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`` hey , another atom . i 'm hydrogen , nice to meet you . how are you feeling about the jump ? '' `` hi there , i 'm antihydrogen , your antiatom , and to be honest , i 'm feeling kind of neutral . my positron and antiproton balance out , just like your electron and proton , right ? '' `` hey , yeah ! you look just like me , but different somehow . '' `` whoa , be careful ! if we get too close , we 'll disappear in a spark of energy . i 'd like to stay in one piece . '' `` oh wow , sorry . '' `` it 's okay . i was just thinking , it 's kind of weird for us to be chatting like this before our jump above cern . '' `` why 's that ? '' `` well , for starters , how do we know we 'll both fall ? '' `` of course we 'll fall . it 's gravity , you know , the force of attraction between masses . i even know how fast we should fall . galileo showed in that tower experiment that all falling objects accelerate at the same rate , regardless of mass . '' `` that 's for bigger objects . it 's a different story for small particles like us . our mass is so tiny that the gravitational force we experience is miniscule , and if the particles are charged , like my antiproton or your proton , then it becomes impossible to detect compared to the much greater electromagnetic force acting on them . '' `` but that 's only for charged particles . you and i are both neutral . our charges balance out , so the electromagnetic force is small and the gravitational force should be detectable . i know mine 's been measured . '' `` because you 're everywhere , but i 'm kind of hard to find . '' `` why is that , anyway ? should n't there have been an equal amount of matter and antimatter created in the big bang ? '' `` you 'd think so , but then all of those particles would have annihilated each other into energy , remember ? and the universe is obviously full of matter . no one knows why there is more matter than antimatter , which is why scientists are so interested in studying me . '' `` so where do they find you anyway ? '' `` actually , i was made in that lab down there . they needed an accelerator to make my antiproton because it 's so heavy , just as heavy as your proton . getting my positron was easier . it 's much lighter , like your electron , and there are materials that naturally decay by emitting one . then they just had to put the two together and they got me . but it 's only recently that they 've been able to keep me around long enough to study my properties . '' `` and now they 've sent you on this jump with me . hey , wait a minute . '' `` that 's right . we 're reenacting galileo 's experiment , but with matter and antimatter instead of two objects made of matter . '' `` so what 's going to happen ? are you going to fall upwards or something ? '' `` only one way to find out ! ''
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`` that 's right . we 're reenacting galileo 's experiment , but with matter and antimatter instead of two objects made of matter . '' `` so what 's going to happen ?
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matter and antimatter physical properties are very similar . masses , charges and internal properties have been measured to be the same ( to a given precision ) on absolute value . how can we then differentiate matter from antimatter ?
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i 'm a geographer at middlebury college , and i use digital technologies to reimagine the past . i want to take you to gettysburg , pennsylvania , july 1 , 1863 , we 're right in the middle of the civil war . from the northwest , the confederate forces under robert e. lee , and from the southeast , the union forces under george meade , converge at this place more or less by chance . they did n't plan to fight here . but the battle of gettysburg turns out to be the turning point of the civil war . now , robert e. lee is probably the most famous american general , widely respected . but at gettysburg , he made some crucial mistakes , probably the most important was in ordering pickett 's charge . i 'm going to show you how i took a new look at pickett 's charge with historical maps and gis . my key map was this extraordinary thing , 12 feet by 13 feet , in the vault of treasures at the national archives . here are some of my students at middlebury to give you a sense of that scale . it was recompiled into a finished map the size of a large poster . you can see the layout of the town of gettysburg , you see the undulating shape of the terrain . if you look at other details , you can see forests and orchards and streams and roads . i want you to look at those very fine black lines . those are called contour lines , and they show the elevation at 4-foot intervals , the most detailed elevation i have ever seen . now , before i explain this image , i need to tell you a little about gis . it stands for geographic information systems . it 's a kind of software that allows you to map almost anything . you can also use it to do terrain analysis . for example , if you 're building a ski resort , and you want people to get off the lift and have the most spectacular view possible , you use viewshed analysis that shows you what you can see from a certain point on the terrain . i used that to place myself digitally in the footsteps of robert e. lee , to ask , 'what could he see ? ' and 'what could he not see ? ' that might have influenced his command decisions . now , back to these contour lines . this is the best elevation data that i could find . i traced all of the lines , you see in the black and white drawings , some of those lines , stitched them together , gave them elevation values , and then transformed it , within the gis program , into a continuous terrain . this is a simulation of the ground of the battlefield . now , i 'm ready to place myself in lee 's boots and ask what he could see . the particular moment i want to look at is that battle i mentioned , pickett 's charge . lee makes a crucial decision on the morning of the third day , this is july 3rd , 1863 , the fighting on the previous two days has been fierce . it 's gone back and forth , neither side has a clear advantage . lee goes down to the bottom of the field , we know this , here 's my gorgeous source map again and watch the red circle appear . he goes to the southern end of the battlefield at about 8:00 in the morning with his binoculars and looks through them to figure out where to attack the union line , where are they most vulnerable . now , in this next image , i 'm going to show you the gis process called viewshed analysis , along with lee 's line of sight in that sort of reddish cone is the direction we think he was looking . viewshed analysis , remember , tells me what i can see and what i ca n't see from a certain point , so in this map , the grey area is what lee could n't see . the clear area , where you see that historic map coming through , is what he could 've definitely seen . notice how much of the right side of the map is in grey . now , we add another crucial piece of information . someone named john bachelder , a landscape painter from new hampshire , went down to the battlefield as soon as he heard about the fight , in order to document where troops had been and to try to paint the battle . he ended up getting $ 10,000 from congress in order to document troop positions down to the half hour . he produced 24 maps that we also digitized and brought into the gis . and this next map shows that troop position information ; it 's crucial for understanding what lee could and what he could n't see . now , if you look closely at this map , you might be able to see kind of the middle is a black oval around an area that 's relatively clear . the blue markings in that black oval are union troops that i 'm definitely sure that lee could see . but if you look to the right of that , you 'll see an awful lot of blue markings . those are union troops in the shadows . now , we know that on the night before lee 's reconnaissance so , the night of july 2nd , he sent out scouts . of course , he wanted to know where the federal troops were . but quite astonishingly , we have no explanation for this . the scouts came back saying , 'do n't worry , general lee . we did n't see any troops to the east , ' in your map to the right , 'of the roundtops , some really big hills . ' we do n't know if they got drunk or fell asleep , but they did n't see almost a third of the union army . so lee is blind from his scouts , and from his viewpoint , he 's also blind . he decides to attack what he thinks is the weak middle of the union line , not knowing about where the rest of the troops are . so if you look in the middle of this image , there 's a gap in the union line from where the blue soldiers are at the north of the battlefield and at the south . so let me now play out , using these troop positions , pickett 's charge . the confederate soldiers are lined up on the west side of the battlefield , standing under the trees . 18,000 men who first begin to walk and then trot and then run across open farm fields with their rifles leveled at the federal line . now , the union army has about 15-20 minutes to organize itself . they see that the confederates are converging on the middle of their line , and what do they do ? the blue arrow here , representing movement of the union troops , they pull their troops toward that weak center , and let me show you how they were able to concentrate those men in a remarkably short period of time . lee did n't know that the union could 've done this . you see now , they 're standing like a wall , ready to receive the confederate assault , which happens between 1:30 and about 2:00 , 2:30 in the afternoon . there is tremendously fierce fighting , hand-to-hand combat . now these blue lines , coming in between 2-2:30 in the afternoon , are pulling more reserves , more reinforcements , to that weak center of the union line . what happens ? the union soliders drive the confederates off . lee rides out , among his men , at 3:00 in the afternoon , saying , 'i 'm sorry . it 's my fault . it 's my fault . ' this story of sight has been a missing part of the battle of gettysburg . here 's their retreat . historians have not been previously able to figure out what he could and could n't see . i think it helps explain his decision . why ? because from his point of view , the federals were very weak . he was attacking at the logical place , but without full knowledge , he set his men out for a dreadful defeat . now , there 's one more piece to this story . last summer was the 150th anniversary of the battle of gettysburg . and i was able to work with a 3d animator , so we were able to use the gis information to render the terrain issue as you see it here . and my closing story is about how sight helped the other side . a federal general named gk warren stood in the spot that this panoramic view is showing you , looking out over the battlefield . and at a key moment on day two , he was able to see on the far horizon confederate soldiers emerging out of the trees who were about to attack little roundtop . he called in reinforcements just in time and saved the day for the union , setting the stage for the union almost-victory on day three . so , i hope that all of you who are so gifted with digital technologies will begin to think about how you can use them for history . it can be amazing . thank you .
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you can also use it to do terrain analysis . for example , if you 're building a ski resort , and you want people to get off the lift and have the most spectacular view possible , you use viewshed analysis that shows you what you can see from a certain point on the terrain . i used that to place myself digitally in the footsteps of robert e. lee , to ask , 'what could he see ? '
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if you 're building a ski resort and you want people to get the most spectacular views , what do you use ?
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three and a half thousand years ago in egypt , a noble pharaoh was the victim of a violent attack . but the attack was not physical . this royal had been dead for 20 years . the attack was historical , an act of damnatio memoriae , the damnation of memory . somebody smashed the pharaoh 's statues , took a chisel and attempted to erase the pharaoh 's name and image from history . who was this pharaoh , and what was behind the attack ? here 's the key : the pharaoh hatshepsut was a woman . in the normal course of things , she should never have been pharaoh . although it was legal for a woman to be a monarch , it disturbed some essential egyptian beliefs . firstly , the pharaoh was known as the living embodiment of the male god horus . secondly , disturbance to the tradition of rule by men was a serious challenge to maat , a word for `` truth , '' expressing a belief in order and justice , vital to the egyptians . hatshepsut had perhaps tried to adapt to this belief in the link between order and patriarchy through her titles . she took the name maatkare , and sometimes referred to herself as hatshepsu , with a masculine word ending . but apparently , these efforts did n't convince everyone , and perhaps someone erased hatshepsut 's image so that the world would forget the disturbance to maat , and egypt could be balanced again . hatshepsut , moreover , was not the legitimate heir to the thrown , but a regent , a kind of stand-in co-monarch . the egyptian kingship traditionally passed from father to son . it passed from thutmose i to his son thutmose ii , hatshepsut 's husband . it should have passed from thutmose ii directly to his son thutmose iii , but thutmose iii was a little boy when his father died . hatshepsut , the dead pharaoh 's chief wife and widow , stepped in to help as her stepson 's regent but ended up ruling beside him as a fully fledged pharaoh . perhaps thutmose iii was angry about this . perhaps he was the one who erased her images . it 's also possible that someone wanted to dishonor hatshepsut because she was a bad pharaoh . but the evidence suggests she was actually pretty good . she competently fulfilled the traditional roles of the office . she was a great builder . her mortuary temple , djeser-djeseru , was an architectural phenomenon at the time and is still admired today . she enhanced the economy of egypt , conducting a very successful trade mission to the distant land of punt . she had strong religious connections . she even claimed to be the daughter of the state god , amun . and she had a successful military career , with a nubian campaign , and claims she fought alongside her soldiers in battle . of course , we have to be careful when we assess the success of hatshepsut 's career , since most of the evidence was written by hatshepsut herself . she tells her own story in pictures and writing on the walls of her mortuary temple and the red chapel she built for amun . so who committed the crimes against hatshepsut 's memory ? the most popular suspect is her stepson , nephew and co-ruler , thutmose iii . did he do it out of anger because she stole his throne ? this is unlikely since the damage was n't done until 20 years after hatshepsut died . that 's a long time to hang onto anger and then act in a rage . maybe thutmose iii did it to make his own reign look stronger . but it is most likely that he or someone else erased the images so that people would forget that a woman ever sat on egypt 's throne . this gender anomaly was simply too much of a threat to maat and had to be obliterated from history . happily , the ancient censors were not quite thorough enough . enough evidence survived for us to piece together what happened , so the story of this unique powerful woman can now be told .
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she tells her own story in pictures and writing on the walls of her mortuary temple and the red chapel she built for amun . so who committed the crimes against hatshepsut 's memory ? the most popular suspect is her stepson , nephew and co-ruler , thutmose iii .
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describe hatshepsut 's path to the throne . create a diagram .
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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 .
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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 .
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what is bud burst ?
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studies have shown that taking vitamins is good for your health and bad for your health . that newly discovered herb can improve your memory or destroy your liver . headlines proclaim a promising new cancer treatment and never mention it again . on a daily basis , we are bombarded with attention-grabbing news , backed up by scientific studies , but what are these studies ? how are they performed ? and how do we know whether they 're reliable ? when it comes to dietary or medical information , the first thing to remember is that while studies on animals or individual cells can point the way towards further research , the only way to know how something will affect humans is through a study involving human subjects . and when it comes to human studies , the scientific gold standard is the randomized clinical trial , or rct . the key to rcts is that the subjects are randomly assigned to their study groups . they are often blinded to make them more rigorous . this process attempts to ensure that the only difference between the groups is the one the researchers are attempting to study . for example , when testing a new headache medication , a large pool of people with headaches would be randomly divided into two groups , one receiving the medication and another receiving a placebo . with proper randomization , the only significant overall difference between the two groups will be whether or not they received the medication , rather than other differences that could affect results . randomized clinical trials are incredible tools , and , in fact , the us food and drug administration often requires at least two to be conducted before a new drug can be marketed . but the problem is that an rct is not possible in many cases , either because it 's not practical or would require too many volunteers . in such cases , scientists use an epidemiological study , which simply observes people going about their usual behavior , rather than randomly assigning active participants to control invariable groups . let 's say we wanted to study whether an herbal ingredient on the market causes nausea . rather than deliberately giving people something that might make them nauseated , we would find those who already take the ingredient in their everyday lives . this group is called the cohort . we would also need a comparison group of people who do not have exposure to the ingredient . and we would then compare statistics . if the rate of nausea is higher in the herbal cohort , it suggests an association between the herbal supplement and nausea . epidemiological studies are great tools to study the health effects of almost anything , without directly interfering in people 's lives or assigning them to potentially dangerous exposures . so , why ca n't we rely on these studies to establish causal relationships between substances and their effects on health ? the problem is that even the best conducted epidemiological studies have inherent flaws . precisely because the test subjects are not randomly assigned to their groups . for example , if the cohort in our herbal study consisted of people who took the supplement for health reasons , they may have already had higher rates of nausea than the other people in the sample . or the cohort group could 've been composed of people who shop at health food stores and have different diets or better access to healthcare . these factors that can affect results , in addition to the factor being studied , are known as confounding variables . these two major pitfalls , combined with more general dangers , such as conflicts of interest or selective use of data , can make the findings of any particular epidemiological study suspect , and a good study must go out of its way to prove that its authors have taken steps to eliminate these types of errors . but even when this has been done , the very nature of epidemiological studies , which examine differences between preexisting groups , rather than deliberately inducing changes within the same individuals , means that a single study can only demonstrate a correlation between a substance and a health outcome , rather than a true cause and effect relationship . at the end of the day , epidemiological studies have served as excellent guides to public health , alerting us to critical health hazards , such as smoking , asbestos , lead , and many more . but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction . so , the next time you see a headline about a new miracle cure or the terrible danger posed by an everyday substance , try to learn more about the original study and the limitations inherent in any epidemiological study or clinical trial before jumping to conclusions .
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headlines proclaim a promising new cancer treatment and never mention it again . on a daily basis , we are bombarded with attention-grabbing news , backed up by scientific studies , but what are these studies ? how are they performed ? and how do we know whether they 're reliable ?
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what kind of studies were performed to evaluate the drugs i take for safety and effectiveness ?
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the onset of cancer usually begins as a solitary tumor in a specific area of the body . if the tumor is not removed , cancer has the ability to spread to nearby organs , as well as places far away from the origin , such as the brain . so how does cancer move to new areas , and why are some organs more likely to get infected than others ? the process of cancer spreading across the body is known as metastasis . it begins when cancer cells from an initial tumor invade nearby normal tissue . as the cells proliferate , they spread via one of the three common routes of metastasis : transcoelomic , lymphatic , or hematogenous spread . in transcoelomic spread , malignant cells penetrate the covering surfaces of cavities in our body . these surfaces are known as peritoneum and serve as walls to segment the body cavity . malignant cells in ovarian cancer , for example , spread through peritoneum , which connects the ovary to the liver , resulting in metastasis on the liver surface . next , cancerous cells invade blood vessels when they undergo hematogenous spread . as there are blood vessels almost everywhere in the body , malignant cells utilize this to reach more distant parts of the body . finally , lymphatic spread occurs when the cancer invades the lymph nodes , and travels to other parts of the body via the lymphatic system . as this system drains many parts of the body , it also provides a large network for the cancer . in addition , the lymphatic vessels empty into the blood circulation , allowing the malignant cells to undergo hematogenous spread . once at a new site , the cells once again undergo proliferation , and form small tumors known as micrometastases . these small tumors then grow into full-fledged tumors , and complete the metastatic process . different cancers have been known to have specific sites of metastasis . for example , prostate cancer commonly metastasizes to the bone , while colon cancer metastasizes to the liver . various theories have been proposed to explain the migration pattern of malignant cells . of particular interest are two conflicting theories . stephen paget , an english surgeon , came up with the seed and soil theory of metastasis . the seed and soil theory stated that cancer cells die easily in the wrong microenvironment , hence they only metastasize to a location with similar characteristics . however , james ewing , the first professor of pathology at cornell university , challenged the seed and soil theory , and proposed that the site of metastasis was determined by the location of the vascular and lymphatic channels which drain the primary tumor . patients with primary tumors that were drained by vessels leading to the lung would eventually develop lung metastases . today , we know that both theories contain valuable truths . yet the full stories of metastasis is much more complicated than either of the two proposed theories . factors like the cancer cell 's properties , and the effectiveness of the immune system in eliminating the cancer cells , also play a role in determining the success of metastasis . unfortunately , many questions about metastasis remain unanswered until today . understanding the exact mechanism holds an important key to finding a cure for advanced stage cancers . by studying both the genetic and environmental factors , which contribute to successful metastasis , we can pinpoint ways to shut down the process . the war against cancer is a constant struggle , and scientists are hard at work developing new methods against metastasis . of recent interest is immunotherapy , a modality which involves harnessing the power of the immune system to destroy the migrating cells . this can be done in different ways , such as training immune cells to recognize cancerous cells via vaccines . the growth and activity of the immune cells can also be stimulated by injecting man-made interleukins , chemicals which are usually secreted by the immune cells of the body . these two treatments are only the tip of the iceberg . with the collaborated research efforts of governments , companies and scientists , perhaps the process of metastasis will be stopped for good .
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of particular interest are two conflicting theories . stephen paget , an english surgeon , came up with the seed and soil theory of metastasis . the seed and soil theory stated that cancer cells die easily in the wrong microenvironment , hence they only metastasize to a location with similar characteristics .
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which theory is more popularly used to explain metastasis today ? give some examples of metastatic cancers that spread according to each theory .
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( music ) ( music ) we live in an interconnected , an increasingly globalized world . thanks to international jet travel , people and the diseases they carry can be in any city on the planet in a matter of hours . and once a virus touches down , sometimes all it takes is one sneeze to spread the infection throughout the community . when humans were hunter-gatherers , roaming the wild savannas , we were never in one place long enough , and settlements were not large enough to sustain the transmission of infectious microbes . but with the advent of the agricultural revolution 10,000 years ago , and the arrival of permanent settlements in the middle east , people began living side-by-side with animals , facilitating the spread of bacteria and viruses between cattle and humans . epidemics and pandemics come in many shapes and forms . in 2010 , for instance , a devastating earthquake struck haiti , forcing thousands of people into temporary refugee camps . within weeks , the camps had become breeding grounds for cholera , a bacteria spread by contaminated water , triggering a country-wide epidemic . but the most common cause of epidemics are viruses , such as measles , influenza and hiv . and when they go global , we call them pandemics . pandemics have occurred throughout human history , some have left scars on the tissue and bone of their victims , while evidence for others comes from preserved dna . for instance , scientists have recovered dna from the bacteria that transmits tuberculosis from the remains of ancient egyptian mummies . and in 2011 , scientists investigating a plague pit in the city of london were able to reconstruct the genome of yersinia pestis , the bacterium responsible for the black death of the 14th century . it is thought the plague originated in china in around 1340 , spreading west along the silk road , the caravan route running from mongolia to the crimea . in 1347 , the plague reached the mediterranean , and by 1400 , it had killed in excess of 34 million europeans , earning it the title , the great mortality . it was later historians who called it the black death . however , by far the greatest pandemic killer is influenza . flu is constantly circulating between the southern and northern hemispheres . in north america and europe , seasonal flus occur every autumn and winter . as the majority of children and adults will have been exposed to the virus in previous seasons , these illnesses are usually mild . however , every 20 to 40 years or so the virus undergoes a dramatic mutation . usually this occurs when a wild flu virus circulating in ducks and farm poultry meets a pig virus , and they exchange genes . this process is known as antigenic shift and has occurred throughout human history . the first recorded pandemic occurred in 1580 . the 18th and 19th centuries saw at least six further pandemics . in terms of mortality , none can compare with the great flu pandemic of 1918 . the first indication of the pandemic came in the spring , when american troops in northern france began complaining of chills , headaches and fever . then , the following september , at a u.s. army barracks near boston , soldiers started collapsing on parade , prompting their removal to the camp infirmary . as a surgeon there recalled , two hours after admission , they had the mahogany spots over the cheekbones and a few hours later you can begin to see the cyanosis extending from their ears and spreading all over the face . it is only a matter of a few hours then until death comes , and it is simply a struggle for air until they suffocate . on the s.s. leviathan , a huge american transport en route to bordeaux , sick men hemorrhaged blood from their noses , turning the decks between their bunks slick with bodily fluids . meanwhile , british soldiers returning from northern france on furlough introduced the flu to dover and other channel ports , from where the virus was carried by rail to london . by the time the pandemic had run its course in april 1919 , an estimated 675,000 americans and 230,000 britons were dead . in india alone , some 10 million were killed , and worldwide the death toll was an astonishing 50 million . but that was then . today , planes can transport viruses to any country on the globe in a fraction of the time it took in 1918 . in february 2003 , for instance , a chinese doctor arrived at the metropole hotel in hong kong feeling unwell . unknown to him , he was harboring a new animal-origin virus called sars , short for severe acute respiratory syndrome . within 24 hours of checking into room 913 , sixteen other guests had been infected , and over the following days five boarded planes to overseas destinations , spreading the virus to vietnam , singapore and canada . flights between hong kong , toronto and other international cities were quickly grounded and thanks to other emergency measures , a pandemic was averted . by the time the outbreak was over four months later , sars had infected 29 countries worldwide and more than 1,000 people were dead . for all that the virus was rapidly contained , however , there was little that could be done about the alarming news reports carried by cable news channels and the internet . as bloggers added to the hysteria by spreading unfounded conspiracy theories , tourism in hong kong and other affected cities ground to a halt , costing businesses more than 10 billion u.s. dollars . one business , however , did very well . above all , sars was a reminder that pandemics have always been associated with panic . if history teaches us anything , it 's that while pandemics may start small , their impacts can be as dramatic as wars and natural disasters . the difference today is that science gives us the ability to detect pandemics right at the very beginning and to take action to mitigate their impacts before they spread too widely . ( music )
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usually this occurs when a wild flu virus circulating in ducks and farm poultry meets a pig virus , and they exchange genes . this process is known as antigenic shift and has occurred throughout human history . the first recorded pandemic occurred in 1580 .
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what is antigenic shift ?
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the earth intercepts a lot of solar power : 173 thousand terawatts . that 's ten thousand times more power than the planet 's population uses . so is it possible that one day the world could be completely reliant on solar energy ? to answer that question , we first need to examine how solar panels convert solar energy to electrical energy . solar panels are made up of smaller units called solar cells . the most common solar cells are made from silicon , a semiconductor that is the second most abundant element on earth . in a solar cell , crystalline silicon is sandwiched between conductive layers . each silicon atom is connected to its neighbors by four strong bonds , which keep the electrons in place so no current can flow . here 's the key : a silicon solar cell uses two different layers of silicon . an n-type silicon has extra electrons , and p-type silicon has extra spaces for electrons , called holes . where the two types of silicon meet , electrons can wander across the p/n junction , leaving a positive charge on one side and creating negative charge on the other . you can think of light as the flow of tiny particles called photons , shooting out from the sun . when one of these photons strikes the silicon cell with enough energy , it can knock an electron from its bond , leaving a hole . the negatively charged electron and location of the positively charged hole are now free to move around . but because of the electric field at the p/n junction , they 'll only go one way . the electron is drawn to the n-side , while the hole is drawn to the p-side . the mobile electrons are collected by thin metal fingers at the top of the cell . from there , they flow through an external circuit , doing electrical work , like powering a lightbulb , before returning through the conductive aluminum sheet on the back . each silicon cell only puts out half a volt , but you can string them together in modules to get more power . twelve photovoltaic cells are enough to charge a cellphone , while it takes many modules to power an entire house . electrons are the only moving parts in a solar cell , and they all go back where they came from . there 's nothing to get worn out or used up , so solar cells can last for decades . so what 's stopping us from being completely reliant on solar power ? there are political factors at play , not to mention businesses that lobby to maintain the status quo . but for now , let 's focus on the physical and logistical challenges , and the most obvious of those is that solar energy is unevenly distributed across the planet . some areas are sunnier than others . it 's also inconsistent . less solar energy is available on cloudy days or at night . so a total reliance would require efficient ways to get electricity from sunny spots to cloudy ones , and effective storage of energy . the efficiency of the cell itself is a challenge , too . if sunlight is reflected instead of absorbed , or if dislodged electrons fall back into a hole before going through the circuit , that photon 's energy is lost . the most efficient solar cell yet still only converts 46 % of the available sunlight to electricity , and most commercial systems are currently 15-20 % efficient . in spite of these limitations , it actually would be possible to power the entire world with today 's solar technology . we 'd need the funding to build the infrastructure and a good deal of space . estimates range from tens to hundreds of thousands of square miles , which seems like a lot , but the sahara desert alone is over 3 million square miles in area . meanwhile , solar cells are getting better , cheaper , and are competing with electricity from the grid . and innovations , like floating solar farms , may change the landscape entirely . thought experiments aside , there 's the fact that over a billion people do n't have access to a reliable electric grid , especially in developing countries , many of which are sunny . so in places like that , solar energy is already much cheaper and safer than available alternatives , like kerosene . for say , finland or seattle , though , effective solar energy may still be a little way off .
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where the two types of silicon meet , electrons can wander across the p/n junction , leaving a positive charge on one side and creating negative charge on the other . you can think of light as the flow of tiny particles called photons , shooting out from the sun . when one of these photons strikes the silicon cell with enough energy , it can knock an electron from its bond , leaving a hole .
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what is light ?
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thinking of getting a tattoo ? decorating your birthday suit would add another personal story to a history of tattoos stretching back at least 8000 years . tattooed mummies from around the world attest to the universality of body modification across the millennia , and to the fact that you really were stuck with it forever if your civilization never got around to inventing laser removal . a mummy from the chinchorro culture in pre-incan peru has a mustache tattooed on his upper lip . ötzi , mummified iceman of the alps , has patterned charcoal tats along his spine , behind his knee and around his ankles , which might be from an early sort of acupuncture . the mummy of amunet , a priestess in middle kingdom egypt , features tattoos thought to symbolize sexuality and fertility . even older than the mummies , figurines of seemingly tattooed people , and tools possibly used for tattooing date back tens of thousands of years . tattoos do n't have one historical origin point that we know of , but why do we english speakers call them all tattoos ? the word is an anglophonic modification of `` tatao , '' a polynesian word used in tahiti , where english captain james cook landed in 1769 and encountered heavily tattooed men and women . stories of cook 's findings and the tattoos his crew acquired cemented our usage of `` tattoo '' over previous words like `` scarring , '' `` painting , '' and `` staining , '' and sparked a craze in victorian english high society . we might think of victorians having victorian attitudes about such a risque thing , and you can find such sentiments , and even bans , on tattooing throughout history . but while publicly some brits looked down their noses at tattoos , behind closed doors and away from their noses , lots of people had them . reputedly , queen victoria had a tiger fighting a python , and tattoos became very popular among cook 's fellow soldiers , who used them to note their travels . you crossed the atlantic ? get an anchor . been south of the equator ? time for your turtle tat . but westerners sported tattoos long before meeting the samoans and maori of the south pacific . crusaders got the jerusalem cross so if they died in battle , they 'd get a christian burial . roman soldiers on hadrian 's wall had military tattoos and called the picts beyond it `` picts , '' for the pictures painted on them . there 's also a long tradition of people being tattooed unwillingly . greeks and romans tattooed slaves and mercenaries to discourage escape and desertion . criminals in japan were tattooed as such as far back as the 7th century . most infamously , the nazis tattooed numbers on the chest or arms of jews and other prisoners at the auschwitz concentration camp in order to identify stripped corpses . but tattoos forced on prisoners and outcasts can be redefined as people take ownership of that status or history . primo levi survived auschwitz and wore short sleeves to germany after the war to remind people of the crime his number represented . today , some holocaust survivors ' descendants have their relatives numbers ' tattooed on their arms . the torah has rules against tattoos , but what if you want to make indelible what you feel should never be forgotten ? and those criminals and outcasts of japan , where tattooing was eventually outlawed from the mid-19th century to just after world war ii , added decoration to their penal tattoos , with designs borrowed from woodblock prints , popular literature and mythical spirtual iconography . yakuza gangs viewed their outsider tattoos as signs of lifelong loyalty and courage . after all , they lasted forever and it really hurt to get them . for the maori , those tattoos were an accepted mainstream tradition . if you shied away from the excruciating chiseling in of your moko design , your unfinished tattoo marked your cowardice . today , unless you go the traditional route , your tattoo artist will probably use a tattoo machine based on the one patented by samuel o'reilly in 1891 , itself based on thomas edison 's stencil machine from 1876 . but with the incredibly broad history of tattoos giving you so many options , what are you going to get ? this is a bold-lined expression of who you are , or you want to appear to be . as the naturalist aboard cook 's ship said of the tataoed tahitians , `` everyone is marked , thus in different parts of his body , according maybe to his humor or different circumstances of his life . '' maybe your particular humor and circumstances suggest getting a symbol of cultural heritage , a sign of spirituality , sexual energy , or good old-fashioned avant-garde defiance . a reminder of a great accomplishment , or of how you think it would look cool if hulk hogan rode a rhino . it 's your expression , your body , so it 's your call . just two rules : you have to find a tattooist who wo n't be ashamed to draw your idea , and when in doubt , you can never go wrong with `` mom . ''
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thinking of getting a tattoo ? decorating your birthday suit would add another personal story to a history of tattoos stretching back at least 8000 years .
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what might a japanese person with a penal tattoo have added to it ?
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ah , spring . grass growing , flowers blooming , trees growing new leaves , but if you get allergies , this explosion of new life probably inspires more dread than joy . step outside , and within minutes , you 're sneezing and congested . your nose is running , your eyes are swollen and watery , your throat is itchy . for you and millions of others , it 's seasonal allergy time . so what 's behind this onslaught of mucus ? the answer lies within you . it 's your immune system . seasonal allergies , also called hay fever , or allergic rhinitis , are a hypersensitive immune response to something that 's not actually harmful . pollen from trees and grass , and mold spores from tiny fungi find their way into your mucous membranes and your body attacks these innocuous travelers the same way it would infectious bacteria . the immune system has a memory . when a foreign substance gets tagged as threatening , white blood cells produce customized antibodies that will recognize the offender the next time around . they then promptly recruit the body 's defense team . but sometimes , the immune system accidentally discriminates against harmless substances , like pollen . when it wafts in again , antibodies on the surface of white blood cells recognize it and latch on . this triggers the cell to release inflammatory chemicals , like histamine , which stimulate nerve cells , and cause blood vessels in the mucous membranes to swell and leak fluid . in other words , itchiness , sneezing , congestion , and a runny nose . allergies usually , but not always , show up for the first time during childhood . but why do some people get allergies and others do n't ? allergies tend to run in families , so genetics may be one culprit . in fact , errors in a gene that helps regulate the immune system are associated with higher rates of allergies . the environment you grow up in matters , too . being exposed to an allergen as a baby makes you less likely to actually develop an allergy to it . people who grow up on farms , in big families , and in the developing world also tend to have fewer allergies , although there are plenty of exceptions , partly thanks to genetics . one theory is that as children , they encounter more of the microbes and parasites that co-evolved with traditional hunter-gatherer societies . called the hygiene hypothesis , the idea is that when the immune system is n't exposed to the familiar cast of microbes , it 'll keep itself busy mounting defenses against harmless substances , like pollen . another theory is that an immune system toughened up by a barrage of pathogens is less likely to overreact to allergens . pollen is a common offender , just because we encounter so much of it , but there 's a long list of substances : dust , animal dander , insect venom , medications , certain foods , that can send your immune system into overdrive . some of these reactions can be scary . an allergy can develop into full-blown anaphylaxis , which typically brings on severe swelling , shortness of breath , and very low blood pressure . it can be deadly . the body can even have an allergic reaction to itself causing auto-immune disorders , like multiple sclerosis , lupus , and type 1 diabetes . but even non-life threatening allergy symptoms can make you miserable , so what can you do about it ? medications can help reduce the symptoms . the most common ones keep histamines from binding to your cells . these antihistamines stop the inflammation response . steroids can help dial down the immune system . another more permanent option is immunotherapy . deliberate , controlled exposure to gradually increasing amounts of an allergen can teach the immune system that it is n't dangerous after all . and if you 're really adventurous , there 's a less traditional option : intestinal parasites . when hookworms sink their teeth into the intestinal wall , they secrete chemicals that blunt the immune system . some studies suggest that hookworms can treat allergies , which may be another reason allergies are more common in industrialized countries where hookworms are few and far between . of course , you can always just wait your seasonal allergies out . the spring pollen onslaught dwindles by mid-summer , just in time for ragweed season .
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when hookworms sink their teeth into the intestinal wall , they secrete chemicals that blunt the immune system . some studies suggest that hookworms can treat allergies , which may be another reason allergies are more common in industrialized countries where hookworms are few and far between . of course , you can always just wait your seasonal allergies out .
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allergies seem to be influenced by :
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one of the great things about science is that when scientists make a discovery , it 's not always in a prescribed manner , as in , only in a laboratory under strict settings , with white lab coats and all sorts of neat science gizmos that go , `` beep ! '' in reality , the events and people involved in some of the major scientific discoveries are as weird and varied as they get . my case in point : the weird history of the cell theory . there are three parts to the cell theory . one : all organisms are composed of one or more cells . two : the cell is the basic unit of structure and organization in organisms . and three : all cells come from preexisting cells . to be honest , this all sounds incredibly boring until you dig a little deeper into how the world of microscopic organisms , and this theory came to be . it all started in the early 1600s in the netherlands , where a spectacle maker named zacharias janssen is said to have come up with the first compound microscope , along with the first telescope . both claims are often disputed , as apparently he was n't the only bored guy with a ton of glass lenses to play with at the time . despite this , the microscope soon became a hot item that every naturalist or scientist at the time wanted to play with , making it much like the ipad of its day . one such person was a fellow dutchman by the name of anton van leeuwenhoek , who heard about these microscope doohickeys , and instead of going out and buying one , he decided to make his own . and it was a strange little contraption indeed , as it looked more like a tiny paddle the size of a sunglass lens . if he had stuck two together , it probably would have made a wicked set of sunglasses that you could n't see much out of . anyhoo , once leeuwenhoek had his microscope ready , he went to town , looking at anything and everything he could with them , including the gunk on his teeth . yes , you heard right . he actually discovered bacteria by looking at dental scrapings , which , when you keep in mind that people did n't brush their teeth much -- if at all -- back then , he must have had a lovely bunch of bacteria to look at . when he wrote about his discovery , he did n't call them bacteria , as we know them today . but he called them `` animalcules , '' because they looked like little animals to him . while leeuwenhoek was staring at his teeth gunk , he was also sending letters to a scientific colleague in england , by the name of robert hooke . hooke was a guy who really loved all aspects of science , so he dabbled in a little bit of everything , including physics , chemistry and biology . thus it is hooke who we can thank for the term `` the cell , '' as he was looking at a piece of cork under his microscope , and the little chambers he saw reminded him of cells , or the rooms monks slept in in their monasteries . think college dorm rooms , but without the tvs , computers and really annoying roommates . hooke was something of an underappreciated scientist of his day -- something he brought upon himself , as he made the mistake of locking horns with one of the most famous scientists ever , sir isaac newton . remember when i said hooke dabbled in many different fields ? well , after newton published a groundbreaking book on how planets move due to gravity , hooke made the claim that newton had been inspired by hooke 's work in physics . newton , to say the least , did not like that , which sparked a tense relationship between the two that lasted even after hooke died , as quite a bit of hooke 's research -- as well as his only portrait -- was ... misplaced , due to newton . much of it was rediscovered , thankfully , after newton 's time , but not his portrait , as , sadly , no one knows what robert hooke looked like . fast-forward to the 1800s , where two german scientists discovered something that today we might find rather obvious , but helped tie together what we now know as the cell theory . the first scientist was matthias schleiden , a botanist who liked to study plants under a microscope . from his years of studying different plant species , it finally dawned on him that every single plant he had looked at were all made of cells . at the same time , on the other end of germany was theodor schwann , a scientist who not only studied slides of animal cells under the microscope and got a special type of nerve cell named after him , but also invented rebreathers for firefighters , and had a kickin ' pair of sideburns . after studying animal cells for a while , he , too , came to the conclusion that all animals were made of cells . immediately , he reached out via snail mail , as twitter had yet to be invented , to other scientists working in the same field with schleiden , who got back to him , and the two started working on the beginnings of the cell theory . a bone of contention arose between them . as for the last part of the cell theory -- that cells come from preexisting cells -- schleiden did n't exactly subscribe to that thought , as he swore cells came from free-cell formation , where they just kind of spontaneously crystallized into existence . that 's when another scientist named rudolph virchow , stepped in with research showing that cells did come from other cells , research that was actually -- hmm ... how to put it ? -- `` borrowed without permission '' from a jewish scientist by the name of robert remak , which led to two more feuding scientists . thus , from teeth gunk to torquing off newton , crystallization to schwann cells , the cell theory came to be an important part of biology today . some things we know about science today may seem boring , but how we came to know them is incredibly fascinating . so if something bores you , dig deeper . it 's probably got a really weird story behind it somewhere .
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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 ?
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can you describe a time when collaboration worked well for you ? where there ever any disagreements that led to a false assumption ( like cells spontaneously crystalizing into existence ) ?
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translator : jenny zurawell i am awele . daughter of alice , granddaughter of ruth , great-granddaughter of big momma alice and madir corine , great-great-granddaughter of anna and zitii benyen . it is my hope to find my best possible self in the service of others . now , my daddy , he used to tell me stories . my daddy , he would say , `` i want you to know who you are and where you come from . that will guide you as you discover who you must be . now , you listen to this story , you hear me , baby girl ? it 's not going to be in a book . your teacher is not going to tell it , but you need to understand who you are . '' that became a guiding principle in the stories that i wanted to tell . stories about legacy of who we are . i used to hear all the time that children are the future , but what does that cliché really mean and how are we preparing them ? so i looked for narratives about young people and the legacy that they bring as agents of change . the power that you have right now . today , march 2 , 1955 -- the story that i want to share with you comes from 1955 , march 2 . it 's about a courageous 16-year-old girl , claudette colvin . and it comes full circle today because a week ago today , in san francisco , my middle school students , they performed a program that i had written , `` agents of change , '' starting with the reenactment of plessy v. ferguson from 1892 to 1896 , moving to brown v. board and a student-led strike by barbara rose johns , jumping to claudette colvin and the montgomery bus boycott and ending in 1960 with the sit-in movement , the non-violent movement led by students . so i 'm going to share the story , and i would like to also share the work i do with it , as a case study . i paid my dime at the front of the bus , and then i ran to the back door with the rest of the colored kids so the driver would n't take off before we got on . also , well , whites do n't want us walking down the aisle next to them . when i got back on the bus , colored section was full , so , i sat in the middle section . i took the last row seat on the left , it was right by the window , was n't thinking about anything in particular . `` hey . '' i did n't know the girl next to me either , this older girl . so i just looked out the window . driver went more stops , more people were getting on , colored and white . pretty soon , no more seats were available . `` give me those seats , '' the driver called out . colored folks just started getting up . white folks started taking their seats , but i stayed seated . girl next to me and the other two across -- they stayed seated . i knew it was n't the restricted area . `` make light on your feet ! '' girl next to me got up immediately . she stood in the aisle , then the other two girls . but i told myself , this is n't the restricted area . the driver , he looked up , looked in the window , that mirror . he pulled over . a pregnant lady , mrs. hamilton , got on the bus . she ran to the back and got on , not knowing he was trying to have me relinquish my seat . and she sat right next to me . `` the two of you need to get up so i can drive on . '' `` sir , i paid my dime , i paid my fare . it 's my right , you know , my constitutional -- '' `` constitutional ? ha-ha , let me get the police . '' well he got off and he flagged down two motormen , and they came . and those motormen , they came onto the bus . looked at mrs. hamilton . `` now the two of you need to get up so the driver can drive on . '' `` sir , i paid my dime . i 'm pregnant . if i were to move right now , i 'd be very sick , sir . '' `` sir , i paid my dime too , you know , and it 's my right , my constitutional right . i 'm a citizen of the united states . you just read the 13th and 14th amendment , it 'll tell you so . i know the law . my teacher , she taught it at school . '' you see , my teacher , she taught the constitution , the bill of rights , the declaration of independence , patrick henry 's speech -- i even memorized it . my teacher , she would prick our minds , trying to see what we thinking about . she would say , `` who are you ? hmm ? who are you , sitting right here right now ? the person that people think they see from your outside ? who are you on the inside ? how you think ? how you feel ? what you believe ? would you be willing to stand up for what you believe in even if someone wants to hold you back because you 're different ? do you love your beautiful brown skin , children ? hmm ? are you american ? what does it mean to be an american ? huh ? homework tonight , write me an essay : `` what does it mean to be an american ? '' you need to know who you are , children ! '' my teacher , she would teach us history and current events . she said that 's how we can understand everything that 's going on and we can do something about it . `` sir , all i know is i hate jim crow . i also know if i ai n't got nothing worth living for , i ai n't got nothing worth dying for . so give me liberty or give me death ! ouch ! i do n't care ! take me to jail . '' they dragged her off the bus . next thing , claudette colvin was in a car seat , backseat of the police car , handcuffed through the windows . the following year , may 11 , 1956 , claudette colvin was the star witness in the federal court case browder v. gayle . her , an 18-year-old teenager and two others , women , mrs. browder . their case , browder v. gayle , went up to the supreme court . on the heels of brown v. board of education , the 14th amendment and her powerful testimony that day , the rest is history . now , why is it we do n't know this story ? the montgomery bus boycott -- we hear rosa parks , martin luther king , they will forever be lifted up . but the role women played in that movement , the role of claudette , as an up-stander , it teaches us important lessons that challenge us today . what does it mean to be a participant ? a responsible citizen in a democracy ? and lessons of courage and of faith ? so i find freedom movement history that includes young people so that they can explore these big ideas of identity , your chosen identity , and the imposed identity . what does membership in society mean ? who has it ? how do we make amends ? race and violence in america , as well as participatory citizenship . so these stories allow me to have conversations , to speak the unspeakable , that many are afraid to have . once in eugene , oregon , a young , blond-haired , blue-eyed boy , middle schooler , at the end of a performance in the dialogue said , `` but ms. awele , racism 's over , right ? '' and not wanting to answer for him , i said , `` turn to the person sitting next to you . see if you can come up with evidence . '' and i gave them four minutes to talk . soon , they began to tell stories , evidence of racism in their community . a girl wrote to me , a high school student in san francisco : `` i was going to skip school but then i heard we had an assembly , so i came . and after listening to the students talk and seeing your performance , i thought i should organize my friends and we should go down to a board meeting and tell them that want to have advanced classes for a through g requirements . '' so , i tell you this story today in honor of the legacy of young people that have come before , so that they will have guideposts and signs to be the change that they want to see in this world , as claudette colvin was . because she struck down the constitutionality of segregated seats in montgomery , alabama . thank you . ( applause ) thank you . ( applause )
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so these stories allow me to have conversations , to speak the unspeakable , that many are afraid to have . once in eugene , oregon , a young , blond-haired , blue-eyed boy , middle schooler , at the end of a performance in the dialogue said , `` but ms. awele , racism 's over , right ? '' and not wanting to answer for him , i said , `` turn to the person sitting next to you .
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what startling question did a boy in eugene , oregon ask awele makeba ?
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translator : tom carter reviewer : bedirhan cinar most people have heard of the electoral college during presidential election years . but what exactly is the electoral college ? simply said , it is a group of people appointed by each state who formally elect the president and vice president of the united states . to understand how this process began and how it continues today , we can look at the constitution of the united states : article two , section one , clause two of the constitution . it specifies how many electors each state is entitled to have . since 1964 , there have been 538 electors in each presidential election . how do they decide on the number 538 ? well , the number of electors is equal to the total voting membership of the united states congress . 435 representatives , plus 100 senators , and 3 electors from the district of columbia . essentially , the democratic candidate and republican candidate are each trying to add up the electors in every state so that they surpass 270 electoral votes , or just over half the 538 votes , and win the presidency . so how do states even get electoral votes ? each state receives a particular number of electors based on population size . the census is conducted every 10 years , so every time the census happens , states might gain or lose a few electoral votes . let 's say you 're a voter in california , a state with 55 electoral votes . if your candidate wins in california , they get all 55 of the state 's electoral votes . if your candidate loses , they get none . this is why many presidential candidates want to win states like texas , florida , and new york . if you currently add up the electoral votes of those three states , you would have 96 electoral votes . even if a candidate won north dakota , south dakota , montana , wyoming , vermont , new hampshire . connecticut and west virginia , they would only gain 31 electoral votes total from those eight states . here is where it can get a little tricky . on a rare occasion , like in the year 2000 , someone can win the popular vote but fail to gain 270 electoral votes . this means that the winner may have won and collected their electoral votes by small margins , winning just enough states with just enough electoral votes , but the losing candidate may have captured large voter margins in the remaining states . if this is the case , the very large margins secured by the losing candidate in the other states would add up to over 50 % of the ballots cast nationally . therefore , the losing candidate may have gained more than 50 % of the ballots cast by voters , but failed to gain 270 of the electoral votes . some critics of the electoral college argue the system gives an unfair advantage to states with large numbers of electoral votes . think of it this way . it is possible for a candidate to not get a single person 's vote -- not one vote -- in 39 states , or the district of columbia , yet be elected president by winning the popular vote in just 11 of these 12 states : california , new york , texas , florida , pennsylvania , illinois , ohio , michigan , new jersey , north carolina , georgia or virginia . this is why both parties pay attention to these states . however , others argue that the electoral college protects small states such as rhode island , vermont and new hampshire , and even geographically large states with small populations like alaska , wyoming and the dakotas . that 's because a candidate ca n't completely ignore small states , because in a close election , every electoral vote counts . there are certain states that have a long history of voting for a particular party . these are known as `` safe states . '' for the past four election cycles -- in 1996 , 2000 , 2004 and 2008 -- democrats could count on states like oregon , maryland , michigan and massachusetts , whereas the republicans could count on states like mississippi , alabama , kansas and idaho . states that are teetering between between parties are called `` swing states . '' in the past four election cycles , ohio and florida have been swing states , twice providing electoral votes for a democratic candidate , and twice providing electoral votes for a republican candidate . think about it . do you live in a safe state ? if so , is it a democratic or republican safe state ? do you live in a swing state ? are your neighboring states swing or safe ? is the population in your state increasing or decreasing ? and do not forget , when you are watching the electoral returns on election night every four years and the big map of the united states is on the screen , know that the magic number is 270 and start adding .
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translator : tom carter reviewer : bedirhan cinar most people have heard of the electoral college during presidential election years . but what exactly is the electoral college ? simply said , it is a group of people appointed by each state who formally elect the president and vice president of the united states .
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what is the electoral college ?
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translator : andrea mcdonough reviewer : jessica ruby nowadays , we take curiosity for granted . we believe that if we put in the hard work , we might one day stand before the pyramids , discover a new species of flower , or even go to the moon . but , in the 18th and 19th century , female eyes gazed out windows at a world they were unlikely to ever explore . life for women in the time of queen victoria was largely relegated to house chores and gossip . and , although they devoured books on exotic travel , most would never would leave the places in which they were born . however , there were a few victorian women , who , through privilege , endurance , and not taking `` no '' for an answer , did set sail for wilder shores . in 1860 , marianne north , an amateur gardener and painter , crossed the ocean to america with letters of introduction , an easel , and a love of flowers . she went on to travel to jamaica , peru , japan , india , australia . in fact , she went to every continent except antarctica in pursuit of new flowers to paint . `` i was overwhelmed with the amount of subjects to be painted , '' she wrote . `` the hills were marvelously blue , piled one over the other beyond them . i never saw such abundance of pure color . '' with no planes or automobiles and rarely a paved street , north rode donkeys , scaled cliffs , and crossed swamps to reach the plants she wanted . and all this in the customary dress of her day , floor-length gowns . as photography had not yet been perfected , marianne 's paintings gave botanists back in europe their first glimpses of some of the world 's most unusual plants , like the giant pitcher plant of borneo , the african torch lily , and the many other species named for her as she was the first european to catalog them in the wild . meanwhile , back in london , miss mary kingsley was the sheltered daughter of a traveling doctor who loved hearing her father 's tales of native customs in africa . midway through writing a book on the subject , her father fell ill and died . so , kingsley decided she would finish the book for him . peers of her father advised her not to go , showing her maps of tropical diseases , but she went anyhow , landing in modern-day sierra leone in 1896 with two large suitcases and a phrase book . traveling into the jungle , she was able to confirm the existence of a then-mythical creature , the gorilla . she recalls fighting with crocodiles , being caught in a tornado , and tickling a hippopotamus with her umbrella so that he 'd leave the side of her canoe . falling into a spiky pit , she was saved from harm by her thick petticoat . `` a good snake properly cooked is one of the best meals one gets out here , '' she wrote . think indiana jones was resourceful ? kingsley could out-survive him any day ! but when it comes to breaking rules , perhaps no female traveler was as daring as alexandra david-neel . alexandra , who had studied eastern religions at home in france , wanted desperately to prove herself to parisian scholars of the day , all of whom were men . she decided the only way to be taken seriously was to visit the fabled city of lhasa in the mountains of tibet . `` people will have to say , 'this woman lived among the things she 's talking about . she touched them and she saw them alive , ' '' she wrote . when she arrived at the border from india , she was forbidden to cross . so , she disguised herself as a tibetan man . dressed in a yak fur coat and a necklace of carved skulls , she hiked through the barren himilayas all the way to lhasa , where she was subsequently arrested . she learned that the harder the journey , the better the story , and went on to write many books on tibetan religion , which not only made a splash back in paris but remain important today . these brave women , and others like them , went all over the world to prove that the desire to see for oneself not only changes the course of human knowledge , it changes the very idea of what is possible . they used the power of curiosity to try and understand the viewpoints and peculiarities of other places , perhaps because they , themselves , were seen as so unusual in their own societies . but their journeys revealed to them something more than the ways of foreign lands , they revealed something only they , themselves , could find : a sense of their own self .
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but , in the 18th and 19th century , female eyes gazed out windows at a world they were unlikely to ever explore . life for women in the time of queen victoria was largely relegated to house chores and gossip . and , although they devoured books on exotic travel , most would never would leave the places in which they were born .
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women ’ s fashion of the time was quite restrictive . what fashionable item helped mary kingsley when she fell into a pit of thorns ?
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studies have shown that taking vitamins is good for your health and bad for your health . that newly discovered herb can improve your memory or destroy your liver . headlines proclaim a promising new cancer treatment and never mention it again . on a daily basis , we are bombarded with attention-grabbing news , backed up by scientific studies , but what are these studies ? how are they performed ? and how do we know whether they 're reliable ? when it comes to dietary or medical information , the first thing to remember is that while studies on animals or individual cells can point the way towards further research , the only way to know how something will affect humans is through a study involving human subjects . and when it comes to human studies , the scientific gold standard is the randomized clinical trial , or rct . the key to rcts is that the subjects are randomly assigned to their study groups . they are often blinded to make them more rigorous . this process attempts to ensure that the only difference between the groups is the one the researchers are attempting to study . for example , when testing a new headache medication , a large pool of people with headaches would be randomly divided into two groups , one receiving the medication and another receiving a placebo . with proper randomization , the only significant overall difference between the two groups will be whether or not they received the medication , rather than other differences that could affect results . randomized clinical trials are incredible tools , and , in fact , the us food and drug administration often requires at least two to be conducted before a new drug can be marketed . but the problem is that an rct is not possible in many cases , either because it 's not practical or would require too many volunteers . in such cases , scientists use an epidemiological study , which simply observes people going about their usual behavior , rather than randomly assigning active participants to control invariable groups . let 's say we wanted to study whether an herbal ingredient on the market causes nausea . rather than deliberately giving people something that might make them nauseated , we would find those who already take the ingredient in their everyday lives . this group is called the cohort . we would also need a comparison group of people who do not have exposure to the ingredient . and we would then compare statistics . if the rate of nausea is higher in the herbal cohort , it suggests an association between the herbal supplement and nausea . epidemiological studies are great tools to study the health effects of almost anything , without directly interfering in people 's lives or assigning them to potentially dangerous exposures . so , why ca n't we rely on these studies to establish causal relationships between substances and their effects on health ? the problem is that even the best conducted epidemiological studies have inherent flaws . precisely because the test subjects are not randomly assigned to their groups . for example , if the cohort in our herbal study consisted of people who took the supplement for health reasons , they may have already had higher rates of nausea than the other people in the sample . or the cohort group could 've been composed of people who shop at health food stores and have different diets or better access to healthcare . these factors that can affect results , in addition to the factor being studied , are known as confounding variables . these two major pitfalls , combined with more general dangers , such as conflicts of interest or selective use of data , can make the findings of any particular epidemiological study suspect , and a good study must go out of its way to prove that its authors have taken steps to eliminate these types of errors . but even when this has been done , the very nature of epidemiological studies , which examine differences between preexisting groups , rather than deliberately inducing changes within the same individuals , means that a single study can only demonstrate a correlation between a substance and a health outcome , rather than a true cause and effect relationship . at the end of the day , epidemiological studies have served as excellent guides to public health , alerting us to critical health hazards , such as smoking , asbestos , lead , and many more . but these were demonstrated through multiple , well-conducted epidemiological studies , all pointing in the same direction . so , the next time you see a headline about a new miracle cure or the terrible danger posed by an everyday substance , try to learn more about the original study and the limitations inherent in any epidemiological study or clinical trial before jumping to conclusions .
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when it comes to dietary or medical information , the first thing to remember is that while studies on animals or individual cells can point the way towards further research , the only way to know how something will affect humans is through a study involving human subjects . and when it comes to human studies , the scientific gold standard is the randomized clinical trial , or rct . the key to rcts is that the subjects are randomly assigned to their study groups .
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randomized clinical trials are considered the gold standard in determining cause and effect relationships related to human health outcomes .
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long before descartes famously declared , `` i think , therefore i am , '' and long after that , scientists and philosophers alike have puzzled over what they call the mind-body problem . is the mind some separate , non-material entity piloting a machine of flesh ? or if it 's just a particularly elusive part of our physical body , how can it translate the input of our animal senses into the seemingly non-physical experiences that we call thoughts ? but though the answers have been debated endlessly , new research suggests that part of the problem lies in how we pose the question in the first place , assuming a distinction between our sensory perception and our ideas that may not really be there . the traditional model of our mental function has been that the senses provide separate data to our brain which are then translated into the appropriate mental phenomena : visual images into trees , auditory experiences into bird songs , and so on . but occasionally , we have come across people whose senses seem to mingle together , allowing them to hear colors , or taste sounds . until recently , the common understanding was that this phenomenon , called synesthesia , was a direct connection between the parts of the brain responsible for sensory stimuli such as seeing the color yellow immediately upon hearing the tone of b flat . but newer studies have shown that synesthesia is actually mediated through our understanding of the shapes , colors and sounds that our senses apprehend . in order for the cross-sensory experiences to occur , the higher level ideas and concepts that our minds associate with the sensory input must be activated . for example , this shape can be seen as either the letter `` s '' or the number `` 5 , '' and synesthetes associate each with different colors or sounds based on how they interpret it despite the purely visual stimulus remaining identical . in another study , synesthetes created novel color associations for unfamiliar letters after learning what the letters were . so because it relies on a connection between ideas and senses , this mental phenomenon underlying synesthesia is known as ideasthesia . synesthesia only occurs in some people , although it may be more common than previously thought . but ideasthesia itself is a fundamental part of our lives . virtually all of us recognize the color red as warm and blue as cold . many would agree that bright colors , italic letters and thin lines are high-pitched , while earth tones are low-pitched . and while many of these associations are acquired through cultural exposure , others have been demonstrated even in infants and apes , suggesting that at least some associations are inborn . when asked to choose between two possible names for these shapes , people from entirely different cultural and language backgrounds overwhelmingly agree that `` kiki '' is the spiky star , while `` bouba '' is the rounded blob , both because of the sounds themselves and the shapes our mouths make to produce them . and this leads to even more associations within a rich semantic network . kiki is described as nervous and clever , while bouba is perceived as lazy and slow . what all of this suggests is that our everyday experiences of colors , sounds and other stimuli do not live on separate sensory islands but are organized in a network of associations similar to our language network . this is what enables us to understand metaphors even though they make no logical sense , such as the comparison of snow to a white blanket , based on the shared sensations of softness and lightness . ideasthesia may even be crucial to art , which relies on a synthesis of the conceptual and the emotional . in great art , idea and aesthesia enhance each other , whether it 's song lyrics combining perfectly with a melody , the thematic content of a painting heightened by its use of colors and brushstrokes , or the well constructed plot of a novel conveyed through perfectly crafted sentences . most importantly , the network of associations formed by ideasethesia may not only be similar to our linguistic network but may , in fact , be an integral part of it . rather than the traditional view , where our senses first capture a collection of colors and shapes , or some vibrations in the air , and our mind then classifies them as a tree or a siren , ideasthesia suggests that the two processes occur simultaneously . our sensory perceptions are shaped by our conceptual understanding of the world . and the two are so connected that one can not exist without the other . if this model suggested by ideasthesia is accurate , it may have major implications for some of the biggest scientific and philosophical issues surrounding the study of mind . without a preexisting concept of self , descartes would not have had an `` i '' to attribute the thinking to . and without a preexisting network of interrelated and distinct concepts , our sensory experience of the world would be an undifferentiated mass rather than the discrete objects we actually apprehend . for science , the task is to find where this network lies , how it is formed , and how it interacts with external stimuli . for philosophy , the challenge is to rethink what this new model of consciousness means for our understanding of our selves and our relation to the world around us .
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this is what enables us to understand metaphors even though they make no logical sense , such as the comparison of snow to a white blanket , based on the shared sensations of softness and lightness . ideasthesia may even be crucial to art , which relies on a synthesis of the conceptual and the emotional . in great art , idea and aesthesia enhance each other , whether it 's song lyrics combining perfectly with a melody , the thematic content of a painting heightened by its use of colors and brushstrokes , or the well constructed plot of a novel conveyed through perfectly crafted sentences .
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in your own appreciation of art , can you find examples in which the emotional experiences that the artwork evoked were combined with your understanding of the meaning of the work ?
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a close encounter with a man-eating giant , a sorceress who turns men into pigs , a long-lost king taking back his throne . on their own , any of these make great stories , but each is just one episode in the `` odyssey , '' a 12,000-line poem spanning years of ancient greek history , myth , and legend . how do we make sense of such a massive text that comes from and tells of a world so far away ? the fact that we can read the `` odyssey '' at all is pretty incredible , as it was composed before the greek alphabet appeared in the 8th century bce . it was made for listeners rather than readers , and was performed by oral poets called rhapsodes . tradition identifies its author as a blind man named homer . but no one definitively knows whether he was real or legendary . the earliest mentions of him occur centuries after his era . and the poems attributed to him seem to have been changed and rearranged many times by multiple authors before finally being written down in their current form . in fact , the word rhapsode means stitching together , as these poets combined existing stories , jokes , myths , and songs into a single narrative . to recite these massive epics live , rhapsodes employed a steady meter , along with mnemonic devices , like repetition of memorized passages or set pieces . these included descriptions of scenery and lists of characters , and helped the rhapsode keep their place in the narrative , just as the chorus or bridge of a song helps us to remember the next verses . because most of the tales were familiar to the audience , it was common to hear the sections of the poem out of order . at some point , the order became set in stone and the story was locked into place as the one we read today . but since the world has changed a bit in the last several thousand years , it helps to have some background before jumping in . the `` odyssey '' itself is a sequel to homer 's other famous epic , the `` iliad , '' which tells the story of the trojan war . if there 's one major theme uniting both poems , it 's this : do not , under any circumstances , incur the wrath of the gods . the greek pantheon is a dangerous mix of divine power and human insecurity , prone to jealousy and grudges of epic proportions . and many of the problems faced by humans in the poems are caused by their hubris , or excessive pride in believing themselves superior to the gods . the desire to please the gods was so great that the ancient greeks traditionally welcomed all strangers into their homes with generosity for fear that the strangers might be gods in disguise . this ancient code of hospitality was called xenia . it involved hosts providing their guests with safety , food , and comfort , and the guests returning the favor with courtesy and gifts if they had them . xenia has a significant role in the `` odyssey , '' where odysseus in his wanderings is the perpetual guest , while in his absence , his clever wife penelope plays non-stop host . the `` odyssey '' recounts all of odysseus 's years of travel , but the narrative begins in medias res in the middle of things . ten years after the trojan war , we find our hero trapped on an island , still far from his native ithaca and the family he has n't seen for 20 years . because he 's angered the sea god poseidon by blinding his son , a cyclops , odysseus 's passage home has been fraught with mishap after mishap . with trouble brewing at home and gods discussing his fate , odysseus begins the account of those missing years to his hosts . one of the most fascinating things about the `` odyssey '' is the gap between how little we know about its time period and the wealth of detail the text itself contains . historians , linguists , and archeologists have spent centuries searching for the ruins of troy and identifying which islands odysseus visited . just like its hero , the 24-book epic has made its own long journey through centuries of myth and history to tell us its incredible story today .
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in fact , the word rhapsode means stitching together , as these poets combined existing stories , jokes , myths , and songs into a single narrative . to recite these massive epics live , rhapsodes employed a steady meter , along with mnemonic devices , like repetition of memorized passages or set pieces . these included descriptions of scenery and lists of characters , and helped the rhapsode keep their place in the narrative , just as the chorus or bridge of a song helps us to remember the next verses .
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which of the following elements helped the rhapsodes remember and recite the poem ?
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in 1800 , the explorer alexander von humboldt witnessed a swarm of electric eels leap out of the water to defend themselves against oncoming horses . most people thought the story so unusual that humboldt made it up . but fish using electricity is more common than you might think ; and yes , electric eels are a type of fish . underwater , where light is scarce , electrical signals offer ways to communicate , navigate , and find—plus , in rare cases , stun—prey . nearly 350 species of fish have specialized anatomical structures that generate and detect electrical signals . these fish are divided into two groups , depending on how much electricity they produce . scientists call the first group the weakly electric fish . structures near their tails called electric organs produce up to a volt of electricity , about two-thirds as much as a aa battery . how does this work ? the fish 's brain sends a signal through its nervous system to the electric organ , which is filled with stacks of hundreds or thousands of disc-shaped cells called electrocytes . normally , electrocytes pump out sodium and potassium ions to maintain a positive charge outside and negative charge inside . but when the nerve signal arrives at the electrocyte , it prompts the ion gates to open . positively charged ions flow back in . now , one face of the electrocyte is negatively charged outside and positively charged inside . but the far side has the opposite charge pattern . these alternating charges can drive a current , turning the electrocyte into a biological battery . the key to these fish 's powers is that nerve signals are coordinated to arrive at each cell at exactly the same time . that makes the stacks of electrocytes act like thousands of batteries in series . the tiny charges from each one add up to an electrical field that can travel several meters . cells called electroreceptors buried in the skin allow the fish to constantly sense this field and the changes to it caused by the surroundings or other fish . the peter ’ s elephantnose fish , for example , has an elongated chin called a schnauzenorgan that 's riddled in electroreceptors . that allows it to intercept signals from other fish , judge distances , detect the shape and size of nearby objects , and even determine whether a buried insect is dead or alive . but the elephantnose and other weakly electric fish do n't produce enough electricity to attack their prey . that ability belongs to the strongly electric fish , of which there are only a handful of species . the most powerful strongly electric fish is the electric knife fish , more commonly known as the electric eel . three electric organs span almost its entire two-meter body . like the weakly electric fish , the electric eel uses its signals to navigate and communicate , but it reserves its strongest electric discharges for hunting using a two-phased attack that susses out and then incapacitates its prey . first , it emits two or three strong pulses , as much as 600 volts . these stimulate the prey 's muscles , sending it into spasms and generating waves that reveal its hiding place . then , a volley of fast , high-voltage discharges causes even more intense muscle contractions . the electric eel can also curl up so that the electric fields generated at each end of the electric organ overlap . the electrical storm eventually exhausts and immobilizes the prey , and the electric eel can swallow its meal alive . the other two strongly electric fish are the electric catfish , which can unleash 350 volts with an electric organ that occupies most of its torso , and the electric ray , with kidney-shaped electric organs on either side of its head that produce as much as 220 volts . there is one mystery in the world of electric fish : why do n't they electrocute themselves ? it may be that the size of strongly electric fish allows them to withstand their own shocks , or that the current passes out of their bodies too quickly . some scientists think that special proteins may shield the electric organs , but the truth is , this is one mystery science still has n't illuminated .
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then , a volley of fast , high-voltage discharges causes even more intense muscle contractions . the electric eel can also curl up so that the electric fields generated at each end of the electric organ overlap . the electrical storm eventually exhausts and immobilizes the prey , and the electric eel can swallow its meal alive .
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how do the pulses generated by an electric eel affect its prey ?
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think back to a really vivid memory . got it ? okay , now try to remember what you had for lunch three weeks ago . that second memory probably is n't as strong , but why not ? why do we remember some things , and not others ? and why do memories eventually fade ? let 's look at how memories form in the first place . when you experience something , like dialing a phone number , the experience is converted into a pulse of electrical energy that zips along a network of neurons . information first lands in short term memory , where it 's available from anywhere from a few seconds to a couple of minutes . it 's then transferred to long-term memory through areas such as the hippocampus , and finally to several storage regions across the brain . neurons throughout the brain communicate at dedicated sites called synapses using specialized neurotransmitters . if two neurons communicate repeatedly , a remarkable thing happens : the efficiency of communication between them increases . this process , called long term potentiation , is considered to be a mechanism by which memories are stored long-term , but how do some memories get lost ? age is one factor . as we get older , synapses begin to falter and weaken , affecting how easily we can retrieve memories . scientists have several theories about what 's behind this deterioration , from actual brain shrinkage , the hippocampus loses 5 % of its neurons every decade for a total loss of 20 % by the time you 're 80 years old to the drop in the production of neurotransmitters , like acetylcholine , which is vital to learning and memory . these changes seem to affect how people retrieve stored information . age also affects our memory-making abilities . memories are encoded most strongly when we 're paying attention , when we 're deeply engaged , and when information is meaningful to us . mental and physical health problems , which tend to increase as we age , interfere with our ability to pay attention , and thus act as memory thieves . another leading cause of memory problems is chronic stress . when we 're constantly overloaded with work and personal responsibilites , our bodies are on hyperalert . this response has evolved from the physiological mechanism designed to make sure we can survive in a crisis . stress chemicals help mobilize energy and increase alertness . however , with chronic stress our bodies become flooded with these chemicals , resulting in a loss of brain cells and an inability to form new ones , which affects our ability to retain new information . depression is another culprit . people who are depressed are 40 % more likely to develop memory problems . low levels of serotonin , a neurotransmitter connected to arousal , may make depressed individuals less attentive to new information . dwelling on sad events in the past , another symptom of depression , makes it difficult to pay attention to the present , affecting the ability to store short-term memories . isolation , which is tied to depression , is another memory thief . a study by the harvard school of public health found that older people with high levels of social integration had a slower rate of memory decline over a six-year period . the exact reason remains unclear , but experts suspect that social interaction gives our brain a mental workout . just like muscle strength , we have to use our brain or risk losing it . but do n't despair . there are several steps you can take to aid your brain in preserving your memories . make sure you keep physically active . increased blood flow to the brain is helpful . and eat well . your brain needs all the right nutrients to keep functioning correctly . and finally , give your brain a workout . exposing your brain to challenges , like learning a new language , is one of the best defenses for keeping your memories intact .
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let 's look at how memories form in the first place . when you experience something , like dialing a phone number , the experience is converted into a pulse of electrical energy that zips along a network of neurons . information first lands in short term memory , where it 's available from anywhere from a few seconds to a couple of minutes .
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you look up a friends phone number , however when you call the number , the line is busy . when you start to dial the number again at a later time , you realize you no longer remember it . this experience probably occurred because the phone number was only temporarily stored in your :
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steel and plastic . these two materials are essential to so much of our infrastructure and technology , and they have a complementary set of strengths and weaknesses . steel is strong and hard , but difficult to shape intricately . while plastic can take on just about any form , it 's weak and soft . so would n't it be nice if there were one material as strong as the strongest steel and as shapeable as plastic ? well , a lot of scientists and technologists are getting excited about a relatively recent invention called metallic glass with both of those properties , and more . metallic glasses look shiny and opaque , like metals , and also like metals , they conduct heat and electricity . but they 're way stronger than most metals , which means they can withstand a lot of force without getting bent or dented , making ultrasharp scalpels , and ultrastrong electronics cases , hinges , screws ; the list goes on . metallic glasses also have an incredible ability to store and release elastic energy , which makes them perfect for sports equipment , like tennis racquets , golf clubs , and skis . they 're resistant to corrosion , and can be cast into complex shapes with mirror-like surfaces in a single molding step . despite their strength at room temperature , if you go up a few hundred degrees celsius , they soften significantly , and can be deformed into any shape you like . cool them back down , and they regain the strength . so where do all of these wondrous attributes come from ? in essence , they have to do with metallic glass ' unique atomic structure . most metals are crystalline as solids . that means that if you zoomed in close enough to see the individual atoms , they 'd be neatly lined up in an orderly , repeating pattern that extends throughout the whole material . ice is crystalline , and so are diamonds , and salt . if you heat these materials up enough and melt them , the atoms can jiggle freely and move randomly , but when you cool them back down , the atoms reorganize themselves , reestablishing the crystal . but what if you could cool a molten metal so fast that the atoms could n't find their places again , so that the material was solid , but with the chaotic , amorphous internal structure of a liquid ? that 's metallic glass . this structure has the added benefit of lacking the grain boundaries that most metals have . those are weak spots where the material is more susceptible to scratches or corrosion . the first metallic glass was made in 1960 from gold and silicon . it was n't easy to make . because metal atoms crystallize so rapidly , scientists had to cool the alloy down incredibly fast , a million degrees kelvin per second , by shooting tiny droplets at cold copper plates , or spinning ultrathin ribbons . at that time , metallic glasses could only be tens or hundreds of microns thick , which was too thin for most practical applications . but since then , scientists have figured out that if you blend several metals that mix with each other freely , but ca n't easily crystallize together , usually because they have very different atomic sizes , the mixture crystallizes much more slowly . that means you do n't have to cool it down as fast , so the material can be thicker , centimeters instead of micrometers . these materials are called bulk metallic glasses , or bmgs . now there are hundreds of different bmgs , so why are n't all of our bridges and cars made out of them ? many of the bmgs currently available are made from expensive metals , like palladium and zirconium , and they have to be really pure because any impurities can cause crystallization . so a bmg skyscraper or space shuttle would be astronomically expensive . and despite their strength , they 're not yet tough enough for load-bearing applications . when the stresses get high , they can fracture without warning , which is n't ideal for , say , a bridge . but when engineers figure out how to make bmgs from cheaper metals , and how to make them even tougher , for these super materials , the sky 's the limit .
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many of the bmgs currently available are made from expensive metals , like palladium and zirconium , and they have to be really pure because any impurities can cause crystallization . so a bmg skyscraper or space shuttle would be astronomically expensive . and despite their strength , they 're not yet tough enough for load-bearing applications .
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what advantage does a bmg golf club head have over its traditional counterpart ?
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the stereotype that men are smarter than women has a long history , but in the battle of the sexes , who actually has the superior intellect when it comes down to it ? are boys smarter than girls ? early studies show that male brains are 8 to 13 percent larger in volume than female brains , however this has been since attributed to differences in body size . women 's brains have more gyrofication or brain folding , and as a result , a greater cortical surface area . besides , bigger is n't always better . sperm whales , elephants and dolphins all have larger brains than humans , and while they are smart , their cognitive abilities are less than our own . there are other structural differences , though , like males having more connections within hemispheres , while women have more connections between hemispheres . but overall , mri brain imaging shows significant overlap in the physical structure between the sexes . after studying 14 hundred brains and comparing the sexes , researchers found that mostly all men and woman show a mosaic of female and male typical structures in the brain . this study also evaluted gender stereotypical behaviours . like how video games are often considered male behaviour while scrapbooking is female and the results found that 0.1 % of test subjects displayed only male or only female typical behaviours . tests on intelligence find similar results with major iq studies showing neglible , or no sex differences in general intelligence but do show women having stronger verbal abilities while men show stronger visual-spatial abilities . interestingly , studies show more male variance in tests with their scores being both the worst and the best . one meta analysis of 22 studies did fiund men to be 3.3 to 5.5 iq points above women but this study has been called into question by academics who found the methodology flawed . in academic performance of language , math and science , women consistently received better grade in 70 % of nations . but on sat testing in the u.s. men scored 33 points higher in math and science . other tests like the program for international student assessment showed both sexes performing equally in several countries with girls performing better in some like iceland suggesting cultural and environmental differences and not necessarily biological differences at play . but research has found that stereotypes about womens performance actually impact how well they do . when told that a particular math test had significant gender differences , women performed significantly worse than their male peers . while women who were told there was no difference , scored the same . this phenomenom is known as the stereotype threat . even google search data shows that parents 2.5 times more likely to search is my son gifted than is my daughter gifted ? despite 11 % more girls in gifted programs in america . and girls pick up on these bias as early as 6 years old . when told a story at age 5 about a person who is really really smart both boys and girls associate intelligence with there own gender but by age 6 both girls and boys picked a male character as the smartest . in a similar experiment kids were asked if they wanted to play a game for people who are really really smart and again at age 5 both sexes wanted to play but by age 6 , girls had decided these games were n't for them . and though women do strive to work in stem fields studies show they face barriers . in a double blind study science faculty from research universities rated applications for a lab manager position . what they did n't know is that the applications were randomly assigned either male or female names . as a result , faculty perceived the male applicant names to be significantly more competent , hireable and deserving of mentoring even though the applications with female names were identical . males were also offered higher starting salaries , an average of 30,000 versus the females 26,000 . though these studies produce a sobering reality research does point to growing equality between the sexes with passing decades and education and in spite of these barriers women continue to contribute to our collective scientific knowledge . rosalind franklin allowed us to understand our own dna , katherine johnson helped apollo 11 land on the moon and this year maryam mirzakhani is the first women to win a nobel prize for mathematics . fellow mathematician izabella laba said `` mirzakhan 's selection does exactly nothing to convince me that women are capable of doing mathematical research at the same level of men . i have never had any doubt about that in the first place.. what i take from it instead is that we as a society , men and women alike , are becoming better at encouraging and nurturing mathematical talent in women , and more capable of reconizing excellence in women 's work . '' to learn more we asked the women at asap science to speak personally about their experiences growing up and give insight about how they navigate the societal pressures of being a woman . click on the screen or the link in the description to check out that video and subscribe for more weekly science videos every thursday .
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sperm whales , elephants and dolphins all have larger brains than humans , and while they are smart , their cognitive abilities are less than our own . there are other structural differences , though , like males having more connections within hemispheres , while women have more connections between hemispheres . but overall , mri brain imaging shows significant overlap in the physical structure between the sexes .
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males have more connections _____ hemispheres , whereas women have more connections _____ hemispheres .
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how and when did our universe begin ? how did it get to look like this ? how will it end ? humans have been discussing these questions for as long as they 've been around without ever reaching much agreement . today , cosmologists are working hard to find the answers . but how can anyone hope to find concrete answers to such profound questions ? and how is it possible to explore and study something as huge as the universe , most of which we 'll never be able to reach ? the answer is light . and although light from distant parts of the universe can take billions of years to reach us , it carries six unique messages that , when put together , can disclose an amazing amount of information to astronomers who know how to look for it . just as sunlight can be split up into the familiar rainbow , splitting the light from distant objects exposes different patterns of colors depending on its source . this distinctive light barcode can reveal not only an object 's composition , but also the temperature and pressure of its constituent parts . there 's even more we can discover from light . if you 've ever stood on a train platform , you might have noticed that the train sounds different depending on its direction with the pitch ascending when it approaches you and descending when it speeds away . but this is n't because the train conductor is practicing for a second career . rather , it 's because of something called the doppler effect where sound waves generated by an approaching object are compressed , while those from a receding object are stretched . but what has this to do with astronomy ? sound does not travel through a vacuum . in space , no one can you hear you scream ! but the same doppler effect applies to light whose source is moving at exceptional speed . if it 's moving towards us , the shorter wavelength will make the light appear to be bluer . while light from a source that 's moving away will have a longer wavelength , shifting towards red . so by analyzing the color pattern in the doppler shift of the light from any object observed with a telescope , we can learn what it 's made of , how hot it is and how much pressure it 's under , as well as whether it 's moving , in what direction and how fast . and these six measurements , like six points of light , reveal the history of the universe . the first person to study the light from distant galaxies was edwin hubble , and the light he observed was redshifted . the distant galaxies were all moving away from us , and the further away the were , the faster they were receding . hubble had discovered our universe is expanding , providing the first evidence for the big bang theory . along with the idea that the visible universe has been constantly expanding from a densely packed single point , one of this theory 's most important predictions is that the early universe consisted of just two gases : hydrogen and helium , in a ratio of three to one . and this prediction can also be tested with light . if we observe the light from a remote , quiet region of the universe and split it , we do indeed find the signatures of the two gases in just those proportions . another triumph for the big bang . however , many puzzles remain . although we know the visible universe is expanding , gravity should be applying the brakes . but recent measurements of light from distant dying stars show us that they 're farther away than predicted . so the expansion of the universe is actually accelerating . something appears to be pushing it , and many scientists believe that something is dark energy , making up over 2/3 of the universe and slowly tearing it apart . our knowledge of the behavior of matter and the precision of our instruments means that simply observing distant stars can tell us more about the universe than we ever thought possible . but there are other mysteries , like the nature of dark energy upon which we have yet to shed light .
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how and when did our universe begin ? how did it get to look like this ?
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how have improvements in satellites and ground and space based telescopes improved our understanding of the universe ?
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every year , about 1,000 new words are added to the oxford english dictionary . where do they come from , and how do they make it into our everyday lives ? with over 170,000 words currently in use in the english language , it might seem we already have plenty . yet , as our world changes , new ideas and inventions spring forth , and science progresses , our existing words leave gaps in what we want to express and we fill those gaps in several ingenious , practical , and occasionally peculiar ways . one way is to absorb a word from another language . english has borrowed so many words over its history that nearly half of its vocabulary comes directly from other languages . sometimes , this is simply because the thing the word describes was borrowed itself . rome and france brought legal and religious concepts , like altar and jury , to medieval england , while trade brought crops and cuisine , like arabic coffee , italian spaghetti , and indian curry . but sometimes , another language has just the right word for a complex idea or emotion , like naïveté machismo , or schadenfreude . scientists also use classical languages to name new concepts . clone , for example , was derived from the ancient greek word for twig to describe creating a new plant from a piece of the old . and today , the process works both ways , with english lending words like software to languages all over the world . another popular way to fill a vocabulary gap is by combining existing words that each convey part of the new concept . this can be done by combining two whole words into a compound word , like airport or starfish , or by clipping and blending parts of words together , like spork , brunch , or internet . and unlike borrowings from other languages , these can often be understood the first time you hear them . and sometimes a new word is n't new at all . obsolete words gain new life by adopting new meanings . villain originally meant a peasant farmer , but in a twist of aristocratic snobbery came to mean someone not bound by the knightly code of chivalry and , therefore , a bad person . a geek went from being a carnival performer to any strange person to a specific type of awkward genius . and other times , words come to mean their opposite through irony , metaphor , or misuse , like when sick or wicked are used to describe something literally amazing . but if words can be formed in all these ways , why do some become mainstream while others fall out of use or never catch on in the first place ? sometimes , the answer is simple , as when scientists or companies give an official name to a new discovery or technology . and some countries have language academies to make the decisions . but for the most part , official sources like dictionaries only document current usage . new words do n't originate from above , but from ordinary people spreading words that hit the right combination of useful and catchy . take the word meme , coined in the 1970s by sociobiologist richard dawkins from the ancient greek for imitation . he used it to describe how ideas and symbols propagate through a culture like genes through a population . with the advent of the internet , the process became directly observable in how jokes and images were popularized at lightning speed . and soon , the word came to refer to a certain kind of image . so meme not only describes how words become part of language , the word is a meme itself . and there 's a word for this phenomenon of words that describe themselves : autological . not all new words are created equal . some stick around for millennia , some adapt to changing times , and others die off . some relay information , some interpret it , but the way these words are created and the journey they take to become part of our speech tells us a lot about our world and how we communicate within it .
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and sometimes a new word is n't new at all . obsolete words gain new life by adopting new meanings . villain originally meant a peasant farmer , but in a twist of aristocratic snobbery came to mean someone not bound by the knightly code of chivalry and , therefore , a bad person .
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some words are borrowed from other languages ? why do we do this rather than invent completely new ones ?
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translator : bedirhan cinar why do we cringe when we hear `` shakespeare ? '' if you ask me , it 's usually because of his words . all those thines and thous and therefores and wherefore-art-thous can be more than a little annoying . but you have to wonder , why is he so popular ? why have his plays been made and remade more than any other playwright ? it 's because of his words . back in the late 1500s and early 1600s , that was the best tool that a person had , and there was a lot to talk about . however , most of it was pretty depressing . you know , with the black plague and all . shakespeare does use a lot of words . one of his most impressive accomplishments is his use of insults . they would unify the entire audience ; and no matter where you sat , you could laugh at what was going on onstage . words , specifically dialogue in a drama setting , are used for many different reasons : to set the mood of the scene , to give some more atmosphere to the setting , and to develop relationships between characters . insults do this in a very short and sharp way . let 's first go to `` hamlet . '' right before this dialogue , polonius is the father of ophelia , who is in love with prince hamlet . king claudius is trying to figure out why prince hamlet is acting so crazy since the king married prince hamlet 's mother . polonius offers to use his daughter to get information from prince hamlet . then we go into act ii scene 2 . polonius : `` do you know me , my lord ? '' hamlet : `` excellent well . you 're a fishmonger . '' polonius : `` not i , my lord . '' hamlet : `` then i would you were so honest a man . '' now , even if you did not know what `` fishmonger '' meant , you can use some contextual clues . one : polonius reacted in a negative way , so it must be bad . two : fish smell bad , so it must be bad . and three : `` monger '' just does n't sound like a good word . so from not even knowing the meaning , you 're beginning to construct some characterization of the relationship between hamlet and polonius , which was not good . but if you dig some more , `` fishmonger '' means a broker of some type , and in this setting , would mean like a pimp , like polonius is brokering out his daughter for money , which he is doing for the king 's favor . this allows you to see that hamlet is not as crazy as he 's claiming to be , and intensifies the animosity between these two characters . want another example ? `` romeo and juliet '' has some of the best insults of any of shakespeare 's plays . it 's a play about two gangs , and the star-crossed lovers that take their own lives . well , with any fisticuffs you know that there is some serious smack talk going on . and you are not disappointed . in act i scene 1 , right from the get-go we are shown the level of distrust and hatred the members of the two families , the capulets and montagues , meet . gregory : `` i will frown as i pass by , and let them take it as they list . '' sampson : `` nay , as they dare , i will bite my thumb at them , which is a disgrace to them , if they bear it . '' enter abraham and balthasar . abraham : `` do you bite your thumb at us , sir ? '' sampson : `` i do bite my thumb , sir . '' abraham : `` do you bite your thumb at us , sir ? '' okay , so how does this development help us understand mood or character ? well , let 's break it down to the insult . biting your thumb today may not seem like a big deal , but sampson says it is an insult to them . if they take it so , it must have been one . this begins to show us the level of animosity between even the men who work for the two houses . and you normally would not do anything to someone unless you wanted to provoke them into a fight , which is exactly what 's about to happen . looking deeper , biting your thumb in the time in which the play was written is like giving someone the finger today . a pretty strong feeling comes with that , so we now are beginning to feel the tension in the scene . later on in the scene , tybalt , from the house of the capulets , lays a good one on benvolio from the house of the montagues . tybalt : `` what , art thou drawn among these heartless hinds ? turn thee , benvolio , and look upon thy death . '' benvolio : `` i do but keep the peace ; put up thy sword , or manage it to part these men with me . '' tybalt : `` what , drawn and talk of peace ! i hate the word , as i hate hell , all montagues , and thee . have at thee , coward ! '' okay , heartless hinds . we know that once again , it 's not a good thing . both families hate each other , and this is just adding fuel to the fire . but just how bad is this stinger ? a heartless hind is a coward , and calling someone that in front of his own men , and the rival family , means there 's going to be a fight . tybalt basically calls out benvolio , and in order to keep his honor , benvolio has to fight . this dialogue gives us a good look at the characterization between these two characters . tybalt thinks that the montagues are nothing but cowardly dogs , and has no respect for them . once again , adding dramatic tension to the scene . okay , now here 's a spoiler alert . tybalt 's hotheadedness and severe hatred of the montagues is what we literature people call his hamartia , or what causes his downfall . oh , yes . he goes down at the hands of romeo . so when you 're looking at shakespeare , stop and look at the words , because they really are trying to tell you something .
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polonius : `` do you know me , my lord ? '' hamlet : `` excellent well . you 're a fishmonger . ''
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what does fishmonger mean in the context of shakespeare 's play hamlet ?
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you know , i had a real rough time in school with add , and i have a phd . i earned a phd , but ... tough to pay attention -- biology , geology , physics , chemistry -- really tough for me . only one thing grabbed my attention , and it 's that planet called earth . but in this picture here , you 'll see that earth is mostly water . that 's the pacific . seventy percent of earth is covered with water . you can say , `` hey , i know earth . i live here . '' you do n't know earth . you do n't know this planet , because most of it 's covered with that -- average depth , two miles . and when you go outside and look up at the empire state building , chrysler building , the average depth of the ocean is 15 of those on top of one another . we 've explored about five percent of what 's in that water . `` explored , '' meaning , for the first time , go peek and see what 's there . so what i want to do today is show you some things about this planet , about the oceans . i want to take you from shallow water down to the deep water , and hopefully , like me , you 'll see some things that get you hooked on exploring planet earth . you know things like corals ; you 've seen plenty of corals , those of you who 've been to the beach , snorkeling , know corals are an amazing place to go -- full of life , some big animals , small animals , some nice , some dangerous , sharks , whales , all that stuff . they need to be protected from humanity . they 're great places . but what you probably do n't know is in the very deep part of the ocean , we have volcanic eruptions . most volcanoes on earth are at the bottom of the sea -- more than 80 percent . and we actually have fire , fire deep inside the ocean , going on right now . all over the world -- in the pacific , the atlantic , the indian ocean . in this place , the ocean floor , the rocks actually turn to liquid . so you actually have waves on the ocean floor . you 'd say nothing could live there , but when we look in detail , even there , in the deepest , darkest places on earth , we find life , which tells us that life really wants to happen . so , pretty amazing stuff . every time we go to the bottom of the sea , we explore with our submarines , with our robots , we see something that 's usually surprising , sometimes it 's startling and sometimes revolutionary . you see that puddle of water sitting there . and all around the water there 's a little cliff , there 's a little white sandy beach . we 'll get closer , you 'll see the beach a little bit better , some of the waves in that water , down there . the thing that 's special about this water is that it 's at the bottom of the gulf of mexico . so you 're sitting inside a submarine , looking out the window at a little pond of water beneath the sea . we see ponds , we see lakes , we see rivers -- in fact , right here is a river at the bottom of the ocean going from the lower left to the upper right . water is actually flowing through there . this totally blew our minds . how can you have this at the bottom ? you 're in the ocean looking at more water . and there 's animals that only live in that water . so , the bottom of the ocean -- i love this map , because it shows in the middle of the ocean , there 's a mountain range . it 's the greatest mountain range on earth , called the mid-ocean ridge -- 50,000 miles long , and we 've hardly had a peek at it . hardly had a peek at it . we find valleys , many thousands of valleys , larger , wider , deeper than the grand canyon . we find , as i said , underwater lakes , rivers , waterfalls . the largest waterfall on the planet is actually under the ocean , up near iceland . all that stuff is in that five percent that we 've explored . so the deal about the ocean is that to explore it , you 've got to have technology . not only technology , but it 's not just dave gallo or one person exploring , it 's a team of people . you 've got to have the talent , the team . you 've got to have the technology . in this case , it 's our ship , atlantis , and the submarine , alvin . inside that submarine -- this is an alvin launch -- there 's three people . they 're being wheeled out onto deck . there 's 47 other people , the teamwork on that ship , making sure that these people are okay . everybody in that submarine is thinking one thing right now : should i have gone to the bathroom one more time ? because you 're in there for 10 hours -- 10 hours in that little sphere . three of you together and nobody is going to be around you . you go into the water and once you hit the water , it 's amazing . there 's a lovely color blue that penetrates right inside you . you do n't hear the surface ship anymore , you hear that pinging of a sonar . if you 've got an iphone you 've got sonar on there -- it 's that same pinging that goes down to the bottom and comes back up . divers check out the sub to make sure the outside is okay , and then they say `` go , '' and down you go to the bottom of the ocean and it 's an amazing trip . so for two and a half hours , you sink down to the bottom . and two hours of it is totally pitch black . we thought that nothing could live inside that world at the bottom of the ocean . and when we look , we find some amazing things . all the way down -- we call it the mid-water -- from the top of the ocean down to the bottom , we find life . whenever we stop and look , we find life . i 'm going to show you some jellies . they 're absolutely some of the coolest creatures on earth . look at that thing , just flailing his arms around . that 's like a little lobster . that one is like all these animals with their mouths hooked together , the colonial animals . some animals are tiny , some can be longer than this stage . just amazing animals . and you ca n't collect them with a net -- we have to go with our cameras and take a look at them . so every time we go , new species of life . the ocean is full of life . and yet the deepest part of the ocean -- when we go to that mountain range , we find hot springs . now we were sure -- because this is poisonous water , because it 's so deep it would crush the titanic the same way you crush an empty cup in your hand -- we were sure there would be no life there at all . instead , we find more life and diversity and density than in the tropical rainforest . so , in one instance , in one peek out the window of the sub , we discover something that revolutionizes the way we think about life on earth ; and that is , you do n't always have to have sunlight to get life going . there 's big animals down there too , some that look familiar . that guy 's called dumbo . i love him . dumbo 's great . this guy -- oh man , i wish i had more footage of this . we 're trying to get an expedition together to go look at this and maybe in a year we 'll have that . go online and look . vampyroteuthis infernalis . the vampire squid . incredibly cool . in the darkness of the deep sea , he 's got glowing tentacles , so if i 'm coming at you like him , i put my arms out in the darkness so all you see are little glowing things over here . meanwhile , i 'm coming at you . when he wants to escape , he 's got these glowing pods on his butt that look like eyes . glowing eyes on his butt . how cool is that ? just an amazing animal . ( laughter ) `` vampire '' squid , because when it gets protective , it pulls this black cape over its whole body , and curls up into a ball . outrageous animal . this ship , `` the ship of dreams '' -- a hundred years ago this coming april , this ship was supposed to show up in new york . it 's the titanic . i co-led an expedition out there last year . we are learning so much about that ship . the titanic is an interesting place for biology , because animals are moving in to live on the titanic . microbes are actually eating the hull of the titanic . that 's where jack was king of the world there on the bow of the titanic . so we 're doing real good . and what 's exciting to me is that we 're making a virtual titanic , so you can sit there at home with your joystick and your headset on , and you can actually explore the titanic for yourself . that 's what we want to do , make these virtual worlds , so it 's not dave gallo or someone else exploring the world ; it 's you . you explore it for yourself . so here 's the bottom line : the oceans are unexplored and i ca n't begin to tell you how important that is , because they 're important to us . seven billion people live on this planet and all of us are impacted by the sea , because the oceans control the air you breathe , the water you drink , the food you eat . all those are controlled in some way by the ocean , and this is a thing that we have n't even explored -- five percent . the thing i want to leave you with is , in that five percent , i showed you some cool stuff . there 's a lot more cool stuff -- every dive we go on in the ocean , we find something new about the sea . so what 's in that other 95 percent ? did we get the exciting stuff or is there more out there ? and i 'm here to tell you that the ocean is full of surprises . there 's a quote i love by marcel proust : `` the true voyage of exploration is not so much in seeking new landscapes , '' which we do , `` but in having new eyes . '' and so i hope today , by showing you some of this , it 's given you some new eyes about this planet , and for the first time , i want you to think about it differently . thank you very much . thank you . ( applause )
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vampyroteuthis infernalis . the vampire squid . incredibly cool .
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how did the vampire squid get its name ?
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in islamic culture , geometry is everywhere . you can find it in mosques , madrasas , palaces and private homes . this tradition began in the 8th century ce during the early history of islam , when craftsman took preexisting motifs from roman and persian cultures and developed them into new forms of visual expression . this period of history was a golden age of islamic culture , during which many achievements of previous civilizations were preserved and further developed , resulting in fundamental advancements in scientific study and mathematics . accompanying this was an increasingly sophisticated use of abstraction and complex geometry in islamic art , from intricate floral motifs adorning carpets and textiles , to patterns of tilework that seemed to repeat infinitely , inspiring wonder and contemplation of eternal order . despite the remarkable complexity of these designs , they can be created with just a compass to draw circles and a ruler to make lines within them , and from these simple tools emerges a kaleidoscope multiplicity of patterns . so how does that work ? well , everything starts with a circle . the first major decision is how will you divide it up ? most patterns split the circle into four , five or six equal sections . and each division gives rise to distinctive patterns . there 's an easy way to determine whether any pattern is based on fourfold , fivefold , or sixfold symmetry . most contain stars surrounded by petal shapes . counting the number of rays on a starburst , or the number of petals around it , tells us what category the pattern falls into . a star with six rays , or surrounded by six petals , belongs in the sixfold category . one with eight petals is part of the fourfold category , and so on . there 's another secret ingredient in these designs : an underlying grid . invisible , but essential to every pattern , the grid helps determine the scale of the composition before work begins , keeps the pattern accurate , and facilitates the invention of incredible new patterns . let 's look at an example of how these elements come together . we 'll start with a circle within a square , and divide it into eight equal parts . we can then draw a pair of criss-crossing lines and overlay them with another two . these lines are called construction lines , and by choosing a set of their segments , we 'll form the basis of our repeating pattern . many different designs are possible from the same construction lines just by picking different segments . and the full pattern finally emerges when we create a grid with many repetitions of this one tile in a process called tessellation . by choosing a different set of construction lines , we might have created this pattern , or this one . the possibilities are virtually endless . we can follow the same steps to create sixfold patterns by drawing construction lines over a circle divided into six parts , and then tessellating it , we can make something like this . here 's another sixfold pattern that has appeared across the centuries and all over the islamic world , including marrakesh , agra , konya and the alhambra . fourfold patterns fit in a square grid , and sixfold patterns in a hexagonal grid . fivefold patterns , however , are more challenging to tessellate because pentagons do n't neatly fill a surface , so instead of just creating a pattern in a pentagon , other shapes have to be added to make something that is repeatable , resulting in patterns that may seem confoundingly complex , but are still relatively simple to create . also , tessellation is not constrained to simple geometric shapes , as m.c . escher 's work demonstrates . and while the islamic geometric design tradition does n't tend to employ elements like fish and faces , it does sometimes make use of multiple shapes to craft complex patterns . this more than 1,000-year-old tradition has wielded basic geometry to produce works that are intricate , decorative and pleasing to the eye . and these craftsman prove just how much is possible with some artistic intuition , creativity , dedication and a great compass and ruler .
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we can follow the same steps to create sixfold patterns by drawing construction lines over a circle divided into six parts , and then tessellating it , we can make something like this . here 's another sixfold pattern that has appeared across the centuries and all over the islamic world , including marrakesh , agra , konya and the alhambra . fourfold patterns fit in a square grid , and sixfold patterns in a hexagonal grid . fivefold patterns , however , are more challenging to tessellate because pentagons do n't neatly fill a surface , so instead of just creating a pattern in a pentagon , other shapes have to be added to make something that is repeatable , resulting in patterns that may seem confoundingly complex , but are still relatively simple to create .
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some patterns appear across the islamic world and across the centuries . it is often not clear how the same patterns could be made in different places , centuries apart and thousands of kilometers apart . what possible explanations can you think of that might explain this ?
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when you hear the word art , what comes to mind ? a painting , like the mona lisa , or a famous sculpture or a building ? what about a vase or a quilt or a violin ? are those things art , too , or are they craft ? and what 's the difference anyway ? it turns out that the answer is not so simple . a spoon or a saddle may be finely wrought , while a monument may be , well , uninspired . just as not every musical instrument is utilitarian , not every painting or statue is made for its own sake . but if it 's so tricky to separate art from craft , then why do we distinguish objects in this way ? you could say it 's the result of a dramatic historical turn of events . it might seem obvious to us today to view people , such as da vinci or michelangelo , as legendary artists , and , of course , they possessed extraordinary talents , but they also happened to live in the right place at the right time , because shortly before their lifetimes the concept of artists hardly existed . if you had chanced to step into a medieval european workshop , you would have witnessed a similar scene , no matter whether the place belonged to a stonemason , a goldsmith , a hatmaker , or a fresco painter . the master , following a strict set of guild statutes , insured that apprentices and journeymen worked their way up the ranks over many years of practice and well-defined stages of accomplishment , passing established traditions to the next generation . patrons regarded these makers collectively rather than individually , and their works from murano glass goblets , to flemish lace , were valued as symbols of social status , not only for their beauty , but their adherence to a particular tradition . and the customer who commissioned and paid for the work , whether it was a fine chair , a stone sculpture , a gold necklace , or an entire building , was more likely to get credit than those who designed or constructed it . it was n't until around 1400 that people began to draw a line between art and craft . in florence , italy , a new cultural ideal that would later be called renaissance humanism was beginning to take form . florentine intellectuals began to spread the idea of reformulating classical greek and roman works , while placing greater value on individual creativity than collective production . a few brave painters , who for many centuries , had been paid by the square foot , successfully petitioned their patrons to pay them on the basis of merit instead . within a single generation , people 's attitudes about objects and their makers would shift dramatically , such that in 1550 , giorgio vasari , not incidentally a friend of michelangelo , published an influential book called , `` lives of the most excellent painters , sculptors and architects , '' elevating these types of creators to rock star status by sharing juicy biographical details . in the mind of the public , painting , sculpture and architecture were now considered art , and their makers creative masterminds : artists . meanwhile , those who maintained guild traditions and faithfully produced candelsticks , ceramic vessels , gold jewelery or wrought iron gates , would be known communally as artisans , and their works considered minor or decorative arts , connoting an inferior status and solidifying the distinction between art and craft that still persists in the western world . so , if we consider a painting by rembrandt or picasso art , then where does that leave an african mask ? a chinese porclein vase ? a navajo rug ? it turns out that in the history of art , the value placed on innovation is the exception rather than the rule . in many cultures of the world , the distinction between art and craft has never existed . in fact , some works that might be considered craft , a peruvian rug , a ming dynasty vase , a totem pole , are considered the cultures ' preeminent visual forms . when art historians of the 19th century saw that the art of some non-western cultures did not change for thousands of years , they classified the works as primitive , suggesting that their makers were incapable of innovating and therefore were not really artists . what they did n't realize was that these makers were not seeking to innovate at all . the value of their works lay precisely in preserving visual traditions , rather than in changing them . in the last few decades , works such as quilts , ceramics and wood carvings have become more prominently included in art history textbooks and displayed in museums alongside paintings and sculpture . so maybe it 's time to dispense with vague terms like art and craft in favor of a word like visual arts that encompasses a wider array of aesthetic production . after all , if our appreciation of objects and their makers is so conditioned by our culture and history , then art and its definition are truly in the eye of the beholder .
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a few brave painters , who for many centuries , had been paid by the square foot , successfully petitioned their patrons to pay them on the basis of merit instead . within a single generation , people 's attitudes about objects and their makers would shift dramatically , such that in 1550 , giorgio vasari , not incidentally a friend of michelangelo , published an influential book called , `` lives of the most excellent painters , sculptors and architects , '' elevating these types of creators to rock star status by sharing juicy biographical details . in the mind of the public , painting , sculpture and architecture were now considered art , and their makers creative masterminds : artists .
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who authored a book in 1550 entitled lives of the most excellent painters , sculptors , and architects , which rocketed several renaissance artists to fame ?
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we live in an age of protest . on campuses and public squares , on streets and social media , protesters around the world are challenging the status quo . protest can thrust issues onto the national or global agenda , it can force out tyrants , it can activate people who have long been on the sidelines of civic life . while protest is often necessary , is it sufficient ? consider the arab spring . all across the middle east , citizen protesters were able to topple dictators . afterwards , though , the vacuum was too often filled by the most militant and violent . protest can generate lasting positive change when it 's followed by an equally passionate effort to mobilize voters , to cast ballots , to understand government , and to make it more inclusive . so here are three core strategies for peacefully turning awareness into action and protest into durable political power . first , expand the frame of the possible , second , choose a defining fight , and third , find an early win . let 's start with expanding the frame of the possible . how often have you heard in response to a policy idea , `` that 's just never going to happen '' ? when you hear someone say that , they 're trying to define the boundaries of your civic imagination . the powerful citizen works to push those boundaries outward , to ask what if - what if it were possible ? what if enough forms of power - people power , ideas , money , social norms - were aligned to make it happen ? simply asking that question and not taken as given all the givens of conventional politics is the first step in converting protest to power . but this requires concreteness about what it would look like to have , say , a radically smaller national government , or , by contrast , a big single-payer healthcare system , a way to hold corporations accountable for their misdeeds , or , instead , a way to free them from onerous regulations . this brings us to the second strategy , choosing a defining fight . all politics is about contrasts . few of us think about civic life in the abstract . we think about things in relief compared to something else . powerful citizens set the terms of that contrast . this does n't mean being uncivil . it simply means thinking about a debate you want to have on your terms over an issue that captures the essence of the change you want . this is what the activists pushing for a $ 15 minimum wage in the u.s. have done . they do n't pretend that $ 15 by itself can fix inequality , but with this ambitious and contentious goal , which they achieved first in seattle and then beyond , they have forced a bigger debate about economic justice and prosperity . they 've expanded the frame of the possible , strategy one , and created a sharp emblematic contrast , strategy two . the third key strategy , then , is to seek and achieve an early win . an early win , even if it 's not as ambitious as the ultimate goal , creates momentum , which changes what people think is possible . the solidarity movement , which organized workers in cold war poland emerged just this way , first , with local shipyard strikes in 1980 that forced concessions , then , over the next decade , a nationwide effort that ultimately helped topple poland 's communist government . getting early wins sets in motion a positive feedback loop , a contagion , a belief , a motivation . it requires pressuring policymakers , using the media to change narrative , making arguments in public , persuading skeptical neighbors one by one by one . none of this is as sexy as a protest , but this is the history of the u.s. civil rights movement , of indian independence , of czech self-determination . not the single sudden triumph , but the long , slow slog . you do n't have to be anyone special to be part of this grind , to expand the frame of the possible , to pick a defining fight , or to secure an early win . you just have to be a participant and to live like a citizen . the spirit of protest is powerful . so is showing up after the protest . you can be the co-creator of what comes next .
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protest can generate lasting positive change when it 's followed by an equally passionate effort to mobilize voters , to cast ballots , to understand government , and to make it more inclusive . so here are three core strategies for peacefully turning awareness into action and protest into durable political power . first , expand the frame of the possible , second , choose a defining fight , and third , find an early win .
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which of these is not an example of successfully moving from protest to power ?
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ok , fermium , it has absolutely no use as far as anyone knows except that it ’ s extremely radioactive . it ’ s named after enrico fermi who is a well-known physicist . fermi was an italian physicist who in the 1930s was the first person to discover artificial radioactivity . this is where neutrons , which had only recently been discovered when they did these experiments , hit an element that is not radioactive , increase the weight of the nucleus but not the number of protons and cause it to fall apart by radioactive decay . and it also , like einsteinium , where it was first found in the debris of a nuclear bomb , in fact the very first nuclear bomb that was ever tested . shortly after the fascists took power in italy , fermi moved to the united states and , as part of the manhattan project for building the atomic bomb , he built the first nuclear reactor under the football stadium , in the squash courts under the football stadium at chicago university , the university of chicago , right in the centre of chicago , and they filled the squash courts with blocks of carbon with holes in the middle through which they put rods of uranium . so the first ever sustained nuclear reaction took place in the sports field of university of chicago and if you go now there , the stadium itself has been completely demolished , but there ’ s a rather fine monument to the birth of the atomic era .
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this is where neutrons , which had only recently been discovered when they did these experiments , hit an element that is not radioactive , increase the weight of the nucleus but not the number of protons and cause it to fall apart by radioactive decay . and it also , like einsteinium , where it was first found in the debris of a nuclear bomb , in fact the very first nuclear bomb that was ever tested . shortly after the fascists took power in italy , fermi moved to the united states and , as part of the manhattan project for building the atomic bomb , he built the first nuclear reactor under the football stadium , in the squash courts under the football stadium at chicago university , the university of chicago , right in the centre of chicago , and they filled the squash courts with blocks of carbon with holes in the middle through which they put rods of uranium .
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as with einsteinium , fermium was first observed in the debris of the very first nuclear bomb . what was the bomb´s name ?
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ah , romantic love - beautiful and intoxicating , heartbreaking and soul-crushing , often all at the same time . why do we choose to put ourselves through its emotional wringer ? does love make our lives meaningful , or is it an escape from our loneliness and suffering ? is love a disguise for our sexual desire , or a trick of biology to make us procreate ? is it all we need ? do we need it at all ? if romantic love has a purpose , neither science nor psychology has discovered it yet . but over the course of history , some of our most respected philosophers have put forward some intriguing theories . love makes us whole , again . the ancient greek philosopher plato explored the idea that we love in order to become complete . in his `` symposium '' , he wrote about a dinner party , at which aristophanes , a comic playwright , regales the guests with the following story : humans were once creatures with four arms , four legs , and two faces . one day , they angered the gods , and zeus sliced them all in two . since then , every person has been missing half of him or herself . love is the longing to find a soulmate who 'll make us feel whole again , or , at least , that 's what plato believed a drunken comedian would say at a party . love tricks us into having babies . much , much later , german philosopher arthur schopenhauer maintained that love based in sexual desire was a voluptuous illusion . he suggested that we love because our desires lead us to believe that another person will make us happy , but we are sorely mistaken . nature is tricking us into procreating , and the loving fusion we seek is consummated in our children . when our sexual desires are satisfied , we are thrown back into our tormented existences , and we succeed only in maintaining the species and perpetuating the cycle of human drudgery . sounds like somebody needs a hug . love is escape from our loneliness . according to the nobel prize-winning british philosopher bertrand russell , we love in order to quench our physical and psychological desires . humans are designed to procreate , but without the ecstasy of passionate love , sex is unsatisfying . our fear of the cold , cruel world tempts us to build hard shells to protect and isolate ourselves . love 's delight , intimacy , and warmth helps us overcome our fear of the world , escape our lonely shells , and engage more abundantly in life . love enriches our whole being , making it the best thing in life . love is a misleading affliction . siddhārtha gautama , who became known as the buddha , or the enlightened one , probably would have had some interesting arguments with russell . buddha proposed that we love because we are trying to satisfy our base desires . yet , our passionate cravings are defects , and attachments , even romantic love , are a great source of suffering . luckily , buddha discovered the eight-fold path , a sort of program for extinguishing the fires of desire so that we can reach nirvana , an enlightened state of peace , clarity , wisdom , and compassion . the novelist cao xueqin illustrated this buddhist sentiment that romantic love is folly in one of china 's greatest classical novels , `` dream of the red chamber . '' in a subplot , jia rui falls in love with xi-feng who tricks and humiliates him . conflicting emotions of love and hate tear him apart , so a taoist gives him a magic mirror that can cure him as long as he does n't look at the front of it . but of course , he looks at the front of it . he sees xi-feng . his soul enters the mirror and he is dragged away in iron chains to die . not all buddhists think this way about romantic and erotic love , but the moral of this story is that such attachments spell tragedy , and should , along with magic mirrors , be avoided . love lets us reach beyond ourselves . let 's end on a slightly more positive note . the french philosopher simone de beauvoir proposed that love is the desire to integrate with another and that it infuses our lives with meaning . however , she was less concerned with why we love and more interested in how we can love better . she saw that the problem with traditional romantic love is it can be so captivating , that we are tempted to make it our only reason for being . yet , dependence on another to justify our existence easily leads to boredom and power games . to avoid this trap , beauvoir advised loving authentically , which is more like a great friendship . lovers support each other in discovering themselves , reaching beyond themselves , and enriching their lives and the world together . though we might never know why we fall in love , we can be certain that it will be an emotional rollercoaster ride . it 's scary and exhilarating . it makes us suffer and makes us soar . maybe we lose ourselves . maybe we find ourselves . it might be heartbreaking , or it might just be the best thing in life . will you dare to find out ?
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luckily , buddha discovered the eight-fold path , a sort of program for extinguishing the fires of desire so that we can reach nirvana , an enlightened state of peace , clarity , wisdom , and compassion . the novelist cao xueqin illustrated this buddhist sentiment that romantic love is folly in one of china 's greatest classical novels , `` dream of the red chamber . '' in a subplot , jia rui falls in love with xi-feng who tricks and humiliates him .
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which sentiment about romantic love does novelist cao xueqin illustrate in dream of the red chamber ?
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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 .
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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 .
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what happened to cantor during the last half of his life ?
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10,000 years ago , a deadly virus arose in northeastern africa . the virus spread through the air , attacking the skin cells , bone marrow , spleen , and lymph nodes of its victims . the unlucky infected developed fevers , vomiting , and rashes . 30 % of infected people died during the second week of infection . survivors bore scars and scabs for the rest of their lives . smallpox had arrived . in 1350 b.c. , the first smallpox epidemics hit during the egypt-hittite war . egyptian prisoners spread smallpox to the hittites , which killed their king and devastated his civilization . insidiously , smallpox made its way around the world via egyptian merchants , then through the arab world with the crusades , and all the way to the americas with the spanish and portuguese conquests . since then , it has killed billions of people with an estimated 300 to 500 million people killed in the 20th century alone . but smallpox is not unbeatable . in fact , the fall of smallpox started long before modern medicine . it began all the way back in 1022 a.d . according to a small book , called `` the correct treatment of small pox , '' a buddhist nun living in a famous mountain named o mei shan in the southern providence of sichuan would grind up smallpox scabs and blow the powder into nostrils of healthy people . she did this after noticing that those who managed to survive smallpox never got it again , and her odd treatment worked . the procedure , called variolation , slowly evolved and by the 1700 's , doctors were taking material from sores and putting them into healthy people through four or five scratches on the arm . this worked pretty well as inoculated people would not get reinfected , but it was n't foolproof . up to three percent of people would still die after being exposed to the puss . it was n't until english physician edward jenner noticed something interesting about dairy maids that we got our modern solution . at age 13 , while jenner was apprentice to a country surgeon and apothecary in sodbury , near bristol , he heard a dairy maid say , `` i shall never have smallpox , for i have had cowpox . i shall never have an ugly , pockmarked face . '' cowpox is a skin disease that resembles smallpox and infects cows . later on , as a physician , he realized that she was right , women who got cowpox did n't develop the deadly smallpox . smallpox and cowpox viruses are from the same family . but when a virus infects an unfamiliar host , in this case cowpox infecting a human , it is less virulent , so jenner decided to test whether the cowpox virus could be used to protect against smallpox . in may 1796 , jenner found a young dairy maid , sarah nelmes , who had fresh cowpox lesions on her hand and arm caught from the utters of a cow named blossom . using matter from her pustules , he inoculated james phipps , the eight-year-old son of his gardener . after a few days of fever and discomfort , the boy seemed to recover . two months later , jenner inoculated the boy again , this time with matter from a fresh smallpox lesion . no disease developed , and jenner concluded that protection was complete . his plan had worked . jenner later used the cowpox virus in several other people and challenged them repeatedly with smallpox , proving that they were immune to the disease . with this procedure , jenner invented the smallpox vaccination . unlike variolation , which used actual smallpox virus to try to protect people , vaccination used the far less dangerous cowpox virus . the medical establishment , cautious then as now , deliberated at length over his findings before accepting them . but eventually vaccination was gradually accepted and variolation became prohibited in england in 1840 . after large vaccination campaigns throughout the 19th and 20th centuries , the world health organization certified smallpox 's eradication in 1979 . jenner is forever remembered as the father of immunology , but let 's not forget the dairy maid sarah nelmes , blossom the cow , and james phipps , all heroes in this great adventure of vaccination who helped eradicate smallpox .
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jenner later used the cowpox virus in several other people and challenged them repeatedly with smallpox , proving that they were immune to the disease . with this procedure , jenner invented the smallpox vaccination . unlike variolation , which used actual smallpox virus to try to protect people , vaccination used the far less dangerous cowpox virus . the medical establishment , cautious then as now , deliberated at length over his findings before accepting them .
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how did the smallpox virus infection spread most frequently ?
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some of the world 's most recognizable symbols exist to sell products , others to steer traffic or advance political causes . but there 's one whose main purpose is to help people . you may know it as the wheelchair symbol , or a sign for people with disabilities , but its formal title as maintained by the iso is the international symbol of access . but despite its familiarity , many people are unclear as to what the symbol actually means , which has a lot to do with the symbol itself and the way it came about . in 1968 , the international commission on technology and accessibility held a design contest . they were looking for a symbol that would be readily identifiable from a reasonable distance , self-descriptive , simple , practical , and could n't be confused with existing signage . the winning design , which did n't have a head , was created by a danish designer named susanne koefed . the addition of a head a year later gave it a more human form , and within ten years , it was endorsed by both the united nations and the iso . with minimal cost and minimal fuss , a global icon was born . there have been a few tweaks over the decades . the graphic artists guild added more rounded , human-like features , and in 2012 , the accessible icon project produced a more dynamic version . but what does it really represent ? what 's its purpose ? put simply , it 's a sign to identify where there are accessible facilities . the strength of such an internationally recognized image is that wherever you travel , you do n't need to speak the language or have in-depth cultural knowledge . if you require an accessible toilet , the sign shows the way . but the confusion comes from the term accessibility and what that actually means . many people assume that because the symbol depicts a wheelchair , that accessible facilities are meant only for people who use wheelchairs , or those , at the very least , who have a visible physical condition . but accessibility is a broad concept that applies to many , many different conditions . that includes people with autism , visual impairments , and autoimmune diseases , like lupus , which can cause pain and fatigue , along with many other conditions . in fact , the world health organization estimates that there are approximately 1 billion people who experience some form of disability , which means that this group is very likely to include yourself , or a family member , a classmate , a friend , or a work colleague . and people who use wheelchairs only make up about 65 million , or 15 % of the total . the vast majority have non-visible disabilities . accessible parking spaces , facilities , and entrances are designed with that entire group in mind . so it 's easy to see why in recent years people have begun to raise questions about whether the symbol is really appropriate for what it 's meant to do . and it 's not just about accuracy . it 's common for people to become indignant , sometimes abusive , when they see people without visible disabilities using accessible facilities . the symbol is unfortunately creating widespread issues for the very people and families it 's meant to help . the recent redesigns have attempted with some success to acknowledge concerns over the current symbol . but some think that a complete redesign is in order . it 's a difficult task , though . how do you replace a symbol that 's familiar the world over ? and what do you replace it with ?
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and it 's not just about accuracy . it 's common for people to become indignant , sometimes abusive , when they see people without visible disabilities using accessible facilities . the symbol is unfortunately creating widespread issues for the very people and families it 's meant to help .
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what laws and organizations exist in your country to support/protect the rights of people with disabilities ?
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english , like all languages , is a messy business . you can be uncouth but not couth . you can be ruthless , but good luck trying to show somebody that you have ruth unless you happen to be married to someone named ruth . it 's bad to be unkempt but impossible to be kempt , or sheveled as opposed to disheveled . there are other things that make no more sense than those but that seem normal now because the sands of time have buried where they came from . for example , did you ever wonder why a nickname for edward is ned ? where 'd the n come from ? it 's the same with nellie for ellen . afterall , if someone 's name is ethan , we do n't nickname him nethan , nor do we call our favorite maria , nmaria . in fact , if anyone did , our primary urge would be to either scold them or gently hide them away until the company had departed . all these nicknames trace back to a mistake , although , a perfectly understandable one . in fact , even the word nickname is weird . what 's so `` nick '' about a nickname ? is it that it 's a name that has a nick in it ? let 's face it , not likely . actually , in old english , the word was ekename , and eke meant also or other . you can see eke still used in chaucer 's < em > canterbury tales < /em > in a sentence like , `` whan zephyrus eek with his sweete breeth , '' which meant , `` when zephyr also with his sweet breath . '' ekename meant `` also name . '' what happened was that when people said , `` an ekename , '' it could sound like they were saying , `` a nekename , '' and after a while , so many people were hearing it that way that they started saying , `` that 's my nickname , '' instead of , `` that 's my ekename . '' now , the word had a stray n at the front that started as a mistake , but from now on was what the word really was . it was rather as if you had gum on the bottom of your shoe and stepped on a leaf , dragged that leaf along for the rest of your life , were buried wearing that shoe and went to heaven in it to spend eternity wedded to that stray , worn-out leaf . ekename picked up an n and never let it go . the same thing happened with other words . old english speakers cut otches into wood . but after centuries of being asked to cut an otch into something , it was easy to think you were cutting a notch instead , and pretty soon you were . in a world where almost no one could read , it was easier for what people heard to become , after awhile , what it started to actually be . here 's where the ned-style nicknames come in . old english was more like german than our english is now , and just as in german , my is mein , in old english , my was meen . you would say meen book , actually boke in old english , or meen cat . and just as today , we might refer to our child as my dahlia or my laura , in old english , they would say , `` meen ed '' . that is mein ed , mein ellie . you see where this is going . as time passed , meen morphed into the my we know today . that meant that when people said , `` mein ed , '' it sounded like they were saying my ned . that is , it sounded like whenever someone referred to edward affectionately , they said ned instead of ed . behold , the birth of a nickname ! or an ekename . hence , also nellie for ellen and nan for ann , and even in the old days , nabby for abigal . president john adam 's wife abigail 's nickname was nabby . all sorts of words are like this . old english speakers wore naprons , but a napron sounds like an apron , and that gave birth to a word apron that no one in beowulf would have recognized . umpire started as numpires , too . if all of this sounds like something sloppy that we modern people would never do , then think about something you hear all the time and probably say , `` a whole nother . '' what 's nother ? we have the word another , of course , but it 's composed of an and other , or so we thought . yet , when we slide whole into the middle , we do n't say , `` a whole other , '' we clip that n off of the an and stick it to other and create a new word , nother . for a long time , nobody was writing these sort of things down or putting them in a dictionary , but that 's only because writing is more codified now than it was 1,000 years ago . so , when you see a weird word , remember that there might be a whole nother side to the story .
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for example , did you ever wonder why a nickname for edward is ned ? where 'd the n come from ? it 's the same with nellie for ellen .
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many words no longer have the n they once had because :
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translator : andrea mcdonough reviewer : jessica ruby mysteries of vernacular : sarcophagus , a stone coffin typically adorned with decorative carvings or inscriptions . the history of the word sarcophagus is so skin-crawlingly grotesque , it seems to come right out of a low-budget horror film . rather than having a b-movie origin , however , its roots can be traced back to the early roman empire where the greek word sarkophagus was used to describe the limestone that a coffin was made of , not the coffin itself . according to the roman scholar pliny the elder , citizens of the empire believed that limestone from a quarry near troy would dissolve flesh . for this reason , it was quite desireable in the construction of coffins . though it 's unclear if the belief was widespread or even accurately reported by pliny , what is certain is that sarkophagus came from the greek words sark , meaning flesh , and phagein , a verb meaning to eat . from flesh-eating stone to stone coffin , it 's a fitting etymology for the final resting place of the deceased .
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though it 's unclear if the belief was widespread or even accurately reported by pliny , what is certain is that sarkophagus came from the greek words sark , meaning flesh , and phagein , a verb meaning to eat . from flesh-eating stone to stone coffin , it 's a fitting etymology for the final resting place of the deceased .
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the ancient egyptians had very strong ideas about the way one ’ s body traveled into the afterlife . how do you think they would have felt about flesh-eating coffins ?
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a famous ancient greek once said , `` give me a place to stand , and i shall move the earth . '' but this was n't some wizard claiming to perform impossible feats . it was the mathematician archimedes describing the fundamental principle behind the lever . the idea of a person moving such a huge mass on their own might sound like magic , but chances are you 've seen it in your everyday life . one of the best examples is something you might recognize from a childhood playground : a teeter-totter , or seesaw . let 's say you and a friend decide to hop on . if you both weigh about the same , you can totter back and forth pretty easily . but what happens if your friend weighs more ? suddenly , you 're stuck up in the air . fortunately , you probably know what to do . just move back on the seesaw , and down you go . this may seem simple and intuitive , but what you 're actually doing is using a lever to lift a weight that would otherwise be too heavy . this lever is one type of what we call simple machines , basic devices that reduce the amount of energy required for a task by cleverly applying the basic laws of physics . let 's take a look at how it works . every lever consists of three main components : the effort arm , the resistance arm , and the fulcrum . in this case , your weight is the effort force , while your friend 's weight provides the resistance force . what archimedes learned was that there is an important relationship between the magnitudes of these forces and their distances from the fulcrum . the lever is balanced when the product of the effort force and the length of the effort arm equals the product of the resistance force and the length of the resistance arm . this relies on one of the basic laws of physics , which states that work measured in joules is equal to force applied over a distance . a lever ca n't reduce the amount of work needed to lift something , but it does give you a trade-off . increase the distance and you can apply less force . rather than trying to lift an object directly , the lever makes the job easier by dispersing its weight across the entire length of the effort and resistance arms . so if your friend weighs twice as much as you , you 'd need to sit twice as far from the center as him in order to lift him . by the same token , his little sister , whose weight is only a quarter of yours , could lift you by sitting four times as far as you . seesaws may be fun , but the implications and possible uses of levers get much more impressive than that . with a big enough lever , you can lift some pretty heavy things . a person weighing 150 pounds , or 68 kilograms , could use a lever just 3.7 meters long to balance a smart car , or a ten meter lever to lift a 2.5 ton stone block , like the ones used to build the pyramids . if you wanted to lift the eiffel tower , your lever would have to be a bit longer , about 40.6 kilometers . and what about archimedes ' famous boast ? sure , it 's hypothetically possible . the earth weighs 6 x 10^24 kilograms , and the moon that 's about 384,400 kilometers away would make a great fulcrum . so all you 'd need to lift the earth is a lever with a length of about a quadrillion light years , 1.5 billion times the distance to the andromeda galaxy . and of course a place to stand so you can use it . so for such a simple machine , the lever is capable of some pretty amazing things . and the basic elements of levers and other simple machines are found all around us in the various instruments and tools that we , and even some other animals , use to increase our chances of survival , or just make our lives easier . after all , it 's the mathematical principles behind these devices that make the world go round .
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seesaws may be fun , but the implications and possible uses of levers get much more impressive than that . with a big enough lever , you can lift some pretty heavy things . a person weighing 150 pounds , or 68 kilograms , could use a lever just 3.7 meters long to balance a smart car , or a ten meter lever to lift a 2.5 ton stone block , like the ones used to build the pyramids .
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which of these is not an example of a lever ?
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on september 1st , 1953 , william scoville used a hand crank and a cheap drill saw to bore into a young man 's skull , cutting away vital pieces of his brain and sucking them out through a metal tube . but this was n't a scene from a horror film or a gruesome police report . dr. scoville was one of the most renowned neurosurgeons of his time , and the young man was henry molaison , the famous patient known as `` h.m. '' , whose case provided amazing insights into how our brains work . as a boy , henry had cracked his skull in an accident and soon began having seizures , blacking out and losing control of bodily functions . after enduring years of frequent episodes , and even dropping out of high school , the desperate young man had turned to dr. scoville , a daredevil known for risky surgeries . partial lobotomies had been used for decades to treat mental patients based on the notion that mental functions were strictly localized to corresponding brain areas . having successfully used them to reduce seizures in psychotics , scoville decided to remove h.m. 's hippocampus , a part of the limbic system that was associated with emotion but whose function was unknown . at first glance , the operation had succeeded . h.m. 's seizures virtually disappeared , with no change in personality , and his iq even improved . but there was one problem : his memory was shot . besides losing most of his memories from the previous decade , h.m. was unable to form new ones , forgetting what day it was , repeating comments , and even eating multiple meals in a row . when scoville informed another expert , wilder penfield , of the results , he sent a ph.d student named brenda milner to study h.m. at his parents ' home , where he now spent his days doing odd chores , and watching classic movies for the first time , over and over . what she discovered through a series of tests and interviews did n't just contribute greatly to the study of memory . it redefined what memory even meant . one of milner 's findings shed light on the obvious fact that although h.m. could n't form new memories , he still retained information long enough from moment to moment to finish a sentence or find the bathroom . when milner gave him a random number , he managed to remember it for fifteen minutes by repeating it to himself constantly . but only five minutes later , he forgot the test had even taken place . neuroscientists had though of memory as monolithic , all of it essentially the same and stored throughout the brain . milner 's results were not only the first clue for the now familiar distinction between short-term and long-term memory , but show that each uses different brain regions . we now know that memory formation involves several steps . after immediate sensory data is temporarily transcribed by neurons in the cortex , it travels to the hippocampus , where special proteins work to strengthen the cortical synaptic connections . if the experience was strong enough , or we recall it periodically in the first few days , the hippocampus then transfers the memory back to the cortex for permanent storage . h.m. 's mind could form the initial impressions , but without a hippocampus to perform this memory consolidation , they eroded , like messages scrawled in sand . but this was not the only memory distinction milner found . in a now famous experiment , she asked h.m. to trace a third star in the narrow space between the outlines of two concentric ones while he could only see his paper and pencil through a mirror . like anyone else performing such an awkward task for the first time , he did horribly . but surprisingly , he improved over repeated trials , even though he had no memory of previous attempts . his unconscious motor centers remembered what the conscious mind had forgotten . what milner had discovered was that the declarative memory of names , dates and facts is different from the procedural memory of riding a bicycle or signing your name . and we now know that procedural memory relies more on the basal ganglia and cerebellum , structures that were intact in h.m. 's brain . this distinction between `` knowing that '' and `` knowing how '' has underpinned all memory research since . h.m. died at the age of 82 after a mostly peaceful life in a nursing home . over the years , he had been examined by more than 100 neuroscientists , making his the most studied mind in history . upon his death , his brain was preserved and scanned before being cut into over 2000 individual slices and photographed to form a digital map down to the level of individual neurons , all in a live broadcast watched by 400,000 people . though h.m. spent most of his life forgetting things , he and his contributions to our understanding of memory will be remembered for generations to come .
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but this was n't a scene from a horror film or a gruesome police report . dr. scoville was one of the most renowned neurosurgeons of his time , and the young man was henry molaison , the famous patient known as `` h.m. '' , whose case provided amazing insights into how our brains work . as a boy , henry had cracked his skull in an accident and soon began having seizures , blacking out and losing control of bodily functions . after enduring years of frequent episodes , and even dropping out of high school , the desperate young man had turned to dr. scoville , a daredevil known for risky surgeries .
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after henry molaison ( h.m. ) cracked his skull when he was young , which symptoms did he suffer ?
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imagine waking up the morning of prom , or your wedding day , or a big job interview… and sure enough , you look in the mirror to find your forehead is covered in zits ! it ’ s happened to lots of us . acne , or acne vulgaris , is the most common skin disease in humans . it affects about 80 % of people at some point in their lives . most people get acne between the ages of 11 and 30 , but sometimes older people continue to struggle with it , too . acne happens when follicles and pores become clogged with dead skin cells and oils . and … it sucks . but by studying how acne forms , doctors have developed ways to prevent and treat it . it all starts with your skin : a complex organ made up of two layers and lots of nerves , blood vessels , and glands . your skin cells regenerate about once a month , so you constantly have dead skin cells sloughing off , and new skin cells rising to the surface . this whole skin-replacement thing isn ’ t much of a problem , on its own . but lots of these dead skin cells come out through your pores . and pores make things more complicated . skin pores are essentially just openings for tiny hairs . hair follicles , the root ends of the hairs , are embedded in your skin and surrounded by clusters of sebaceous glands , special glands that produce sebum . sebum is that oily , waxy stuff that comes out of your pores . it helps keep your skin waterproof and moisturized : it keeps excess water out of your body , and it keeps water already inside you from getting out through your skin . so , sebum is important . but things can go very wrong if your sebum production gets out of whack . when your body doesn ’ t produce enough sebum , your skin can dry out , making you more susceptible to bacterial or fungal infections . but if your body produces too much sebum , it can build up inside your pores , trap dead skin cells , and cause a blockage . increased sebum production is one of the major factors involved in the development of acne . increased keratin production is another one . keratin is a protein produced by your hair follicles . it gives structure to each strand of hair , as well as the top layer of your skin . but when the hair follicles produce too much keratin , the extra protein binds together dead skin cells , so they can ’ t just shed out of the pore like they normally would . you end up with a blockage that then traps more dead skin cells , plus sebum . once the pore is officially clogged , it becomes a breeding ground for colonies of bacteria — especially propionibacterium acnes . that ’ s a species of commensal bacteria , which basically means it ’ s friendly . it naturally lives on your skin , and it ’ s not harmful … most of the time . the commensal bacteria that make up your microbiome probably even help prevent other , more harmful bacteria from colonizing on your skin . so having colonies of propionibacterium acnes living on you isn ’ t a bad thing . you want them there — as long as they stay on the surface of your skin . when the bacteria find their way deep into skin pores where they don ’ t belong , that ’ s when they can cause an infection . and infections often cause inflammation . when you get an infection , your immune system responds by increasing blood flow to the area and sending extra immune cells and enzymes to fight off the infection . different combinations of symptoms cause different kinds of acne , with names you ’ ve probably heard before : blackheads , whiteheads , pimples , pustules … technically , they all mean different things . the scientific term for a clogged pore is a comedo , which actually used to mean a parasitic worm . people started using the term to refer to a clogged pore because the stuff that comes out when you squeeze it looks kind of like a worm . when the main symptom is just that the pore is clogged , without much inflammation , that ’ s either a blackhead or a whitehead . blackheads are what it ’ s called when the comedo is open . the trapped sebum and dead skin cells become oxidized , which turns the surface of the clogged material into a dark color , kind of like how silver tarnishes . when the comedo closes , skin cells grow over the top of the plug and stop this oxidation from happening , so the whitish color of the sebum shows through . that ’ s called a whitehead . when there ’ s a comedo plus an infection that causes inflammation , that ’ s a different kind of acne : pimples ! the typical reddish bumpy kind are more specifically called papules . if the inflammation gets really bad , sometimes the bumps start leaking fluid or bacteria-filled pus . those kind are categorized as pustules , and they ’ re usually a much brighter red , or sometimes white from the oozing fluid . the most severe kind of acne is generally called cystic acne . that ’ s when the infection takes root in the deepest layers of the skin . sometimes the infection causes more solid bumps to form , called nodules . and sometimes the infection causes pus-filled bumps , called cysts . so that ’ s how acne happens . but what causes it in the first place ? what makes healthy pores become clogged , infected , and sometimes ooze-y ? again , there are a few different factors involved . genetics seem to be important , for one thing . so if your parents had acne , you ’ re more likely to have it too . hormones also have a huge influence on acne — specifically , androgen hormones , like testosterone , which influence the development of both the male and female reproductive systems . which explains why acne is so much more of a problem during puberty . androgen hormones are linked to sebum production . so during puberty , when the hormones are highly active , there ’ s an increase in sebum production . increased stress has been thought to increase hormone production , as well . so if you find yourself breaking out the day before a big test , that ’ s probably why . when you ’ re stressed , you produce more hormones , which then increases your sebum production . since sebum is an oil , a lot of people say that greasy foods will cause acne . sometimes you ’ ll also hear that dairy makes it worse , or even more specific foods , like chocolate . but the truth is , scientists aren ’ t really sure how or whether diet and acne are connected . there have been lots of studies investigating this , and some do suggest a possible link . but others don ’ t . we need more comprehensive , controlled trials with plenty of subjects before we can come to any real conclusions . doctors do acknowledge that there ’ s anecdotal evidence , and they say that if changing your diet has helped with your acne , then it makes sense for you to stick with it . there just isn ’ t enough evidence to support the idea that diet has a role in acne in general . but we do know that exposure to other topical oils , like some cosmetics or moisturizers , can cause acne by blocking your pores with extra oils and trapping sebum . it ’ s easy to avoid the problem , though — just look for products that say they ’ re non-comedogenic , which means that they shouldn ’ t clog your pores . but the natural oil on your face isn ’ t really a problem . you ’ ll often hear that you should wash your face a lot to help prevent acne , but acne isn ’ t caused by dirt or by the natural oil that ’ s already on the surface of your skin . and washing your face too much can actually irritate your skin , making acne worse . to treat acne , the goal is to reduce the factors that come together to cause breakouts . the one thing you shouldn ’ t do is pop a zit . the big risk is that you ’ ll push the infection out of the hair follicle and into the surrounding skin , instead of out to the surface . plus , you ’ ll irritate the area , causing more inflammation and making the acne take longer to heal . you might also spread bacteria to non-affected pores . instead , treatments try to lower sebum production , stop dead cells from clumping together in the pore as much , prevent bacterial growth , and lower inflammation . treatments can range from mild to aggressive , depending on how severe the symptoms are . for mild acne like blackheads and whiteheads , you can usually use topical over-the-counter medications . one of the most effective is benzoyl peroxide , a chemical compound that ’ s really good at killing bacteria . it decomposes into super reactive forms of oxygen , which bind to and destroy the molecules the bacteria need to survive . another common treatment is salicylic acid , which doesn ’ t kill the bacteria , but stops them from replicating . it can also break down skin cells and keratin to help unclog the pores inflammatory acne , like papular pimples or cystic acne , sometimes needs stronger treatment to reduce the inflammation . that usually means prescription meds . # # # antibiotics — the kind that are also used to treat other bacterial infections , from strep throat to urinary tract infections — can be used to treat acne . they stop bacterial growth and reduce inflammation . another kind of treatment involves retinoids , which are compounds related to vitamin a. retinoids work by binding to skin cell receptors to remove dead skin cells and encourage healthy skin cell growth . so retinoids work really well to unclog pores full of dead skin cells . they ’ re anti-inflammatory , too . in severe cystic acne cases , stronger retinoids actually work at the deeper layers of skin to reduce the size of the oil glands so they produce less sebum . and since hormones are a big factor in sebum production , using birth control or corticosteroids can regulate female hormones and reduce the amount of androgen hormones being produced . fewer androgen receptors at work means less sebum production , which means less acne . sometimes , severe , cystic acne will leave scarring , but there are ways to reduce it . these procedures don ’ t necessarily treat or prevent the acne itself , but they can reduce the bumps and scars left over from bad breakouts . dermabrasion uses a gentle sanding tool to wear down layers of the skin that have scarred over from cystic acne , but it only works for people with lighter skin . this procedure has mostly been replaced by laser resurfacing , which uses laser pulses to remove skin layer by layer until the scar has smoothed out . then there are chemical peels , which use compounds like salicylic acid or retinoic acid to perform what ’ s basically a controlled injury to the top layer of skin , killing the top layer of cells . the dead skin cells peel off , revealing healthy skin cells underneath . luckily , most people grow out of the acne-ridden years of puberty , though some people will continue to have acne well into their 40s and 50s . but even though a bad breakout might make you self-conscious , it ’ s normal , it ’ s treatable , and it ’ s not life-threatening . so take care of your skin , talk to your doctor about prescription treatments if you want them , and trust that your acne will probably get better with age . and then you get to look forward to wrinkles ! thanks for watching this episode of scishow , brought to you by our patrons on patreon . if you want to help support this show , just go to patreon.com/scishow . and don ’ t forget to go to youtube.com/scishow and subscribe !
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but when the hair follicles produce too much keratin , the extra protein binds together dead skin cells , so they can ’ t just shed out of the pore like they normally would . you end up with a blockage that then traps more dead skin cells , plus sebum . once the pore is officially clogged , it becomes a breeding ground for colonies of bacteria — especially propionibacterium acnes .
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what two functions does sebum -- the oil on your skin -- serve ?
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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 .
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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 .
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were tycho brahe ’ s unusual personal experiences an asset or a distraction to his astronomy career ?
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before the creation of humanity , the greek gods won a great battle against a race of giants called the titans . most titans were destroyed or driven to the eternal hell of tartarus . but the titan prometheus , whose name means foresight , persuaded his brother epimetheus to fight with him on the side of the gods . as thanks , zeus entrusted the brothers with the task of creating all living things . epimetheus was to distribute the gifts of the gods among the creatures . to some , he gave flight ; to others , the ability to move through water or race through grass . he gave the beasts glittering scales , soft fur , and sharp claws . meanwhile , prometheus shaped the first humans out of mud . he formed them in the image of the gods , but zeus decreed they were too remain mortal and worship the inhabitants of mount olympus from below . zeus deemed humans subservient creatures vulnerable to the elements and dependent on the gods for protection . however , prometheus envisioned his crude creations with a greater purpose . so when zeus asked him to decide how sacrifices would be made , the wily prometheus planned a trick that would give humans some advantage . he killed a bull and divided it into two parts to present to zeus . on one side , he concealed the succulent flesh and skin under the unappealing belly of the animal . on the other , he hid the bones under a thick layer of fat . when zeus chose the seemingly best portion for himself , he was outraged at prometheus 's deception . fuming , zeus forbade the use of fire on earth , whether to cook meat or for any other purpose . but prometheus refused to see his creations denied this resource . and so , he scaled mount olympus to steal fire from the workshop of hephaestus and athena . he hid the flames in a hollow fennel stalk and brought it safely down to the people . this gave them the power to harness nature for their own benefit and ultimately dominate the natural order . with fire , humans could care for themselves with food and warmth . but they could also forge weapons and wage war . prometheus 's flames acted as a catalyst for the rapid progression of civilization . when zeus looked down at this scene , he realized what had happened . prometheus had once again wounded his pride and subverted his authority . furious , zeus imposed a brutal punishment . prometheus was to be chained to a cliff for eternity . each day , he would be visited by a vulture who would tear out his liver and each night his liver would grow back to be attacked again in the morning . although prometheus remained in perpetual agony , he never expressed regret at his act of rebellion . his resilience in the face of oppression made him a beloved figure in mythology . he was also celebrated for his mischievous and inquisitive spirit , and for the knowledge , progress , and power he brought to human hands . he 's also a recurring figure in art and literature . in percy bysshe shelley 's lyrical drama `` prometheus unbound , '' the author imagines prometheus as a romantic hero who escapes and continues to spread empathy and knowledge . of his protagonist , shelley wrote , `` prometheus is the type of the highest perfection of moral and intellectual nature , impelled by the purest and the truest motives to the best and noblest ends . '' his wife mary envisaged prometheus as a more cautionary figure and subtitled her novel `` frankenstein : the modern prometheus . '' this suggests the damage of corrupting the natural order and remains relevant to the ethical questions surrounding science and technology today . as hero , rebel , or trickster , prometheus remains a symbol of our capacity to capture the powers of nature , and ultimately , he reminds us of the potential of individual acts to ignite the world .
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most titans were destroyed or driven to the eternal hell of tartarus . but the titan prometheus , whose name means foresight , persuaded his brother epimetheus to fight with him on the side of the gods . as thanks , zeus entrusted the brothers with the task of creating all living things .
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in greek , the name prometheus means :
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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 .
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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 .
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the definition of density is
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one foggy morning in 1884 , the british steamer `` rumney '' crashed into the french ship `` frigorifique . '' seeing their ship filling with water , the french crew climbed aboard the `` rumney . '' but as they sailed towards the nearest port , a silent form suddenly emerged from the fog : the abandoned `` frigorifique . '' it was too late to turn , and the impact was enough to sink the `` rumney . '' as the sailors scrambled into the lifeboats , the empty `` frigorifique '' sailed back into the fog , having seemingly taken its revenge . in reality , the french sailors had left the engines running , and the `` frigorifique '' sailed in a circle before striking the `` rumney '' and finally sinking . but its story became one of the many tales of ghost ships , unmanned vessels that apparently sail themselves . and although they 've influenced works like `` dracula '' and `` pirates of the caribbean , '' crewless ships are n't the product of ghostly spirits , just physics at work . one of the most famous ghost ships was the `` mary celeste '' found sailing the atlantic in 1872 with no one aboard , water in its hold , and lifeboats missing . the discovery of its intact cargo and a captain 's log that ended abruptly led to wild rumors and speculation . but the real culprits were two scientific phenomena : buoyancy and fluid dynamics . here 's how buoyancy works . an object placed in a liquid displaces a certain volume of fluid . the liquid in turn exerts an upward buoyant force equal to the weight of the fluid that 's been displaced . this phenomenon is called archimedes 's principle . objects that are less dense than water , such as balsa wood , icebergs , and inflatable rafts always float . that 's because the upward buoyant force is always stronger than the downward force of gravity . but for objects or ships to float when they 're made of materials , like steel , that are denser than water , they must displace a volume of water larger than their weight . normally , the water filling a ship 's hull would increase its weight and cause it to sink - just what the `` mary celeste 's '' crew feared when they abandoned ship . but the sailors did n't account for fluid dynamics . the water stopped flowing at the point of equilibrium , when it reached the same level as the hull . as it turned out , the weight of the water was n't enough to sink the ship and the `` mary celeste '' was found a few days later while the unfortunate crew never made it to shore . far stranger is the tale of `` a. ernest mills , '' a schooner transporting salt , whose crew watched it sink to the sea floor following a collision . yet four days later , it was spotted floating on the surface . the key to the mystery lay in the ship 's heavy cargo of salt . the added weight of the water in the hull made the vessel sink , but as the salt dissolved in the water , the weight decreased enough that the force of gravity became less than the buoyant force and the ship floated back to the surface . but how do we explain the most enduring aspect of ghost ship legends : multiple sightings of the same ships hundreds of miles and several years apart ? the answer lies in ocean currents , which are like invisible rivers flowing through the ocean . factors , like temperature , salinity , wind , gravity , and the coriolis effect from the earth 's rotation create a complex system of water movement . that applies both at the ocean 's surface and deep below . sailors have always known about currents , but their patterns were n't well known until recently . in fact , tracking abandoned ships was how scientists determined the shape and speed of the atlantic gyre , the gulf stream , and related currents in the first place . beginning in 1883 , the u.s. hydrographic office began collecting monthly data that included navigation hazards , like derelict ships , whose locations were reported by passing vessels . so abandoned ships may not be moved by ghost crews or supernatural curses , but they are a real and fascinating phenomenon born through the ocean and kept afloat by powerful , invisible , scientifically studied forces .
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objects that are less dense than water , such as balsa wood , icebergs , and inflatable rafts always float . that 's because the upward buoyant force is always stronger than the downward force of gravity . but for objects or ships to float when they 're made of materials , like steel , that are denser than water , they must displace a volume of water larger than their weight .
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buoyancy is an upward force equal to :
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james joyce 's `` ulysses '' is widely considered to be both a literary masterpiece and one of the hardest works of literature to read . it inspires such devotion that once a year on a day called bloomsday , thousands of people all over the world dress up like the characters , take to the streets , and read the book aloud . and some even make a pilgrimage to dublin just to visit the places so vividly depicted in joyce 's opus . so what is it about this famously difficult novel that inspires so many people ? there 's no one simple answer to that question , but there are a few remarkable things about the book that keep people coming back . the plot , which transpires over the course of a single day , is a story of three characters : stephen dedalus , reprised from joyce 's earlier novel , `` a portrait of the artist as a young man '' ; leopold bloom , a half-jewish advertising canvasser for a dublin newspaper ; and bloom 's wife molly , who is about to embark on an affair . stephen is depressed because of his mother 's recent death . meanwhile , bloom wanders throughout the city . he goes to a funeral , his work , a pub , and so on , avoiding going home because molly is about to begin her affair . where it really starts to get interesting , though , is how the story 's told . each chapter is written in a different style . 15 is a play , 13 is like a cheesy romance novel , 12 is a story with bizarre , exaggerated interruptions , 11 uses techniques , like onomatopoeia , repetitions , and alliteration to imitate music , and 14 reproduces the evolution of english literary prose style , from its beginnings in anglo-saxon right up to the 20th century . that all culminates in the final chapter which follows molly 's stream of consciousness as it spools out in just eight long paragraphs with almost no punctuation . the range of styles joyce uses in `` ulysses '' is one of the things that makes it so difficult , but it also helps make it enjoyable . and it 's one of the reasons that the book has held up as one of the key texts of literary modernism , a movement characterized by overturning traditional modes of writing . joyce fills his narrative gymnastic routines with some of the most imaginative use of language you 'll find anywhere . take , for instance , `` the figure seated on a large boulder at the foot of a round tower was that of a broadshouldered deepchested stronglimbed frankeyed redhaired freelyfreckled shaggybearded widemouthed largenosed longheaded deepvoiced barekneed brawnyhanded hairlegged ruddyfaced sinewyarmed hero . '' here , joyce exaggerates the description of a mangy old man in a pub to make him seem like an improbably gigantesque hero . it 's true that some sections are impenetrably dense at first glance , but it 's up to the reader to let their eyes skim over them or break out a shovel and dig in . and once you start excavating the text , you 'll find the book to be an encyclopedic treasure trove . it 's filled with all manner of references and allusions from medieval philosophy to the symbolism of tattoos , and from dante to dublin slang . as suggested by the title , some of these allusions revolve around homer 's `` odyssey . '' each chapter is named after a character or episode from the `` odyssey , '' but the literary references are often coy , debatable , sarcastic , or disguised . for example , homer 's odysseus , after an epic 20-year-long journey , returns home to ithaca and reunites with his faithful wife . in contrast , joyce 's bloom wanders around dublin for a day and returns home to his unfaithful wife . it 's a very funny book . it has highbrow intellectual humor , if you have the patience to track down joyce 's references , and more lowbrow dirty jokes . those , and other sexual references , were too much for some . in the u.s. , the book was put on trial , banned , and censored before it had even been completed because it was originally published as a serial novel . readers of `` ulysses '' are n't just led through a variety of literary styles . they 're also given a rich and shockingly accurate tour of a specific place at a time : dublin in 1904 . joyce claimed that if dublin were to be destroyed , it could be recreated from the pages of this book . while such a claim is not exactly true , it does show the great care that joyce took in precisely representing details , both large and small , of his home city . no small feat considering he wrote the entire novel while living outside of his native ireland . it 's a testament to joyce 's genius that `` ulysses '' is a difficult book . some people find it impenetrable without a full book of annotations to help them understand what joyce is even talking about . but there 's a lot of joy to be found in reading it , more than just unpacking allusions and solving puzzles . and if it 's difficult , or frustrating , or funny , that 's because life is all that , and more . responding to some criticism of `` ulysses , '' and there was a lot when it was first published , joyce said that if `` ulysses '' is n't worth reading , then life is n't worth living .
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it 's a very funny book . it has highbrow intellectual humor , if you have the patience to track down joyce 's references , and more lowbrow dirty jokes . those , and other sexual references , were too much for some . in the u.s. , the book was put on trial , banned , and censored before it had even been completed because it was originally published as a serial novel .
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references to which famous italian writer can be found in ulysses ?
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if you line up the entire text of `` moby dick , '' which was published in 1851 , into a giant rectangle , you may notice some peculiar patterns , like these words , which seem to predict the assassination of martin luther king , or these references to the 1997 death of princess di . so , was herman melville a secret prophet ? the answer is no , and we know that thanks to a mathematical principle called ramsey theory . it 's the reason we can find geometric shapes in the night sky , it 's why we can know without checking that at least two people in london have exactly the same number of hairs on their head , and it explains why patterns can be found in just about any text , even vanilla ice lyrics . so what is ramsey theory ? simply put , it states that given enough elements in a set or structure , some particular interesting pattern among them is guaranteed to emerge . as a simple example , let 's look at what 's called the party problem , a classic illustration of ramsey theory . suppose there are at least six people at a party . amazingly enough , we can say for sure that some group of three of them either all know each other , or have never met before , without knowing a single thing about them . we can demonstrate that by graphing out all the possibilities . each point represents a person , and a line indicates that the pair know each other . every pair only has two possibilities : they either know each other or they do n't . there are a lot of possibilities , but every single one has the property that we 're looking for . six is the lowest number of guests where that 's guaranteed to be the case , which we can express like this . ramsey theory gives us a guarantee that such a minimum number exists for certain patterns , but no easy way to find it . in this case , as the total number of guests grows higher , the combinations get out of control . for instance , say you 're trying to find out the minimum size of a party where there 's a group of five people who all know each other or all do n't . despite five being a small number , the answer is virtually impossible to discover through an exhaustive search like this . that 's because of the sheer volume of possibilities . a party with 48 guests has 2^ ( 1128 ) possible configurations , more than the number of atoms in the universe . even with the help of computers , the best we know is that the answer to this question is somewhere between 43 and 49 guests . what this shows us is that specific patterns with seemingly astronomical odds can emerge from a relatively small set . and with a very large set , the possibilities are almost endless . any four stars where no three lie in a straight line will form some quadrilateral shape . expand that to the thousands of stars we can see in the sky , and it 's no surprise that we can find all sorts of familiar shapes , and even creatures if we look for them . so what are the chances of a text concealing a prophecy ? well , when you factor in the number of letters , the variety of possible related words , and all their abbreviations and alternate spellings , they 're pretty high . you can try it yourself . just pick a favorite text , arrange the letters in a grid , and see what you can find . the mathematician t.s . motzkin once remarked that , `` while disorder is more probable in general , complete disorder is impossible . '' the sheer size of the universe guarantees that some of its random elements will fall into specific arrangements , and because we evolved to notice patterns and pick out signals among the noise , we are often tempted to find intentional meaning where there may not be any . so while we may be awed by hidden messages in everything from books , to pieces of toast , to the night sky , their real origin is usually our own minds .
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it 's the reason we can find geometric shapes in the night sky , it 's why we can know without checking that at least two people in london have exactly the same number of hairs on their head , and it explains why patterns can be found in just about any text , even vanilla ice lyrics . so what is ramsey theory ? simply put , it states that given enough elements in a set or structure , some particular interesting pattern among them is guaranteed to emerge .
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why are computers not capable of finding ramsey numbers through ‘ brute force ’ calculations ?
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fish are in trouble . the cod population off canada 's east coast collapsed in the 1990s , intense recreational and commercial fishing has decimated goliath grouper populations in south florida , and most populations of tuna have plummeted by over 50 % , with the southern atlantic bluefin on the verge of extinction . those are just a couple of many examples . overfishing is happening all over the world . how did this happen ? when some people think of fishing , they imagine relaxing in a boat and patiently reeling in the day 's catch . but modern industrial fishing , the kind that stocks our grocery shelves , looks more like warfare . in fact , the technologies they employ were developed for war . radar , sonar , helicopters , and spotter planes are all used to guide factory ships towards dwindling schools of fish . long lines with hundreds of hooks or huge nets round up massive amounts of fish , along with other species , like seabirds , turtles , and dolphins . and fish are hauled up onto giant boats , complete with onboard flash freezing and processing facilities . all of these technologies have enabled us to catch fish at greater depths and farther out at sea than ever before . and as the distance and depth of fishing have expanded , so has the variety of species we target . for example , the patagonian toothfish neither sounds nor looks very appetizing . and fishermen ignored it until the late 1970s . then it was rebranded and marketed to chefs in the u.s. as chilean sea bass , despite the animal actually being a type of cod . soon it was popping up in markets all over the world and is now a delicacy . unfortunately , these deep water fish do n't reproduce until they 're at least ten years old , making them extremely vulnerable to overfishing when the young are caught before they 've had the chance to spawn . consumer taste and prices can also have harmful effects . for example , shark fin soup is considered such a delicacy in china and vietnam that the fin has become the most profitable part of the shark . this leads many fishermen to fill their boats with fins leaving millions of dead sharks behind . the problems are n't unique to toothfish and sharks . almost 31 % of the world 's fish populations are overfished , and another 58 % are fished at the maximum sustainable level . wild fish simply ca n't reproduce as fast as 7 billion people can eat them . fishing also has impacts on broader ecosystems . wild shrimp are typically caught by dragging nets the size of a football field along the ocean bottom , disrupting or destroying seafloor habitats . the catch is often as little as 5 % shrimp . the rest is by-catch , unwanted animals that are thrown back dead . and coastal shrimp farming is n't much better . mangroves are bulldozed to make room for shrimp farms , robbing coastal communities of storm protection and natural water filtration and depriving fish of key nursery habitats . so what does it look like to give fish a break and let them recover ? protection can take many forms . in national waters , governments can set limits about how , when , where , and how much fishing occurs , with restrictions on certain boats and equipment . harmful practices , such as bottom trawling , can be banned altogether , and we can establish marine reserves closed to all fishing to help ecosystems restore themselves . there 's also a role for consumer awareness and boycotts to reduce wasteful practices , like shark finning , and push fishing industries towards more sustainable practices . past interventions have successfully helped depleted fish populations recover . there are many solutions . the best approach for each fishery must be considered based on science , respect for the local communities that rely on the ocean , and for fish as wild animals . and then the rules must be enforced . international collaboration is often needed , too , because fish do n't care about our borders . we need to end overfishing . ecosystems , food security , jobs , economies , and coastal cultures all depend on it .
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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 .
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what is the original name of the chilean seabass ?
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there 's a factory inside you that weighs about 1.4 kilograms and runs for 24 hours a day . this is your liver , the heaviest organ in your body , and one of the most crucial . this industrious structure simultaneously acts as a storehouse , a manufacturing hub , and a processing plant . and each of these functions involve so many important subtasks that without the liver , our bodies would simply stop working . one of the liver 's main functions is to filter the body 's blood , which it receives in regular shipments from two sources : the hepatic artery delivers blood from the heart , while the hepatic portal vein brings it from the intestine . this double delivery fills the liver with nutrients , that it then sorts , processes and stores with the help of thousands of tiny internal processing plants , known as lobules . both blood flows also deliver the oxygen that the liver needs to function . the blood that is received from the intestine contains carbohydrates , fats , and vitamins and other nutrients dissolved in it from the food you 've consumed . these must be processed in different ways . in the case of carbohydrates , the liver breaks them down and converts them into sugars for the body to use as energy when the filtered blood is sent back out . sometimes the body has leftovers of nutrients that it does n't immediately require . when that happens , the liver holds some back , and stacks them in its storage facility . this facility works like a pantry for future cases when the body might be in need of nutrients . but the blood flowing into the liver is n't always full of good things . it also contains toxins and byproducts that the body ca n't use . and the liver monitors these strictly . when it spots a useless or toxic substance , it either converts it into a product that ca n't hurt the body or isolates it and whisks it away , channeling it through the kidneys and intestine to be excreted . of course , we would n't consider the liver a factory if it did n't also manufacture things . this organ makes everything from various blood plasma proteins that transport fatty acids and help form blood clots , to the cholesterol that helps the body create hormones . it also makes vitamin d and substances that help digestion . but one of its most vital products is bile . like an eco-friendly treatment plant , the liver uses cells called hepatocytes to convert toxic waste products into this bitter greenish liquid . as it 's produced , bile is funneled into a small container below the liver , called the gallbladder , before being trickled into the intestine to help break down fats , destroy microbes , and neutralize extra stomach acid . bile also helps carry other toxins and byproducts from the liver out of the body . so as you can see , the liver is an extremely efficient industrial site , performing multiple tasks that support each other . but such a complex system needs to be kept running smoothly by keeping it healthy and not overloading it with more toxins than it can handle . this is one factory we simply ca n't afford to shut down .
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there 's a factory inside you that weighs about 1.4 kilograms and runs for 24 hours a day . this is your liver , the heaviest organ in your body , and one of the most crucial .
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why do you think the liver has to work 24 hours a day ? why ca n't it just take a break ?
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lead is a very soft metal and it ’ s easily moulded into all sorts of shapes . this is a pot , i ’ m not sure what it is from , i got it from an old lab that was being closed down so it was probably made for holding a strong acid because lead is very unreactive . you can see rather nicely here the white colour of lead oxide because it has oxidised over the years and this is the white material that was used for paints . this white lead paint that people use , the oxide of lead , had one rather unfortunate consequence that it reacts with sulphur in the air and in victorian times when people burnt coal they produced a lot of sulphur , and the sulphur reacted with the lead to give a black colour which made the white paint eventually turn grey and if you waited long enough black . and this effect was exploited by one of my former colleagues here professor leslie crombie , who during the war was working for the british admiralty in their research labs on the camouflaging of submarines . now if you want your submarine not to be seen , when it is well away from the coast it needs to be white because if you have a white submarine it does not show up against the sky but , if you are trying to slip into the coast at night and not be seen you need the submarine to be black . so leslie came up with the idea of painting the submarine with lead oxide and when it was going near the coast , some sailors went out on to the outside of the ship and sloshed over a solution of sulphide and seawater and the paint turned black . and so you could then go into the coast , drop your agent , do whatever secret things you wanted to do , and then when you went away from the coast they sloshed hydrogen peroxide with seawater , which turned the sulphite into sulphate , and lead sulphate is white so your submarine went white again . so you could change the colour of your submarine to suit what you were doing in the military operation and nobody would see you . and that was a real thing that happened ? yes , that was a real thing . i don ’ t know how widely it was used but they actually tried it out and it worked . so they just needed to take the chemicals and they could add the seawater to make the solution to put on the submarine . the other very important property of lead is that because the lead atom is heavy it is very good at stopping radioactive particles particularly alpha particles , which are helium nuclei those are the nucleus of the helium atom , or beta particles which are electrons . what you should find that if we put this in the way , it should stop counting almost immediately so let us see if that works . there we go straight back down to background and if we take it away , and it picks back up again . and so people who are working with radioactive samples used to use , and still use , bricks made out of lead . so here are two of the bricks and you can see this is a small one and this one is rather thinner . the problem is that if you start building these bricks into a wall , there is always a chance that when you have two bits together there might be a slight gap between the two bricks and some of the radioactive particles may go between them . so to avoid this the bricks are made with groves in it , and a pointed part here , so that when you put them together there is absolutely no way that anything can go through because you can ’ t have a direct line through it . now the trouble is of course you can ’ t see anything through it , so if you have an experiment where you want to handle radioactive material inside a container and manipulate it you can ’ t make the whole container of lead because you can ’ t see what is going on inside . and so for that , people have developed lead glass , of which this is a sample and it is immensely heavy , but this is glass and there is really a large amount of lead that has been put in it . and some of the fancy crystals that your grandmothers or your ancestors might have had , had a bit of lead in the glass . this has got a really high proportion of lead in the glass which is probably why the glass is yellow rather than the white colour that you normally have with glass . but windows like this can be used for handling really quite radioactive materials behind them . the colour is rather nice isn ’ t it ? good . but it is very heavy , so… well , lead has had a very long history ; it was one of the first metals to be widely used . the romans used this for drinking materials . there is also lead acetate , that is a compound of lead and vinegar is meant to taste sweet and the romans added this to their wine to make it sweeter . the fact that it was really very poisonous and caused , possibly even caused madness , was not really widely recognised . in fact some people have suggested that part of the collapse of the roman empire was due to too much lead . lead was very widely used in the uk for water pipes because it ’ s easy to manufacture and to join together . it tends not to have been very dangerous in terms of drinking water because it gets a coating on the surface so you do not get much lead in the water ; though if you do have a house with lead pipes in , it is usually advisable to change them . it ’ s again , it was used very widely from the 1920s up till the late 70s or 80s as an additive for petrol . in the old days when petrol engines were first introduced , when you came to a hill and put down the accelerator of your car , the engine started misfiring , so-called ‘ pinking ’ , and the whole thing shook . so it was really quite difficult to drive up hills , but then it was discovered that you could put in a compound , so-called tetraethyl lead , which was really very poisonous , but the guy who discovered it washed his hands in public at a press conference saying “ look it ’ s so safe ” , despite the fact that there were people dying in his factory . so it was very widely adopted and so it was only in quite recent times that it was realised how much lead was being blown out into the atmosphere in car exhausts . and so it ’ s now almost everywhere we have lead-free petrol as a result of people realising the poison-ness of lead .
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this is a pot , i ’ m not sure what it is from , i got it from an old lab that was being closed down so it was probably made for holding a strong acid because lead is very unreactive . you can see rather nicely here the white colour of lead oxide because it has oxidised over the years and this is the white material that was used for paints . this white lead paint that people use , the oxide of lead , had one rather unfortunate consequence that it reacts with sulphur in the air and in victorian times when people burnt coal they produced a lot of sulphur , and the sulphur reacted with the lead to give a black colour which made the white paint eventually turn grey and if you waited long enough black . and this effect was exploited by one of my former colleagues here professor leslie crombie , who during the war was working for the british admiralty in their research labs on the camouflaging of submarines .
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what is the white compound on the inside of the cover of the lead pot , shown by the professor ?
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what do silk , dna , wood , balloons , and silly putty all have in common ? they 're polymers . polymers are such a big part of our lives that it 's virtually impossible to imagine a world without them , but what the heck are they ? polymers are large molecules made of small units called monomers linked together like the railroad cars from a train . poly means many , and mono means one , and mers or mero means parts . many polymers are made by repeating the same small monomer over and over again while others are made from two monomers linked in a pattern . all living things are made of polymers . some of the organic molecules in organisms are small and simple , having only one of a few functional groups . others , especially those that play structural roles or store genetic information , are macromolecules . in many cases , these macromolecules are polymers . for example , complex carbohydrates are polymers of simple sugars , proteins are polymers of amino acids , and nucleic acids , dna and rna , which contain our genetic information , are polymers of nucleotides . trees and plants are made of the polymer cellulose . it 's the tough stuff you find in bark and stems . feathers , fur , hair , and fingernails are made up of the protein keratin , also a polymer . it does n't stop there . did you know that the exoskeletons of the largest phylum in the animal kingdom , the arthropods , are made of the polymer chitin ? polymers also form the basis for synthetic fibers , rubbers , and plastics . all synthetic polymers are derived from petroleum oil and manufactured through chemical reactions . the two most common types of reactions used to make polymers are addition reactions and condensation reactions . in addition reactions , monomers simply add together to form the polymer . the process starts with a free radical , a species with an unpaired electron . the free radical attacks and breaks the bonds to form new bonds . this process repeats over and over to create a long-chained polymer . in condensation reactions , a small molecule , such as water , is produced with each chain-extending reaction . the first synthetic polymers were created by accident as by-products of various chemical reactions . thinking they were useless , chemists mostly discarded them . finally , one named leo baekeland decided maybe his useless by-product was n't so useless after all . his work resulted in a plastic that could be permanently squished into a shape using pressure and high temperatures . since the name of this plastic , polyoxybenzylmethylenglycolanhydride , was n't very catchy , advertisers called it bakelite . bakelite was made into telephones , children 's toys , and insulators for electrical devices . with its development in 1907 , the plastics industry exploded . one other familiar polymer , silly putty , was also invented by accident . during world war ii , the united states was in desperate need of synthetic rubber to support the military . a team of chemists at general electric attempted to create one but ended up with a gooey , soft putty . it was n't a good rubber substitute , but it did have one strange quality : it appeared to be extremely bouncy . silly putty was born ! synthetic polymers have changed the world . think about it . could you imagine getting through a single day without using plastic ? but polymers are n't all good . styrofoam , for example , is made mainly of styrene , which has been identified as a possible carcinogen by the environmental protection agency . as styrofoam products are being made , or as they slowly deteriorate in landfills or the ocean , they can release toxic styrene into the environment . in addition , plastics that are created by addition polymerization reactions , like styrofoam , plastic bags , and pvc , are built to be durable and food-safe , but that means that they do n't break down in the environment . millions of tons of plastics are dumped into landfills every year . this plastic does n't biodegrade , it just breaks down into smaller and smaller pieces , affecting marine life and eventually making their way back to humans . polymers can be soft or hard , squishy or solid , fragile or strong . the huge variation between means they can form an incredibly diverse array of substances , from dna to nylon stockings . polymers are so useful that we 've grown to depend on them every day . but some are littering our oceans , cities , and waterways with effects on our health that we 're only beginning to understand .
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silly putty was born ! synthetic polymers have changed the world . think about it .
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leo baekeland invented ___________________ which was one of the earliest synthetic polymers .
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the discovery of the structure of dna was one of the most important scientific achievements in the last century , in human history , in fact . the now-famous double helix is almost synonymous with watson and crick , two of the scientists who won the nobel prize for figuring it out . but there 's another name you may know , too , rosalind franklin . you may have heard that her data supported watson and crick 's brilliant idea , or that she was a plain-dressing , belligerent scientist , which is how watson actually described her in `` the double helix . '' but thanks to franklin 's biographers , who investigated her life and interviewed many people close to her , we now know that that account is far from true , and her scientific contributions have been vastly underplayed . let 's hear the real story . rosalind elsie franklin was born in london in 1920 . she wanted to be a scientist ever since she was a teenager , which was n't a common or easy career path for girls at that time . but she excelled at science anyway . she won a scholarship to cambridge to study chemistry , where she earned her ph.d. , and she later conducted research on the structure of coal that led to better gas masks for the british during world war ii . in 1951 , she joined king 's college to use x-ray techniques to study the structure of dna , then one of the hottest topics in science . franklin upgraded the x-ray lab and got to work shining high-energy x-rays on tiny , wet crystals of dna . but the acadmemic culture at the time was n't very friendly to women , and franklin was isolated from her colleagues . she clashed with maurice wilkins , a labmate who assumed franklin had been hired as his assistant . but franklin kept working , and in 1952 , she obtained photo 51 , the most famous x-ray image of dna . just getting the image took 100 hours , the calculations necessary to analyze it would take a year . meanwhile , the american biologist james watson and the british physicist francis crick were also working on finding dna 's structure . without franklin 's knowledge , wilkins took photo 51 and showed it to watson and crick . instead of calculating the exact position of every atom , they did a quick analysis of franklin 's data and used that to build a few potential structures . eventually , they arrived at the right one . dna is made of two helicoidal strands , one opposite the other with bases in the center like rungs of a ladder . watson and crick published their model in april 1953 . meanwhile , franklin had finished her calculations , come to the same conclusion , and submitted her own manuscript . the journal published the manuscripts together , but put franklin 's last , making it look like her experiments just confirmed watson and crick 's breakthrough instead of inspiring it . but franklin had already stopped working on dna and died of cancer in 1958 , never knowing that watson and crick had seen her photographs . watson , crick , and wilkins won the nobel prize in 1962 for their work on dna . it 's often said that franklin would have been recognized by a nobel prize if only they could be awarded posthumously . and , in fact , it 's possible she could have won twice . her work on the structure of viruses led to a nobel for a colleague in 1982 . it 's time to tell the story of a brave woman who fought sexism in science , and whose work revolutionized medicine , biology , and agriculture . it 's time to honor rosalind elsie franklin , the unsung mother of the double helix .
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meanwhile , the american biologist james watson and the british physicist francis crick were also working on finding dna 's structure . without franklin 's knowledge , wilkins took photo 51 and showed it to watson and crick . instead of calculating the exact position of every atom , they did a quick analysis of franklin 's data and used that to build a few potential structures .
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if you were wilkins , what would you have done when you got your hands on the photo 51 ?
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there 's a play so powerful that an old superstition says its name should never even be uttered in a theater , a play that begins with witchcraft and ends with a bloody severed head , a play filled with riddles , prophesies , nightmare visions , and lots of brutal murder , a play by william shakespeare sometimes referred to as the `` scottish play '' or the `` tragedy of macbeth . '' first performed at the globe theater in london in 1606 , `` macbeth '' is shakespeare 's shortest tragedy . it is also one of his most action-packed . in five acts , he recounts a story of a scottish nobleman who steals the throne , presides over a reign of terror , and then meets a bloody end . along the way , it asks important questions about ambition , power , and violence that spoke directly to the politics of shakespeare 's time and continue to echo in our own . england in the early 17th century was politically precarious . queen elizabeth i died in 1603 without producing an heir , and in a surprise move , her advisors passed the crown to james stewart , king of scotland . two years later , james was subject to an assassination attempt called the gunpowder plot . questions of what made for a legitimate king were on everyone 's lips . so shakespeare must have known he had potent material when he conflated and adapted the stories of a murderous 11th century scottish king named macbeth and those of several other scottish nobles . he found their annals in hollinshed 's `` chronicles , '' a popular 16th century history of britain and ireland . shakespeare would also have known he needed to tell his story in a way that would immediately grab the attention of his diverse and rowdy audience . the globe welcomed all sections of society . wealthier patrons watched the stage from covered balconies while poorer people paid a penny to take in the show from an open-air section called the pit . talking , jeering , and cheering was common during performances . there are even accounts of audiences throwing furniture when plays were flops . so `` macbeth '' opens with a literal bang . thunder cracks and three witches appear . they announce they 're searching for a scottish nobleman and war hero named macbeth , then fly off while chanting a curse that predicts a world gone mad . `` fair is foul and foul is fair . hover through the fog and filthy air . '' as seen later , they find macbeth and his fellow nobleman banquo . `` all hail macbeth , '' they prophesize , `` that shalt be king hereafter ! '' `` king ? '' macbeth wonders . just what would he have to do to gain the crown ? macbeth and his wife lady macbeth soon chart a course of murder , lies , and betrayal . in the ensuing bloodbath , shakespeare provides viewers with some of the most memorable passages in english literature . `` out , damned spot ! out , i say ! '' lady macbeth cries when she believes she ca n't wipe her victim 's blood off her hands . her obsession with guilt is one of many themes that runs through the play , along with the universal tendency to abuse power , the endless cycles of violence and betrayal , the defying political conflict . as is typical with shakespeare 's language , a number of phrases that got their start in the play have been repeated so many times that they now feel commonplace . they include `` the milk of human kindness , '' `` what 's done is done , '' and the famous witches ' spell , `` double , double toil and trouble ; fire burn , and caldron bubble . '' but shakespeare saves the juiciest bit of all for macbeth himself . towards the end of the play , macbeth reflects on the universality of death and the futility of life . `` out , out , brief candle ! '' he laments . `` life 's but a walking shadow , a poor player that struts and frets his hour upon the stage and then is heard no more . it is a tale told by an idiot , full of sound and fury signifying nothing . '' life may be a tale told my an idiot , but `` macbeth '' is not . shakespeare 's language and characters have entered our cultural consciousness to a rare extent . directors often use the story to shed light on abuses of power , ranging from the american mafia to dictators across the globe . the play has been adapted to film many times , including akira kurosawa 's `` throne of blood , '' which takes place in feudal japan , and a modernized version called `` scotland , pa , '' in which macbeth and his rivals are managers of competing fast food restaurants . no matter the presentation , questions of morality , politics , and power are still relevant today , and so , it seems , is shakespeare 's `` macbeth . ''
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there 's a play so powerful that an old superstition says its name should never even be uttered in a theater , a play that begins with witchcraft and ends with a bloody severed head , a play filled with riddles , prophesies , nightmare visions , and lots of brutal murder , a play by william shakespeare sometimes referred to as the `` scottish play '' or the `` tragedy of macbeth . '' first performed at the globe theater in london in 1606 , `` macbeth '' is shakespeare 's shortest tragedy . it is also one of his most action-packed .
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the audience at the globe theatre , where shakespeare ’ s plays were performed :
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a toothpaste brand claims their product will destroy more plaque than any product ever made . a politician tells you their plan will create the most jobs . we 're so used to hearing these kinds of exaggerations in advertising and politics that we might not even bat an eye . but what about when the claim is accompanied by a graph ? afterall , a graph is n't an opinion . it represents cold , hard numbers , and who can argue with those ? yet , as it turns out , there are plenty of ways graphs can mislead and outright manipulate . here are some things to look out for . in this 1992 ad , chevy claimed to make the most reliable trucks in america using this graph . not only does it show that 98 % of all chevy trucks sold in the last ten years are still on the road , but it looks like they 're twice as dependable as toyota trucks . that is , until you take a closer look at the numbers on the left and see that the figure for toyota is about 96.5 % . the scale only goes between 95 and 100 % . if it went from 0 to 100 , it would look like this . this is one of the most common ways graphs misrepresent data , by distorting the scale . zooming in on a small portion of the y-axis exaggerates a barely detectable difference between the things being compared . and it 's especially misleading with bar graphs since we assume the difference in the size of the bars is proportional to the values . but the scale can also be distorted along the x-axis , usually in line graphs showing something changing over time . this chart showing the rise in american unemployment from 2008 to 2010 manipulates the x-axis in two ways . first of all , the scale is inconsistent , compressing the 15-month span after march 2009 to look shorter than the preceding six months . using more consistent data points gives a different picture with job losses tapering off by the end of 2009 . and if you wonder why they were increasing in the first place , the timeline starts immediately after the u.s. 's biggest financial collapse since the great depression . these techniques are known as cherry picking . a time range can be carefully chosen to exclude the impact of a major event right outside it . and picking specific data points can hide important changes in between . even when there 's nothing wrong with the graph itself , leaving out relevant data can give a misleading impression . this chart of how many people watch the super bowl each year makes it look like the event 's popularity is exploding . but it 's not accounting for population growth . the ratings have actually held steady because while the number of football fans has increased , their share of overall viewership has not . finally , a graph ca n't tell you much if you do n't know the full significance of what 's being presented . both of the following graphs use the same ocean temperature data from the national centers for environmental information . so why do they seem to give opposite impressions ? the first graph plots the average annual ocean temperature from 1880 to 2016 , making the change look insignificant . but in fact , a rise of even half a degree celsius can cause massive ecological disruption . this is why the second graph , which show the average temperature variation each year , is far more significant . when they 're used well , graphs can help us intuitively grasp complex data . but as visual software has enabled more usage of graphs throughout all media , it 's also made them easier to use in a careless or dishonest way . so the next time you see a graph , do n't be swayed by the lines and curves . look at the labels , the numbers , the scale , and the context , and ask what story the picture is trying to tell .
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this is why the second graph , which show the average temperature variation each year , is far more significant . when they 're used well , graphs can help us intuitively grasp complex data . but as visual software has enabled more usage of graphs throughout all media , it 's also made them easier to use in a careless or dishonest way .
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why are graphs commonly used to present claims ?
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ah , romantic love - beautiful and intoxicating , heartbreaking and soul-crushing , often all at the same time . why do we choose to put ourselves through its emotional wringer ? does love make our lives meaningful , or is it an escape from our loneliness and suffering ? is love a disguise for our sexual desire , or a trick of biology to make us procreate ? is it all we need ? do we need it at all ? if romantic love has a purpose , neither science nor psychology has discovered it yet . but over the course of history , some of our most respected philosophers have put forward some intriguing theories . love makes us whole , again . the ancient greek philosopher plato explored the idea that we love in order to become complete . in his `` symposium '' , he wrote about a dinner party , at which aristophanes , a comic playwright , regales the guests with the following story : humans were once creatures with four arms , four legs , and two faces . one day , they angered the gods , and zeus sliced them all in two . since then , every person has been missing half of him or herself . love is the longing to find a soulmate who 'll make us feel whole again , or , at least , that 's what plato believed a drunken comedian would say at a party . love tricks us into having babies . much , much later , german philosopher arthur schopenhauer maintained that love based in sexual desire was a voluptuous illusion . he suggested that we love because our desires lead us to believe that another person will make us happy , but we are sorely mistaken . nature is tricking us into procreating , and the loving fusion we seek is consummated in our children . when our sexual desires are satisfied , we are thrown back into our tormented existences , and we succeed only in maintaining the species and perpetuating the cycle of human drudgery . sounds like somebody needs a hug . love is escape from our loneliness . according to the nobel prize-winning british philosopher bertrand russell , we love in order to quench our physical and psychological desires . humans are designed to procreate , but without the ecstasy of passionate love , sex is unsatisfying . our fear of the cold , cruel world tempts us to build hard shells to protect and isolate ourselves . love 's delight , intimacy , and warmth helps us overcome our fear of the world , escape our lonely shells , and engage more abundantly in life . love enriches our whole being , making it the best thing in life . love is a misleading affliction . siddhārtha gautama , who became known as the buddha , or the enlightened one , probably would have had some interesting arguments with russell . buddha proposed that we love because we are trying to satisfy our base desires . yet , our passionate cravings are defects , and attachments , even romantic love , are a great source of suffering . luckily , buddha discovered the eight-fold path , a sort of program for extinguishing the fires of desire so that we can reach nirvana , an enlightened state of peace , clarity , wisdom , and compassion . the novelist cao xueqin illustrated this buddhist sentiment that romantic love is folly in one of china 's greatest classical novels , `` dream of the red chamber . '' in a subplot , jia rui falls in love with xi-feng who tricks and humiliates him . conflicting emotions of love and hate tear him apart , so a taoist gives him a magic mirror that can cure him as long as he does n't look at the front of it . but of course , he looks at the front of it . he sees xi-feng . his soul enters the mirror and he is dragged away in iron chains to die . not all buddhists think this way about romantic and erotic love , but the moral of this story is that such attachments spell tragedy , and should , along with magic mirrors , be avoided . love lets us reach beyond ourselves . let 's end on a slightly more positive note . the french philosopher simone de beauvoir proposed that love is the desire to integrate with another and that it infuses our lives with meaning . however , she was less concerned with why we love and more interested in how we can love better . she saw that the problem with traditional romantic love is it can be so captivating , that we are tempted to make it our only reason for being . yet , dependence on another to justify our existence easily leads to boredom and power games . to avoid this trap , beauvoir advised loving authentically , which is more like a great friendship . lovers support each other in discovering themselves , reaching beyond themselves , and enriching their lives and the world together . though we might never know why we fall in love , we can be certain that it will be an emotional rollercoaster ride . it 's scary and exhilarating . it makes us suffer and makes us soar . maybe we lose ourselves . maybe we find ourselves . it might be heartbreaking , or it might just be the best thing in life . will you dare to find out ?
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but over the course of history , some of our most respected philosophers have put forward some intriguing theories . love makes us whole , again . the ancient greek philosopher plato explored the idea that we love in order to become complete .
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according to schopenhauer , love is a trick that nature plays in order to get us to do what ?
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would you like to know what 's in our future ? what 's going to happen tomorrow , next year , or even a millennium from now ? well , you 're not alone . everyone from governments to militaries to industry leaders do , as well , and they all employ people called futurists who attempt to forecast the future . some are able to do this with surprising accuracy . in the middle of the 20th century , a think tank known as the rand corporation consulted dozens of scientists and futurists who together forecast many of the technologies we take for granted today , including artificial organs , the use of birth control pills , and libraries able to look up research material for the reader . one way futurists arrive at their predictions is by analyzing movements and trends in society , and charting the paths they are likely to follow into the future with varying degrees of probability . their work informs the decisions of policymakers and world leaders , enabling them to weigh options for the future that otherwise could not have been imagined in such depth or detail . of course , there are obvious limits to how certain anyone can be about the future . there are always unimaginable discoveries that arise which would make no sense to anyone in the present . imagine , for example , transporting a physicist from the middle of the 19th century into the 21st . you explain to him that a strange material exists , uranium 235 , that of its own accord can produce enough energy to power an entire city , or destroy it one fell swoop . `` how can such energy come from nowhere ? '' he would demand to know . `` that 's not science , that 's magic . '' and for all intents and purposes , he would be right . his 19th century grasp of science includes no knowledge of radioactivity or nuclear physics . in his day , no forecast of the future could have predicted x-rays , or the atom bomb , let alone the theory of relativity or quantum mechanics . as arthur c. clarke has said , `` any sufficiently advanced technology is indistinguishable from magic . '' how can we prepare , then , for a future that will be as magical to us as our present would appear to someone from the 19th century ? we may think our modern technology and advanced data analysis techniques might allow us to predict the future with much more accuracy than our 19th century counterpart , and rightly so . however , it 's also true that our technological progress has brought with it new increasingly complex and unpredictable challenges . the stakes for future generations to be able to imagine the unimaginable are higher than ever before . so the question remains : how do we do that ? one promising answer has actually been with us since the 19th century and the industrial revolution that laid the foundation for our modern world . during this time of explosive development and invention , a new form of literature , science fiction , also emerged . inspired by the innovations of the day , jules verne , h.g . wells , and other prolific thinkers explored fantastic scenarios , depicting new frontiers of human endeavor . and throughout the 20th century and into the 21st , storytellers have continued to share their visions of the future and correctly predicted many aspects of the world we inhabit decades later . in `` brave new world , '' aldous huxley foretold the use of antidepressants in 1932 , long before such medication became popular . in 1953 , ray bradbury 's `` fahrenheit 451 , '' forecast earbuds , `` thimble radios , '' in his words . and in `` 2001 : a space odyssey , '' arthur c. clarke described a portable , flat-screen news pad in 1968 . in works that often combine entertainment and social commentary , we are invited to suspend our disbelief and consider the consequences of radical shifts in familiar and deeply engrained institutions . in this sense , the best science fiction fulfills the words of philosopher michel foucault , `` i 'm no prophet . my job is making windows where there were once walls . '' free from the constraints of the present and our assumptions of what 's impossible , science fiction serves as a useful tool for thinking outside of the box . many futurists recognize this , and some are beginning to employ science fictions writers in their teams . just recently , a project called iknow proposed scenarios that look much like science fiction stories . they include the discovery of an alien civilization , development of a way for humans and animals to communicate flawlessly , and radical life extension . so , what does the future hold ? of course , we ca n't know for certain , but science fiction shows us many possibilities . ultimately , it is our responsibility to determine which we will work towards making a reality .
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they include the discovery of an alien civilization , development of a way for humans and animals to communicate flawlessly , and radical life extension . so , what does the future hold ? of course , we ca n't know for certain , but science fiction shows us many possibilities .
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let ’ s say that you want to understand the consequences of global warming . how will you approach the subject , assuming you want to understand the consequences one year from now , or fifty years into the future ?
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what is the shape of a molecule ? well , a molecule is mostly empty space . almost all of its mass is concentrated in the extremely dense nuclei of its atoms . and its electrons , which determine how the atoms are bonded to each other , are more like clouds of negative charge than individual , discrete particles . so , a molecule does n't have a shape in the same way that , for example , a statue has a shape . but for every molecule , there 's at least one way to arrange the nuclei and electrons so as to maximize the attraction of opposite charges and minimize the repulsion of like charges . now , let 's assume that the only electrons that matter to a molecule 's shape are the outermost ones from each participating atom . and let 's also assume that the electron clouds in between atoms , in other words , a molecule 's bonds , are shaped kind of like sausages . remember that nuclei are positively charged and electrons are negatively charged , and if all of a molecule 's nuclei were bunched up together or all of its electrons were bunched up together , they would just repel each other and fly apart , and that does n't help anyone . in 1776 , alessandro volta , decades before he would eventually invent batteries , discovered methane . now , the chemical formula of methane is ch4 . and this formula tells us that every molecule of methane is made up of one carbon and four hydrogen atoms , but it does n't tell us what 's bonded to what or how they atoms are arranged in 3d space . from their electron configurations , we know that carbon can bond with up to four other atoms and that each hydrogen can only bond with one other atom . so , we can guess that the carbon should be the central atom bonded to all the hydrogens . now , each bond represents the sharing of two electrons and we draw each shared pair of electrons as a line . so , now we have a flat representation of this molecule , but how would it look in three dimensions ? we can reasonably say that because each of these bonds is a region of negative electric charge and like charges repel each other , the most favorable configuration of atoms would maximize the distance between bonds . and to get all the bonds as far away from each other as possible , the optimal shape is this . this is called a tetrahedron . now , depending on the different atoms involved , you can actually get lots of different shapes . ammonia , or nh3 , is shaped like a pyramid . carbon dioxide , or co2 , is a straight line . water , h2o , is bent like your elbow would be bent . and chlorine trifluoride , or clf3 , is shaped like the letter t. remember that what we 've been doing here is expanding on our model of atoms and electrons to build up to 3d shapes . we 'd have to do experiments to figure out if these molecules actually do have the shapes we predict . spoiler alert : most of the do , but some of them do n't . now , shapes get more complicated as you increase the number of atoms . all the examples we just talked about had one obviously central atom , but most molecules , from relatively small pharmaceuticals all the way up to long polymers like dna or proteins , do n't . the key thing to remember is that bonded atoms will arrange themselves to maximize the attraction between opposite charges and minimize the repulsion between like charges . some molecules even have two or more stable arrangements of atoms , and we can actually get really cool chemistry from the switches between those configurations , even when the composition of that molecule , that 's to say the number and identity of its atoms , has not changed at all .
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now , shapes get more complicated as you increase the number of atoms . all the examples we just talked about had one obviously central atom , but most molecules , from relatively small pharmaceuticals all the way up to long polymers like dna or proteins , do n't . the key thing to remember is that bonded atoms will arrange themselves to maximize the attraction between opposite charges and minimize the repulsion between like charges .
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the optimal way to arrange a molecule having four regions of electron density surrounding a central atom looks most like
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there have been many different things written and said about marriage . from the sweetly inspirational to the hilariously cynical . but what many of them have in common is that they sound like they express a universal and timeless truth , when in fact nearly everything about marriage , from its main purpose to the kinds of relationships it covers to the rights and responsibilities involved , has varied greatly between different eras , cultures and social classes . so , let 's take a quick look at the evolution of marriage . pair bonding and raising children is as old as humanity itself . with the rise of sedentary agricultural societies about 10,000 years ago , marriage was also a way of securing rights to land and property by designating children born under certain circumstances as rightful heirs . as these societies became larger and more complex , marriage became not just a matter between individuals and families , but also an official institution governed by religious and civil authorities . and it was already well established by 2100 b.c . when the earliest surviving written laws in the mesopotamian code of ur-nammu provided many specifics governing marriage , from punishments for adultery to the legal status of children born to slaves . many ancient civilizations allowed some form of multiple simultaneous marriage . and even today , less than a quarter of the world 's hundreds of different cultures prohibit it . but just because something was allowed does n't mean it was always possible . demographic realities , as well as the link between marriage and wealth , meant that even though rulers and elites in ancient mesopotamia , egypt and israel had multiple concubines or wives , most commoners could only afford one or two tending towards monogamy in practice . in other places , the tables were turned , and a woman could have multiple husbands as in the himalayan mountains where all brothers in a family marrying the same woman kept the small amount of fertile land from being constantly divided into new households . marriages could vary not only in the number of people they involved but the types of people as well . although the names and laws for such arrangements may have differed , publicly recognized same-sex unions have popped up in various civilizations throughout history . mesopotamian prayers included blessings for such couples , while native american two-spirit individuals had relationships with both sexes . the first instances of such arrangements actually being called `` marriage '' come from rome , where the emperors nero and elagabalus both married men in public ceremonies with the practice being explictly banned in 342 a.d . but similar traditions survived well into the christian era , such as adelphopoiesis , or `` brother-making '' in orthodox churches , and even an actual marriage between two men recorded in 1061 at a small chapel in spain . nor was marriage even necessarily between two living people . ghost marriages , where either the bride or groom were deceased , were conducted in china to continue family lineages or appease restless spirits . and some tribes in sudan maintain similar practices . despite all these differences , a lot of marriages throughout history did have one thing in common . with crucial matters like property and reproduction at stake , they were way too important to depend on young love . especially among the upperclasses , matches were often made by families or rulers . but even for commoners , who had some degree of choice , the main concern was practicality . the modern idea of marriage as being mainly about love and companionship only emerged in the last couple of centuries . with industrialization , urbanization and the growth of the middle class more people became independent from large extended families and were able to support a new household on their own . encouraged by new ideas from the enlightenment , people began to focus on individual happiness and pursuits , rather than familial duty or wealth and status , at least some of the time . and this focus on individual happiness soon led to other transformations , such as easing restrictions on divorce and more people marrying at a later age . so , as we continue to debate the role and definition of marriage in the modern world , it might help to keep in mind that marriage has always been shaped by society , and as a society 's structure , values and goals change over time , its ideas of marriage will continue to change along with them .
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pair bonding and raising children is as old as humanity itself . with the rise of sedentary agricultural societies about 10,000 years ago , marriage was also a way of securing rights to land and property by designating children born under certain circumstances as rightful heirs . as these societies became larger and more complex , marriage became not just a matter between individuals and families , but also an official institution governed by religious and civil authorities .
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what was the main purpose of marriage in agricultural societies ?
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when you think of archimedes ' `` eureka ! '' moment , you probably think of this . as it turns out , it may have been more like this . in the third century bc , hieron , king of the sicilian city of syracuse , chose archimedes to supervise an engineering project of unprecedented scale . hieron commissioned a sailing vessel 50 times bigger than a standard ancient warship , named the syracusia after his city . hieron wanted to construct the largest ship ever , which was destined to be given as a present for egypt 's ruler , ptolemy . but could a boat the size of a palace possibly float ? in archimedes 's day , no one had attempted anything like this . it was like asking , `` can a mountain fly ? '' king hieron had a lot riding on that question . hundreds of workmen were to labor for years on constructing the syracusia out of beams of pine and fir from mount etna , ropes from hemp grown in spain , and pitch from france . the top deck , on which eight watchtowers were to stand , was to be supported not by columns , but by vast wooden images of atlas holding the world on his shoulders . on the ship 's bow , a massive catapult would be able to fire 180 pound stone missiles . for the enjoyment of its passengers , the ship was to feature a flower-lined promenade , a sheltered swimming pool , and bathhouse with heated water , a library filled with books and statues , a temple to the goddess aphrodite , and a gymnasium . and just to make things more difficult for archimedes , hieron intended to pack the vessel full of cargo : 400 tons of grain , 10,000 jars of pickled fish , 74 tons of drinking water , and 600 tons of wool . it would have carried well over a thousand people on board , including 600 soldiers . and it housed 20 horses in separate stalls . to build something of this scale , only for that to sink on its maiden voyage ? well , let 's just say that failure would n't have been a pleasant option for archimedes . so he took on the problem : will it sink ? perhaps he was sitting in the bathhouse one day , wondering how a heavy bathtub can float , when inspiration came to him . an object partially immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object . in other words , if a 2,000 ton syracusia displaced exactly 2,000 tons of water , it would just barely float . if it displaced 4,000 tons of water , it would float with no problem . of course , if it only displaced 1,000 tons of water , well , hieron would n't be too happy . this is the law of buoyancy , and engineers still call it archimedes ' principle . it explains why a steel supertanker can float as easily as a wooden rowboat or a bathtub . if the weight of water displaced by the vessel below the keel is equivalent to the vessel 's weight , whatever is above the keel will remain afloat above the waterline . this sounds a lot like another story involving archimedes and a bathtub , and it 's possible that 's because they 're actually the same story , twisted by the vagaries of history . the classical story of archimedes ' eureka ! and subsequent streak through the streets centers around a crown , or corona in latin . at the core of the syracusia story is a keel , or korone in greek . could one have been mixed up for the other ? we may never know . on the day the syracusia arrived in egypt on its first and only voyage , we can only imagine how residents of alexandria thronged the harbor to marvel at the arrival of this majestic , floating castle . this extraordinary vessel was the titanic of the ancient world , except without the sinking , thanks to our pal , archimedes .
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when you think of archimedes ' `` eureka ! '' moment , you probably think of this .
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what greek city did archimedes come from ?
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on july 26 , 1943 , los angeles was blanketed by a thick gas that stung people 's eyes and blocked out the sun . panicked residents believed their city had been attacked using chemical warfare . but the cloud was n't an act of war . it was smog . a portmanteau of smoke and fog , the word smog was coined at the beginning of the 20th century to describe the thick gray haze that covered cities such as london , glasgow , and edinburgh . this industrial smog was known to form when smoke from coal-burning home stoves and factories combined with moisture in the air . but the smog behind the la panic was different . it was yellowish with a chemical odor . since the city did n't burn much coal , its cause would remain a mystery until a chemist named arie haagen-smit identified two culprits , volatile organic compounds , or vocs , and nitrous oxides . vocs are compounds that easily become vapors and may contain elements , such as carbon , oxygen , hydrogen , chlorine , and sulfur . some are naturally produced by plants and animals , but others come from manmade sources , like solvents , paints , glues , and petroleum . meanwhile , the incomplete combustion of gas in motor vehicles releases nitrous oxide . that 's what gives this type of smog its yellowish color . vocs and nitrous oxide react with sunlight to produce secondary pollutants called pans and tropospheric , or ground level , ozone . pans and ozone cause eye irritation and damage lung tissue . both are key ingredients in photochemical smog , which is what had been plaguing la . so why does smog affect some cities but not others ? both industrial and photochemical smog combine manmade pollution with local weather and geography . london 's high humidity made it a prime location for industrial smog . photochemical smog is strongest in urban areas with calm winds and dry , warm , sunny weather . the ultraviolet radiation from sunlight provides the energy necessary to breakdown molecules that contribute to smog formation . cities surrounded by mountains , like la , or lying in a basin , like beijing , are also especially vulnerable to smog since there 's nowhere for it to dissipate . that 's also partially due to a phenomenon known as temperature inversion , where instead of warm air continuously rising upward , a pollution-filled layer of air remains trapped near the earth 's surface by a slightly warmer layer above . smog is n't just an aesthetic eyesore . both forms of smog irritate the eyes , nose , and throat , exacerbate conditions like asthma and emphysema , and increase the risk of respiratory infections like bronchitis . smog can be especially harmful to young children and older people and exposure in pregnant women has been linked to low birth weight and potential birth defects . secondary pollutants found in photochemical smog can damage and weaken crops and decrease yield , making them more susceptible to insects . yet for decades , smog was seen as the inevitable price of civilization . londoners had become accustomed to the notorious pea soup fog swirling over their streets until 1952 , when the great smog of london shut down all transportation in the city for days and caused more than 4,000 respiratory deaths . as a result , the clean air act of 1956 banned burning coal in certain areas of the city , leading to a massive reduction in smog . similarly , regulations on vehicle emissions and gas content in the us reduced the volatile compounds in the air and smog levels along with them . smog remains a major problem around the world . countries like china and poland that depend on coal for energy experience high levels of industrial smog . photochemical smog and airborne particles from vehicle emissions affect many rapidly developing cities , from mexico city and santiago to new delhi and tehran . governments have tried many methods to tackle it , such as banning cars from driving for days at a time . as more than half of the world 's population crowds into cities , considering a shift to mass transit and away from fossil fuels may allow us to breathe easier .
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meanwhile , the incomplete combustion of gas in motor vehicles releases nitrous oxide . that 's what gives this type of smog its yellowish color . vocs and nitrous oxide react with sunlight to produce secondary pollutants called pans and tropospheric , or ground level , ozone .
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which product of incomplete combustion gives photochemical smog its yellowish color ?
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myths and misconceptions about evolution . let 's talk about evolution . you 've probably heard that some people consider it controversial , even though most scientists do n't . but even if you are n't one of those people and you think you have a pretty good understanding of evolution , chances are you still believe some things about it that are n't entirely right , things like , `` evolution is organisms adapting to their environment . '' this was an earlier , now discredited , theory of evolution . almost 60 years before darwin published his book , jean-baptiste lamarck proposed that creatures evolve by developing certain traits over their lifetimes and then passing those on to their offspring . for example , he thought that because giraffes spent their lives stretching to reach leaves on higher branches , their children would be born with longer necks . but we know now that 's not how genetic inheritance works . in fact , individual organisms do n't evolve at all . instead , random genetic mutations cause some giraffes to be born with longer necks , and that gives them a better chance to survive than the ones who were n't so lucky , which brings us to `` survival of the fittest '' . this makes it sound like evolution always favors the biggest , strongest , or fastest creatures , which is not really the case . for one thing , evolutionary fitness is just a matter of how well-suited they are to their current environment . if all the tall trees suddenly died out and only short grass was left , all those long-necked giraffes would be at a disadvantage . secondly , survival is not how evolution occurs , reproduction is . and the world if full of creatures like the male anglerfish , which is so small and ill-suited for survival at birth that it has to quickly find a mate before it dies . but at least we can say that if an organism dies without reproducing , it 's evolutionarily useless , right ? wrong ! remember , natural selection happens not at the organism level , but at the genetic level , and the same gene that exists in one organism will also exist in its relatives . so , a gene that makes an animal altruistically sacrifice itself to help the survival and future reproduction of its siblings or cousins , can become more widespread than one that is solely concerned with self-preservation . anything that lets more copies of the gene pass on to the next generation will serve its purpose , except evolutionary purpose . one of the most difficult things to keep in mind about evolution is that when we say things like , `` genes want to make more copies of themselves , '' or even , `` natural selection , '' we 're actually using metaphors . a gene does n't want anything , and there 's no outside mechanism that selects which genes are best to preserve . all that happens is that random genetic mutations cause the organisms carrying them to behave or develop in different ways . some of those ways result in more copies of the mutated gene being passed on , and so forth . nor is there any predetermined plan progressing towards an ideal form . it 's not ideal for the human eye to have a blind spot where the optic nerve exits the retina , but that 's how it developed , starting from a simple photoreceptor cell . in retrospect , it would have been much more advantageous for humans to crave nutrients and vitamins rather than just calories . but over the millenia , during which our ancestors evolved , calories were scarce , and there was nothing to anticipate that this would later change so quickly . so , evolution proceeds blindly , step by step by step , creating all of the diversity we see in the natural world .
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this makes it sound like evolution always favors the biggest , strongest , or fastest creatures , which is not really the case . for one thing , evolutionary fitness is just a matter of how well-suited they are to their current environment . if all the tall trees suddenly died out and only short grass was left , all those long-necked giraffes would be at a disadvantage .
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why are humans not ideally adapted to their current environment ?
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translator : andrea mcdonough reviewer : bedirhan cinar people often think the word `` doubt '' spelling is a little crazy because of the letter `` b '' . since it does n't spell a sound , most folks ca n't figure out what it 's doing there . but in spite of what most of us learn in school , sound is < i > never < /i > the most important aspect of spelling an english word . a word 's meaning and history need to come first . to doubt means to question , to waver , to hesitate . as a noun , it means uncertainty or confusion . the present-day english word `` doubt '' started as a latin word , `` dubitare '' . it first moved from latin into french where it lost both its `` buh '' sound and its letter `` b '' . and then it came into english in the 13th century . about 100 years later , scribes who wrote english but also knew latin , started to reinsert the `` b '' into the word 's spelling , even though no one pronounced it that way . but why would they do this ? why would anyone in their right mind reinsert a silent letter into a spelling ? well , because they knew latin , the scribes understood that the root of `` doubt '' had a `` b '' in it . over time , even as fewer literate people knew latin , the `` b '' was kept because it marked important , meaningful connections to other related words , like `` dubious '' and `` indubitalbly , '' which were subsequently borrowed into english from the same latin root , `` dubitare '' . understanding these historical connections not only helped us to spell `` doubt , '' but also to understand the meaning of these more sophisticated words . but the story does n't end there . if we look even deeper , we can see beyond the shadow of a doubt , just how revealing that `` b '' can be . there are only two base words in all of english that have the letters `` d-o-u-b '' : one is doubt , and the other is double . we can build lots of other words on each of these bases , like doubtful and doubtless , or doublet , and redouble , and doubloon . it turns out that if we look into their history , we can see that they both derive from the same latin forms . the meaning of double , two , is reflected in a deep understanding of doubt . see , when we doubt , when we hesitate , we second guess ourselves . when we have doubts about something , when we have questions or confusion , we are of two minds . historically , before english began to borrow words from french , it already had a word for doubt . that old english word was `` tweogan , '' a word whose relationship to `` two '' is clear in its spelling as well . so the next time you are in doubt about why english spelling works the way it does , take a second look . what you find just might make you do a double-take .
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if we look even deeper , we can see beyond the shadow of a doubt , just how revealing that `` b '' can be . there are only two base words in all of english that have the letters `` d-o-u-b '' : one is doubt , and the other is double . we can build lots of other words on each of these bases , like doubtful and doubtless , or doublet , and redouble , and doubloon .
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find three words with silent letters . why are those letters present in the words today ?
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translator : andrea mcdonough reviewer : bedirhan cinar every cell in your body is separated from those around it by its outermost layer , its membrane . a cell membrane must be both sturdy and flexible . imagine a membrane made of metal - great at keeping the cell 's guts inside , but horrible at letting materials flow in and out . but a membrane made of fishnet stocking would go too far in the opposite direction - leaky , but easily torn . so , the ideal membrane falls somewhere in the middle . over the past few centuries , we 've learned a lot about the way membranes work . the tale starts in the late 1800 's when , according to legend , a german woman named agnes pockels was doing dishes . her observation , that not all detergents dissolve grease in the same way , piqued her curiosity , so she made careful measurements of the size of soapy films that formed on the surface of a metal tray filled with water . later , in the 1920 's , ge scientists irving langmuir and katharine blodgett reexamined the problem with a more elaborate contraption and found that those tiny slicks were in fact a single layer of oil molecules . each oil molecule has one side that loves water and floats on the surface , and one side that loathes water and protrudes into the air . so what does it have to do with cell membranes ? well , at the turn of the 20th century , chemists charles overton and hans meyer demonstrated that the cell membrane is composed of substances that , like oil , have a water-loving part and a water-loathing part . we now call these substances lipids . in 1925 , two scientists , evert gorter and francois grendel , pushed our understanding further . they designed an experiment meant to test whether cell membranes are made of only one layer of lipids , a monolayer , or two layers stacked on top of one another , called a bilayer . gorter and grendel drew blood from a dog , a sheep , a rabbit , a goat , a guinea pig , and human volunteers . from each of these samples , they extracted all the lipids from all the red blood cells and placed a few drops of this extract on a tray of water . true to form , the lipids , like oil , spread out into a monolayer , whose size gorter and grendel could measure . if they compared the surface area of that monolayer to the surface area to the intact red blood cells , they 'd be able to tell whether the red blood cell membrane is one or two layers thick . to understand the design of their experiment , imagine looking down at a sandwich . if you measure the surface area of what you see , you 'll get the dimensions of a single slice of bread even though there are two slices , one stacked perfectly atop the other . but , if you open the sandwich and place the two slices side by side , you get twice the surface area . the gorter and grendel experiment is basically the same idea . the open sandwich is the monolayer formed by extracted cellular lipids spreading out into a sheet . the closed sandwich is the intact red blood cell membrane . low and behold , they observed a two-to-one ratio , proving beyond the shadow of a doubt that a cell membrane is a bilayer , which when unstacked , yields a monolayer twice its size . so almost 30 years before the double-helix structure of dna was elucidated , a single experiment involving fancy versions of household materials enabled deep insight into the basic architecture of the cell .
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translator : andrea mcdonough reviewer : bedirhan cinar every cell in your body is separated from those around it by its outermost layer , its membrane . a cell membrane must be both sturdy and flexible . imagine a membrane made of metal - great at keeping the cell 's guts inside , but horrible at letting materials flow in and out . but a membrane made of fishnet stocking would go too far in the opposite direction - leaky , but easily torn .
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a cell membrane 's construction can be likened to a metal jacket . it 's strong and sturdy , keeping all the contents of a cell securely in tact .
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translator : andrea mcdonough reviewer : bedirhan cinar one of the grandest scientific tools ever made by mankind is called an atom smasher . and i mean literally grand . the biggest one ever built , the large hadron collider , or lhc , is a ring with a circumference of about 18 miles . that 's more than the entire length of manhattan . so what is an atom smasher ? it is a device that collides atomic nuclei together at extremely high energy . the most powerful one scientists have ever built can heat matter to the hottest temperatures ever achieved , temperatures last seen at a trillionth of second after the universe began . our accelerators are full of engineering superlatives . the beam-containing region of the lhc is a vacuum , with lower pressure than what surrounds the international space station , and is 456 degrees fahrenheit below zero , colder than the temperature of deepest space . a previous accelerator sitting in the lhc tunnel holds the world record for velocity , accelerating an electron to a speed so fast that if it were to race a photon of light , it would take about 14 minutes for the photon to get a lead of about 10 feet . if that does n't impress you , remember the photon is fastest thing in the universe , it goes about 186,000 miles per second . so how do these subatomic particle accelerators work ? well , they use electric fields . electric fields make charged particles move in the same way that gravity will pull a dropped baseball . the force from the electric field will pull a particle to make it move . the speed will continue to increase until the charged particle is moving incredibly fast . a simple particle accelerator can be made by hooking two parallel metal plates to a battery . the charge from the battery moves on to the two metal plates and makes an electric field that pulls the particle along . and that 's it , you got a particle accelerator . the problem is that an accelerator built this way is very weak . building a modern accelerator like the lhc this way would take over five trillion standard d-cell batteries . so scientists use much stronger batteries and put them one after another . an earlier accelerator used this method and was about a mile long and was equivalent to 30 billion batteries . however , to make an accelerator that is equivalent to five trillion batteries would require an accelerator 150 miles long . scientists needed another way . while electric fields would make a particle go faster , magnetic fields make them move in a circular path . if you put an electric field along the circle , you do n't need to use miles of electric fields , you can use a single electric field over and over again . the beams go around the circle , and each time they gain more energy . so very high-energy accelerators consist of a short region with accelerating electric fields , combined with long series of magnets that guide the particles in a circle . the strength of the magnets and the radius of the circular path determines the maximum energy of the beam . once the beam is zooming along , then the real fun begins , the smashing . the reason physicists want to get those particles moving so fast is so that they can slam them into one another . these collisions can teach us about the fundamental rules that govern matter , but they 'd be impossible without the feat of engineering that is the particle accelerator .
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so how do these subatomic particle accelerators work ? well , they use electric fields . electric fields make charged particles move in the same way that gravity will pull a dropped baseball .
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you ’ ve heard that electric fields are required to increase the speed of subatomic particles , yet most of a circular accelerator is surrounded by magnets . why do physicists not simply put electric fields around the entire ring ?
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europium is an element which , when you excite the atoms or excite the electrons in the atoms , gives out very nice red coloured light . ok , so europium is pretty much in the middle of the lanthanide series . perhaps its most famous use is in television screens . in fact , most or many of the rare earths can fluoresce in this way and give out light , but europium is particularly good at giving a very nice red colour , and so europium salts are used in television screens , not lcd screens like you have on the laptop , but the old-fashioned cathode ray televisions . so it ’ s very good at phosphorescence , for example , so we use it in the tubes in tv screens to get different colours . the screen on the inside of the screen you have dots of europium and when the electrons from the electron beam in the cathode ray tube hit the europium you get a very intense emission of red light which gives you the red colour to form the colour television pictures .
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ok , so europium is pretty much in the middle of the lanthanide series . perhaps its most famous use is in television screens . in fact , most or many of the rare earths can fluoresce in this way and give out light , but europium is particularly good at giving a very nice red colour , and so europium salts are used in television screens , not lcd screens like you have on the laptop , but the old-fashioned cathode ray televisions . so it ’ s very good at phosphorescence , for example , so we use it in the tubes in tv screens to get different colours .
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it used to be found in old tvs but , which common energy-saving devices use europium nowadays ?
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translator : jenny zurawell one of the funny things about owning a brain is that you have no control over the things that it gathers and holds onto , the facts and the stories . and as you get older , it only gets worse . things stick around for years sometimes before you understand why you 're interested in them , before you understand their import to you . here 's three of mine . when richard feynman was a young boy in queens , he went for a walk with his dad and his wagon and a ball . he noticed that when he pulled the wagon , the ball went to the back of the wagon . he asked his dad , `` why does the ball go to the back of the wagon ? '' and his dad said , `` that 's inertia . '' he said , `` what 's inertia ? '' and his dad said , `` ah . inertia is the name that scientists give to the phenomenon of the ball going to the back of the wagon . '' ( laughter ) `` but in truth , nobody really knows . '' feynman went on to earn degrees at mit , princeton , he solved the challenger disaster , he ended up winning the nobel prize in physics for his feynman diagrams , describing the movement of subatomic particles . and he credits that conversation with his father as giving him a sense that the simplest questions could carry you out to the edge of human knowledge , and that that 's where he wanted to play . and play he did . eratosthenes was the third librarian at the great library of alexandria , and he made many contributions to science . but the one he is most remembered for began in a letter that he received as the librarian , from the town of swenet , which was south of alexandria . the letter included this fact that stuck in eratosthenes ' mind , and the fact was that the writer said , at noon on the solstice , when he looked down this deep well , he could see his reflection at the bottom , and he could also see that his head was blocking the sun . i should tell you -- the idea that christopher columbus discovered that the world is spherical is total bull . it 's not true at all . in fact , everyone who was educated understood that the world was spherical since aristotle 's time . aristotle had proved it with a simple observation . he noticed that every time you saw the earth 's shadow on the moon , it was circular , and the only shape that constantly creates a circular shadow is a sphere , q.e.d . the earth is round . but nobody knew how big it was until eratosthenes got this letter with this fact . so he understood that the sun was directly above the city of swenet , because looking down a well , it was a straight line all the way down the well , right past the guy 's head up to the sun . eratosthenes knew another fact . he knew that a stick stuck in the ground in alexandria at the same time and the same day , at noon , the sun 's zenith , on the solstice , the sun cast a shadow that showed that it was 7.2 degrees off-axis . if you know the circumference of a circle , and you have two points on it , all you need to know is the distance between those two points , and you can extrapolate the circumference . 360 degrees divided by 7.2 equals 50 . i know it 's a little bit of a round number , and it makes me suspicious of this story too , but it 's a good story , so we 'll continue with it . he needed to know the distance between swenet and alexandria , which is good because eratosthenes was good at geography . in fact , he invented the word geography . ( laughter ) the road between swenet and alexandria was a road of commerce , and commerce needed to know how long it took to get there . it needed to know the exact distance , so he knew very precisely that the distance between the two cities was 500 miles . multiply that times 50 , you get 25,000 , which is within one percent of the actual diameter of the earth . he did this 2,200 years ago . now , we live in an age where multi-billion-dollar pieces of machinery are looking for the higgs boson . we 're discovering particles that may travel faster than the speed of light , and all of these discoveries are made possible by technology that 's been developed in the last few decades . but for most of human history , we had to discover these things using our eyes and our ears and our minds . armand fizeau was an experimental physicist in paris . his specialty was actually refining and confirming other people 's results , and this might sound like a bit of an also-ran , but in fact , this is the soul of science , because there is no such thing as a fact that can not be independently corroborated . and he was familiar with galileo 's experiments in trying to determine whether or not light had a speed . galileo had worked out this really wonderful experiment where he and his assistant had a lamp , each one of them was holding a lamp . galileo would open his lamp , and his assistant would open his . they got the timing down really good . they just knew their timing . and then they stood at two hilltops , two miles distant , and they did the same thing , on the assumption from galileo that if light had a discernible speed , he 'd notice a delay in the light coming back from his assistant 's lamp . but light was too fast for galileo . he was off by several orders of magnitude when he assumed that light was roughly ten times as fast as the speed of sound . fizeau was aware of this experiment . he lived in paris , and he set up two experimental stations , roughly 5.5 miles distant , in paris . and he solved this problem of galileo 's , and he did it with a really relatively trivial piece of equipment . he did it with one of these . i 'm going to put away the clicker for a second because i want to engage your brains in this . so this is a toothed wheel . it 's got a bunch of notches and it 's got a bunch of teeth . this was fizeau 's solution to sending discrete pulses of light . he put a beam behind one of these notches . if i point a beam through this notch at a mirror , five miles away , that beam is bouncing off the mirror and coming back to me through this notch . but something interesting happens as he spins the wheel faster . he notices that it seems like a door is starting to close on the light beam that 's coming back to his eye . why is that ? it 's because the pulse of light is not coming back through the same notch . it 's actually hitting a tooth . and he spins the wheel fast enough and he fully occludes the light . and then , based on the distance between the two stations and the speed of his wheel and the number of notches in the wheel , he calculates the speed of light to within two percent of its actual value . and he does this in 1849 . this is what really gets me going about science . whenever i 'm having trouble understanding a concept , i go back and i research the people that discovered that concept . i look at the story of how they came to understand it . what happens when you look at what the discoverers were thinking about when they made their discoveries , is you understand that they are not so different from us . we are all bags of meat and water . we all start with the same tools . i love the idea that different branches of science are called fields of study . most people think of science as a closed , black box , when in fact it is an open field . and we are all explorers . the people that made these discoveries just thought a little bit harder about what they were looking at , and they were a little bit more curious . and their curiosity changed the way people thought about the world , and thus it changed the world . they changed the world , and so can you . thank you . ( applause )
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but for most of human history , we had to discover these things using our eyes and our ears and our minds . armand fizeau was an experimental physicist in paris . his specialty was actually refining and confirming other people 's results , and this might sound like a bit of an also-ran , but in fact , this is the soul of science , because there is no such thing as a fact that can not be independently corroborated .
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armand fizeau improved upon galileo ’ s
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hi , i 'm john green , this is crash course us history and today we 're going to talk about what america 's best at : war . [ patriotic rock music ] uh , mr. green , the united states has actually only declared war 5 times in the last 230 years . oh me from the the past , you sniveling literalist . well today we 're going to talk about america 's first declared war , the war of 1812 , so called because historians are terrible at naming things . i mean the could have called it the revolutionary war : part deux , or the canadian cataclysm , or the war to facilitate future wars . but no , they just named it after the year it started . [ theme music ] i know this disappoints the military historians among you , but as usual , we 're gon na spend more time talking about the causes and effects of the war than the actual , like , killing parts , because ultimately it 's the ambiguity of the war of 1812 that makes it so interesting . the reason most often given for the war of 1812 was the british impressment of american sailors , whereby american sailors would be kidnapped and basically forced into british servitude . this disrupted american shipping and also seems like a reasonably obvious violation of american sovereignty , but it 's a little more complicated than that . first of all , there were many thousands of british sailors working aboard american ships so many of the sailors that the british captured were in fact british . which gets to the large point that citizenship at the time was a pretty slippery concept especially on the high seas . like , papers were often forged , and many sailors identified supposed american-ness through tattoos of like eagles and flags . and there were several reasons why a british sailor might like to become , or pretend to be , an american , including that the brits at the time were fighting napoleon in what historians , in their infinite creativity , called the napoleonic wars . and on that topic , britain 's impressment policy allowed them both to disrupt american shipping to france and get new british sailors to strengthen their war effort , which was annoying to the americans on a couple levels especially the french-loving republicans , which is a phrase that you do n't hear very often anymore . another reason often given for the war , was america 's crazy conspiratorial anglophobia . there was even a widespread rumor that british agents were buying up connecticut sheep in order to sabotage the textile industry , lest you worry that america 's fascination with conspiracy theories is new . so those pushing for war were known as war hawks , and the most famous among them was kentucky 's henry clay . they took the impressment of sailors as an affront to american national honor , but they also complained that britain 's actions were an affront to free trade , by which they meant america 's ability to trade with europeans other than great britain . and to be fair , the british were trying to regulate american trade . they even passed the orders in counsel which required american ships to dock in britain and pay tax before trading with other european nations . britain , we were an independent nation ! you ca n't do that kind of stuff ! we have a special relationship but it 's not that special ! but the problem with saying that this caused the war was that the orders had been in effect for five years before the war started . and they were rescinded in 1812 before the us declared war . although , admittedly , we did n't know about it because it did n't reach us until after we declared . there was no twitter . another reason for the war was canada . that 's right canada , american 's wanted you and who can blame them we your excellent healthcare and your hockey and your first rate national anthem . stan this is fun but enough with the # 1812problems . according to the virginia congressman john randolph , `` agrarian cupidity not maritime rights urges the war . we have heard but one word : canada , canada , canada . '' i 'm not here to criticize you john randolph but that 's actually three words . now some historians disagree with this but the relentless pursuit of new land certainly fits in with the jeffersonian model of an agrarian republic . and there 's another factor that figured into america 's decision to go to war : expansion into territory controlled by native americans . oh , it 's time for the mystery document ? the rules here are simple : i try to guess the author of the mystery document . usually i 'm wrong and i get shocked . all right , let ’ s see what we got here . `` you want , by your distinctions of indian tribes , in allotting to each a particular tract of land , to make them to war with each other . you never see an indian come and endeavor to make the white people do so . '' it 's tecumseh . drop the mic ... [ dinging noise ] is something that i would do except that the mic is actually attached to my shirt so there 's n– there 's no drama in this . clearly a native american criticism of white people , and i happen to know that that particular one comes from tecumseh and i do n't get shocked today . so it should n't come as a surprise that americans were continuing to push westward into territories where indians were living . i mean , this was a big reason for the louisiana purchase after all . by the beginning of the war , more than 400,000 settlers had moved into territories west of the original 13 colonies and they outnumbered american indians by a significant margin . some native groups responded with a measure of assimilation . cherokees like john ross wanted to become more `` civilized '' , that is , more white and farmer-y . and some of them did even adopt such civilized practices as written languages and slavery , the most civilized practice of all . [ sigh ] people are always like , `` why are n't you more celebratory of american history ? '' well , why is n't there more to celebrate ? but other indians wanted to resist . the best known of these were the aforementioned tecumseh and his brother tensk – stan , can you just put it on the screen ? [ tenskwatawa on screen ] yes . let 's just enjoy looking at that . right , that 's just for all you visual learners . so he was also known as the prophet , because of his religious teachings , and also because of the pronunciation issues . the prophet encouraged indians , especially those living in and around the settlement of prophetstown , to abandon the ways of the whites , primarily in the form of alcohol and manufactured consumer goods . so stop drinking alcohol and eating refined sugars – this guy sounds like my doctor ! tecumseh was more militant ; attempting to revive neolin 's idea of pan-indianism and actively resisting white settlement . as he put it , `` sell a country , why not sell the air , the great sea , as well as the earth ? did not the great spirit make them all for the use of his children ? '' the americans responded to this reasonable criticism in the traditional manner – with guns . william henry harrison destroyed the native settlement at prophetstown in what would become known as the battle of tippecanoe . he would later ride that fame all the way to the presidency in 1840 and then – spoiler alert : he would give the longest inauguration address ever , catch a cold , and die 40 days later . let that be a lesson to you , american politicians : long speeches ? fatal ! so i just painted a pretty negative picture of the american treatment of the indians – because it was awful . but i have n't mentioned how this relates to the war of 1812 . the americans were receiving reports that the british were encouraging tecumseh , which they probably were . and the important thing to remember here is that the war of 1812 , like the seven years war and the american revolution was also a war against indians . and as in those other two wars , the indians were the biggest losers . and not in the cool way of biggest loser where , like , trainer bob helps you lose weight , but in the really sad way , where your entire civilization gets john c. calhouned . so the war of 1812 was the first time that the united states declared war on anybody . it was also the smallest margin of a declaration of war vote : 79 to 49 in the house and 19 to 13 in the senate . northern states , which relied on trade a lot , did n't want to go to war , while southern and western states , which were more agrarian and wanted expansion to get land for farming and slavery , did . the closeness of the vote reflects a profound ambivalence about the war . as henry adams wrote , `` many nations have gone to war in pure gaiety of the heart , but perhaps the united states were the first to force themselves into a war they dreaded , in the hope that the war itself might create the spirit they lacked . '' do n't worry , henry adams ! in the future we 're gon na get pretty gaiety of heart-ish about war . anyway , as an actual war , the war of 1812 was something of a farce . let 's go to the thought bubble . the us army numbered 10-12 thousand and its officers were sunk into either sloth , ignorance , or habits of intemperate drinking . the us navy had 17 ships . great britain had 1,000 . also , america had very little money , britain collected 40 times more tax revenue than the us . but britain was busy fighting napoleon , which is why they did n't really start kicking america 's butt until 1814 , after napoleon was defeated . napoleon 's defeat was also the practice of impressment , since britain did n't need so many sailors anymore . initially , much of the war consisted of america 's attempts to take canada , which any map will show you went smashingly . americans were confident the canadians would rush to join the us . when marching from detroit , general william hull informed the canadians that , `` you will be emancipated from tyranny and oppression and restored to the dignified station of free men . '' and the canadians were like , `` yeah , we 're okay actually . '' and so the british in canada , with their indian allies , went ahead and captured detroit and then forced hull 's surrender . america 's lack of success in canada was primarily attributable to terrible strategy . they might have succeeded if they 'd taken montreal , but they did n't want to march through northern new york because it was full of federalists who were opposed to the war . instead they concentrated on the west , that is , the area around detroit , where fighting went back and forth . the british found much more success , even seizing washington dc and burning the white house . in the course of the battle , british admiral george cockburn , overseeing the destruction of a newspaper printing house , told the forces that took the city , `` be sure that all the cs are destroyed , so that the rascals can not any longer abuse my name . it 's hard out there for a cockburn . thanks , thought bubble . given these problems it 's amazing there were any american successes , but there were . the battleship uss constitution broke the myth of british naval invincibility when cannonballs bounced off it and earned it the nickname `` old ironsides '' . oliver hazard perry defeated a british fleet , in , of all places , lake erie . at the battle of the thames , william harry harrison defeated tecumseh . and the battle of horseshoe ben showed one of the reasons why indians were defeated when andrew jackson played one group of creeks against another group of creeks and cherokees . 800 indians were killed in that battle . and speaking of jackson , the most notable american victory of the war was the battle of new orleans , which catapulted him to prominence . he lost only 71 men while inflicting 2,036 british casualties . of course , the most memorable thing about the battle is that it took place two weeks after the peace treaty ending the war had been signed . but hey , that 's not jackson 's fault . again – no twitter , # 1815problems . the treaty of ghent , which ended the war , proved just how necessary the war had been : not at all . no territory changed hands when negotiations started . and in august 1814 , the british asked for northern maine , demilitarization of the great lakes , and some territory to create an independent nation for the indians , and the northwest . but none of that happened , not because the u.s. was in a particularly good negotiating position , but it would have been awkward for great britain to carve out pieces of the us , and then tell russia and prussia that they could n't take pieces of europe for themselves to celebrate their victory in the napoleonic wars . there were no provisions in the treaty about impressment or free trade and basically the treaty returned everything to the status quo . so , neither the us or great britain actually won . but the indians suffered significant casualties and gave up even more territory , definitely lost . so with a treaty like that , the war must have had a negligible impact on american history , right ? except , no ; the war of 1812 confirmed that the us would exist . britain would never invade american again ( until 1961 ) . i mean the us were good customers , and great britain was happy to let them trade , as long as that trade was n't helping a french dictator . the war launched andrew jackson 's career and solidified the settlement and conquest of land east of the mississippi river . and our lack of success in canada reinforced canadian nationalism while also ensuring that instead of becoming one great nation , we would forever be canada 's pants . the war also spelled the end of the federalist party , which tried in 1815 with the hartford convention to change the constitution . in retrospect , the hartford convention proposals actually look pretty reasonable . they wanted to eliminate the clause wherein black people were counted as 3/5 of a human , and require a 2/3 congressional majority to declare war . but because they had their convention right before jackson 's victory at new orleans , they only came off looking unpatriotic and out of touch , as the elite so often do . it 's hard to argue that the americans really won the war of 1812 , but we felt like we won , and nothing unleashes national pride like war winning . the nationalistic fervor that emerged in the early 19th century , was , like most things , good news for some and bad news for others . but what ’ s important to remember , regardless of whether you 're an american , is that after 1812 , the united states saw itself not just as an independent nation but as a big player on the world stage . for better and for worse , that 's a gig we 've held onto . and no matter how you feel about america 's international interventions , you need to remember , it did n't begin in afghanistan or even europe ; it started with freakin ' canada . thanks for watching , i 'll see you next week . crash course is produced and directed by stan muller . the script supervisor is meredith danko . our show is written by my high school history teacher raoul meyer and myself . our associate producer is danica johnson . and our graphics team is thought cafe . if you have questions about today 's video , you can ask them in comments , where they will be answered by our team of historians . we also accept suggestions for libertage captions . thanks for watching crash course and as we say in my hometown : do n't forget to be awesome . goodbye ! do n't forget to subscribe !
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oh me from the the past , you sniveling literalist . well today we 're going to talk about america 's first declared war , the war of 1812 , so called because historians are terrible at naming things . i mean the could have called it the revolutionary war : part deux , or the canadian cataclysm , or the war to facilitate future wars .
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why do historians find fault with the argument that the `` orders in council '' caused the war of 1812 ?
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in 1996 , 56 volunteers took part in a study to test a new painkiller called trivaricaine . on each subject , one index finger was covered in the new painkiller while the other remained untouched . then , both were squeezed in painful clamps . the subjects reported that the treated finger hurt less than the untreated one . this should n't be surprising , except trivaricaine was n't actually a painkiller , just a fake concotion with no pain-easing properties at all . what made the students so sure this dummy drug had worked ? the answer lies in the placebo effect , an unexplained phenomenon wherein drugs , treatments , and therapies that are n't supposed to have an effect , and are often fake , miraculously make people feel better . doctors have used the term placebo since the 1700s when they realized the power of fake drugs to improve people 's symptoms . these were administered when proper drugs were n't available , or if someone imagined they were ill . in fact , the word placebo means `` i shall please '' in latin , hinting at a history of placating troubled patients . placebos had to mimic the real treatments in order to be convincing , so they took the form of sugar pills , water-filled injections , and even sham surgeries . soon , doctors realized that duping people in this way had another use : in clinical trials . by the 1950s , researchers were using placebos as a standard tool to test new treatments . to evaluate a new drug , for instance , half the patients in a trial might receive the real pill . the other half would get a placebo that looked the same . since patients would n't know whether they 'd received the real thing or a dud , the results would n't be biased , researchers believed . then , if the new drug showed a significant benefit compared to the placebo , it was proved effective . nowadays , it 's less common to use placebos this way because of ethical concerns . if it 's possible to compare a new drug against an older version , or another existing drug , that 's preferable to simply giving someone no treatment at all , especially if they have a serious ailment . in these cases , placebos are often used as a control to fine-tune the trial so that the effects of the new versus the old or alternative drug can be precisely compared . but of course , we know the placebos exert their own influence , too . thanks to the placebo effect , patients have experienced relief from a range of ailments , including heart problems , asthma , and severe pain , even though all they 'd received was a fake drug or sham surgery . we 're still trying to understand how . some believe that instead of being real , the placebo effect is merely confused with other factors , like patients trying to please doctors by falsely reporting improvements . on the other hand , researchers think that if a person believes a fake treatment is real , their expectations of recovery actually do trigger physiological factors that improve their symptoms . placebos seem to be capable of causing measurable change in blood pressure , heart rate , and the release of pain-reducing chemicals , like endorphins . that explains why subjects in pain studies often say placebos ease their discomfort . placebos may even reduce levels of stress hormones , like adrenaline , which can slow the harmful effects of an ailment . so should n't we celebrate the placebo 's bizarre benefits ? not necessarily . if somebody believes a fake treatment has cured them , they may miss out on drugs or therapies that are proven to work . plus , the positive effects may fade over time , and often do . placebos also cloud clinical results , making scientists even more motivated to discover how they wield such power over us . despite everything we know about the human body , there are still some strange and enduring mysteries , like the placebo effect . so what other undiscovered marvels might we contain ? it 's easy to investigate the world around us and forget that one of its most fascinating subjects lies right behind our eyes .
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nowadays , it 's less common to use placebos this way because of ethical concerns . if it 's possible to compare a new drug against an older version , or another existing drug , that 's preferable to simply giving someone no treatment at all , especially if they have a serious ailment . in these cases , placebos are often used as a control to fine-tune the trial so that the effects of the new versus the old or alternative drug can be precisely compared .
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why is it considered ethically questionable to give someone a placebo if another working treatment is available ?
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so krypton is one of the noble gases , it ’ s not very reactive but it does react with the element fluorine . jim turner , who was my supervisor when i did my doctorate , was the first person to discover that fluorine could react with krypton but even that reaction requires quite bright lights to break the bond between the fluorine atoms to get them to react . but krypton can also be used in lasers when mixtures of krypton and of fluorine-containing compound can be used to generate very bright pulses or intense pulses of ultraviolet light . some years ago we had a professor here who bought a really big krypton-fluoride laser and when he switched it on and the beam hit the wall it burnt a hole right through the wall so he knew where to make the hole to get his beam into the next lab .
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jim turner , who was my supervisor when i did my doctorate , was the first person to discover that fluorine could react with krypton but even that reaction requires quite bright lights to break the bond between the fluorine atoms to get them to react . but krypton can also be used in lasers when mixtures of krypton and of fluorine-containing compound can be used to generate very bright pulses or intense pulses of ultraviolet light . some years ago we had a professor here who bought a really big krypton-fluoride laser and when he switched it on and the beam hit the wall it burnt a hole right through the wall so he knew where to make the hole to get his beam into the next lab .
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what link does krypton have with the nobel prize in chemistry ?
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what does the french revolution have to do with the time nasa accidentally crashed a $ 200 million orbiter into the surface of mars ? actually , everything . that crash happened due to an error in converting between two measurement systems , u.s. customary units and their s.i , or metric , equivalence . so what 's the connection to the french revolution ? let 's explain . for the majority of recorded human history , units like the weight of a grain or the length of a hand were n't exact and varied from place to place . and different regions did n't just use varying measurements . they had completely different number systems as well . by the late middle ages , the hindu-arabic decimal system mostly replaced roman numerals and fractions in europe , but efforts by scholars like john wilkins to promote standard decimal-based measures were less successful . with a quarter million different units in france alone , any widespread change would require massive disruption . and in 1789 , that disruption came . the leaders of the french revolution did n't just overthrow the monarchy . they sought to completely transform society according to the rational principles of the enlightenment . when the new government took power , the academy of sciences convened to reform the system of measurements . old standards based on arbitrary authority or local traditions were replaced with mathematical and natural relationships . for example , the meter , from the greek word for measure , was defined as 1/10,000,000 between the equator and north pole . and the new metric system was , in the words of the marquis de condorcet , `` for all people , for all time . '' standardizing measurements had political advantages for the revolutionaries as well . nobles could no longer manipulate local units to extract more rent from commoners , while the government could collect taxes more efficiently . and switching to a new republican calendar with ten-day weeks reduced church power by eliminating sundays . adoption of this new system was n't easy . in fact , it was a bit of a mess . at first , people used new units alongside old ones , and the republican calendar was eventually abandoned . when napoléon bonaparte took power , he allowed small businesses to use traditional measurements redefined in metric terms . but the metric system remained standard for formal use , and it spread across the continent , along with france 's borders . while napoléon 's empire lasted eight years , its legacy endured far longer . some european countries reverted to old measurements upon independence . others realized the value of standardization in an age of international trade . after portugal and the netherlands switched to metric voluntarily , other nations followed , with colonial empires spreading the system around the world . as france 's main rival , britain had resisted revolutionary ideas and retained its traditional units . but over the next two centuries , the british empire slowly transitioned , first approving the metric system as an optional alternative before gradually making it offical . however , this switch came too late for thirteen former colonies that had already gained independence . the united states of america stuck with the english units of its colonial past and today remains one of only three countries which have n't fully embraced the metric system . despite constant initiatives for metrication , many americans consider units like feet and pounds more intuitive . and ironically , some regard the once revolutionary metric system as a symbol of global conformity . nevertheless , the metric system is almost universally used in science and medicine , and it continues to evolve according to its original principles . for a long time , standard units were actually defined by carefully maintained physical prototypes . but thanks to improving technology and precision , these objects with limited access and unreliable longevity are now being replaced with standards based on universal constants , like the speed of light . consistent measurements are such an integral part of our daily lives that it 's hard to appreciate what a major accomplishment for humanity they 've been . and just as it arose from a political revolution , the metric system remains crucial for the scientific revolutions to come .
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despite constant initiatives for metrication , many americans consider units like feet and pounds more intuitive . and ironically , some regard the once revolutionary metric system as a symbol of global conformity . nevertheless , the metric system is almost universally used in science and medicine , and it continues to evolve according to its original principles .
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what might common french citizens have liked about the metric system when it was adopted ? what might they have disliked ? why ?
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when the infamous fictional character , carrie white , left her high school prom hall ablaze , and brought terror upon her town , she relied on her powers of telekinesis , the ability to manipulate physical objects using the power of the mind alone . but while carrie is just a fictional film based upon a fictional book , belief in telekinesis is n't fictional at all . for centuries , humans have claimed they really do have the power to control the motion of objects using only their minds . levitation , opening doors at will and spoon bending are all intriguing examples . it happens in the matrix when neo freezes bullets midair , and it 's a skill that yoda has honed to a t. but is telekinesis real , or just as fictional as carrie , yoda and neo combined ? to investigate , we need to evaluate telekinetic claims through a scientific lens using the scientific method . telekinesis is part of the discipline called parapsychology , in which researchers study psychic phenomena . parapsychologists regard what they do as a science , but other scientists disagree . let 's start with a few basic observations . observation # 1 : while there are loads of anecdotes out there about telekinesis , there 's no scientific proof that it exists ; no studies conducted according to the scientific method and repeated under lab conditions can show that its real . in the 1930s , the so-called father of parapsychology , joseph banks rhine , tested in the lab whether people could use telekinesis to make a dice roll the way they wanted it to . but afterwards , scientists could n't replicate his results , and since replication is key to proving an idea , that was a problem . aside from scientists , there are also countless self-proclaimed telekinetics , but all have been exposed as tricksters , or ca n't perform under conditions where they 're not totally in control , suggesting that they manipulate the situation to get the results they want . today , there 's even a huge stash of prize money available from lots of organizations for anyone who can prove that psychic abilities , like telekinesis , are real . but these riches remain unclaimed . observation # 2 : when we investigate telekinesis , there 's no consensus about what exactly is being measured . are powerful , yoda-like brainwaves at work perhaps ? since nobody agrees , it 's difficult to apply a research standard , something required in all other types of science to test the validity of ideas . observation # 3 : the point of science is to discover the unknown , and in the history of scientific investigation , it 's definitely happened that new discoveries have gone against established science , and even overturned whole branches of science . such discoveries must be proven extra carefully to withstand skepticism . in the case of telekinesis , the idea goes against established science , but lacks the powerful evidence in favor of it . our universe is controlled and explained by the laws of physics , and one of these laws tells us that brain waves ca n't control objects because they 're neither strong nor far-reaching enough to influence anything outside of our skulls . physics also tells us that the only forces that can influence objects from afar are magnetic and gravitational . probably the closest thing to telekinesis that science can explain is the use of thoughts to control a robotic arm . in the brains of stroke patients who ca n't move , researchers can implant tiny wires into the region that controls movement , and then train the patient to concentrate on moving a robotic arm , which acts like an extension of their minds , and it works . it 's amazing , but it is n't telekinesis . the patients thoughts are n't just vague , undetectable things . they 're measurable brain signals , translated through wires into a robot . science can measure , test and explain the motion , and that 's how we 've shown that this kind of mind control is real . science is a slow process of accumulating the evidence that either stands for or against an idea . when we stack up evidence , we can see which tower grows tallest , and in the case of telekinesis , it 's not the tower showing that it exists . some say this mystical phenomenon ca n't fit within the confines of science , and that 's okay . but then telekinesis becomes purely a matter of personal conviction . if something ca n't be assessed scientifically , then it ca n't be described as scientific either . so the results of our investigation reveal that however much we may want to believe that the force really is within us , the case for telekinesis remains weak . sorry neo , carrie and yoda . your skills are mind-blowing , but for now , they belong in the movies .
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in the 1930s , the so-called father of parapsychology , joseph banks rhine , tested in the lab whether people could use telekinesis to make a dice roll the way they wanted it to . but afterwards , scientists could n't replicate his results , and since replication is key to proving an idea , that was a problem . aside from scientists , there are also countless self-proclaimed telekinetics , but all have been exposed as tricksters , or ca n't perform under conditions where they 're not totally in control , suggesting that they manipulate the situation to get the results they want .
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why do you think it ’ s so important that scientists are able to replicate each other ’ s experiments ?
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modern computers are revolutionizing our lives , performing tasks unimaginable only decades ago . this was made possible by a long series of innovations , but there 's one foundational invention that almost everything else relies upon : the transistor . so what is that , and how does such a device enable all the amazing things computers can do ? well , at their core , all computers are just what the name implies , machines that perform mathematical operations . the earliest computers were manual counting devices , like the abacus , while later ones used mechanical parts . what made them computers was having a way to represent numbers and a system for manipulating them . electronic computers work the same way , but instead of physical arrangements , the numbers are represented by electric voltages . most such computers use a type of math called boolean logic that has only two possible values , the logical conditions true and false , denoted by binary digits one and zero . they are represented by high and low voltages . equations are implemented via logic gate circuits that produce an output of one or zero based on whether the inputs satisfy a certain logical statement . these circuits perform three fundamental logical operations , conjunction , disjunction , and negation . the way conjunction works is an `` and gate '' provides a high-voltage output only if it receives two high-voltage inputs , and the other gates work by similar principles . circuits can be combined to perform complex operations , like addition and subtraction . and computer programs consist of instructions for electronically performing these operations . this kind of system needs a reliable and accurate method for controlling electric current . early electronic computers , like the eniac , used a device called the vacuum tube . its early form , the diode , consisted of two electrodes in an evacuated glass container . applying a voltage to the cathode makes it heat up and release electrons . if the anode is at a slightly higher positive potential , the electrons are attracted to it , completing the circuit . this unidirectional current flow could be controlled by varying the voltage to the cathode , which makes it release more or less electrons . the next stage was the triode , which uses a third electrode called the grid . this is a wire screen between the cathode and anode through which electrons could pass . varying its voltage makes it either repel or attract the electrons emitted by the cathode , thus , enabling fast current-switching . the ability to amplify signals also made the triode crucial for radio and long distance communication . but despite these advancements , vacuum tubes were unreliable and bulky . with 18,000 triodes , eniac was nearly the size of a tennis court and weighed 30 tons . tubes failed every other day , and in one hour , it consumed the amount of electricity used by 15 homes in a day . the solution was the transistor . instead of electrodes , it uses a semiconductor , like silicon treated with different elements to create an electron-emitting n-type , and an electron absorbing p-type . these are arranged in three alternating layers with a terminal at each . the emitter , the base , and the collector . in this typical npn transistor , due to certain phenomena at the p-n interface , a special region called a p-n junction forms between the emitter and base . it only conducts electricity when a voltage exceeding a certain threshold is applied . otherwise , it remains switched off . in this way , small variations in the input voltage can be used to quickly switch between high and low-output currents . the advantage of the transistor lies in its efficiency and compactness . because they do n't require heating , they 're more durable and use less power . eniac 's functionality can now be surpassed by a single fingernail-sized microchip containing billions of transistors . at trillions of calculations per second , today 's computers may seem like they 're performing miracles , but underneath it all , each individual operation is still as simple as the flick of a switch .
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the ability to amplify signals also made the triode crucial for radio and long distance communication . but despite these advancements , vacuum tubes were unreliable and bulky . with 18,000 triodes , eniac was nearly the size of a tennis court and weighed 30 tons .
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why were vacuum tubes discarded ?
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every day of your life , you move through systems of power that other people made . do you sense them ? do you understand power ? do you realize why it matters ? power is something we are often uncomfortable talking about . that 's especially true in civic life , how we live together in community . in a democracy , power is supposed to reside with the people , period . any further talk about power and who really has it seems a little dirty , maybe even evil . but power is no more inherently good or evil than fire or physics . it just is . it governs how any form of government works . it determines who gets to determine the rules of the game . so learning how power operates is key to being effective , being taken seriously , and not being taken advantage of . in this lesson , we 'll look at where power comes from , how it 's exercised and what you can do to become more powerful in public life . let 's start with a basic definition . power is the ability to make others do what you would have them do . of course , this plays out in all arenas of life , from family to the workplace to our relationships . our focus is on the civic arena , where power means getting a community to make the choices and to take the actions that you want . there are six main sources of civic power . first , there 's physical force and a capacity for violence . control of the means of force , whether in the police or a militia , is power at its most primal . a second core source of power is wealth . money creates the ability to buy results and to buy almost any other kind of power . the third form of power is state action , government . this is the use of law and bureaucracy to compel people to do or not do certain things . in a democracy , for example , we the people , theoretically , give government its power through elections . in a dictatorship , state power emerges from the threat of force , not the consent of the governed . the fourth type of power is social norms or what other people think is okay . norms do n't have the centralized machinery of government . they operate in a softer way , peer to peer . they can certainly make people change behavior and even change laws . think about how norms around marriage equality today are evolving . the fifth form of power is ideas . an idea , individual liberties , say , or racial equality , can generate boundless amounts of power if it motivates enough people to change their thinking and actions . and so the sixth source of power is numbers , lots of humans . a vocal mass of people creates power by expressing collective intensity of interest and by asserting legitimacy . think of the arab spring or the rise of the tea party . crowds count . these are the six main sources of power , what power is . so now , let 's think about how power operates . there are three laws of power worth examining . law number one : power is never static . it 's always either accumulating or decaying in a civic arena . so if you are n't taking action , you 're being acted upon . law number two : power is like water . it flows like a current through everyday life . politics is the work of harnessing that flow in a direction you prefer . policymaking is an effort to freeze and perpetuate a particular flow of power . policy is power frozen . law number three : power compounds . power begets more power , and so does powerlessness . the only thing that keeps law number three from leading to a situation where only one person has all the power is how we apply laws one and two . what rules do we set up so that a few people do n't accumulate too much power , and so that they ca n't enshrine their privilege in policy ? that 's the question of democracy , and you can see each of these laws at work in any news story . low wage workers organize to get higher pay . oil companies push to get a big pipeline approved . gay and lesbian couples seek the legal right to marry . urban parents demand school vouchers . you may support these efforts or not . whether you get what you want depends on how adept you are with power , which brings us finally to what you can do to become more powerful in public life . here , it 's useful to think in terms of literacy . your challenge is to learn how to read power and write power . to read power means to pay attention to as many texts of power as you can . i do n't mean books only . i mean seeing society as a set of texts . do n't like how things are in your campus or city or country ? map out who has what kind of power , arrayed in what systems . understand why it turned out this way , who 's made it so , and who wants to keep it so . study the strategies others in such situations used : frontal attack or indirection , coalitions or charismatic authority . read so you may write . to write power requires first that you believe you have the right to write , to be an author of change . you do . as with any kind of writing , you learn to express yourself , speak up in a voice that 's authentic . organize your ideas , then organize other people . practice consensus building . practice conflict . as with writing , it 's all about practice . every day you have a chance to practice , in your neighborhood and beyond . set objectives , then bigger ones . watch the patterns , see what works . adapt , repeat . this is citizenship . in this short lesson , we 've explored where civic power comes from , how it works and what you can do to exercise it . one big question remaining is the `` why '' of power . do you want power to benefit everyone or only you ? are your purposes pro-social or anti-social ? this question is n't about strategy . it 's about character , and that 's another set of lessons . but remember this : power plus character equals a great citizen , and you have the power to be one .
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policymaking is an effort to freeze and perpetuate a particular flow of power . policy is power frozen . law number three : power compounds .
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explain the statement : policy is frozen power .
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translator : andrea mcdonough reviewer : bedirhan cinar i would like to introduce you to one of the most amazing scientists who have ever lived . so famous , that more places on earth have been named after him than any human being . so famous , that president thomas jefferson said he was the most important scientist he ever met . and simon bolivar called him the true discoverer of south america . on the 100th anniversary of his birth , every story on the front page of < i > the new york times < /i > was written about him . who is this scientist and what did he do that was so extraordinary ? his name is alexander von humboldt . never heard of him ? most people have n't . his name has been lost in history , but here is what he did . alexander von humboldt started as a practicing geologist , but when an inheritance allowed him the freedom to travel , he began an incredible , five-year scientific journey through south america , mexico , and cuba . from 1799 to 1804 , von humboldt and his botonist partner , aime bonpland , traveled through the jungles of venezuela , made detailed drawings of inca ruins while exploring the mountains of peru , and traversed the breadth of mexico and cuba . he explored the length of the orinoco river in venezuela . this 1700 mile portion of the trip was filled with danger , disease , and fantastic new discoveries . for example , von humboldt was the first explorer to witness the preparation of the curare plant for poison arrows . he recognized the importance of the cinchona tree , whose bark contains quinine , which is a malaria cure , and discovered the ocean current , which limits rainfall on the coast of peru , later named the humboldt current . he discovered and described many new species of plants and animals , including the electric eel . in ecuador , he climbed the one of the highest volcanoes , chimborazo , so that he could record air pressure , something no one had ever done at this altitude . the entire journey covered over 24,000 miles , the same distance as the circumference of the earth . along the way , he took measurements about the shape of the land , its temperature , the air pressure , and the strength of magnetic fields . by connecting places of identical temperatures , he created contour maps with lines of similar temperatures , which he called `` isotherms '' . because humboldt invented these maps , scientists began to see patterns in the life and the types of life present in certain places , and he became a pioneer in the visual presentation of scientific data . these discoveries and measurements were critical to what made him such an important scientist . until humboldt , scientists who described new plants and animals did not clearly see the crucial connection between living things and the places in which they lived , called habitats . they did not appreciate the role of the environment on the diversity of life . humboldt discovered and understood the importance of these connections . because of this , he is considered the founder of biogeography . he also developed a theory called the `` unity of nature , '' which shows the interconnectedness of all nature . this knowledge plays a vital role in the preservation and protection of our habitat . his book , < i > cosmos < /i > , describes this theory and is still in print today . as celebrated a scientist as he was , von humboldt was also generous , thus serving another role in the world . he was the mentor and teacher to younger scientists . in fact , just recently it was discovered the crucial role that humboldt played in the work of his most famous pen-pal , charles darwin . a young darwin read humboldt extensively and wrote in his diary while on the beagle , `` i am at present fit only to read humboldt . he , like another sun , illuminates everything i behold . '' today , although humboldt is known and revered by a small community of scientists , he is almost totally forgotten by many of us . alexander von humboldt 's influence is apparent everywhere and in every scientific discipline . he is , perhaps , the most important forgotten man of science . but he does n't have to be , because if you remember him , perhaps his influence will be celebrated .
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who is this scientist and what did he do that was so extraordinary ? his name is alexander von humboldt . never heard of him ?
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which continent did alexander von humboldt and aime bonpland explore from 1799 to 1804 ?
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ok , today we 're going to talk about the mole . now , i know what you 're thinking : `` i know what a mole is , it 's a small furry creature that digs holes in the ground and destroys gardens . '' and some of you might be thinking that it 's a growth on your aunt 's face with hairs sticking out of it . well , in this case , a mole is a concept that we use in chemistry to count molecules , atoms , just about anything extremely small . have you ever wondered how many atoms there are in the universe ? or in your body ? or even in a grain of sand ? scientists have wanted to answer that question , but how do you count something as small as an atom ? well , in 1811 , someone had an idea that if you had equal volumes of gases , at the same temperature and pressure , they would contain an equal number of particles . his name was lorenzo romano amedeo carlo avogadro . i wonder how long it took him to sign autographs . unfortunately for avogadro , most scientists did n't accept the idea of the atom , and there was no way to prove he was right . there was no clear difference between atoms and molecules . most scientists looked at avogadro 's work as purely hypothetical , and did n't give it much thought . but it turned out he was right ! by late 1860 , avogadro was proven correct , and his work helped lay the foundation for the atomic theory . unfortunately , avogadro died in 1856 . now the thing is that the amount of particles in even small samples is tremendous . for example , if you have a balloon of any gas at zero degrees celcius , and at a pressure of one atmosphere , then you have precisely six hundred and two sextillion gas particles . that is , you have six with 23 zeros after it particles of gas in the container . or in scientific notation , 6.02 times 10 to the 23rd particles . this example is a little misleading , because gases take up a lot of space due to the high kinetic energy of the gas particles , and it leaves you thinking atoms are bigger than they really are . instead , think of water molecules . if you pour 18.01 grams of water into a glass , which is 18.01 milliliters , which is like three and a half teaspoons of water , you 'll have 602 sextillion molecules of water . since lorenzo romano - uh , never mind - avogadro was the first one to come up with this idea , scientists named the number 6.02 times 10 to the 23rd after him . it is simply known as avogadros 's number . now , back to the mole . not that mole . this mole . yep , this number has a second name . the mole . chemists use the term mole to refer to the quantities that are at the magnitude of 602 sextillion . this is known as a molar quantity . atoms and molecules are so small , that chemists have bundled them into groups called moles . moles are hard for students to understand because they have a hard time picturing the size of a mole , or of 602 sextillion . it 's just too big to wrap our brains around . remember our 18.01 milliliters of water ? well , that 's a mole of water . but how much is that ? exactly what does 602 sextillion look like ? maybe this 'll help . exchange the water particles for donuts . if you had a mole of donuts , they would cover the entire earth to a depth of eight kilometers , which is about five miles . you really need a lot of coffee for that . if you had a mole of basketballs , you could create a new planet the size of the earth . if you received a mole of pennies on the day you were born and spent a million dollars a second until the day you died at the age of 100 , you would still have more than 99.99 % of your money in the bank . ok. now we sort of have an idea how large the mole is . so how do we use it ? you might be surprised to know that chemists use it the same way you use pounds to buy grapes , deli meat , or eggs . when you go to the grocery store , you do n't go to the deli counter and ask for 43 slices of salami , you buy your salami by the pound . when you buy your eggs , you buy a dozen eggs . when we hear the word dozen , we probably think of the number 12 . we also know that a pair is two , a baker 's dozen is 13 , a gross is 144 , and a ream of paper is - anybody ? a ream is 500 . well , a mole is really the same thing . for a chemist , a mole conjures up the number 6.02 times 10 to the 23rd , not a fuzzy little animal . the only difference is that the other quantities are more familiar to us . so there you have it - the story of the mole , avogadro , basketballs , and how to buy salami at the grocery store .
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now , back to the mole . not that mole . this mole . yep , this number has a second name .
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why do you think chemists prefer using the mole ? why do n't they just count each particle ?
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hey there and welcome to life noggin . a lot can change over the course of a century . in the early 20th century , einstein wrote his theory of relativity . in 1953 , dr. jonas salk announced that he had successfully created a polio vaccine . and in 1990 , the world wide web was invented . but what about changes over a longer period of time , like a few million years ? obviously , the earth was a drastically different place , but it makes me wonder : could you , a modern human , survive on earth 2.5 million years ago ? to start off , let ’ s talk about the environment . you , my friend , would be living in the pleistocene epoch , which spanned from 2.6 millions years ago to 11,700 years ago . this was the time period in which the most recent ice ages took place . during the peak periods where most of the water on earth was ice , the global average temperatures were 5 to 10 degrees celsius colder than they are today . this was a much cooler and drier earth . so already , unless you have an incredibly insulating jacket , your chances of survival are looking pretty slim . during this time , you may also have bumped into one of your earliest human ancestors -- homo habilis . this species looked more like apes than humans , but were able to walk on their back legs and use their hands to make stone tools , hence its name , which means “ handy man ” . but , luckily for you , if you encountered one of them , scientists are unsure if it would attack . the general consensus is that homo habilis were vegetarians and did not hunt anything but small game . so , in this sense , you may not be in direct harm . but what about diseases ? the prevailing idea on the origin of human diseases is that many of them arose once animals were domesticated . however , with new data , it ’ s thought that diseases like tapeworms , mycobacterial infections , tuberculosis , and leprosy were around during the pleistocene epoch . and scientists believe that the bacteria b. bronchiseptica , which infected hominids 2.5 million years ago , may have evolved into the bacteria that is now responsible for whooping cough . and even more , scientists have recently determined that the parasites that cause malaria were around 2.5 million years ago . the parasites were relatively benign at that time , and malaria only became a major disease after agriculture and dense human populations arose . but if you were living 2.5 million years ago , without access to any of today ’ s medicine , you would probably not make it too long . well that ’ s quite a sad note to end on . to lighten the mood a bit , let me know what you would most want to see from 2.5 million years ago . make sure you come back every monday for a brand new video . as always , i ’ m blocko and this has been life noggin . don ’ t forget to keep on thinking !
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so already , unless you have an incredibly insulating jacket , your chances of survival are looking pretty slim . during this time , you may also have bumped into one of your earliest human ancestors -- homo habilis . this species looked more like apes than humans , but were able to walk on their back legs and use their hands to make stone tools , hence its name , which means “ handy man ” .
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describe the basic traits of homo habilis .
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you 've probably heard that carbon dioxide is warming the earth , but how does it work ? is it like the glass of a greenhouse or like an insulating blanket ? well , not entirely . the answer involves a bit of quantum mechanics , but do n't worry , we 'll start with a rainbow . if you look closely at sunlight separated through a prism , you 'll see dark gaps where bands of color went missing . where did they go ? before reaching our eyes , different gases absorbed those specific parts of the spectrum . for example , oxygen gas snatched up some of the dark red light , and sodium grabbed two bands of yellow . but why do these gases absorb specific colors of light ? this is where we enter the quantum realm . every atom and molecule has a set number of possible energy levels for its electrons . to shift its electrons from the ground state to a higher level , a molecule needs to gain a certain amount of energy . no more , no less . it gets that energy from light , which comes in more energy levels than you could count . light consists of tiny particles called photons and the amount of energy in each photon corresponds to its color . red light has lower energy and longer wavelengths . purple light has higher energy and shorter wavelengths . sunlight offers all the photons of the rainbow , so a gas molecule can choose the photons that carry the exact amount of energy needed to shift the molecule to its next energy level . when this match is made , the photon disappers as the molecule gains its energy , and we get a small gap in our rainbow . if a photon carries too much or too little energy , the molecule has no choice but to let it fly past . this is why glass is transparent . the atoms in glass do not pair well with any of the energy levels in visible light , so the photons pass through . so , which photons does carbon dioxide prefer ? where is the black line in our rainbow that explains global warming ? well , it 's not there . carbon dioxide does n't absorb light directly from the sun . it absorbs light from a totally different celestial body . one that does n't appear to be emitting light at all : earth . if you 're wondering why our planet does n't seem to be glowing , it 's because the earth does n't emit visible light . it emits infared light . the light that our eyes can see , including all of the colors of the rainbow , is just a small part of the larger spectrum of electromagnetic radiation , which includes radio waves , microwaves , infrared , ultraviolet , x-rays , and gamma rays . it may seem strange to think of these things as light , but there is no fundamental difference between visible light and other electromagnetic radiation . it 's the same energy , but at a higher or lower level . in fact , it 's a bit presumptuous to define the term visible light by our own limitations . after all , infrared light is visible to snakes , and ultraviolet light is visible to birds . if our eyes were adapted to see light of 1900 megahertz , then a mobile phone would be a flashlight , and a cell phone tower would look like a huge lantern . earth emits infrared radiation because every object with a temperature above absolute zero will emit light . this is called thermal radiation . the hotter an object gets , the higher frequency the light it emits . when you heat a piece of iron , it will emit more and more frequencies of infrared light , and then , at a temperature of around 450 degrees celsius , its light will reach the visible spectrum . at first , it will look red hot . and with even more heat , it will glow white with all of the frequencies of visible light . this is how traditional light bulbs were designed to work and why they 're so wasteful . 95 % of the light they emit is invisible to our eyes . it 's wasted as heat . earth 's infrared radiation would escape to space if there were n't greenhouse gas molecules in our atmophere . just as oxygen gas prefers the dark red photons , carbon dioxide and other greenhouse gases match with infrared photons . they provide the right amount of energy to shift the gas molecules into their higher energy level . shortly after a carbon dioxide molecule absorbs an infrared photon , it will fall back to its previous energy level , and spit a photon back out in a random direction . some of that energy then returns to earth 's surface , causing warming . the more carbon dioxide in the atmosphere , the more likely that infrared photons will land back on earth and change our climate .
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before reaching our eyes , different gases absorbed those specific parts of the spectrum . for example , oxygen gas snatched up some of the dark red light , and sodium grabbed two bands of yellow . but why do these gases absorb specific colors of light ?
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oxygen gas snatched up some of the ________ .
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two or three days ago , i got a letter from one of our fans and it ’ s different from any other letter that we have ever had , because this fan , young , has attached to it a sample of an element and what ’ s more it is an element that i had never seen . it ’ s scandium . it ’ s only a small piece but according to my colleague steve , it ’ s a very expensive element , so this might be quite valuable , and scandium is a really interesting element , much more interesting than i realised , when i first talked about it on the video . scandium is an element which chemists usually ignore , i have never used scandium in any of my research . it was one of the elements that mendeleev predicted ought to exist when he first devised the periodic table , when he made it there were lots of elements which were not known , but what he did was to predict that there were holes in various places where he felt that there ought to be an element and because obviously these elements did not have names , he called them ekea boron or ekea aluminium or ekea silicon meaning underneath those elements . and the triumph of the periodic table was that people actually discovered these elements . and the first one that was discovered was the element gallium ( ekea aluminium ) and the second one was ekea boron which is scandium . now you might think that it is a bit surprising because if you look at a modern periodic table , scandium and boron are really quite a long way apart but in the original way that medeleev started the periodic table when he wrote it down first , scandium and boron came very close together because both of them , have three electrons in their outer shell which makes their chemistry quite similar . of course medeleev did not know about electrons , but he guessed from looking at titanium which has four electrons and calcium which has two that he thought there was something missing and what is also interesting about these three elements that he predicted is that they all ended up with names of countries . there was gallium that was named after france , from the latin word for france . scandium that was named after , well perhaps not a country but a region , scandinavia , and then germanium , that was named after germany . the first time that an element was discovered , when gallium was discovered , people said well it was just luck , but when scandium was discovered , they really began to take mendeleev pretty seriously , and by the time germanium was discovered they really all decided that mendeleev was right . scandium , because it is an uncommon element , is one where people don ’ t know much about the chemistry . i have never really done any research in this area but like many elements suddenly there comes a time where they become really quite popular and topical and now is the time for scandium and the reason is that scandium is a really light metal . its density is slightly less than 4 , that ’ s 4 grams per cubic centimetre and that is very much lighter than most metals . copper is nearly 10 and lead and gold are close to 20 , so this is really very light . so why should metals be important if they are light , and that ’ s , the reason is sometimes you want to use a metal , but you don ’ t want the object you make to be very heavy and so for example titanium which is very light , is used for making everything from golf clubs to jet fighter planes , where you want it to be really light either so that you can swing it fast or fly fast . for scandium the reasons are rather different , people are now thinking about using hydrogen , to power cars , to use hydrogen gas , to use hydrogen gas as the fuel to power cars , but what they want to do is to store the hydrogen , in the equivalent of the petrol tank . you can ’ t just pressurise the hydrogen as in a gas cylinder because the container would be so heavy , that your car would be like a military tank it would be so heavy . so what they want to try and do is produce a chemical compound , which is a bit like a sponge that will absorb the hydrogen and then for example if you warm it gently they hydrogen will come out , and it is here that you want the metal to be light because you want this material that you are using to store hydrogen not to weigh very much . because you have got to cart it around in your car all the time , and scandium compounds are now looking really quite promising , for storage of hydrogen , and the idea is that rather like a molecular model kit , where you have balls joined with sticks , you can use organic compounds , those of carbon and hydrogen with a little oxygen , like sticks to join together scandium atoms , and produce a structure which has a lot of holes in it and then the hydrogen can go into those holes and be stored without needing an enormous pressure . sounds like an incredibly complicated way to make a fuel tank . it is quite complicated but on the other hand , if it works , you don ’ t need to understand the chemistry . you just add the hydrogen to your tank and away you go . how can you have got to your ripe old age as a chemist and never seen scandium ? well , chemists very often use compounds , salts of metals , but it ’ s not too often that you use the metal itself and salts because they don ’ t have to be purified and so on quite as much as the metals are easier to get , they are not as expensive and so there are lots of the elements which i haven ’ t seen , but i am really quite pleased with this sample of scandium , so when i am finished i am going to frame it and hang it on my wall . so we have one of my students who works with one of my colleagues , martin schroder and the student , has done his whole project , three year project , on the chemistry of scandium , so when i got this letter i asked him : have you ever seen scandium ? and he hadn ’ t , he had never seen the metal , so he was really quite excited to see john ’ s letter .
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and the first one that was discovered was the element gallium ( ekea aluminium ) and the second one was ekea boron which is scandium . now you might think that it is a bit surprising because if you look at a modern periodic table , scandium and boron are really quite a long way apart but in the original way that medeleev started the periodic table when he wrote it down first , scandium and boron came very close together because both of them , have three electrons in their outer shell which makes their chemistry quite similar . of course medeleev did not know about electrons , but he guessed from looking at titanium which has four electrons and calcium which has two that he thought there was something missing and what is also interesting about these three elements that he predicted is that they all ended up with names of countries .
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in our periodic table , scandium and boron are quite separate , but mendeleev put them very close together . what explanation was given by the professor for this ? why is the chemistry of scandium and boron similar ?
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why do we buy certain products or choose certain brands ? this is the sort of question advertisers have always asked , and there are no easy answers . however , there is a handy tool that helps companies explore this and similar questions , and it 's called the focus group . until the 1940s , market research was often quantitative using things like sales figures and customer polls to track consumption . but this changed during world war ii . sociologists robert merton and paul lazarsfeld set out to learn how unprecedented exposure to wartime propaganda was affecting the public . instead of polling large numbers of people with straightforward questions and quantifiable answers , the researchers conducted in-person interviews , sometimes with small groups , engaging them in more open discussions . later , this method was picked up by the advertising industry with the help of consultants , like austrian-born psychologist ernest dichter , who first coined the term focus group . this new technique was a type of qualitative research focused on the nature of people 's preferences and thoughts . it could n't tell marketers what percentage of people buy a certain product or brand , but it could tell them more about the people who do , their reasoning for doing so , and even the unconscious motivations behind those reasons . rather than providing definite conclusions for business and sales , focus groups would be used for exploratory research , generating new ideas for products and marketing based on deeper understanding of consumer habits . for example , early focus groups found that contrary to popular opinion at the time , wives often had more influence than their husbands when choosing which car to buy , so chrysler shifted gears by marketing cars directly to women . and dr. dichter himself conducted focus groups for mattel to learn what girls wanted in a doll . the result was the original barbie doll . so how does a focus group work ? first , companies recruit between six and ten participants according to specific criteria that meet their research objectives . they could be mothers of children between five and seven , or teenagers planning to buy a new phone in the next three months . this is often done through professional recruiters who manage lists of people who 've agreed to participate in focus groups for payment or other rewards . during a session , participants are asked to respond to various prompts from the group moderator , like sharing their opinions on a certain product , or their emotional reactions to an advertisement . they may even be asked to do seemingly unrelated tasks , like imagining brands as animals in a zoo . the idea is that this can reveal useful information about the participant 's feelings that traditional questions might not get to . beyond these basics , many variations are possible . a focus group may have two or more moderators perhaps taking opposite sides on a question , or a researcher might be hidden in the focus group unknown to other participants to see how their answers can be influenced . and the whole process may also be observed by researchers through a one-way mirror . but although they can provide valuable insight , focus groups do have their limitations , and one of the main ones is that the simple act of observing something can change it . this principle is called observer interference . the answers participants give are likely to be affected by the presence of the researchers , social pressure from the rest of the group , or simply knowing that they 're taking part in a focus group . and because researchers often use a small sample size in a specific setting , it 's hard to generalize their results . the findings that researchers do reach from focus groups are often tested through experiments and data gathering . those put numbers on questions like how many potential customers there are and what price they 'd be willing to pay . this part of the process changes as technology evolves . but focus groups have remained largely the same for decades . perhaps when it comes to the big , important questions , there 's no substitute for people genuinely interacting with each other .
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the result was the original barbie doll . so how does a focus group work ? first , companies recruit between six and ten participants according to specific criteria that meet their research objectives .
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researchers observing the focus group commonly do this by a :
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[ stories from the sea ] [ fish tale my secret life as plankton ] how did i get here ? well , it 's a stranger story than you might think . i came from a world of drifters , a place few humans have ever seen . the world of plankton . i came from a batch of a million eggs , and only a few of us survived . when i became a larva , i moved among other drifters . [ `` plankton '' comes from the greek `` planktos '' for wandering ] my fellow plankton came in all sizes , from tiny algae and bacteria to animals longer than a blue whale . i shared my nursery with other embryos and juveniles , from clams and crabs to sea urchins and anemones . ( high pitch sound ) we drifting animals are called zooplankton . the most common animals here are copepods and krill . ( buzzing ) you could search the world over , but you 'd never find a place more diverse than my childhood home . a teaspoon of seawater can contain more than a million living creatures . it can be a pretty tough existence , though . trillions are born here , but only a few make it to adulthood . he may be no larger than a pin head , but this crab larva is an arrow worm 's worst nightmare . ( bumping noises ) ( buzzing ) epic battles between carnivores like these are just one way to get food . but the real powers of this place come from phytoplankton . single-celled life that transforms sunlight and carbon dioxide into edible gold . phytoplankton are the base for the largest food web in the world . during the night , many animals like me would rise up from the depths to feed on this sun-powered feast . ( maraca sound ) i was part of the largest daily migration of life on earth . during the day , i 'd return to the darkness , where i 'd join my bizarre companions . ( high pitch buzz ) ( flapping noises ) cannibals , like this sea butterfly mollusk , that eats its next of kin . and comb jellies , that beat cilia like rainbowed eyelashes . some of these snare their prey with sticky tentacles , while others just take a bite out of their cousins . and siphonophores that catch prey with toxic fishing lures . but my favorite would have to be the crustacean phronima . its monstrous looks inspired the movie `` aliens . '' it can catch tiny bits in its bristles , but prefers larger prey like salps . with two sets of eyes , this female prowls the deeper water . prey in hand , she performs one of the strangest behaviors in the entire animal kingdom . with body parts from her victims , she delicately assembles a barrel-like home feeding her young until they can drift off and survive on their own . best of all , they make the perfect snack for a small fish like me . here among the plankton , the food web is so tangled and complex , even scientists do n't know who eats whom . but i do . at least now you know a bit of my story . there 's so much more to me than just a tasty meal .
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i came from a world of drifters , a place few humans have ever seen . the world of plankton . i came from a batch of a million eggs , and only a few of us survived .
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why do some plankton migrate vertically ?
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translator : andrea mcdonough reviewer : bedirhan cinar you 've probably heard of the boston tea party , something about a bunch of angry colonists dressed as native americans throwing chests of tea into the water . but the story is far more complicated , filled with imperial intrigue , corporate crisis , smuggling , and the grassroots origins of the american revolution . the first thing you need to know about tea in the 1700 's is that it was really , really popular . in england , each man , woman , and child consumed almost 300 cups of this stuff every year . and , since the english colonized america , americans were crazy about tea too . by the 1760 's , they were drinking over a million pounds of tea every year . so , when britain wanted to increase taxes on tea in america , people were not happy , mostly because they had no say in tax decisions made in london . remember that famous phrase , `` no taxation without representation '' ? the american colonists had long believed that they were not subject to taxes imposed by legislature in which they lacked representation . in fact , rather than paying the taxes , they simply dodged the tax collectors . since the east coast of america is hundreds of miles long and british enforcement was lax , about 3/4 of the tea americans were drinking was smuggled in , usually from holland . but the british insisted that parliament did have the authority to tax the colonists , especially after britain went deeply into debt fighting the french in the seven years ' war . to close the budget gap , london looked to americans , and in 1767 imposed new taxes on a variety of imports , including the american 's beloved tea . america 's response : no thanks ! they boycotted the importation of tea from britain , and instead , brewed their own . after a new bunch of british customs commissioners cried to london for troops to help with tax enforcement , things got so heated that the red coats fired on a mob in boston , killing several people , in what was soon called the boston massacre . out of the terms of the 1773 tea act , parliament cooked up a new strategy . now the east india company would sell the surplus tea directly through hand-picked consignees in america . this would lower the price to consumers , making british tea competitive with the smuggled variety while retaining some of the taxes . but the colonists saw through the british ploy and cried , `` monopoly ! '' now it 's a cold and rainy december 16 , 1773 . about 5,000 bostonians are crowded into the old south meeting house , waiting to hear whether new shipments of tea that have arrived down the harbor will be unloaded for sale . when the captain of one of those ships reported that he could not leave with his cargo on board , sam adams rose to shout , `` this meeting can do no more to save the country ! '' cries of `` boston harbor a teapot tonight ! '' rang out from the crowd , and about 50 men , some apparently dressed as native americans , marched down to griffin 's wharf , stormed aboard three ships , and threw 340 tea chests overboard . an infuriated british government responsded with the so-called coercive acts of 1774 , which , among other things , closed the port of boston until the locals compensated the east india company for the tea . that never happened . representatives of the colonies gathered at philadelphia to consider how best to respond to continued british oppression . this first continental congress supported destruction of the tea , pledged to support a continued boycott , and went home in late october 1774 even more united in their determination to protect their rights and liberties . the boston tea party began a chain reaction that led with little pause to the declaration of independence and a bloody rebellion , after which the new nation was free to drink its tea , more or less , in peace .
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but the colonists saw through the british ploy and cried , `` monopoly ! '' now it 's a cold and rainy december 16 , 1773 . about 5,000 bostonians are crowded into the old south meeting house , waiting to hear whether new shipments of tea that have arrived down the harbor will be unloaded for sale .
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why did bostonians destroy the tea in december 1773 rather than simply refusing to buy it from those approved by the british to sell it ?
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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 .
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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 .
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what benefits does the muscular system provide , other than just helping you to move ?
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translator : andrea mcdonough reviewer : jessica ruby there are still lots of things about space that we may never be able to answer , like is time travel possible ? or are aliens living somewhere else in the milky way ? but there is one thing i believe about space : space is trying to kill me . space is n't out to get me personally . it 's also trying to kill you and everybody else . think about it . space does n't naturally have what we need to survive when we travel there : no air , it 's too hot or too cold , no ozone to protect us from those nasty uv rays , either . this all sounds bad , but what can space really do to me if i stay on earth ? what we need to understand is that objects in space can cause people to think their days are numbered , even when there are events on earth that can hurt or kill us before something from space does . so , what are the odds that one of these objects will really affect earth and you and me in our lifetime ? well , we can take what we know about the universe to try and figure that out . you might have heard stories about asteroids hitting the earth . that would be pretty bad . scientists think asteroids might have killed off most of the dinosaurs . sounds like something we should worry about , right ? well , astronomers can now watch asteroids in space and see them coming using complex computer models to predict the deadly rock 's path . for a while , the reported odds that asteroid apophis would strike earth in 2036 were once 1 in 625 . but , after updating their data , astronomers now say the chances are extremely low . okay , what about the sun ? hollywood movies like to pick on our sun by showing earth destroyed by solar flares or the sun dying out , which would cause earth to freeze . astronomers predict our sun contains enough gas to make energy for another 3 to 5 billion years . so , in 3 to 5 billion years , if people still exist on earth , they 'll have to deal with that . but today , well , we 're safe . sometimes the sun does shoot flares at earth , but the magnetic fields surrounding our planet blocks most of that radiation . the radiation that does get through creates things like the aurora borealis . gigantic solar flares can mess with our satellites and electrical equipment , but the chances of it killing you are pretty slim . okay , what about that supermassive black hole in the middle of our galaxy ? what happens to earth , and us , when it pulls us in ? after all , it is supermassive . nope , not going to happen . that 's one big object that ca n't bother us . how can we be so sure ? our solar system is on the edge of the milky way while the nearest supermassive black hole is about 26,000 light years from earth . that means we are n't on that black hole 's menu . so , you still think space objects are trying to kill you even after what i 've told you so far ? i think i 've even convinced myself that odds are really good that space and the objects up there wo n't kill me after all . but i 'll probably keep looking up just to make sure nothing is headed my way .
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well , astronomers can now watch asteroids in space and see them coming using complex computer models to predict the deadly rock 's path . for a while , the reported odds that asteroid apophis would strike earth in 2036 were once 1 in 625 . but , after updating their data , astronomers now say the chances are extremely low .
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design methods you believe could protect earth from asteroid impacts . justify your choice ( s ) .
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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 .
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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 .
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what are some of the different ways you can hydrate ?
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imagine this : you 're fast asleep when all of a sudden you 're awoken ! and not by your alarm clock . your eyes open , and there 's a demon sitting on your chest , pinning you down . you try to open your mouth and scream , but no sound comes out . you try to get up and run away , but you realize that you are completely immobilized . the demon is trying to suffocate you , but you ca n't fight back . you 've awoken into your dream , and it 's a nightmare . it sounds like a stephen king movie , but it 's actually a medical condition called sleep paralysis , and about half of the population has experienced this strange phenomenon at least once in their life . this panic-inducing episode of coming face-to-face with the creatures from your nightmares can last anywhere from seconds to minutes and may involve visual or auditory hallucinations of an evil spirit or an out-of-body feeling like you 're floating . some have even mistaken sleep paralysis for an encounter with a ghost or an alien abduction . in 1867 , dr. silas weir mitchell was the first medical professional to study sleep paralysis . `` the subject awakes to consciousness of his environment but is incapable of moving a muscle . lying to all appearance , still asleep . he 's really engaged for a struggle for movement , fraught with acute mental distress . could he but manage to stir , the spell would vanish instantly . '' even though dr. mitchell was the first to observe patients in a state of sleep paralysis , it 's so common that nearly every culture throughout time has had some kind of paranormal explanation for it . in medieval europe , you might think that an incubus , a sex-hungry demon in male form , visited you in the night . in scandinavia , the mare , a damned woman , is responsible for visiting sleepers and sitting on their rib cages . in turkey , a jinn holds you down and tries to strangle you . in thailand , phi am bruises you while you sleep . in the southern united states , the hag comes for you . in mexico , you could blame subirse el muerto , the dead person , on you . in greece , mora sits upon your chest and tries to asphyxiate you . in nepal , khyaak the ghost resides under the staircase . it may be easier to blame sleep paralysis on evil spirits because what 's actually happening in your brain is much harder to explain . modern scientists believe that sleep paralysis is caused by an abnormal overlap of the rem , rapid eye movement , and waking stages of sleep . during a normal rem cycle , you 're experiencing a number of sensory stimuli in the form of a dream , and your brain is unconscious and fully asleep . during your dream , special neurotransmitters are released , which paralyze almost all of your muscles . that 's called rem atonia . it 's what keeps you from running in your bed when you 're being chased in your dreams . during an episode of sleep paralysis , you 're experiencing normal components of rem . you 're dreaming and your muscles are paralyzed , only your brain is conscious and wide awake . this is what causes you to imagine that you 're having an encounter with a menacing presence . so this explains the hallucinations , but what about the feelings of panic , strangling , choking , chest pressure that so many people describe ? well during rem , the function that keeps you from acting out your dreams , rem atonia , also removes voluntary control of your breathing . your breath becomes more shallow and rapid . you take in more carbon dioxide and experience a small blockage of your airway . during a sleep paralysis episode , a combination of your body 's fear response to a perceived attack by an evil creature and your brain being wide awake while your body is in an rem sleep state triggers a response for you to take in more oxygen . that makes you gasp for air , but you ca n't because rem atonia has removed control of your breath . this struggle for air while your body sleeps creates a perceived sensation of pressure on the chest or suffocation . while a few people experience sleep paralysis regularly and it may be linked to sleep disorders such as narcolepsy , many who experience an episode of sleep paralysis do so infrequently , perhaps only once in a lifetime . so you can rest easy , knowing that an evil entity is not trying to haunt , possess , strangle , or suffocate you . save that for the horror films !
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this struggle for air while your body sleeps creates a perceived sensation of pressure on the chest or suffocation . while a few people experience sleep paralysis regularly and it may be linked to sleep disorders such as narcolepsy , many who experience an episode of sleep paralysis do so infrequently , perhaps only once in a lifetime . so you can rest easy , knowing that an evil entity is not trying to haunt , possess , strangle , or suffocate you .
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what are three common symptoms of sleep paralysis ?
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trillions of bacteria , viruses , and fungi live on or inside of us , and maintaining a good , balanced relationship with them is to our advantage . together , they form the gut microbiome , a rich ecosystem that performs a variety of functions in our bodies . the bacteria in our guts can break down food the body ca n't digest , produce important nutrients , regulate the immune system , and protect against harmful germs . we do n't yet have the blueprint for exactly which good bacteria a robust gut needs , but we do know that it 's important for a healthy microbiome to have a variety of bacterial species . many factors affect our microbiomes , including our environment , medications like antibiotics , and even whether we were delivered by c-section or not . diet , too , is emerging as one of the leading influences on the health of our guts . and while we ca n't control all these factors , we can manipulate the balance of our microbes by paying attention to what we eat . dietary fiber from foods like fruits , vegetables , nuts , legumes , and whole grains is the best fuel for gut bacteria . when bacteria digest fiber , they produce short chain fatty acids that nourish the gut barrier , improve immune function , and can help prevent inflammation , which reduces the risk of cancer . and the more fiber you ingest , the more fiber-digesting bacteria colonize your gut . in a recent study , scientists exchanged the regular high-fiber diets of a group of rural south africans with the high-fat , meat-heavy diets of a group of african-americans . after just two weeks on the high-fat , low-fiber , western-style diet , the rural african group showed increased inflammation of the colon , as well as a decrease of butyrate . that 's a short chain fatty acid thought to lower risk of colon cancer . meanwhile , the group that switched to a high-fiber , low-fat diet had the opposite result . so what goes wrong with our gut bacteria when we eat low-fiber processed foods ? lower fiber means less fuel for the gut bacteria , essentially starving them until they die off . this results in less diversity and hungry bacteria . in fact , some can even start to feed on the mucus lining . we also know that specific foods can affect gut bacteria . in one recent microbiome study , scientists found that fruits , vegetables , tea , coffee , red wine , and dark chocolate were correlated with increased bacterial diversity . these foods contain polyphenols , which are naturally occurring antioxidant compounds . on the other hand , foods high in dairy fat , like whole milk , and sugar-sweetened sodas were correlated with decreased diversity . how food is prepared also matters . minimally processed , fresh foods generally have more fiber and provide better fuel . so lightly steamed , sautéed , or raw vegetables are typically more beneficial than fried dishes . there are also ways of preparing food that can actually introduce good bacteria , also known as probiotics , into your gut . fermented foods are teeming with helpful probiotic bacteria , like lactobacillus and bifidobacteria . originally used as a way of preserving foods before the invention of refrigeration , fermentation remains a traditional practice all over the world . foods like kimchi , sauerkraut , tempeh , and kombucha provide variety and vitality to our diets . yogurt is another fermented food that can introduce helpful bacteria into our guts . that does n't necessarily mean that all yogurt is good for us , though . brands with too much sugar and not enough bacteria may not actually help . these are just general guidelines . more research is needed before we fully understand exactly how any of these foods interact with our microbiomes . we see positive correlations , but the insides of our guts are difficult places to make direct observations . for instance , we do n't currently know whether these foods are directly responsible for the changes in diversity , or if something more complicated is happening . while we 're only beginning to explore the vast wilderness inside our guts , we already have a glimpse of how crucial our microbiomes are for digestive health . the great news is we have the power to fire up the bacteria in our bellies . fill up on fibers , fresh and fermented foods , and you can trust your gut to keep you going strong .
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trillions of bacteria , viruses , and fungi live on or inside of us , and maintaining a good , balanced relationship with them is to our advantage . together , they form the gut microbiome , a rich ecosystem that performs a variety of functions in our bodies . the bacteria in our guts can break down food the body ca n't digest , produce important nutrients , regulate the immune system , and protect against harmful germs .
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what are some helpful functions that gut bacteria provide for our bodies ?
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how do you get what you want using just your words ? aristotle set out to answer exactly that question over 2,000 years ago with the treatise on rhetoric . rhetoric , according to aristotle , is the art of seeing the available means of persuasion . and today we apply it to any form of communication . aristotle focused on oration , though , and he described three types of persuasive speech . forensic , or judicial , rhetoric establishes facts and judgements about the past , similar to detectives at a crime scene . epideictic , or demonstrative , rhetoric makes a proclamation about the present situation , as in wedding speeches . but the way to accomplish change is through deliberative rhetoric , or symbouleutikon . rather than the past or the present , deliberative rhetoric focuses on the future . it 's the rhetoric of politicians debating a new law by imagining what effect it might have , like when ronald regan warned that the introduction of medicare would lead to a socialist future spent telling our children and our children 's children what it once was like in america when men were free . but it 's also the rhetoric of activists urging change , such as martin luther king jr 's dream that his children will one day live in a nation where they will not be judged by the color of their skin , but by the content of their character . in both cases , the speaker 's present their audience with a possible future and try to enlist their help in avoiding or achieving it . but what makes for good deliberative rhetoric , besides the future tense ? according to aristotle , there are three persuasive appeals : ethos , logos , and pathos . ethos is how you convince an audience of your credibility . winston churchill began his 1941 address to the u.s. congress by declaring , `` i have been in full harmony all my life with the tides which have flowed on both sides of the atlantic against privilege and monopoly , '' thus highlighting his virtue as someone committed to democracy . much earlier , in his defense of the poet archias , roman consul cicero appealed to his own practical wisdom and expertise as a politician : `` drawn from my study of the liberal sciences and from that careful training to which i admit that at no part of my life i have ever been disinclined . '' and finally , you can demonstrate disinterest , or that you 're not motivated by personal gain . logos is the use of logic and reason . this method can employ rhetorical devices such as analogies , examples , and citations of research or statistics . but it 's not just facts and figures . it 's also the structure and content of the speech itself . the point is to use factual knowledge to convince the audience , as in sojourner truth 's argument for women 's rights : `` i have as much muscle as any man and can do as much work as any man . i have plowed and reaped and husked and chopped and mowed and can any man do more than that ? '' unfortunately , speakers can also manipulate people with false information that the audience thinks is true , such as the debunked but still widely believed claim that vaccines cause autism . and finally , pathos appeals to emotion , and in our age of mass media , it 's often the most effective mode . pathos is neither inherently good nor bad , but it may be irrational and unpredictable . it can just as easily rally people for peace as incite them to war . most advertising , from beauty products that promise to relieve our physical insecurities to cars that make us feel powerful , relies on pathos . aristotle 's rhetorical appeals still remain powerful tools today , but deciding which of them to use is a matter of knowing your audience and purpose , as well as the right place and time . and perhaps just as important is being able to notice when these same methods of persuasion are being used on you .
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most advertising , from beauty products that promise to relieve our physical insecurities to cars that make us feel powerful , relies on pathos . aristotle 's rhetorical appeals still remain powerful tools today , but deciding which of them to use is a matter of knowing your audience and purpose , as well as the right place and time . and perhaps just as important is being able to notice when these same methods of persuasion are being used on you .
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if you lived during aristotle ’ s time , how do you imagine yourself as one of his students ?
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when it was ratified in 1789 , the u.s. constitution did n't just institute a government by the people . it provided a way for the people to alter the constitution itself . and yet , of the nearly 11,000 amendments proposed in the centuries since , only 27 have succeeded as of 2016 . so what is it that makes the constitution so hard to change ? in short , its creators . the founders of the united states were trying to create a unified country from thirteen different colonies , which needed assurance that their agreements could n't be easily undone . so here 's what they decided . for an amendment to even be proposed , it must receive a two-thirds vote of approval in both houses of congress , or a request from two-thirds of state legislatures to call a national convention , and that 's just the first step . to actually change the constitution , the amendment must be ratified by three-quarters of all states . to do this , each state can either have its legislature vote on the amendment , or it can hold a separate ratification convention with delegates elected by voters . the result of such high thresholds is that , today , the american constitution is quite static . most other democracies pass amendments every couple of years . the u.s. , on the other hand , has n't passed one since 1992 . at this point , you may wonder how any amendments managed to pass at all . the first ten , known as the bill of rights , includes some of america 's most well-known freedoms , such as the freedom of speech , and the right to a fair trial . these were passed all at once to resolve some conflicts from the original constitutional convention . years later , the thirteenth amendment , which abolished slavery , as well as the fourteenth and fifteenth amendments , only passed after a bloody civil war . ratifying amendments has also become harder as the country has grown larger and more diverse . the first ever proposed amendment , a formula to assign congressional representatives , was on the verge of ratification in the 1790s . however , as more and more states joined the union , the number needed to reach the three-quarter mark increased as well , leaving it unratified to this day . today , there are many suggested amendments , including outlawing the burning of the flag , limiting congressional terms , or even repealing the second amendment . while many enjoy strong support , their likelihood of passing is slim . americans today are the most politically polarized since the civil war , making it nearly impossible to reach a broad consensus . in fact , the late supreme court justice antonin scalia once calculated that due to america 's representative system of government , it could take as little as 2 % of the total population to block an amendment . of course , the simplest solution would be to make the constitution easier to amend by lowering the thresholds required for proposal and ratification . that , however , would require its own amendment . instead , historical progress has mainly come from the u.s. supreme court , which has expanded its interpretation of existing constitutional laws to keep up with the times . considering that supreme court justices are unelected and serve for life once appointed , this is far from the most democratic option . interestingly , the founders themselves may have foreseen this problem early on . in a letter to james madison , thomas jefferson wrote that laws should expire every 19 years rather than having to be changed or repealed since every political process is full of obstacles that distort the will of the people . although he believed that the basic principles of the constitution would endure , he stressed that the earth belongs to the living , and not to the dead .
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of course , the simplest solution would be to make the constitution easier to amend by lowering the thresholds required for proposal and ratification . that , however , would require its own amendment . instead , historical progress has mainly come from the u.s. supreme court , which has expanded its interpretation of existing constitutional laws to keep up with the times .
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as described in the constitution , there are _____ different ways to propose an amendment and _____ different ways to ratify an amendment
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have you ever had someone try to explain something to you a dozen times with no luck – but , then , when you see a picture , the idea finally clicks ? if that sounds familiar , maybe you might consider yourself a visual learner . or , if reading or listening does the trick , maybe you feel like you ’ re a verbal learner . we call these labels learning styles , but is there /really/ a way to categorize different types of students ? well , it actually seems like /multiple/ presentation formats , especially if one of them is visual , help most people learn . when psychologists and educators test for learning styles , they ’ re trying to figure out whether these are inherent traits that affect how well students learn , instead of just a preference . usually , they start by giving a survey to figure out what style a student favors , like visual or verbal learning . then , they try to teach the students something with a specific presentation style , like using visual aids , and do a follow-up test to see how much they learned . that way , the researchers can see if the self-identified verbal learners really learned better when the information was just spoken aloud , for example . but , according to a 2008 review , only /one/ study that followed this design found that students actually learned best with their preferred style… and it had some pretty big flaws . the researchers excluded two-thirds of the original participants because they did n't seem to have /any/ clear learning style from the survey at the beginning . plus , they removed outliers from the data if they thought they were “ extreme , ” without defining exactly what that meant . and , they did n't even report the actual test scores in the final paper . so ... it doesn ’ t really seem like learning styles are an inherent trait that we all have . but , that does n't mean that all students will do amazingly if they just spend all their time reading from a textbook . instead , /most people/ seem to learn better if they ’ re taught in several ways – especially if one is visual . in one study , researchers tested whether students remembered lists of words better if they heard them , saw them , or both . and everyone seemed to do better if they got to see the words in print , even the self-identified auditory learners . that preference did n't seem to matter . similar studies tested whether students learned basic physics and chemistry concepts better by reading plain text or viewing pictures , too . and everyone did better with the help of pictures . so the question of whether or not you 're a visual learner could best be answered with : `` well , yeah , kinda . but so are most people . '' thanks for asking , and thanks especially to all of our patrons on patreon who keep these answers coming . if you ’ d like to submit questions to be answered , or get some videos a few days early , go to patreon.com/scishow . and don ’ t forget to go to youtube.com/scishow and subscribe !
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when psychologists and educators test for learning styles , they ’ re trying to figure out whether these are inherent traits that affect how well students learn , instead of just a preference . usually , they start by giving a survey to figure out what style a student favors , like visual or verbal learning . then , they try to teach the students something with a specific presentation style , like using visual aids , and do a follow-up test to see how much they learned .
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according to the studies mentioned in the video , what learning aid ( verbal , auditory , visual , etc . ) generally has the biggest influence on students ' ability to retain information ?
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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 .
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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 .
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president _____ , a conservative , expected his nominee _______ to rule like a conservative .
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you might think you know a lot about native americans through popular movies , books , and classes in school , but it turns out that a lot of what we think we know about famous native american figures is n't quite right . take sacajawea for example . you probably remember her as a beautiful indian woman who lived an exotic life serving as the all-knowing guide for lewis and clark 's famous expedition , right ? well , that 's not exactly how it happened . not much is known about sacajawea 's early childhood , but we do know that she was born in 1788 into the agaidika tribe of the lemhi shoshone in what is now idaho . in 1800 , when she was about 12 years old , sacajawea and several other girls were kidnapped by a group of hidatsa indians . she was taken as a captive to a hidatsa village in present-day north dakota . then , she was sold to a french canadian fur trapper named toussaint charbonneau . within a year or so , she was pregnant with her first child . soon after she became pregnant , the corps of discovery arrived near the hidatsa villages . captains meriwether lewis and william clark built fort mandan there , and then started interviewing people to help guide them on their perilous expedition . they agreed to hire sacajawea 's husband , charbonneau , with the understanding that his lovely wife would also come along as an interpreter . they figured her very presence would help any encounters with native tribes along the way . as clark noted in his journal , `` a woman with a party of men is a token of peace . '' shortly thereafter , sacajawea gave birth to a little boy named jean baptiste charbonneau . clark called him pompy . she carried pompy on a board strapped to her back as the corps of discovery forged on . besides interpreting the language when lewis and clark encountered indians , sacajawea 's activities as a member of the corps included digging for roots , collecting edible plants , and picking berries . in 1805 , the boat they were riding in was capsized . she dove into the water , recovering all the important papers and supplies that would otherwise have been lost , including the journals and records of lewis and clark . later that year , captain lewis and three men scouted 75 miles ahead of the expedition 's main party , crossing the continental divide . the next day they encountered a group of shishones . not only did they prove to be sacajawea 's band , but their leader , chief cameahwait , turned out to be her very own brother . after five years of separation since her kidnapping as a young girl , sacajawea and cameahwait had an emotional reunion . unfortunately , she quickly had to bid farewell to her beloved brother and continue on with the journey . at one point , the expedition became so difficult and freezing , the group was reduced to eating candles to survive . when temperatures finally became more bearable , sacajawea found , dug , and cooked roots to help the group regain their strength . on the return trip , they encountered an indian wearing a beautiful fur robe . lewis and clark wanted to bring the robe to thomas jefferson as a gift but had nothing to trade for it . so , sacajawea agreed to trade her most precious possession , her beaded belt , for the fur . a little over two years after the expedition began , it was finally over , ending in st. louis . today , we learn about sacajawea in school as a heroic guide , but her life , like most everyone 's , was much more complicated than history books sometimes give her credit for .
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you might think you know a lot about native americans through popular movies , books , and classes in school , but it turns out that a lot of what we think we know about famous native american figures is n't quite right . take sacajawea for example . you probably remember her as a beautiful indian woman who lived an exotic life serving as the all-knowing guide for lewis and clark 's famous expedition , right ?
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sacajawea faced a great amount of hardship during her short life yet remained positive and hardworking . it is unlikely she even realized her tremendous significance in lewis and clark ’ s journey.where do you think sacajawea gleaned such motivation ? under similar circumstances , do you think you would remain cheerful and continue to work hard ? why or why not ?
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it may seem like the semicolon is struggling with an identity crisis . it looks like a comma crossed with a period . maybe that 's why we toss these punctuation marks around like grammatical confetti . we 're confused about how to use them properly . in fact , it 's the semicolon 's half-half status that makes it useful . it 's stronger than a comma , and less final than a period . it fills the spaces in between , and for that reason , it has some specific and important tasks . for one , it can clarify ideas in a sentence that 's already festooned with commas . `` semicolons : at first , they may seem frightening , then , they become enlightening , finally , you 'll find yourself falling for these delightful punctuation marks . '' even though the commas separate different parts of the sentence , it 's easy to lose track of what belongs where . but then the semicolon edges in to the rescue . in list-like sentences , it can exert more force than commas do , cutting sentences into compartments and grouping items that belong together . the semicolon breaks things up , but it also builds connections . another of its tasks is to link together independent clauses . these are sentences that can stand on their own , but when connected by semicolons , look and sound better because they 're related in some way . `` semicolons were once a great mystery to me . i had no idea where to put them . '' technically , there 's nothing wrong with that . these two sentences can stand alone . but imagine they appeared in a long list of other sentences , all of the same length , each separated by periods . things would get monotonous very fast . in that situation , semicolons bring fluidity and variation to writing by connecting related clauses . but as beneficial as they are , semicolons do n't belong just anywhere . there are two main rules that govern their use . firstly , unless they 're being used in lists , semicolons should only connect clauses that are related in some way . you would n't use one here , for instance : `` semicolons were once a great mystery to me ; i 'd really like a sandwich . '' periods work best here because these are two totally different ideas . a semicolon 's job is to reunite two independent clauses that will benefit from one another 's company because they refer to the same thing . secondly , you 'll almost never find a semicolon willingly stationed before coordinating conjunctions : the words , `` and , '' `` but , '' `` for , '' `` nor , '' `` or , '' `` so , '' and `` yet . '' that 's a comma 's place , in fact . but a semicolon can replace a conjunction to shorten a sentence or to give it some variety . ultimately , this underappreciated punctuation mark can give writing clarity , force , and style , all encompassed in one tiny dot and squiggle that 's just waiting to be put in the right place .
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periods work best here because these are two totally different ideas . a semicolon 's job is to reunite two independent clauses that will benefit from one another 's company because they refer to the same thing . secondly , you 'll almost never find a semicolon willingly stationed before coordinating conjunctions : the words , `` and , '' `` but , '' `` for , '' `` nor , '' `` or , '' `` so , '' and `` yet . ''
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another of the semicolon 's grammatical functions is to :
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translator : andrea mcdonough reviewer : jessica ruby we are constantly asked for our opinions . which team do you think will win the super bowl ? who wore it better on the red carpet ? who are you going to vote for for mayor ? public opinion polls are everywhere . important decision makers in american government have long relied on public opinion polls throughout elections and important legislation . the problem is public opinion is n't easy to track and , often times , is n't even right . in 1948 , the < i > chicago daily tribune < /i > ran a now famous headline : `` dewey defeats truman , '' they cried in big , bold , black and white letters . the problem is that dewey had n't defeated truman . the < i > tribune < /i > had relied on polls to come to their conclusion . whoops ! this happens all the time because public opinion polls are either inaccurate or misleading . so , why are they wrong ? and why do we keep using them ? first , let 's start with an important term : sample . a sample is the group of people that respond to questions during a public opinion poll . a poll 's quality rests largely on its sample , and a sample can be bad in a few key ways . it can be too small , too narrow , or the poll itself can be too difficult . polls that are too small are bad for obvious reasons . and while you ca n't possibly ask every single person in america for their opinion , the more people you ask , the more accurate your prediction . polls that are too narrow , that only ask a certain type of person a question , are bad , too . consider a poll about whether or not the potato is the best vegetable in america . if you only asked people in idaho , where the state food is the potato , chances are that you would get a much different answer than if you asked people in the state of new mexico , where the state vegetable is beans . getting the right kind of diversity in your sample means making sure that your sample has a range of ages , races , genders , and geographic regions , just to name a few . finally , polls that are too hard ca n't tell you much either . if you 're asking people for their opinions on things about which they have no prior knowledge , the results will be pointless . you 're better off shaking a magic 8 ball . it 's not just the people you 're asking that can cause bias , though . the person doing the asking is part of the problem , too . that 's called interviewer bias . interviewer bias is all about the effect that the person asking the questions has on the sample . humans generally do n't like confrontation . people worry that their answers may make them look bad . therefore , we find that people tend to give socially desirable responses , not necessarily their honest opinions , because they do n't want to come across as heartless , racist , or bigoted . and the way we word our questions matters too . when polls purposely sway the answers one way or the other , it 's called a push poll because it pushes people to answer a certain way . `` would you vote for candidate smith ? '' is a perfectly normal question . `` would you vote for candidate smith if you knew that he robs senior citizens ? '' is a push poll . so , if polls are open to all sorts of manipulation and inaccuracies , why are they still so prevalent ? despite their flaws , public opinion polls provide us with some sense of the thoughts and moods of large groups of people . they offer politicians the chance to pass legislation they think a majority of americans will support . they help fashionistas on tv know which star wore the dress better on the red carpet . finally , they make us , the people who get polled , feel as though our voice has been heard . so , next time you get a phone call asking your opinion , or if you see a poll online , take some time to think about who is asking and why they 're asking . then , take that poll , and its results , with a grain of salt or a potato .
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the person doing the asking is part of the problem , too . that 's called interviewer bias . interviewer bias is all about the effect that the person asking the questions has on the sample .
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an interviewer , the person asking the questions , might influence the respondents ’ answers without even meaning to ! for instance , the gender of the interviewer could play a role in how people may choose to answer . what are some other characteristics of an interviewer that might affect a poll ’ s answers ?
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few individuals have influenced the world and many of today 's thinkers like plato . one 20th century philosopher even went so far as to describe all of western philosophy as a series of footnotes to plato . he created the first western university and was teacher to ancient greece 's greatest minds , including aristotle . but even one of the founders of philosophy was n't perfect . along with his great ideas , plato had a few that have n't exactly stood the test of time . so here are brief rundowns of a few of his best and worst ideas . plato argued that beyond our imperfect world was a perfect unchanging world of forms . forms are the ideal versions of the things and concepts we see around us . they serve as a sort of instruction manual to our own world . floating around the world of forms is the ideal tree , and the ideal youtube channel , and even the ideal justice , or ideal love . our own reality is comprised of imperfect copies of ideal forms . plato argued that philosophers should strive to contemplate and understand these perfect forms so that they may better navigate our misleading reality . while it may seem silly , the disconnect between the world as it appears and the greater truth behind it is one of philosophy 's most vexing problems . it 's been the subject of thousands of pages by theologians , philosophers , and screenwriters alike . it raises questions like should we trust our senses to come to the truth or our own reason ? for plato , the answer is reason . it alone provides us with at least the potential to contemplate the forms . but reason did n't always pan out for plato himself . when he sought to situate humankind amongst the animals , he lumped us in with birds . `` featherless bipeds '' was his official designation . diogenes the cynic , annoyed by this definition , stormed into plato 's class with a plucked chicken , announcing , `` behold . plato 's man . '' but back to a few good ideas . plato is one of the earliest political theorists on record , and with aristotle , is seen as one of the founders of political science . he reasoned that being a ruler was no different than any other craft , whether a potter or doctor , and that only those who had mastered the craft were fit to lead . ruling was the craft of contemplating the forms . in his republic , plato imagined a utopia where justice is the ultimate goal . plato 's ideal city seeks a harmonious balance between its individual parts and should be lead by a philosopher king . millennia before his time , plato also reasoned that women were equally able to rule in this model city . unfortunately , plato was inconsistent with women , elsewhere likening them to children . he also believed that a woman 's womb was a live animal that could wander around in her body and cause illness . this bad idea , also espoused by other contemporaries of plato , was sadly influential for hundreds of years in european medicine . furthermore , he thought that society should be divided into three groups : producers , the military , and the rulers , and that a great noble lie should convince everyone to follow this structure . the noble lie he proposed was that we 're all born with gold , silver , or a mixture of brass and iron in our souls , which determine our roles in life . some thinkers have gone on to credit the idea of the noble lie as a prototype for 20th century propaganda , and the philosopher king as inspiration for the dictators that used them . should a few bad ideas tarnish plato 's status as one of the greatest philosophers in history ? no ! plato gave the leaders and thinkers who came after him a place to start . through the centuries , we 've had the chance to test those ideas through writing and experience , and have accepted some while rejecting others . we are continuing to refine , amend , and edit his ideas which have become foundations of the modern world .
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diogenes the cynic , annoyed by this definition , stormed into plato 's class with a plucked chicken , announcing , `` behold . plato 's man . '' but back to a few good ideas .
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why does plato think there are forms ?
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have you ever tried to picture an ideal world ? one without war , poverty , or crime ? if so , you 're not alone . plato imagined an enlightened republic ruled by philosopher kings , many religions promise bliss in the afterlife , and throughout history , various groups have tried to build paradise on earth . thomas more 's 1516 book `` utopia '' gave this concept a name , greek for `` no place . '' though the name suggested impossibility , modern scientific and political progress raised hopes of these dreams finally becoming reality . but time and time again , they instead turned into nightmares of war , famine , and oppression . and as artists began to question utopian thinking , the genre of dystopia , the not good place , was born . one of the earliest dystopian works is jonathan swift 's `` gulliver 's travels . '' throughout his journey , gulliver encounters fictional societies , some of which at first seem impressive , but turn out to be seriously flawed . on the flying island of laputa , scientists and social planners pursue extravagant and useless schemes while neglecting the practical needs of the people below . and the houyhnhnm who live in perfectly logical harmony have no tolerance for the imperfections of actual human beings . with his novel , swift established a blueprint for dystopia , imagining a world where certain trends in contemporary society are taken to extremes , exposing their underlying flaws . and the next few centuries would provide plenty of material . industrial technology that promised to free laborers imprisoned them in slums and factories , instead , while tycoons grew richer than kings . by the late 1800 's , many feared where such conditions might lead . h. g. wells 's `` the time machine '' imagined upper classes and workers evolving into separate species , while jack london 's `` the iron heel '' portrayed a tyrannical oligarchy ruling over impoverished masses . the new century brought more exciting and terrifying changes . medical advances made it possible to transcend biological limits while mass media allowed instant communication between leaders and the public . in aldous huxley 's `` brave new world '' , citizens are genetically engineered and conditioned to perform their social roles . while propaganda and drugs keep the society happy , it 's clear some crucial human element is lost . but the best known dystopias were not imaginary at all . as europe suffered unprecedented industrial warfare , new political movements took power . some promised to erase all social distinctions , while others sought to unite people around a mythical heritage . the results were real-world dystopias where life passed under the watchful eye of the state and death came with ruthless efficiency to any who did n't belong . many writers of the time did n't just observe these horrors , but lived through them . in his novel `` we '' , soviet writer yevgeny zamyatin described a future where free will and individuality were eliminated . banned in the u.s.s.r. , the book inspired authors like george orwell who fought on the front lines against both fascism and communism . while his novel `` animal farm '' directly mocked the soviet regime , the classic `` 1984 '' was a broader critique of totalitarianism , media , and language . and in the u.s.a. , sinclair lewis 's `` it ca n't happen here '' envisioned how easily democracy gave way to fascism . in the decades after world war ii , writers wondered what new technologies like atomic energy , artificial intelligence , and space travel meant for humanity 's future . contrasting with popular visions of shining progress , dystopian science fiction expanded to films , comics , and games . robots turned against their creators while tv screens broadcast deadly mass entertainment . workers toiled in space colonies above an earth of depleted resources and overpopulated , crime-plagued cities . yet politics was never far away . works like `` dr. strangelove '' and `` watchmen '' explored the real threat of nuclear war , while `` v for vendetta '' and `` the handmaid 's tale '' warned how easily our rights could disappear in a crisis . and today 's dystopian fiction continues to reflect modern anxieties about inequality , climate change , government power , and global epidemics . so why bother with all this pessimism ? because at their heart , dystopias are cautionary tales , not about some particular government or technology , but the very idea that humanity can be molded into an ideal shape . think back to the perfect world you imagined . did you also imagine what it would take to achieve ? how would you make people cooperate ? and how would you make sure it lasted ? now take another look . does that world still seem perfect ?
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in the decades after world war ii , writers wondered what new technologies like atomic energy , artificial intelligence , and space travel meant for humanity 's future . contrasting with popular visions of shining progress , dystopian science fiction expanded to films , comics , and games . robots turned against their creators while tv screens broadcast deadly mass entertainment .
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what is the relationship between science fiction and dystopia ?
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sharks have been celebrated as powerful gods by some native cultures . for example , fijians believe the shark god dakuwaqa , could protect fisherman from the dangers at sea . and today , sharks are recognized as apex predators of the world 's ocean and include some of the earth 's longest living vertebrates . what is it that makes these fish worthy of our ancient legends and so successful in the seas ? much of their hunting prowess stems from a unique set of biological traits honed for more than 400 million years . their cartilaginous skeletons are less dense than bony ones and require less energy to move . large oily livers lend buoyancy to their streamlined bodies , and while trunk muscles of bony fishes attach directly to their skeletons , those of sharks also join to their skin . this special design transforms them into pressurized tubes whose springy skin can efficiently transmit muscular forces to the tail . shark skin has additional remarkable features . despite its smooth external appearance , at the micro level , it has a coarse texture thanks to thousands of tiny teeth-like scales called dermal denticles . each denticle is coated in a substance called enameloid , which turns the skin into a tough shield . plus the structure of denticles varies across the body in such a way as to reduce noise and drag when the shark moves through water . as for the teeth in their mouths , sharks can produce up to 50,000 in a lifetime . on average , they can lose one tooth a week , and each time that happens , it 's rapidly replaced . thanks to a layer of fluoride coating their teeth , sharks also avoid cavities . but teeth are n't the same in all sharks . they can vary across species and by diet . some are dense and flattened , useful for crushing mollusks . others are needle-like for gripping fish . the mouths of great whites contain pointy lower teeth for holding prey and triangular serrated upper teeth for slicing . this variety enables sharks to target prey in a diversity of ocean environments . many species also have another peculiar trait - the ability to launch their jaws out of their mouths , open them extra wide , and grab prey by surprise . over the course of evolution , shark brains have expanded , coupled with the growth of their sensory organs . modern-day sharks can smell a few drops of blood and hear sounds underwater from 800 meters away . they 're particularly well-tuned to low frequencies , including those emitted by dying fish . and like cats , they have reflective membranes called tapeta lucida at the backs of their eyes that dramatically improve their vision in low light . as if these heightened abilities were n't enough , sharks have even honed a sixth sense . they 're able to hunt using a network of electrosensory cells called ampullae of lorenzini . these cells are filled with hypersensitive jelly which allows them to detect electrical signals from prey , including the slightest twitch of a muscle . some of the most iconic shark species , like great whites , makos , porbeagles , and salmon sharks owe their success to another surprising trait : warm blood inside a cold-blooded creature . inside their bodies , they have bundles of arteries and veins called rete mirabile . here , venous blood warmed up by the shark 's working muscles passes right next to arteries carrying cold , oxygen-rich blood from the gills . this arrangement transfers heat to the blood that gets cycled back to the body 's vital organs . warmer muscles enable faster , more powerful swimming , while warmer bellies aid digestion , and the more rapid development of young in utero . and warmer eyes and brains keep the sharks alert in cold waters . with these amazing adaptations , there 's more to revere than fear from the 500 shark species roaming our oceans . unfortunately , one-third of these species are threatened due to overfishing . after millions of years in the making , these apex predators may be meeting their greatest challenge yet .
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and warmer eyes and brains keep the sharks alert in cold waters . with these amazing adaptations , there 's more to revere than fear from the 500 shark species roaming our oceans . unfortunately , one-third of these species are threatened due to overfishing .
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how many shark species are in existence today ?
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if you think of culture as an iceberg , only a small fraction of it is visible . food , flags , and festivals , which are often talked about in schools , are the visible parts that we rightly celebrate . however , only when we look deeper , under the water , are we able to focus on the common values that connect us . in what seems to be an increasingly troubled world , where social and political systems are being stretched , conflict within and between countries is at times heightened , while human rights are being ignored , this desire for peace grows ever stronger . sometimes we see this common value emerging above the surface and becoming visible . for example , it is part of everyday language used when people greet one another and welcome the new day . in many parts of the arab world and parts of south asia , such as bangladesh for example , the greeting of `` as-salamu alaykum '' can be translated to `` peace be with you . '' the same is true as you walk through markets or into schools each morning in india , or nepal , or bhutan , where greetings of `` namaste , '' which has not only a strong message of peace - `` the spirit in me greets the spirit in you '' - but also its physical gesture , the palms brought together slowly at the heart , to honor a special place in each of us . in myanmar , greetings of `` mingalarbar '' are met by bowing monks as they internalize a message where others add blessing to enhance the auspiciousness of the moment , or by giggling children as they scurry off to school . after many hours of hiking through the mountains of lesotho , surrounded by the tranquility and rugged terrain , you are likely to meet a herdboy who has slept the night in a vacant rondoval and bellows out greetings of `` lumela '' or `` khotso '' , which means `` peace be with you . '' if you took a moment to research further the meanings behind `` shalom , '' or the korean greeting , you would find that they too have deeply-seated connections to peace . however , they have become quick comments made to welcome , greet , and say hello , and in this overuse , have likely lost the focus that was originally intended when put into practice hundreds or thousands of years ago . in highlighting this simple evidence of ingrained behavior , we can create the necessary shift in thinking needed to incorporate flexibility and open-mindedness in us all when looking at the globalization of the world .
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in myanmar , greetings of `` mingalarbar '' are met by bowing monks as they internalize a message where others add blessing to enhance the auspiciousness of the moment , or by giggling children as they scurry off to school . after many hours of hiking through the mountains of lesotho , surrounded by the tranquility and rugged terrain , you are likely to meet a herdboy who has slept the night in a vacant rondoval and bellows out greetings of `` lumela '' or `` khotso '' , which means `` peace be with you . '' if you took a moment to research further the meanings behind `` shalom , '' or the korean greeting , you would find that they too have deeply-seated connections to peace .
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in the rondavels of lesotho , you may hear heard boys shouting greetings that literally translate to :
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each year in the united states , players of sports and recreational activities receive between 2.5 and 4 million concussions . how dangerous are all those concussions ? the answer is complicated , and lies in how the brain responds when something strikes it . the brain is made of soft fatty tissue , with a consistency something like jello . inside its protective membranes and the skull 's hard casing , this delicate organ is usually well-shielded . but a sudden jolt can make the brain shift and bump against the skull 's hard interior , and unlike jello , the brain 's tissue is n't uniform . it 's made of a vast network of 90 billion neurons , which relay signals through their long axons to communicate throughout the brain and control our bodies . this spindly structure makes them very fragile so that when impacted , neurons will stretch and even tear . that not only disrupts their ability to communicate but as destroyed axons begin to degenerate , they also release toxins causing the death of other neurons , too . this combination of events causes a concussion . the damage can manifest in many different ways including blackout , headache , blurry vision , balance problems , altered mood and behavior , problems with memory , thinking , and sleeping , and the onset of anxiety and depression . every brain is different , which explains why people 's experiences of concussions vary so widely . luckily , the majority of concussions fully heal and symptoms disappear within a matter of days or weeks . lots of rest and a gradual return to activity allows the brain to heal itself . on the subject of rest , many people have heard that you 're not supposed to sleep shortly after receiving a concussion because you might slip into a coma . that 's a myth . so long as doctors are n't concerned there may also be a more severe brain injury , like a brain bleed , there 's no documented problem with going to sleep after a concussion . sometimes , victims of concussion can experience something called post-concussion syndrome , or pcs . people with pcs may experience constant headaches , learning difficulties , and behavioral symptoms that even affect their personal relationships for months or years after the injury . trying to play through a concussion , even for only a few minutes , or returning to sports too soon after a concussion , makes it more likely to develop pcs . in some cases , a concussion can be hard to diagnose because the symptoms unfold slowly over time . that 's often true of subconcussive impacts which result from lower impact jolts to the head than those that cause concussions . this category of injury does n't cause noticable symptoms right away , but can lead to severe degenerative brain diseases over time if it happens repeatedly . take soccer players , who are known for repeatedly heading soccer balls . using a technique called diffusion tensor imaging , we 're beginning to find out what effect that has on the brain . this method allows scientists to find large axon bundles and see how milder blows might alter them structurally . in 2013 , researchers using this technique discovered that athletes who had headed the ball most , about 1,800 times a year , had damaged the structural integrity of their axon bundles . the damage was similar to how a rope will fail when the individual fibers start to fray . those players also performed worse on short-term memory tests , so even though no one suffered full-blown concussions , these subconcussive hits added up to measurable damage over time . in fact , researchers know that an overload of subconcussive hits is linked to a degenerative brain disease known as chronic traumatic encephalopathy , or cte . people with cte suffer from changes in their mood and behavior that begin appearing in their 30s or 40s followed by problems with thinking and memory that can , in some cases , even result in dementia . the culprit is a protein called tau . usually , tau proteins support tiny tubes inside our axons called microtubules . it 's thought that repeated subconcussive hits damage the microtubules , causing the tau proteins to dislodge and clump together . the clumps disrupt transport and communication along the neuron and drive the breakdown of connections within the brain . once the tau proteins start clumping together , they cause more clumps to form and continue to spread throughout the brain , even after head impacts have stopped . the data show that at least among football players , between 50 and 80 % of concussions go unreported and untreated . sometimes that 's because it 's hard to tell a concussion has occurred in the first place . but it 's also often due to pressure or a desire to keep going despite the fact that something 's wrong . this does n't just undermine recovery . it 's also dangerous . our brains are n't invincible . they still need us to shield them from harm and help them undo damage once it 's been done .
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so long as doctors are n't concerned there may also be a more severe brain injury , like a brain bleed , there 's no documented problem with going to sleep after a concussion . sometimes , victims of concussion can experience something called post-concussion syndrome , or pcs . people with pcs may experience constant headaches , learning difficulties , and behavioral symptoms that even affect their personal relationships for months or years after the injury .
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what are some symptoms of pcs ( post-concussion syndrome ) and what makes it more likely to develop it ?
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as the story goes , the legendary marksman william tell was forced into a cruel challenge by a corrupt lord . william 's son was to be executed unless william could shoot an apple off his head . william succeeded , but let 's imagine two variations on the tale . in the first variation , the lord hires a bandit to steal william 's trusty crossbow , so he is forced to borrow an inferior one from a peasant . however , the borrowed crossbow is n't adjusted perfectly , and william finds that his practice shots cluster in a tight spread beneath the bullseye . fortunately , he has time to correct for it before it 's too late . variation two : william begins to doubt his skills in the long hours before the challenge and his hand develops a tremor . his practice shots still cluster around the apple but in a random pattern . occasionally , he hits the apple , but with the wobble , there is no guarantee of a bullseye . he must settle his nervous hand and restore the certainty in his aim to save his son . at the heart of these variations are two terms often used interchangeably : accuracy and precision . the distinction between the two is actually critical for many scientific endeavours . accuracy involves how close you come to the correct result . your accuracy improves with tools that are calibrated correctly and that you 're well-trained on . precision , on the other hand , is how consistently you can get that result using the same method . your precision improves with more finely incremented tools that require less estimation . the story of the stolen crossbow was one of precision without accuracy . william got the same wrong result each time he fired . the variation with the shaky hand was one of accuracy without precision . william 's bolts clustered around the correct result , but without certainty of a bullseye for any given shot . you can probably get away with low accuracy or low precision in everyday tasks . but engineers and researchers often require accuracy on microscopic levels with a high certainty of being right every time . factories and labs increase precision through better equipment and more detailed procedures . these improvements can be expensive , so managers must decide what the acceptable uncertainty for each project is . however , investments in precision can take us beyond what was previously possible , even as far as mars . it may surprise you that nasa does not know exactly where their probes are going to touch down on another planet . predicting where they will land requires extensive calculations fed by measurements that do n't always have a precise answer . how does the martian atmosphere 's density change at different elevations ? what angle will the probe hit the atmosphere at ? what will be the speed of the probe upon entry ? computer simulators run thousands of different landing scenarios , mixing and matching values for all of the variables . weighing all the possibilities , the computer spits out the potential area of impact in the form of a landing ellipse . in 1976 , the landing ellipse for the mars viking lander was 62 x 174 miles , nearly the area of new jersey . with such a limitation , nasa had to ignore many interesting but risky landing areas . since then , new information about the martian atmosphere , improved spacecraft technology , and more powerful computer simulations have drastically reduced uncertainty . in 2012 , the landing ellipse for the curiosity lander was only 4 miles wide by 12 miles long , an area more than 200 times smaller than viking 's . this allowed nasa to target a specific spot in gale crater , a previously un-landable area of high scientific interest . while we ultimately strive for accuracy , precision reflects our certainty of reliably achieving it . with these two principles in mind , we can shoot for the stars and be confident of hitting them every time .
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precision , on the other hand , is how consistently you can get that result using the same method . your precision improves with more finely incremented tools that require less estimation . the story of the stolen crossbow was one of precision without accuracy . william got the same wrong result each time he fired .
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questions of precision can arise not just from direct measurements , but also when we make decisions about what values are appropriate to plug into calculations . provide an example of this from the mars curiosity lander story .
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each spring , nature lovers eagerly greet the signs that winter is finally coming to an end . as the days grow warmer , the flowers and trees start to bloom , and the world comes alive with the melodious call of birds in search of a new mate . but where have these enchanting sounds been hiding all winter ? for almost 200 species of song birds , their winters have been spent down in the tropical climates of central and south america . while this may sound ideal , it involves one of the most perilous journeys known in the entire animal kingdom . this journey is called migration , and for song birds , this can involve travelling somewhere between a few hundred to almost 7,000 miles in a period of several weeks to four months . birds spend weeks preparing for the intense journey by gorging on large quantities of food , sometimes doubling their weight prior to departure . while flying , birds can lose almost one percent of their body weight an hour , so packing on the pounds is crucial to their survival . however , more than the physical stress , migrating birds are now facing a new source of hardship : landscape change . just imagine you 're the one getting ready to take a trip . you 've packed the car with everything you think you need , fueled up the tank , eaten a huge breakfast , and hit the road . you 've taken this journey before . you know all your favorite rest stops and little back-alley diners to grab a bite . everything is planned out . but just as your fuel gauge starts dipping into the red zone , you pass by what should have been a gas station , except it 's closed . `` not a problem , '' you think , `` the next one ca n't be too far away . '' but then that next station never appears . unfortunately , as you continue on your route , the reality of the situation starts to set in . more and more stations are closed or just erased from your map . all of a sudden , your routine trip has become a desperate search just to find somewhere safe to rest and refuel for the night . this scenario has become the reality for the majority of migrating song birds as human land development continues unchecked . humans are altering important stop-over sites that birds have been using for generations . as migrators pass over the continent , they run a gauntlet of dangers , including pesticide ingestion in rural farmlands , habitat loss in suburban developments , as well as disorientation from light pollution , and even structure collision with tall , reflective glass buildings in cities . of the estimated 20 billion individual birds that comprise the fall population , only about half will return to breed the following spring . almost one billion of these deaths are attributed just to building collisions . with such astounding yearly losses , humans risk more than just the loss of the beautiful colors and songs of birds , they also play an important role in the ecosystem . birds help with insect control , pollination , and disbursing seeds throughout the landscape . without birds , the natural world would be a very different place . although birds face an on-going threat from human land development , there are actions that we can all take to help . many countries and local governements have already passed important laws that restrict the use of poisonous pesticides . by using more natural , plant-based products , we can maintain our farms and gardens without the dangerous side effects . in addition , as our global populations continue to grow and people need places to call home , green spaces can offer both bird habitat as well as a peaceful and natural place for us to enjoy . small changes at home can also make a huge difference . by hanging up feeders and building bird houses in outdoor areas , we can provide much-needed food and safety during long migrations . turning out lights in suburban and urban environments can also help birds that look for stars to navigate . with our help , these sky travellers can reach their destination safely , and hopefully keep returning year after year .
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as migrators pass over the continent , they run a gauntlet of dangers , including pesticide ingestion in rural farmlands , habitat loss in suburban developments , as well as disorientation from light pollution , and even structure collision with tall , reflective glass buildings in cities . of the estimated 20 billion individual birds that comprise the fall population , only about half will return to breed the following spring . almost one billion of these deaths are attributed just to building collisions .
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what proportion of birds that migrate in the fall return to breed the following spring ?
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grammatical tense is how languages talk about time without explicitly naming time periods by , instead , modifying verbs to specify when action occurs . so how many different tenses are there in a language like english ? at first , the answer seems obvious : there 's past , present , and future . but thanks to something called grammatical aspect , each of those time periods actually divides further . there are four kinds of aspect . in the continuous or progressive aspect , the actions are still happening at the time of reference . the perfect aspect describes actions that are finished . the perfect progressive aspect is a combination , describing a completed part of a continuous action . and finally , there 's the simple aspect , the basic form of the past , present , and future tense where an action is not specified as continuous or discreet . that 's all a little hard to follow , so let 's see how it works in action . let 's say your friends tell you they went on a secret naval mission to collect evidence of a mysterious sea creature . the tense sets the overall frame of reference in the past , but within that , there are many options . your friends might say a creature attacked their boat , that 's the past simple , the most general aspect , which gives no further clarification . they were sleeping when it happened , a continuous process underway at that point . they might also tell you they had departed from nantucket to describe an action completed even earlier . that 's an example of the past perfect . or that they had been sailing for three weeks , something that was ongoing up until that point . in the present , they tell you that they still search for the creature today , their present simple activity . perhaps they are preparing for their next mission continuously as they speak . and they have built a special submarine for it , a completed achievement . plus , if they have been researching possible sightings of the creature , it 's something they 've been doing for a while and are still doing now making it present perfect progressive . so what does this next mission hold ? you know it still has n't happened because they will depart next week , the future simple . your friends will be searching for the elusive creature , an extended continuous undertaking . they tell you the submarine will have reached uncharted depths a month from now . that 's a confident prediction about what will be achieved by a specific point in the future , a point at which they will have been voyaging for three weeks in the future perfect progressive . the key insight to all these different tenses is that each sentence takes place in a specific moment , whether it 's past , present , or future . the point of aspects is that they tell you as of that moment the status of the action . in total , they give us twelve possibilities in english . what about other languages ? some , like french , swahili , and russian take a similar approach to english . others describe and divide time differently . some have fewer grammatical tenses , like japanese , which only distinguishes past from non-past , buli and tukang basi , which only distinguish future from non-future , and mandarin chinese with no verb tenses at all , only aspect . on the other hand , languages like yagwa split past tense into multiple degrees , like whether something happened hours , weeks , or years ago . in others , tenses are intertwined with moods that can convey urgency , necessity , or probability of events . this makes translation difficult but not impossible . speakers of most languages without certain tenses can express the same ideas with auxiliary words , like would or did , or by specifying the time they mean . are the variations from language to language just differents ways of describing the same fundamental reality ? or do their diverse structures reflect different ways of thinking about the world and even time itself ? and if so , what other ways of conceiving time may be out there ?
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but thanks to something called grammatical aspect , each of those time periods actually divides further . there are four kinds of aspect . in the continuous or progressive aspect , the actions are still happening at the time of reference . the perfect aspect describes actions that are finished . the perfect progressive aspect is a combination , describing a completed part of a continuous action . and finally , there 's the simple aspect , the basic form of the past , present , and future tense where an action is not specified as continuous or discreet .
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continuous ( progressive ) aspect in english is mostly used to describe actions that :
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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 .
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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 .
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the video ends with the statement “ sometimes coincidences aren ’ t as coincidental as they seem. ” explain .
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what is consciousness ? can an artificial machine really think ? does the mind just consist of neurons in the brain , or is there some intangible spark at its core ? for many , these have been vital considerations for the future of artificial intelligence . but british computer scientist alan turing decided to disregard all these questions in favor of a much simpler one : can a computer talk like a human ? this question led to an idea for measuring aritificial intelligence that would famously come to be known as the turing test . in the 1950 paper , `` computing machinery and intelligence , '' turing proposed the following game . a human judge has a text conversation with unseen players and evaluates their responses . to pass the test , a computer must be able to replace one of the players without substantially changing the results . in other words , a computer would be considered intelligent if its conversation could n't be easily distinguished from a human 's . turing predicted that by the year 2000 , machines with 100 megabytes of memory would be able to easily pass his test . but he may have jumped the gun . even though today 's computers have far more memory than that , few have succeeded , and those that have done well focused more on finding clever ways to fool judges than using overwhelming computing power . though it was never subjected to a real test , the first program with some claim to success was called eliza . with only a fairly short and simple script , it managed to mislead many people by mimicking a psychologist , encouraging them to talk more and reflecting their own questions back at them . another early script parry took the opposite approach by imitating a paranoid schizophrenic who kept steering the conversation back to his own preprogrammed obsessions . their success in fooling people highlighted one weakness of the test . humans regularly attribute intelligence to a whole range of things that are not actually intelligent . nonetheless , annual competitions like the loebner prize , have made the test more formal with judges knowing ahead of time that some of their conversation partners are machines . but while the quality has improved , many chatbot programmers have used similar strategies to eliza and parry . 1997 's winner catherine could carry on amazingly focused and intelligent conversation , but mostly if the judge wanted to talk about bill clinton . and the more recent winner eugene goostman was given the persona of a 13-year-old ukrainian boy , so judges interpreted its nonsequiturs and awkward grammar as language and culture barriers . meanwhile , other programs like cleverbot have taken a different approach by statistically analyzing huge databases of real conversations to determine the best responses . some also store memories of previous conversations in order to improve over time . but while cleverbot 's individual responses can sound incredibly human , its lack of a consistent personality and inability to deal with brand new topics are a dead giveaway . who in turing 's day could have predicted that today 's computers would be able to pilot spacecraft , perform delicate surgeries , and solve massive equations , but still struggle with the most basic small talk ? human language turns out to be an amazingly complex phenomenon that ca n't be captured by even the largest dictionary . chatbots can be baffled by simple pauses , like `` umm ... '' or questions with no correct answer . and a simple conversational sentence , like , `` i took the juice out of the fridge and gave it to him , but forgot to check the date , '' requires a wealth of underlying knowledge and intuition to parse . it turns out that simulating a human conversation takes more than just increasing memory and processing power , and as we get closer to turing 's goal , we may have to deal with all those big questions about consciousness after all .
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in other words , a computer would be considered intelligent if its conversation could n't be easily distinguished from a human 's . turing predicted that by the year 2000 , machines with 100 megabytes of memory would be able to easily pass his test . but he may have jumped the gun .
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what were turing ’ s predictions for how computers would do on the test ?
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