not obvious what to put first , or how to be sure all of them are on the list . nevertheless , there is a very clever way that we can make a list of all the fractions . this was first done by georg cantor , in the late eighteen hundreds . first , we put all the fractions into a grid . they 're all there . for instance , you can find , say , 117/243 , in the 117th row and 223rd column . now we make a list out of this by starting at the upper left and sweeping back and forth diagonally , skipping over any fraction , like 2/2 , that represents the same number as one the we 've already picked . we get a list of all the fractions , which means we 've created a one-to-one match between the whole numbers and the fractions , despite the fact that we thought maybe there ought to be more fractions . ok , here 's where it gets really interesting . you may know that not all real numbers -- that is , not all the numbers on a number line -- are fractions . the square root of two and pi , for instance . any number like this is called irrational . not because it 's crazy , or anything , but because the fractions are ratios of whole numbers , and so are called rationals ; meaning the rest are non-rational , that is , irrational . irrationals are represented by infinite , non-repeating decimals . so , can we make a one-to-one match between the whole numbers and the set of all the decimals , both the rationals and the irrationals ? that is , can we make a list of all the decimal numbers ? candor showed that you ca n't . not merely that we do n't know how , but that it ca n't be done . look , suppose you claim you have made a list of all the decimals . i 'm going to show you that you did n't succeed , by producing a decimal that is not on your list . i 'll construct my decimal one place at a time . for the first decimal place of my number , i 'll look at the first decimal place of your first number . if it 's a one , i 'll make mine a two ; otherwise i 'll make mine a one . for the second place of my number , i 'll look at the second place of your second number . again , if yours is a one , i 'll make mine a two , and otherwise i 'll make mine a one . see how this is going ? the decimal i 've produced ca n't be on your list . why ? could it be , say , your 143rd number ? no , because the 143rd place of my decimal is different from the 143rd place of your 143rd number . i made it that way . your list is incomplete . it does n't contain my decimal number . and , no matter what list you give me , i can do the same thing , and produce a decimal that 's not on that list . so we 're faced with this astounding conclusion : the decimal numbers can not be put on a list . they represent a bigger infinity that the infinity of whole numbers . so , even though we 're familiar with only a few irrationals , like square root of two and pi , the infinity of irrationals is actually greater than the infinity of fractions . someone once said that the rationals -- the fractions -- are like the stars in the night sky . the irrationals are like the blackness . cantor also showed that , for any infinite set , forming a new set made of all the subsets of the original set represents a bigger infinity than that original set . this means that , once you have one infinity , you can always make a bigger one by making the set of all subsets of that first set . and then an even bigger one by making the set of all the subsets of that one . and so on . and so , there are an infinite number of infinities of different sizes . if these ideas make you uncomfortable , you are not alone . some of the greatest mathematicians of cantor 's day were very upset with this stuff . they tried to make this different infinities irrelevant , to make mathematics work without them somehow . cantor was even vilified personally , and it got so bad for him that he suffered severe depression , and spent the last half of his life in and out of mental institutions . but eventually , his ideas won out . today , they 're considered fundamental and magnificent . all research mathematicians accept these ideas , every college math major learns them , and i 've explained them to you in a few minutes . some day , perhaps , they 'll be common knowledge . there 's more . we just pointed out that the set of decimal numbers -- that is , the real numbers -- is a bigger infinity than the set of whole numbers . candor wondered whether there are infinities of different sizes between these two infinities . he did n't believe there were , but could n't prove it . candor 's conjecture became known as the continuum hypothesis . in 1900 , the great mathematician david hilbert listed the continuum hypothesis as the most important unsolved problem in mathematics . the 20th century saw a resolution of this problem , but in a completely unexpected , paradigm-shattering way . in the 1920s , kurt gödel showed that you can never prove that the continuum hypothesis is false . then , in the 1960s , paul j. cohen showed that you can never prove that the continuum hypothesis is true . taken together , these results mean that there are unanswerable questions in mathematics . a very stunning conclusion . mathematics is rightly considered the pinnacle of human reasoning , but we now know that even mathematics has its limitations . still , mathematics has some truly amazing things for us to think about .

so we 're faced with this astounding conclusion : the decimal numbers can not be put on a list . they represent a bigger infinity that the infinity of whole numbers . so , even though we 're familiar with only a few irrationals , like square root of two and pi , the infinity of irrationals is actually greater than the infinity of fractions .

which infinity is bigger , the whole numbers or the decimals ?

how do you imagine the life of a scientist ? boring and monotonous , spending endless hours in the lab with no social interaction ? maybe for some but not tycho brahe . the 16th century scholar who accurately predicted planetary motion and cataloged hundreds of stars before the telescope had been invented also had a cosmic-sized personal life . tycho brahe was born in 1546 to danish nobles , but at age two was kidnapped to be raised by his uncle instead . his parents did n't seem to mind . tycho was supposed to have a career in law , but after witnessing a solar eclipse at thirteen , he began spending more time with mathematics and science professors , who taught him the art of celestial observation . by the time tycho 's uncle sent him off to germany a few years later , he had lost interest in his law studies , instead reading astronomy books , improving his instruments , and taking careful notes of the night skies . it was n't long before his own measurements were more accurate than those in his books . while in germany , tycho got into a bit of an argument with another student at a party over a mathematical formula , resulting in a sword duel and tycho losing a good-sized chunk of his nose . after that , he was said to have worn a realistic prosthetic of gold and silver that he would glue onto his face . fortunately , tycho did n't need his nose to continue his astronomical work . he kept studying the night sky and creating all sorts of instruments , including a building-sized quadrant for measuring the angles of stars . after months of careful observation , tycho discovered a new star in the constellation cassiopeia . the publication of this discovery granted him rock star status and offers of scientific positions all over europe . wanting to keep him at home , the king of denmark offered to give tycho his own personal island with a state of the art observatory . called uraniborg and costing about 1 % of denmark 's entire budget , this observatory was more of a castle , containing formal gardens , rooms for family , staff and visiting royalty , and an underground section just for all the giant instruments . tycho also built a papermill and printing press for publishing his papers , and a lab for studying alchemy . and since no castle would be complete without entertainment , tycho employed a clairvoyant dwarf named jep as court jester . tycho lived on his island , studying and partying for about 20 years . but after falling out with the new danish king , he took up an invitation from the holy roman emperor to become the official imperial astronomer in prague . there , he met another famous astronomer johannes kepler , who became his assistant . while kepler 's work interested him , tycho was protective of his data , and the two often got into heated arguments . in 1601 , tycho attended a formal banquet where he drank quite a lot but was too polite to leave the table to relieve himself , deciding to tough it out instead . this proved to be a bad idea , as he quickly developed a bladder infection and died a few days later . but over 400 years after his death , tycho still had a few surprises up his sleeve . when his body was exhumed and studied in 2010 , the legendary gold and silver nose was nowhere to be found , with chemical traces suggesting that he wore a more casual brass nose instead . tycho 's mustache hair was also found to contain unusually high levels of toxic mercury . was it from a medicine used to treat his bladder infection ? a residue from his alchemy experiments ? or did his quarrelsome coworker johannes kepler poison him to acquire his data ? we may never know , but the next time you think scientists lead boring lives , dig a little deeper . a fascinating story may be just beyond the tip of your nose .

it was n't long before his own measurements were more accurate than those in his books . while in germany , tycho got into a bit of an argument with another student at a party over a mathematical formula , resulting in a sword duel and tycho losing a good-sized chunk of his nose . after that , he was said to have worn a realistic prosthetic of gold and silver that he would glue onto his face .

what was the subject of the argument that eventually ended in a sword duel and the loss of part of brahe ’ s nose ?

some are longer than a blue whale . others are barely larger than a grain of sand . one species unleashes one of the most deadly venoms on earth . another holds a secret that 's behind some of the greatest breakthroughs in biology . they 've inhabited the ocean for at least half a billion years , and they 're still flourishing as the sea changes around them . jellyfish are soft-bodied sea creatures that are n't really fish . they 're part of a diverse team of gelatinous zooplankton , zooplankton being animals that drift in the ocean . there are more than 1,000 species of jellyfish , and many others that are often mistaken for them . a noted feature of jellyfish is a translucent bell made of a soft delicate material called mesoglea . sandwiched between two layers of skin , the mesoglea is more than 95 % water held together by protein fibers . the jellyfish can contract and relax their bells to propel themselves . they do n't have a brain or a spinal cord , but a neural net around the bell 's inner margin forms a rudimentary nervous system that can sense the ocean 's currents and the touch of other animals . jellyfish do n't have typical digestive systems , either . these gelatinous carnivores consume plankton and other small sea creatures through a hole in the underside of their bells . the nutrients are absorbed by an inner layer of cells with waste excreted back through their mouths . but the jellyfish 's relatively simple anatomy does n't prevent it from having some remarkable abilities . one kind of box jellyfish has 24 eyes . scientists think it can see color and form images within its simple nervous system . four of its eyes are curved upward on stalks . this allows the jellyfish to peer through the surface of the water , looking for the canopy of the mangrove trees where it feeds . in fact , this may be one of the only creatures with a 360-degree view of its environment . the jellyfish 's sting , which helps it capture prey and defend itself , is its most infamous calling card . in the jelly 's epidermis , cells called nematocysts lie coiled like poisonous harpoons . when they 're triggered by contact , they shoot with an explosive force . it exerts over 550 times the pressure of mike tyson 's strongest punch to inject venom into the victim . some jellyfish stings barely tingle , but others cause severe skin damage . the venom of one box jellyfish can kill a human in under five minutes , making it one of the most potent poisons of any animal in the world . other jellyfish superpowers are less lethal . one species of jellyfish glows green when it 's agitated , mostly thanks to a biofluorescent compound called green fluorescent protein , or gfp . scientists isolated the gene for gfp and figured out how to insert it into the dna of other cells . there , it acts like a biochemical beacon , marking genetic modifications , or revealing the path of critical molecules . scientists have used the glow of gfp to watch cancer cells proliferate , track the development of alzheimer 's , and illuminate countless other biological processes . developing the tools and techniques from gfp has netted three scientists a nobel prize in 2008 , and another three in 2014 . but it 's jellyfish who may be the most successful organisms on earth . ancient fossils prove that jellyfish have inhabited the seas for at least 500 million years , and maybe go back over 700 million . that 's longer than any other multiorgan animal . and as other marine animals are struggling to survive in warmer and more acidic oceans , the jellyfish are thriving , and perhaps getting even more numerous . it does n't hurt that some can lay as many as 45,000 eggs in a single night . and there 's some jellyfish whose survival strategy almost sounds like science fiction . when the immortal jellyfish is sick , aging , or under stress , its struggling cells can change their identity . the tiny bell and tentacles deteriorate and turn into an immature polyp that spawns brand new clones of the parent . as far as we know , these are the only animals who found a loophole when facing mortality . that 's pretty sophisticated for species that are 95 % water and predate the dinosaurs .

when they 're triggered by contact , they shoot with an explosive force . it exerts over 550 times the pressure of mike tyson 's strongest punch to inject venom into the victim . some jellyfish stings barely tingle , but others cause severe skin damage .

the explosive sting of some jellyfish exerts ____ times the pressure of mike tyson 's strongest punch .

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 .

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 .

australia has one of the highest rates of skin cancer in the world . why might this population be particularly susceptible ?

fish are in trouble . the cod population off canada 's east coast collapsed in the 1990s , intense recreational and commercial fishing has decimated goliath grouper populations in south florida , and most populations of tuna have plummeted by over 50 % , with the southern atlantic bluefin on the verge of extinction . those are just a couple of many examples . overfishing is happening all over the world . how did this happen ? when some people think of fishing , they imagine relaxing in a boat and patiently reeling in the day 's catch . but modern industrial fishing , the kind that stocks our grocery shelves , looks more like warfare . in fact , the technologies they employ were developed for war . radar , sonar , helicopters , and spotter planes are all used to guide factory ships towards dwindling schools of fish . long lines with hundreds of hooks or huge nets round up massive amounts of fish , along with other species , like seabirds , turtles , and dolphins . and fish are hauled up onto giant boats , complete with onboard flash freezing and processing facilities . all of these technologies have enabled us to catch fish at greater depths and farther out at sea than ever before . and as the distance and depth of fishing have expanded , so has the variety of species we target . for example , the patagonian toothfish neither sounds nor looks very appetizing . and fishermen ignored it until the late 1970s . then it was rebranded and marketed to chefs in the u.s. as chilean sea bass , despite the animal actually being a type of cod . soon it was popping up in markets all over the world and is now a delicacy . unfortunately , these deep water fish do n't reproduce until they 're at least ten years old , making them extremely vulnerable to overfishing when the young are caught before they 've had the chance to spawn . consumer taste and prices can also have harmful effects . for example , shark fin soup is considered such a delicacy in china and vietnam that the fin has become the most profitable part of the shark . this leads many fishermen to fill their boats with fins leaving millions of dead sharks behind . the problems are n't unique to toothfish and sharks . almost 31 % of the world 's fish populations are overfished , and another 58 % are fished at the maximum sustainable level . wild fish simply ca n't reproduce as fast as 7 billion people can eat them . fishing also has impacts on broader ecosystems . wild shrimp are typically caught by dragging nets the size of a football field along the ocean bottom , disrupting or destroying seafloor habitats . the catch is often as little as 5 % shrimp . the rest is by-catch , unwanted animals that are thrown back dead . and coastal shrimp farming is n't much better . mangroves are bulldozed to make room for shrimp farms , robbing coastal communities of storm protection and natural water filtration and depriving fish of key nursery habitats . so what does it look like to give fish a break and let them recover ? protection can take many forms . in national waters , governments can set limits about how , when , where , and how much fishing occurs , with restrictions on certain boats and equipment . harmful practices , such as bottom trawling , can be banned altogether , and we can establish marine reserves closed to all fishing to help ecosystems restore themselves . there 's also a role for consumer awareness and boycotts to reduce wasteful practices , like shark finning , and push fishing industries towards more sustainable practices . past interventions have successfully helped depleted fish populations recover . there are many solutions . the best approach for each fishery must be considered based on science , respect for the local communities that rely on the ocean , and for fish as wild animals . and then the rules must be enforced . international collaboration is often needed , too , because fish do n't care about our borders . we need to end overfishing . ecosystems , food security , jobs , economies , and coastal cultures all depend on it .

in national waters , governments can set limits about how , when , where , and how much fishing occurs , with restrictions on certain boats and equipment . harmful practices , such as bottom trawling , can be banned altogether , and we can establish marine reserves closed to all fishing to help ecosystems restore themselves . there 's also a role for consumer awareness and boycotts to reduce wasteful practices , like shark finning , and push fishing industries towards more sustainable practices .

bottom-trawling is a type of net fishing that has been compared to what ?

imagine something small enough to float on a particle of dust that holds the keys to understanding cancer , virology , and genetics . luckily for us , such a thing exists in the form of trillions upon trillions of human lab-grown cells called hela . let 's take a step back for a second . scientists grow human cells in the lab to study how they function , understand how diseases develop , and test new treatments without endangering patients . to make sure that they can repeat these experiments over and over , and compare the results with other scientists , they need huge populations of identical cells that can duplicate themselves faithfully for years , but until 1951 , all human cell lines that researchers tried to grow had died after a few days . then a john hopkins scientist named george gey received a sample of a strange looking tumor : dark purple , shiny , jelly-like . this sample was special . some of its cells just kept dividing , and dividing , and dividing . when individual cells died , generations of copies took their place and thrived . the result was an endless source of identical cells that 's still around today . the very first immortal human cell line . gey labeled it `` hela '' after the patient with the unusual tumor , henrietta lacks . born on a tobacco farm in virginia , she lived in baltimore with her husband and five children . she died of aggressive cervical cancer a few months after her tumorous cells were harvested , and she never knew about them . so what 's so special about the cells from henrietta lacks that lets them survive when other cell lines die ? the short answer is we do n't entirely know . normal human cells have built-in control mechanisms . they can divide about 50 times before they self destruct in a process called apoptosis . this prevents the propagation of genetic errors that creep in after repeated rounds of division . but cancer cells ignore these signals , dividing indefinitely and crowding out normal cells . still , most cell lines eventually die off , especially outside the human body . not hela , though , and that 's the part we ca n't yet explain . regardless , when dr. gey realized he had the first immortal line of human cells , he sent samples to labs all over the world . soon the world 's first cell production facility was churning out 6 trillion hela cells a week , and scientists put them to work in an ethically problematic way , building careers and fortunes off of henrietta 's cells without her or her family 's consent , or even knowledge until decades later . the polio epidemic was at its peak in the early 50s . hela cells , which easily took up and replicated the virus , allowed jonas salk to test his vaccine . they 've been used to study diseases , including measles , mumps , hiv , and ebola . we know that human cells have 46 chromosomes because a scientist working with hela discovered a chemcial that makes chromosomes visible . hela cells themselves actually have around 80 highly mutated chromosomes . hela cells were the first to be cloned . they 've traveled to outer space . telomerase , an enzyme that helps cancer cells evade destruction by repairing their dna , was discovered first in hela cells . in an interesting turn of fate , thanks to hela , we know that cervical cancer can be caused by a virus called hpv and now there 's a vaccine . hela-fueled discoveries have filled thousands of scientific papers , and that number is probably even higher than anyone knows . hela cells are so resilient that they can travel on almost any surface : a lab worker 's hand , a piece of dust , invading cultures of other cells and taking over like weeds , countless cures , patents and discoveries all made thanks to henrieta lacks .

they 've traveled to outer space . telomerase , an enzyme that helps cancer cells evade destruction by repairing their dna , was discovered first in hela cells . in an interesting turn of fate , thanks to hela , we know that cervical cancer can be caused by a virus called hpv and now there 's a vaccine . hela-fueled discoveries have filled thousands of scientific papers , and that number is probably even higher than anyone knows .

research with hela cells lead to a vaccine for _____ , which likely caused henrietta ’ s cancer .

we 've decided to make a new video about aluminium because it 's a long time over five years since we made the first one and ... we did n't say very much . aluminium is a surprisingly abundand element . if you look at this periodic table here , where the area of the different elements gives you a rough idea of the abundance you can see that aluminium is one of the most abundant metals up there with sodium , magnesium and calcium . more aluminum than potassium ; about the same or perhaps even more than iron . we 're never going to run out of aluminium . the problem with aluminium is that you do n't find aluminium metal in nature as a metal . it 's always tied up with other compounds ; mostly with oxygen , in clays . you know what clays are , the sort of muddy stuff that you get stuck on your shoes when it 's raining . to get the aluminium out of the clay , that is , to break the aluminium/oxygen bonds , which are very strong ; requires a lot of energy , which comes from electricity . so , making aluminium is very energy intensive . that 's why people like to recycle aluminium because once you 've got it , it 's worth preserving ; but it 's fantastically important because aluminium is a very light metal . and it 's often used as an alloy because the aluminium alloys are stronger than the aluminium itself , so , if you 're using it for aircraft or some other use like that where you want to combine lightness with strength then the stronger you can make it , the better . but when it was first made , in the 19th century , isolated as a metal it was terrifically valuable and there are stories of the french emperor serving his honored guests with aluminium plates or aluminium cutlery while the less important people had silver or gold ; but those times have passed and now you can get cupcakes and things like that surrounded by foil of aluminium . aluminium is a very good metal for making things because it has a very thin coating of aluminium oxide on the surface which prevents it [ from ] reacting with things . but as soon as that coating goes it becomes very reactive . alfred worden : hadley base , do you read houston ? david scott : yeah . now , 5 by , joe . worden : okay . worden : and i guess we 're standing by for your high-gain alignment per the checklist . scott : okay , stand by . you may have seen our video where we put copper chloride in one of these cupcake holders ... [ first of all i 'm going to dissolve some up and make a fairly concentrated solution . i 'm going to place this here . ] ... and what came out was this , or rather the copper chloride came out through the hole . [ it starts boiling really quite nicely . now , imagine i was doing this for my children who were quite small at that time , and ... voosh ! ] and the aluminium was completely dissolved up forming aluminium chloride and copper metal . in my own research , aluminium is quite important ; quite a lot of our equipment uses aluminium . not so much for the high pressure tubing that we use because quite a lot of my reaserch involves high pressures but we use it for the metal blocks that we put round the tubing so that we can heat it up . aluminium has a good electrical conductivity , and it 's also easy to machine . this is a piece of equipment here where we have a tube going down the middle . you can see the diameter of the tube here . around it is an aluminium block and an electrical heater . now , this particular case there was an accident , or a mishap , because the thermocouple that was controlling the temperature of this fell out . so , the heater got hotter and hotter , and eventually , the aluminium melted and poured down here . and i think this is really beautiful . well , fortunately , i was not in the lab or i would 've got very angry with my students but i think when it happened it was quite exciting ; this would have been glowing almost red because the melting point of aluminium is around 500 degrees centigrade . but then once it formed originally it was very shiny but quickly , it again developed the surface layer of aluminium oxide . if you have fine particles of aluminium and blow them into a flame ... ... then they will burn quite spectacularly and you form aluminium oxide . now , on the face of it , aluminium oxide sounds a rather boring compound but it 's really very useful and we use it quite a lot in our research in all sorts of different ways . it looks like a white powder . not very exciting . but in our group this aluminium oxide has been a fantastic catalyst all sorts of reactions that we did n't expect have gone with this material . my students keep it in a bottle almost like a magic catalyst and i 've only been given a little to show you . it acts as a solid acid which can be used at very high temperature and will get various acid-catalyzed reactions of organic compounds . it will make ethers , we have made various alkynes and a whole series of different compounds and my students still use it very much . if you melt the aluminium oxide , which we ca n't do here but can be done industrially , you can make single crystals which are transparent like glass and then you can grow a single crystal tube , like this one , which because it 's a single crystal , it 's terrifically strong . it 's the defects that make something weak and so if you have just one crystal there are no defects and so it 's very strong . so you can put a very high pressure inside this tube without it blowing up . brady : but you could make that tube out of metal , professor . professor : but , if you have a metal then you ca n't see what 's going on inside , and we 're using these tubes for photochemical reactions . so , we take a light like this , and shine it on the chemicals going through the tube under high pressure and we can convert one chemical into another . we can do this very efficiently because the light is absorbed by the molecules that we want to react and so we dont waste the energy on everything else . and using leds , which are a very efficient light source , you can get a process that is very energy efficient and it all depends on having this sapphire tube . this is synthetic sapphire . the real sapphire , the gems , have impurities in them , of other metals , which give them the nice colors , particularly the blue . princess kate has a blue sapphire ring which belonged to her husband 's mother , princess di , before her . and so , these are very valuable ones . but synthetic sapphire is also expensive but not in the same class as a natural gem . brady : what can nature do that the guys at the sapphire factory ca n't do ? professor : nature has time . the people who grow this will take hours or days or perhaps weeks to grow it . nature can spend thousands or millions of years growing a particular gem and therefore they can heat it up and cool it down in natural surroundings , in volcanoes ... or whatever far more slowly than people can afford to do industrially . there 's a lot of argument whether you should call it aluminum or aluminium now , there is n't a totally correct one because both forms are acceptable . but , all or nearly all chemists use aluminium because it 's very important to use a standardized nomenclature right across the world . and i think aluminium sounds nicer . student : hi professor , my question is is it aluminum or aluminium ? 'cause i want to know what to call my aluminium model . apparantly , there was a decision in 1990 by iupac the international union of pure and applied chemistry that it should definately be called a l u m i n i u m but then they relented three years later and said you could use aluminum as well . but if you 're a serious chemist you really need to say aluminium , because otherwise people wo n't find your papers , your publications , when they search because they 'll almost certainly put an `` i '' ' in the name . aluminium is frequently used or used [ to be ] frequently used kkfor sauce pans , for cooking in because it 's easy to make , easy to machine and particularly when people used electric stoves it was easy to make a flat bottom so that you got good contact between the electric element and the sauce pan . the problem with aluminium sauce pans is that if you 're cooking some fairly acidic food , for example boiling lemons or rhubarb something like that which is quite acidic you can dissolve some of the aluminium and people got quite worried about getting aluminium in their food . also , if you cook red cabbage , which is an indicator ; blue for alkali , red for acid , then if you boil it in an aluminium sauce pan it goes blue . and earlier in my carreer i used a red cabbage together with a white one to make a union jack , a u.k. flag with a mixture of red and blue-red cabbage and the white from the white cabbage . unfortionately , i 've lost the photo ; brady is very cross with me . but it was quite fun cooking it in the kitchen . i did it once myself , but it was such a lot of work that the second time a got one of my students to do it .

we 've decided to make a new video about aluminium because it 's a long time over five years since we made the first one and ... we did n't say very much . aluminium is a surprisingly abundand element . if you look at this periodic table here , where the area of the different elements gives you a rough idea of the abundance you can see that aluminium is one of the most abundant metals up there with sodium , magnesium and calcium .

if you reverse the letters in the symbol al , you get the symbol of another element , la . interestingly , the symbols of the elements immediately below al in group 13 can also be reversed to give another element , for example ga/ag . how many similar pairs of elements can you find in the periodic table ?

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 .

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 .

what can you repeat to help you remember the formula for logarithms ?

lovely ! i ’ ve just realised that erbium is the most crucial element for the internet of all the elements on the periodic table , and so i want to take you across to materials engineering where we can see a demonstration which will explain to you why it ’ s so important , and why without erbium many of you couldn ’ t be watching this video . erbium is another lanthanide metal . it ’ s soft , silvery , quite malleable , very reactive towards oxygen and water and , i suppose , for us right now it ’ s quite significant , because it was originally discovered from a mineral which was found in this quarry . so we ’ re in a quarry in sweden near stockholm , called ytterby mine and some black minerals that were found in this quarry actually were the birthplace for four new chemical elements and erbium was one of them . erbium is a photographic filter and it is actually a nuclear poison . what that means is that it will kill dead any nuclear fission process so it ’ s obviously got some applications there . it ’ s an interesting element when you make compounds of it and dissolve it in solution it often goes pink . now this is some erbium trichloride . you ’ ll notice it ’ s very slightly pink . i think this is one of the ones that , because of its pink colourations , get ’ s used in jewellery and things like sunglasses and things like that , if memory serves . more recently erbium is used as an amplifier of light as it ’ s transmitted down optical fibres . so , the reason we are here , and why i ’ m all dressed up , these are the fibres that transmit the signals for the internet . now the reason they use fibres is because copper cables which you would normally use for electrical signals can not carry nearly as much information , as many youtube viewings at once , as one of these fibres . and the fibre is very strong , neither brady nor i have managed to break it , and the problem is that even with this fibre , with the light beam going down it , eventually the light gets weaker and weaker and you lose the signal . so every 50km , every 30 miles or so , down the fibre when it ’ s under the sea you have to amplify the signal to get it back up again so that our youtube video can reach the other side of the atlantic or to india or wherever . and so the way you ’ ve got to do it you ’ ve got to somehow amplify the light , make it more intense , and you can do this with erbium because if you put erbium into the glass then if you shine a light onto the erbium atoms they get excited and then as the light comes in from the signal it interacts with the erbium atom and the erbium atom loses its energy and gives out more light . so essentially the light comes in and comes out twice as intense . it then keeps going another 30 miles and you repeat it . here we ’ ve got the infrared laser , i used to work with lasers , but i ’ ve rather given up now . so it ’ s quite nostalgic . is it switched on ? and if you put this in the laser beam you can see there ’ s a special screen here , which will actually take an infrared laser beam which you can ’ t see and make it into visible light so you can see it . we ’ ve got infrared light going into a piece of glass with erbium in it . now , what is happening here is the physics here is slightly different from what happens in the amplifier , but is really quite fun because the light beam that you can ’ t see is suddenly being changed into visible light , to green light , which you can . yes it ’ s very important , i had heard about it in lectures but when we videoed our first video about erbium i had completely forgotten about this , although without it nobody would have seen any of our videos . welders , people that join pieces of metal together using either large electric fields or extreme temperatures have special masks to protect their eyes from the very bright light which is given out in the welding process . welding goggles typically can include erbium salts because they are intense and they absorb a massive amount of the light so the eyes of the welder are not damaged at all . so , under the sea you have these fibres with copper wires going next to it carrying the currents for the diodes that excite the amplifiers all the way along and , apparently , the current going down these wires is quite attractive to sharks and so in shallow water sharks come along and see the cable and it seems attractive and they start chewing it and , although brady and i can ’ t break the fibres , a shark in full spate can easily cut through it and so there have been quite alot of problems with the optic fibres in shallow water being chewed to bits by sharks .

and the fibre is very strong , neither brady nor i have managed to break it , and the problem is that even with this fibre , with the light beam going down it , eventually the light gets weaker and weaker and you lose the signal . so every 50km , every 30 miles or so , down the fibre when it ’ s under the sea you have to amplify the signal to get it back up again so that our youtube video can reach the other side of the atlantic or to india or wherever . and so the way you ’ ve got to do it you ’ ve got to somehow amplify the light , make it more intense , and you can do this with erbium because if you put erbium into the glass then if you shine a light onto the erbium atoms they get excited and then as the light comes in from the signal it interacts with the erbium atom and the erbium atom loses its energy and gives out more light .

as the professor explained in the final minute of the video , who are the big enemies of the internet fibers under the sea ?

so californium is another element which was first prepared at the berkeley labs in california . it ’ s got quite a few military applications , usually involving the word ‘ nuclear ’ . but what most people don ’ t realise is it ’ s actually used in various types of machines for detecting metal fatigue and stress in airplanes , so obviously it ’ s pretty important our planes don ’ t fall to bits in mid-air and they are used in the kind of instruments which scan for this and can spot any problems long before they become a serious issue . it ’ s also probably the only other actinide which has possibly routinely got its way into households which is that it ’ s also used in metal detectors .

so californium is another element which was first prepared at the berkeley labs in california . it ’ s got quite a few military applications , usually involving the word ‘ nuclear ’ .

in which us city was californium first made ?

what do silk , dna , wood , balloons , and silly putty all have in common ? they 're polymers . polymers are such a big part of our lives that it 's virtually impossible to imagine a world without them , but what the heck are they ? polymers are large molecules made of small units called monomers linked together like the railroad cars from a train . poly means many , and mono means one , and mers or mero means parts . many polymers are made by repeating the same small monomer over and over again while others are made from two monomers linked in a pattern . all living things are made of polymers . some of the organic molecules in organisms are small and simple , having only one of a few functional groups . others , especially those that play structural roles or store genetic information , are macromolecules . in many cases , these macromolecules are polymers . for example , complex carbohydrates are polymers of simple sugars , proteins are polymers of amino acids , and nucleic acids , dna and rna , which contain our genetic information , are polymers of nucleotides . trees and plants are made of the polymer cellulose . it 's the tough stuff you find in bark and stems . feathers , fur , hair , and fingernails are made up of the protein keratin , also a polymer . it does n't stop there . did you know that the exoskeletons of the largest phylum in the animal kingdom , the arthropods , are made of the polymer chitin ? polymers also form the basis for synthetic fibers , rubbers , and plastics . all synthetic polymers are derived from petroleum oil and manufactured through chemical reactions . the two most common types of reactions used to make polymers are addition reactions and condensation reactions . in addition reactions , monomers simply add together to form the polymer . the process starts with a free radical , a species with an unpaired electron . the free radical attacks and breaks the bonds to form new bonds . this process repeats over and over to create a long-chained polymer . in condensation reactions , a small molecule , such as water , is produced with each chain-extending reaction . the first synthetic polymers were created by accident as by-products of various chemical reactions . thinking they were useless , chemists mostly discarded them . finally , one named leo baekeland decided maybe his useless by-product was n't so useless after all . his work resulted in a plastic that could be permanently squished into a shape using pressure and high temperatures . since the name of this plastic , polyoxybenzylmethylenglycolanhydride , was n't very catchy , advertisers called it bakelite . bakelite was made into telephones , children 's toys , and insulators for electrical devices . with its development in 1907 , the plastics industry exploded . one other familiar polymer , silly putty , was also invented by accident . during world war ii , the united states was in desperate need of synthetic rubber to support the military . a team of chemists at general electric attempted to create one but ended up with a gooey , soft putty . it was n't a good rubber substitute , but it did have one strange quality : it appeared to be extremely bouncy . silly putty was born ! synthetic polymers have changed the world . think about it . could you imagine getting through a single day without using plastic ? but polymers are n't all good . styrofoam , for example , is made mainly of styrene , which has been identified as a possible carcinogen by the environmental protection agency . as styrofoam products are being made , or as they slowly deteriorate in landfills or the ocean , they can release toxic styrene into the environment . in addition , plastics that are created by addition polymerization reactions , like styrofoam , plastic bags , and pvc , are built to be durable and food-safe , but that means that they do n't break down in the environment . millions of tons of plastics are dumped into landfills every year . this plastic does n't biodegrade , it just breaks down into smaller and smaller pieces , affecting marine life and eventually making their way back to humans . polymers can be soft or hard , squishy or solid , fragile or strong . the huge variation between means they can form an incredibly diverse array of substances , from dna to nylon stockings . polymers are so useful that we 've grown to depend on them every day . but some are littering our oceans , cities , and waterways with effects on our health that we 're only beginning to understand .

what do silk , dna , wood , balloons , and silly putty all have in common ? they 're polymers . polymers are such a big part of our lives that it 's virtually impossible to imagine a world without them , but what the heck are they ?

why do different polymers have different properties ?

in 1985 , 16-year-old douglas casa , ran the championship 10,000 meter track race at the empire state games . suddenly , with just 200 meters to go , he collapsed , got back up and then collapsed again on the final straightaway , with his body temperature at dangerous levels . he had suffered an exertional heat stroke . fortunately , with immediate and proper treatment , he survived the potentially fatal episode and has since helped save 167 people in similar circumstances . from ancient soldiers on the battlefield to modern day warriors on the gridiron , exertional heat stroke , or sunstroke , has long been a serious concern . and unlike classical heat stroke , which affects vulnerable people such as infants and the elderly during heat waves , exertional heat stroke is caused by intense exercise in the heat , and is one of the top three killers of athletes and soldiers in training . when you exercise , nearly 80 % of the energy you use is transformed into heat . in normal circumstances , this is what 's known as compensable heat stress . and your body can dissipate the heat as quickly as it 's generated through cooling methods like the evaporation of sweat . but with uncompensable heat stress , your body is unable to lose enough heat due to overexertion or high temperatures in humidity , which raises your core temperature beyond normal levels . this causes the proteins and cell membranes to denature , creating cells that no longer function properly and begin to leak their contents . if these leaky cells proliferate through the body , the results can be devastating . including liver damage , blood clot formation in the kidneys , damage to the gastrointestinal tract and even the failure of vital organs . so how do you diagnose an exertional heat stroke ? the main criterion is a core body temperature greater than 40 degrees celsius observed along with physical symptoms such as increased heart rate , low blood pressure and rapid breathing or signs of central nervous system disfunction such as confused behavior , aggression or loss of consciousness . the most feasible and accurate way to assess core body temperature is with a rectal thermometer as other common temperature-taking methods are not accurate in these circumstances . as far as treatment goes , the most important thing to remember is cool first , transport second . because the human body can withstand a core temperature above 40 degrees celsius for about 30 minutes before cell damage sets in , it 's essential to initiate rapid cooling on site in order to lower it as quickly as possible . after any athletic or protective gear has been removed from the victim , place them in an ice water tub while stirring the water and monitoring vitals continuously . if this is not possible , dousing in ice water and applying wet towels over the entire body can help . but before you start anything , emergency services should be called . as you wait , it 's important to keep the victim calm while cooling as much surface area as possible until emergency personnel arrive . if medical staff are available on site , cooling should continue until a core temperature of 38.9 degrees celsius is reached . the sun is known for giving life , but it can also take life away if we 're not careful , even affecting the strongest among us . as dr. jj levick wrote of exertional heat stroke in 1859 , `` it strikes down its victim with his full armor on . youth , health and strength oppose no obstacle to its power . '' but although this condition is one of the top three leading causes of death in sports , it has been 100 % survivable with proper care .

suddenly , with just 200 meters to go , he collapsed , got back up and then collapsed again on the final straightaway , with his body temperature at dangerous levels . he had suffered an exertional heat stroke . fortunately , with immediate and proper treatment , he survived the potentially fatal episode and has since helped save 167 people in similar circumstances .

what are some common situations where exertional heat stroke might occur ?

many people in the united states and latin america have grown up celebrating the anniversary of christopher columbus 's voyage , but was he an intrepid explorer who brought two worlds together or a ruthless exploiter who brought colonialism and slavery ? and did he even discover america at all ? it 's time to put columbus on the stand in history vs. christopher columbus . `` order , order in the court . wait , am i even supposed to be at work today ? '' cough `` yes , your honor . from 1792 , columbus day was celebrated in many parts of the united states on october 12th , the actual anniversary date . but although it was declared an official holiday in 1934 , individual states are n't required to observe it . only 23 states close public services , and more states are moving away from it completely . '' cough `` what a pity . in the 70s , we even moved it to the second monday in october so people could get a nice three-day weekend , but i guess you folks just hate celebrations . '' `` uh , what are we celebrating again ? '' `` come on , your honor , we all learned it in school . christopher columbus convinced the king of spain to send him on a mission to find a better trade route to india , not by going east over land but sailing west around the globe . everyone said it was crazy because they still thought the world was flat , but he knew better . and when in 1492 he sailed the ocean blue , he found something better than india : a whole new continent . '' `` what rubbish . first of all , educated people knew the world was round since aristotle . secondly , columbus did n't discover anything . there were already people living here for millennia . and he was n't even the first european to visit . the norse had settled newfoundland almost 500 years before . '' `` you do n't say , so how come we 're not all wearing those cow helmets ? '' `` actually , they did n't really wear those either . '' cough `` who cares what some vikings did way back when ? those settlements did n't last , but columbus 's did . and the news he brought back to europe spread far and wide , inspiring all the explorers and settlers who came after . without him , none of us would be here today . '' `` and because of him , millions of native americans are n't here today . do you know what columbus did in the colonies he founded ? he took the very first natives he met prisoner and wrote in his journal about how easily he could conquer and enslave all of them . '' `` oh , come on . everyone was fighting each other back then . did n't the natives even tell columbus about other tribes raiding and taking captives ? '' `` yes , but tribal warfare was sporadic and limited . it certainly did n't wipe out 90 % of the population . '' `` hmm . why is celebrating this columbus so important to you , anyway ? '' `` your honor , columbus 's voyage was an inspiration to struggling people all across europe , symbolizing freedom and new beginnings . and his discovery gave our grandparents and great-grandparents the chance to come here and build better lives for their children . do n't we deserve a hero to remind everyone that our country was build on the struggles of immigrants ? '' `` and what about the struggles of native americans who were nearly wiped out and forced into reservations and whose descendants still suffer from poverty and discrimination ? how can you make a hero out of a man who caused so much suffering ? '' `` that 's history . you ca n't judge a guy in the 15th century by modern standards . people back then even thought spreading christianity and civilization across the world was a moral duty . '' `` actually , he was pretty bad , even by old standards . while governing hispaniola , he tortured and mutilated natives who did n't bring him enough gold and sold girls as young as nine into sexual slavery , and he was brutal even to the other colonists he ruled , to the point that he was removed from power and thrown in jail . when the missionary , bartolomé de las casas , visited the island , he wrote , 'from 1494 to 1508 , over 3,000,000 people had perished from war , slavery and the mines . who in future generations will believe this ? ' '' `` well , i 'm not sure i believe those numbers . '' `` say , are n't there other ways the holiday is celebrated ? '' `` in some latin american countries , they celebrate the same date under different names , such as día de la raza . in these places , it 's more a celebration of the native and mixed cultures that survived through the colonial period . some places in the u.s. have also renamed the holiday , as native american day or indigenous people 's day and changed the celebrations accordingly . '' `` so , why not just change the name if it 's such a problem ? '' `` because it 's tradition . ordinary people need their heroes and their founding myths . ca n't we just keep celebrating the way we 've been doing for a century , without having to delve into all this serious research ? it 's not like anyone is actually celebrating genocide . '' `` traditions change , and the way we choose to keep them alive says a lot about our values . '' `` well , it looks like giving tired judges a day off is n't one of those values , anyway . '' traditions and holidays are important to all cultures , but a hero in one era may become a villain in the next as our historical knowledge expands and our values evolve . and deciding what these traditions should mean today is a major part of putting history on trial .

`` say , are n't there other ways the holiday is celebrated ? '' `` in some latin american countries , they celebrate the same date under different names , such as día de la raza . in these places , it 's more a celebration of the native and mixed cultures that survived through the colonial period .

what do some latin american countries celebrate on holidays like día de la raza ?

translator : andrea mcdonough reviewer : bedirhan cinar fourth and nineteen , folks , they 've got ta have a play as time 's ticking away because they 've got to stay in this ball game , they 've got to win . they come out lined up in the empty set , three receivers to the right , two to the left . defense looks like they 're gon na to man up with no safety . this is the exact offensive match-up that they want : the best receiver lined up against the linebacker . quarterback steps back to receive the ball , five yards deep in the gun . he takes a snap , drops three steps , he plants his back foot , he 's looking for an opening . there 's a blitz coming off the edge ! he steps up to avoid the rush . he 's looking down field . he 's got the inside receiver making a cut . he 's got a step on the linebacker . quarterback has a beat on it . he lets the ball go , it 's in the air ! receiver is out in front of the defender . he 's got it beat ! he 's out in front , racing for the ball ! it 's coming down ! he cradles it at the fifteen ! he 's at the ten , five ! touchdown ! unbelievable play ! now , wait a minute . of course , it 's believable , it 's physics , specifically the differences between scalars and vectors . so , let 's just see that replay . `` quarterback steps back to receive the ball , five yards deep in the gun . '' stop . see , measurements are defined as two different quantities . scalars are measurements with only numbers , and vectors are measurements with direction . for example , when that quarterback takes the snap , he 's five yards away , but from where ? back from the line of scrimmage , so the five yards by itself is a scalar quantity . when you add a direction , like five yards deep , it becomes a vector quantity . five yards - scalar , five yards deep - vector . ok , go ahead . `` he takes a snap , drops three steps . he plants his back foot , he 's looking for an opening . there 's a blitz coming off the edge ! he steps up to avoid the rush . '' whoa ! here 's a difference between distance and displacement . distance is a measurement without identifying where you moved . it 's a scalar quantity . when the quarterback makes a three-step drop , he moves about three yards back . when he moves about another three yards forward , when he steps up into the pocket , so that quarterback moves a total distance of six yards . that 's a distance , that 's a scalar . now , displacement is a vector quantity , describing about how far out of place the object is . so the quarterback dropped back three yards and then moved back forward three yards , he 's in the exact same place where he started . so , his displacement is zero yards . distance - six yards , displacement - zero yards . so , let 's look at what happened next . `` quarterback has a beat on it , he let 's the ball go ! it 's in the air ! receiver is out in front of the defender . '' stop . so , here 's speed and velocity , but let 's just do one thing at a time . so , speed is measurement without direction , it 's a scalar quantity . velocity is a vector quantity . it is that object 's speed , but with a direction of motion . so the receiver accelerates away , gaining both speed and distance . this takes the receiver 5 seconds to run those 50 yards . so his average speed , in any given time , is 10 yards/second . the linebacker tries to keep up , but his overall speed is slower , he only goes 35 yards in those 5 seconds , so his average speed is only 7 yards/second . they 're both traveling in a forward direction , so their velocity is also positive . you ca n't go from resting to your peak speed immediately . you 've got to build up to it . this is acceleration . at first the linebacker can keep up with that receiver , but eventually the faster receiver pulls away . that 's acceleration , the change in speed over time . acceleration is a vector quantity . it describes a rate at which an object changes velocity . like velocity , acceleration is a vector . it happens in a direction . so let 's just look at that play just one more time . `` quarterback steps back to receive the ball , five yards deep in the gun . '' vector ! `` he takes a snap , drops three steps , he plants his back foot . he 's looking for an opening . there 's a blitz coming off the edge ! he steps up to avoid the rush . '' displacement ! `` he 's got the inside receiver making a cut . he 's got a step on the linebacker . the quarterback has a beat on it . he let 's the ball go ! it 's in the air ! receiver is out in front of the defender ! '' velocity ! `` he 's got it beat ! he 's out in front , racing for the ball ! it 's coming down ! he cradles it at the fifteen , he 's at the ten , five ! '' acceleration ! `` touchdown ! unbelievable play ! that was a great play as time expired , resulting in the touchdown and ultimately the win and pure effort . '' and pure science .

at first the linebacker can keep up with that receiver , but eventually the faster receiver pulls away . that 's acceleration , the change in speed over time . acceleration is a vector quantity .

what type of line is always found on a graph of accelerating speed ?

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 .

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 .

the rich diversity of life found in the redwood crowns included :

this just in : `` thief robs town with world 's largest chocolate bunny . '' wait , so are we talking about this , or this ? that 's a classic case of a misplaced modifier , a common grammatical mistake that can dramatically change the meaning of a sentence . and lest you think this is a bit far-fetched , confusing headlines like this appear all the time . modifiers are words , phrases , and clauses that add information about other parts of a sentence , which is usually helpful . but when modifiers are n't linked clearly enough to the words they 're actually referring to , they can create unintentional ambiguity . that happens because the modifying words , in this case , `` with world 's largest chocolate bunny , '' modify the wrong thing , the robber 's actions instead of the town . to correct this particular sentence , we simply rephrase to make it clearer what the modifying phrase is talking about . `` town with world 's largest chocolate bunny robbed by thief . '' now , at least it 's clear that the thief was n't armed with a giant chocolate animal . sometimes , modifying words , phrases , or clauses do n't appear to be modifying anything at all . that 's called a dangling modifier . `` having robbed the bank in record time , it was possible to make off with the town 's chocolate rabbit as well . '' the modifying phrase in this sentence seems unrelated to anything else , and so we 're clueless about who the chocolate-loving criminal could possibly be . giving the modifier something to modify will solve the problem . then there 's another group called the squinting modifiers because they 're stuck between two things and could feasibly refer to either . often , these modifiers are adverbs , like the one in this sentence : `` robbers who steal chocolate bunnies rapidly attract the outrage of onlookers . '' `` rapidly '' is the modifier , here , but what 's not clear is whether it 's referring to the speed of the chocolate thievery , or how quickly it alerts the furious onlookers . to clarify , we can either put the modifier closer to its intended phrase , which works in some cases , or we can entirely reword the sentence so that the modifier no longer squints , but clearly applies to only one part . `` chocolate bunny-thieving robbers rapidly attract the outrage of onlookers . '' justice will eventually come to the chocolate thief , but in the meantime , our task is to avoid verbal ambiguity by making it clear which parts of the sentences modifiers belong to . that way , we can at least maintain grammatical law and order .

giving the modifier something to modify will solve the problem . then there 's another group called the squinting modifiers because they 're stuck between two things and could feasibly refer to either . often , these modifiers are adverbs , like the one in this sentence : `` robbers who steal chocolate bunnies rapidly attract the outrage of onlookers . '' `` rapidly '' is the modifier , here , but what 's not clear is whether it 's referring to the speed of the chocolate thievery , or how quickly it alerts the furious onlookers .

'squinting ' modifiers most often take the form of :

let 's say you 're on a game show . you 've already earned $ 1000 in the first round when you land on the bonus space . now , you have a choice . you can either take a $ 500 bonus guaranteed or you can flip a coin . if it 's heads , you win $ 1000 bonus . if it 's tails , you get no bonus at all . in the second round , you 've earned $ 2000 when you land on the penalty space . now you have another choice . you can either take a $ 500 loss , or try your luck at the coin flip . if it 's heads , you lose nothing , but if it 's tails , you lose $ 1000 instead . if you 're like most people , you probably chose to take the guaranteed bonus in the first round and flip the coin in the second round . but if you think about it , this makes no sense . the odds and outcomes in both rounds are exactly the same . so why does the second round seem much scarier ? the answer lies in a phenomenon known as loss aversion . under rational economic theory , our decisions should follow a simple mathematical equation that weighs the level of risk against the amount at stake . but studies have found that for many people , the negative psychological impact we feel from losing something is about twice as strong as the positive impact of gaining the same thing . loss aversion is one cognitive bias that arises from heuristics , problem-solving approaches based on previous experience and intuition rather than careful analysis . and these mental shortcuts can lead to irrational decisions , not like falling in love or bungee jumping off a cliff , but logical fallacies that can easily be proven wrong . situations involving probability are notoriously bad for applying heuristics . for instance , say you were to roll a die with four green faces and two red faces twenty times . you can choose one of the following sequences of rolls , and if it shows up , you 'll win $ 25 . which would you pick ? in one study , 65 % of the participants who were all college students chose sequence b even though a is shorter and contained within b , in other words , more likely . this is what 's called a conjunction fallacy . here , we expect to see more green rolls , so our brains can trick us into picking the less likely option . heuristics are also terrible at dealing with numbers in general . in one example , students were split into two groups . the first group was asked whether mahatma gandhi died before or after age 9 , while the second was asked whether he died before or after age 140 . both numbers were obviously way off , but when the students were then asked to guess the actual age at which he died , the first group 's answers averaged to 50 while the second group 's averaged to 67 . even though the clearly wrong information in the initial questions should have been irrelevant , it still affected the students ' estimates . this is an example of the anchoring effect , and it 's often used in marketing and negotiations to raise the prices that people are willing to pay . so , if heuristics lead to all these wrong decisions , why do we even have them ? well , because they can be quite effective . for most of human history , survival depended on making quick decisions with limited information . when there 's no time to logically analyze all the possibilities , heuristics can sometimes save our lives . but today 's environment requires far more complex decision-making , and these decisions are more biased by unconscious factors than we think , affecting everything from health and education to finance and criminal justice . we ca n't just shut off our brain 's heuristics , but we can learn to be aware of them . when you come to a situation involving numbers , probability , or multiple details , pause for a second and consider that the intuitive answer might not be the right one after all .

let 's say you 're on a game show . you 've already earned $ 1000 in the first round when you land on the bonus space .

what is a heuristic ?

your favorite band is great at playing music , but not so great at being organized . they keep misplacing their instruments on tour , and it 's driving their manager mad . on the day of the big concert , the band wakes up to find themselves tied up in a windowless , soundproof practice room . their manager explains what 's happening . outside , there are ten large boxes . each contains one of your instruments , but do n't be fooled by the pictures - they 've been randomly placed . i 'm going to let you out one at a time . while you 're outside , you can look inside any five boxes before security takes you back to the tour bus . you ca n't touch the instruments or in any way communicate what you find to the others . no marking the boxes , shouting , nothing . if each one of you can find your own instrument , then you can play tonight . otherwise , the label is dropping you . you have three minutes to think about it before we start . the band is in despair . after all , each musician only has a 50 % chance of finding their instrument by picking five random boxes . and the chances that all ten will succeed are even lower - just 1 in 1024 . but suddenly , the drummer comes up with a valid strategy that has a better than 35 % chance of working . can you figure out what it was ? pause the video on the next screen if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 here 's what the drummer said : everyone first open the box with the picture of your instrument . if your instrument is inside , you 're done . otherwise , look at whatever 's in there , and then open the box with that picture on it . keep going that way until you find your instrument . the bandmates are skeptical , but amazingly enough , they all find what they need . and a few hours later , they 're playing to thousands of adoring fans . so why did the drummer 's strategy work ? each musician follows a linked sequence that starts with the box whose outside matches their instrument and ends with the box actually containing it . note that if they kept going , that would lead them back to the start , so this is a loop . for example , if the boxes are arranged like so , the singer would open the first box to find the drums , go to the eighth box to find the bass , and find her microphone in the third box , which would point back to the first . this works much better than random guessing because by starting with the box with the picture of their instrument , each musician restricts their search to the loop that contains their instrument , and there are decent odds , about 35 % , that all of the loops will be of length five or less . how do we calculate those odds ? for the sake of simplicity , we 'll demonstrate with a simplified case , four instruments and no more than two guesses allowed for each musician . let 's start by finding the odds of failure , the chance that someone will need to open three or four boxes before they find their instrument . there are six distinct four-box loops . one fun way to count them is to make a square , put an instrument at each corner , and draw the diagonals . see how many unique loops you can find , and keep in mind that these two are considered the same , they just start at different points . these two , however , are different . we can visualize the eight distinct three-box loops using triangles . you 'll find four possible triangles depending on which instrument you leave out , and two distinct paths on each . so of the 24 possible combinations of boxes , there are 14 that lead to faliure , and ten that result in success . that computational strategy works for any even number of musicians , but if you want a shortcut , it generalizes to a handy equation . plug in ten musicians , and we get odds of about 35 % . what if there were 1,000 musicians ? 1,000,000 ? as n increases , the odds approach about 30 % . not a guarantee , but with a bit of musician 's luck , it 's far from hopeless . hi everybody , if you liked this riddle , try solving these two .

your favorite band is great at playing music , but not so great at being organized . they keep misplacing their instruments on tour , and it 's driving their manager mad .

can you suggest your own modification of the problem ?

translator : jennifer cody reviewer : jessica ruby when faced with a big challenge where potential failure seems to lurk at every corner , maybe you 've heard this advice before : `` be more confident . '' and most likely , this is what you think when you hear it : `` if only it were that simple . '' but what is confidence ? take the belief that you are valuable , worthwhile , and capable , also known as self-esteem , add in the optimism that comes when you are certain of your abilities , and then empowered by these , act courageously to face a challenge head-on . this is confidence . it turns thoughts into action . so where does confidence even come from ? there are several factors that impact confidence . one : what you 're born with , such as your genes , which will impact things like the balance of neurochemicals in your brain . two : how you 're treated . this includes the social pressures of your environment . and three : the part you have control over , the choices you make , the risks you take , and how you think about and respond to challenges and setbacks . it is n't possible to completely untangle these three factors , but the personal choices we make certainly play a major role in confidence development . so , by keeping in mind a few practical tips , we do actually have the power to cultivate our own confidence . tip 1 : a quick fix . there are a few tricks that can give you an immediate confidence boost in the short term . picture your success when you 're beginning a difficult task , something as simple as listening to music with deep bass ; it can promote feelings of power . you can even strike a powerful pose or give yourself a pep talk . tip two : believe in your ability to improve . if you 're looking for a long-term change , consider the way you think about your abilities and talents . do you think they are fixed at birth , or that they can be developed , like a muscle ? these beliefs matter because they can influence how you act when you 're faced with setbacks . if you have a fixed mindset , meaning that you think your talents are locked in place , you might give up , assuming you 've discovered something you 're not very good at . but if you have a growth mindset and think your abilities can improve , a challenge is an opportunity to learn and grow . neuroscience supports the growth mindset . the connections in your brain do get stronger and grow with study and practice . it also turns out , on average , people who have a growth mindset are more successful , getting better grades , and doing better in the face of challenges . tip three : practice failure . face it , you 're going to fail sometimes . everyone does . j.k. rowling was rejected by twelve different publishers before one picked up `` harry potter . '' the wright brothers built on history 's failed attempts at flight , including some of their own , before designing a successful airplane . studies show that those who fail regularly and keep trying anyway are better equipped to respond to challenges and setbacks in a constructive way . they learn how to try different strategies , ask others for advice , and perservere . so , think of a challenge you want to take on , realize it 's not going to be easy , accept that you 'll make mistakes , and be kind to yourself when you do . give yourself a pep talk , stand up , and go for it . the excitement you 'll feel knowing that whatever the result , you 'll have gained greater knowledge and understanding . this is confidence .

translator : jennifer cody reviewer : jessica ruby when faced with a big challenge where potential failure seems to lurk at every corner , maybe you 've heard this advice before : `` be more confident . '' and most likely , this is what you think when you hear it : `` if only it were that simple . ''

in what ways does feeling confident help a person succeed in their every day life ?

there 's a job out there with a great deal of power , pay , prestige , and near-perfect job security . and there 's only one way to be hired : get appointed to the us supreme court . if you want to become a justice on the supreme court , the highest federal court in the united states , three things have to happen . you have to be nominated by the president of the united states , your nomination needs to be approved by the senate , and finally , the president must formally appoint you to the court . because the constitution does n't specify any qualifications , in other words , that there 's no age , education , profession , or even native-born citizenship requirement , a president can nominate any individual to serve . so far , six justices have been foreign-born , at least one never graduated from high school , and another was only 32 years old when he joined the bench . most presidents nominate individuals who broadly share their ideological view , so a president with a liberal ideology will tend to appoint liberals to the court . of course , a justice 's leanings are not always so predictable . for example , when president eisenhower , a republican , nominated earl warren for chief justice , eisenhower expected him to make conservative decisions . instead , warren 's judgements have gone down as some of the most liberal in the court 's history . eisenhower later remarked on that appointment as `` the biggest damned-fool mistake '' he ever made . many other factors come up for consideration , as well , including experience , personal loyalties , ethnicity , and gender . the candidates are then thoroughly vetted down to their tax records and payments to domestic help . once the president interviews the candidate and makes a formal nomination announcement , the senate leadership traditionally turns the nomination over to hearings by the senate judiciary committee . depending on the contentiousness of the choice , that can stretch over many days . since the nixon administration , these hearings have averaged 60 days . the nominee is interviewed about their law record , if applicable , and where they stand on key issues to discern how they might vote . and especially in more recent history , the committee tries to unearth any dark secrets or past indiscretions . the judiciary committee votes to send the nomination to the full senate with a positive or negative recommendation , often reflective of political leanings , or no recommendation at all . most rejections have happened when the senate majority has been a different political party than the president . when the senate does approve , it 's by a simple majority vote , with ties broken by the vice president . with the senate 's consent , the president issues a written appointment , allowing the nominee to complete the final steps to take the constitutional and judicial oaths . in doing so , they solemnly swear to administer justice without respect to persons and do equal right to the poor and the rich and faithfully and impartially discharge and perform all the duties incumbent upon a us supreme court justice . this job is for life , barring resignation , retirement , or removal from the court by impeachment . and of the 112 justices who have held the position , not one has yet been removed from office as a result of an impeachment . one of their roles is to protect the fundamental rights of all americans , even as different parties take power . with the tremendous impact of this responsibility , it 's no wonder that a us supreme court justice is expected to be , in the words of irving r. kaufman , `` a paragon of virtue , an intellectual titan , and an administrative wizard . '' of course , not every member of the court turns out to be an exemplar of justice . each leaves behind a legacy of decisions and opinions to be debated and dissected by the ultimate judges , time and history .

and there 's only one way to be hired : get appointed to the us supreme court . if you want to become a justice on the supreme court , the highest federal court in the united states , three things have to happen . you have to be nominated by the president of the united states , your nomination needs to be approved by the senate , and finally , the president must formally appoint you to the court .

if you want to become a justice on the united states supreme court , you have to be :

in mythological ancient greece , soaring above crete on wings made from wax and feathers , icarus , the son of daedalus , defied the laws of both man and nature . ignoring the warnings of his father , he rose higher and higher . to witnesses on the ground , he looked like a god , and as he peered down from above , he felt like one , too . but , in mythological ancient greece , the line that separated god from man was absolute and the punishment for mortals who attempted to cross it was severe . such was the case for icarus and daedalus . years before icarus was born , his father daedalus was highly regarded as a genius inventor , craftsman , and sculptor in his homeland of athens . he invented carpentry and all the tools used for it . he designed the first bathhouse and the first dance floor . he made sculptures so lifelike that hercules mistook them for actual men . though skilled and celebrated , daedalus was egotistical and jealous . worried that his nephew was a more skillful craftsman , daedalus murdered him . as punishment , daedalus was banished from athens and made his way to crete . preceded by his storied reputation , daedalus was welcomed with open arms by crete 's king minos . there , acting as the palace technical advisor , daedalus continued to push the boundaries . for the king 's children , he made mechanically animated toys that seemed alive . he invented the ship 's sail and mast , which gave humans control over the wind . with every creation , daedalus challenged human limitations that had so far kept mortals separate from gods , until finally , he broke right through . king minos 's wife , pasiphaë , had been cursed by the god poseidon to fall in love with the king 's prized bull . under this spell , she asked daedalus to help her seduce it . with characteristic audacity , he agreed . daedalus constructed a hollow wooden cow so realistic that it fooled the bull . with pasiphaë hiding inside daedalus 's creation , she conceived and gave birth to the half-human half-bull minotaur . this , of course , enraged the king who blamed daedalus for enabling such a horrible perversion of natural law . as punishment , daedalus was forced to construct an inescapable labyrinth beneath the palace for the minotaur . when it was finished , minos then imprisoned daedalus and his only son icarus within the top of the tallest tower on the island where they were to remain for the rest of their lives . but daedalus was still a genius inventor . while observing the birds that circled his prison , the means for escape became clear . he and icarus would fly away from their prison as only birds or gods could do . using feathers from the flocks that perched on the tower , and the wax from candles , daedalus constructed two pairs of giant wings . as he strapped the wings to his son icarus , he gave a warning : flying too near the ocean would dampen the wings and make them too heavy to use . flying too near the sun , the heat would melt the wax and the wings would disintegrate . in either case , they surely would die . therefore , the key to their escape would be in keeping to the middle . with the instructions clear , both men leapt from the tower . they were the first mortals ever to fly . while daedalus stayed carefully to the midway course , icarus was overwhelmed with the ecstasy of flight and overcome with the feeling of divine power that came with it . daedalus could only watch in horror as icarus ascended higher and higher , powerless to change his son 's dire fate . when the heat from the sun melted the wax on his wings , icarus fell from the sky . just as daedalus had many times ignored the consequences of defying the natural laws of mortal men in the service of his ego , icarus was also carried away by his own hubris . in the end , both men paid for their departure from the path of moderation dearly , icarus with his life and daedalus with his regret .

just as daedalus had many times ignored the consequences of defying the natural laws of mortal men in the service of his ego , icarus was also carried away by his own hubris . in the end , both men paid for their departure from the path of moderation dearly , icarus with his life and daedalus with his regret .

veering from the “ path of moderation ” can be both good and bad . reflect on this thought and respond .

in 1796 , the scientist edward jenner injected material from a cowpox virus into an eight-year-old boy with a hunch that this would provide the protection needed to save people from deadly outbreaks of the related smallpox virus . it was a success . the eight-year-old was inoculated against the disease and this became the first ever vaccine . but why did it work ? to understand how vaccines function , we need to know how the immune system defends us against contagious diseases in the first place . when foreign microbes invade us , the immune system triggers a series of responses in an attempt to identify and remove them from our bodies . the signs that this immune response is working are the coughing , sneezing , inflammation and fever we experience , which work to trap , deter and rid the body of threatening things , like bacteria . these innate immune responses also trigger our second line of defense , called adaptive immunity . special cells called b cells and t cells are recruited to fight microbes , and also record information about them , creating a memory of what the invaders look like , and how best to fight them . this know-how becomes handy if the same pathogen invades the body again . but despite this smart response , there 's still a risk involved . the body takes time to learn how to respond to pathogens and to build up these defenses . and even then , if a body is too weak or young to fight back when it 's invaded , it might face very serious risk if the pathogen is particularly severe . but what if we could prepare the body 's immune response , readying it before someone even got ill ? this is where vaccines come in . using the same principles that the body uses to defend itself , scientists use vaccines to trigger the body 's adaptive immune system , without exposing humans to the full strength disease . this has resulted in many vaccines , which each work uniquely , separated into many different types . first , we have live attenuated vaccines . these are made of the pathogen itself but a much weaker and tamer version . next , we have inactive vaccines , in which the pathogens have been killed . the weakening and inactivation in both types of vaccine ensures that pathogens do n't develop into the full blown disease . but just like a disease , they trigger an immune response , teaching the body to recognize an attack by making a profile of pathogens in preparation . the downside is that live attenuated vaccines can be difficult to make , and because they 're live and quite powerful , people with weaker immune systems ca n't have them , while inactive vaccines do n't create long-lasting immunity . another type , the subunit vaccine , is only made from one part of the pathogen , called an antigen , the ingredient that actually triggers the immune response . by even further isolating specific components of antigens , like proteins or polysaccharides , these vaccines can prompt specific responses . scientists are now building a whole new range of vaccines called dna vaccines . for this variety , they isolate the very genes that make the specific antigens the body needs to trigger its immune response to specific pathogens . when injected into the human body , those genes instruct cells in the body to make the antigens . this causes a stronger immune response , and prepares the body for any future threats , and because the vaccine only includes specific genetic material , it does n't contain any other ingredients from the rest of the pathogen that could develop into the disease and harm the patient . if these vaccines become a success , we might be able to build more effective treatments for invasive pathogens in years to come . just like edward jenner 's amazing discovery spurred on modern medicine all those decades ago , continuing the development of vaccines might even allow us to treat diseases like hiv , malaria , or ebola , one day .

in 1796 , the scientist edward jenner injected material from a cowpox virus into an eight-year-old boy with a hunch that this would provide the protection needed to save people from deadly outbreaks of the related smallpox virus . it was a success .

why does inoculating with cowpox protect against smallpox but a standard flu vaccine can not protect against every flu strain ?

a lone priestess walks towards an underground chamber . people line the streets to watch as she proclaims her innocence . it does n't matter . she 's already been judged and found guilty . the sentence ? live burial . the underground chamber contains a portion of bread , water , milk , and oil . she will have a lamp , a bed , and a blanket , but she wo n't emerge alive . at the threshold , the priestess pauses , claims her innocence one last time , then enters the chamber never to be seen again by the roman people . the priestess is one of rome 's six vestal virgins , each carefully selected as children from rome 's most aristocratic families . but now with her death , there are only five , and a new priestess must be chosen . the six-year-old licinia witnessed the spectacle , never suspecting that a few days later , she 'd be chosen as the next vestal virgin . her age , her patrician family lineage , and her apparent good health makes her the best candidate to serve the goddess vesta in the eyes of the romans . her parents are proud that their daughter 's been chosen . licinia is afraid , but she has no choice in the matter . she must serve the goddess for at least the next 30 years . for the first ten years of licinia 's service , she 's considered in training , learning how to be a vestal virgin . her most important duty is keeping vigil over the flame of vesta , the virgin goddess of the hearth . vesta does n't have a statue like other roman gods and goddesses . instead , she 's represented by the flame which burns day and night in her temple located next to the forum in the center of the city . like all vestal priestesses , licinia spends part of each day on shift , watching and tending to the flame . the flame represents two things . the first is the continuation of rome as a power in the world . the romans believed that if the flame goes out , the city 's in danger . the flame also symbolizes the continuing virginity of vesta 's priestesses . for the romans , a vestal 's virginity signaled not only her castitas , or modest spirit and body , but also her ritual purity . so licinia knows she must never let the flame go out . her life , the lives of her fellow vestals , and the safety of rome itself depends upon it . licinia learns to collect water each day from a nearby fountain to cleanse the temple . she learns the fasti , the calendar of sacred rituals and she watches while the senior priestesses conduct sacrifices . by the time licinia completes her training , she 's 16 years old . licinia understands that the way she must act is a reflection of the goddess she serves . when it 's her turn to collect the water , she keeps her eyes lowered to the ground . when she performs sacrifices , she focuses intently on the task . licinia directs her energy towards being the best priestess she can be . she 's worried that someday the state will claim her life for its own purposes to protect itself from danger . licinia could be accused of incestum , meaning unchastity , at any time and be sacrificed whether she 's innocent or guilty . licinia fully understands now why her predecessor was buried alive . ten years ago , the flame of vesta went out . the priestesses knew that they could n't keep it a secret . the future of rome depended upon it . they went to the chief priest and he opened an investigation to discover why the flame had failed . someone came forward and claimed that one of the vestals was no longer a virgin . that was the beginning of the end . the accused protested her innocence , but it was n't enough . she was tried and found guilty . that vestal 's death was meant to protect the city , but licinia weeps for what has been lost and for what she knows now . her own path was paved by the death of another , and her life could be taken just as easily for something as simple as a flame going out .

for the first ten years of licinia 's service , she 's considered in training , learning how to be a vestal virgin . her most important duty is keeping vigil over the flame of vesta , the virgin goddess of the hearth . vesta does n't have a statue like other roman gods and goddesses .

the flame of vesta was very important to the ancient romans . so much so that the most important duty of the vestals was to take turns keeping vigil over the flame to make sure that it continued to burn . what other reasons can you come up with for why fire was important in the ancient world ?

translator : andrea mcdonough reviewer : bedirhan cinar nearly every one of your science classes starts off with the scientific method . you recognize this ? ask a question , form a hypothesis , perform an experiment , collect data , draw conclusions , and then memorize a bunch of facts . this is really boring ! science is not a simple recipe in a cookbook , and learning is not memorizing facts for tests . yet , that is exactly what we do . we have to change this ! we have to look at how curiosity can ultimately benefit society by looking towards tomorrow , by going through a path from involvement to imagination to invention to innovation . and i 'd like to illustrate this by telling you the real story about how we discovered how geckos stick . first you need to get involved . you need to do curiosity-driven research yourself . we know that learning by being an active researcher is the best way to learn . imagine being in my lab and trying to discover how geckos stick . `` here is one of our subjects . this is a crested gecko . we are going to put the gecko on glass and we 're going to use a high speed camera that can capture up to 1,000 pictures in one second . there he goes . ok , record it . there 's the animal 's toes . '' `` so how do their feet stick and unstick so quickly ? '' how < i > do < /i > they do this ? we wonder , it 's kind of crazy , right ? it 's hard to believe . well it turns out , it was already known that the geckos have hairy toes , and those hairs are really small compared to your hair , and the little tips at the end are even smaller . well , my student tanya , who is not much older than some of you when she did this , a sophomore undergraduate , tried to figure this out , and we told that her that in order to do this , you 'd have to measure the force of a single hair . though we kind of only did this jokingly because these hairs are so small , we did n't think it was possible . but tanya did n't know that , and she went on to build the simplest , most beautiful measurement device ever . here it is : she took one of those tiny little hairs and put it on to a probe , and then she began pushing it into the metal beam . now she was very frustrated for months - it did n't stick . but she had figured out she had to orient it just like the gecko grabs on , and then it worked ! and there 's the little split ends grabbing the beam in that little window . and then she did something magical : for the first time ever , she measured the force of a single gecko hair that allowed her to discover a completely new way to stick to something , something no human has ever known before . they have hairy little toes , huge numbers of hairs , and each hair has the worst case of split ends possible , 100 to 1,000 nano-tips that an animal has on one hair , and 2 billion total , and they do n't stick by glue , or by suction , or by velcro . it was discovered that they stick by inter-molecular forces alone , by van der waals forces , and you 'll learn this in chemistry and physics , if you take it . it 's unbelievable ! it 's a whole new way of thinking about making an adhesive ! well , this is n't the end of the story , there are still mysteries . why are the gecko 's feet looking like this ? they have bizarre toes and we do n't know why . if you go into a museum and look at each gecko species , you see they have all different hairs , different lengths , and thicknesses , and patterns . why ? i do n't know ! but you should come to berkeley and help me figure this out . it 's just about right , so , apply . but it 's a mystery . there is even more stuff that is unknown . this tarantula also has hairs and can stick this way , too , but recently it was found that they also can secrete silk from their feet , not just their behind , like you know they do . and even more recently , my graduate student ann showed that all spiders can secrete glue , and we know nothing about this glue except it was around way before this guy , millions of years before . so do n't stop at the discovery , next imagine the possible uses for society . here is the first human supported by a gecko-inspired adhesive . this is my former graduate student , kellar autumn , who is professor at lewis and clark , offering his second born child for the test . and she 's a very good sport about it ! now imagine all the things you could make from this , not only adhesives , but products in sports , and biomedicine , technology , robotics , toys , automotive , fashion , clothes , and yes , even hair pieces . i swear to you , we got a call from michael jackson 's hairdresser about hair pieces before he passed away . who would have guessed from studying geckos ? ! ? next , invent a game-changing technology , device , or product . like my engineering colleague at berkeley , ron fearing , did when he made one of the first synthetic , self-cleaning dry adhesives after the simplest version that you see in animals . believe it or not , right now , because of this work , you can make your own synthetic gecko nano-tape by nano-molding with just a few parts , and here 's the recipe that we can give you . it 's been incredible since we made this discovery of all the papers and the work and the different ways to make it , it 's emerging into a billion dollar industry . and who would have imagined that it started because we were curious about how geckos can run up walls . next you need to innovate , create a business that ultimately benefits society . did you know that there are 6 million people per year that have chronic wounds , 2 million develop an infection , and infections account for 100,000 hospital deaths ? imagine if you could build a company that could produce a gecko-inspired band-aid that would remove the pain and suffering . just a simple invention . if you look at the last three great earthquakes , over 700,000 people were trapped and lost their lives . imagine the company that made a search-and-rescue robot inspired from a gecko that could move anywhere and quickly find individuals that have been trapped , that sometimes survive as long as two weeks . there is a gecko-inspired robot , stickybot , from the stanford group , that can grab on to any surface . now we ran our own , for ted , mini bio-inspired design challenge to get you to think about these kinds of products . we have a winner . here 's the winner . the winner came up with this design called stickyseat . really clever . it 's a seat that is not only comfortable , but it aids a seat belt , if you were in an accident , in terms of keeping your seat and moving . this is brilliant ! we did n't think about this , although we might think about patenting it now , but there is a winner for this , and the winner , and you ca n't , you ca n't make up something like this , the winner 's name is harry . where 's harry ? harry , come here , we have a prize for you . where 's harry ? harry ! come here ! we have a crested gecko for you that has very cool hairs on it . congratulations for harry ! excellent job ! so do n't worry , if you missed out on this , it 's ok because we are doing another design challenge working with the san diego zoo . they 're developing a best ideas project in san diego , but it 's going to go national . and i 'll leave you with a fact that you should keep being curious because curiosity-based research leads to the biggest benefits , as we showed you in our example , and you < i > can < /i > make a difference < i > now < /i > because like tanya , you do n't know what ca n't be done . thank you .

and i 'd like to illustrate this by telling you the real story about how we discovered how geckos stick . first you need to get involved . you need to do curiosity-driven research yourself .

what did tanya , a student in robert full 's lab , need to figure out before she could answer her question ?