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cramming for a test ? trying to get more done than you have time to do ? stress is a feeling we all experience when we are challenged or overwhelmed . but more than just an emotion , stress is a hardwired physical response that travels throughout your entire body . in the short term , stress can be advantageous , but when activated too often or too long , your primitive fight or flight stress response not only changes your brain but also damages many of the other organs and cells throughout your body . your adrenal gland releases the stress hormones cortisol , epinephrine , also known as adrenaline , and norepinephrine . as these hormones travel through your blood stream , they easily reach your blood vessels and heart . adrenaline causes your heart to beat faster and raises your blood pressure , over time causing hypertension . cortisol can also cause the endothelium , or inner lining of blood vessels , to not function normally . scientists now know that this is an early step in triggering the process of atherosclerosis or cholesterol plaque build up in your arteries . together , these changes increase your chances of a heart attack or stroke . when your brain senses stress , it activates your autonomic nervous system . through this network of nerve connections , your big brain communicates stress to your enteric , or intestinal nervous system . besides causing butterflies in your stomach , this brain-gut connection can disturb the natural rhythmic contractions that move food through your gut , leading to irritable bowel syndrome , and can increase your gut sensitivity to acid , making you more likely to feel heartburn . via the gut 's nervous system , stress can also change the composition and function of your gut bacteria , which may affect your digestive and overall health . speaking of digestion , does chronic stress affect your waistline ? well , yes . cortisol can increase your appetite . it tells your body to replenish your energy stores with energy dense foods and carbs , causing you to crave comfort foods . high levels of cortisol can also cause you to put on those extra calories as visceral or deep belly fat . this type of fat does n't just make it harder to button your pants . it is an organ that actively releases hormones and immune system chemicals called cytokines that can increase your risk of developing chronic diseases , such as heart disease and insulin resistance . meanwhile , stress hormones affect immune cells in a variety of ways . initially , they help prepare to fight invaders and heal after injury , but chronic stress can dampen function of some immune cells , make you more susceptible to infections , and slow the rate you heal . want to live a long life ? you may have to curb your chronic stress . that 's because it has even been associated with shortened telomeres , the shoelace tip ends of chromosomes that measure a cell 's age . telomeres cap chromosomes to allow dna to get copied every time a cell divides without damaging the cell 's genetic code , and they shorten with each cell division . when telomeres become too short , a cell can no longer divide and it dies . as if all that were n't enough , chronic stress has even more ways it can sabotage your health , including acne , hair loss , sexual dysfunction , headaches , muscle tension , difficulty concentrating , fatigue , and irritability . so , what does all this mean for you ? your life will always be filled with stressful situations . but what matters to your brain and entire body is how you respond to that stress . if you can view those situations as challenges you can control and master , rather than as threats that are insurmountable , you will perform better in the short run and stay healthy in the long run .
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together , these changes increase your chances of a heart attack or stroke . when your brain senses stress , it activates your autonomic nervous system . through this network of nerve connections , your big brain communicates stress to your enteric , or intestinal nervous system . besides causing butterflies in your stomach , this brain-gut connection can disturb the natural rhythmic contractions that move food through your gut , leading to irritable bowel syndrome , and can increase your gut sensitivity to acid , making you more likely to feel heartburn .
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through the enteric nervous system , stress causes :
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why does salt dissolve in water but oil does n't ? well , in a word , chemistry , but that 's not very satisfying , is it ? well , the reason salt dissolves and oil does not comes down to the two big reasons why anything happens at all : energetics and entropy . energetics deals primarily with the attractive forces between things . when we look at oil or salt in water , we focus on the forces between particles on a very , very , very small scale , the molecular level . to give you a sense of this scale , in one glass of water , there are more molecules than known stars in the universe . now , all of these molecules are in constant motion , moving , vibrating , and rotating . what prevents almost all of those molecules from just flying out of the glass are the attractive interactions between molecules . the strength of the interactions between water , itself , and other substances is what we mean when we say energetics . you can think of the water molecules engaging in a constant dance , sort of like a square dance where they constantly and randomly exchange partners . put simply , the ability for substances to interact with water , balanced with how they disrupt how water interacts with itself , plays an important role in explaining why certain things mix well into water and others do n't . entropy basically describes the way things and energy can be arranged based on random motion . for example , think of the air in a room . imagine all the different possible arrangements in space for the trillions of particles that make up the air . some of those arrangments might have all the oxygen molecules over here and all the nitrogen molecules over there , separated . but far more of the possible arrangements have those molecules mixed up with one another . so , entropy favors mixing . energetics deals with attractive forces . and so , if attractive forces are present , the probability of some arrangements can be enhanced , the ones where things are attracted to each other . so , it is always the balance of these two things that determines what happens . on the molecular level , water is comprised of water molecules , made up of two hydrogen atoms and an oxygen atom . as liquid water , these molecules are engaged in a constant and random square dance that is called the hydrogen bonding network . entropy favors keeping the square dance going at all times . there are always more ways that all the water molecules can arrange in a square dance , as compared to if the water molecules did a line dance . so , the square dance constantly goes on . so , what happens when you put salt in the water ? well , on the molecular level , salt is actually made up of two different ions , chlorine and sodium , that are organized like a brick wall . they show up to the dance as a big group in formation and sit on the side at first , shy and a bit reluctant to break apart into individual ions to join the dance . but secretly , those shy dancers just want someone to ask them to join . so , when a water randomly bumps into one of them and pulls them into the dance away from their group , they go . and once they go into the dance , they do n't come back out . and in fact , the addition of the salt ions adds more possible dance positions in the square dance , so it is favored for them to stay dancing with water . now , let 's take oil . with oil , the molecules are sort of interested in dancing with water , so entropy favors them joining the dance . the problem is that oil molecules are wearing gigantic ballgowns , and they 're way bigger than water molecules . so , when an oil molecule gets pulled in , their size is really disruptive to the dance and the random exchange of partners that the waters engage in , a very important part of the dance . in addition , they are not great dancers . the water molecules try to engage the oil molecules in the dance , but they just keep bumping into their dresses and taking up all the room on the dance floor . there are way more ways the waters can dance when the oil gets off the floor , so the waters squeeze out the oil , pushing it back to the bench with the others . pretty soon , when a large number of oils have been squeezed over to the side , they band together to commiserate about how unfair the waters are being and stick together as a group . so , it is this combination of the interactions between molecules and the configurations available to them when they 're moving randomly that dictates whether they mix . in other words , water and oil do n't mix because they just do n't make great dance partners .
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well , in a word , chemistry , but that 's not very satisfying , is it ? well , the reason salt dissolves and oil does not comes down to the two big reasons why anything happens at all : energetics and entropy . energetics deals primarily with the attractive forces between things .
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in the video , “ dancing ” is used as an analogy to convey the ideas of energetics and entropy . can you build an explanation for why salt dissolves and oil doesn ’ t without using an analogy or personifying the ions and molecules ( referred to as anthropomorphism ) ? use only the definitions of energetics and entropy when building your explanation .
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translator : andrea mcdonough reviewer : bedirhan cinar the brain is the center of all of our thoughts , dreams , emotions , and memories . it 's what makes us who we are . but , there is still a lot that we do n't know about the brain . scientists have worked for years on trying to understand the human brain using techniques like eeg and fmri , where we scan the brain from the outside . but what if we could look inside the brains of humans and watch them as they work ? well , now we can by looking at the brains of people who are already going through surgery for clinical reasons , like curing epilepsy . epilepsy is a disease in which a faulty part of the brain starts working spontaneously for no apparent reason . it 's like an earthquake but inside your head . there 's no way to know in advance when a seizure will occur , so the patients are always at risk of unexpectedly losing control . there are drugs that treat epilepsy , but these do n't always work . some patients who do n't respond well to the drugs can undergo a different treatment where the faulty part in their brain , the part that starts the seizures , is surgically removed . the challenge is knowing which part to take out . how do you figure out which bit of the brain is faulty ? in order to find the exact location of the seizure onset , doctors embed electrodes directly into the patient 's brain around the suspected seizure center . the patient then stays in the hospital for a few days , waiting to have a seizure with the electrodes constantly recording the activity inside his or her brain . yes , now we want the patient to have a seizure so doctors can use the embedded electrodes to measure it and learn exactly where its origin was . after doctors are sure where the seizures come from in the brain , they can take the electrodes out . now they know what part of the brain they can remove in order to cure the patient . these brain electrodes can tell us more than just where the seizures happen . based on where the doctors place the electrodes in the brain , we can ask questions about what the brain does . sometimes we find one cell that starts bursting in activity every time the patient sees a particular picture , for example , a picture of marilyn monroe . see , every time the patient sees marilyn monroe , some specific cells fire in the brain . you can now know when the patient is thinking of marilyn monroe just by listening to these cells fire . when we find one or a few of these cells with each patient , we can then do all kinds of fancy things . for example , we can connect the recording electrode to a cursor on a screen and have the patient move the cursor left or right just by thinking of things . this can help people who lost the ability to move their hands , like people with spinal cord injuries or wounded soldiers , by having them control a prosthetic arm directly with their brain . our brain is a brilliant device which can make predictions about the future . for example , we can all know which word will appear at the end of this ... sentence . the brain can solve complicated problems , imagine the entire universe , and grasp concepts such as infinity or unicorns . the brain produces complex emotions like love or jealousy , it 's what makes us creative and curious , and it can even contemplate about itself . and the brain is the organ we use to study the brain . i think that the brain is the most beautiful organ in our body , but then i ask myself , `` which organ is making me think that ? ''
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but , there is still a lot that we do n't know about the brain . scientists have worked for years on trying to understand the human brain using techniques like eeg and fmri , where we scan the brain from the outside . but what if we could look inside the brains of humans and watch them as they work ?
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according to cerf , the brain is the most astonishing part of the human body . why ?
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our planet 's diverse thriving ecosystems may seem like permanent fixtures , but they 're actually vulnerable to collapse . jungles can become deserts , and reefs can become lifeless rocks , even without cataclysmic events , like volcanoes and asteroids . what makes one ecosystem strong and another weak in the face of change ? the answer , to a large extent , is biodiversity . biodiversity is built out of three intertwined features : ecosystem diversity , species diversity , and genetic diversity . the more intertwining there is between these features , the denser and more resilient the weave becomes . take the amazon rainforest , one of the most biodiverse regions on earth due to its complex ecosystems , huge mix of species , and the genetic variety within those species . here are tangled liana vines , which crawl up from the forest floor to the canopy , intertwining with treetops and growing thick wooden stems that support these towering trees . helped along by the vines , trees provide the seeds , fruits and leaves to herbivores , such as the tapir and the agouti , which disperse their seeds throughout the forest so they can grow . leftovers are consumed by the millions of insects that decompose and recycle nutrients to create rich soil . the rainforest is a huge system filled with many smaller systems , like this , each packed with interconnected species . every link provides stability to the next , strengthening biodiversity 's weave . that weave is further reinforced by the genetic diversity within individual species , which allows them to cope with changes . species that lack genetic diversity due to isolation or low population numbers , are much more vulnerable to fluctuations caused by climate change , disease or habitat fragmentation . whenever a species disappears because of its weakened gene pool , a knot is untied and parts of the net disintegrate . so , what if we were to remove one species from the rainforest ? would the system fall apart ? probably not . the volume of species , their genetic diversity , and the complexity of the ecosystems form such rich biodiversity in this forest that one species gap in the weave wo n't cause it to unravel . the forest can stay resilient and recover from change . but that 's not true in every case . in some environments , taking away just one important component can undermine the entire system . take coral reefs , for instance . many organisms in a reef are dependent on the coral . it provides key microhabitats , shelter and breeding grounds for thousand of species of fish , crustaceans and mollusks . corals also form interdependent relationships with fungi and bacteria . the coral itself is a loom that allows the tangled net of biodiversity to be woven . that makes coral a keystone organism , one that many others depend on for their suvival . so what happens when destructive fishing practices , pollution and ocean acidification weaken coral or even kill it altogether ? exactly what you might think . the loss of this keystone species leaves its dependents at a loss , too , threatening the entire fabric of the reef . ecosystem , species and genetic diversity together form the complex tangled weave of biodiversity that is vital for the survival of organisms on earth . we humans are woven into this biodiversity , too . when just a few strands are lost , our own well-being is threatened . cut too many links , and we risk unraveling it all . what the future brings is unpredictable , but biodiversity can give us an insurance policy , earth 's own safety net to safeguard our survival .
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in some environments , taking away just one important component can undermine the entire system . take coral reefs , for instance . many organisms in a reef are dependent on the coral .
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coral reefs are essential for the survival of other organisms . they provide :
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packed inside every cell in your body is a set of genetic instructions , 3.2 billion base pairs long . deciphering these directions would be a monumental task but could offer unprecedented insight about the human body . in 1990 , a consortium of 20 international research centers embarked on the world 's largest biological collaboration to accomplish this mission . the human genome project proposed to sequence the entire human genome over 15 years with $ 3 billion of public funds . then , seven years before its scheduled completion , a private company called celera announced that they could accomplish the same goal in just three years and at a fraction of the cost . the two camps discussed a joint venture , but talks quickly fell apart as disagreements arose over legal and ethical issues of genetic property . and so the race began . though both teams used the same technology to sequence the entire human genome , it was their strategies that made all the difference . their paths diverged in the most critical of steps : the first one . in the human genome project 's approach , the genome was first divided into smaller , more manageable chunks about 150,000 base pairs long that overlapped each other a little bit on both ends . each of these fragments of dna was inserted inside a bacterial artificial chromosome where they were cloned and fingerprinted . the fingerprints showed scientists where the fragments overlapped without knowing the actual sequence . using the overlapping bits as a guide , the researchers marked each fragment 's place in the genome to create a contiguous map , a process that took about six years . the cloned fragments were sequenced in labs around the world following one of the project 's two major principles : that collaboration on our shared heritage was open to all nations . in each case , the fragments were arbitrarily broken up into small , overlapping pieces about 1,000 base pairs long . then , using a technology called the sanger method , each piece was sequenced letter by letter . this rigorous map-based approach called hierarchical shotgun sequencing minimized the risk of misassembly , a huge hazard of sequencing genomes with many repetitive portions , like the human genome . the consortium 's `` better safe than sorry '' approach contrasted starkly with celera 's strategy called whole genome shotgun sequencing . it hinged on skipping the mapping phase entirely , a faster , though foolhardy , approach according to some . the entire genome was directly chopped up into a giant heap of small , overlapping bits . once these bits were sequenced via the sanger method , celera would take the formidable risk of reconstructing the genome using just the overlaps . but perhaps their decision was n't such a gamble because guess whose freshly completed map was available online for free ? the human genome consortium , in accordance with the project 's second major principle which held that all of the project 's data would be shared publicly within 24 hours of collection . so in 1998 , scientists around the world were furiously sequencing lines of genetic code using the tried and true , yet laborious , sanger method . finally , after three exhausting years of continuous sequencing and assembling , the verdict was in . in february 2001 , both groups simultaneously published working drafts of more than 90 % of the human genome , several years ahead of the consortium 's schedule . the race ended in a tie . the human genome project 's practice of immediately sharing its data was an unusual one . it is more typical for scientists to closely guard their data until they are able to analyze it and publish their conclusions . instead , the human genome project accelerated the pace of research and created an international collaboration on an unprecedented scale . since then , robust investment in both the public and private sector has led to the identification of many disease related genes and remarkable advances in sequencing technology . today , a person 's genome can be sequenced in just a few days . however , reading the genome is only the first step . we 're a long way away from understanding what most of our genes do and how they are controlled . those are some of the challenges for the next generation of ambitious research initiatives .
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in 1990 , a consortium of 20 international research centers embarked on the world 's largest biological collaboration to accomplish this mission . the human genome project proposed to sequence the entire human genome over 15 years with $ 3 billion of public funds . then , seven years before its scheduled completion , a private company called celera announced that they could accomplish the same goal in just three years and at a fraction of the cost .
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when the human genome project was proposed , what was the projected time to completion ?
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one day , i found myself at the top of a mountain , one descent to go , one last chance to fulfill a lifelong dream . i was n't even old enough to walk into a pg-13 movie alone when my dream took roots . yet there i stood , my three teammates by my side , facing the opportunity to make history . my mind wandered , just for half a second , but that half-second was filled with a lifetime of memories , and two decisions that brought me here to the top of the mountain . i made the first decision after a very challenging period in my career as an athlete -- five years of recurring injuries as a track athlete . five years -- that 's a long time to dedicate to anything . but as much as i loved track , the injuries were slowly killing my drive and my dreams . my injuries had me feeling like a failure at a sport i was once great at . the last of the series of injuries required major elbow surgery . as i sat on my couch , days out of surgery , i thought of an old coach and mentor 's words , comparing me to a great bobsledder he once knew . `` bobsled ? no way ! '' but after year upon year of not reaching the goals i set for myself in track , it was time for a change . so i reached out to the us olympic committee , and they told me to start training . i was going to be a bobsledder ! i did n't know anything about it , but the first decision had been made . there i was , in what felt like a blink of an eye later , about to push my four-man sled with my team to the chance of olympic gold , olympic glory . `` back set ! front set ! ready and -- '' the driver yelled , and off we went . we dug as deep as we could , and as the cadence of our steps increased and the sled accelerated , we left everything we had on the track , before leaving the ice and boarding our night train sled . and a calm came over me . and once in the sled , as it was picking up speed , for just another millisecond , my mind went back to that day on the couch . `` how can i train for the bobsled team without getting hurt over and over again like before ? '' i looked in the mirror and realized i still wanted to compete . i still wanted to succeed . but i had to face the reality that my getting hurt was n't to be blamed elsewhere . i realized that if i had a problem it was up to me to change it , and that what i had been doing all this time may not have been best for me . i had to confront my reality and make a change , and that was the second decision . the decision in my mind not to get hurt anymore had many layers , but it mostly had to do with taking responsibility for all the variables in my life . if i thought something i would do or something i felt would lead me to injury , then it most certainly would . i would have to have a fundamental shift in mindset . i learned to let go of the fears i had trained myself to have over the years and decided to trust myself and my body to push through situations i had thought insurmountable before . what followed those five years of injuries were nine years of not missing one race i entered for the usa national and olympic teams . because i made a decision , then another one , and held true to those two decisions , i found myself back with my team approaching 90 miles per hour . and as we came around the last corners , i could hear the crowd cheering and the cowbells blaring , and a hard `` you ! '' coming from the masses as we passed by at 95 miles an hour . but someone was n't yelling `` you ! '' at us , they were yelling `` usa ! '' we were moving so fast , we only heard the first piece of it . we then came around the last bend , and when we all looked up , the clock simply read `` 1 . '' we had done it ; we were olympic gold medalists . we were the best in the world . my hands went up immediately , as the moment i had been waiting for my entire life had finally come true . and as our sled slowly came to a stop and i looked into the crowd to see my mom , dad , sister and family and friends crying for me , i knew my decisions had been worth the sacrifice , worth the fear . two decisions and those five minutes sitting on that couch began to change my life , and sticking to them fulfilled my dreams . it was those decisions and standing by them that ultimately gave me the confidence to perform at the olympic games . what two decisions can you make and stick to that will change your life forever ? i challenge you to look at what you 're doing in your life and think of what you dream to do .
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the decision in my mind not to get hurt anymore had many layers , but it mostly had to do with taking responsibility for all the variables in my life . if i thought something i would do or something i felt would lead me to injury , then it most certainly would . i would have to have a fundamental shift in mindset .
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what did mesler realize about the problems that he would face as an athlete ?
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here 's a conundrum : identical twins originate from the same dna , so how can they turn out so different even in traits that have a significant genetic component ? for instance , why might one twin get heart disease at 55 , while her sister runs marathons in perfect health ? nature versus nurture has a lot to do with it , but a deeper related answer can be found within something called epigenetics . that 's the study of how dna interacts with the multitude of smaller molecules found within cells , which can activate and deactivate genes . if you think of dna as a recipe book , those molecules are largely what determine what gets cooked when . they are n't making any conscious choices themselves , rather their presence and concentration within cells makes the difference . so how does that work ? genes in dna are expressed when they 're read and transcribed into rna , which is translated into proteins by structures called ribosomes . and proteins are much of what determines a cell 's characteristics and function . epigenetic changes can boost or interfere with the transcription of specific genes . the most common way interference happens is that dna , or the proteins it 's wrapped around , gets labeled with small chemical tags . the set of all of the chemical tags that are attached to the genome of a given cell is called the epigenome . some of these , like a methyl group , inhibit gene expression by derailing the cellular transcription machinery or causing the dna to coil more tightly , making it inaccessible . the gene is still there , but it 's silent . boosting transcription is essentially the opposite . some chemical tags will unwind the dna , making it easier to transcribe , which ramps up production of the associated protein . epigenetic changes can survive cell division , which means they could affect an organism for its entire life . sometimes that 's a good thing . epigenetic changes are part of normal development . the cells in an embryo start with one master genome . as the cells divide , some genes are activated and others inhibited . over time , through this epigenetic reprogramming , some cells develop into heart cells , and others into liver cells . each of the approximately 200 cell types in your body has essentially the same genome but its own distinct epigenome . the epigenome also mediates a lifelong dialogue between genes and the environment . the chemical tags that turn genes on and off can be influenced by factors including diet , chemical exposure , and medication . the resulting epigenetic changes can eventually lead to disease , if , for example , they turn off a gene that makes a tumor-suppressing protein . environmentally-induced epigenetic changes are part of the reason why genetically identical twins can grow up to have very different lives . as twins get older , their epigenomes diverge , affecting the way they age and their susceptibility to disease . even social experiences can cause epigenetic changes . in one famous experiment , when mother rats were n't attentive enough to their pups , genes in the babies that helped them manage stress were methylated and turned off . and it might not stop with that generation . most epigenetic marks are erased when egg and sperm cells are formed . but now researchers think that some of those imprints survive , passing those epigenetic traits on to the next generation . your mother 's or your father 's experiences as a child , or choices as adults , could actually shape your own epigenome . but even though epigenetic changes are sticky , they 're not necessarily permanent . a balanced lifestyle that includes a healthy diet , exercise , and avoiding exposure to contaminants may in the long run create a healthy epigenome . it 's an exciting time to be studying this . scientists are just beginning to understand how epigenetics could explain mechanisms of human development and aging , as well as the origins of cancer , heart disease , mental illness , addiction , and many other conditions . meanwhile , new genome editing techniques are making it much easier to identify which epigenetic changes really matter for health and disease . once we understand how our epigenome influences us , we might be able to influence it , too .
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for instance , why might one twin get heart disease at 55 , while her sister runs marathons in perfect health ? nature versus nurture has a lot to do with it , but a deeper related answer can be found within something called epigenetics . that 's the study of how dna interacts with the multitude of smaller molecules found within cells , which can activate and deactivate genes .
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what is true regarding the role of epigenetics in biological processes ?
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a few years ago , i broke into my own house . i had just driven home , it was around midnight in the dead of montreal winter , i had been visiting my friend , jeff , across town , and the thermometer on the front porch read minus 40 degrees -- and do n't bother asking if that 's celsius or fahrenheit , minus 40 is where the two scales meet -- it was very cold . and as i stood on the front porch fumbling in my pockets , i found i did n't have my keys . in fact , i could see them through the window , lying on the dining room table where i had left them . so i quickly ran around and tried all the other doors and windows , and they were locked tight . i thought about calling a locksmith -- at least i had my cellphone , but at midnight , it could take a while for a locksmith to show up , and it was cold . i could n't go back to my friend jeff 's house for the night because i had an early flight to europe the next morning , and i needed to get my passport and my suitcase . so , desperate and freezing cold , i found a large rock and i broke through the basement window , cleared out the shards of glass , i crawled through , i found a piece of cardboard and taped it up over the opening , figuring that in the morning , on the way to the airport , i could call my contractor and ask him to fix it . this was going to be expensive , but probably no more expensive than a middle-of-the-night locksmith , so i figured , under the circumstances , i was coming out even . now , i 'm a neuroscientist by training and i know a little bit about how the brain performs under stress . it releases cortisol that raises your heart rate , it modulates adrenaline levels and it clouds your thinking . so the next morning , when i woke up on too little sleep , worrying about the hole in the window , and a mental note that i had to call my contractor , and the freezing temperatures , and the meetings i had upcoming in europe , and , you know , with all the cortisol in my brain , my thinking was cloudy , but i did n't know it was cloudy because my thinking was cloudy . ( laughter ) and it was n't until i got to the airport check-in counter , that i realized i did n't have my passport . ( laughter ) so i raced home in the snow and ice , 40 minutes , got my passport , raced back to the airport , i made it just in time , but they had given away my seat to someone else , so i got stuck in the back of the plane , next to the bathrooms , in a seat that would n't recline , on an eight-hour flight . well , i had a lot of time to think during those eight hours and no sleep . ( laughter ) and i started wondering , are there things that i can do , systems that i can put into place , that will prevent bad things from happening ? or at least if bad things happen , will minimize the likelihood of it being a total catastrophe . so i started thinking about that , but my thoughts did n't crystallize until about a month later . i was having dinner with my colleague , danny kahneman , the nobel prize winner , and i somewhat embarrassedly told him about having broken my window , and , you know , forgotten my passport , and danny shared with me that he 'd been practicing something called prospective hindsight . ( laughter ) it 's something that he had gotten from the psychologist gary klein , who had written about it a few years before , also called the pre-mortem . now , you all know what the postmortem is . whenever there 's a disaster , a team of experts come in and they try to figure out what went wrong , right ? well , in the pre-mortem , danny explained , you look ahead and you try to figure out all the things that could go wrong , and then you try to figure out what you can do to prevent those things from happening , or to minimize the damage . so what i want to talk to you about today are some of the things we can do in the form of a pre-mortem . some of them are obvious , some of them are not so obvious . i 'll start with the obvious ones . around the home , designate a place for things that are easily lost . now , this sounds like common sense , and it is , but there 's a lot of science to back this up , based on the way our spatial memory works . there 's a structure in the brain called the hippocampus , that evolved over tens of thousands of years , to keep track of the locations of important things -- where the well is , where fish can be found , that stand of fruit trees , where the friendly and enemy tribes live . the hippocampus is the part of the brain that in london taxicab drivers becomes enlarged . it 's the part of the brain that allows squirrels to find their nuts . and if you 're wondering , somebody actually did the experiment where they cut off the olfactory sense of the squirrels , and they could still find their nuts . they were n't using smell , they were using the hippocampus , this exquisitely evolved mechanism in the brain for finding things . but it 's really good for things that do n't move around much , not so good for things that move around . so this is why we lose car keys and reading glasses and passports . so in the home , designate a spot for your keys -- a hook by the door , maybe a decorative bowl . for your passport , a particular drawer . for your reading glasses , a particular table . if you designate a spot and you 're scrupulous about it , your things will always be there when you look for them . what about travel ? take a cell phone picture of your credit cards , your driver 's license , your passport , mail it to yourself so it 's in the cloud . if these things are lost or stolen , you can facilitate replacement . now these are some rather obvious things . remember , when you 're under stress , the brain releases cortisol . cortisol is toxic , and it causes cloudy thinking . so part of the practice of the pre-mortem is to recognize that under stress you 're not going to be at your best , and you should put systems in place . and there 's perhaps no more stressful a situation than when you 're confronted with a medical decision to make . and at some point , all of us are going to be in that position , where we have to make a very important decision about the future of our medical care or that of a loved one , to help them with a decision . and so i want to talk about that . and i 'm going to talk about a very particular medical condition . but this stands as a proxy for all kinds of medical decision-making , and indeed for financial decision-making , and social decision-making -- any kind of decision you have to make that would benefit from a rational assessment of the facts . so suppose you go to your doctor and the doctor says , `` i just got your lab work back , your cholesterol 's a little high . '' now , you all know that high cholesterol is associated with an increased risk of cardiovascular disease , heart attack , stroke . and so you 're thinking having high cholesterol is n't the best thing , and so the doctor says , `` you know , i 'd like to give you a drug that will help you lower your cholesterol , a statin . '' and you 've probably heard of statins , you know that they 're among the most widely prescribed drugs in the world today , you probably even know people who take them . and so you 're thinking , `` yeah ! give me the statin . '' but there 's a question you should ask at this point , a statistic you should ask for that most doctors do n't like talking about , and pharmaceutical companies like talking about even less . it 's for the number needed to treat . now , what is this , the nnt ? it 's the number of people that need to take a drug or undergo a surgery or any medical procedure before one person is helped . and you 're thinking , what kind of crazy statistic is that ? the number should be one . my doctor would n't prescribe something to me if it 's not going to help . but actually , medical practice does n't work that way . and it 's not the doctor 's fault , if it 's anybody 's fault , it 's the fault of scientists like me . we have n't figured out the underlying mechanisms well enough . but glaxosmithkline estimates that 90 percent of the drugs work in only 30 to 50 percent of the people . so the number needed to treat for the most widely prescribed statin , what do you suppose it is ? how many people have to take it before one person is helped ? 300 . this is according to research by research practitioners jerome groopman and pamela hartzband , independently confirmed by bloomberg.com . i ran through the numbers myself . 300 people have to take the drug for a year before one heart attack , stroke or other adverse event is prevented . now you 're probably thinking , `` well , ok , one in 300 chance of lowering my cholesterol . why not , doc ? give me the prescription anyway . '' but you should ask at this point for another statistic , and that is , `` tell me about the side effects . '' right ? so for this particular drug , the side effects occur in five percent of the patients . and they include terrible things -- debilitating muscle and joint pain , gastrointestinal distress -- but now you 're thinking , `` five percent , not very likely it 's going to happen to me , i 'll still take the drug . '' but wait a minute . remember under stress you 're not thinking clearly . so think about how you 're going to work through this ahead of time , so you do n't have to manufacture the chain of reasoning on the spot . 300 people take the drug , right ? one person 's helped , five percent of those 300 have side effects , that 's 15 people . you 're 15 times more likely to be harmed by the drug than you are to be helped by the drug . now , i 'm not saying whether you should take the statin or not . i 'm just saying you should have this conversation with your doctor . medical ethics requires it , it 's part of the principle of informed consent . you have the right to have access to this kind of information to begin the conversation about whether you want to take the risks or not . now you might be thinking i 've pulled this number out of the air for shock value , but in fact it 's rather typical , this number needed to treat . for the most widely performed surgery on men over the age of 50 , removal of the prostate for cancer , the number needed to treat is 49 . that 's right , 49 surgeries are done for every one person who 's helped . and the side effects in that case occur in 50 percent of the patients . they include impotence , erectile dysfunction , urinary incontinence , rectal tearing , fecal incontinence . and if you 're lucky , and you 're one of the 50 percent who has these , they 'll only last for a year or two . so the idea of the pre-mortem is to think ahead of time to the questions that you might be able to ask that will push the conversation forward . you do n't want to have to manufacture all of this on the spot . and you also want to think about things like quality of life . because you have a choice oftentimes , do you i want a shorter life that 's pain-free , or a longer life that might have a great deal of pain towards the end ? these are things to talk about and think about now , with your family and your loved ones . you might change your mind in the heat of the moment , but at least you 're practiced with this kind of thinking . remember , our brain under stress releases cortisol , and one of the things that happens at that moment is a whole bunch on systems shut down . there 's an evolutionary reason for this . face-to-face with a predator , you do n't need your digestive system , or your libido , or your immune system , because if you 're body is expending metabolism on those things and you do n't react quickly , you might become the lion 's lunch , and then none of those things matter . unfortunately , one of the things that goes out the window during those times of stress is rational , logical thinking , as danny kahneman and his colleagues have shown . so we need to train ourselves to think ahead to these kinds of situations . i think the important point here is recognizing that all of us are flawed . we all are going to fail now and then . the idea is to think ahead to what those failures might be , to put systems in place that will help minimize the damage , or to prevent the bad things from happening in the first place . getting back to that snowy night in montreal , when i got back from my trip , i had my contractor install a combination lock next to the door , with a key to the front door in it , an easy to remember combination . and i have to admit , i still have piles of mail that have n't been sorted , and piles of emails that i have n't gone through . so i 'm not completely organized , but i see organization as a gradual process , and i 'm getting there . thank you very much . ( applause )
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if these things are lost or stolen , you can facilitate replacement . now these are some rather obvious things . remember , when you 're under stress , the brain releases cortisol . cortisol is toxic , and it causes cloudy thinking .
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what are some of the things that your brain does when operating under stress ?
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on a december afternoon in chicago during the middle of world war ii , scientists cracked open the nucleus at the center of the uranium atom and turned nuclear mass into energy over and over again . they did this by creating for the first time a chain reaction inside a new engineering marvel : the nuclear reactor . since then , the ability to mine great amounts of energy from uranium nuclei has led some to bill nuclear power as a plentiful utopian source of electricity . a modern nuclear reactor generates enough electricity from one kilogram of fuel to power an average american household for nearly 34 years . but rather than dominate the global electricity market , nuclear power has declined from an all-time high of 18 % in 1996 to 11 % today . and it 's expected to drop further in the coming decades . what happened to the great promise of this technology ? it turns out nuclear power faces many hurdles , including high construction costs and public opposition . and behind these problems lie a series of unique engineering challenges . nuclear power relies on the fission of uranium nuclei and a controlled chain reaction that reproduces this splitting in many more nuclei . the atomic nucleus is densely packed with protons and neutrons bound by a powerful nuclear force . most uranium atoms have a total of 238 protons and neutrons , but roughly one in every 140 lacks three neutrons , and this lighter isotope is less tightly bound . compared to its more abundant cousin , a strike by a neutron easily splits the u-235 nuclei into lighter , radioactive elements called fission products , in addition to two to three neutrons , gamma rays , and a few neutrinos . during fission , some nuclear mass transforms into energy . a fraction of the newfound energy powers the fast-moving neutrons , and if some of them strike uranium nuclei , fission results in a second larger generation of neutrons . if this second generation of neutrons strike more uranium nuclei , more fission results in an even larger third generation , and so on . but inside a nuclear reactor , this spiraling chain reaction is tamed using control rods made of elements that capture excess neutrons and keep their number in check . with a controlled chain reaction , a reactor draws power steadily and stably for years . the neutron-led chain reaction is a potent process driving nuclear power , but there 's a catch that can result in unique demands on the production of its fuel . it turns out , most of the neutrons emitted from fission have too much kinetic energy to be captured by uranium nuclei . the fission rate is too low and the chain reaction fizzles out . the first nuclear reactor built in chicago used graphite as a moderator to scatter and slow down neutrons just enough to increase their capture by uranium and raise the rate of fission . modern reactors commonly use purified water as a moderator , but the scattered neutrons are still a little too fast . to compensate and keep up the chain reaction , the concentration of u-235 is enriched to four to seven times its natural abundance . today , enrichment is often done by passing a gaseous uranium compound through centrifuges to separate lighter u-235 from heavier u-238 . but the same process can be continued to highly enrich u-235 up to 130 times its natural abundance and create an explosive chain reaction in a bomb . methods like centrifuge processing must be carefully regulated to limit the spread of bomb-grade fuel . remember , only a fraction of the released fission energy goes into speeding up neutrons . most of the nuclear power goes into the kinetic energy of the fission products . those are captured inside the reactor as heat by a coolant , usually purified water . this heat is eventually used to drive an electric turbine generator by steam just outside the reactor . water flow is critical not only to create electricity , but also to guard against the most dreaded type of reactor accident , the meltdown . if water flow stops because a pipe carrying it breaks , or the pumps that push it fail , the uranium heats up very quickly and melts . during a nuclear meltdown , radioactive vapors escape into the reactor , and if the reactor fails to hold them , a steel and concrete containment building is the last line of defense . but if the radioactive gas pressure is too high , containment fails and the gasses escape into the air , spreading as far and wide as the wind blows . the radioactive fission products in these vapors eventually decay into stable elements . while some decay in a few seconds , others take hundreds of thousands of years . the greatest challenge for a nuclear reactor is to safely contain these products and keep them from harming humans or the environment . containment does n't stop mattering once the fuel is used up . in fact , it becomes an even greater storage problem . every one to two years , some spent fuel is removed from reactors and stored in pools of water that cool the waste and block its radioactive emissions . the irradiated fuel is a mix of uranium that failed to fission , fission products , and plutonium , a radioactive material not found in nature . this mix must be isolated from the environment until it has all safely decayed . many countries propose deep time storage in tunnels drilled far underground , but none have been built , and there 's great uncertainty about their long-term security . how can a nation that has existed for only a few hundred years plan to guard plutonium through its radioactive half-life of 24,000 years ? today , many nuclear power plants sit on their waste , instead , storing them indefinitely on site . apart from radioactivity , there 's an even greater danger with spent fuel . plutonium can sustain a chain reaction and can be mined from the waste to make bombs . storing spent fuel is thus not only a safety risk for the environment , but also a security risk for nations . who should be the watchmen to guard it ? visionary scientists from the early years of the nuclear age pioneered how to reliably tap the tremendous amount of energy inside an atom - as an explosive bomb and as a controlled power source with incredible potential . but their successors have learned humbling insights about the technology 's not-so-utopian industrial limits . mining the subatomic realm makes for complex , expensive , and risky engineering .
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but if the radioactive gas pressure is too high , containment fails and the gasses escape into the air , spreading as far and wide as the wind blows . the radioactive fission products in these vapors eventually decay into stable elements . while some decay in a few seconds , others take hundreds of thousands of years .
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plutonium is a radioactive material , exposure to which is hazardous to human health , and is one of the few materials that can be used to make a nuclear weapon . the time it takes for half of any initial quantity of plutonium to decay into stable non-radioactive products is roughly :
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the geography of our planet is in flux . each continent has ricocheted around the globe on one or more tectonic plates , changing quite dramatically with time . today , we 'll focus on north america and how its familiar landscape and features emerged over hundreds of millions of years . our story begins about 750 million years ago . as the super continent rodinia becomes unstable , it rifts along what 's now the west coast of north america to create the panthalassa ocean . you 're seeing an ancestral continent called laurentia , which grows over the next few hundred million years as island chains collide with it and add land mass . we 're now at 400 million years ago . off today 's east coast , the massive african plate inches westward , closing the ancient iapetus ocean . it finally collides with laurentia at 250 million years to form another supercontinent pangea . the immense pressure causes faulting and folding , stacking up rock to form the appalachian mountains . let 's fast forward a bit . about 100 million years later , pangea breaks apart , opening the southern atlantic ocean between the new north american plate and the african plate . we forge ahead , and now the eastward-moving farallon plate converges with the present-day west coast . the farallon plate 's greater density makes it sink beneath north america . this is called subduction , and it diffuses water into the magma-filled mantle . that lowers the magma 's melting point and makes it rise into the overlying north american plate . from a subterranean chamber , the magma travels upwards and erupts along a chain of volcanos . magma still deep underground slowly cools , crystallizing to form solid rock , including the granite now found in yosemite national park and the sierra nevada mountains . we 'll come back to that later . now , it 's 85 million years ago . the farallon plate becomes less steep , causing volcanism to stretch eastward and eventually cease . as the farallon plate subducts , it compresses north america , thrusting up mountain ranges like the rockies , which extend over 3,000 miles . soon after , the eurasian plate rifts from north america , opening the north atlantic ocean . we 'll fast forward again . the colorado plateau now uplifts , likely due to a combination of upward mantle flow and a thickened north american plate . in future millennia , the colorado river will eventually sculpt the plateau into the epic grand canyon . 30 million years ago , the majority of the farallon plate sinks into the mantle , leaving behind only small corners still subducting . the pacific and north american plates converge and a new boundary called the san andreas fault forms . here , north america moves to the south , sliding against the pacific plate , which shifts to the north . this plate boundary still exists today , and moves about 30 millimeters per year capable of causing devastating earthquakes . the san andreas also pulls apart western north america across a wide rift zone . this extensional region is called the basin and range province , and through uplift and erosion , is responsible for exposing the once deep granite of yosemite and the sierra nevada . another 15 million years off the clock , and magma from the mantle burns a giant hole into western north america , periodically erupting onto the surface . today , this hotspot feeds an active supervolcano beneath yellowstone national park . it has n't erupted in the last 174,000 years , but if it did , its sheer force could blanket most of the continent with ash that would blacken the skies and threaten humanity . the yellowstone supervolcano is just one reminder that the earth continues to seethe below our feet . its mobile plates put the planet in a state of constant flux . in another few hundred million years , who knows how the landscape of north america will have changed . as the continent slowly morphs into something unfamiliar , only geological time will tell .
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the colorado plateau now uplifts , likely due to a combination of upward mantle flow and a thickened north american plate . in future millennia , the colorado river will eventually sculpt the plateau into the epic grand canyon . 30 million years ago , the majority of the farallon plate sinks into the mantle , leaving behind only small corners still subducting .
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in order for the colorado river to carve the deep grand canyon , what must happen first ?
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translator : andrea mcdonough reviewer : bedirhan cinar miss gayle 's 5 steps to slam poetry , a lesson of transformation . step 1 : write it all down . `` take one memory , explore it like a new land , '' the visiting poet tells the class . `` do n't leave anything out . '' tyler sits in this high school workshop , dizzy with where to start . memories wander in and out of his heart like vagrants searching for home . he bends to his desk , he writes , `` the snow goes black when the moon turns its eyes away , all paper is yellow , all letters spell eviction note , mama 's lies are footsteps too many to count . making excuses on black snow . 'i paid the rent , this is your room forever , baby . i love you . ' but , she would n't even look at me . '' step 2 : read out loud . as he writes , his lips try on words then toss them out like bad tenants . he pushes his desk back , stands . `` aunt jocelyn 's rice pudding was sweet , but that 's not what i want to write . have you ever been so cold your hair becomes an icicle ? your little sister 's fear of the dark freezes on her lips like she 's kissed the ice tray ? how hungry have you been ? '' step 3 : cut the fat . abandon extra words . his pen becomes a machete , slashing ands , thens , becauses . step 4 : read out loud , again . the 11th grade boy makes sure step 3 's cuts were n't too deep . step 5 : add flava . juice , power , movement , emotion . `` vanilla flavoring is the secret to my aunt 's pudding . i kick out a few raisins but leave one or two . life needs some bitter to man up the sweet . '' his hands reach out like shells to hold our disbelief . is this tyler speaking ? the one who keeps his eyes on the floor like they 're carrying something heavy ? voice rattles windows . `` i am free now . '' body quivers with the pulse of each word . `` the sun 's joy melts snow . '' fingers trace the curve of his jaw . `` my aunt 's face was warm as a water heater when she let us in that night . '' our boy is done , his transformation complete . step 1 : write it all down . step 2 : read out loud . step 3 : cut the fat . step 4 : read out loud . step 5 : add flava . tyler 's first poem takes residence in his heart . he flings his arms wide like an open door . welcome home !
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his hands reach out like shells to hold our disbelief . is this tyler speaking ? the one who keeps his eyes on the floor like they 're carrying something heavy ?
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what is the yellow paper tyler is writing about ?
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translator : tom carter reviewer : bedirhan cinar geckos and grasshoppers , worms and watermelons , elephants and escherichia coli , man and mushroom . all so different in form and function , but amazingly the same in how their form and function are determined . first , all these organisms are made of one or more cells , and every cell of every living thing on earth contains all the information it takes to create and duplicate and make variations of itself . that information is stored in a very long but quite simple double molecule called dna , or deoxyribonucleic acid . and the dna of every living organism is made of chains of four smaller molecules called nucleotides . what dictates the difference between a man and a mushroom is the sequence of these nucleotides in the long dna chain . the four differing nucleotide parts , called bases , are made of a few carbon , oxygen , hydrogen , nitrogen and phosphorus atoms , and the molecules look like this . and each of these four bases is attached to an identical backbone molecule , a sugar called deoxyribose - the `` d '' in dna - and a phosphate group . let 's simplify these nucleotides and show them like this . so , a single sequence of nucleotides joined by their common sugars would look like this . and the dna molecule where such sequences are stored looks like this . but how does a simple molecule dictate the form and function of millions of different living things ? you can think of dna as a great library of information , information that is used to do one thing and one thing only : direct the building of different protein molecules . and it 's the proteins that build the cells and keep them functioning and changing and reproducing . here 's where the familiar word 'gene ' comes in . if your dna is a library of information , a gene is a book in that library . a gene is a segment of the dna molecule . let 's say your body needs a particular protein , like insulin . to get it , some of your cells send a protein signal through the bloodstream to the cells in your pancreas , where insulin is made . that signal protein tells other proteins in the cell 's nuclei to open up a part of the dna double helix , the insulin gene , and start making insulin proteins . as soon as enough insulin has been produced , another signal protein comes to the pancreas ' cells that tells them to stop making insulin . it 's like looking up a book in the dna library about insulin , and then putting it back when you 're done . there are genes in dna for visible and invisible things that make up your body , like genes for eye color , protein pigments , for skin color , for hair color , for stopping and starting bone growth , for your blood type , for how many fingers or arms and legs you have , for proteins that influence how long you live . your dna probably contains between 25 thousand and 40 thousand genes , while the dna of a worm or a plant or a fruit fly contains about 12 thousand to 20 thousand genes . some of those genes have quite different sequences of nucleotides than yours , and some are similar to yours . though it happens infrequently , our own nucleotide sequences can change as the result of spontaneous or environmental damage which might remove or shift a nucleotide position . this changes the gene involved , and can then change the protein . most of these changes , called mutations , have very little effect on the organism or its descendants . some are mildly damaging , and a few can make the organism better-suited to its environment . it is these tiny changes in dna gene sequences , happening over millions of years , that create the differences among living organisms , from geckos to grasshoppers . worms to watermelons , elephants to escherichia coli , and man to mushroom .
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all so different in form and function , but amazingly the same in how their form and function are determined . first , all these organisms are made of one or more cells , and every cell of every living thing on earth contains all the information it takes to create and duplicate and make variations of itself . that information is stored in a very long but quite simple double molecule called dna , or deoxyribonucleic acid .
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every cell of every living thing on earth contains all the information it needs to create and duplicate and make variations of :
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cerium is one of only two elements which , if you strike it , will make sparks . one of them is iron and the other one is cerium . and so i bought this when i was on holiday a year ago . i haven ’ t had the chance to use it . it contains , it consists of a rod here which claims to have several metals including cerium . let ’ s see if it sparks . ok so cerium , element number 58 , has some bizarre uses , would you believe it ’ s used in self-cleaning ovens . so it ’ s not very easy to do but , once you get the hang of it , it does go quite well . cerium also has uses such for staining glass . so if you want to stain your glass yellow then you could use cerium in that . what is happening is that tiny pieces of cerium are being knocked off and , in the air , they just burst into flames . so , i think , the property is , not so much that it forms a spark , but that you can knock off the right size lumps to make them burn . these things that are being knocked off are probably just a few nanometres , that ’ s a thousandth-millionth of a metre across so they ’ re very tiny size . so then the surface area is high because it ’ s small so it has a large surface compared to its volume . and so it reacts with oxygen very rapidly and heats up and bursts into flame . the point about cerium is that very small particles of cerium oxide are now becoming quite important in various areas of technology . there ’ s a company , or several companies , that are using nano particles of cerium oxide as an additive for fuels to make a particular diesel fuel to try and make it burn better and give more power when you are driving diesel cars . and here in nottingham we are trying to develop new ways of making these nano particles by reacting cerium with high temperature water and it ’ s been quite successful . it ’ s also used in organic synthesis by chemists for making organic molecules because it can be very reactive under certain circumstances . cerium is also used in permanent magnets for obvious applications in magnetism .
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the point about cerium is that very small particles of cerium oxide are now becoming quite important in various areas of technology . there ’ s a company , or several companies , that are using nano particles of cerium oxide as an additive for fuels to make a particular diesel fuel to try and make it burn better and give more power when you are driving diesel cars . and here in nottingham we are trying to develop new ways of making these nano particles by reacting cerium with high temperature water and it ’ s been quite successful .
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which compound of cerium can be used as a fuel additive to produce more power in cars with diesel engines ?
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what is proof ? and why is it so important in mathematics ? proofs provide a solid foundation for mathematicians logicians , statisticians , economists , architects , engineers , and many others to build and test their theories on . and they 're just plain awesome ! let me start at the beginning . i 'll introduce you to a fellow named euclid . as in , `` here 's looking at you , clid . '' he lived in greece about 2,300 years ago , and he 's considered by many to be the father of geometry . so if you 've been wondering where to send your geometry fan mail , euclid of alexandria is the guy to thank for proofs . euclid is not really known for inventing or discovering a lot of mathematics but he revolutionized the way in which it is written , presented , and thought about . euclid set out to formalize mathematics by establishing the rules of the game . these rules of the game are called axioms . once you have the rules , euclid says you have to use them to prove what you think is true . if you ca n't , then your theorem or idea might be false . and if your theorem is false , then any theorems that come after it and use it might be false too . like how one misplaced beam can bring down the whole house . so that 's all that proofs are : using well-established rules to prove beyond a doubt that some theorem is true . then you use those theorems like blocks to build mathematics . let 's check out an example . say i want to prove that these two triangles are the same size and shape . in other words , they are congruent . well , one way to do that is to write a proof that shows that all three sides of one triangle are congruent to all three sides of the other triangle . so how do we prove it ? first , i 'll write down what we know . we know that point m is the midpoint of ab . we also know that sides ac and bc are already congruent . now let 's see . what does the midpoint tell us ? luckily , i know the definition of midpoint . it is basically the point in the middle . what this means is that am and bm are the same length , since m is the exact middle of ab . in other words , the bottom side of each of our triangles are congruent . i 'll put that as step two . great ! so far i have two pairs of sides that are congruent . the last one is easy . the third side of the left triangle is cm , and the third side of the right triangle is - well , also cm . they share the same side . of course it 's congruent to itself ! this is called the reflexive property . everything is congruent to itself . i 'll put this as step three . ta dah ! you 've just proven that all three sides of the left triangle are congruent to all three sides of the right triangle . plus , the two triangles are congruent because of the side-side-side congruence theorem for triangles . when finished with a proof , i like to do what euclid did . he marked the end of a proof with the letters qed . it 's latin for `` quod erat demonstrandum , '' which translates literally to `` what was to be proven . '' but i just think of it as `` look what i just did ! '' i can hear what you 're thinking : why should i study proofs ? one reason is that they could allow you to win any argument . abraham lincoln , one of our nation 's greatest leaders of all time used to keep a copy of euclid 's elements on his bedside table to keep his mind in shape . another reason is you can make a million dollars . you heard me . one million dollars . that 's the price that the clay mathematics institute in massachusetts is willing to pay anyone who proves one of the many unproven theories that it calls `` the millenium problems . '' a couple of these have been solved in the 90s and 2000s . but beyond money and arguments , proofs are everywhere . they underly architecture , art , computer programming , and internet security . if no one understood or could generate a proof , we could not advance these essential parts of our world . finally , we all know that the proof is in the pudding . and pudding is delicious . qed .
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let me start at the beginning . i 'll introduce you to a fellow named euclid . as in , `` here 's looking at you , clid . ''
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what is euclid famous for ?
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thallium , because it is heavier , has two different so-called oxidation states . it can react with one atom of chlorine per thallium , or say three , and the different chemistry between thallium-one and thallium-three . thallium salts are very poisonous , and there was quite a notorious case some years ago when a technician at some company , who turned out to be mad , was discovered to have been poisoning many of his colleagues with thallium and so , but it is not a widely used element , apart from a few materials that are used . there is a rather nice red material that is made of thallium , which has the rather unromantic name of krs-5 , this is mixed bromide and iodine with thallium which is used as windows for many infrared experiments . but because thallium is so poisonous , one has to be quite careful about handling .
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thallium , because it is heavier , has two different so-called oxidation states . it can react with one atom of chlorine per thallium , or say three , and the different chemistry between thallium-one and thallium-three . thallium salts are very poisonous , and there was quite a notorious case some years ago when a technician at some company , who turned out to be mad , was discovered to have been poisoning many of his colleagues with thallium and so , but it is not a widely used element , apart from a few materials that are used .
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what is the product of the reaction between thallium and steam ?
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translator : andrea mcdonough reviewer : bedirhan cinar nameste . i 'm from india , and india is one of the oldest civilizations in the world . it has contributed to the world concepts such as yoga , ayurveda , spicy chicken tikka , and vedic math . vedic math is one of the world 's easiest and simplest way to do math . we are going to combine together and do some number crunching today . so what we are going to first do is multiply by 11 . we 're going to do it together , so if you blink , you 're going to miss it . so just watch it , ok . so we 're going to do 32 times 11 , ok . so we split 3 , and we split 2 , and we add 3 and 2 and paste it on top , and we get the answer as 352 . that 's it . let 's try another sum . 45 times 11 . let 's hear it . exactly , that 's 495 . and 75 times 11 . so it gives you 7,125 , 1 gets carried over and it becomes 825 . that 's how simple it is . ok , this is the principle behind it where a is the coefficient . let 's move on . ok , now what we 're going to do is the base method . ok , this is used to multiply numbers very close to the powers of 10 , like 10 , 100 , 1,000 , and so on . so we have a sum here , say 99 times 97 . ok , now tell me , is 99 more than 100 or less than 100 ? less by how much ? so we write minus 01 . and 97 is less than 100 by how much ? so we write minus 03 . so what we 're going to do is we 're going to cross subtract and get the first part of the answer , like this . we 're going to do cross subtraction . 97 minus 01 would give us 96. and we multiply 03 times 01 vertically , and we get an answer of 03 . let 's check another sum . try and do it yourselves . we got 98 , which is , is it more than a 100 , less than 100 ? by how much ? and 97 is 3 . so we got 98 , we go crosswise , we got 98 minus 3 , or we can do 97 minus 2 , they 'll all give you the same answer . so that would give us 95 . and the second part would be 06 . so that 's our answer . ok , let 's take a bigger number . let 's try this one . here the base is 1,000 . so we got -004 , and 997 would be -003 . we go crosswise like this , and we get 996 minus 003 would give us 993 , and 004 times 003 would give us 012 . and that 's our answer . thank you . 14 times 12 . ok , here the base is 10 . ok , so is 14 more than 10 or less than 10 ? more , so we got plus 4 , and 12 , we got plus 2 . again , we apply the same rule , so we do 12 plus 4 , which gives us 16 , like this . and we multiply 2 and 4 , that gives us 8 . so now , all of us here , we 're going to do mental squaring , ok. everybody is going to participate here , and we 're going to do squares of numbers more than 100 mentally right now . so we got 101 , ok , now visualize on the board , what 's going to be on the right hand side . plus 01 , so we got that . ok , now we add plus sides , right ? yes ? no ? so we got 101 plus 01 , that would give us 102 , and , see here , like this . and 01 is getting squared , right ? so that would give us 01 , and that 's your answer . try the next one . let 's try 102 squared . let 's try , everybody . so 100 , so 102 would be 10404 . ok , now the next one , try it everybody together . i 'll give you 5 seconds . ok , let 's say it together , let 's say it together , ok. [ 10609 ] 10609 and that 's the answer . woo ! 104 squared , how much would that be ? calculate it , 5 seconds . come on , girls in the back . ok , so the answer would be 10816 . ok , let 's do the next one : 105 squared . oh , no , no , no , no , we 're going to try over , we 're going to try over , ok ? ok . i 'll give you 5 seconds , just think about it . ok , now we 're going to go , ok ? 11025 . ok , let 's going to do the next one , 106 squared . try it , come one , everybody , it 's simple and easy . [ 11236 ] ok , let 's do it one more time . 11236 . now 107 , think , hold on , do n't say anything out loud , just think mentally , 107 squared . ok , now let 's say it out loud . 11449 . and 108 squared . [ 11664 ] fantastic , give yourself a round of applause , come on ! and this is the principle behind this , where a and b are the excesses or the deficiency from the base . i 'm going to teach you in vedic math , there are 16 sutras , or word formulas , ok . they are very visual and one of them is called , `` vertically and crosswise , '' through which you can multiply any number by any number in a single line . so i 'm going to do a two-digit by a two-digit multiplication . let 's do this . so we got 31 times 12 . ok , so we 're going to apply the vertically and crosswise sutra . so we 're going to do like this : vertically , and then we 're going to go crosswise , and then we 're going to do vertical again . so , 2 times 1 gives us [ 2 ] , 2 times 3 gives us [ 6 ] , and 1 times 1 gives us [ 1 ] . 6 plus 1 , [ 7 ] . 1 times 3 gives us [ 3 ] . and that 's it , and that 's our answer . no more tedious calculations , no more going through the rough work , it 's simple in one line . i want to show you a sum again , this time with carry-overs . the same formula , all of us here can do this , ok . same formula . so let 's get started . 4 times 2 gives us [ 8 ] . ok , now we go crosswise like this , so we 're going to multiply 4 times 1 , [ 4 ] , and 3 times 2 , [ 6 ] 4 plus 6 gives us [ 10 ] . so we put down 0 , carry the 1 . and 3 times 1 gives us [ 3 ] , plus 1 , [ 4 ] . exactly , that 's our answer , 408 . ok , thank you for being such a participative audience , and we had a great time number crunching . now i want to end with a question : whether you 'd like math to be dull or boring , or fun and interesting ? the choice is yours .
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it has contributed to the world concepts such as yoga , ayurveda , spicy chicken tikka , and vedic math . vedic math is one of the world 's easiest and simplest way to do math . we are going to combine together and do some number crunching today .
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why do you enjoy math ? if you do n't , explain why .
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so praseodymium is a very interesting element . it ’ s got a myriad of uses but perhaps the most interesting one is that it has been used to enable us to get within 1/1000th of a degree of absolute zero , which is minus 273 degrees c , which is pretty darn cold . it was just used in the components which they were using in the coils to get the temperature down . it ’ s also used in welder ’ s goggles because it ’ s quite good at filtering out harmful types of light to the human eye , so you find it ’ s in the goggle and it helps the welder be able to see what he ’ s doing . it ’ s also been used in a silicate which is being used to lower the speed of light down to a mere 300 metres per second , which is still pretty fast but not very fast compared to the normal speed of light .
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it ’ s got a myriad of uses but perhaps the most interesting one is that it has been used to enable us to get within 1/1000th of a degree of absolute zero , which is minus 273 degrees c , which is pretty darn cold . it was just used in the components which they were using in the coils to get the temperature down . it ’ s also used in welder ’ s goggles because it ’ s quite good at filtering out harmful types of light to the human eye , so you find it ’ s in the goggle and it helps the welder be able to see what he ’ s doing .
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as stephen explained , it 's thanks to a praseodymium alloy that chemists can approach the lowest possible temperature . what do we call this temperature , and how many degrees celsius does it correspond to ?
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a girl i 've never met before changed my life and the life of thousands of other people . i 'm the ceo of dosomething.org . it 's one of the largest organizations in the world for young people . in fact it 's bigger than the boy scouts in the united states . and we 're not homophobic . ( laughter ) and it 's true -- the way we communicate with young people is by text , because that 's how young people communicate . so we 'll run over 200 campaigns this year , things like collecting peanut butter for food pantries , or making valentine 's day cards for senior citizens who are homebound . and we 'll text them . and we 'll have a 97 percent open rate . it 'll over-index hispanic and urban . we collected 200,000 jars of peanut butter and over 365,000 valentine 's day cards . this is big scale . ok -- ( applause ) but there 's one weird side effect . every time we send out a text message , we get back a few dozen text messages having nothing to do with peanut butter or hunger or senior citizens -- but text messages about being bullied , text messages about being addicted to pot . and the worst message we ever got said exactly this : `` he wo n't stop raping me . it 's my dad . he told me not to tell anyone . are you there ? '' we could n't believe this was happening . we could n't believe that something so horrific could happen to a human being , and that she would share it with us -- something so intimate , so personal . and we realized we had to stop triaging this and we had to build a crisis text line for these people in pain . so we launched crisis text line , very quietly , in chicago and el paso -- just a few thousand people in each market . and in four months , we were in all 295 area codes in america . just to put that into perspective , that 's zero marketing and faster growth than when facebook first launched . ( applause ) text is unbelievably private . no one hears you talking . so we spike everyday at lunch time -- kids are sitting at the lunch table and you think that she 's texting the cute boy across the hall , but she 's actually texting us about her bulimia . and we do n't get the word `` like '' or `` um '' or hyperventilating or crying . we just get facts . we get things like , `` i want to die . i have a bottle of pills on the desk in front of me . '' and so the crisis counselor says , `` how about you put those pills in the drawer while we text ? '' and they go back and forth for a while . and the crisis counselor gets the girl to give her her address , because if you 're texting a text line , you want help . so she gets the address and the counselor triggers an active rescue while they 're texting back and forth . and then it goes quiet -- 23 minutes with no response from this girl . and the next message that comes in says -- it 's the mom -- `` i had no idea , and i was in the house , we 're in an ambulance on our way to the hospital . '' as a mom that one just -- the next message comes a month later . `` i just got out of the hospital . i was diagnosed as bipolar , and i think i 'm going to be ok. '' ( applause ) i would love to tell you that that 's an unusual exchange , but we 're doing on average 2.41 active rescues a day . thirty percent of our text messages are about suicide and depression -- huge . the beautiful thing about crisis text line is that these are strangers counseling other strangers on the most intimate issues , and getting them from hot moments to cold moments . it 's exciting , and i will tell you that we have done a total of more than 6.5 million text messages in less than two years . ( applause ) but the thing that really gets me hot and sweaty about this , the thing that really gets me psyched is the data : 6.5 million messages -- that 's the volume , velocity and variety to provide a really juicy corpus . we can do things like predictive work . we can do all kinds of conclusions and learnings from that data set . so we can be better , and the world can be better . so how do we use the data to make us better ? alright , chances are someone here , someone watching this has seen a therapist or a shrink at some point in time in your life -- you do not have to raise your hand . ( laughter ) how do you know that person 's any good ? oh , they have a degree from harvard on the wall ? are you sure he did n't graduate in the bottom 10 percent ? ( laughter ) when my husband and i saw a marriage counselor , i thought she was a genius when she said , `` i 'll see you guys in two weeks -- but i need to see you next week , sir . '' ( laughter ) we have the data to know what makes a great counselor . we know that if you text the words `` numbs '' and `` sleeve , '' there 's a 99 percent match for cutting . we know that if you text in the words `` mg '' and `` rubber band , '' there 's a 99 percent match for substance abuse . and we know that if you text in `` sex , '' `` oral '' and `` mormon , '' you 're questioning if you 're gay . now that 's interesting information that a counselor could figure out but that algorithm in our hands means that an automatic pop-up says , `` 99 percent match for cutting -- try asking one of these questions '' to prompt the counselor . or `` 99 percent match for substance abuse , here are three drug clinics near the texter . '' it makes us more accurate . on the day that robin williams committed suicide , people flooded hotlines all over this country . it was sad to see an icon , a funnyman , commit suicide , and there were three hour wait times on every phone hotline in the country . we had a spike in volume also . the difference was if you text us , `` i want to die , '' or `` i want to kill myself , '' the algorithm reads that , you 're code orange , and you become number one in the queue . so we can handle severity , not chronological . ( applause ) this data is also making the world better because i 'm sitting on the world 's first map of real-time crises . think about it : those 6.5 million messages , auto-tagging through natural language processes , all of these data points -- i can tell you that the worst day of the week for eating disorders : monday . the worst time of day for substance abuse : 5am . and that montana is a beautiful place to visit but you do not want to live there , because it is the number one state for suicidal ideation . and we 've made this data public and free and open . we 've pulled all the personally identifiable information . and it 's in a place called crisistrends.org . because i want schools to be able to see that monday is the worst day for eating disorders , so that they can plan meals and guidance counselors to be there on mondays . and i want families to see that substance abuse questions spike at 5am . i want somebody to take care of those native american reservations in montana . ( applause ) data , evidence makes policy , research , journalism , policing , school boards -- everything better . i do n't think of myself as a mental health activist . i think of myself as a national health activist . i get really excited about this data , i 'm a little nerdy . yeah , that sounded too girly . i 'm nerdy . ( laughter ) i love data . and the only difference really between me and those people in hoodies down the road with their fat-funded companies , is that i 'm not inspired by helping you find chinese food at 2am in dallas , or helping you touch your wrist and get a car immediately , or swipe right and get laid . i 'm inspired -- ( laughter , applause ) i want to use tech and data to make the world a better place . i want to use it to help that girl , who texted in about being raped by her father . because the truth is we never heard from her again . and i hope that she is somewhere safe and healthy , and i hope that she sees this talk and she knows that her desperation and her courage inspired the creation of crisis text line and inspires me every freaking day . ( applause )
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and we 're not homophobic . ( laughter ) and it 's true -- the way we communicate with young people is by text , because that 's how young people communicate . so we 'll run over 200 campaigns this year , things like collecting peanut butter for food pantries , or making valentine 's day cards for senior citizens who are homebound .
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does the ability to text easily bring people closer or move them farther apart ? why do you think that ?
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translator : andrea mcdonough reviewer : jessica ruby today , we 're going to look at the world of rome through the eyes of a young girl . here she is , drawing a picture of herself in the atrium of her father 's enormous house . her name is domitia , and she is just 5 years old . she has an older brother who is fourteen , lucius domitius ahenobarbus , named after her dad . girls do n't get these long names that boys have . what is worse is that dad insists on calling all his daughters domitia . `` domitia ! '' his call to domitia drawing on the column , domitia iii . she has an older sister , domitia ii , who is 7 years old . and then there 's domitia i , who is ten . there would have been a domitia iv , but mom died trying to give birth to her three years ago . confused ? the romans were too . they could work out ancestry through the male line with the nice , tripartite names such as lucius domitius ahenobarbus . but they got in a real mess over which domitia was married to whom and was either the great aunt or the great stepmother and so on to whom when they came to write it down . domitia iii is not just drawing on the pillar , she 's also watching the action . you see , it 's early , in the time of day when all her dad 's clients and friends come to see him at home to pay their respects . lucius popidius secundus , a 17 year old , he wants to marry domitia ii within the next five to seven years , has come as well . he seems to be wooing not his future wife , but her dad . poor lucius , he does not know that domitia 's dad thinks he and his family are wealthy but still scumbags from the subura . afterall , it is the part of rome full of barbers and prostitutes . suddenly , all the men are leaving with dad . it 's the second hour and time for him to be in court with a sturdy audience of clients to applaud his rhetoric and hiss at his opponent . the house is now quieter . the men wo n't return for seven hours , not until dinner time . but what happens in the house for those seven hours ? what do domitia , domitia , and domitia do all day ? not an easy question ! everything written down by the romans that we have today was written by men . this makes constructing the lives of women difficult . however , we ca n't have a history of just roman men , so here it goes . we can begin in the atrium . there is a massive loom , on which dad 's latest wife is working on a new toga . domitia , domitia , and domitia are tasked with spinning the wool that will be used to weave this mighty garment , 30 or more feet long and elliptical in shape . romans loved the idea that their wives work wool . we know that because it 's written on the gravestones of so many roman women . unlike women in greece , roman women go out the house and move about the city . they go to the baths in the morning to avoid the men or to separate baths that are for women only . some do go in for the latest fad of the ad 70s : nude bathing with men present . where they have no place is where the men are : in the forum , in the law court , or in the senate house . their place in public is in the porticos with gardens , with sculpture , and with pathways for walking in . when domitia , domitia , and domitia want to leave the house to go somewhere , like the portico of livia , they must get ready . domitia ii and domitia iii are ready , but domitia i , who is betrothed to be married in two years to darling philatus , is n't ready . she 's not slow , she just has more to do . being betrothed means she wears the insignia of betrothal : engagement rings and all the gifts pilatus has given her - jewels , earrings , necklaces , and the pendants . she may even wear her myrtle crown . all this bling shouts , `` i 'm getting married to that 19 year old who gave me all this stuff i 'm wearing ! '' while as they wait , domitia ii and domitia iii play with their dolls that mirror the image of their sister decked out to be married . one day , these dolls will be dedicated to the household gods on the day of their wedding . okay , we 're ready . the girls step into litters carried by some burly slaves . they also have a chaperone with them and will be meeting an aunt at the porticus of livia . carried high on the shoulders of these slaves , the girls look out through the curtains to see the crowded streets below them . they traverse the city , pass the coliseum , but then turn off to climb up the hill to the porticus of livia . it was built by livia , the wife of the first emperor augustus , on the site of the house of vedius pollio . he was n't such a great guy . he once tried to feed a slave to the eels in his fish pond for simply dropping a dish . luckily , the emperor was at the dinner and tamed his temper . the litters are placed on the ground and the girls get out and arm in arm , two by two , they ascend the steps into the enclosed garden with many columns . domitia iii shot off and is drawing on a column . domitia ii joins her but seeks to read the graffiti higher up on the column . she spots a drawing of gladiators and tries to imagine seeing them fighting , something she will never be permitted to do , except from the very rear of the coliseum . from there , she will have a good view of the 50,000 spectators but will see little by way of blood and gore . if she really wanted a decent view , she could become a vestal virgin and would sit right down the front . but a career tending the sacred flame of vesta is not to everybody 's taste . domitia i has met another ten year old also decked out in the insignia of betrothal . home time . when they get there after the eighth hour , something is up . a smashed dish lies on the floor . all the slaves are being gathered together in the atrium and await the arrival of their master . dad is going to go mad . he will not hit his children , but like many other romans , he believes that slaves have to be punished . the whip lies ready for his arrival . no one knows who smashed the dish , but dad will call the undertaker to torture it out of them , if he must . the doorkeeper opens the front door to the house . a hush comes over the anxious slaves . in walks not their master but , instead , a pregnant teenager . it is the master 's eldest daughter , age 15 , who is already a veteran of marriage and child birth . guess what her name is . there is a five to ten percent chance she wo n't survive giving birth to her child , but , for now , she has come to dinner with her family . as a teenage mother , she has proved that she is a successful wife by bringing children and descendants for her husband , who will carry on his name in the future . the family head off to the dining room and are served dinner . it would seem dad has had an invite to dinner elsewhere . with dinner concluded , the girls crossed the atrium to bid farewell to their older sister who is carried home in a litter , escorted by some of dad 's bodyguards . returning to the house , the girls cross the atrium . the slaves , young and old , male and female , await the return of their owner . when he returns , he may exact vengeance , ensuring his power over the slaves is maintained through violence and terror , to which any slave could be subjected . but , for the girls , they head upstairs for the night , ready for bed .
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she has an older brother who is fourteen , lucius domitius ahenobarbus , named after her dad . girls do n't get these long names that boys have . what is worse is that dad insists on calling all his daughters domitia .
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what was significant about the names of males in ancient rome , and why were the names of females sometimes confusing ?
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you 're standing at the ready inside the goal when suddenly , you feel an intense itch on the back of your head . we 've all experienced the annoyance of an inconvenient itch , but have you ever pondered why we itch in the first place ? the average person experiences dozens of individual itches each day . they can be triggered by all sorts of things , including allergic reactions , dryness , and even some diseases . and then there are the mysterious ones that pop up for no reason at all , or just from talking about itching . you 're scratching your head right now , are n't you ? anyhow , let 's take one of the most common sources : bug bites . when a mosquito bites you , it releases a compound into your body called an anticoagulant that prevents your blood from clotting . that compound , which we 're mildly allergic to , triggers the release of histamine , a chemical that makes our capillaries swell . this enables increased blood flow , which helpfully accelerates the body 's immune response to this perceived threat . that explains the swelling , and it 's the same reason pollen can make your eyes puff up . histamine also activates the nerves involved in itching , which is why bug bites make you scratch . but the itchy sensation itself is n't yet fully understood . in fact , much of what we do know comes from studying the mechanics of itching in mice . researchers have discovered that itch signals in their skin are transmitted via a subclass of the nerves that are associated with pain . these dedicated nerves produce a molecule called natriuretic polypetide b , which triggers a signal that 's carried up the spinal cord to the brain , where it creates the feeling of an itch . when we scratch , the action of our fingernails on the skin causes a low level pain signal that overrides the itching sensation . it 's almost like a distraction , which creates the sensation of relief . but is there actually an evolutionary purpose to the itch , or is it simply there to annoy us ? the leading theory is that our skin has evolved to be acutely aware of touch so that we 're equipped to deal with risks from the outside world . think about it . our automatic scratching response would dislodge anything harmful that 's potentially lurking on our skin , like a harmful sting , a biting insect , or the tendrils of a poisonous plant . this might explain why we do n't feel itching inside our bodies , like in our intestines , which is safe from these external threats , though imagine how maddening that would be . in some people , glitches in the pathways responsible for all of this can cause excessive itching that can actually harm their health . one extreme example is a psychological condition called delusory parasitosis where people believe their bodies are infested with mites or fleas scurrying over and under their skin , making them itch incessantly . another phenomenon called phantom itching can occur in patients who 've had amputations . because this injury has so severely damaged the nervous system , it confuses the body 's normal nerve signaling and creates sensations in limbs that are no longer there . doctors are now finding ways to treat these itching anomalies . in amputees , mirrors are used to reflect the remaining limb , which the patient scratches . that creates an illusion that tricks the brain into thinking the imaginary itch has been satisfied . oddly enough , that actually works . researchers are also searching for the genes involved in itching and developing treatments to try and block the pathway of an itch in extreme cases . if having an unscratchable itch feels like your own personal hell , dante agreed . the italian poet wrote about a section of hell where people were punished by being left in pits to itch for all eternity .
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in fact , much of what we do know comes from studying the mechanics of itching in mice . researchers have discovered that itch signals in their skin are transmitted via a subclass of the nerves that are associated with pain . these dedicated nerves produce a molecule called natriuretic polypetide b , which triggers a signal that 's carried up the spinal cord to the brain , where it creates the feeling of an itch .
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what other sensations are the nerve cells that transmit itch signals associated with ?
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now and then i think of what i learned in high school like ap bio and british literature is that igneous or metamorphic ? i do n't need to write a nine bic and i 'll admit i do n't know shit about millard fillmore why did i have to learn this stuff ? it is never common -- had they never used it for nothing ? why did we have to read the scarlet letter ? puritans are boring even when one is a slut there 's actually one thing i still know eli whitney he invented the cotton gin definitely do not need that , though now it 's just a study that i used to know now it 's just a study that i used to know now and then i think of all the things i 've taught you every handout with a far side cartoon apropo you do n't want to live that way forgetting every word i say you said you 'd never let it go i guess mnemonic devices just were n't enough for you though you really freaking pissed me off i worked so hard to teach you something , now you do n't know nothing what does the comment symbolize ? or anything beyond the first three digits of pi and what about sohcahtoa or asexual reproduction of a protozoa i guess you did n't need that though now it 's just a study that you used to know a study i used to know now it 's just a study that you used to know i used to know a study
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now and then i think of what i learned in high school like ap bio and british literature is that igneous or metamorphic ? i do n't need to write a nine bic and i 'll admit i do n't know shit about millard fillmore why did i have to learn this stuff ?
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history/english question : over the past 100 years , who has been making the decisions about what material and activities to include in high school curriculum ?
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humans know the surprising prick of a needle , the searing pain of a stubbed toe , and the throbbing of a toothache . we can identify many types of pain and have multiple ways of treating it . but what about other species ? how do the animals all around us experience pain ? it 's important that we find out . we keep animals as pets , they enrich our environment , we farm many species for food , and we use them in experiments to advance science and human health . animals are clearly important to us , so it 's equally important that we avoid causing them unnecessary pain . for animals that are similar to us , like mammals , it 's often obvious when they 're hurting . but there 's a lot that is n't obvious , like whether pain relievers that work on us also help them . and the more different an animal is from us , the harder it is to understand their experience . how do you tell whether a shrimp is in pain ? a snake ? a snail ? in vertebrates , including humans , pain can be split into two distinct processes . in first , nerves and the skin sense something harmful and communicate that information to the spinal cord . there , motor neurons activate movements that make us rapidly jerk away from the threat . this is the physical recognition of harm called nociception , and nearly all animals , even those with very simple nervous systems , experience it . without this ability , animals would be unable to avoid harm and their survival would be threatened . the second part is the conscious recognition of harm . in humans , this occurs when the sensory neurons in our skin make a second round of connections via the spinal cord to the brain . there , millions of neurons in multiple regions create the sensations of pain . for us , this is a very complex experience associated with emotions like fear , panic , and stress , which we can communicate to others . but it 's harder to know exactly how animals experience this part of the process because most them ca n't show us what they feel . however , we get clues from observing how animals behave . wild , hurt animals are known to nurse their wounds , make noises to show their distress , and become reclusive . in the lab , scientists have discovered that animals like chickens and rats will self-administer pain-reducing drugs if they 're hurting . animals also avoid situations where they 've been hurt before , which suggests awareness of threats . we 've reached the point that research has made us so sure that vertebrates recognize pain that it 's illegal in many countries to needlessly harm these animals . but what about other types of animals like invertebrates ? these animals are n't legally protected , partly because their behaviors are harder to read . we can make good guesses about some of them , like oysters , worms , and jellyfish . these are examples of animals that either lack a brain or have a very simple one . so an oyster may recoil when squirted with lemon juice , for instance , because of nociception . but with such a simple nervous system , it 's unlikely to experience the conscious part of pain . other invertebrate animals are more complicated , though , like the octopus , which has a sophisticated brain and is thought to be one of the most intelligent invertebrate animals . yet , in many countries , people continue the practice of eating live octopus . we also boil live crawfish , shrimp , and crabs even though we do n't really know how they 're affected either . this poses an ethical problem because we may be causing these animals unnecessary suffering . scientific experimentation , though controversial , gives us some clues . tests on hermit crabs show that they 'll leave an undesirable shell if they 're zapped with electricity but stay if it 's a good shell . and octopi that may originally curl up an injured arm to protect it will risk using it to catch prey . that suggests that these animals make value judgements around sensory input instead of just reacting reflexively to harm . meanwhile , crabs have been known to repeatedly rub a spot on their bodies where they 've received an electric shock . and even sea slugs flinch when they know they 're about to receive a noxious stimulus . that means they have some memory of physical sensations . we still have a lot to learn about animal pain . as our knowledge grows , it may one day allow us to live in a world where we do n't cause pain needlessly .
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that suggests that these animals make value judgements around sensory input instead of just reacting reflexively to harm . meanwhile , crabs have been known to repeatedly rub a spot on their bodies where they 've received an electric shock . and even sea slugs flinch when they know they 're about to receive a noxious stimulus . that means they have some memory of physical sensations .
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crabs have been shown to respond to noxious stimuli by :
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translator : andrea mcdonough reviewer : bedirhan cinar how come some insects are able to walk on the surface of a pond , but you quickly sink to the bottom when you try to walk on water ? and why do lakes freeze from the top down in winter ? in a word , the answer to all these questions is polarity . water is a simple molecule made up of one oxygen atom and two hydrogen atoms , but it is essential to life . in fact , water makes up approximately 60 % of the adult human being 's body weight . the polarity within those water molecules gives this common substance the properties that make it unique and life-sustaining . polarity refers to the unequal sharing of electrons within a molecule . for water , the bonding between the oxygen atom and two hydrogen atoms within a single water molecule is like a tug-of-war between a big , strong football player and a cute little toddler . oxygen is a larger atom , with more protons in its nucleus than hydrogen . these positive charges are like a person 's physical strength . they 're able to attract the negatively charged electrons in the bond , just like a strong individual is able to overpower a weaker individual in a tug of war . so , oxygen is able to attract more than its fair share of electrons . because hydrogen is smaller and has less strength , or fewer protons , it loses the tug of war and attracts fewer than its fair share of electrons . so , the oxygen in water behaves as though it 's negative , and the hydrogens behave as though they 're positive . the bonds within a single water molecule are called polar covalent bonds . covalent means that the electrons are shared . but , as we just learned , polar means that these electrons are not shared equally . in water , the oxygen acts negative and the hydrogens act positive . since negative and positive attract , that oxygen is attracted to the hydrogen atoms in neighboring water molecules . a special type of bond forms between water molecules , known as a hydrogen bond . hydrogen bonds do n't just happen in water either . they can form between a water molecule and different substances that are polar or ionic . water 's ability to stick to itself is called cohesion , while water 's ability to stick to other substances is called adhesion . now , think back to the initial questions . first , why are some insects able to walk on water ? surface tension due to hydrogen bonding creates a thin film on the surface of water that gives enough resistance for super-light insects to walk on . you ca n't walk on it because the hydrogen bonds are n't strong enough to hold you up . why does ice float on top of liquid water ? for most other substances , the solid state is more dense than the liquid state , but that is not the case for water ! hydrogen bonds keep water molecules farther apart in frozen water than in liquid water . the farther apart the molecules are , the less dense that solid is . so ice is about 9 % less dense than water , which means it floats on the top . that 's why lakes freeze from the top down and aquatic life is able to survive through a cold winter every year . it is the polarity of the water molecule and the resulting hydrogen bonding that account for water 's unique properties . so , the reason that water is so special , from inside your cells to the world 's oceans , is simply because it is a polar molecule .
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for most other substances , the solid state is more dense than the liquid state , but that is not the case for water ! hydrogen bonds keep water molecules farther apart in frozen water than in liquid water . the farther apart the molecules are , the less dense that solid is .
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as we know , a plant ’ s roots absorb water . however , water is needed by all parts of the plant . based on what we learned about the polarity of water , explain how water is transported through tiny tubes from the roots to the leaves within a plant . ( video hint : think about how blood moves around the body . )
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currently i think there are eight intelligences that i ’ m very confident about and a few more that i ’ ve bene thinking about . i ’ ll share that with our audience . the first two intelligences are the ones which iq tests and other kind of standardized tests valorize and as long as we know there are only two out of eight it ’ s perfectly fine to look at them . linguistic intelligence is how well you ’ re able to use language . it ’ s a kind of skill that poets have , other kinds of writers , journalists tend to have linguistic intelligence , orators . the second intelligence is logical mathematical intelligence . as the name implies logicians , mathematicians , scientists have that kind of intelligence . they ’ re able to do mathematical proofs . they ’ re able to do scientific reasoning and experimentation . and it ’ s great to have language and logical intelligence because most tests really focus on that . and if you do well in those tests as long as you stay in school you think you ’ re smart . but if you ever walk out into broadway or the highway or into the woods or into a farm you then find out that other intelligences are at least this important . so the third intelligence is musical intelligence and that ’ s the capacity to appreciate different kinds of musics , to produce the music by voice or by an instrument or to conduct music . and people say well music is a talent . it ’ s not an intelligence . and i say well why if you ’ re good with words is that an intelligence but if you ’ re good with tones and rhythms and timbres nobody ’ s ever given me a good answer which is why it makes sense to talk about musical intelligence . and at certain cultures over history musical intelligence has been very important . the fourth intelligence is spatial intelligence . that ’ s the intelligence which allows us to handle and work in space that ’ s close by . a chess player would have spatial intelligence . a surgeon would have spatial intelligence . but there ’ s another variety of spatial intelligence which we use for a much broader navigation . that ’ s what an airplane pilot or a sea captain would have . how do you find your way around large territory and large space . similarly with the fifth intelligence bodily kinesthetic intelligence it comes in two flavors . one flavor is the ability to use your whole body to solve problems or to make things . and athletes and dancers would have that kind of bodily kinesthetic intelligence . but another variety is being able to use your hands or other parts of your body to solve problems or make things . a craft person would have bodily kinesthetic intelligence even if they weren ’ t particularly a good athlete or dancer . the sixth intelligence and seventh intelligence have to do with human beings . interpersonal intelligence is how you understand other people , how you motivate them , how you lead them , how you work with them , how you cooperate with them . anybody at any workplace with other people needs interpersonal intelligence . leaders hopefully have a lot of interpersonal intelligence . but any intelligence can be used in a pernicious way so the salesman that sells you something you don ’ t want for a price you don ’ t want to pay , he or she has got interpersonal intelligence . it ’ s just not being used in a way that we might prefer . the seventh kind of intelligence is difficult to assess but it ’ s very important . it ’ s intrapersonal intelligence . it ’ s the understanding yourself . if we go back a way in history and prehistory knowledge of yourself probably wasn ’ t that important because people did what their parents or grandparents did whether they were hunters or fisherman or craftspeople . but nowadays especially in developed society people lead their own lives . we follow our own careers . we often switch careers . we don ’ t necessarily live at home as we get older . and if you don ’ t have a good understanding of yourself you are in big trouble . so that ’ s intrapersonal intelligence . the eighth intelligence which i added some years ago is the naturalist intelligence . and that ’ s the capacity to make important relevant discriminations in the world of nature between one plant and another , between one animal and another . it ’ s the intelligence of the naturalist , the intelligence of charles darwin . i missed it the first go around when i wrote about it but i tried to atone by adding it to my list . and by the way you might say well but nature isn ’ t so important anymore . but in fact everything we do in the commercial world uses our naturalist intelligence . why do i buy this jacket rather than another one ? this sweater rather than another one ? one hair style rather than another ? those all make just the naturalist intelligence because the brain is very adaptive . and when an old use of a brain center no longer is relevant it gets hijacked for something new . so we ’ re all using our naturalist intelligence even if we never walk out into the woods or into the savannah of east asia . the two other intelligences which i ’ m interested in , one of them is called the teaching or pedagogical intelligence . the intelligence which allows us to be able to teach successfully to other people . now you could have two people who have exactly the same expertise and knowledge in the field but one is a very good teacher and the other isn ’ t . that probably doesn ’ t surprise individuals so much . but what got me fascinated was as young as two or three kids already know how to teach . now what does that mean ? you show a child how to do something let ’ s say a three or four year old and then you ask the child to explain it to an older person or to a younger person . and even the three or four year old will explain it very differently to a young person , will go through details , point things and speak slowly . and with an older person it would be much more elliptical and say well you do this and that and then you can figure it out . so that shows as young as three let ’ s say we already have teaching intelligence . the other one is one which i think is going to be difficult to prove to a skeptic but i call it existential intelligence . and existential intelligence is the intelligence of big questions . philosophical questions , artistic questions . what does it mean to love ? why do we die ? what ’ s going to be in the future ? my pet bird might have more musical intelligence . the rats who are scurrying around the floor might have more spatial intelligence . but no other animals have existential intelligence . part of the human condition is to think about questions of existence . and i like to say every five year old has existential intelligence because five year old are always asking why this , why that . but the difference between a five year old and a philosopher is the five year old doesn ’ t pay too much attention to the answer whereas philosophers and other people who develop existential intelligence are really very interested in how we attack questions like that . so again where there ’ s eight intelligences or ten or twelve is less important to me than having broken the monopoly of a single intelligence which sort of labels you for all time . i think if we lived forever we could probably develop each intelligence to a very high degree . but life is very short and if you devote too much attention to one intelligence you ’ re not going to have much time to work on other kinds of intelligences . and so the big question is should you play to strength or should you bolster weakness ? and that ’ s a value judgment . scientists can not give you an answer to that . if , for example , you want to be a jack of all trades and be very well rounded then probably you ’ re going to want to nurture the intelligences which aren ’ t that strong . if on the other hand you ’ re dead set on really coming to the top of some particular heap then you ’ re probably going to find the intelligences that you ’ re strongest at and really push those . and , you know , if a parent came to me and said well should we supplement or should we accentuate i would say well tell me what you would like your child to do . or better let the child tell you what he or she wants to do rather than say well science says you should do one or the other . i think it ’ s a question of values , not of science . some people think there ’ s such a thing as humor intelligence . but , in fact , i don ’ t . i think humor intelligence is simply the operation of a logical intelligence in some realm like human nature or physical nature or the workplace . and what happens is in humor there ’ s a certain expectation and you flip that expectation so it ’ s logic but it ’ s logic that ’ s played out in different kinds of ways . people had mentioned there ’ s such a thing as a cooking intelligence , a humor intelligence and a sexual intelligence . and i quipped well that can ’ t be intelligences because i don ’ t have any of them .
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and if you don ’ t have a good understanding of yourself you are in big trouble . so that ’ s intrapersonal intelligence . the eighth intelligence which i added some years ago is the naturalist intelligence . and that ’ s the capacity to make important relevant discriminations in the world of nature between one plant and another , between one animal and another .
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describe what naturalist intelligence is .
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translator : andrea mcdonough reviewer : jessica ruby today , we 're going to look at the world of rome through the eyes of a young girl . here she is , drawing a picture of herself in the atrium of her father 's enormous house . her name is domitia , and she is just 5 years old . she has an older brother who is fourteen , lucius domitius ahenobarbus , named after her dad . girls do n't get these long names that boys have . what is worse is that dad insists on calling all his daughters domitia . `` domitia ! '' his call to domitia drawing on the column , domitia iii . she has an older sister , domitia ii , who is 7 years old . and then there 's domitia i , who is ten . there would have been a domitia iv , but mom died trying to give birth to her three years ago . confused ? the romans were too . they could work out ancestry through the male line with the nice , tripartite names such as lucius domitius ahenobarbus . but they got in a real mess over which domitia was married to whom and was either the great aunt or the great stepmother and so on to whom when they came to write it down . domitia iii is not just drawing on the pillar , she 's also watching the action . you see , it 's early , in the time of day when all her dad 's clients and friends come to see him at home to pay their respects . lucius popidius secundus , a 17 year old , he wants to marry domitia ii within the next five to seven years , has come as well . he seems to be wooing not his future wife , but her dad . poor lucius , he does not know that domitia 's dad thinks he and his family are wealthy but still scumbags from the subura . afterall , it is the part of rome full of barbers and prostitutes . suddenly , all the men are leaving with dad . it 's the second hour and time for him to be in court with a sturdy audience of clients to applaud his rhetoric and hiss at his opponent . the house is now quieter . the men wo n't return for seven hours , not until dinner time . but what happens in the house for those seven hours ? what do domitia , domitia , and domitia do all day ? not an easy question ! everything written down by the romans that we have today was written by men . this makes constructing the lives of women difficult . however , we ca n't have a history of just roman men , so here it goes . we can begin in the atrium . there is a massive loom , on which dad 's latest wife is working on a new toga . domitia , domitia , and domitia are tasked with spinning the wool that will be used to weave this mighty garment , 30 or more feet long and elliptical in shape . romans loved the idea that their wives work wool . we know that because it 's written on the gravestones of so many roman women . unlike women in greece , roman women go out the house and move about the city . they go to the baths in the morning to avoid the men or to separate baths that are for women only . some do go in for the latest fad of the ad 70s : nude bathing with men present . where they have no place is where the men are : in the forum , in the law court , or in the senate house . their place in public is in the porticos with gardens , with sculpture , and with pathways for walking in . when domitia , domitia , and domitia want to leave the house to go somewhere , like the portico of livia , they must get ready . domitia ii and domitia iii are ready , but domitia i , who is betrothed to be married in two years to darling philatus , is n't ready . she 's not slow , she just has more to do . being betrothed means she wears the insignia of betrothal : engagement rings and all the gifts pilatus has given her - jewels , earrings , necklaces , and the pendants . she may even wear her myrtle crown . all this bling shouts , `` i 'm getting married to that 19 year old who gave me all this stuff i 'm wearing ! '' while as they wait , domitia ii and domitia iii play with their dolls that mirror the image of their sister decked out to be married . one day , these dolls will be dedicated to the household gods on the day of their wedding . okay , we 're ready . the girls step into litters carried by some burly slaves . they also have a chaperone with them and will be meeting an aunt at the porticus of livia . carried high on the shoulders of these slaves , the girls look out through the curtains to see the crowded streets below them . they traverse the city , pass the coliseum , but then turn off to climb up the hill to the porticus of livia . it was built by livia , the wife of the first emperor augustus , on the site of the house of vedius pollio . he was n't such a great guy . he once tried to feed a slave to the eels in his fish pond for simply dropping a dish . luckily , the emperor was at the dinner and tamed his temper . the litters are placed on the ground and the girls get out and arm in arm , two by two , they ascend the steps into the enclosed garden with many columns . domitia iii shot off and is drawing on a column . domitia ii joins her but seeks to read the graffiti higher up on the column . she spots a drawing of gladiators and tries to imagine seeing them fighting , something she will never be permitted to do , except from the very rear of the coliseum . from there , she will have a good view of the 50,000 spectators but will see little by way of blood and gore . if she really wanted a decent view , she could become a vestal virgin and would sit right down the front . but a career tending the sacred flame of vesta is not to everybody 's taste . domitia i has met another ten year old also decked out in the insignia of betrothal . home time . when they get there after the eighth hour , something is up . a smashed dish lies on the floor . all the slaves are being gathered together in the atrium and await the arrival of their master . dad is going to go mad . he will not hit his children , but like many other romans , he believes that slaves have to be punished . the whip lies ready for his arrival . no one knows who smashed the dish , but dad will call the undertaker to torture it out of them , if he must . the doorkeeper opens the front door to the house . a hush comes over the anxious slaves . in walks not their master but , instead , a pregnant teenager . it is the master 's eldest daughter , age 15 , who is already a veteran of marriage and child birth . guess what her name is . there is a five to ten percent chance she wo n't survive giving birth to her child , but , for now , she has come to dinner with her family . as a teenage mother , she has proved that she is a successful wife by bringing children and descendants for her husband , who will carry on his name in the future . the family head off to the dining room and are served dinner . it would seem dad has had an invite to dinner elsewhere . with dinner concluded , the girls crossed the atrium to bid farewell to their older sister who is carried home in a litter , escorted by some of dad 's bodyguards . returning to the house , the girls cross the atrium . the slaves , young and old , male and female , await the return of their owner . when he returns , he may exact vengeance , ensuring his power over the slaves is maintained through violence and terror , to which any slave could be subjected . but , for the girls , they head upstairs for the night , ready for bed .
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he seems to be wooing not his future wife , but her dad . poor lucius , he does not know that domitia 's dad thinks he and his family are wealthy but still scumbags from the subura . afterall , it is the part of rome full of barbers and prostitutes . suddenly , all the men are leaving with dad .
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did you know that slaves were a part of the lives of wealthy romans ? in a few sentences , explain how the slave industry functioned in ancient rome .
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hi , everybody ! i am a comparative anatomist . a comparative anatomist is someone who studies the structure of the body of lots of different animals . and my favorite animals are whales . i like to study whales because they 're so interesting . they 've adapted to a unique environment of living in the water . and what i 'm going to tell you about is how whales make sounds by basically farting with their face . you know that they do this farting thing with their blowhole ; they blow out air like that , but they also use air in lots of other ways . they use it for sound production , which is what i 'll focus on , but i also study other things they do with air , like keep it out of their bloodstream so they do n't get bubbles , which is what happens to human scuba divers when they get decompression sickness . but i 'd like to start with the story of how these animals make these farting noises , and that story begins with understanding how hard it is to look at whales , because they live underwater and they 're really big , so they 're hard animals to study . and in this picture -- you see that animal in the middle ? that 's a baby whale and it 's already the size of a bus ! when you look at whales , start with the top of their head because their nose is on the top of their head , kind of like a built-in snorkel . they breathe through that because they 're mammals and mammals breathe air . their nose can be opened and closed , as if you were to pinch it like this . you can see it 's open in the bottom frame , where the red arrows are . but not all whales have two nostrils . whales include the groups of dolphins and porpoises , and dolphins and porpoises , the small whales , have only one nostril on the top of their head , and they open and close that nostril by taking what is essentially an upper lip , like this , and turning it back over their nose , like this . that 's how they open and close their nose . so when they make sounds , what they 're basically doing is a raspberry , ( makes raspberry sound ) which is kind of like a fart , right ? or up in new york , we call it a bronx cheer . and the way they do that is by taking that big , fatty structure of a big fat lip , which , as you can see here in this picture , which is a cut through the middle of a dolphin 's head , that big fat lip is that big yellow portion there , and they roll it back and forth over the top of their nose so that they vibrate it , kind of like when you let the air out of a balloon and it makes that weird vibration sound . so this is what it sounds like when they make their noise : ( vibration noise ) hear it ? he 'll do it again when he faces the camera . ( vibration noise ) sounds like it 's farting underwater . what that dolphin is actually doing , though , is echolocation , which is making these series of pulses , and it uses it like a bat uses sonar . well , a bat uses radar , but when it 's underwater it 's sonar , so this animal is using sonar to see its world in sound . trying to understand how this works , you have to look at it as if you were looking at the amplifier speakers of a sound system . the small-toothed whales are basically the `` tweeters , '' and the sound is coming from that little nose that 's moving back and forth and coming out of their forehead . but the big whales are kind of like the `` woofers , '' the big speakers that you have in an amplifier system . and what 's happening is their sound is coming out of the throat . so if you tried to make sound like a whale -- make a sound right now , and go , `` ahhhhhh . '' ok , now put your hand on your throat , on your adam 's apple . you feel that vibration right there ? that is lost energy for you , because that 's not how you communicate to everybody . you do it out of the mouth . but if you open your mouth underwater , no one will hear you . you have to be able to take this energy and amplify it through the water . that 's what whales do . and when you hear their sound -- ( squeaking sound ) it 's kind of like when you squeak the air out of a balloon . so they get a lot of squeaky noises , but they also have this sound : ( vibrating sound ) it sounds like it 's farting , does n't it ? it 's like it 's got this giant whoopee cushion in its throat . so , how do you know that 's what a whale is doing ? well , we study whales that come to us from strandings . these are animals that die on the beach . small whales like dolphins and porpoises are easy ; we can take them to the lab . but the big whales -- we 've got to bring the lab to the whale . and this is what that looks like . i 'm the one in the middle with the red hat . i 'm not a very tall person , so you can see how big this whale was compared to me . the whale is 65 feet long . and my scalpel is this little tool on the side here . it basically looks like a hockey stick with a blade on the end of it . and doing a dissection of a whale is a very difficult process . you literally have to get into your work . it 's kind of like a giant bloody construction zone . you 're wearing a hard hat , you 're working with heavy machinery . in this case , by the way , that 's just the voice box of a blue whale . just the voice box . i 'm only five feet tall -- you can see it 's like 12 feet long . how do we know what 's going on ? well , we look at the voice box , or larynx , and we see -- this is from a baby whale so it 's much smaller . you see this little u-shaped thing i 've outlined in blue . that 's the part that 's vibrating . it 's kind of like our vocal folds . when i put my hand in there , where that blue sleeve is , you can see there 's a sack underneath it . that 's the whoopee cushion . that 's the air bubble or the balloon . so what these animals are doing -- and you can see , there 's this big black balloon in the throat , where the digestive tract , which is in blue , meets the breathing tract , which is in light blue , and right in the middle is that black sack . these animals are using that sack to make these sounds . and so they vibrate that and send it out . small-toothed whales also have air sacks ; they 're all over their heads , so it 's like they 're airheads . they use this to capture as much air as they can to take down with them when they 're diving , because when you dive , pressures increase , and that decreases the volume of air you have available . but more importantly , having that sack allows them to recycle the air that they 're using , because air is a precious commodity . you do n't want to have to go back up to the surface to get more . so when you make a sound underwater , if you 're a whale -- let 's hear you start making a sound , go `` ahhhh . '' but whales keep their mouths closed , so go `` ahhhmm . '' ( audience makes noise ) you 're all humming , right ? but whales keep their nose closed and go , `` mmmm . '' ( makes noise ) what happened ? you ca n't make the sound anymore once you close your nose because you 've pressurized the system . whales , by having air sacks , keep themselves from pressurizing the system , which means the air continues to flow , and so if you had a bag on the end of your nose , you 'd be able to make air continue to flow . so i hope you 've enjoyed that . that 's what a comparative anatomist does for a living . we study the structure of these animals . we try to mimic it ; we apply it back to the human situation , maybe making new technologies for protective devices or maybe even making new treatments for medicines for people 's diseases who mimic these weird environments . so i hope you enjoyed that . thank you . ( applause )
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you can see it 's open in the bottom frame , where the red arrows are . but not all whales have two nostrils . whales include the groups of dolphins and porpoises , and dolphins and porpoises , the small whales , have only one nostril on the top of their head , and they open and close that nostril by taking what is essentially an upper lip , like this , and turning it back over their nose , like this .
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all whales derive from a common land-dwelling ancestor , but diverged over time along two different evolutionary paths , resulting in two different groups : toothed whales ( including dolphins , porpoises , and sperm whales ) and baleen whales ( including fin , blue , and humpback whales ) . what are some of the differences in their anatomy , and how do these differences affect sound production ?
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we live in a three-dimensional world where everything has length , width , and height . but what if our world were two-dimensional ? we would be squashed down to occupy a single plane of existence , geometrically speaking , of course . and what would that world look and feel like ? this is the premise of edwin abbott 's 1884 novella , flatland . flatland is a fun , mathematical thought experiment that follows the trials and tribulations of a square exposed to the third dimension . but what is a dimension , anyway ? for our purposes , a dimension is a direction , which we can picture as a line . for our direction to be a dimension , it has to be at right angles to all other dimensions . so , a one-dimensional space is just a line . a two-dimensional space is defined by two perpendicular lines , which describe a flat plane like a piece of paper . and a three-dimensional space adds a third perpendicular line , which gives us height and the world we 're familiar with . so , what about four dimensions ? and five ? and eleven ? where do we put these new perpendicular lines ? this is where flatland can help us . let 's look at our square protagonist 's world . flatland is populated by geometric shapes , ranging from isosceles trianges to equilateral triangles to squares , pentagons , hexagons , all the way up to circles . these shapes are all scurrying around a flat world , living their flat lives . they have a single eye on the front of their faces , and let 's see what the world looks like from their perspective . what they see is essentially one dimension , a line . but in abbott 's flatland , closer objects are brighter , and that 's how they see depth . so a triangle looks different from a square , looks different a circle , and so on . their brains can not comprehend the third dimension . in fact , they vehemently deny its existence because it 's simply not part of their world or experience . but all they need , as it turns out , is a little boost . one day a sphere shows up in flatland to visit our square hero . here 's what it looks like when the sphere passes through flatland from the square 's perspective , and this blows his little square mind . then the sphere lifts the square into the third dimension , the height direction where no flatlander has gone before and shows him his world . from up here , the square can see everything : the shapes of buildings , all the precious gems hidden in the earth , and even the insides of his friends , which is probably pretty awkward . once the hapless square comes to terms with the third dimension , he begs his host to help him visit the fourth and higher dimensions , but the sphere bristles at the mere suggestion of dimensions higher than three and exiles the square back to flatland . now , the sphere 's indignation is understandable . a fourth dimension is very difficult to reconcile with our experience of the world . short of being lifted into the fourth dimension by visiting hypercube , we ca n't experience it , but we can get close . you 'll recall that when the sphere first visited the second dimension , he looked like a series of circles that started as a point when he touched flatland , grew bigger until he was halfway through , and then shrank smaller again . we can think of this visit as a series of 2d cross-sections of a 3d object . well , we can do the same thing in the third dimension with a four-dimensional object . let 's say that a hypersphere is the 4d equivalent of a 3d sphere . when the 4d object passes through the third dimension , it 'll look something like this . let 's look at one more way of representing a four-dimensional object . let 's say we have a point , a zero-dimensional shape . now we extend it out one inch and we have a one-dimensional line segment . extend the whole line segment by an inch , and we get a 2d square . take the whole square and extend it out one inch , and we get a 3d cube . you can see where we 're going with this . take the whole cube and extend it out one inch , this time perpendicular to all three existing directions , and we get a 4d hypercube , also called a tesseract . for all we know , there could be four-dimensional lifeforms somewhere out there , occasionally poking their heads into our bustling 3d world and wondering what all the fuss is about . in fact , there could be whole other four-dimensional worlds beyond our detection , hidden from us forever by the nature of our perception . does n't that blow your little spherical mind ?
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now , the sphere 's indignation is understandable . a fourth dimension is very difficult to reconcile with our experience of the world . short of being lifted into the fourth dimension by visiting hypercube , we ca n't experience it , but we can get close .
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pretend you are visited by a hypersphere who lifts you out of the third dimension into the fourth . what might you experience ? try drawing something you see on your journey .
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every chicken was once an egg , every oak tree an acorn , every frog a tadpole . the patch of mold on that old piece of bread in the back of your fridge , not so long ago that was one , solitary cell . even you were once but a gleam in your parents ' eyes . all these organisms share the same basic goal : to perpetuate their own existence . all lifeforms that we 've discovered so far stay alive by using basically the same rules , materials , and machinery . imagine a factory full of robots . these robots have two missions : one , keep the factory running , and two , when the time is right , set up an entirely new factory . to do those things , they need assembly instructions , raw materials , plenty of energy , a few rules about when to work normally , when to work quickly , or when to stop , and some exchange currencies because even robots need to get paid . each factory has a high security office with blueprints for all the possible factory configurations and complete sets of instructions to make all the different types of robots a factory could ever need . special robots photocopy these instructions and send them off to help make the building blocks of more robots . their colleagues assemble those parts into still more robots , which are transported to the right location in the factory and given the tools they need to start working . every robot draws energy from the central power plant , a giant furnace that can burn regular fuel but also scrap materials if not enough regular fuel is available . certain zones in the factory have harsher working conditions , so these areas are walled off . but the robots inside can at least communicate with the rest of the factory through specialized portals embedded directly into the walls . and as you 've probably figured out , what we 're describing here is a cell . the high security office is the nucleus . it stores the blueprints and instructions as deoxyribonucleic acid , or dna . the photocopied instructions are rna . the robots themselves are mostly proteins built from amino acids , but they 'll often use special tools that are , or are derived from , vitamins and minerals . the walls between factory zones and around the factory itself are mostly made up of lipids , a.k.a . fats . in most organisms , the primary fuel source are sugars , but in a pinch , fats and proteins can be broken down and burned in the furnace as well . the portals are membrane proteins which allow very specific materials and information to pass through the walls at the right times . many interactions between robot proteins require some kind of push , think robot minimum wage . a few small but crucial forms of money are transferred between proteins to provide this push . electrons , protons , oxygen , and phosphate groups are the main chemical currencies , and they 're kept in small molecular wallets or larger tote bags to keep them safe . this is biochemistry , the study of how every part of the factory interacts to keep your life running smoothly in the face of extreme challenges . maybe there 's too much fuel ; your body will store the excess as glycogen or fat . maybe there 's not enough ; your body will use up those energy reserves . maybe a virus or bacteria tries to invade ; your body will mobilize the immune system . maybe you touched something hot or sharp ; your nerves will let you know so you can stop . maybe it 's time to create a new cell or a new person . amazingly , oak trees , chickens , frogs , and , yes , even you share so many of the same basic robot and factory designs that biochemists can learn a lot about all of them all at the same time .
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to do those things , they need assembly instructions , raw materials , plenty of energy , a few rules about when to work normally , when to work quickly , or when to stop , and some exchange currencies because even robots need to get paid . each factory has a high security office with blueprints for all the possible factory configurations and complete sets of instructions to make all the different types of robots a factory could ever need . special robots photocopy these instructions and send them off to help make the building blocks of more robots .
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barriers separate different zones of the factory , and membranes separate different parts of a cell . what do these barriers contribute to the operation ?
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most people recognize his name and know that he is famous for having said something , but considering the long-lasting impact his teachings have had on the world , very few people know who confucius really was , what he really said , and why . amid the chaos of 6th century bce china , where warring states fought endlessly among themselves for supremacy , and rulers were frequently assassinated , sometimes by their own relatives , confucius exemplified benevolence and integrity , and through his teaching , became one of china 's greatest philosophers . born to a nobleman but raised in poverty from a very young age following the untimely death of his father , confucius developed what would become a lifelong sympathy for the suffering of the common people . barely supporting his mother and disabled brother as a herder and account keeper at a granary , and with other odd jobs , it was only with the help of a wealthy friend that confucius was able to study at the royal archives , where his world view would be formed . though the ancient texts there were regarded by some as irrelevant relics of the past , confucius was inspired by them . through study and reflection , confucius came to believe that human character is formed in the family and by education in ritual , literature , and history . a person cultivated in this way works to help others , guiding them by moral inspiration rather than brute force . to put his philosophy into practice , confucius became an advisor to the ruler of his home state of lu . but after another state sent lu 's ruler a troop of dancing girls as a present and the ruler ignored his duties while enjoying the girls in private , confucius resigned in disgust . he then spent the next few years traveling from state to state , trying to find a worthy ruler to serve , while holding fast to his principles . it was n't easy . in accordance with his philosophy , and contrary to the practice of the time , confucius dissuaded rulers from relying on harsh punishments and military power to govern their lands because he believed that a good ruler inspires others to spontaneously follow him by virtue of his ethical charisma . confucius also believed that because the love and respect we learn in the family are fundamental to all other virtues , personal duties to family sometimes supersede obligations to the state . so when one duke bragged that his subjects were so upright that a son testified against his own father when his father stole a sheep , confucius informed the duke that genuinely upright fathers and sons protected one another . during his travels , confucius almost starved , he was briefly imprisoned , and his life was threatened at several points . but he was not bitter . confucius had faith that heaven had a plan for the world , and he taught that a virtuous person could always find joy in learning and music . failing to find the ruler he sought , confucius returned to lu and became a teacher and philosopher so influential , that he helped shaped chinese culture and we recognize his name worldwide , even today . for the disciples of confucius , he was the living embodiment of a sage who leads others through his virtue , and they recorded his sayings , which eventually were edited into a book we know in english as `` the analects . '' today , millions of people worldwide adhere to the principles of confucianism , and though the precise meaning of his words has been debated for millennia , when asked to summarize his teachings in a single phrase , confucius himself said , `` do not inflict upon others that which you yourself would not want . '' 2,500 years later , it 's still sage advice .
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failing to find the ruler he sought , confucius returned to lu and became a teacher and philosopher so influential , that he helped shaped chinese culture and we recognize his name worldwide , even today . for the disciples of confucius , he was the living embodiment of a sage who leads others through his virtue , and they recorded his sayings , which eventually were edited into a book we know in english as `` the analects . '' today , millions of people worldwide adhere to the principles of confucianism , and though the precise meaning of his words has been debated for millennia , when asked to summarize his teachings in a single phrase , confucius himself said , `` do not inflict upon others that which you yourself would not want . ''
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the collection of the sayings of confucius is known in english as what ?
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why are most manhole covers round ? sure , it makes them easy to roll and slide into place in any alignment but there 's another more compelling reason involving a peculiar geometric property of circles and other shapes . imagine a square separating two parallel lines . as it rotates , the lines first push apart , then come back together . but try this with a circle and the lines stay exactly the same distance apart , the diameter of the circle . this makes the circle unlike the square , a mathematical shape called a curve of constant width . another shape with this property is the reuleaux triangle . to create one , start with an equilateral triangle , then make one of the vertices the center of a circle that touches the other two . draw two more circles in the same way , centered on the other two vertices , and there it is , in the space where they all overlap . because reuleaux triangles can rotate between parallel lines without changing their distance , they can work as wheels , provided a little creative engineering . and if you rotate one while rolling its midpoint in a nearly circular path , its perimeter traces out a square with rounded corners , allowing triangular drill bits to carve out square holes . any polygon with an odd number of sides can be used to generate a curve of constant width using the same method we applied earlier , though there are many others that are n't made in this way . for example , if you roll any curve of constant width around another , you 'll make a third one . this collection of pointy curves fascinates mathematicians . they 've given us barbier 's theorem , which says that the perimeter of any curve of constant width , not just a circle , equals pi times the diameter . another theorem tells us that if you had a bunch of curves of constant width with the same width , they would all have the same perimeter , but the reuleaux triangle would have the smallest area . the circle , which is effectively a reuleaux polygon with an infinite number of sides , has the largest . in three dimensions , we can make surfaces of constant width , like the reuleaux tetrahedron , formed by taking a tetrahedron , expanding a sphere from each vertex until it touches the opposite vertices , and throwing everything away except the region where they overlap . surfaces of constant width maintain a constant distance between two parallel planes . so you could throw a bunch of reuleaux tetrahedra on the floor , and slide a board across them as smoothly as if they were marbles . now back to manhole covers . a square manhole cover 's short edge could line up with the wider part of the hole and fall right in . but a curve of constant width wo n't fall in any orientation . usually they 're circular , but keep your eyes open , and you just might come across a reuleaux triangle manhole .
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this makes the circle unlike the square , a mathematical shape called a curve of constant width . another shape with this property is the reuleaux triangle . to create one , start with an equilateral triangle , then make one of the vertices the center of a circle that touches the other two .
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the reuleaux triangle _____ .
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rising temperatures and seas , massive droughts , changing landscapes . successfully adapting to climate change is growing increasingly important . for humans , this means using our technological advancement to find solutions , like smarter cities and better water management . but for some plants and animals , adapting to these global changes involves the most ancient solution of all : evolution . evolutionary adaptation usually occurs along time scales of thousands to hundreds of thousands of years . but in cases where species are under especially strong selective conditions , like those caused by rapidly changing climates , adaptive evolution can happen more quickly . in recent decades , we 've seen many plants , animals , and insects relocating themselves and undergoing changes to their body sizes , and the dates they flower or breed . but many of these are plastic , or nonheritable changes to an individual 's physical traits . and there are limits to how much an organism can change its own physiology to meet environmental requirements . that 's why scientists are seeking examples of evolutionary changes coded in species ' dna that are heritable , long-lasting , and may provide a key to their future . take the tawny owl . if you were walking through a wintry forest in northern europe 30 years ago , chances are you 'd have heard , rather than seen , this elusive bird . against the snowy backdrop , its plumage would have been near impossible to spot . today , the landscape is vastly different . since the 1980s , climate change has led to significantly less snowfall , but you 'd still struggle to spot a tawny owl because nowadays , they 're brown . the brown color variant is the genetically dominant form of plumage in this species , but historically , the recessive pale gray variant triumphed because of its selective advantage in helping these predators blend in . however , less snow cover reduces opportunities for camouflage , so lately , this gray color variant has been losing the battle against natural selection . the offspring of the brown color morphs , on the other hand , have an advantage in exposed forests , so brown tawny owls are flourishing today . several other species have undergone similar climate-change-adaptive genetic changes in recent decades . pitcher plant mosquitoes have rapidly evolved to take advantage of the warmer temperatures , entering dormancy later and later in the year . two spot ladybug populations , once comprised of equal numbers of melanic and non-melanic morphs , have now shifted almost entirely to the non-melanic color combination . scientists think that keeps them from overheating . meanwhile , pink salmon have adapted to warmer waters by spawning earlier in the season to protect their sensitive eggs . and wild thyme plants in europe are producing more repellent oils to protect themselves against the herbivores that become more common when it 's warm . these plants and animals belong to a group of about 20 identified species with evolutionary adaptations to rapid climate change , including snapping turtles , wood frogs , knotweed , and silver spotted skipper butterflies . however , scientists hope to discover more species evolving in response to climate change out of 8.7 million species on the planet . for most of our planet 's astounding and precious biodiversity , evolution wo n't be the answer . instead , many of those species will have to rely on us to help them survive a changing world or face extinction . the good news is we already have the tools . across the planet , we 're making on-the-ground decisions that will help entire ecosystems adapt . critical climate refuges are being identified and set aside , and projects are underway to help mobile species move to more suitable climates . existing parks and protected areas are also doing climate change check-ups to help their wildlife cope . fortunately , it 's still within our power to preserve much of the wondrous biodiversity of this planet , which , after all , sustains us in so many ways .
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several other species have undergone similar climate-change-adaptive genetic changes in recent decades . pitcher plant mosquitoes have rapidly evolved to take advantage of the warmer temperatures , entering dormancy later and later in the year . two spot ladybug populations , once comprised of equal numbers of melanic and non-melanic morphs , have now shifted almost entirely to the non-melanic color combination .
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what environmental change has driven pitcher-plant mosquitoes to delay dormancy ?
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in 1845 , ireland 's vast potato fields were struck by an invasive fungal disease that rapidly infested this staple crop . the effect was devastating . one million people died of famine , and over a million more were forced to leave ireland . nowadays , we avoid such agricultural catastrophes with the help of pesticides . those are a range of manmade chemicals that control insects , unwanted weeds , funguses , rodents , and bacteria that may threaten our food supply . they 've become an essential part of our food system . as populations have grown , monoculture , single crop farming , has helped us feed people efficiently . but it 's also left our food vulnerable to extensive attack by pests . in turn , we 've become more dependent on pesticides . today , we annually shower over 5 billion pounds of pesticides across the earth to control these unwanted visitors . the battle against pests , especially insects , has marked agriculture 's long history . records from thousands of years ago suggest that humans actively burned some of their crops after harvest to rid them of pests . there 's even evidence from ancient times that we recruited other insects to help . in 300 a.d. , chinese farmers specially bred ferocious predatory ants in orange orchards to protect the trees from other bugs . later , as large-scale farming spread , we began sprinkling arsenic , lead , and copper treatments on crops . but these were incredibly toxic to humans as well . as our demand for more , safer produce increased , so did the need for effective chemicals that could control pests on a grander scale . this ushered in the era of chemical pesticides . in 1948 , a swiss chemist named paul hermann müller was awarded a nobel prize for his discovery of dichlorodiphenyltrichloroethane , also known as ddt . this new molecule had unparalleled power to control many insect species until the 1950s , when insects became resistant to it . worse , the chemical actually drove dramatic declines in bird populations , poisoned water sources , and was eventually found to cause long-term health problems in humans . by 1972 , ddt had been banned in the united states , and yet traces still linger in the environment today . since then , chemists have been searching for alternatives . with each new wave of inventions , they 've encountered the same obstacle - rapid species evolution . as pesticides destroy pest populations , they leave behind only the most resistant individuals . they then pass on their pesticide-resisting genes to the next generation . that 's lead to the rise of super bugs , such as the colorado potato beetle , which is resistant to over 50 different insecticides . another downside is that other bugs get caught in the crossfire . some of these are helpful predators of plant pests or vital pollinators , so erasing them from agriculture wipes out their benefits , too . pesticides have improved over time and are currently regulated by strict safety standards , but they still have the potential to pollute soil and water , impact wildlife , and even harm us . so considering all these risks , why do we continue using pesticides ? although they 're imperfect , they currently may be our best bet against major agricultural disasters , not to mention mosquito-born diseases . today , scientists are on a quest for alternative pest control strategies that balance the demands of food production with environmental concerns . nature has become a major source of inspiration , from natural plant and fungal chemicals that can repel or attract insects , to recruiting other insects as crop bodyguards . we 're also turning to high-tech solutions , like drones . programmed to fly over crops , these machines can use their sensors and gps to carry out more targeted sprays that limit a pesticide 's wider environmental impact . with a combination of biological understanding , environmental awareness , and improved technologies , we have a better chance of finding a holistic solution to pests . chemical pesticides may never shake their controversial reputation , but with their help , we can ensure that agricultural catastrophes stay firmly in our past .
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with each new wave of inventions , they 've encountered the same obstacle - rapid species evolution . as pesticides destroy pest populations , they leave behind only the most resistant individuals . they then pass on their pesticide-resisting genes to the next generation .
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which of the organisms listed below can be considered a pest ?
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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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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 .
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if it is possible to win the presidency by winning 11 large states , why do you think candidates pay attention to smaller states ? can you think of additional strategies that would benefit a democrat or a republican specifically ?
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the evolutionary tango of animal genitalia . can you guess what you 're looking at ? if you answered `` duck vagina , '' you 'd be right . although the bird 's outward appearance may not strike you as especially odd , it uses this strange , intricate , cork-screw shaped contraption to reproduce . we see similarly unbelievable genitalia in insects , mammals , reptiles , fish , spiders , and even snails . apparently , no organs evolve faster and into more variable shapes than those involved in procreation . superficially , it makes sense because evolution works via reproduction . when an animal leaves more offspring , its genes will spread . and since genitalia are an animal 's tools for reproduction , any improvement there will have immediate effect . and yet , what 's the point of having such decorative nether regions ? after all , the function of genitalia seems simple . a penis deposits a bit of sperm and a vagina receives it and delivers it to the egg . a pipette-like thingy on the male and a funnel-like gizmo on the female should do just fine for any animal . and yet , that 's not what we see . the penis of a chicken flea , for example , looks nothing like a pipette , more like an exploded grandfather clock . and the vagina of a featherwing beetle resembles something you 'd find in a dr. seuss book . throughout the animal kingdom , genitalia are very complex things , much more complicated than seems necessary for what they 're meant to do . that 's because genitalia do more than just deposit and receive sperm . many male animals also use the penis as courtship device , like crane flies . in some south american species , males have a tiny washboard and scraper on their penis , which produces a song that reverberates throughout the female 's body when they mate . it 's thought that if female crane flies enjoy this unusual serenade , they 'll allow the male to father their offspring . this way , the genes of the most musical penises spread , leading to rapid evolution of insects ' phalluses . similarly , some beetles have two little drumsticks on either side of the penis . during mating , they 'll rub , slap , or tap the female with these . and some hoofed mammals , like rams and bulls , use a whip-like extension on the penis 's left side to create a sensation during mating . but how can females really choose between males if she can only assess them after mating ? this is where the power of female adaptation comes into play . in fact , insemination is different to conception , and the female genitalia exploit this distinction . for instance , in some dung flies , the vagina contains pockets for separating sperm from different males depending on how appealing they were . males using their penises for courtship and females controlling their own sperm management are two reasons why genitalia evolve into such complex shapes . but there are others because genitalia are also where a sexual conflict is played out . a female 's interests are best served if she fertilizes her eggs with the sperm of the best fathers and creates genetic variability amongst her offspring . for a male , on the other hand , this is bad news . for him , it would be best if a female used his sperm to fertilize all of her eggs . so we see cycles of adaptation in an evolutionary arms race to retain control . black widow spiders have a disposable penis tip that breaks off inside the vagina blocking the attempts of his rivals , and bed bug males bypass a female 's genitalia altogether using a syringe-like penis to inject sperm cells directly into her belly . not to be outdone , females have evolved their own countermeasures . in some bed bug species , the females have evolved an entirely new set of genitalia on their right hand flanks where the males usually pierce them . that allows them to maintain the power to filter out unwanted sperm with their genitalia . and duck vaginas are shaped like a clockwise spiral so that when the male inflates his long , counterclockwise coiled penis into her , and she disapproves , all she needs to do is flex her vaginal muscles and the penis just flubs out . so , genitalia differs so much , not just to fascinate us , but because in every species , they 're the result of a furious evolutionary tango of sex that has been going on for millions of years and will continue for millions of years to come .
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similarly , some beetles have two little drumsticks on either side of the penis . during mating , they 'll rub , slap , or tap the female with these . and some hoofed mammals , like rams and bulls , use a whip-like extension on the penis 's left side to create a sensation during mating .
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after mating with a female , how do male black widow spiders discourage future males from mating with her as well ?
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everybody loves fireworks -- the lights , the colors , and , of course , the big boom . but the history of fireworks is n't all hugs and celebrations . long before epic fireworks displays , chemists in china invented the key ingredient that propels those bright lights into the sky . that invention was what we now call gunpowder . our story begins back in ancient china in the mid-ninth century where early chinese alchemists were trying to create a potion for immortality . instead , what they created was a flammable powder that burned down many of their homes . they quickly realized that this black powder , which they called fire medicine , was precisely the opposite of something that would make you live forever . in these early days , the chinese had n't yet figured out how to make the powder explode ; it was simply very flammable , and their armies used it to make flaming arrows and even a flamethrower . but once they figured out the right proportions of ingredients to create a blast , they began using the powder even more , creating fireworks to keep evil spirits away and bombs to defend themselves against mongol invaders . it was these mongols , most likely , who spread the invention of gunpowder across the world . after fielding chinese attacks , they learned how to produce the powder themselves and brought it with them on their conquests in persia and india . william of rubruck , a european ambassador to the mongols , was likely responsible for bringing gunpowder back to europe around 1254 . from there , engineers and military inventors created all kinds of destructive weapons . from bombs to guns to cannons , gunpowder left its mark on the world in some pretty terrible ways , in contrast to the beautiful marks it can leave in the air . so , how does black powder propel fireworks into the sky ? you might have seen old westerns or cartoons where a trail of gunpowder is lit and it leads to a large and obviously explosive barrel . once the fire gets to the barrel , a large boom occurs . but why does n't the trail itself explode ? the reason is that burning the powder releases energy and gases . while the trail is burning , these are easily released into the surrounding air . but when the gunpowder is contained within the barrel , the energy and gases can not easily escape and build up until boom ! firework canisters provide a single , upward-facing outlet to channel this explosive energy . the wick ignites the gunpowder and the energy takes the easiest exit from the canister , launching the firework high into the sky . the flame then makes its way through the firework 's encasing and the same reaction occurs high above our heads . so , while the chinese alchemists never found the compound for eternal life , they did find something that would go on to shape all of civilization , something that has caused many tragic moments in human history , and yet still gives us hope when we look up in celebration at the colorful night sky .
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the wick ignites the gunpowder and the energy takes the easiest exit from the canister , launching the firework high into the sky . the flame then makes its way through the firework 's encasing and the same reaction occurs high above our heads . so , while the chinese alchemists never found the compound for eternal life , they did find something that would go on to shape all of civilization , something that has caused many tragic moments in human history , and yet still gives us hope when we look up in celebration at the colorful night sky .
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what does sulfur do in the combustion reaction ?
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have you ever heard the term , `` tip of the iceberg '' ? you know that icebergs are mostly underwater , their immense bulk hidden beneath the water . but why is that so ? well , the density of pure ice is less than that of sea water . usually only 1/9 of the volume of an iceberg is above the water . the shape of the underwater portion is difficult to discern by looking at the above-surface portion . this has led to the expression , `` tip of the iceberg . '' here are some thing you might not know about the icy islands . the life of an iceberg begins many thousands of years before it reaches the ocean . unlike sea ice or pack ice , which form when the ocean freezes , glaciers are made of fresh water . for thousands of years , these glaciers build layer upon layer of ice , constantly compressing , moving , adding snow , compressing , and moving again as they inch along like a frozen river . it is the force of gravity that pulls them towards the sea , where a glacier may calve off to become an iceberg or continue to spread up as an ice shelf or an ice tongue . once an iceberg breaks away from the glacier or ice shelf , it will usually live for three to six years , floating around , carried by the currents and tidal movements of the ocean . as it floats along , it is battered by waves , melts , and smashes into land and sometimes other icebergs . some icebergs are so unstable that they have more dramatic ends , heaving up , collapsing , and sometimes even exploding . and as they fall apart , many icebergs make all sorts of strange sounds . when a piece of iceberg melts , it makes a fizzing sound , called bergie seltzer . this sound is made when the water-ice interface reaches compressed air bubbles trapped in the ice . as this happens , each bubble bursts , making a popping sound . there are six official size classifications for icebergs . the smallest icebergs are called growlers . they can be up the size of your car and are very dangerous for ships and boats because usually they sit just at the waterline where they are not easy to spot . next are the bergy bits - yes , that is their scientific name - which can be up to the size of your home . the other four sizes are small , medium , large , and very large . so just how big is a very large iceberg ? officially , any iceberg looming larger than 270 feet high above sea level and 670 feet long is considered very large . that 's 27 stories of looming , blue ice . and how do icebergs get that blue color anyways ? when snow on the glacier is compressed over many hundreds of years , the weight of the snow forces the air bubbles out of the ice , creating pure ice with very little air trapped inside . this compression is seen when the glacier calves , creating a blue iceberg . an iceberg that has not experienced as much compression and has a large amount of air and surface edges reflects light as white . although they form in far northern or southern areas , icebergs can float thousands of miles . an iceberg from the arctic floated as far south as bermuda . antarctic icebergs are mostly trapped in the circumpolar current , never giving them a chance to float north . however , they have been known to interrupt shipping lanes between australia , south america , and south africa . for all their travelling , many people think that these slabs of ice are barren of life , but these seemingly sterile ice slabs also harbor their own complex ecosystems and they shape the ecosystems that they pass through . they become mobile , floating ecosystems . even in the coldest seas , icebergs are always melting , at least a little bit . this melting has a major impact on the ocean around an iceberg . the fresh water from the berg creates a pool of fresh water that can extend a nautical mile away from the iceberg . this water is colder than the surrounding sea water , and the temperature variation creates thermal currents in the vicinity of the iceberg . life thrives on and around an iceberg . young icefish hide in small ice holes to avoid predators , while a variety of invertebrates , like jellyfish and siphonophores , congregate in the area . many of them come to feed on krill , tiny shrimp-like creatures . snow petrels nest on the icebergs and feed on the sea life nearby . whales and seals and penguins seem to like them too . and even now that you know all this , we 're still at the tip of the iceberg . there are all sorts of things we do n't know about icebergs . perhaps you 'll be the one to see a little deeper .
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when snow on the glacier is compressed over many hundreds of years , the weight of the snow forces the air bubbles out of the ice , creating pure ice with very little air trapped inside . this compression is seen when the glacier calves , creating a blue iceberg . an iceberg that has not experienced as much compression and has a large amount of air and surface edges reflects light as white .
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what is a glacier ?
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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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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 ?
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how did materials scientists manage to produce bulk metallic glasses ?
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in 1997 , a french woman named jeanne calment passed away after 122 years and 164 days on this earth , making her the oldest known person in history . her age was so astounding that a millionaire pledged $ 1 million to anyone who could break her record . but in reality , living to this age or beyond is a feat that very few , maybe even no humans , are likely to accomplish . human bodies just are n't built for extreme aging . our capacity is set at about 90 years . but what does aging really mean and how does it counteract the body 's efforts to stay alive ? we know intuitively what it means to age . for some , it means growing up , while for others , it 's growing old . yet finding a strict scientific definition of aging is a challenge . what we can say is that aging occurs when intrinsic processes and interactions with the environment , like sunlight , and toxins in the air , water , and our diets , cause changes in the structure and function of the body 's molecules and cells . those changes in turn drive their decline , and subsequently , the failure of the whole organism . the exact mechanisms of aging are poorly understood . but recently , scientists have identified nine physiological traits , ranging from genetic changes to alterations in a cell 's regenerative ability that play a central role . firstly , as the years pass , our bodies accumulate genetic damage in the form of dna lesions . these occur naturally when the body 's dna replicates , but also in non-dividing cells . organelles called mitochondria are especially prone to this damage . mitochondria produce adenosine triphosphate , or atp , the main energy source for all cellular processes , plus mitochondria regulate many different cell activities and play an important role in programmed cell death . if mitochondrial function declines , then cells and , later on , whole organs , deteriorate , too . other changes are known to occur in the expression patterns of genes , also known as epigenetic alterations , that affect the body 's tissues and cells . genes silenced or expressed only at low levels in newborns become prominent in older people , leading to the development of degenerative diseases , like alzheimer 's , which accelerate aging . even if we could avoid all these harmful genetic alterations , not even our own cells could save us . the fact remains that cellular regeneration , the very stuff of life , declines as we age . the dna in our cells is packaged within chromosomes , each of which has two protective regions at the extremities called telomeres . those shorten every time cells replicate . when telomeres become too short , cells stop replicating and die , slowing the body 's ability to renew itself . with age , cells increasingly grow senescent , too , a process that halts the cell cycle in times of risk , like when cancer cells are proliferating . but the response also kicks in more as we age , halting cell growth and cutting short their ability to replicate . aging also involves stem cells that reside in many tissues and have the property of dividing without limits to replenish other cells . as we get older , stem cells decrease in number and tend to lose their regenerative potential , affecting tissue renewal and maintenance of our organs original functions . other changes revolve around cells ' ability to function properly . as they age , they stop being able to do quality control on proteins , causing the accumulation of damaged and potentially toxic nutrients , leading to excessive metabolic activity that could be fatal for them . intercellular communication also slows , ultimately undermining the body 's functional ability . there 's a lot we do n't yet understand about aging . ultimately , does longer life as we know it come down to diet , exercise , medicine , or something else ? will future technologies , like cell-repairing nanobots , or gene therapy , artificially extend our years ? and do we want to live longer than we already do ? starting with 122 years as inspiration , there 's no telling where our curiosity might take us .
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the dna in our cells is packaged within chromosomes , each of which has two protective regions at the extremities called telomeres . those shorten every time cells replicate . when telomeres become too short , cells stop replicating and die , slowing the body 's ability to renew itself . with age , cells increasingly grow senescent , too , a process that halts the cell cycle in times of risk , like when cancer cells are proliferating . but the response also kicks in more as we age , halting cell growth and cutting short their ability to replicate .
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tumor cells can be considered “ immortal ” in comparison with normal cells . how can a cell become immortal ?
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you work at the college library . you 're in the middle of a quiet afternoon when suddenly a shipment of 1,280 different books arrives . the books have been dropped of in one long straight line , but they 're all out of order , and the automatic sorting system is broken . to make matters worse , classes start tomorrow , which means that first thing in the morning , students will show up in droves looking for these books . how can you get them all sorted in time ? one way would be to start at one end of the line with the first pair of books . if the first two books are in order , then leave them as they are . otherwise , swap them . then , look at the second and third books , repeat the process , and continue until you reach the end of the line . at some point , you 'll come across the book that should be last , and keep swapping it with every subsequent book , moving it down the line until it reaches the end where it belongs . then , start from the beginning and repeat the process to get the second to last book in its proper place , and keep going until all books are sorted . this approach is called bubble sort . it 's simple but slow . you 'd make 1,279 comparisons in the first round , then 1,278 , and so on , adding up to 818,560 comparisons . if each took just one second , the process would take over nine days . a second strategy would be to start by sorting just the first two books . then , take the third book and compare it with the book in the second spot . if it belongs before the second book , swap them , then compare it with the book in the first spot , and swap again if needed . now you 've sorted the first three books . keep adding one book at a time to the sorted sub-line , comparing and swapping the new book with the one before it until it 's correctly placed among the books sorted so far . this is called insertion sort . unlike bubble sort , it usually does n't require comparing every pair of books . on average , we 'd expect to only need to compare each book to half of the books that came before it . in that case , the total number of comparisons would be 409,280 , taking almost five days . you 're still doing way too many comparisons . here 's a better idea . first , pick a random book . call it the partition and compare it to every other book . then , divide the line by placing all the books that come before the partition on its left and all the ones that come after it on its right . you 've just saved loads of time by not having to compare any of the books on the left to any of the ones on the right ever again . now , looking only at the books on the left , you can again pick a random partition book and separate those books that come before it from those that come after it . you can keep creating sub-partitions like this until you have a bunch of small sub-lines , each of which you 'd sort quickly using another strategy , like insertion sort . each round of partitioning requires about 1,280 comparisons . if your partitions are pretty balanced , dividing the books into 128 sub-lines of ten would take about seven rounds , or 8,960 seconds . sorting these sub-lines would add about 22 seconds each . all in all , this method known as quicksort could sort the books in under three and a half hours . but there 's a catch . your partitions could end up lopsided , saving no time at all . luckily , this rarely happens . that 's why quicksort is one of the most efficient strategies used by programmers today . they use it for things like sorting items in an online store by price , or creating a list of all the gas stations close to a given location sorted by distance . in your case , you 're done quick sorting with time to spare . just another high-stakes day in the library .
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then , look at the second and third books , repeat the process , and continue until you reach the end of the line . at some point , you 'll come across the book that should be last , and keep swapping it with every subsequent book , moving it down the line until it reaches the end where it belongs . then , start from the beginning and repeat the process to get the second to last book in its proper place , and keep going until all books are sorted .
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in which sorting algorithm did we come across the book that should be last in line , and then keep comparing that book with each subsequent book until we reach the end of the line ?
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translator : andrea mcdonough reviewer : jessica ruby hello , humans . my name is matt and for the next several moments , you are going to listen to me . mwah , ha , ha , ha , ha . sorry . i 'm just joking . this is my normal voice . have you ever taken direction from a mysterious voice on the computer before ? no ? perfect ! i want to try an experiment with you , but i ca n't tell you what that experiment entails because if i do , it wo n't work . you 'll just have to trust me . this will all make sense soon , hopefully . if you 're sitting down , stand up from your chair and take a step back . in a moment , i 'm going to have you twirl around , so give yourself a bit of space . need to move some furniture around ? take your time . i 'll wait . on the count of three , you 're going to start hopping on one foot . are you ready ? one , two , three ! hop , hop , hop , hop , hop . nice work ! ok , while you 're still hopping , i now want you to begin barking like a dog . ruff , ruff ; ruff , ruff ; ruff , ruff . wow , that 's quite a bark ! and a few more . ruff , ruff , ruff . and three , two , one , stop ! feel free to relax and sit back down . now , i want you think about how much time passed between the moment i said , `` go ! '' and you began hopping on one foot to the moment i said , `` stop ! '' take a guess . i 'm looking for an exact number of seconds or minutes . now , with a pen and paper , write that number down . all done ? the exact time was actually 26 seconds . did you overestimate ? chances are that you did . so , what was the culprit ? the culprit was time perception . although we can make shockingly precise time estimates , when we experience something new , unusual , or dynamic , like hopping on one foot while taking instructions from a voice on the computer , or , say , jumping out of an airplane , we often miscalculate how much time has passed . meaning , if you bungee jump for the first time , your fall to the bottom may seem like it lasted for 10 seconds while the recorded time may actually show that the jump only lasted for 5 . the reason for this difference is unlike your body 's physical drop to the bottom , your brain 's perception of time does not follow a straight line between two points . some scientists even believe your brain follows more of a curved path that is dependent on the amount of information you take in as you fall downwards . for example , david eagleman , a neuroscientist at baylor college of medicine , believes time perception is heavily influenced by the number of memories and data you record onto your brain . when you have a new experience , like jumping off a high dive for the first time , your senses are heightened . you 're taking in more details about sights , sounds , and smells than you normally would . and you store more data onto your brain in the form of memories . so , the more data you store in your brain , like the smell of chlorine as you leapt from the high dive or the color of the water , the longer your perception of that experience . meaning , the number of memories and data you record on your brain has a direct impact on how long you believe that experience to have lasted . have you ever heard a person recount what it 's like to be in a car accident ? although automotive accidents typically last seconds , those involved often say they felt the accident lasted far longer . time perception can also account for why your childhood may have seem to have lasted forever . by adulthood , a year can slip by in a heartbeat , but children record more data onto their brains . this occurs because many of the experiences we have as children are new and unfamiliar to us . the stack of encoded memories on your brain is so dense that reading them back makes you believe your experiences must have taken forever . additionally , when you 're 5 years old , one year is 1/5 of your life . but , when you 're 25 , one year makes up 1/25 , further altering your perception of time . and , if you 're an adult , think about a trip that you may have taken to a far-away land for the first time . did n't those two weeks you spent exploring your surroundings seem to have lasted far longer than 14 days ? though time perception is rooted in both hard science and theory , it provides a great lesson for us on how to live our lives . i 'm sure you have all heard that a person should n't sit on a couch and let life pass them by . well , time perception tells us why that is . if you get up and engage with the world and have new experiences , and maybe even hop around on one foot and bark like a dog , you will literally perceive your own life to have lasted for a longer period of time .
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so , what was the culprit ? the culprit was time perception . although we can make shockingly precise time estimates , when we experience something new , unusual , or dynamic , like hopping on one foot while taking instructions from a voice on the computer , or , say , jumping out of an airplane , we often miscalculate how much time has passed .
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scientists believe time perception is important because :
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so this is a sample of osmium . osmium , again , is a precious metal , platinum-group metal , and this is an osmium sponge which is very nicely packaged up in this box . so let ’ s have a look and see if we can find it . so osmium is another one of the elements in the so-called ‘ platinum group ’ and it is quite unusual in that its oxide – osmium tetroxide is a stable compound which is really quite easily evaporated . it has quite a strong smell which is unusual for metal compounds and it can be evaporated quite easily and it is used in organic chemistry because if you have compounds with double bonds between two carbon atoms , osmium tetroxide reacts with it really quite easily . so here the osmium itself , it is a very , very reactive metal , it is sealed in this glass ampule under an inert atmosphere of argon so that it can ’ t oxidise . the argon is very inert and it stops the metal reacting . so here you can see this very dark black metal , very fine spongy-type material , at the bottom of this glass vial . again , osmium has played some role in my life because i did some of the early work in my doctorate involved osmium compound , it was ruthenium and osmium and iron . the ruthenium compound was orange , the osmium compound a rather fetching pale yellow and the iron compound a very dark green . and the osmium compound was perhaps the most boring because it behaved in exactly the way that was predicted . so osmium reacts with the air to form osmium tetroxide , which is a very , very toxic material , it makes us go blind so we have very careful with storing the osmium . since then , i think in my life i have made one osmium compound that nobody had ever made before , it wasn ’ t enough to see but i could see the absorption of light by this compound , so i was really quite excited . do you remember what it was it in it ? what ? do you remember what it was , the compound ? the compound was osmium dicarbonyl dinitrosyl and it was interesting because nobody had ever made this compound before , but it was similar to a compound of iron which was quite well known . the compound of iron looked like blood ; it was a really quite dramatic compound . i never found out what the colour of the osmium compound was , i never made enough , but i am not a very good synthetic chemist .
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so here you can see this very dark black metal , very fine spongy-type material , at the bottom of this glass vial . again , osmium has played some role in my life because i did some of the early work in my doctorate involved osmium compound , it was ruthenium and osmium and iron . the ruthenium compound was orange , the osmium compound a rather fetching pale yellow and the iron compound a very dark green . and the osmium compound was perhaps the most boring because it behaved in exactly the way that was predicted . so osmium reacts with the air to form osmium tetroxide , which is a very , very toxic material , it makes us go blind so we have very careful with storing the osmium . since then , i think in my life i have made one osmium compound that nobody had ever made before , it wasn ’ t enough to see but i could see the absorption of light by this compound , so i was really quite excited .
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which compound is formed when metallic osmium is exposed to air ; it is useful in the organic synthetic laboratory and pete said it is very toxic ?
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a banker in london sends the latest stock info to his colleagues in hong kong in less than a second . with a single click , a customer in new york orders electronics made in beijing , transported across the ocean within days by cargo plane or container ship . the speed and volume at which goods and information move across the world today is unprecedented in history . but global exchange itself is older than we think , reaching back over 2,000 years along a 5,000 mile stretch known as the silk road . the silk road was n't actually a single road , but a network of multiple routes that gradually emerged over centuries , connecting to various settlements and to each other thread by thread . the first agricultural civilizations were isolated places in fertile river valleys , their travel impeded by surrounding geography and fear of the unknown . but as they grew , they found that the arid deserts and steps on their borders were inhabited , not by the demons of folklore , but nomadic tribes on horseback . the scythians , who ranged from hungary to mongolia , had come in contact with the civilizations of greece , egypt , india and china . these encounters were often less than peaceful . but even through raids and warfare , as well as trade and protection of traveling merchants in exchange for tariffs , the nomads began to spread goods , ideas and technologies between cultures with no direct contact . one of the most important strands of this growing web was the persian royal road , completed by darius the first in the 5th century bce . stretching nearly 2,000 miles from the tigris river to the aegean sea , its regular relay points allowed goods and messages to travel at nearly 1/10 the time it would take a single traveler . with alexander the great 's conquest of persia , and expansion into central asia through capturing cities like samarkand , and establishing new ones like alexandria eschate , the network of greek , egyptian , persian and indian culture and trade extended farther east than ever before , laying the foundations for a bridge between china and the west . this was realized in the 2nd century bce , when an ambassador named zhang qian , sent to negotiate with nomads in the west , returned to the han emperor with tales of sophisticated civilizations , prosperous trade and exotic goods beyond the western borders . ambassadors and merchants were sent towards persia and india to trade silk and jade for horses and cotton , along with armies to secure their passage . eastern and western routes gradually linked together into an integrated system spanning eurasia , enabling cultural and commercial exhange farther than ever before . chinese goods made their way to rome , causing an outflow of gold that led to a ban on silk , while roman glassware was highly prized in china . military expeditions in central asia also saw encounters between chinese and roman soldiers . possibly even transmitting crossbow technology to the western world . demand for exotic and foreign goods and the profits they brought , kept the strands of the silk road in tact , even as the roman empire disintegrated and chinese dynasties rose and fell . even mongolian hoards , known for pillage and plunder , actively protected the trade routes , rather than disrupting them . but along with commodities , these routes also enabled the movement of traditions , innovations , ideologies and languages . originating in india , buddhism migrated to china and japan to become the dominant religion there . islam spread from the arabian penninsula into south asia , blending with native beliefs and leading to new faiths , like sikhism . and gunpowder made its way from china to the middle east forging the futures of the ottoman , safavid and mughul empires . in a way , the silk road 's success led to its own demise as new maritime technologies , like the magnetic compass , found their way to europe , making long land routes obsolete . meanwhile , the collapse of mongol rule was followed by china 's withdrawal from international trade . but even though the old routes and networks did not last , they had changed the world forever and there was no going back . europeans seeking new maritime routes to the riches they knew awaited in east asia led to the age of exploration and expansion into africa and the americas . today , global interconnectedness shapes our lives like never before . canadian shoppers buy t-shirts made in bangladesh , japanese audiences watch british television shows , and tunisians use american software to launch a revolution . the impact of globalization on culture and economy is indisputable . but whatever its benefits and drawbacks , it is far from a new phenomenon . and though the mountains , deserts and oceans that once separated us are now circumvented through super sonic vehicles , cross-continental communication cables , and signals beamed through space rather than caravans traveling for months , none of it would have been possible without the pioneering cultures whose efforts created the silk road : history 's first world wide web .
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but along with commodities , these routes also enabled the movement of traditions , innovations , ideologies and languages . originating in india , buddhism migrated to china and japan to become the dominant religion there . islam spread from the arabian penninsula into south asia , blending with native beliefs and leading to new faiths , like sikhism .
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what religion makes it way from india along silk roads to china ?
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how did adolf hitler , a tyrant who orchestrated one of the largest genocides in human history , rise to power in a democratic country ? the story begins at the end of world war i . with the successful allied advance in 1918 , germany realized the war was unwinnable and signed an armistice ending the fighting . as its imperial government collapsed , civil unrest and worker strikes spread across the nation . fearing a communist revolution , major parties joined to suppress the uprisings , establishing the parliamentary weimar republic . one of the new government 's first tasks was implementing the peace treaty imposed by the allies . in addition to losing over a tenth of its territory and dismantling its army , germany had to accept full responsibility for the war and pay reparations , debilitating its already weakened economy . all this was seen as a humiliation by many nationalists and veterans . they wrongly believed the war could have been won if the army had n't been betrayed by politicians and protesters . for hitler , these views became obsession , and his bigotry and paranoid delusions led him to pin the blame on jews . his words found resonance in a society with many anti-semitic people . by this time , hundreds of thousands of jews had integrated into german society , but many germans continued to perceive them as outsiders . after world war i , jewish success led to ungrounded accusations of subversion and war profiteering . it can not be stressed enough that these conspiracy theories were born out of fear , anger , and bigotry , not fact . nonetheless , hitler found success with them . when he joined a small nationalist political party , his manipulative public speaking launched him into its leadership and drew increasingly larger crowds . combining anti-semitism with populist resentment , the nazis denounced both communism and capitalism as international jewish conspiracies to destroy germany . the nazi party was not initially popular . after they made an unsuccessful attempt at overthrowing the government , the party was banned , and hitler jailed for treason . but upon his release about a year later , he immediately began to rebuild the movement . and then , in 1929 , the great depression happened . it led to american banks withdrawing their loans from germany , and the already struggling german economy collapsed overnight . hitler took advantage of the people 's anger , offering them convenient scapegoats and a promise to restore germany 's former greatness . mainstream parties proved unable to handle the crisis while left-wing opposition was too fragmented by internal squabbles . and so some of the frustrated public flocked to the nazis , increasing their parliamentary votes from under 3 % to over 18 % in just two years . in 1932 , hitler ran for president , losing the election to decorated war hero general von hindenburg . but with 36 % of the vote , hitler had demonstrated the extent of his support . the following year , advisors and business leaders convinced hindenburg to appoint hitler as chancellor , hoping to channel his popularity for their own goals . though the chancellor was only the administrative head of parliament , hitler steadily expanded the power of his position . while his supporters formed paramilitary groups and fought protestors in streets . hitler raised fears of a communist uprising and argued that only he could restore law and order . then in 1933 , a young worker was convicted of setting fire to the parliament building . hitler used the event to convince the government to grant him emergency powers . within a matter of months , freedom of the press was abolished , other parties were disbanded , and anti-jewish laws were passed . many of hitler 's early radical supporters were arrested and executed , along with potential rivals , and when president hindenburg died in august 1934 , it was clear there would be no new election . disturbingly , many of hitler 's early measures did n't require mass repression . his speeches exploited people 's fear and ire to drive their support behind him and the nazi party . meanwhile , businessmen and intellectuals , wanting to be on the right side of public opinion , endorsed hitler . they assured themselves and each other that his more extreme rhetoric was only for show . decades later , hitler 's rise remains a warning of how fragile democratic institutions can be in the face of angry crowds and a leader willing to feed their anger and exploit their fears .
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but upon his release about a year later , he immediately began to rebuild the movement . and then , in 1929 , the great depression happened . it led to american banks withdrawing their loans from germany , and the already struggling german economy collapsed overnight . hitler took advantage of the people 's anger , offering them convenient scapegoats and a promise to restore germany 's former greatness . mainstream parties proved unable to handle the crisis while left-wing opposition was too fragmented by internal squabbles .
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the fact that the nazis had virtually no power in the german government before the great depression , how did this make hitler ’ s rhetoric & promises to restore germany ’ s greatness more attractive to the german people ?
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on a december afternoon in chicago during the middle of world war ii , scientists cracked open the nucleus at the center of the uranium atom and turned nuclear mass into energy over and over again . they did this by creating for the first time a chain reaction inside a new engineering marvel : the nuclear reactor . since then , the ability to mine great amounts of energy from uranium nuclei has led some to bill nuclear power as a plentiful utopian source of electricity . a modern nuclear reactor generates enough electricity from one kilogram of fuel to power an average american household for nearly 34 years . but rather than dominate the global electricity market , nuclear power has declined from an all-time high of 18 % in 1996 to 11 % today . and it 's expected to drop further in the coming decades . what happened to the great promise of this technology ? it turns out nuclear power faces many hurdles , including high construction costs and public opposition . and behind these problems lie a series of unique engineering challenges . nuclear power relies on the fission of uranium nuclei and a controlled chain reaction that reproduces this splitting in many more nuclei . the atomic nucleus is densely packed with protons and neutrons bound by a powerful nuclear force . most uranium atoms have a total of 238 protons and neutrons , but roughly one in every 140 lacks three neutrons , and this lighter isotope is less tightly bound . compared to its more abundant cousin , a strike by a neutron easily splits the u-235 nuclei into lighter , radioactive elements called fission products , in addition to two to three neutrons , gamma rays , and a few neutrinos . during fission , some nuclear mass transforms into energy . a fraction of the newfound energy powers the fast-moving neutrons , and if some of them strike uranium nuclei , fission results in a second larger generation of neutrons . if this second generation of neutrons strike more uranium nuclei , more fission results in an even larger third generation , and so on . but inside a nuclear reactor , this spiraling chain reaction is tamed using control rods made of elements that capture excess neutrons and keep their number in check . with a controlled chain reaction , a reactor draws power steadily and stably for years . the neutron-led chain reaction is a potent process driving nuclear power , but there 's a catch that can result in unique demands on the production of its fuel . it turns out , most of the neutrons emitted from fission have too much kinetic energy to be captured by uranium nuclei . the fission rate is too low and the chain reaction fizzles out . the first nuclear reactor built in chicago used graphite as a moderator to scatter and slow down neutrons just enough to increase their capture by uranium and raise the rate of fission . modern reactors commonly use purified water as a moderator , but the scattered neutrons are still a little too fast . to compensate and keep up the chain reaction , the concentration of u-235 is enriched to four to seven times its natural abundance . today , enrichment is often done by passing a gaseous uranium compound through centrifuges to separate lighter u-235 from heavier u-238 . but the same process can be continued to highly enrich u-235 up to 130 times its natural abundance and create an explosive chain reaction in a bomb . methods like centrifuge processing must be carefully regulated to limit the spread of bomb-grade fuel . remember , only a fraction of the released fission energy goes into speeding up neutrons . most of the nuclear power goes into the kinetic energy of the fission products . those are captured inside the reactor as heat by a coolant , usually purified water . this heat is eventually used to drive an electric turbine generator by steam just outside the reactor . water flow is critical not only to create electricity , but also to guard against the most dreaded type of reactor accident , the meltdown . if water flow stops because a pipe carrying it breaks , or the pumps that push it fail , the uranium heats up very quickly and melts . during a nuclear meltdown , radioactive vapors escape into the reactor , and if the reactor fails to hold them , a steel and concrete containment building is the last line of defense . but if the radioactive gas pressure is too high , containment fails and the gasses escape into the air , spreading as far and wide as the wind blows . the radioactive fission products in these vapors eventually decay into stable elements . while some decay in a few seconds , others take hundreds of thousands of years . the greatest challenge for a nuclear reactor is to safely contain these products and keep them from harming humans or the environment . containment does n't stop mattering once the fuel is used up . in fact , it becomes an even greater storage problem . every one to two years , some spent fuel is removed from reactors and stored in pools of water that cool the waste and block its radioactive emissions . the irradiated fuel is a mix of uranium that failed to fission , fission products , and plutonium , a radioactive material not found in nature . this mix must be isolated from the environment until it has all safely decayed . many countries propose deep time storage in tunnels drilled far underground , but none have been built , and there 's great uncertainty about their long-term security . how can a nation that has existed for only a few hundred years plan to guard plutonium through its radioactive half-life of 24,000 years ? today , many nuclear power plants sit on their waste , instead , storing them indefinitely on site . apart from radioactivity , there 's an even greater danger with spent fuel . plutonium can sustain a chain reaction and can be mined from the waste to make bombs . storing spent fuel is thus not only a safety risk for the environment , but also a security risk for nations . who should be the watchmen to guard it ? visionary scientists from the early years of the nuclear age pioneered how to reliably tap the tremendous amount of energy inside an atom - as an explosive bomb and as a controlled power source with incredible potential . but their successors have learned humbling insights about the technology 's not-so-utopian industrial limits . mining the subatomic realm makes for complex , expensive , and risky engineering .
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to compensate and keep up the chain reaction , the concentration of u-235 is enriched to four to seven times its natural abundance . today , enrichment is often done by passing a gaseous uranium compound through centrifuges to separate lighter u-235 from heavier u-238 . but the same process can be continued to highly enrich u-235 up to 130 times its natural abundance and create an explosive chain reaction in a bomb .
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the concentration of the lighter isotope of uranium , uranium-235 , is very low in nature relative to the abundance of the heavier uranium-238 . in most modern reactors , the abundance of uranium-235 in the fuel needs to be enriched by a factor of :
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this is ytterbium . again , a lanthanide . stored in a very old glass bowl . ytterbium is one of three lanthanides , which was named after a swedish town called ytterby which is where they were all discovered . ytterbium , terbium and erbium were all derivatives of that town name . the town 's done well out of it , has n't it ? -the town 's did very well out of it , yeah . have you ever been there ? no , not personally . -you should go ! yeah , i should . it 's quite moving , and quite ... quite stirring to be here in this place because this is where science and industry came together , for one of the earliest times i suppose . and quite a significant place of discovery and economic vibrancy for the local area . it 's almost spiritual , it 's really quite , quite different . what does it look like ? ytterbium , it depends on whether talk about metal or as an element . often , ytterbium 2 compounds as sort of yellows and oranges . where did i get it from ? from a catalogue . so ytterbium , it 's a rare earth element , it 's a metal . it 's a silvery lustrous metal . it 's very soft and it reacts very readily with oxygen to form a very nice protective oxide layer which sits over the metal . so it preserves itself after a reaction with oxygen . it was first identified or first isolated from a sample of a mineral which was recovered from this very quarry , where were in ytterby near stockholm in sweden . but it took a very long time to make that extraction and to purify the metal . it 's a rare earth element , it 's one of 15 . and it 's actually the least abandoned of the rare earths . but the name `` rare earth '' makes you think that it 's really rare . but if you look at its occurrence in the earth 's crust , it was a surprise to find that actually it 's twice as abundant as tin . but that said , total production of ytterbium is only 50 tons per year . so it 's still very little utilized , and that 's probably because its chemistry is least understood . and it 's least understood because we really are n't able to isolate significant meant of ytterbium in the late 1950s . like many other rare earth elements , it 's main applications lie in electronics industry . it 's used as a dopant for phosphorus , it 's used as a dopant for ceramic capacitors , and other electronic devices . so really niche applications , but research is broadening these applications day on day . the metal itself is really quite unusual because its properties change as a function of pressure . so it 's a metal , so it 's a conductor . but when you push it under extreme pressure , say 14,000 atmospheres of pressure , it becomes a semiconductor . and that semi conductor ability changes as a function of temperature so it 's used as a pressure sensor in extreme environments . and in fact , one of the major applications as an electronic devices for the monitoring sort of measurement of pressure especially within nuclear explosions . so quite a significant element , and quite a recent discovery . . . . . . . . . . . . . captions by www.subply.com
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stored in a very old glass bowl . ytterbium is one of three lanthanides , which was named after a swedish town called ytterby which is where they were all discovered . ytterbium , terbium and erbium were all derivatives of that town name .
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where was ytterbium discovered , together with two other lanthanides and yttrium ?
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when you think of natural history museums , you probably picture exhibits filled with ancient lifeless things , like dinosaurs meteroites , and gemstones . but behind that educational exterior , which only includes about 1 % of a museum 's collection , there are hidden laboratories where scientific breakthroughs are made . beyond the unmarked doors , and on the floors the elevators wo n't take you to , you 'd find windows into amazing worlds . this maze of halls and laboratories is a scientific sanctuary that houses a seemingly endless variety of specimens . here , researchers work to unravel mysteries of evolution , cosmic origins , and the history of our planet . one museum alone may have millions of specimens . the american museum of natural history in new york city has over 32,000,000 in its collection . let 's take a look at just one of them . scientists have logged exactly where and when it was found and used various dating techniques to pinpoint when it originated . repeat that a million times over , and these plants , animals , minerals , fossils , and artifacts present windows into times and places around the world and across billions of years of history . when a research problem emerges , scientists peer through these windows and test hypotheses about the past . for example , in the 1950s , populations of predatory birds , like peregrine falcons , owls , and eagles started to mysteriously crash , to the point where a number of species , including the bald eagle , were declared endangered . fortunately , scientists in the field museum in chicago had been collecting the eggs of these predatory birds for decades . they discovered that the egg shells used to be thicker and had started to thin around the time when an insecticide called ddt started being sprayed on crops . ddt worked very well to kill insects , but when birds came and ate those heaps of dead bugs , the ddt accumulated in their bodies . it worked its way up the food chain and was absorbed by apex predator birds in such high concentrations that it thinned their eggs so that they could n't support the nesting bird 's weight . there were omelettes everywhere until scientists from the field museum in chicago , and other institutions , helped solve the mystery and save the day . america thanks you , field museum . natural history museums windows into the past have solved many other scientific mysteries . museum scientists have used their collections to sequence the neanderthal genome , discover genes that gave mammoths red fur , and even pinpoint where ancient giant sharks gave birth . there are about 900 natural history museums in the world , and every year they make new discoveries and insights into the earth 's past , present and future . museum collections even help us understand how modern threats , such as global climate change , are impacting our world . for instance , naturalists have been collecting samples for over 100 years from walden pond , famously immortalized by henry david thoreau . thanks to those naturalists , who count thoreau among their number , we know that the plants around walden pond are blooming over three weeks earlier than they did 150 years ago . because these changes have taken place gradually , one person may not have noticed them over the span of a few decades , but thanks to museum collections , we have an uninterrupted record showing how our world is changing . so the next time you 're exploring a natural history museum , remember that what you 're seeing is just one gem of a colossal scientific treasure trove . behind those walls and under your feet are windows into forgotten worlds . and who knows ? one day some future scientist may peer through one and see you .
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here , researchers work to unravel mysteries of evolution , cosmic origins , and the history of our planet . one museum alone may have millions of specimens . the american museum of natural history in new york city has over 32,000,000 in its collection . let 's take a look at just one of them .
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what is a topic that a scientist in a natural history museum might study ?
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translator : andrea mcdonough reviewer : jessica ruby olive oil is 100 % fat ; there 's nothing else in it . pancake mix , on the other hand , is only about 11 % fat . and , yet , olive oil is good for you , and pancake mix is not . why is that ? as it turns out , the amount of fat we eat does n't impact our weight or our cholesterol or our risk of heart disease nearly as much as what kind of fat we eat . but let 's back up : what is fat ? if we were to zoom in on a salmon , which is a fatty fish , past the organs , past the tissues , into the cells , we would see that the stuff we call fat is actually made up of molecules called triglycerides , and they are not all alike . here 's one example . those three carbons on the left , that 's glycerol . now , you can think of that as the backbone that holds the rest of the molecule together . the three long chains on the right are called fatty acids , and it 's subtle differences in the structures of these chains that determine whether a fat is , let 's say , solid or liquid ; whether or not it goes rancid quickly ; and , most importantly , how good or how bad it is for you . let 's take a look at some of these differences . one is length . fatty acids can be short or long . another , more important difference is the type of bond between the carbon atoms . some fatty acids have only single bonds . others have both single and double bonds . fatty acids with only single bonds are called saturated , and those with one or more double bonds are called unsaturated . now , most unsaturated fats are good for you , while saturated fats are bad for you in excess . for saturated fats , the story pretty much ends there but not for unsaturated fats . the double bonds in these molecules have a kind of weird property ; they 're rigid . so , that means there are two ways to arrange every double bond . the first is like this , where both hydrogens are on same side and both carbons are on the same side . the second way is like this . now the hydrogens and carbons are on opposite sides of the double bond . now , even though both of these molecules are made up of exactly the same building blocks , they are two completely different substances , and they behave completely differently inside of us . the configuration on the left is called cis , which you 've probably never heard of . the one of the right is called trans , and you probably have heard of trans fats before . they do n't go rancid , they 're more stable during deep frying , and they can change the texture of foods in ways that other fats just ca n't . they 're also terrible for your health , by far worse than saturated fat , even though technically they 're a type of unsaturated fat . now , i know that seems crazy , but your body does n't care what a molecule looks like on paper . all that matters is the 3-d shape where the molecule fits , where it does n't , and what pathways it interferes with . so , how do you know if a food has trans fat in it ? well , the only sure way to know is if you see the words , `` partially hydrogenated '' in the ingredients list . do n't let nutrition labels or advertising fool you . the fda allows manufacturers to claim that their products contain `` 0 '' grams of trans fat even if they actually have up to half a gram per serving . but there are no hard and fast rules about how small a serving can be , and , that means , you 'll have to rely on seeing those key words , partially hydrogenated , because that 's how trans fats are made , by partially hydrogenating unsaturated fats . so , let 's go back to our olive oil and pancake mix from before . olive oil is 100 % fat . pancake mix is only 11 % fat . but olive oil is mostly unsaturated fat , and it has no trans fat at all . on the other hand , more than half the fat in pancake mix is either saturated or trans fat . and , so , even though olive oil has 10 times as much fat as pancake mix , it 's healthy for you , whereas pancake mix is not . now , i 'm not trying to pick on pancake mix . there are lots of foods with this type of fat profile . the point is this : it 's not how much fat you eat , it 's what kind of fat . and what makes a particular fat healthy or unhealthy is its shape .
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for saturated fats , the story pretty much ends there but not for unsaturated fats . the double bonds in these molecules have a kind of weird property ; they 're rigid . so , that means there are two ways to arrange every double bond .
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molecules are
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without a doubt , the most exciting scientific observation of 2012 was the discovery of a new particle at the cern laboratory that could be the higgs boson , a particle named after physicist peter higgs . the higgs field is thought to give mass to fundamental , subatomic particles like the quarks and leptons that make up ordinary matter . the higgs bosons are wiggles in the field , like the bump you see when you twitch a rope . but how does this field give mass to particles ? if this sounds confusing to you , you 're not alone . in 1993 , the british science minister challenged physicists to invent a simple way to understand all this higgs stuff . the prize was a bottle of quality champagne . the winning explanation went something like this : suppose there 's a large cocktail party at the cern laboratory filled with particle physics researchers . this crowd of physicists represents the higgs field . if a tax collector entered the party , nobody would want to talk to them , and they could very easily cross the room to get to the bar . the tax collector would n't interact with the crowd in much the same way that some particles do n't interact with the higgs field . the particles that do n't interact , like photons for example , are called massless . now , suppose that peter higgs entered the same room , perhaps in search of a pint . in this case , the physicists will immediately crowd around higgs to discuss with him their efforts to measure the properties of his namesake boson . because he interacts strongly with the crowd , higgs will move slowly across the room . continuing our analogy , higgs has become a massive particle through his interactions with the field . so , if that 's the higgs field , how does the higgs boson fit into all of this ? let 's pretend our crowd of party goers is uniformly spread across the room . now suppose someone pops their head in the door to report a rumor of a discovery at some distant , rival laboratory . people near the door will hear the rumor , but people far away wo n't , so they 'll move closer to the door to ask . this will create a clump in the crowd . as people have heard the rumor , they will return to their original positions to discuss its implications , but people further away will then ask what 's going on . the result will be a clump in the crowd that moves across the room . this clump is analogous to the higgs boson . it is important to remember that it is not that massive particles interact more with the higgs field . in our analogy of the party , all particles are equal until they enter the room . both peter higgs and the tax collector have zero mass . it is the interaction with the crowd that causes them to gain mass . i 'll say that again . mass comes from interactions with a field . so , let 's recap . a particle gets more or less mass depending on how it interacts with a field , just like different people will move through the crowd at different speeds depending on their popularity . and the higgs boson is just a clump in the field , like a rumor crossing the room . of course , this analogy is just that -- an analogy , but it 's the best analogy anyone has come up with so far . so , that 's it . that 's what the higgs field and the higgs boson is all about . continuing research will tell us if we found it , and the reward will probably be more than just a bottle of champagne .
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without a doubt , the most exciting scientific observation of 2012 was the discovery of a new particle at the cern laboratory that could be the higgs boson , a particle named after physicist peter higgs . the higgs field is thought to give mass to fundamental , subatomic particles like the quarks and leptons that make up ordinary matter . the higgs bosons are wiggles in the field , like the bump you see when you twitch a rope .
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the higgs field gives subatomic particles their
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they say , 'time is money , ' but what does one really have to do with the other ? meet sheila ! she just got her first big bonus . sheila knows exactly what she wants to do with that money . she 's had her eye on a nice convertible for a while now . yes , sheila , that 's a nice car ! oh , looks like sheila is a little short . but wait ! she has an idea . sheila is a smart cookie . she knows that if she deposits the money for a year instead of buying the car today , she will earn interest . then she 'll be able to afford the car . sheila knows that the value of her deposit one year from now will equal the money deposited today plus the interest earned . we call sheila 's money deposited today the present value of money . and the value of sheila 's deposit next year is the future value of money . what connects one to the other ? the interest rate , also known as the time value of money . now , with a little bit of rearranging , we can figure out the future value of sheila 's money with this equation . so in a year , the future value will be $ 11,000 . well , it 's been a year ! and there 's sheila , with enough money to buy the car . sheila really understands the future value of money . now , i just hope she understands the speed limit ! now , meet timmy . he 's also gotten his bonus . the money seems to be burning a hole in his pocket . yes , timmy , that 's a nice car that will surely impress people . oh ! looks like you 're a little short . maybe you can follow sheila 's example . you see , timmy , just like sheila , after the first year , you 'll have $ 11,000 . but timmy , that is still not enough to buy that fancy car . why do n't you leave the money deposited for another year ? let 's see how your deposit will be doing in two years . with a little bit of rearranging , it becomes the value of your money next year , times one plus the interest rate . we can then convert the future value one year from now to the present value times one plus the interest rate . we can even simplify this further by just squaring the value of one plus the interest rate . sorry , timmy , you 'll have more money after two years , but you still ca n't afford the car ! i do n't know how many more years you 'll have to wait , but i can tell you one way we can figure it out . do you see that little number two in the equation ? any number that you put in there is the number of years that you are waiting , also known as the period . sure , timmy , we can see how much you 'll have in five years . let 's connect future value and present value across five years . let 's watch the period increase from two to five . after 5 years , you 'll have $ 16,105.10 . sorry , timmy , you have to wait a little longer . 10 years ? yeah ! let 's see if you 'll be able to buy the car then . not quite . well , timmy , it looks like you 'll need 26 years to afford this car . you should ask sheila for a ride to the beach . maybe a bicycle will suit you better ? i hear the bus is pretty cheap !
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do you see that little number two in the equation ? any number that you put in there is the number of years that you are waiting , also known as the period . sure , timmy , we can see how much you 'll have in five years .
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the number of years of a particular investment is also known as ________ .
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flying through the night , i watch over this world , a silent guardian , a watchful protector , a dark knight , i 'm ... okay , fine . so , i 'm not batman . i 'm just a bat . but like batman , i 'm often misunderstood . people think i 'm scary , strange and dangerous . if they only knew my story , though , i 'd be cheered as a hero . when people think of bats , many think of vampires who want to suck their blood . but the truth is that out of over 1200 bat species , only three are vampire bats . out of these three , only one prefers the blood of mammals , and even these bats mostly feed on cattle . maybe that still does n't seem so great , but vampire bats can be a great help to humans . a chemical known as desmoteplase found in vampire bat saliva helps break down blood clots , and is being tested by recovering stroke victims . of the remaining 1000+ species of bats , about 70 % feed on insects . these bats help control the real vampires : mosquitos , whose nasty bites are not just annoying but spread diseases , like west nile virus . a single little brown bat can eat 1000 insects every hour , and a colony of mexican free-tailed bats can eat several tons of moths in just one night . in the united states alone , bats provide an estimated 3.7 billion dollars worth of free pest control for farmers , which benefits everyone who eats the foods that they grow . fruit bats , also called megabats because of their large size , are important for the role they play in plant pollination . by traveling between flowers while feeding on nectar and fruits , these bats transport the pollen and seeds that help plants reproduce . in southeast asia , for example , the cave nectar bat is the only pollinator of the durian fruit . other bats pollinate peaches , bananas , and the agave plants that tequila is made from . without them , many of our food plants would be unable to produce the tasty fruits we enjoy . as heroes of the ecosystem , bats have their own unique utility belts . bats have been a source of inspiration for the design of flying robots and even an energy-efficient spy plane , as they are the only mammal capable of true powered flight . echolocation , a type of biological sonar , is also used by bats as a way to navigate and find prey in the dark . although there 's a common misconception that bats are blind , in truth , all species of bats have sight . and some have even adapted large eyes to see better in dim lighting . many people worry about getting infected by bats , and like any other animals , bats can carry diseases , like rabies . in reality , though , less than .5 % of all bats carry this virus . that 's about the same odds as getting the same result on a coin flip eight times in a row . the perception that bats are often diseased may come from the fact that sick bats , who may show unusual behavior , emerge during the daytime , or be unable to fly , are more likely to be encountered by people . so a good way to protect yourself is to protect bats as well , keeping them healthy , protecting their habitats , and reducing their risk of transmitting disease . in north america , bats are threatened by a devastating sickness called white-nose syndrome . this fungal infection causes bats to wake up while hibernating during a winter . unable to find food , they expend large amounts of energy , and eventually starve to death . white-nose syndrome has wiped out entire caves full of bats , with a mortality rate that can exceed 90 % . climate change and habitat destruction also pose serious threats to bat populations . for example , in january 2014 , a record heat wave in australia caused over 100,000 bats to die from heat exhaustion . some people just want to watch the world burn , and bats all over the world are threatened by damage to the places that we call home , including mangrove swamps , old-growth forests , and , of course , bat caves . so even though i 'm the hero of the story , i do need to be saved . and now that you know the true story about us bats , you can learn how to protect such heroic animals . install a properly designed bat box , one of the easiest ways to provide shelter for bats . discourage the use of pesticides , which can harm bats when we try to feed on the insects you want to get rid of in the first place . avoid going into caves where you might disturb hibernating bats , and always decontaminate your gear after visiting a cave . if you have unwanted bats living in an attic or barn , contact your local government to safely and humanely relocate us . and if you come across a bat , do not attempt to handle it , but instead , call animal control . batman might want to keep his identity secret , but a great way to help real bats is by continuing to learn about them and spreading the truth that they are real heroes , even if their good deeds are often unseen .
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and now that you know the true story about us bats , you can learn how to protect such heroic animals . install a properly designed bat box , one of the easiest ways to provide shelter for bats . discourage the use of pesticides , which can harm bats when we try to feed on the insects you want to get rid of in the first place .
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explain two ways that bats provide help for farmers who grow food plants .
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it 's 4 a.m. , and the big test is in eight hours , followed by a piano recital . you 've been studying and playing for days , but you still do n't feel ready for either . so , what can you do ? well , you can drink another cup of coffee and spend the next few hours cramming and practicing , but believe it or not , you might be better off closing the books , putting away the music , and going to sleep . sleep occupies nearly a third of our lives , but many of us give surprisingly little attention and care to it . this neglect is often the result of a major misunderstanding . sleep is n't lost time , or just a way to rest when all our important work is done . instead , it 's a critical function , during which your body balances and regulates its vital systems , affecting respiration and regulating everything from circulation to growth and immune response . that 's great , but you can worry about all those things after this test , right ? well , not so fast . it turns out that sleep is also crucial for your brain , with a fifth of your body 's circulatory blood being channeled to it as you drift off . and what goes on in your brain while you sleep is an intensely active period of restructuring that 's crucial for how our memory works . at first glance , our ability to remember things does n't seem very impressive at all . 19th century psychologist herman ebbinghaus demonstrated that we normally forget 40 % of new material within the first twenty minutes , a phenomenon known as the forgetting curve . but this loss can be prevented through memory consolidation , the process by which information is moved from our fleeting short-term memory to our more durable long-term memory . this consolidation occurs with the help of a major part of the brain , known as the hippocampus . its role in long-term memory formation was demonstrated in the 1950s by brenda milner in her research with a patient known as h.m. after having his hippocampus removed , h.m. 's ability to form new short-term memories was damaged , but he was able to learn physical tasks through repetition . due to the removal of his hippocampus , h.m. 's ability to form long-term memories was also damaged . what this case revealed , among other things , was that the hippocampus was specifically involved in the consolidation of long-term declarative memory , such as the facts and concepts you need to remember for that test , rather than procedural memory , such as the finger movements you need to master for that recital . milner 's findings , along with work by eric kandel in the 90 's , have given us our current model of how this consolidation process works . sensory data is initially transcribed and temporarily recorded in the neurons as short-term memory . from there , it travels to the hippocampus , which strengthens and enhances the neurons in that cortical area . thanks to the phenomenon of neuroplasticity , new synaptic buds are formed , allowing new connections between neurons , and strengthening the neural network where the information will be returned as long-term memory . so why do we remember some things and not others ? well , there are a few ways to influence the extent and effectiveness of memory retention . for example , memories that are formed in times of heightened feeling , or even stress , will be better recorded due to the hippocampus ' link with emotion . but one of the major factors contributing to memory consolidation is , you guessed it , a good night 's sleep . sleep is composed of four stages , the deepest of which are known as slow-wave sleep and rapid eye movement . eeg machines monitoring people during these stages have shown electrical impulses moving between the brainstem , hippocampus , thalamus , and cortex , which serve as relay stations of memory formation . and the different stages of sleep have been shown to help consolidate different types of memories . during the non-rem slow-wave sleep , declarative memory is encoded into a temporary store in the anterior part of the hippocampus . through a continuing dialogue between the cortex and hippocampus , it is then repeatedly reactivated , driving its gradual redistribution to long-term storage in the cortex . rem sleep , on the other hand , with its similarity to waking brain activity , is associated with the consolidation of procedural memory . so based on the studies , going to sleep three hours after memorizing your formulas and one hour after practicing your scales would be the most ideal . so hopefully you can see now that skimping on sleep not only harms your long-term health , but actually makes it less likely that you 'll retain all that knowledge and practice from the previous night , all of which just goes to affirm the wisdom of the phrase , `` sleep on it . '' when you think about all the internal restructuring and forming of new connections that occurs while you slumber , you could even say that proper sleep will have you waking up every morning with a new and improved brain , ready to face the challenges ahead .
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so hopefully you can see now that skimping on sleep not only harms your long-term health , but actually makes it less likely that you 'll retain all that knowledge and practice from the previous night , all of which just goes to affirm the wisdom of the phrase , `` sleep on it . '' when you think about all the internal restructuring and forming of new connections that occurs while you slumber , you could even say that proper sleep will have you waking up every morning with a new and improved brain , ready to face the challenges ahead .
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provide evidence to support the statement that `` we wake up each morning with a new brain . ''
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translator : andrea mcdonough reviewer : bedirhan cinar 9th of january , 2007 joshua bell , one of the greatest violinist in the world , played to a packed audience at boston 's stately symphony hall of 1,000 people where most seats went for more than $ 100 . he was used to full , sell-out shows . he was at the peak of his abilities and fame . three days later , joshua bell played to an audience of nobody ! well , maybe six people paused for a moment , and one child stopped for a while looking , as if he understood that something special was happening . joshua said of the experience , `` it was a strange feeling that people were actually ignoring me . '' joshua bell was playing violin in a subway station . `` at a music hall , i 'll get upset if someone coughs or if someone 's cell phone goes off , but here my expectations quickly diminished . i was oddly grateful when somebody threw in a dollar . '' what changed ? same music , on the same violin , played with the same passion and by the same man . why did people listen and then not listen ? aristotle would be able to explain . what does it take to persuade people ? 2,300 years ago , aristotle wrote the single most important work on persuasion , < i > rhetoric < /i > , the 3 means of persuasion : logos , ethos , and pathos . logos is that the idea makes sense from the audience 's point of view . this is usually different from the speaker 's point of view , so work needs to be done to make the idea relevant to the world view , the pains and the challenges of the listeners . a good argument is like good music . good music follows some rules of composition ; good arguments follow some rules of logic . it makes sense to the audience . ethos is reputation , what are you known for ; credibility , do you look and act professional ; trustworthy , are your motives clear , do you show the listener that you care about them as much as yourself ? authority is confidence plus a concise message , a clear , strong voice . pathos is the emotional connection . stories are an effective human tool for creating an emotional connection . there are moments where an audience is not ready to hear the message . a speaker must create the right emotional environment for their message . what changed ? why did people travel for miles to hear him play one night , and not even pause for moment to listen the next morning ? the answer is that ethos and pathos were missing . ethos the fact that the great concert hall hosts joshua 's concert transfers its trust to joshua . we trust the institution , we now trust joshua . the subway does not have our trust for musical talent , we do not expect to find great art , great music , or great ideas , so it confers no trust to joshua . pathos the concert hall is designed for an emotional bond between an audience and an artist , a subway platform is not . the hustle and movement and stress is just not conducive to the emotional connection needed between performer and listener . logos , ethos , pathos , the idea is nothing without the rest . this is what joshua bell learned on that cold , january day in 2007 . if you have a great idea , how do you build credibility and emotional connection ?
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translator : andrea mcdonough reviewer : bedirhan cinar 9th of january , 2007 joshua bell , one of the greatest violinist in the world , played to a packed audience at boston 's stately symphony hall of 1,000 people where most seats went for more than $ 100 . he was used to full , sell-out shows .
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where did joshua bell play for an audience of 1,000 people where most seats went for $ 100 ?
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is teleportation possible ? could a baseball transform into something like a radio wave , travel through buildings , bounce around corners , and change back into a baseball ? oddly enough , thanks to quantum mechanics , the answer might actually be yes . sort of . here 's the trick . the baseball itself could n't be sent by radio , but all the information about it could . in quantum physics , atoms and electrons are interpreted as a collection of distinct properties , for example , position , momentum , and intrinsic spin . the values of these properties configure the particle , giving it a quantum state identity . if two electrons have the same quantum state , they 're identical . in a literal sense , our baseball is defined by a collective quantum state resulting from its many atoms . if this quantum state information could be read in boston and sent around the world , atoms for the same chemical elements could have this information imprinted on them in bangalore and be carefully directed to assemble , becoming the exact same baseball . there 's a wrinkle though . quantum states are n't so easy to measure . the uncertainty principle in quantum physics implies the position and momentum of a particle ca n't be measured at the same time . the simplest way to measure the exact position of an electron requires scattering a particle of light , a photon , from it , and collecting the light in a microscope . but that scattering changes the momentum of the electron in an unpredictable way . we lose all previous information about momentum . in a sense , quantum information is fragile . measuring the information changes it . so how can we transmit something we 're not permitted to fully read without destroying it ? the answer can be found in the strange phenomena of quantum entanglement . entanglement is an old mystery from the early days of quantum physics and it 's still not entirely understood . entangling the spin of two electrons results in an influence that transcends distance . measuring the spin of the first electron determines what spin will measure for the second , whether the two particles are a mile or a light year apart . somehow , information about the first electron 's quantum state , called a qubit of data , influences its partner without transmission across the intervening space . einstein and his colleagues called this strange communcation spooky action at a distance . while it does seem that entanglement between two particles helps transfer a qubit instantaneously across the space between them , there 's a catch . this interaction must begin locally . the two electrons must be entangled in close proximity before one of them is transported to a new site . by itself , quantum entanglement is n't teleportation . to complete the teleport , we need a digital message to help interpret the qubit at the receiving end . two bits of data created by measuring the first particle . these digital bits must be transmitted by a classical channel that 's limited by the speed of light , radio , microwaves , or perhaps fiberoptics . when we measure a particle for this digital message , we destroy its quantum information , which means the baseball must disappear from boston for it to teleport to bangalore . thanks to the uncertainty principle , teleportation transfers the information about the baseball between the two cities and never duplicates it . so in principle , we could teleport objects , even people , but at present , it seems unlikely we can measure the quantum states of the trillion trillion or more atoms in large objects and then recreate them elsewhere . the complexity of this task and the energy needed is astronomical . for now , we can reliably teleport single electrons and atoms , which may lead to super-secured data encryption for future quantum computers . the philosophical implications of quantum teleportation are subtle . a teleported object does n't exactly transport across space like tangible matter , nor does it exactly transmit across space , like intangible information . it seems to do a little of both . quantum physics gives us a strange new vision for all the matter in our universe as collections of fragile information . and quantum teleportation reveals new ways to influence this fragility . and remember , never say never . in a little over a century , mankind has advanced from an uncertain new understanding of the behavior of electrons at the atomic scale to reliably teleporting them across a room . what new technical mastery of such phenomena might we have in 1,000 , or even 10,000 years ? only time and space will tell .
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measuring the spin of the first electron determines what spin will measure for the second , whether the two particles are a mile or a light year apart . somehow , information about the first electron 's quantum state , called a qubit of data , influences its partner without transmission across the intervening space . einstein and his colleagues called this strange communcation spooky action at a distance .
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in a quantum teleport , it 's the quantum state that gives an electron its unique identity ; this identity is transferred from an electron located at an initial location in space to another electron located at the final location . if it were possible today for a human being—whose body is made up of an enormous collection of atomic particles—to teleport , would the being who stepped out of a so-called teleporter at the final location still be the same person ?
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translator : tom carter reviewer : bedirhan cinar take an adjective such as `` implacable , '' or a verb like `` proliferate , '' or even another noun , `` crony , '' and add a suffix , such as `` -ity , '' or `` -tion , '' or `` -ism . '' you 've created a new noun . `` implacability , '' `` proliferation , '' `` cronyism . '' sounds impressive , right ? wrong ! you 've just unleashed a flesh-eating zombie . nouns made from other parts of speech are called nominalizations . academics love them . so do lawyers , bureaucrats , business writers . i call them zombie nouns , because they consume the living . they cannibalize active verbs , they suck the lifeblood from adjectives , and they substitute abstract entities for human beings . here 's an example . `` the proliferation of nominalizations in a discursive formation may be an indication of a tendency towards pomposity and abstraction . '' huh ? this sentence contains no fewer than seven nominalizations , yet it fails to tell us who is doing what . when we eliminate , or reanimate , most of the zombie nouns , so `` tendency '' becomes `` tend , '' `` abstraction '' becomes `` abstract , '' then we add a human subject and some active verbs , the sentence springs back to life . `` writers who overload their sentences with nominalizations tend to sound pompous and abstract . '' only one zombie noun -- the key word `` nominalizations '' -- has been allowed to remain standing . at their best , nominalizations help us express complex ideas , perception , intelligence , epistemology . at their worst , they impede clear communication . to get a feeling for how zombie nouns work , release a few of them into a lively sentence and watch them sap all its energy . george orwell played this game in his essay `` politics in the english language . '' he started with a well-known verse from the book of ecclesiastes in the bible . it says `` i returned and saw under the sun , that the race is not to the swift , nor the battle to the strong , neither yet bread to the wise , nor yet riches to men of understanding , nor yet favor to men of skill ; but time and chance happeneth to them all . '' now here 's orwell 's modern english version . `` objective considerations of contemporary phenomena compel the conclusion that success or failure in competitive activities exhibits no tendency to be commensurate with innate capacity , but that a considerable element of the unpredictable must invariably be taken into account . '' the bible passage speaks to our senses and emotions with concrete nouns , descriptions of people , and punchy , abstract nouns such as `` race , '' `` battle , '' `` riches , '' `` time , '' `` chance . '' not a zombie among them . orwell 's satirical translation , on the other hand , is teeming with nominalizations and other vague abstractions . the zombies have taken over , and the humans have fled the village . zombie nouns do their worst damage when they gather in jargon-generating packs and swallow every noun , verb and adjective in sight . so `` globe '' becomes `` global , '' becomes `` globalize , '' becomes `` globalization . '' the grandfather of all nominalizations , antidisestablishmentarianism , contains at least two verbs , three adjectives , and six other nouns inside its distended belly . a paragraph heavily populated by nominalizations will send your readers straight to sleep . rescue them from the zombie apocalypse with vigorous verb-driven sentences that are concrete and clearly structured . you want your sentences to live , not to join the living dead .
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to get a feeling for how zombie nouns work , release a few of them into a lively sentence and watch them sap all its energy . george orwell played this game in his essay `` politics in the english language . '' he started with a well-known verse from the book of ecclesiastes in the bible .
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george orwell rewrote a passage from ecclesiastes because he wanted to
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it 's estimated that for every 10,000 bills in the u.s. , one of those bills is fake . that may not sound like much , but it adds up to millions of dollars in cold hard cash . counterfeit money has the potential to cause all sorts of problems , from leaving you short $ 20 to destabilizing national economies . but do n't worry . you can help catch the counterfeits . all you need are some simple tools and a bit of chemistry . first up , the anti-counterfeit detection pen . the pen looks like a highlighter and contains a solution of potassium iodide and elemental iodine . it reveals of the presence of starch , which is commonly used to strengthen regular printer paper , but wo n't be found in real money . that 's because authentic bills are made of cotton and linen and are threaded with tiny red and blue fibers . that material is made by a single , highly-guarded company called crane and company , which has been printing currency since paul revere asked them to help finance the revolutionary war . the starch in many counterfeit bills , on the other hand , is made of two molecules : amylopectin and amylose . it 's amylose that gives the fake away . its long chain of sugar molecules connected by oxygen atoms forms a helical structure , like dna . iodide likes to squeeze inside this coil , forming a new compound that leaves a dark mark on the paper . however , in the absence of starch , there is no chemical reaction and the mark will look light yellow . so if the fake is n't printed on starchy paper , iodine solutions ca n't help you . that 's one of the reasons u.s. bills printed since 1996 have been chemically enhanced to include another counterfeit countermeasure : a strip that fluoresces under uv light . that 's the same kind of light used at black light parties and airport security lines . the polyester strip printed with invisble ink is just one millimeter wide and is found in different positions depending on a bill 's value . if you hold your dollar up to natural light , you can see the amount and the word usa printed on the band . but under uv light , these strips really shine . they contain molecules that can be excited by absorbing certain amounts of energy , specifically , that given off by common uv light sources . as these excited molecules return to their original states , they lose a bit of energy as heat and then radiate the rest as light . energy is inversely related to wavelength , which means that the longer wavelengths have lower energy . so the lower energy light given off by the strip means longer wavelengths that fall in the visible range , and suddenly we can see that which had been invisible . and if a glowing strip does n't show up on a recent bill , you have a fake on your hands . for times when you 're not dealing with counterfeit masterminds , looking for simple visual cues will do . make sure the portrait looks lifelike and not flat , the seal has perfectly even sawtooth points , the inked border is unbroken , and the serial number has precisely equal spacing between each number . so the next time you come across some dubious dough , have a closer look , pull out your iodine solution , or take it to a rave and you just might catch a counterfeit .
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all you need are some simple tools and a bit of chemistry . first up , the anti-counterfeit detection pen . the pen looks like a highlighter and contains a solution of potassium iodide and elemental iodine .
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the counterfeit detection pen detects a counterfeit by leaving a dark mark on a bill when a reaction occurs between _____ and _____ .
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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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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 .
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all of the following are examples of fermented foods except :
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nothing stuck to mafia boss john gotti who evaded justice for years by bribing and threatening jurors and witnesses . that earned him the name the teflon don after one of the slipperiest materials on earth . teflon was in the spacesuits the apollo crew wore for the moon landing , in pipes and valves used in the manhattan project , and maybe in your kitchen as the nonstick coating on frying pans and cookie sheets . so what is this slippery solid , and why does n't anything stick to it ? teflon is a brand name for polytetrafluoroethylene , or ptfe . it was stumbled upon accidentally in 1938 by a 27-year-old american chemist named roy plunkett while he was trying to develop a non-toxic refrigerant fluid for dupont , a chemicals company . the strange , white substance that formed inside his lab canister was chemically inert , meaning it would n't react with other substances . it also had an extremely low coefficient of friction , making other materials slide right off it . teflon 's properties make it perfect when you need something slippery , chemical resistant , or waterproof , which means it has a lot of applications . it can be found all over the place , as a coating on raincoats , industrial ball bearings , artificial joints , circuit boards , and even the rocky mountains-themed roof of the denver international airport . the incredible properties of ptfe come from its molecular structure . it 's a polymer , meaning it 's made of long chains of repeating units of atoms strung together . a ptfe chain has a backbone of carbon atoms , each of which is attached to two fluorines . the fluorine atoms surround the carbon like armor , spiraling around the chain , and the bond between carbon and fluorine is incredibly tight . like a couple that ignores everyone except each other , carbon and fluorine interact so strongly that the normal , intermolecular forces that help substances stick to each other do n't stand a chance . even the famously adhesive feet of geckos usually ca n't get a grip . but wait ! if ptfe does n't stick to anything , how can it be so firmly attached to something like a pan ? one method involves sandblasting the pan or etching it with chemicals to make it rough . then , a special primer is applied , which acts like glue . its exact composition is a trade secret guarded by each manufacturer . the pan is sprayed with liquid ptfe and heated to around 800 degrees fahrenheit . the layers then solidify into a smooth , slick coating . when you later cook eggs in this ptfe-coated pan , the extra tight carbon-fluorine bonds just ignore the water and fat and protein molecules in the eggs . without those interactions , the food just slides around without sticking . you might wonder if it 's safe to cook in a ptfe-coated pan . the answer is yes , if you 're careful . ptfe is stable at moderate temperatures , like you 'd use to cook eggs or fish , but above 500 degrees fahrenheit , it starts to degrade , and heating it further releases fumes that can make you feel sick . an empty pan can reach 500 degrees fast over high heat , but most kitchens are ventilated well enough to dissipate the fumes . people used to also think that accidentally consuming ptfe that flaked off a scratched pan was bad for you , but the current consensus is that it 's harmless . because ptfe does n't interact with other chemicals very well , it is n't thought to break down inside your body . whether it 's safe to manufacture teflon is another story . dupont and its spin-off company chemours now face lawsuits worth millions of dollars . they 've been accused of polluting the environment for decades and exposing employees and local communities to health risks associated with a toxic chemical called pfoa . that chemical was involved in manufacturing teflon . as for john gotti , in 1992 , the mob boss was finally convicted of five counts of murder , among other charges . that prompted the head of the fbi office in new york city to announce , `` the teflon is gone . the don is covered in velcro , and all the charges stuck . ''
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they 've been accused of polluting the environment for decades and exposing employees and local communities to health risks associated with a toxic chemical called pfoa . that chemical was involved in manufacturing teflon . as for john gotti , in 1992 , the mob boss was finally convicted of five counts of murder , among other charges .
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take some time and list the various used that teflon has had . is its production worth its impact on the environment ? what should be done ?
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a lone priestess walks towards an underground chamber . people line the streets to watch as she proclaims her innocence . it does n't matter . she 's already been judged and found guilty . the sentence ? live burial . the underground chamber contains a portion of bread , water , milk , and oil . she will have a lamp , a bed , and a blanket , but she wo n't emerge alive . at the threshold , the priestess pauses , claims her innocence one last time , then enters the chamber never to be seen again by the roman people . the priestess is one of rome 's six vestal virgins , each carefully selected as children from rome 's most aristocratic families . but now with her death , there are only five , and a new priestess must be chosen . the six-year-old licinia witnessed the spectacle , never suspecting that a few days later , she 'd be chosen as the next vestal virgin . her age , her patrician family lineage , and her apparent good health makes her the best candidate to serve the goddess vesta in the eyes of the romans . her parents are proud that their daughter 's been chosen . licinia is afraid , but she has no choice in the matter . she must serve the goddess for at least the next 30 years . for the first ten years of licinia 's service , she 's considered in training , learning how to be a vestal virgin . her most important duty is keeping vigil over the flame of vesta , the virgin goddess of the hearth . vesta does n't have a statue like other roman gods and goddesses . instead , she 's represented by the flame which burns day and night in her temple located next to the forum in the center of the city . like all vestal priestesses , licinia spends part of each day on shift , watching and tending to the flame . the flame represents two things . the first is the continuation of rome as a power in the world . the romans believed that if the flame goes out , the city 's in danger . the flame also symbolizes the continuing virginity of vesta 's priestesses . for the romans , a vestal 's virginity signaled not only her castitas , or modest spirit and body , but also her ritual purity . so licinia knows she must never let the flame go out . her life , the lives of her fellow vestals , and the safety of rome itself depends upon it . licinia learns to collect water each day from a nearby fountain to cleanse the temple . she learns the fasti , the calendar of sacred rituals and she watches while the senior priestesses conduct sacrifices . by the time licinia completes her training , she 's 16 years old . licinia understands that the way she must act is a reflection of the goddess she serves . when it 's her turn to collect the water , she keeps her eyes lowered to the ground . when she performs sacrifices , she focuses intently on the task . licinia directs her energy towards being the best priestess she can be . she 's worried that someday the state will claim her life for its own purposes to protect itself from danger . licinia could be accused of incestum , meaning unchastity , at any time and be sacrificed whether she 's innocent or guilty . licinia fully understands now why her predecessor was buried alive . ten years ago , the flame of vesta went out . the priestesses knew that they could n't keep it a secret . the future of rome depended upon it . they went to the chief priest and he opened an investigation to discover why the flame had failed . someone came forward and claimed that one of the vestals was no longer a virgin . that was the beginning of the end . the accused protested her innocence , but it was n't enough . she was tried and found guilty . that vestal 's death was meant to protect the city , but licinia weeps for what has been lost and for what she knows now . her own path was paved by the death of another , and her life could be taken just as easily for something as simple as a flame going out .
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she must serve the goddess for at least the next 30 years . for the first ten years of licinia 's service , she 's considered in training , learning how to be a vestal virgin . her most important duty is keeping vigil over the flame of vesta , the virgin goddess of the hearth .
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what is the minimum length of service for a vestal virgin ?
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what 's your sign ? in western astrology , it 's a constellation determined by when your birthday falls in the calendar . but according to the chinese zodiac , or shēngxiào , it 's your shǔxiàng , meaning the animal assigned to your birth year . and of the many myths explaining these animal signs and their arrangement , the most enduring one is that of the great race . as the story goes , yù dì , or jade emperor , ruler of the heavens , wanted to devise a way to measure time , so he organized a race . the first twelve animals to make it across the river would earn a spot on the zodiac calendar in the order they arrived . the rat rose with the sun to get an early start , but on the way to the river , he met the horse , the tiger , and the ox . because the rat was small and could n't swim very well , he asked the bigger animals for help . while the tiger and horse refused , the kind-hearted ox agreed to carry the rat across . yet , just as they were about to reach the other side , the rat jumped off the ox 's head and secured first place . the ox came in second , with the powerful tiger right behind him . the rabbit , too small to battle the current , nimbly hopped across stones and logs to come in fourth . next came the dragon , who could have flown directly across , but stopped to help some creatures she had encountered on the way . after her came the horse , galloping across the river . but just as she got across , the snake slithered by . the startled horse reared back , letting the snake sneak into sixth place . the jade emperor looked out at the river and spotted the sheep , the monkey , and the rooster all atop a raft , working together to push it through the weeds . when they made it across , the trio agreed to give eighth place to the sheep , who had been the most comforting and harmonious of them , followed by the monkey and the rooster . next came the dog , scrambling onto the shore . he was a great swimmer , but frolicked in the water for so long that he only managed to come in eleventh . the final spot was claimed by the pig , who had gotten hungry and stopped to eat and nap before finally waddling across the finish line . and so , each year is associated with one of the animals in this order , with the cycle starting over every 60 years . why 60 and not twelve ? well , the traditional chinese calendar is made up of two overlapping systems . the animals of the zodiac are associated with what 's called the twelve earthly branches , or shí'èrzhī . another system , the ten heavenly stems , or tiāngān , is linked with the five classical elements of metal , xīn , wood , mù , water , shuǐ , fire , huǒ , and earth , tǔ . each element is assigned yīn or yáng , creating a ten-year cycle . when the twelve animals of the earthly branches are matched with the five elements plus the yīn or the yáng of the heavenly stems , it creates 60 years of different combinations , known as a sexagenary cycle , or gānzhī . so someone born in 1980 would have the sign of yáng metal monkey , while someone born in 2007 would be yīn fire pig . in fact , you can also have an inner animal based on your birth month , a true animal based on your birth date , and a secret animal based on your birth hour . it was the great race that supposedly determined which animals were enshrined in the chinese zodiac , but as the system spread through asia , other cultures made changes to reflect their communities . so if you consult the vietnamese zodiac , you may discover that you 're a cat , not a rabbit , and if you 're in thailand , a mythical snake called a naga replaces the dragon . so whether or not you place stock in what the zodiac says about you as an individual , it certainly reveals much about the culture it comes from .
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in western astrology , it 's a constellation determined by when your birthday falls in the calendar . but according to the chinese zodiac , or shēngxiào , it 's your shǔxiàng , meaning the animal assigned to your birth year . and of the many myths explaining these animal signs and their arrangement , the most enduring one is that of the great race .
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what are the five elements of the chinese zodiac ?
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if you tried to pay for something with a piece of paper , you might run into some trouble . unless , of course , the piece of paper was a hundred dollar bill . but what is it that makes that bill so much more interesting and valuable than other pieces of paper ? after all , there 's not much you can do with it . you ca n't eat it . you ca n't build things with it . and burning it is actually illegal . so what 's the big deal ? of course , you probably know the answer . a hundred dollar bill is printed by the government and designated as official currency , while other pieces of paper are not . but that 's just what makes them legal . what makes a hundred dollar bill valuable , on the other hand , is how many or few of them are around . throughout history , most currency , including the us dollar , was linked to valuable commodities and the amount of it in circulation depended on a government 's gold or silver reserves . but after the us abolished this system in 1971 , the dollar became what is known as fiat money , meaning not linked to any external resource but relying instead solely on government policy to decide how much currency to print . which branch of our government sets this policy ? the executive , the legislative , or the judicial ? the surprising answer is : none of the above ! in fact , monetary policy is set by an independent federal reserve system , or the fed , made up of 12 regional banks in major cities around the country . its board of governors , which is appointed by the president and confirmed by the senate , reports to congress , and all the fed 's profit goes into the us treasury . but to keep the fed from being influenced by the day-to-day vicissitudes of politics , it is not under the direct control of any branch of government . why does n't the fed just decide to print infinite hundred dollar bills to make everyone happy and rich ? well , because then the bills would n't be worth anything . think about the purpose of currency , which is to be exchanged for goods and services . if the total amount of currency in circulation increases faster than the total value of goods and services in the economy , then each individual piece will be able to buy a smaller portion of those things than before . this is called inflation . on the other hand , if the money supply remains the same , while more goods and services are produced , each dollar 's value would increase in a process known as deflation . so which is worse ? too much inflation means that the money in your wallet today will be worth less tomorrow , making you want to spend it right away . while this would stimulate business , it would also encourage overconsumption , or hoarding commodities , like food and fuel , raising their prices and leading to consumer shortages and even more inflation . but deflation would make people want to hold onto their money , and a decrease in consumer spending would reduce business profits , leading to more unemployment and a further decrease in spending , causing the economy to keep shrinking . so most economists believe that while too much of either is dangerous , a small , consistent amount of inflation is necessary to encourage economic growth . the fed uses vast amounts of economic data to determine how much currency should be in circulation , including previous rates of inflation , international trends , and the unemployment rate . like in the story of goldilocks , they need to get the numbers just right in order to stimulate growth and keep people employed , without letting inflation reach disruptive levels . the fed not only determines how much that paper in your wallet is worth but also your chances of getting or keeping the job where you earn it .
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think about the purpose of currency , which is to be exchanged for goods and services . if the total amount of currency in circulation increases faster than the total value of goods and services in the economy , then each individual piece will be able to buy a smaller portion of those things than before . this is called inflation .
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if the total amount of currency circulating increases faster than the total value of goods and services in the economy that is referred to as :
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somewhere right now , people are lining up to scare themselves , maybe with a thrill ride or horror movie . in fact , in october of 2015 alone , about 28 million people visited a haunted house in the u.s . but many consider this behavior perplexing , asking the question , `` what could possibly be fun about being scared ? '' fear has a bad rap , but it 's not all bad . for starters , fear can actually feel pretty good . when a threat triggers our fight or flight response , our bodies prepare for danger by releasing chemicals that change how our brains and bodies function . this automatic response jumpstarts systems that can aid in survival . they do this by making sure we have enough energy and are protected from feeling pain , while shutting down nonessential systems , like critical thought . feeling pain-free and energized , while not getting caught up in worrisome thoughts that normally occupy our brains , that all sounds great , and it can be because this response is similar , though not exactly the same to what we experience in positive , high-arousal states , like excitement , happiness , and even during sex . the difference lays in the context . if we 're in real danger , we 're focused on survival , not fun . but when we trigger this high arousal response in a safe place , we can switch over to enjoying the natural high of being scared . it 's why people on roller coasters can go from screaming to laughing within moments . your body is already in a euphoric state . you 're just relabeling the experience . and though the threat response is universal , research shows differences between individuals in how the chemicals associated with the threat response work . this explains why some are more prone to thrill-seeking than others . other normal physical differences explain why some may love the dizziness associated with a loop-de-loop , while loathing the stomach-drop sensation of a steep roller coaster , or why some squeal with delight inside a haunted house , but retreat in terror if taken to an actual cemetery . fear brings more than just a fun , natural high . doing things that we 're afraid of can give us a nice boost of self-esteem . like any personal challenge , whether it 's running a race or finishing a long book , when we make it through to the end , we feel a sense of accomplishment . this is true even if we know we 're not really in any danger . our thinking brains may know the zombies are n't real , but our bodies tell us otherwise . the fear feels real , so when we make it through alive , the satisfaction and sense of accomplishment also feel real . this is a great evolutionary adaptation . those who had the right balance of bravery and wit to know when to push through the fear and when to retreat were rewarded with survival , new food , and new lands . finally , fear can bring people together . emotions can be contagious , and when you see your friend scream and laugh , you feel compelled to do the same . this is because we make sense of what our friends are experiencing by recreating the experience ourselves . in fact , the parts of the brain that are active when our friend screams are active in us when we watch them . this not only intensifies our own emotional experience , but makes us feel closer to those we 're with . the feeling of closeness during times of fear is aided by the hormone oxytocin released during fight or flight . fear is a powerful emotional experience , and anything that triggers a strong reaction is going to be stored in our memory really well . you do n't want to forget what can hurt you . so if your memory of watching a horror film with your friends is positive and left you with a sense of satisfaction , then you 'll want to do it over and over again .
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finally , fear can bring people together . emotions can be contagious , and when you see your friend scream and laugh , you feel compelled to do the same . this is because we make sense of what our friends are experiencing by recreating the experience ourselves .
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what does it mean to say that emotions can be contagious ? what are the mechanisms by which emotions are contagious ( e.g. , why are they contagious ? ) ?
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prolonged space travel takes a severe toll on the human body . microgravity impairs muscle and bone growth , and high doses of radiation cause irreversible mutations . as we seriously consider the human species becoming space-faring , a big question stands . even if we break free from earth 's orbit and embark on long-duration journeys among the stars , can we adapt to the extreme environments of space ? this wo n't be the first time that humans have adapted to harsh environments and evolved superhuman capabilities . not fantastical powers like laser vision or invisibility , but physiological adaptations for survival in tough conditions . for example , on the himalayan mountains where the highest elevation is nine kilometers above sea level , an unacclimated lowland human will experience symptoms of hypoxia , commonly known as mountain sickness . at these altitudes , the body usually produces extra red blood cells , thickening the blood and impeding its flow . but himalayans who have lived on these mountains for thousands of years permanently evolved mechanisms to circumvent this process and maintain normal blood flow . cases like that prove that humans can develop permanent lifesaving traits . but natural adaptation for entire human populations could take tens of thousands of years . recent scientific advances may help us accelerate human adaptation to single generations . to thrive as a species during space travel , we could potentially develop methods to quickly program protective abilities into ourselves . a beta version of these methods is gene therapy , which we can currently use to correct genetic diseases . gene editing technology , which is improving rapidly , allows scientists to directly change the human genome to stop undesirable processes or make helpful substances . an example of an unwanted process is what happens when our bodies are exposed to ionizing radiation . without an atmospheric barrier and a magnetic field like earth 's , most planets and moons are bombarded with these dangerous subatomic particles . they can pass through nearly anything and would cause potentially cancerous dna damage to space explorers . but what if we could turn the tables on radiation ? human skin produces a pigment called melanin that protects us from the filtered radiation on earth . melanin exists in many forms across species , and some melanin-expressing fungi use the pigment to convert radiation into chemical energy . instead of trying to shield the human body , or rapidly repair damage , we could potentially engineer humans to adopt and express these fungal , melanin-based energy-harvesting systems . they 'd then convert radiation into useful energy while protecting our dna . this sounds pretty sci-fi , but may actually be achievable with current technology . but technology is n't the only obstacle . there are ongoing debates on the consequences and ethics of such radical alterations to our genetic fabric . besides radiation , variation in gravitational strength is another challenge for space travelers . until we develop artificial gravity in a space ship or on another planet , we should assume that astronauts will spend time living in microgravity . on earth , human bone and muscle custodial cells respond to the stress of gravity 's incessant tugging by renewing old cells in processes known as remodeling and regeneration . but in a microgravity environment like mars , human bone and muscle cells wo n't get these cues , resulting in osteoporosis and muscle atrophy . so , how could we provide an artificial signal for cells to counteract bone and muscle loss ? again , this is speculative , but biochemically engineered microbes inside our bodies could churn out bone and muscle remodeling signaling factors . or humans could be genetically engineered to produce more of these signals in the absence of gravity . radiation exposure and microgravity are only two of the many challenges we will encounter in the hostile conditions of space . but if we 're ethically prepared to use them , gene editing and microbial engineering are two flexible tools that could be adapted to many scenarios . in the near future , we may decide to further develop and tune these genetic tools for the harsh realities of space living .
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but what if we could turn the tables on radiation ? human skin produces a pigment called melanin that protects us from the filtered radiation on earth . melanin exists in many forms across species , and some melanin-expressing fungi use the pigment to convert radiation into chemical energy .
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humans produce a skin pigment know as :
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i must look rather strange to you , all covered in spines , without even a face . but i 've taken many forms during my life . i started out just like you : a tiny egg in a watery world . my parents never knew each other . one moonlit night before a storm , thousands of urchins , clams and corals released trillions of sperm and eggs into the open sea . my father 's sperm somehow met my mother 's egg , and they fused . fertilization . instantly , i became an embryo the size of a speck of dust . after a few hours of drifting , i cleaved in two , then four , then eight cells . then so many , i lost count . in less than a day , i developed a gut and a skeleton . i became a rocket ship , a pluteus larva . i floated through the world of plankton , searching for tiny algae to eat . for weeks , i was surrounded by all kinds of organisms , larvae of all sorts . most are so different from their adult form that biologists have a tough time figuring out who they are . try matching these youngsters to their parents . this veliger larvae will turn into a snail ; this zoea , into a crab ; and this planula , into a clytia jelly . some of my young companions are easier to picture as grown-ups . these baby jellies , known as ephyrae , already resemble their beautiful but deadly parents . here in the plankton , there 's more than one way to get your genes into the next generation . most medusa jellies make special structures called polyps , that simply bud off babies with no need for sex . salps are similar . when food is abundant , they just clone themselves into long chains . the plankton is full of surprises when it comes to sex . meet the hermaphrodites . these comb jellies and arrow worms produce , store and release both sperm and eggs . they can fertilize themselves , or another . when you 're floating in a vast sea , with little control over who you may meet , it can pay to play both sides of the field . the majority of species here , however , never mate , nor form any sort of lasting bonds . that was my parents ' strategy . there were so many of us pluteus larvae , i just hid in the crowd , while most of my kin were devoured . not all parents leave the survival of their offspring to chance . some have far fewer young and take much better care of them , brooding their precious cargo for days , even months . this speedy copepod totes her beautifully packaged eggs for days . this phronima crustacean carries her babies on her chest , then carefully places them in a gelatinous barrel . but the black-eyed squid takes the prize . she cradles her eggs in long arms for nine months , the same time it takes to gestate a human infant . eventually , all youngsters have to make it on their own in this drifting world . some will spend their whole lives in the plankton , but others , like me , move on . a few weeks after i was conceived , i decided to settle down , and metamorphosed into a recognizable urchin . so now you know a bit of my story . i may just be a slow-moving ball of spines , but do n't let my calm adult exterior fool you . i was a rocket ship . i was a wild child .
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for weeks , i was surrounded by all kinds of organisms , larvae of all sorts . most are so different from their adult form that biologists have a tough time figuring out who they are . try matching these youngsters to their parents .
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how would you describe the different phases of a sea urchin ’ s development ?
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this episode is supported by edx . termites , prairie dogs , and people are all great builders , each in their own way . and we all share one crucial problem . put a bunch of us in a closed space , breathing oxygen in and co2 out… and it doesn ’ t end well . our tallest skyscrapers and deepest mines are almost completely cut off from outside air . to keep those inside from suffocating , human engineers use giant machines to bring in fresh air and pump stale air out . termite mounds have the same problem . the largest are more than 10 meters high . on a human scale , that ’ s like a skyscraper three and a half kilometers tall ! only instead of condos and offices , it holds one big farm . the termites collect wood , which grows fungus , that the termites eat . all that fungus and the millions of termites that tend to it create a ton of co2 , which would suffocate the colony *and* their crops if it builds up . to keep the air fresh , the whole mound acts like a big lung . during the day , the sun heats the outer chambers more rapidly than the core , moving air up the outside and down the middle . during the night , this current reverses as the outer chambers lose heat to the cool night air . the whole time , co2 and oxygen are exchanged through tiny holes in the outer walls . what ’ s amazing is this is all constructed without a boss . no central architect designing the structure . just instinct and cooperation lets termites build huge ventilation engines powered by nothing but daily temperature cycles . leafcutter ants farm fungus on massive scales too . one colony in south america covered nearly 50 square meters and was home to over 8 million ants ! but unlike those towering termites , the ant labyrinth reached 8 meters underground . so how do they ventilate their agricultural city ? before we answer that , i want you to try something . take a piece of paper , hold it under your lips , and let the other end curl down . if you blow only across the top of the paper , what do you think will happen ? the force of the air hitting the paper should push it down , right ? well watch this . here ’ s what ’ s happening : air is a fluid . when i force air across the top of the paper , that stream pulls other air along , due to viscosity , which is like the friction of fluids . this leaves an area of low pressure behind , and the paper is pulled up to fill it . this is called the coandă effect . what does that have to do with ants ? check this out . when a breeze flows over a hill , the air is deflected over the top . this pulls air along too , just like when i blew over the paper , drawing air out of the ant hill along the way . the ants build lower entrances nearby , where air is drawn in to replace it , ventilating the whole colony with a little breeze . prairie dogs get the same effect from their mounds . breezes over taller hills draw air through the connected tunnel system , keeping the whole town breathing fresh . there ’ s even a tiny shrimp that uses this same system to keep fresh water flowing through its burrows . persian and egyptian architects have used similar structures to cool buildings for centuries , but tiny animals beat us to that technology by millions of years nature is full of species that build their environment to suit them , countless expert animal architects . sometimes , all you need to solve the most complex engineering problems is the awesome power of evolution , …and that ’ s a breath of fresh air . stay curious . thanks to edx , our non-profit partner for sponsoring this episode . edx.org is where you can learn for free from harvard , mit and other universities around the globe . if you liked this video , you should go check out harvard ’ s architectural imagination course . led by professor michael hays , this online course shows you how to look at architecture as an expression of culture as well as technical achievement . it brings you closer to the work of actual architects and historians through hands-on exercises and historic examples . edx.org offers university level courses in everything from artificial intelligence to leadership , data science to robots and cybersecurity . there are even courses from my alma mater , the university of texas ! edx.org puts a universe of free online learning at your fingertips . visit edx.org today and discover the courses that will keep you learning !
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when a breeze flows over a hill , the air is deflected over the top . this pulls air along too , just like when i blew over the paper , drawing air out of the ant hill along the way . the ants build lower entrances nearby , where air is drawn in to replace it , ventilating the whole colony with a little breeze .
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in order to condition its air , what organ does the anthill act like ?
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some of the issues that are important if you want to have people in space for long periods of time . one is that people will tend to lose bone and muscle mass . we know this . if you have to put a cast on your leg , and you take the cast off after a few weeks , you 'll see that your muscles have shrunk in size . and if you measured the bone strength , you 'd also see that might have gone down a little bit , too . and so , it 's very interesting that our body has that ability to adapt to the loads that are put on it , so that bones and muscles are n't static , they 're always changing . while we think of bone as being a solid thing that does n't change very much , it changes too . and it turns out that in weightlessness , you lose bone . and then you also cause the muscles that work against gravity , what are called the postural muscles , they 'll start to shrink and lose strength . there are other things in the cardiovascular system , the heart and blood vessels . and if you think about it , standing up in gravity means you have to work against gravity in order to keep blood pumping to your head . so , if you could n't keep blood pumping in the head , you 'd pass out every time you stood up because when you 're lying down , you do n't have to push against gravity . but when you stand up , you got to work against gravity to keep blood flowing to your head . and your heart and blood vessels have a really nicely worked-out system to make that happen every time . but that system can also change in weightlessness . and then the other area that changes is the system that has to do with balance . again , maintaining your balance is something that you 're doing against gravity , right ? if you did n't have gravity present , you would n't have to worry about falling . but you obviously do have to worry about falling , and we have a very highly developed sense of balance to keep us upright and to prevent us from falling . and when you see what skaters do , you realize just how exquisite a system it is . but when you go into weightlessness , your balance system changes . you do n't really notice it while you are in weightlessness , but when you come back , you do notice it , that your balance has changed and you have a little bit of trouble maintaining your balance . and what it shows is that while you 're in space , your brain is trying to allow you to function in weightlessness . and so , it re-adapts you to be weightless , which you do n't notice until you come back and find out that you 're now back on earth with a balance system that 's been adapted to space . you know , all life developed here on earth with gravity being present , so life evolved under the influence of gravity , and then we grow up with gravity being present , so we learn how to walk and catch a ball and ice skate or whatever , all with gravity being present . and what if you were to grow up without gravity ? what about the systems that depend on gravity , like your muscles or your balance system or the heart and blood vessels ? would they develop normally , or would they be different in some way ? one reason why you might think that it would go down a different pathway is from an experiment that was done some time ago by two neuroscientists called hubel and wiesel . and what they did is they had a kitten , and they put a patch over the eye of the kitten . and then the kitten grew up to be a cat , and they removed the patch . and so , the question is , can the cat see out of that eye ? now , there 's nothing wrong with the eye , right ? but it just has n't seen anything , there has n't been any light coming in . and the answer is that the cat ca n't see out of that eye because what happens is that the brain goes down a different pathway when it develops and the connections that would ordinarily develop to that eye do n't develop . and that ca n't be undone , that 's a permanent change . so , the brain of that cat is fundamentally different from the brain of a cat that grew up seeing out of that eye . that cat grew up with a different brain , in essence . so , then you wonder , well , what about gravity ? what if you do n't have the forces that gravity produces ? is your balance organ going to develop in the same way , or will it be different ? if somebody grew up in space , could they come back to earth and function , or would they really be a different person ?
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what about the systems that depend on gravity , like your muscles or your balance system or the heart and blood vessels ? would they develop normally , or would they be different in some way ? one reason why you might think that it would go down a different pathway is from an experiment that was done some time ago by two neuroscientists called hubel and wiesel .
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what would be different if you grew up in a system without gravity ?
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translator : tom carter reviewer : bedirhan cinar ( circus music ) [ ted n ' ed 's carnival ] [ john lloyd 's inventory of the invisible ] [ adapted from a tedtalk given by john lloyd in 2009 ] june cohen : our next speaker has spent his whole career eliciting that sense of wonder . please welcome john lloyd . ( applause ) [ hall of mirrors ] the question is , `` what is invisible ? '' there 's more of it than you think , actually . everything , i would say -- everything that matters -- except every thing , and except matter . we can see matter but we ca n't see what 's the matter . we can see the stars and the planets but we ca n't see what holds them apart , or what draws them together . with matter as with people , we see only the skin of things , we ca n't see into the engine room , we ca n't see what makes people tick , at least not without difficulty , and the closer we look at anything , the more it disappears . in fact , if you look really closely at stuff , if you look at the basic substructure of matter , there is n't anything there . electrons disappear in a kind of fuzz , and there is only energy . one of the interesting things about invisibility is , the things that we can 's see , we also ca n't understand . gravity is one thing that we ca n't see , and which we do n't understand . it 's the least understood of all the four fundamental forces , and the weakest , and nobody really knows what it is or why it 's there . for what it 's worth , sir isaac newton , the greatest scientist who ever lived , he thought jesus came to earth specifically to operate the levers of gravity . that 's what he thought he was there for . so , bright guy , could be wrong on that one , i do n't know . ( laughter ) consciousness . i see all your faces ; i 've no idea what any of you are thinking . is n't that amazing ? is n't it incredible that we ca n't read each other 's minds , when we can touch each other , taste each other , perhaps , if we get close enough , but we ca n't read each other 's minds . i find that quite astonishing . in the sufi faith , this great middle eastern religion which some claim is the root of all religions , sufi masters are all telepaths , so they say , but their main exercise of telepathy is to send out powerful signals to the rest of us that it does n't exist . so that 's why we do n't think it exists ; the sufi masters working on us . in the question of consciousness and artificial intelligence , artificial intelligence has really , like the study of consciousness , gotten nowhere , we have no idea how consciousness works . not only have they not created artificial intelligence , they have n't yet created artificial stupidity . ( laughter ) the laws of physics : invisible , eternal , omnipresent , all powerful . remind you of anyone ? interesting . i 'm , as you can guess , not a materialist , i 'm an immaterialist . and i 've found a very useful new word -- ignostic . okay ? i 'm an ignostic . [ god ? ] i refuse to be drawn on the question on whether god exists until somebody properly defines the terms . another thing we ca n't see is the human genome . and this is increasingly peculiar , because about 20 years ago when they started delving into the genome , they thought it would probably contain around 100 thousand genes . every year since , it 's been revised downwards . we now think there are likely to be just over 20 thousand genes in the human genome . this is extraordinary , because rice -- get this -- rice is known to have 38 thousand genes . potatoes have 48 chromosomes , two more than people , and the same as a gorilla . ( laughter ) you ca n't see these things , but they are very strange . the stars by day , i always think that 's fascinating . the universe disappears . the more light there is , the less you can see . time . nobody can see time . i do n't know if you know this . there 's a big movement in modern physics to decide that time does n't really exist , because it 's too inconvenient for the figures . it 's much easier if it 's not really there . you ca n't see the future , obviously , and you ca n't see the past , except in your memory . one of the interesting things about the past is you particularly ca n't see -- my son asked me this the other day , `` dad , can you remember what i was like when i was two ? and i said , `` yes . '' he said , `` why ca n't i ? '' is n't that extraordinary ? you can not remember what happened to you earlier than the age of two or three . which is great news for psychoanalysts , because otherwise they 'd be out of a job . because that 's where all the stuff happens ( laughter ) that makes you who you are . another thing you ca n't see is the grid on which we hang . this is fascinating . you probably know , some of you , that cells are continually renewed . skin flakes off , hairs grow , nails , that kind of stuff -- but every cell in your body is replaced at some point . taste buds , every ten days or so . livers and internal organs take a bit longer . spine takes several years . but at the end of seven years , not one cell in your body remains from what was there seven years ago . the question is : who then are we ? what are we ? what is this thing that we hang on ? that is actually us ? atoms , ca n't see them . nobody ever will . they 're smaller than the wavelength of light . gas , ca n't see that . interesting , somebody mentioned 1600 recently . gas was invented in 1600 by a dutch chemist called van helmont . it 's said to be the most successful ever invention of a word by a known individual . quite good . he also invented a word called `` blas , '' meaning astral radiation . did n't catch on , unfortunately . ( laughter ) but well done , him . light -- you ca n't see light . when it 's dark , in a vacuum , if a person shines a beam of light straight across your eyes , you wo n't see it . slightly technical , some physicists will disagree with this . but it 's odd that you ca n't see the beam of light , you can only see what it hits . electricity , ca n't see that . do n't let anyone tell you they understand electricity , they do n't . nobody knows what it is . ( laughter ) you probably think the electrons in an electric wire move instantaneously down a wire , do n't you , at the speed of light , when you turn the light on , they do n't . electrons bumble down the wire , about the speed of spreading honey , they say . galaxies -- hundred billion of them , estimated in the universe . hundred billion . how many can we see ? five . five , out of a hundred billion galaxies , with the naked eye . and one of them is quite difficult to see , unless you 've got very good eyesight . radio waves . there 's another thing . heinrich hertz , when he discovered radio waves , in 1887 , he called them radio waves because they radiated . somebody said to him , `` what 's the point of these , heinrich ? what 's the point of these radio waves that you 've found ? '' and he said , `` well , i 've no idea , but i guess somebody will find a use for them someday . the biggest thing that 's invisible to us is what we do n't know . it is incredible how little we know . thomas edison once said , `` we do n't know one percent of one millionth about anything . '' and i 've come to the conclusion -- because you ask this other question : `` what 's another thing we ca n't see ? '' the point , most of us . what 's the point ? the point -- what i 've got it down to is there are only two questions really worth asking . `` why are we here ? `` , and `` what should we do about it while we are ? '' to help you , i 've got two things to leave you with , from two great philosophers , perhaps two of the greatest philosopher thinkers of the 20th century . one a mathematician and engineer , and the other a poet . the first is ludwig wittgenstein , who said , `` i do n't know why we are here , but i am pretty sure it 's not in order to enjoy ourselves . '' ( laughter ) he was a cheerful bastard , was n't he ? ( laughter ) and secondly , and lastly , w.h . auden , one of my favorite poets , who said , `` we are here on earth to help others . what the others are here for , i 've no idea . '' ( laughter ) ( applause ) ( circus music ) [ get your souvenir photo here ! ] [ continue your journey into the unknown ! ] ( circus music )
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we can see the stars and the planets but we ca n't see what holds them apart , or what draws them together . with matter as with people , we see only the skin of things , we ca n't see into the engine room , we ca n't see what makes people tick , at least not without difficulty , and the closer we look at anything , the more it disappears . in fact , if you look really closely at stuff , if you look at the basic substructure of matter , there is n't anything there .
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lloyd says that we can only see the skin of things . we ca n't see into the engine room . he suggests that the closer we look at anything , the more :
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when we watch a film or a play , we know that the actors probably learned their lines from a script , which essentially tells them what to say and when to say it . a piece of written music operates on exactly the same principle . in a very basic sense , it tells a performer what to play and when to play it . aesthetically speaking , there 's a world of difference between , say , beethoven and justin bieber , but both artists have used the same building blocks to create their music : notes . and although the end result can sound quite complicated , the logic behind musical notes is actually pretty straightforward . let 's take a look at the foundational elements to music notation and how they interact to create a work of art . music is written on five parallel lines that go across the page . these five lines are called a staff , and a staff operates on two axes : up and down and left to right . the up-and-down axis tells the performer the pitch of the note or what note to play , and the left-to-right axis tells the performer the rhythm of the note or when to play it . let 's start with pitch . to help us out , we 're going to use a piano , but this system works for pretty much any instrument you can think of . in the western music tradition , pitches are named after the first seven letters of the alphabet , a , b , c , d , e , f , and g. after that , the cycle repeats itself : a , b , c , d , e , f , g , a , b , c , d , e , f , g , and so on . but how do these pitches get their names ? well , for example , if you played an f and then played another f higher or lower on the piano , you 'd notice that they sound pretty similar compared to , say , a b . going back to the staff , every line and every space between two lines represents a separate pitch . if we put a note on one of these lines or one of these spaces , we 're telling a performer to play that pitch . the higher up on the staff a note is placed , the higher the pitch . but there are obviously many , many more pitches than the nine that these lines and spaces gives us . a grand piano , for example , can play 88 separate notes . so how do we condense 88 notes onto a single staff ? we use something called a clef , a weird-looking figure placed at the beginning of the staff , which acts like a reference point , telling you that a particular line or space corresponds to a specific note on your instrument . if we want to play notes that are n't on the staff , we kind of cheat and draw extra little lines called ledger lines and place the notes on them . if we have to draw so many ledger lines that it gets confusing , then we need to change to a different clef . as for telling a performer when to play the notes , two main elements control this : the beat and the rhythm . the beat of a piece of music is , by itself , kind of boring . it sounds like this . ( ticking ) notice that it does n't change , it just plugs along quite happily . it can go slow or fast or whatever you like , really . the point is that just like the second hand on a clock divides one minute into sixty seconds , with each second just as long as every other second , the beat divides a piece of music into little fragments of time that are all the same length : beats . with a steady beat as a foundation , we can add rhythm to our pitches , and that 's when music really starts to happen . this is a quarter note . it 's the most basic unit of rhythm , and it 's worth one beat . this is a half note , and it 's worth two beats . this whole note here is worth four beats , and these little guys are eighth notes , worth half a beat each . `` great , '' you say , `` what does that mean ? '' you might have noticed that across the length of a staff , there are little lines dividing it into small sections . these are bar lines and we refer to each section as a bar . at the beginning of a piece of music , just after the clef , is something called the time signature , which tells a performer how many beats are in each bar . this says there are two beats in each bar , this says there are three , this one four , and so on . the bottom number tells us what kind of note is to be used as the basic unit for the beat . one corresponds to a whole note , two to a half note , four to a quarter note , and eight to an eighth note , and so on . so this time signature here tells us that there are four quarter notes in each bar , one , two , three , four ; one , two , three , four , and so on . but like i said before , if we just stick to the beat , it gets kind of boring , so we 'll replace some quarter notes with different rhythms . notice that even though the number of notes in each bar has changed , the total number of beats in each bar has n't . so , what does our musical creation sound like ? ( music ) eh , sounds okay , but maybe a bit thin , right ? let 's add another instrument with its own pitch and rhythm . now it 's sounding like music . sure , it takes some practice to get used to reading it quickly and playing what we see on our instrument , but , with a bit of time and patience , you could be the next beethoven or justin bieber .
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as for telling a performer when to play the notes , two main elements control this : the beat and the rhythm . the beat of a piece of music is , by itself , kind of boring . it sounds like this .
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what kind of music inspires you ? why ?
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germanium is the first element in the periodic table , beginning at hydrogen , that ’ s named after a country : it is named after germany . there are other elements named after france and poland and america but we will come to those later . one of the things about germanium and what really makes it important in the periodic table is that this is one of the elements which was unknown when mendeleev constructed the periodic table and he predicted its existence and when it was found it had many of the properties that he had predicted based on the change in properties as you go down and across the periodic table . so this is a small sample of germanium , named after germany , so you can see the wonderful shiny surfaces . germanium is used quite widely as a so-called semi- conducting material . if you look at it in visible light it looks like a metal . germanium na , na , n-na na . i have used germanium mirrors in some of my experiments . the lasers that i used when i was younger had a germanium mirror that let the light out at the front of it and germanium is used quite widely in electronics . this is quite a nice piece of germanium . unfortunately i broke it somewhat earlier in my career , but you can see very nicely how this material looks like a piece of metal but on the other hand if you shine infrared light through it , it ’ s transparent so the infrared light will through but visible light doesn ’ t .
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germanium is the first element in the periodic table , beginning at hydrogen , that ’ s named after a country : it is named after germany . there are other elements named after france and poland and america but we will come to those later .
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germanium was the first element in the periodic table named after a country , specifically the country of its discoverer . who discovered germanium ?
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you 're swimming in the ocean when something brushes your leg . when the tingling sets in , you realize you 've been stung by a jellyfish . how do these beautiful , gelatinous creatures pack such a painful punch ? jellyfish are soft because they are 95 % water and are mostly made of a translucent gel-like substance called mesoglea . with such delicate bodies , they rely on thousands of venom-containing stinging cells called cnidocytes for protection and prey capture . even baby jellyfish , the size of a pencil eraser , have the ability to sting . larval jellyfish , ephyrae , look like tiny flowers pulsating in the sea . as they grow , they become umbrella-shaped with a bell at the top and descending tentacles around the margin . the largest species of jellyfish , the lion 's mane , has tentacles that can extend more than 100 feet , longer than a blue whale . these tentacles contain most of the stinging cells , although some species have them on their bells , too . venom is ejected via a nematocyst , a whip-like hollow tubule , which lies coiled under high osmotic pressure . when mechanical or chemical stimuli activate an external trigger , the lid of the cell pops open and sea water rushes in . this forces a microscopic barbed harpoon to shoot out , penetrate and inject venom into its victim . nematocyst discharge can occur in less than a millionth of a second , making it one of nature 's fastest biomechanical processes . nematocysts can continue to fire even after a jellyfish has died , so it 's important to remove lingering tentacles stuck to the skin . rinsing with vinegar will usually render undischarged nematocysts inactive . seawater can also help remove residual nematocysts . but do n't use fresh water because any change in salt balance alters the osmotic pressure outside of the cnidocyte and will trigger the nematocyst to fire . that 's why urinating on the affected area , a common folk remedy , may do more harm that good , depending on the composition of the urine . most jellyfish stings are a painful nuisance , but some can be deadly . an indo-pacific box jelly , also called a sea wasp , releases venom which can cause contraction of the heart muscles and rapid death in large doses . there 's an anti-venom , but the venom is fast-acting , so you 'd need immediate medical intervention . despite the impressive power in their tentacles , jellies are n't invincible . their stinging cells are no match for the armor of thick-skin predators , like the leatherback turtle and ocean sunfish . these predators both have adaptations that prevents slippery jellyfish from escaping after they are engulfed : backwards pointing spines in the turtle 's mouth and esophagus and recurved teeth behind the sunfish 's cheeks . even tiny lobster slipper larvae can cling to the bell of a jellyfish and hitch a ride , snacking on the jelly while they preserve their own energy for growth . small agile fish use the jellies as moving reefs for protection , darting between tentacles without ever touching them . nudibranchs , which are sea slugs covered in protective slime , can actually steal the jelly 's defenses by eating the cnidocytes and transferring them to specialized sacks for later use , as weapons against their own predators . even humans might benefit from the sting of a jellyfish one day . scientists are working on manipulating cnidocytes to deliver medicine , with nematocysts rarely 3 % of the size of a typical syringe needle . so , the next time you 're out in the ocean , be careful . but also , take a second to marvel at its wonders .
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as they grow , they become umbrella-shaped with a bell at the top and descending tentacles around the margin . the largest species of jellyfish , the lion 's mane , has tentacles that can extend more than 100 feet , longer than a blue whale . these tentacles contain most of the stinging cells , although some species have them on their bells , too .
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the maximum length of a lion 's mane jellyfish 's tentacles is as long as a :
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[ music ] for thousands of years , humans , and plants and animals long before that , have been using frozen “ sky water ” to keep warm . which sort of doesn ’ t make sense . because snow is cool . you might even say it ’ s… ice cold . yeeaahhhhh ! no one knows for sure who built the first igloo , but with the right fit and the right physics , snow can actually warm you better than the inside of a tauntaun . `` you 'll be ok , luke ! '' so , how can something cold keep you cozy ? [ music ] the vast , frozen arctic is one of the most forbidding environments on our planet , yet , the inuit have managed to live there for about 5,000 years . out on the pack ice , winter temperatures reach 50 degrees below zero , and when it ’ s that cold , surviving means finding shelter . it ’ s not an area known for its forests , so nomadic hunters learned to build with the only thing available : snow . eskimo languages really do have dozens and dozens of different words for snow , because there are a lot of different types , and the type of snow you choose can dictate whether your igloo keeps you warm , or turns you into a homo sapiensicle . to understand this , we need to know a little something about being cold . when your body temperature starts to plummet – you ’ re feeling heat leave you . cold can ’ t move into your body – in fact , there is no such thing as cold . where have i heard that before ? oh , right ! think of heat as an actual quantity of stuff : . the more you give away , the colder you feel . this trading of heat can happen three different ways : by convection , conduction , and radiation . all three are at play in an igloo . a person inside will radiate body heat , which moves around the igloo by convection , and is lost through the walls by conduction . this is exactly what happens in your house . living insulation does the same thing . fatty tissues like blubber help stop heat transfer in whales and seals , but for animals who don ’ t have as much junk in the trunk , they cover themselves in air . sea otter fur , for example , is about a thousand times denser than human hair . it ’ s snuggly stuff `` this is the softest thing i 've ever felt in my life . you are adorable ! '' …but the secret to its insulation power is in its texture . otter fur is spiky , so it traps insulating air molecules . and that is exactly what snowflakes do . powdery , fresh snow can be up to 95 % trapped air . this makes it an excellent insulator , but the same way you have to pack it in your hands to make a snowball , it isn ’ t dense enough to build with . solid ice , on the other hand , makes a good windbreaker , but it ’ s too heavy to lift . inuit hunters took the goldilocks approach : the secret to good igloo snow is somewhere in the middle . traditional igloo blocks aren ’ t molded , they ’ re cut out of the ground . that tightly-packed ground snow is dense enough to hold up , but because it still has far more air pockets than a block of ice , it ’ s light , and still a pretty good insulator . as usual , animals figured this one out long before humans . polar bears , groundhogs , even birds like grouse all make snow burrows to stay warm . and even before that , plants were tucking into snow to avoid death by freezing . during the warm months , heat energy from the sun builds up in soil , and just like the the roof above your head , a deep covering of snow prevents that heat from escaping onward and upward . this snowy blanket above stops ice crystals from forming inside plant roots , and shoots , and seeds . not freezing to death is a pretty good motivator for any animal to get crafty , but our big primate brains took it one step further with igloos . their engineering maximizes warmth and stability . cartoon igloos look like flat-bottomed half-spheres , but in reality , they ’ re neither of those things ! if you were to slice a real igloo in half , you ’ d see a shape called a catenary . this gradually sloping shape is the same one that would form if you held a chain from both ends and let it droop . a catenary arch distributes weight more evenly than a half circle , without bulging or buckling . in fact it ’ s one of the most stable arches in nature , so sound that we still use it today . inside , snow houses are carved in different levels . the hot air rises , and the cold air sinks down into the lower part , and away from where you would eat , sleep , and chill . to boot , body heat melts the innermost layer of the walls , strengthening the barrier between you , your airy snow-block insulation , and the frigid great beyond . when you live in an igloo , you act as a living furnace . over time , the temperature in your icy abode can hover some 40-60 degrees above the surrounding air , but bring a friend to your igloo party , and you ’ ll get warmer , faster . stay cozy , and stay curious ! `` hey , you remember that thing i said about eskimos having all those different words for snow ? well our friends from idea channel made a video about that . here 's an idea , you should go check it out . it 's pretty cool . 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when your body temperature starts to plummet – you ’ re feeling heat leave you . cold can ’ t move into your body – in fact , there is no such thing as cold . where have i heard that before ?
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what is happening to your body when you feel cold ?
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the largest organ in your body is n't your liver or your brain . it 's your skin , with a surface area of about 20 square feet in adults . though different areas of the skin have different characteristics , much of this surface performs similar functions , such as sweating , feeling heat and cold , and growing hair . but after a deep cut or wound , the newly healed skin will look different from the surrounding area , and may not fully regain all its abilities for a while , or at all . to understand why this happens , we need to look at the structure of the human skin . the top layer , called the epidermis , consists mostly of hardened cells , called keratinocytes , and provides protection . since its outer layer is constantly being shed and renewed , it 's pretty easy to repair . but sometimes a wound penetrates into the dermis , which contains blood vessels and the various glands and nerve endings that enable the skin 's many functions . and when that happens , it triggers the four overlapping stages of the regenerative process . the first stage , hemostasis , is the skin 's response to two immediate threats : that you 're now losing blood and that the physical barrier of the epidermis has been compromised . as the blood vessels tighten to minimize the bleeding , in a process known as vasoconstriction , both threats are averted by forming a blood clot . a special protein known as fibrin forms cross-links on the top of the skin , preventing blood from flowing out and bacteria or pathogens from getting in . after about three hours of this , the skin begins to turn red , signaling the next stage , inflammation . with bleeding under control and the barrier secured , the body sends special cells to fight any pathogens that may have gotten through . among the most important of these are white blood cells , known as macrophages , which devour bacteria and damage tissue through a process known as phagocytosis , in addition to producing growth factors to spur healing . and because these tiny soldiers need to travel through the blood to get to the wound site , the previously constricted blood vessels now expand in a process called vasodilation . about two to three days after the wound , the proliferative stage occurs , when fibroblast cells begin to enter the wound . in the process of collagen deposition , they produce a fibrous protein called collagen in the wound site , forming connective skin tissue to replace the fibrin from before . as epidermal cells divide to reform the outer layer of skin , the dermis contracts to close the wound . finally , in the fourth stage of remodeling , the wound matures as the newly deposited collagen is rearranged and converted into specific types . through this process , which can take over a year , the tensile strength of the new skin is improved , and blood vessels and other connections are strengthened . with time , the new tissue can reach from 50-80 % of some of its original healthy function , depending on the severity of the initial wound and on the function itself . but because the skin does not fully recover , scarring continues to be a major clinical issue for doctors around the world . and even though researchers have made significant strides in understanding the healing process , many fundamental mysteries remain unresolved . for instance , do fibroblast cells arrive from the blood vessels or from skin tissue adjacent to the wound ? and why do some other mammals , such as deer , heal their wounds much more efficiently and completely than humans ? by finding the answers to these questions and others , we may one day be able to heal ourselves so well that scars will be just a memory .
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a special protein known as fibrin forms cross-links on the top of the skin , preventing blood from flowing out and bacteria or pathogens from getting in . after about three hours of this , the skin begins to turn red , signaling the next stage , inflammation . with bleeding under control and the barrier secured , the body sends special cells to fight any pathogens that may have gotten through .
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what signals the onset of the inflammation phase ?
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so here you can see we have a very thin foil sample of dysprosium . again it is from the bottom end of the periodic table , very , very reactive . stored very , very carefully as a foil . now if we open , very carefully , we might see if the metal is still there . ok so dysprosium is used in nuclear fuel rods because it is very good at capturing neutrons , which means that you can modulate how hot a nuclear reaction is getting which is why it is used in powerstations to prevent the reactions from running away out of control . so take off all this foil and then we can withdraw the sample . so it is in this really nice paper . so is the sample still there ? oh beautiful , here we see this wonderful sample of dysprosium . if you mix dysprosium with cadmium and sulphur it can be used in devices which produce infrared beams . now chemists use infrared beams quite a lot because when you irradiate a sample , a compound with infrared then certain absorbencies will occur which are specific to stretching or bending modes which the molecule will do . this is a way of , therefore , scanning molecules and getting information about their composition and structure . beautiful foil . do you happen to know anything about this element ? not a thing , that ’ s steve ’ s domain . yeah !
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now if we open , very carefully , we might see if the metal is still there . ok so dysprosium is used in nuclear fuel rods because it is very good at capturing neutrons , which means that you can modulate how hot a nuclear reaction is getting which is why it is used in powerstations to prevent the reactions from running away out of control . so take off all this foil and then we can withdraw the sample .
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why is dysprosium used in fission nuclear plants ?
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most people will take a pill , receive an injection , or otherwise take some kind of medicine during their lives , but most of us do n't know anything about how these substances actually work . how can various compounds impact the way we physically feel , think , and even behave ? for the most part , this depends on how a drug alters the communication between cells in the brain . there are a number of different ways that can happen . but before it gets into the brain , any drug must first reach the bloodstream on a journey that can take anywhere from seconds to hours , depending on factors like how it 's administered . the slowest method is to take a drug orally because it must be absorbed by our digestive system before it takes effect . inhaling a drug gets it into the bloodstream faster . and injecting a drug intravenously works quickly too because it pumps the chemicals directly into the blood . once there , the drug quickly reaches the gates of its destination , the brain . the entrance to this organ is guarded by the blood-brain barrier , which separates blood from the nervous system to keep potentially dangerous substances out . so all drugs must have a specific chemical composition which gives them the key to unlock this barrier and pass through . once inside , drugs start to interfere with the brain 's normal functioning by targeting its web of neurons and synapses . neurons are brain cells that have a nucleus , dendrites , and an axon . synapses are structures placed along the dendrites or the axon which allow the exchange of electrochemical signals between neurons . those signals take the form of chemicals called neurotransmitters . each neurotransmitter plays different roles in regulating our behaviors , emotions , and cognition . but they all work in one of two ways . they can either inhibit the receiving neuron , limiting its activity , or excite it , creating a new electrochemical signal that spreads throughout the network . any leftover neurotransmitter usually gets degraded or reabsorbed into the transmitting neuron . a drug 's effectiveness stems from its ability to manipulate these synaptic transmissions at different phases of the process . that results in an increase or a decrease in the amount of neurotransmitters being spread . for instance , common antidepressants , like ssris , stop the reabsorption of serotonin , a neurotransmitter that modulates our moods . this effectively pushes more of it into the neural network . meanwhile , painkillers , like morphine , raise levels of serotonin and noradrenaline , which regulate energy , arousal , alertness , and pleasure . those same neurotransmitters also affect endorphin receptors , reducing pain perception . and tranquilizers works by increasing the production of gaba to inhibit neural activity putting the person in a relaxed or sedated state . what about illegal or elicit drugs ? these have powerful impacts on the brain that we 're still trying to understand . crystal meth , an amphetamine , induces a long-lasting release of dopamine , a neurotransmitter linked with the perception of reward and pleasure . it also activates noradrenaline receptors , which increases the heart rate , dilates pupils , and triggers the body 's fight or flight response . cocaine blocks the reuptake of dopamine and serotonin , pushing more into the network where they boost energy , create feelings of euphoria , and suppress appetites . and hallucinogenic drugs have some of the most puzzling effects . substances like lsd , mescaline , and dmt all block the release of serotonin , which regulates mood and impulsivity . they also have an impact on the neural circuits involved in perception , learning , and behavioral regulation , which may explain why these drugs have such powerful impacts . even if some of these effects sound exciting , there are reasons why some of these drugs are highly controlled and often illegal . drugs have the power to alter the brain 's chemistry , and repeated use can permanently rewire the neural networks that support our ability to think , make decisions , learn , and remember things . there 's a lot we still do n't know about drugs and their effects , both the good and the bad . but those we do know about are the ones we 've studied closely , and turned into effective medicines . as our knowledge grows about drugs and the brain , the possibilities will also increase for treating the many medical problems that puzzle researchers today .
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any leftover neurotransmitter usually gets degraded or reabsorbed into the transmitting neuron . a drug 's effectiveness stems from its ability to manipulate these synaptic transmissions at different phases of the process . that results in an increase or a decrease in the amount of neurotransmitters being spread .
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given the complex effect that a single drug can have on different neurotransmitters , try to imagine the consequences resulting from the interaction of multiple drugs .
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you 're the realm 's greatest mathematician , but ever since you criticized the emperor 's tax laws , you 've been locked in the dungeon with only a marker to count the days . but one day , you 're suddenly brought before the emperor who looks even angrier than usual . one of his twelve governors has been convicted of paying his taxes with a counterfeit coin which has already made its way into the treasury . as the kingdom 's greatest mathematician , you 've been granted a chance to earn your freedom by identifying the fake . before you are the twelve identical looking coins and a balance scale . you know that the false coin will be very slightly lighter or heavier than the rest . but the emperor 's not a patient man . you may only use the scale three times before you 'll be thrown back into the dungeon . you look around for anything else you can use , but there 's nothing in the room - just the coins , the scale , and your trusty marker . how do you identify the counterfeit ? pause here if you want to figure it out for yourself ! answer in : 3 answer in : 2 answer in : 1 obviously you ca n't weigh each coin against all of the others , so you 'll have to weigh several coins at the same time by splitting the stack into multiple piles then narrowing down where the false coin is . start by dividing the twelve coins into three equal piles of four . placing two of these on the scale gives us two possible outcomes . if the two sides balance , all eight coins on the scale are real , and the fake must be among the remaining four . so how do you keep track of these results ? that 's where the marker comes in . mark the eight authentic coins with a zero . now , take three of them and weigh them against three unmarked coins . if they balance , the remaining unmarked coin must be the fake . if they do n't , draw a plus on the three unmarked coins if they 're heavier or a minus if they 're lighter . now , take two of the newly marked coins and weigh them against each other . if they balance , the third coin is fake . otherwise , look at their marks . if they are plus coins , the heavier one is the imposter . if they are marked with minus , it 's the lighter one . but what if the first two piles you weigh do n't balance ? mark the coins on the heavier side with a plus and those on the lighter side with a minus . you can also mark the remaining four coins with zeros since you know the fake one is already somewhere on the scale . now , you 'll need to think strategically so you can remove all remaining ambiguity in just two more weighings . to do this , you 'll need to reassemble the piles . one method is to replace three of the plus coins with three of the minus coins , and replace those with three of the zero coins . > from here , you have three possibilities . if the previously heavier side of the scale is still heavier , that means either the remaining plus coin on that side is actually the heavier one , or the remaining minus coin on the lighter side is actually the lighter one . choose either one of them , and weigh it against one of the regular coins to see which is true . if the previously heavier side became lighter , that means one of the three minus coins you moved is actually the lighter one . weigh two of them against each other . if they balance , the third is counterfeit . if not , the lighter one is . similarly , if the two sides balanced after your substitution , then one of the three plus coins you removed must be the heavier one . weigh two of them against each other . if they balance , the third one is fake . if not , then it 's the heavier one . the emperor nods approvingly at your finding , and the counterfeiting lord takes your place in the dungeon .
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if the previously heavier side of the scale is still heavier , that means either the remaining plus coin on that side is actually the heavier one , or the remaining minus coin on the lighter side is actually the lighter one . choose either one of them , and weigh it against one of the regular coins to see which is true . if the previously heavier side became lighter , that means one of the three minus coins you moved is actually the lighter one .
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in the first weighing of the problem , could we have split the 12 coins another way ( e.g. , 2 groups of 3 and one group of 6 ) and still completed the problem in 3 weighs ?
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you 're facing a giant bowl of energy packed carbon crunchies . one spoonful . two . three . soon , you 're powered up by the energy surge that comes from your meal . but how did that energy get into your bowl ? energy exists in the form of sugars made by the plant your cereal came from , like wheat or corn . as you can see , carbon is the chemical backbone , and plants get their fix of it in the form of carbon dioxide , co2 , from the air that we all breath . but how does a plant 's energy factory , housed in the stroma of the chloroplast , turn a one carbon gas , like co2 , into a six carbon solid , like glucose ? if you 're thinking photosynthesis , you 're right . but photosynthesis is divided into two steps . the first , which stores energy from the sun in the form of adenosine triphosphate , or atp . and the second , the calvin cycle , that captures carbon and turns it into sugar . this second phase represents one of nature 's most sustainable production lines . and so with that , welcome to world 's most miniscule factory . the starting materials ? a mix of co2 molecules from the air , and preassembled molecules called ribulose biphosphate , or rubp , each containing five carbons . the initiator ? an industrious enzyme named rubisco that welds one carbon atom from a co2 molecule with the rubp chain to build an initial six carbon sequence . that rapidly splits into two shorter chains containing three carbons each and called phosphoglycerates , or pgas , for short . enter atp , and another chemical called nicotinamide adenine dinucleotide phosphate , or just nadph . atp , working like a lubricant , delivers energy , while nadph affixes one hydrogen to each of the pga chains , changing them into molecules called glyceraldehyde 3 phosphates , or g3ps . glucose needs six carbons to form , made from two molecules of g3p , which incidentally have six carbons between them . so , sugar has just been manufactured , right ? not quite . the calvin cycle works like a sustainable production line , meaning that those original rubps that kicked things off at the start , need to be recreated by reusing materials within the cycle now . but each rubp needs five carbons and manufacturing glucose takes a whole six . something does n't add up . the answer lies in one phenomenal fact . while we 've been focusing on this single production line , five others have been happening at the same time . with six conveyor belts moving in unison , there is n't just one carbon that gets soldered to one rubp chain , but six carbons soldered to six rubps . that creates 12 g3p chains instead of just two , meaning that all together , 36 carbons exist : the precise number needed to manufacture sugar , and rebuild those rubps . of the 12 g3ps pooled together , two are siphoned off to form that energy rich six carbon glucose chain . the one fueling you via your breakfast . success ! but back on the manufacturing line , the byproducts of this sugar production are swiftly assembled to recreate those six rubps . that requires 30 carbons , the exact number contained by the remaining 10 g3ps . now a molecular mix and match occurs . two of the g3ps are welded together forming a six carbon sequence . by adding a third g3p , a nine carbon chain is built . the first rubp , made up of five carbons , is cast from this , leaving four carbons behind . but there 's no wastage here . those are soldered to a fourth g3p molecule , making a seven carbon chain . added to a fifth g3p molecule , a ten carbon chain is created , enough now to craft two more rubps . with three full rubps recreated from five of the ten g3ps , simply duplicating this process will renew the six rubp chains needed to restart the cycle again . so the calvin cycle generates the precise number of elements and processes required to keep this biochemical production line turning endlessly . and it 's just one of the 100s of cycles present in nature . why so many ? because if biological production processes were linear , they would n't be nearly as efficient or successful at using energy to manufacture the materials that nature relies upon , like sugar . cycles create vital feedback loops that repeatedly reuse and rebuild ingredients crafting as much as possible out of the planet 's available resources . such as that sugar , built using raw sunlight and carbon converted in plant factories to become the energy that powers you and keeps the cycles revolving in your own life .
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that creates 12 g3p chains instead of just two , meaning that all together , 36 carbons exist : the precise number needed to manufacture sugar , and rebuild those rubps . of the 12 g3ps pooled together , two are siphoned off to form that energy rich six carbon glucose chain . the one fueling you via your breakfast .
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the calvin cycle is the second part of the photosynthesis reaction . photosynthesis stores energy from the sun as well we carbon from the air together in the high-energy molecule , glucose . does the calvin cycle itself have a use or release energy ? with energy that is used , where does it come from ?
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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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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 .
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describe each of the shark tooth types , structures , and functions in a chart .
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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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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 .
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which mineral , discovered in the english midlands of derbyshire , is a special form of calcium fluorite ? this special form of calcium fluorite contains trace amounts of europium , which gives it the property to emit blue light when exposed to uv light .
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i love astronomy . you may have noticed . but there ’ s one really frustrating aspect of it : everything we study is really far away . nearly everything we understand about the universe comes from light emitted or reflected by objects . it ’ d be nice if we could get actual samples from them ; physical specimens we could examine in the lab . welp , sometimes the universe can be accommodating , and allows us to hold it in our hands . cambot , can we get this up on still store ? if you go outside on a clear , dark , moonless night — and you really should — chances are pretty good that within a few minutes you ’ ll see a shooting star . it ’ ll zip across the sky , a fiery dot leaving a long glowing trail behind it . they ’ re one of the most exciting and fun things you ’ ll see when you look up , and they always get a gasp and a squeal of delight from people someone who ’ s stargazing . what you ’ re actually seeing is a tiny bit of interplanetary debris : rock , ice , or metal ramming through the earth ’ s atmosphere , heated to incandescence . most are faint , but some can be astonishingly bright ; i saw one once that left an afterimage on my eye ! obviously , shooting stars aren ’ t really stars . so what do we call them ? sometimes it seems like astronomers use different names for objects to keep things as confusing as possible . but really , we do that to separate out different things . in this case , the actual bit of solid stuff coming from space is called a meteoroid . the phenomenon of the meteoroid getting hot and blazing across the sky is called a meteor . and finally , if it hits the ground , we call it a meteorite . i think the second best way to tick off an astronomer is to mix up meteor and meteorite . sometimes astronomers can be pretty pedantic about such things . oh , the best way to tick off an astronomer ? ask them , “ hey , what ’ s your sign ? ” amazingly , a typical meteor that you ’ ll see is due to a meteoroid that ’ s tiny , probably smaller than a grain of sand ! how can that be ? it ’ s because they ’ re hauling mass . you heard me . the meteoroid is orbiting the sun , probably at speeds of a few dozen kilometers per second . as it approaches the earth , our planet ’ s gravity accelerates it an additional 11 kilometers per second — earth ’ s escape velocity . and when it enters our atmosphere it ’ s moving incredibly fast , up to 70 km/sec or more . the energy of motion is called kinetic energy . if you want to get something moving , you have to give it energy , and if you want it to stop , you have to take that energy away . this kinetic energy depends on the mass of the object and how fast it ’ s moving . in fact , it depends on the square of the velocity ; double its speed and it ’ ll have four times the kinetic energy . meteoroids may usually be small , but they ’ re screaming fast , and have a huge amount of kinetic energy . as they hit our atmosphere they slow from their ridiculous orbital speed to nearly a standstill , and all that energy has to go somewhere . it gets converted into light and heat , and that ’ s what we see as a meteor . a big misconception about meteors is that they get hot due to friction with air . actually , a far bigger contributor to their heat is compression . one of the most basic laws of physics is that when you compress a gas it heats up . and a meteoroid coming in at hypersonic speeds compresses the air in front of it a lot , heating it hugely . the gas can reach temperatures of thousands of degrees celsius for a few seconds . the air radiates away this heat , in turn heating up the meteoroid . the material on the surface vaporizes and blows away—a process called ablation . that ablated material leaves a glowing trail behind the meteor , which we call a train . sometimes it can glow for several minutes , getting twisted up in high altitude winds , leaving behind an eerie , ghost-like persistent train . this all happens high above your head , about 90 – 100 km above the ground . typically , from any one location , you can see a few meteors per hour . it may not seem like much , but when you add them up all over the planet you find the earth is getting pelted to the tune of about 100 tons of material a day . but again , most of these meteoroids are teeny tiny . those random meteors are called sporadic meteors . they tend to be rocky in composition , and generally come from asteroids . if two asteroids smack into each other , the collision can eject little bits of material that then orbit the sun on their own . if their orbit crosses the earth , then you have a potential meteor . it may take a few million years , but at some point the earth and the meteoroid are at the same place at the same time , and boom . but sometimes meteoroids travel in packs . when that happens , we can get meteor showers , many dozens or even hundreds of meteors per hour . with one exception , those don ’ t come from asteroids : they come from comets . when a comet orbits the sun , the ice on it turns to gas , dislodging dust and gravel mixed in . this material leaves the comet and tends to stay more or less in the same orbit as the comet itself . over time , that material gets scattered all along the orbit , creating a puffy ribbon of tiny pieces of space debris around the sun . when the earth plows through that cloud of debris , we get a meteor shower . from our viewpoint on earth we see meteors shooting across the sky , apparently radiating away from a single point . that ’ s a perspective effect ; it ’ s like driving through a tunnel and seeing the tiles on the wall and ceiling flying past you , all apparently coming from a point ahead of you . the point in the sky where the meteors come from is called the radiant , and the shower is named after the constellation the radiant ’ s in . so we have the perseid meteor shower , the leonids , the camelopardalids . or the camelopardalids . and , since the earth hits a specific comet stream around the same time every year , the showers are annual . the perseids are in august , and the leonids in november . watching a meteor shower is easy : just go outside and look up ! generally , they ’ re better after local midnight . the earth plows into the meteoroids , so facing the direction of earth ’ s orbital motion means more meteors , just like you get more raindrops on the front windshield of your car than than on the back when driving through a storm . after local midnight you ’ re on the part of the earth facing into the orbit , so you see more meteors . by the way , if you happen to be on the international space station , you have to look down to see a meteor . in 2011 , astronaut ron garan photographed a perseid burning up below him ! but don ’ t worry : the odds of the space station getting hit are extremely low . space is big . oh , and that one exception i mentioned before ? that ’ s the annual geminids shower , which occurs in december . that comes from the asteroid 3200 phaethon , which is on an orbit that takes it very close to the sun . it ’ s possible it gets so hot that the rock vaporizes , making it act like a comet . the vast majority of meteoroids are small and tend to burn up in our atmosphere . but they can be bigger . a bolide , or fireball , is an extremely bright meteor , and those can be about the size of a grapefruit . those happen pretty often somewhere over the earth . i ’ ve seen a few myself . very rarely , an incoming meteoroid will survive all the way to the ground and become a meteorite . sometimes , the immense pressure of ramming earth ’ s air causes the incoming meteoroid to crumble or even explode , raining down dozens or hundreds of smaller pieces . typically , they slow rapidly after their blaze of glory , and simply fall the rest of the way to the ground . the air up there is cold , and their interiors are cold from being in space so long . so , despite what you might think , meteorites don ’ t cause fires when they hit the ground . in fact , they can be quite chilly ! meteorites are classified into three broad categories : stony , which are mostly rock ; iron , which are mostly metal ; and stony iron , which are a mixture of the two . the majority of meteorites we find are stony . the stony meteorites are subdivided into two kinds : chondrites , and achondrites . chondrites contain chondrules , small grains of minerals . these are very primitive , and are thought to have condensed out of the original disk of material that formed the solar system . their age can be found by looking at ratios of elements in them formed from radioactive decay . the oldest known meteorite formed 4.568 billion years ago : before the earth itself formed ! achondrites don ’ t have chondrules in them . most likely they came from a bigger asteroid , one that was once molten through , mixing the minerals . a big collision disrupted the parent body , creating the achondritic meteoroids . iron meteorites most likely come from the center of a large asteroid , one big enough that metals fell to the center via gravity . again , a big impact blew the asteroid up , scattering its material around the asteroid belt , and with some on orbits that eventually intersected earth . stony irons are the rarest . some have green or orange crystals of a mineral called olivine embedded in a web of metal . called pallasites , they may be the most beautiful of all meteorites . i actually collect meteorites . it ’ s fun but can be a somewhat pricey hobby . if you ’ re interested , make sure you get ‘ em from a licensed dealer . we have links to some in the dooblydoo . of course , on occasion the meteoroid coming in can be a tad bigger . and when that happens , well , all hell can break loose . on february 15 , 2013 , residents of the russian city of chelyabinsk got a rude awakening . at 9:20 a.m. local time , a rock about 19 meters across came in at a low angle . it got nearly as bright as the sun as it slammed into the atmosphere , and the pressure of its passage broke it up into several chunks , which broke up again . in a moment ’ s time , the sudden energy released was equivalent to the detonation of a half million tons of tnt — as much as a small atomic bomb ! while no one was killed , over a thousand people were injured by flying glass , shattered by the explosion . no doubt they were at their windows gawking at the huge vapor trail in the sky when the shock wave hit . there was no warning for this event ; the asteroid was essentially too small to detect while it was out in space . well , for now at least . telescopes are coming online soon that should be able to find smaller asteroids and give us some warning . astronomers are more worried about ones roughly a hundred meters across or bigger ; these can do serious damage on a city-wide scale or larger , but at the moment aren ’ t easy to spot much in advance . and what do we do if we do see one headed our way ? as of right now , there ’ s not much we can do . studies have been done to determine the best course of action ; maybe lobbing a nuke at it , or simply ramming it with a spaceprobe to change the orbit and make sure it misses earth . these ideas look good on paper , but they haven ’ t been tested yet . we ’ re still a few years from that . the good news is that objects that size hitting the earth are rare ; maybe once every century or three . but if we do nothing , it will happen eventually . as science fiction writer larry niven points out , the dinosaurs went extinct because they didn ’ t have a space program . hopefully , we ’ re smarter than they were . today you learned that meteors are small bits of interplanetary debris sloughed off by asteroids and comets . when the earth plows through the stream emitted by a comet we get a meteor shower . meteors burn up about 100 km above the earth , but some survive to hit the ground . most of these meteorites are rocky , some are metallic , and a few are a mix of the two . very big meteorites can be a very big problem , but there are plans in the works to prevent us from going the way of the dinosaurs . crash course astronomy - hey crash course , meteors ! cool ! crash course astronomy is produced in association with pbs digital studios . head over to their channel for even more awesome videos . this episode was written by me , phil plait . the script was edited by blake de pastino , and our consultant is dr. michelle thaller . it was directed by nicholas jenkins , the script supervisor and editor is nicole sweeney , the sound designer was michael aranda , and the graphics team is thought café .
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the perseids are in august , and the leonids in november . watching a meteor shower is easy : just go outside and look up ! generally , they ’ re better after local midnight .
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when is the best time of night to see a meteor shower ?
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so you can see on the front of this instrument is a dome shaped device . that dome is a special vessel which is made so we can control the atmosphere inside and it is fabricated from beryllium metal . this is the beryllium which i don ’ t really want to get out . why not ? well , because it is a toxic chemical , a toxic metal . beryllium is an interesting element because most chemists don ’ t really know about it very much at all . so beryllium is a fantastic metal , it is really , really interesting , it ’ s got really lots of strange metallic properties , but one of the most important to me is that it is transparent to x-rays . so i can shine x-rays straight through the beryllium and the beryllium does not absorb it at all which most other metals especially those with higher molecular weights do . beryllium-laden dust has been shown to cause berylliosis which is actually an industrial lung disease which causes the formation of swollen nodules in the lungs called granulomas which is a bit gross , so i don ’ t really want to open up the jar . it ’ s near the beginning of the periodic table , but we rarely come across it . so at the moment we are at matt ’ s lab and we are doing some x-ray experiments on a really , really quite sensitive compound . so x-rays themselves are absorbed by everything , ok , so when we shoot it through the air it is absorbed by the air , so to measure the x-ray absorption of our compound which is sensitive to the air we need to be able to remove the air and encase it so we use beryllium to make a magic box around our sample , that the x-rays can come into , interact with our sample , and then exit without interacting with the material around them . so you can see on the front of this instrument , there is a dome shaped device , that dome , is a special vessel which is made so that we could control the atmosphere inside and it is fabricated from beryllium metal . i talk about in my lectures , i explain that beryllium chloride the molecule that has three atoms , two chlorine atoms and one beryllium atom , has the three atoms arranged in the row , so it is a straight molecule so called linear molecule . i have never seen beryllium chloride . chemists use it on x-ray defractometers because actually it is so lightweight it is actually got atomic number 4 . the beryllium allows the x-rays to come in and out without interacting at all . it is a fantastic device it is really useful for really sensitive chemistry , it is a really beautiful application . the cost of that beryllium though , that is significant , that small beryllium sample cost 15,000 euros . it only has four protons and a number of neutrons so if x-rays fall on atoms of beryllium they are not scattered very much so it ’ s like the difference between shining light through a glass window and if you made it out of a heavy material it would be like , shining through paper , it would be scattered you wouldn ’ t get a good image . i ’ m hoping to actually do some chemistry with beryllium which is why i ’ ve bought it . it is pretty toxic so we are going to have to be very , very careful . you can ’ t actually breathe in the dust at all , cause even actually one exposure has shown with some people one exposure is enough to cause this sort of sensitive reaction . but beryllium is very poisonous so if you do use these beryllium windows , you have to be careful not to lick your fingers . well good chemists shouldn ’ t lick their fingers anyway .
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but beryllium is very poisonous so if you do use these beryllium windows , you have to be careful not to lick your fingers . well good chemists shouldn ’ t lick their fingers anyway .
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in this video , professor poliakoff reminds us of an important rule in the lab : “ good chemists never…
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translator : andrea mcdonough reviewer : bedirhan cinar it is only in the last 100 or so years that human kind has understood that the nucleus of the chemical elements is not always fixed . it can change spontaneously from one element to another . the name for this process is radioactivity . you probably already know something about the nucleus : it 's much tinier than the atom , it 's made of particles called protons and neutrons , there are electrons orbiting around it . and though the atoms can share or swap electrons when they bond together , the nuclei themselves never change . right ? well , no . certain nuclei are not stable in that way . this means they may change suddenly , spontaneously . the radioactive nucleus flings out a small particle and transforms into another element , just like that . for example , the carbon nucleus can eject a fast-moving electron and turn into a nitrogen nucleus . there are two different particles that can be emitted from radioactive nuclei , but never together . the very fast electron is known as a beta particle . if you know a little bit about electrons , you may be thinking , `` what was the electron doing in the nucleus in the first place ? '' the answer is there is a neutron in nucleus spontaneously changed into a proton , which stayed behind , and the electron flew out as a beta particle . this is not what chemistry has taught us to expect . the nucleus is supposed to be stable . neutrons do n't change into protons . except , sometimes they do ! the other particle it emits spontaneously from an unstable nucleus is alpha . an alpha particle is 8,000 times more massive than beta , and it 's a bit slower . alpha is made from two protons and two neutrons . if we trap all those alpha particles together , we get helium gas . alpha is a helium nucleus . like the beta particle , you would not have expected a heavier nucleus to throw out helium . but again , it happens , and the nucleus becomes a new element . so , is radioactivity useful or just dangerous ? wherever you are sitting , it is quite likely that there is a device nearby which contains a source of alpha particles : a smoke detector . the source is radioactive americium . you are totally safe from these alpha particles , which can not travel more than a few centimeters in air . beta particles penetrate much farther through materials than alpha can . radioactive atoms are used in medicine as traces , to show where chemicals travel in the patient . beta particles are emitted and have enough energy to emerge from the body and be detected . there is a third type of nuclear radiation : gamma , which is not a particle at all . it is an electromagnetic wave , like microwaves , or light , but it is actually 1,000 times more energentic than visible light . gamma rays may pass right through your body . gamma is used to zap the bacteria in fruit to increase its shelf life , or in radiotherapy to kill cancer cells . radioactive substances get hot , and this heat can be used to generate power . this heat has been brought to you since space probes , and , in the past , in pacemakers for hearts . the more abruptly nuclear radiation is slowed down , the more damage it does to the atoms it hits . this is called ionization . alpha causes the most ionization as it crashes into other atoms and gamma the least . in humans , the most serious effect of radiation is the damage that it can cause to our dna . although alpha can not penetrate your skin , if you inhale or injest a radioactive nucleus , the health consequences can be severe . radioactivity is both useful and deadly , but it is all around us as a background to the natural world .
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gamma is used to zap the bacteria in fruit to increase its shelf life , or in radiotherapy to kill cancer cells . radioactive substances get hot , and this heat can be used to generate power . this heat has been brought to you since space probes , and , in the past , in pacemakers for hearts .
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nuclear power stations produce dangerous radioactive waste which must be stored safely for thousands of years . despite this , what arguments are used in favor of developing nuclear power ?
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every spring , hundreds of adventure-seekers dream of climbing qomolangma , also known as mount everest . at base camp , they hunker down for months waiting for the chance to scale the mountain 's lofty , lethal peak . but why do people risk life and limb to climb everest ? is it the challenge ? the view ? the chance to touch the sky ? for many , the draw is everest 's status as the highest mountain on earth . there 's an important distinction to make here . mauna kea is actually the tallest from base to summit , but at 8850 meters above sea level , everest has the highest altitude on the planet . to understand how this towering formation was born , we have to peer deep into our planet 's crust , where continental plates collide . the earth 's surface is like an armadillo 's armor . pieces of crust constantly move over , under , and around each other . for such huge continental plates , the motion is relatively quick . they move two to four centimeters per year , about as fast as fingernails grow . when two plates collide , one pushes into or underneath the other , buckling at the margins , and causing what 's known as uplift to accomodate the extra crust . that 's how everest came about . 50 million years ago , the earth 's indian plate drifted north , bumped into the bigger eurasian plate , and the crust crumpled , creating huge uplift . mountain everest lies at the heart of this action , on the edge of the indian-eurasian collision zone . but mountains are shaped by forces other than uplift . as the land is pushed up , air masses are forced to rise as well . rising air cools , causing any water vapor within it to condense and form rain or snow . as that falls , it wears down the landscape , dissolving rocks or breaking them down in a process known as weathering . water moving downhill carries the weathered material and erodes the landscape , carving out deep valleys and jagged peaks . this balance between uplift and erosion gives a mountain its shape . but compare the celestial peaks of the himalayas to the comforting hills of appalachia . clearly , all mountains are not alike . that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast . the peaks grow tall with steep slopes . over time , however , gravity and water wear them down . eventually , erosion overtakes uplift , wearing down peaks faster than they 're pushed up . a third factor shapes mountains : climate . in subzero temperatures , some snowfall does n't completely melt away , instead slowly compacting until it becomes ice . that forms the snowline , which occurs at different heights around the planet depending on climate . at the freezing poles , the snowline is at sea level . near the equator , you have to climb five kilometers before it gets cold enough for ice to form . gathered ice starts flowing under its own immense weight forming a slow-moving frozen river known as a glacier , which grinds the rocks below . the steeper the mountains , the faster ice flows , and the quicker it carves the underlying rock . glaciers can erode landscapes swifter than rain and rivers . where glaciers cling to mountain peaks , they sand them down so fast , they lop the tops off like giant snowy buzzsaws . so then , how did the icy mount everest come to be so tall ? the cataclysmic continental clash from which it arose made it huge to begin with . secondly , the mountain lies near the tropics , so the snowline is high , and the glaciers relatively small , barely big enough to widdle it down . the mountain exists in a perfect storm of conditions that maintain its impressive stature . but that wo n't always be the case . we live in a changing world where the continental plates , earth 's climate , and the planet 's erosive power might one day conspire to cut mount everest down to size . for now , at least , it remains legendary in the minds of hikers , adventurers , and dreamers alike .
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that 's because time comes into the equation , too . when continental plates first collide , uplift happens fast . the peaks grow tall with steep slopes .
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when two plates collide , such as the indian and eurasian plates , what occurs to accommodate the extra crust ?
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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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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 .
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brenda milner , the phd student sent to study h.m. , helped prove :
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if i were to distill the 20 years of elephant research that i 've done into one sentence , what would it be ? what could i tell you ? i would say that elephants are just like us ! and what do i mean by that ? it takes a lot of patience to be out there in the field and trying to figure out patterns of these very slow and intelligent animals . but over time , it is true they are very similar to us . and you think , `` well , how can i say that ? look , they have huge ears , they have really long noses . what do you mean they 're like us ? '' well , in fact , their families are very similar to ours . and family is extremely important to elephants . they grow up in very tight-knit families and they have extended families . and it 's just like our family reunions where you have all the aunts gathering around with all the food they 're going to bring and plan , and all the boys are thinking , `` are we going to play our video games together ? are we going to spar ? '' it 's very , very similar , and it 's jubilant , and screaming , yelling , it 's really amazing to see . but , as soon as you get that family gathering , it 's just like a wedding or anything else , all of the sudden the family politics come out , and the lower-ranking individuals in this scene , you see the arrow off to the back , the lower-ranking individuals already know their station , they 're going to drink at the muddiest part of the pan because the whole family 's here and we ca n't drink at the best water because that 's reserved for the top-ranking family . what 's also very similar is that you have elders in the group that everyone reveres . this is the matriarch , and the other female is reaching over and doing what 's called a trunk to mouth placing her trunk in the mouth , and it 's a sign of respect , it 's kind of like a handshake , but it 's also like a salute . and this salute is learned at a very young age . now , ritual and bonding within the family also facilitates coordinated activities . so , here 's a young female whose calf has fallen into the trough and she does n't know what to do and she panics . well , the older female , that 's the matriarch , she says , `` no problem here , '' she just scoops the baby out . now , that 's not true for a lot of different families , they ca n't coordinate very well , the younger females do n't really know what to do , but the older ones will just get down , kneel down together and pick the baby out . another thing that 's very similar is the coming of age of teenage boys . male elephants at the age of about 12 to 15 . the biggest elephant in this photograph here is an elephant who 's about the leave the family . he gets too big , he gets a little fresh , the adult females had enough of him , but he also is independent , he wants to go out and play with the guys . so what happens then is that you have this all male society , very ritual male society . greg is our main dominant bull here , you can see him in the middle . he 's got a huge posse , his following reveres him . and it 's very interesting how very good leaders , very good dominant individuals know how to titrate the carrot and the stick . this guy 's a master at it , and there 's other bullies out there that want to kind of want to create their own little following , but they ca n't do it because they 're too agressive . and so when he 's not around they try and sweet talk the underlings to come into their fold , and they actually become less agressive . so it 's very interesting to see how politics play out in these male and female societies . now back to the ladies here . in a core family group you 'll have a mother , maybe even a grandmother , her daughters and all of their offspring , the male and female calves . and what 's very interesting here is that how character makes a difference . so each matriarch has a very different character . these two characters are kind of curious , they 're uncertain , whereas these other two characters are really agressive . `` we 're going to charge first , ask questions later . '' but then there are also matriarchs that say , `` forget it ! i 'm going to run first and then figure it out when we 're in the bush and it 's safe . '' but the wisest matriarch , the matriarchs that succeed best in all of the studies that have been done , is the one that assesses the danger and decides is this worth running away from or is this not a big deal at all . now being social is super important for elephants and of course right at the beginning , just like early childhood development , socialization is very important . bathing together , eating together , playing together , rough housing , this is all very important for social development . and who has n't tried to beat their sibling to the head of the line coming into the water hole ? and these relationships from the beginning is just like best friends forever for real . these females are going to live together for life . now if it 's a male , female they might know each other for life , but it 's really important to develop those bonds early on . those are the relationships that are going to save you later . i 'll show you a little schoolyard scenario here . where , i think if you just focus on what 's happening here you can see that we have the bully , he 's pulling on the trunk of this baby calf , and then we have the diplomat who 's reaching over and saying , `` no , do n't do that ! stop doing that ! '' and then , of course , we have the bystander . and how do you get these three different characters within the family ? it 's kind of fascinating to think that elephants really are just like us . and so i got curious about this and i thought , `` well , what if you measure the difference in character of a dominant female 's calf versus a lower-ranking female 's calf , and see what happens in their growing up . '' and so we started doing this . and you can see this little guy with his ears out , really charging at you . the difference between that character and the character who holds back , wants to touch mom , is n't so certain about what 's going on here . but the other one 's charging ahead all confident . well , we started measuring how far away a calf will stray from mom , how often do they touch others , how often do they initiate play , and then look at the dominance of the females , of their mothers . and what we found is that socializing with the dominant calves actually socialize more significantly more than the lower-ranking calves . and what it looks like is it 's not that the lower-ranking calves do n't want to play , they 're actually not allowed to interact with the higher-ranking calves . they get swatted away from the dominant females . and so this is kind of the downside of , okay we are very much like elephants , elephants are as much like us , but it 's kind of for better or for worse because i can also see this happening in humans and maybe we should take a lesson from that . one last thing that we found is that the males will be the risk-takers , they 're more independent and they 're more likely to spend more time away from mom . and that 's very true in human societies and with other social animals . so i hope i 've convinced you that we have very similar lives to elephants and that elephants have very individual , durable characters that we 've measured across years . the bully always tends to be the bully unless there 's some kind of social upset , and he decides he better be a softy or else he 's not going to gain favor at all . and then you have the gentle giants that are always going to be gentle . the young males really need mentoring from the elders , and those gentle giants are very good at doing that , soliciting them . leaving family is a really hard things for the males , but they survive and they figure out who to hang out with . so , just to end here , i just wanted to say that since they are so similar to us , and have these characters , i hope when you see them on tv or you go out and you 're lucky enough to see them in the wild , that maybe you 'll think of them as individual characters deserving of our attention , and also deserving of our protection . thank you .
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and this salute is learned at a very young age . now , ritual and bonding within the family also facilitates coordinated activities . so , here 's a young female whose calf has fallen into the trough and she does n't know what to do and she panics .
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who is the one in charge of making decisions about safety within the family ?
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in 479 bc , when persian soldiers besieged the greek city of potidaea , the tide retreated much farther than usual , leaving a convenient invasion route . but this was n't a stroke of luck . before they had crossed halfway , the water returned in a wave higher than anyone had ever seen , drowning the attackers . the potiidaeans believed they had been saved by the wrath of poseidon . but what really saved them was likely the same phenomenon that has destroyed countless others : a tsunami . although tsunamis are commonly known as tidal waves , they 're actually unrelated to the tidal activity caused by the gravitational forces of the sun and moon . in many ways , tsunamis are just larger versions of regular waves . they have a trough and a crest , and consist not of moving water , but the movement of energy through water . the difference is in where this energy comes from . for normal ocean waves , it comes from wind . because this only affects the surface , the waves are limited in size and speed . but tsunamis are caused by energy originating underwater , from a volcanic eruption , a submarine landslide , or most commonly , an earthquake on the ocean floor caused when the tectonic plates of the earth 's surface slip , releasing a massive amount of energy into the water . this energy travels up to the surface , displacing water and raising it above the normal sea level , but gravity pulls it back down , which makes the energy ripple outwards horizontally . thus , the tsunami is born , moving at over 500 miles per hour . when it 's far from shore , a tsunami can be barely detectable since it moves through the entire depth of the water . but when it reaches shallow water , something called wave shoaling occurs . because there is less water to move through , this still massive amount of energy is compressed . the wave 's speed slows down , while its height rises to as much as 100 feet . the word tsunami , japanese for `` harbor wave , '' comes from the fact that it only seems to appear near the coast . if the trough of a tsunami reaches shore first , the water will withdraw farther than normal before the wave hits , which can be misleadingly dangerous . a tsunami will not only drown people near the coast , but level buildings and trees for a mile inland or more , especially in low-lying areas . as if that were n't enough , the water then retreats , dragging with it the newly created debris , and anything , or anyone , unfortunate enough to be caught in its path . the 2004 indian ocean tsunami was one of the deadliest natural disasters in history , killing over 200,000 people throughout south asia . so how can we protect ourselves against this destructive force of nature ? people in some areas have attempted to stop tsunamis with sea walls , flood gates , and channels to divert the water . but these are not always effective . in 2011 , a tsunami surpassed the flood wall protecting japan 's fukushima power plant , causing a nuclear disaster in addition to claiming over 18,000 lives . many scientists and policy makers are instead focusing on early detection , monitoring underwater pressure and seismic activity , and establishing global communication networks for quickly distributing alerts . when nature is too powerful to stop , the safest course is to get out of its way .
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when it 's far from shore , a tsunami can be barely detectable since it moves through the entire depth of the water . but when it reaches shallow water , something called wave shoaling occurs . because there is less water to move through , this still massive amount of energy is compressed .
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which of the following occur during wave shoaling ( choose all that apply ) ?
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if i were to distill the 20 years of elephant research that i 've done into one sentence , what would it be ? what could i tell you ? i would say that elephants are just like us ! and what do i mean by that ? it takes a lot of patience to be out there in the field and trying to figure out patterns of these very slow and intelligent animals . but over time , it is true they are very similar to us . and you think , `` well , how can i say that ? look , they have huge ears , they have really long noses . what do you mean they 're like us ? '' well , in fact , their families are very similar to ours . and family is extremely important to elephants . they grow up in very tight-knit families and they have extended families . and it 's just like our family reunions where you have all the aunts gathering around with all the food they 're going to bring and plan , and all the boys are thinking , `` are we going to play our video games together ? are we going to spar ? '' it 's very , very similar , and it 's jubilant , and screaming , yelling , it 's really amazing to see . but , as soon as you get that family gathering , it 's just like a wedding or anything else , all of the sudden the family politics come out , and the lower-ranking individuals in this scene , you see the arrow off to the back , the lower-ranking individuals already know their station , they 're going to drink at the muddiest part of the pan because the whole family 's here and we ca n't drink at the best water because that 's reserved for the top-ranking family . what 's also very similar is that you have elders in the group that everyone reveres . this is the matriarch , and the other female is reaching over and doing what 's called a trunk to mouth placing her trunk in the mouth , and it 's a sign of respect , it 's kind of like a handshake , but it 's also like a salute . and this salute is learned at a very young age . now , ritual and bonding within the family also facilitates coordinated activities . so , here 's a young female whose calf has fallen into the trough and she does n't know what to do and she panics . well , the older female , that 's the matriarch , she says , `` no problem here , '' she just scoops the baby out . now , that 's not true for a lot of different families , they ca n't coordinate very well , the younger females do n't really know what to do , but the older ones will just get down , kneel down together and pick the baby out . another thing that 's very similar is the coming of age of teenage boys . male elephants at the age of about 12 to 15 . the biggest elephant in this photograph here is an elephant who 's about the leave the family . he gets too big , he gets a little fresh , the adult females had enough of him , but he also is independent , he wants to go out and play with the guys . so what happens then is that you have this all male society , very ritual male society . greg is our main dominant bull here , you can see him in the middle . he 's got a huge posse , his following reveres him . and it 's very interesting how very good leaders , very good dominant individuals know how to titrate the carrot and the stick . this guy 's a master at it , and there 's other bullies out there that want to kind of want to create their own little following , but they ca n't do it because they 're too agressive . and so when he 's not around they try and sweet talk the underlings to come into their fold , and they actually become less agressive . so it 's very interesting to see how politics play out in these male and female societies . now back to the ladies here . in a core family group you 'll have a mother , maybe even a grandmother , her daughters and all of their offspring , the male and female calves . and what 's very interesting here is that how character makes a difference . so each matriarch has a very different character . these two characters are kind of curious , they 're uncertain , whereas these other two characters are really agressive . `` we 're going to charge first , ask questions later . '' but then there are also matriarchs that say , `` forget it ! i 'm going to run first and then figure it out when we 're in the bush and it 's safe . '' but the wisest matriarch , the matriarchs that succeed best in all of the studies that have been done , is the one that assesses the danger and decides is this worth running away from or is this not a big deal at all . now being social is super important for elephants and of course right at the beginning , just like early childhood development , socialization is very important . bathing together , eating together , playing together , rough housing , this is all very important for social development . and who has n't tried to beat their sibling to the head of the line coming into the water hole ? and these relationships from the beginning is just like best friends forever for real . these females are going to live together for life . now if it 's a male , female they might know each other for life , but it 's really important to develop those bonds early on . those are the relationships that are going to save you later . i 'll show you a little schoolyard scenario here . where , i think if you just focus on what 's happening here you can see that we have the bully , he 's pulling on the trunk of this baby calf , and then we have the diplomat who 's reaching over and saying , `` no , do n't do that ! stop doing that ! '' and then , of course , we have the bystander . and how do you get these three different characters within the family ? it 's kind of fascinating to think that elephants really are just like us . and so i got curious about this and i thought , `` well , what if you measure the difference in character of a dominant female 's calf versus a lower-ranking female 's calf , and see what happens in their growing up . '' and so we started doing this . and you can see this little guy with his ears out , really charging at you . the difference between that character and the character who holds back , wants to touch mom , is n't so certain about what 's going on here . but the other one 's charging ahead all confident . well , we started measuring how far away a calf will stray from mom , how often do they touch others , how often do they initiate play , and then look at the dominance of the females , of their mothers . and what we found is that socializing with the dominant calves actually socialize more significantly more than the lower-ranking calves . and what it looks like is it 's not that the lower-ranking calves do n't want to play , they 're actually not allowed to interact with the higher-ranking calves . they get swatted away from the dominant females . and so this is kind of the downside of , okay we are very much like elephants , elephants are as much like us , but it 's kind of for better or for worse because i can also see this happening in humans and maybe we should take a lesson from that . one last thing that we found is that the males will be the risk-takers , they 're more independent and they 're more likely to spend more time away from mom . and that 's very true in human societies and with other social animals . so i hope i 've convinced you that we have very similar lives to elephants and that elephants have very individual , durable characters that we 've measured across years . the bully always tends to be the bully unless there 's some kind of social upset , and he decides he better be a softy or else he 's not going to gain favor at all . and then you have the gentle giants that are always going to be gentle . the young males really need mentoring from the elders , and those gentle giants are very good at doing that , soliciting them . leaving family is a really hard things for the males , but they survive and they figure out who to hang out with . so , just to end here , i just wanted to say that since they are so similar to us , and have these characters , i hope when you see them on tv or you go out and you 're lucky enough to see them in the wild , that maybe you 'll think of them as individual characters deserving of our attention , and also deserving of our protection . thank you .
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and this salute is learned at a very young age . now , ritual and bonding within the family also facilitates coordinated activities . so , here 's a young female whose calf has fallen into the trough and she does n't know what to do and she panics .
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when elephant extended relatives greet , they have a ritual where one places their trunk in the other ’ s mouth as a form of greeting . they are also very vocal during greetings . do humans have similar greeting rituals ?
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an enduring myth says we use only 10 % of our brain , the other 90 % standing idly by for spare capacity . hucksters promised to unlock that hidden potential with methods `` based on neuroscience , '' but all they really unlock is your wallet . two-thirds of the public and nearly half of science teachers mistakenly believe the 10 % myth . in the 1890s , william james , the father of american psychology , said , `` most of us do not meet our mental potential . '' james meant this as a challenge , not an indictment of scant brain usage . but the misunderstanding stuck . also , scientists could n't figure out for a long time the purpose of our massive frontal lobes or broad areas of the parietal lobe . damage did n't cause motor or sensory deficits , so authorities concluded they did n't do anything . for decades , these parts were called silent areas , their function elusive . we 've since learned that they underscore executive and integrative ability , without which , we would hardly be human . they are crucial to abstract reasoning , planning , weighing decisions and flexibly adapting to circumstances . the idea that 9/10 of your brain sits idly by in your skull looks silly when we calculate how the brain uses energy . rodent and canine brains consume 5 % of total body energy . monkey brains use 10 % . an adult human brain , which accounts for only 2 % of the body 's mass , consumes 20 % of daily glucose burned . in children , that figure is 50 % , and in infants , 60 % . this is far more than expected for their relative brain sizes , which scale in proportion to body size . human ones weigh 1.5 kilograms , elephant brains 5 kg , and whale brains 9 kg , yet on a per weight basis , humans pack in more neurons than any other species . this dense packing is what makes us so smart . there is a trade-off between body size and the number of neurons a primate , including us , can sustain . a 25 kg ape has to eat 8 hours a day to uphold a brain with 53 billion neurons . the invention of cooking , one and half million years ago , gave us a huge advantage . cooked food is rendered soft and predigested outside of the body . our guts more easily absorb its energy . cooking frees up time and provides more energy than if we ate food stuffs raw and so we can sustain brains with 86 billion densely packed neurons . 40 % more than the ape . here 's how it works . half the calories a brain burns go towards simply keeping the structure intact by pumping sodium and potassium ions across membranes to maintain an electrical charge . to do this , the brain has to be an energy hog . it consumes an astounding 3.4 x 10^21 atp molecules per minute , atp being the coal of the body 's furnace . the high cost of maintaining resting potentials in all 86 billion neurons means that little energy is left to propel signals down axons and across synapses , the nerve discharges that actually get things done . even if only a tiny percentage of neurons fired in a given region at any one time , the energy burden of generating spikes over the entire brain would be unsustainable . here 's where energy efficiency comes in . letting just a small proportion of cells signal at any one time , known as sparse coding , uses the least energy , but carries the most information . because the small number of signals have thousands of possible paths by which to distribute themselves . a drawback of sparse coding within a huge number of neurons is its cost . worse , if a big proportion of cells never fire , then they are superfluous and evolution should have jettisoned them long ago . the solution is to find the optimum proportion of cells that the brain can have active at once . for maximum efficiency , between 1 % and 16 % of cells should be active at any given moment . this is the energy limit we have to live with in order to be conscious at all . the need to conserve resources is the reason most of the brain 's operations must happen outside of consciousness . it 's why multitasking is a fool 's errand . we simply lack the energy to do two things at once , let alone three or five . when we try , we do each task less well than if we had given it our full attention . the numbers are against us . your brain is already smart and powerful . so powerful that it needs a lot of power to stay powerful . and so smart that it has built in an energy-efficiency plan . so do n't let a fraudulent myth make you guilty about your supposedly lazy brain . guilt would be a waste of energy . after all this , do n't you realize it 's dumb to waste mental energy ? you have billions of power-hungry neurons to maintain . so hop to it !
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human ones weigh 1.5 kilograms , elephant brains 5 kg , and whale brains 9 kg , yet on a per weight basis , humans pack in more neurons than any other species . this dense packing is what makes us so smart . there is a trade-off between body size and the number of neurons a primate , including us , can sustain .
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the spiny anteater , echidna , has massive frontal lobes but isn ’ t very smart . if our frontal lobes were proportionally as large , we ’ d have to carry them in front of us in a wheelbarrow . if relative brain size doesn ’ t make us smarter than mammals that have much larger brains than we do—a point that has been argued for well over the past century—then what factor ( s ) might account for our relatively superior intelligence and flexibility ?
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about 66 million years ago , something terrible happened to life on our planet . ecosystems were hit with a double blow as massive volcanic eruptions filled the atmosphere with carbon dioxide and an asteroid roughly the size of manhattan struck the earth . the dust from the impact reduced or stopped photosynthesis from many plants , starving herbivores and the carnivores that preyed on them . within a short time span , three-quarters of the world 's species disappeared forever , and the giant dinosaurs , flying pterosaurs , shelled squids , and marine reptiles that had flourished for ages faded into prehistory . it may seem like the dinosaurs were especially unlucky , but extinctions of various severities have occurred throughout the earth 's history , and are still happening all around us today . environments change , pushing some species out of their comfort zones while creating new opportunities for others . invasive species arrive in new habitats , outcompeting the natives . and in some cases , entire species are wiped out as a result of activity by better adapted organisms . sometimes , however , massive changes in the environment occur too quickly for most living creatures to adapt , causing thousands of species to die off in a geological instant . we call this a mass extinction event , and although such events may be rare , paleontologists have been able to identify several of them through dramatic changes in the fossil record , where lineages that persisted through several geological layers suddenly disappear . in fact , these mass extinctions are used to divide the earth 's history into distinct periods . although the disappearance of the dinosaurs is the best known mass extinction event , the largest occurred long before dinosaurs ever existed . 252 million years ago , between the permian and triassic periods , the earth 's land masses gathered together into the single supercontinent pangaea . as it coalesced , its interior was filled with deserts , while the single coastline eliminated many of the shallow tropical seas where biodiversity thrived . huge volcanic eruptions occurred across siberia , coinciding with very high temperatures , suggesting a massive greenhouse effect . these catastrophes contributed to the extinction of 95 % of species in the ocean , and on land , the strange reptiles of the permian gave way to the ancestors of the far more familiar dinosaurs we know today . but mass extinctions are not just a thing of the distant past . over the last few million years , the fluctuation of massive ice sheets at our planet 's poles has caused sea levels to rise and fall , changing weather patterns and ocean currents along the way . as the ice sheets spread , retreated , and returned , some animals were either able to adapt to the changes , or migrate to a more suitable environment . others , however , such as giant ground sloths , giant hyenas , and mammoths went extinct . the extinction of these large mammals coincides with changes in the climate and ecosystem due to the melting ice caps . but there is also an uncomfortable overlap with the rise of a certain hominid species originating in africa 150,000 years ago . in the course of their adaptation to the new environment , creating new tools and methods for gathering food and hunting prey , humans may not have single-handedly caused the extinction of these large animals , as some were able to coexist with us for thousands of years . but it 's clear that today , our tools and methods have become so effective that humans are no longer reacting to the environment , but are actively changing it . the extinction of species is a normal occurrence in the background of ecosystems . but studies suggest that rates of extinction today for many organisms are hundreds to thousands of times higher than the normal background . but the same unique ability that makes humans capable of driving mass extinctions can also enable us to prevent them . by learning about past extinction events , recognizing what is happening today as environments change , and using this knowledge to lessen our effect on other species , we can transform humanity 's impact on the world from something as destructive as a massive asteroid into a collaborative part of a biologically diverse future .
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as the ice sheets spread , retreated , and returned , some animals were either able to adapt to the changes , or migrate to a more suitable environment . others , however , such as giant ground sloths , giant hyenas , and mammoths went extinct . the extinction of these large mammals coincides with changes in the climate and ecosystem due to the melting ice caps . but there is also an uncomfortable overlap with the rise of a certain hominid species originating in africa 150,000 years ago .
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the relatively recent extinction of large mammals such as mammoths was caused by _____________ .
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i know , insects , it 's really weird , but bear with me . now , i am an entomologist . i confess to that . and , when i look at the planet , the reason i 'm an entomologist is because out of the 1.9 million species that are described on planet earth , over 1 million of them are insects . and i truly believe as a scientist today we live in the best of times because here we are enjoying ted , and facebook , and youtube , and this wonderful theater , healthcare , longer life spans . but we also live in the worst of times because we are on a planet with 7 billion people with a lot of problems . and for those of us who look at biodiversity , it 's a heart-wrenching and wonderful time all together because we see the links between nature and people , and we 're losing them at the same time . both honeybees and humans originate in east africa . and , here in kenya , a wonderful relationship exists where a bird called a honeyguide , up there , has this interesting phenomenon where it actually leads either humans , which it 's done for thousands of years , 77,000 year old paintings from tanzania , and the honey badger to the wild honeybee colony . now , for a long time we thought this relationship first evolved between the honeyguide and the honey badger . but it turns out that it actually evolved between the human and the honeyguide , and the badger 's a parasite . now , when we look at bees , there is this amazing diversity out there , 20,000 species . and one in three bites of food that we eat is thanks to an insect pollinator . so one of the things i 'm working on is looking at those links between nature and sustainable human life . and here are just a few of the beautiful bees that we have in kenya , in fact , not far from nairobi . now , how many of you like coffee ? yeah , i actually ca n't drink it because if i do , my hands shake , and i ca n't pick up ants and bees . chocolate ? i love chocolate , the darker the better , so i really like chocolate . now the thing is , without insect pollinators , there would be very little coffee and no chocolate on the planet . could you imagine that ? that 's really scary ! now , i want to show you out of thousands of examples that i could have brought here today to show you how insects are connected to your life , to every single human being on the planet . here are two colleagues and friends . domina is a farmer in mwanza in western tanzania , and peter is from the kerio valley in northwestern kenya . now , domina grows pigeon feed , cow feed , a whole wide range of legumes . and she feeds her family , she survives in a very remote area based off of these amazing crops , legumes , a lot of traditional vegetables , and all of them are pollinated by these different wild bee species . now , peter grows five varieties of mango on his farm , and he actually paid for his education by growing and selling mangoes . and i really like mangoes and so it 's really a great pleasure working on the farm with five different varieties of mango . and if you look at all these different fruits and crops here , one thing that connects us to biodiversity and one thing we do as a scientist , we write papers . we do research , and we write papers . nobody ever reads them , but here 's one of my papers . it 's on the african violet . this is in the u.s . this florist sells about 10,000 dollars worth of violets a year . it 's worth about 6 billion dollars in trade . it originates in east africa , and we never knew what pollinated it . well , i went off and studied this . one thing to say about pollinators is it comes done to being about sex . and how many of you like sex ? where are we , the vatican ? so what happens when insects help plants have sex is there 's really good sex . this is an example of really good sex . so basically the bee comes along , it vibrates the flower at a specific frequency , 11 to 12 hertz , pollen is released , and the plant survives in the wild . this is one of the world 's most endangered plants . we go up into the deserts of northern kenya , which are now very famous because of the discovery of oil . but i will tell you a little different story . these animals , the camel , which allow life in this very remote community , are browsing off of a shrub called indigofera , and indigofera is 100 % dependent on bee pollination . so all these wild bees produce the indigofera , which the camels and goats eat . and we look at a community like this , nalaray , northern samburu , and people will look at these children and say they are poor . and i disagree because over lunch we collected 30 different bee species in the acacia where they had their lunch and 400 pollinator species in the acacia tortilis where their classroom is located . so i want to leave you with a radical piece of technology called the bee hotel that you can innovate and build for yourself . create a habitat where bees can nest and live in your own backyard . but more importantly , please create space in your hearts for insects . spend five minutes a day with them if you can . and i believe that if the one lesson we can learn from insects is that meek shall inherit the earth .
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both honeybees and humans originate in east africa . and , here in kenya , a wonderful relationship exists where a bird called a honeyguide , up there , has this interesting phenomenon where it actually leads either humans , which it 's done for thousands of years , 77,000 year old paintings from tanzania , and the honey badger to the wild honeybee colony . now , for a long time we thought this relationship first evolved between the honeyguide and the honey badger . but it turns out that it actually evolved between the human and the honeyguide , and the badger 's a parasite .
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what is the relationship between the honeybee and the badger ?
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feldspar mineral ... from the ytterby quarry . how many elements does it contain ? shall we take it home ? so terbium , just like europium , is often used in television screens and various types of displays and where it comes in is that it gives green and yellow colours , which in contrast to the red and blue which europium gives you , gives you the full selection that you need to give colour images . so ytterby gruva , ytterby mine , what a great place , the snow is falling . this is designated ytterby mine , a historical landmark for the discovery of four periodic elements : yttrium , terbium , erbium , and ytterbium . terbium was eventually discovered or eventually isolated by the chemist mosander in 1843 . it was from an earth called itrea which was originated in this quarry where we are right now in ytterby in sweden . terbium is a really unusual element . it ’ s a metal ; moderate abundance . it ’ s called a rare earth element , which is really quite ironic because it ’ s not as rare as its name would suggest . the abundance is something like 20 to 30 times that of silver , so i don ’ t think it ’ s really rare . it doesn ’ t really have much biological activity but we do find terbium within the bones in the human body and in animals but also within the kidneys so you do find small concentrations but it doesn ’ t really have a perceived biological activity . terbium is also used in certain magnetic devices and when you include it in certain alloys it forms magnetic devices which increase or decrease in size depending on the strength or type of magnetic field which they are placed into which has various technological applications . so terbium alloys are really quite interesting because they have what ’ s called magnetostrictive behaviour . so what that means is that the size of the crystal or the size of the structure of the alloy itself gets either larger or smaller when it ’ s exposed to a large or strong magnetic field . so , there ’ s much research going into these terbium alloys for small motors or small switches perhaps and also to use as strain gauges and other types of really quite elaborate instruments . so these may well provide us a lot of new research in the areas of nano-science and nano-machines . also , because of its fluorescence nature it ’ s often used as a marker in biochemistry so if you want to stain cells and determine whether certain types are present then you can use it for that too . so in terms of day-to-day life , where do we find terbium ? well we find it in unusual devices like energy-saving light-bulbs because it stimulates or it increases the yield of light in the mercury discharge that we use to run fluorescent strips . so we found it around us in shops and houses , in factories , street-lighting , everywhere . but what i think is a really quite nice and important application of terbium is the fact that it ’ s used to make phosphorescent materials . so these are materials which generate light or allow us to develop pictures if we irradiate them with something like an x-ray . and , in fact , terbium is used to make very , very high light yielding phosphors for use in screens and visualisation screens for x- rays . so what this means is that if i go into the hospital for diagnostic x- ray i no longer have to be exposed to long periods of x-rays because the terbium screen allows the generation of the pictures at much , much lower dose of x-ray . so it ’ s really quite a significant advance . it ’ s really quite nice chemistry as well .
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shall we take it home ? so terbium , just like europium , is often used in television screens and various types of displays and where it comes in is that it gives green and yellow colours , which in contrast to the red and blue which europium gives you , gives you the full selection that you need to give colour images . so ytterby gruva , ytterby mine , what a great place , the snow is falling .
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terbium was used in television screens , but in contrast to europium , terbium gives off these other colors :
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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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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 .
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scientists think sleep paralysis is caused by an overlap of what two stages of sleep ?
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the story of the buddha ’ s life , like all of buddhism , is a story about confronting suffering . he was born between the sixth and fourth century b.c. , the son of a wealthy king in the himalayan foothills of nepal . it was prophesied that the young buddha — then called siddhartha gautama — would either become the emperor of india or a very holy man . since siddhartha ’ s father desperately wanted him to become the former , he kept the child isolated in a palace . young gautama had every imaginable luxury : jewels , servants , lotus ponds , even beautiful dancing women . for 29 years , gautama lived in bliss , protected from the smallest misfortunes of the outside world but then , he left the palace for short excursions . what he saw amazed him : first he met a sick man , then an aging man , and then a dying man . show these kind of people in india—add them to the same image one by one he was astounded to discover that these unfortunate people represented normal—indeed , inevitable—parts of the human condition that would one day touch him , too . horrified and fascinated , gautama made a fourth trip outside the palace walls—and encountered a holy man , who had learned to seek spiritual life in the midst of the vastness of human suffering . inspired by the holy man , gautama left the palace for good . he tried to learn from other holy men . he almost starved himself to death by avoiding all physical comforts and pleasures , as they did . perhaps unsurprisingly , it did not bring him solace from suffering . then he thought of a moment when he was a small boy : sitting by the river , he ’ d noticed that when the grass was cut , the insects and their eggs were trampled and destroyed . as a child , he ’ d felt a deep compassion for the tiny insects . reflecting on his childhood compassion , gautama felt a profound sense of peace . he ate , meditated , and finally reached the highest state of enlightenment : nirvana it refers to the “ blowing out ” of the flames of desire . with this , gautama had become the buddha , “ the awakened one ” . the buddha awoke by recognising that all of creation , from distraught ants to dying human beings , is unified by suffering . recognising this , the buddha discovered how to best approach suffering . first , one shouldn ’ t bathe in luxury , nor abstain from food and comforts altogether . instead , one ought to live in moderation . the buddha called this the middle way this allows for maximal concentration on cultivating compassion for others and seeking enlightenment next , the buddha described a path to transcending suffering called the four noble truths the first noble truth is the realisation that first prompted the buddha ’ s journey : that there is suffering and constant dissatisfaction in the world . the second is that this suffering is caused by our desires . as the buddha said , “ attachment is the root of all suffering. ” the third truth is that we can transcend suffering by removing or managing these desires . the buddha thus made the remarkable claim that we must change our outlook , not our circumstances . we are unhappy not because we don ’ t have enough money , love or status but because we are greedy , vain , and insecure . by re-orienting our mind we can grow to be content . the people become happier—superimpose smiles or use a second image of their face with the correct behaviour and what we now term a mindful attitude , we can also become better people . we can invert negative emotions and states of mind , turning ignorance into wisdom , anger into compassion , and greed into generosity . the fourth and final noble truth the buddha uncovered is that we can learn to move beyond suffering through what he termed the noble eightfold path . the eightfold path involves a series of aspects of behaving “ right ” and wisely : right view , right intention , right speech , right action , right livelihood , right effort , right mindfulness , and right concentration . what strikes the western observer is the notion that wisdom is a habit , not merely an intellectual realisation . one must exercise one ’ s nobler impulses on a regular basis , as one would train a limb . the moment of understanding is only one part of becoming a better person . after his death , the buddha ’ s followers collected his “ sutras ” ( sermons or sayings ) into scripture , and developed texts to guide followers in meditation , ethics , and mindful living . the monasteries that had developed during the buddha ’ s lifetime grew and multiplied , throughout china and east asia . for a time , buddhism was particularly uncommon in india itself , and only a few quiet groups of yellow-clad monks and nuns roamed the countryside , meditating quietly in nature . but then , in the 3rd century b.c. , an indian king named ashoka grew troubled by the wars he had fought and converted to buddhism . he sent monks and nuns far and wide to spread the practice . buddhist spiritual tradition spread across asia and eventually throughout the world . buddha ’ s followers divided into two main schools : theravada buddhism which colonised southeast asia , and mahayana buddhism which took hold in china and northeast asia . today , there are between a half and one and a half billion buddhists in both east and west following the buddha ’ s teachings and seeking a more enlightened and compassionate state of mind . intriguingly , the buddha ’ s teachings are important regardless of our spiritual identification . like the buddha , we are all born into the world not realising how much suffering it contains , and unable to fully comprehend that misfortune , sickness , and death will come to us too . as we grow older , this reality often feels overwhelming , and we may seek to avoid it altogether . but the buddha ’ s teachings remind us of the importance of facing suffering directly . we must do our best to liberate ourselves from the grip of our own desires , and recognise that suffering can be viewed as part of our common connection with others , spurring us to compassion and gentleness .
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reflecting on his childhood compassion , gautama felt a profound sense of peace . he ate , meditated , and finally reached the highest state of enlightenment : nirvana it refers to the “ blowing out ” of the flames of desire . with this , gautama had become the buddha , “ the awakened one ” .
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what does it mean to reach a state of nirvana ?
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what gives the trumpet its clarion ring and the tuba its gut-shaking `` omm pah pah ? '' and what makes the trombone so jazzy ? the answer lies not in the brass these instruments are made of , but in the journey air takes from the musician 's lungs to the instrument 's bell . like any sound , music consists of vibrations traveling through air . instruments are classified based on how those vibrations are produced . percussion instruments are struck . string instruments are plucked or bowed . woodwinds have air blown against a reed or sharp edge . for brass instruments , however , the vibration come directly from the musician 's mouth . one of the first things a brass player must learn is to breathe in deeply , until every possible particle of air is crammed into the lungs . once all that air is inside , it must come out through the mouth , but there , an internal battle takes place as the musician simultaneously tries to hold their lips firmly closed while blowing enough air to force them open . the escaping air meets resistance from the lip muscles , forms an opening called the aperture and creates the vibration that brass players call `` the buzz . '' when a mouthpiece is held up to those vibrating lips , it slightly refines the buzz , amplifying the vibration at certain frequencies . but things get really interesting depending on what instrument is attached to that mouthpiece . a brass instrument 's body is essentially a tube that resonates with the air column blowing through it . the way that sound waves travel through this column forms a limited pattern of pitches known as the harmonic series , with notes spaced far apart at the lower end , but coming closer together as the pitch increases . the musician can alter the pitch of the note through slight contractions of the lips and alterations to air volume and speed . slower , warm sighing air produces lower pitches , and faster , cool , flowing air produces higher pitches in the series . but any single harmonic series has gaps where pitches are missing and the versatility of brass instruments lies in their ability to switch between multiple series . on instruments like the trumpet , valves can be lowered to increase the length of tubing the air travels through , while on a trombone , this is done by extending its slide . lengthening the tube stretches the vibrating air column , reducing the frequency of vibrations and resulting in a lower pitch . this is why the tuba , the largest brass instrument , is also the one capable of playing the lowest notes . so changing the instrument length shifts its harmonic series , while slight variations of the air flow and the player 's lips produce the different notes within it . and those notes finally emerge through the flared bell opening at the end . what started as a deep breath and a vibrating buzz on the lips has now been transformed into a bold and brassy tune . the musician 's skillful manipulation of every part of the process from lungs , to lips , to the mouthpiece , to the instrument itself creates an amazing palette of pitches that can be heard in musical genres across the globe . by harnessing the power of natural resonance in a flexible and controllable way , brass instruments are great examples of the fusion of human creativity with the physics of our world .
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slower , warm sighing air produces lower pitches , and faster , cool , flowing air produces higher pitches in the series . but any single harmonic series has gaps where pitches are missing and the versatility of brass instruments lies in their ability to switch between multiple series . on instruments like the trumpet , valves can be lowered to increase the length of tubing the air travels through , while on a trombone , this is done by extending its slide .
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the harmonic series _____ .
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ok so gadolinium is smack-bang in the middle of the 4f series . it ’ s perhaps most famous for the fact that it ’ s used as a contrast reagent in mri machines . so if you need a full body scan , a doctor will come along an inject you with a solution which contains a bit of gadolinium and what it basically does is that it changes the way that molecules , water molecules react in your body when they are scanned and then you can see the contrast between healthy tissue and , perhaps , unhealthy tissue and then that aids the doctors in their assignment . the thing about the lanthanide series is that it ’ s probably the best example of a smooth contraction in size as you move from the left-hand side to the right-hand side and you lose about 25 % of the radius of the atoms as you move from the left to the right and this is called the ‘ lanthanide contraction. ’ this is actually what ’ s responsible for 2nd and 3rd row transition metals having very similar types of chemistry by group even though actually they should be quite different . the 3rd row should be much larger but , because of the ‘ lanthanide contraction ’ , that increase in size is counterbalanced so they actually end up being more- or-less the same size as their 2nd row counterparts . even chemists sometimes wonder how people can get excited about particular parts of chemistry , and the rare earth elements are elements which , those who are not working in the area don ’ t always see why it can be very exciting . so when i was a student i saw an advertisement in the lab where i was working about a lecture about the oxidation states of the rare earth elements , and the relative stability of two of the oxidation states by a chemist called david johnson , who in those days worked for the open university . and , i went to this lecture because i couldn ’ t imagine how anybody could make it interesting , and it was really fascinating ! he was so enthusiastic and so on , by the end , i rushed out really quite excited i went and bought this book which has been sitting on my bookshelf ever since and has been quite useful for teaching some of my students .
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ok so gadolinium is smack-bang in the middle of the 4f series . it ’ s perhaps most famous for the fact that it ’ s used as a contrast reagent in mri machines .
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one peculiarity of gadolinium is that it has a curie point very close to room temperature , namely at 19 ºc . so at room temperature gadolinium is…
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are you familiar with the word symbiosis ? it 's a fancy term for a partnership between two different species , such as bees and flowers . in a symbiosis , both species depend on each other . i want to tell you about a remarkable symbiosis between a little bird , the clark 's nutcracker , and a big tree , the whitebark pine . whitebark grow in the mountains of wyoming , montana and other western states . they have huge canopies and lots of needles , which provide cover and shelter for other plants and animals , and whitebark feed the forest . their cones are packed with protein . squirrels gnaw the cones from the upper branches so they fall to the ground , and then race down to bury them in piles , or middens . but they do n't get to keep all of them ; grizzlies and black bears love finding middens . but there 's more to a symbiosis than one species feeding another . in the case of the clark 's nutcracker , this bird gives back . while gathering its seeds , it also replants the trees . here 's how it works : using her powerful beak , the nutcracker picks apart a cone in a treetop , pulling out the seeds . she can store up to 80 of them in a pouch in her throat . then she flies through the forest looking for a place to cache the seeds an inch under the soil in piles of up to eight seeds . nutcrackers can gather up to 90,000 seeds in the autumn , which they return for in the winter and spring . and these birds are smart . they remember where all those seeds are . they even use landmarks on the landscape -- trees , stumps , rocks -- to triangulate to caches buried deep under the snow . what they do n't go back and get , those seeds become whitebark . this symbiosis is so important to both species that they 've changed , or evolved , to suit each other . nutcrackers have developed long , tough beaks for extracting seeds from cones , and whitebarks ' branches all sweep upwards with the cones at the very ends , so they can offer them to the nutcrackers as they fly by . that 's a symbiosis : two species cooperating to help each other for the benefit of all .
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in a symbiosis , both species depend on each other . i want to tell you about a remarkable symbiosis between a little bird , the clark 's nutcracker , and a big tree , the whitebark pine . whitebark grow in the mountains of wyoming , montana and other western states .
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where does the clark ’ s nutcracker store whitebark pine seeds , and how many can it store there ?
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translator : bedirhan cinar reviewer : jessica ruby mysteries of vernacular : dynamite , an explosive consisting of nitroglycerin , typically molded into sticks . dynamite , which coincidentally is closely related to the word dynasty , has as much to do with familial persuasion as it does etymology . following in the footsteps of his inventor father , alfred nobel took up engineering . in 1850 , he was exposed to the work of ascanio sobrero , the chemist who invented nitroglycerin . more powerful than gun powder and extremely unpredictable , this highly explosive liquid captivated alfred . working closely with his father , he began experimenting with nitroglycerin , searching for a practical application for the compound . after several explosions , including one that killed alfred 's brother , authorities banned nitroglycerin tests within stockholm city limits . undeterred , alfred moved his lab and began experimenting with additives , eventually finding one that transformed the dangerous liquid into malleable paste , easier to handle and perfect for construction sites . he named this material dynamite , from the greek dunamis , meaning power , and the common scientific suffix -ite . explosives made alfred a very wealthy man . and , in an effort to balance the destruction caused by his invention , he created an endowment that would award nobel prizes to authors , scientists , and advocates of world peace for generations to come .
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dynamite , which coincidentally is closely related to the word dynasty , has as much to do with familial persuasion as it does etymology . following in the footsteps of his inventor father , alfred nobel took up engineering . in 1850 , he was exposed to the work of ascanio sobrero , the chemist who invented nitroglycerin .
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what was alfred nobel 's profession ?
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translator : andrea mcdonough reviewer : bedirhan cinar what is a cartoon really ? many of us love cartoons , most of us grew up reading them or having them read to us . the fact is , cartoons have been around a long time . there are all kinds of cartoons : strip comics , comic books , political cartoons , single-panel cartoons , graphic novels , web comics , animation , caricature , there is something for everyone . no matter the form them come in , cartoons elicit all kinds of emotions from the viewer - happiness , sadness , anger , hilarity , calm - and can transmit ideas in an instant . cartoons are a universal medium enjoyed and understood around the world and across borders . this is why they have survived so long as an art form . but how can a medium that is on the surface so simple have so much influence and at times be so meaningful ? let 's look at what a cartoon is . it starts with an idea . the idea can be verbal , written in words , or it can be visual . a visual idea is simply a picture , a drawing , a doodle . these ideas come from a variety of places . cartoonists might find the idea from observing life , reading a newspaper , trawling online . it can come from a sentence someone said or a single word heard on television . cartoonists are like sponges ; they soak up people , places , mannerisms , clothing , and behavior . sometimes they might jot them down in a little black book that they carry around with them . other times , it is just soaked up into the cartoonist 's brain only to be squeezed out later when she is sitting at her drawing table . not only does a cartoonist have to be aware of what she is seeing visually , but she has to listen to herself think . in other words , take the incoming information and select it , shape it , and then use it for a cartoon . now that you have an idea , or something you think could be good for a cartoon , it 's time to shape it . a cartoon is like a staged play . a cartoonist is playwright , director , stage designer , choreographer , and costume designer . a cartoon has characters , a set , dialogue , even if one line , and a backstory . the characters must be dressed to fit the idea , speak in a way that is natural and forwards the idea or gives the punchline . nothing should be in the cartoon that is not absolutely necessary for the advancement of the idea . the image and words have to < i > dance < /i > together in a way that makes sense . it could be a graceful dance , or an awkward dance , if that is part of the humor or idea . and then the execution . some cartoonists sketch the idea with pencil then ink it with pen using a light box . others visualize the image in their head and draw directly on the paper in pen . different kinds of pens are used : felt-tip , mechanical pen , or a crow quill . paper can be light-weight or heavy-bond . many cartoonists add gray tone , called a wash , by using black watercolor and a brush . others use a soft pencil for the tone . color is usually created by using watercolor . a finished cartoon can then be scanned and adjusted , and the caption can be added on the computer with photoshop . new technologies are emerging for the cartoonist 's use in creating her cartoon . photoshop can serve as a tool for color and image . some may draw directly on a tablet with a stylus . the choices at this stage of creation work in tandem with the idea , and often when the final caption is added , it gets adjusted yet again . but , little is left to chance , except , perhaps , some of the watercolor . all these elements function in concert with one another . it 's almost like a dance of words , ideas , and images that work together in order to make the cartoon a timeless , resilient work of art .
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a finished cartoon can then be scanned and adjusted , and the caption can be added on the computer with photoshop . new technologies are emerging for the cartoonist 's use in creating her cartoon . photoshop can serve as a tool for color and image .
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what analogy does donnelly give to illustrate the many roles a cartoonist plays in developing a cartoon ?
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your body is a temple , but it ’ s also a museum of natural history . look closely and you ’ ll see parts that aren ’ t there because you need them but because your animal ancestors did . no longer serving their previous function but not costly enough to have disappeared , these remnants of our deep history only make sense within the framework of evolution by natural selection . with your arm on a flat surface , push your thumb against your pinky and tip your hand slightly up . if you see a raised band in the middle of the wrist , you ’ ve got a vestigial muscle in your forearm . that tendon you see connects to the palmaris longus , a muscle that around 10-15 % of people are missing on one or both of their arms . it doesn ’ t make them any weaker though . there ’ s no difference in grip strength . in fact , it ’ s one of the first tendons that surgeons will take out so they can use it in reconstructive and cosmetic surgeries . you can find the palmaris longus across mammal species , but it ’ s most developed among those that use their forelimbs to move around . in primates , that means the muscle is longer in lemurs and monkeys and shorter in chimps , gorillas , and other apes that don ’ t do a lot of scrambling through trees . it ’ s not the only leftover muscle that we 've got . look at the three that are attached to our outer ear . we can ’ t get much movement out of these muscles , especially compared to some of our mammal relatives who use them to locate the sources of sounds . presumably this would have been quite helpful for early nocturnal mammals . in humans , you can still detect the remnants of this adaptation with electrodes . in one study researchers recorded a spike of activity in the ear muscle cells in response to a sudden sound . not enough to move the ear , but detectable . and you can probably guess the location of the sound based on the results - it came from a speaker to the left of the study subjects . so this is their left ear subconsciously trying ( and failing ) to pivot toward the sound . you can see another futile effort by our vestigial body parts when you get goosebumps . when we ’ re cold , tiny muscles attached to our body hairs contract , pulling the hair upright which causes the surrounding skin to form a bump . for our furry mammal relatives , the raised hair increases the amount of space for insulation , helping them stay warm . birds can do this too . you ’ ve probably seen a puffy pigeon on a cold day . adrenaline is one of the hormones involved in the body ’ s response to cold temperatures , and it ’ s also part of the fight or flight response . so it helps some animals appear larger when they ’ re threatened . and it may be why surprising and emotional turns in music can give some people goosebumps . and then there ’ s our tail . at the end of our spine are a set of fused vertebrae - some people have 3 , some have 5 . we call it the tailbone . it now serves as an anchor for some pelvic muscles but it ’ s also what ’ s left of our ancestors ’ tails . every one of us actually had a tail at one point . when the basic body plan is being laid out at around 4 weeks of gestation , humans embryos closely resemble embryos of other vertebrates . and that includes a tail with 10-12 developing vertebrae . in many other animals it continues to develop into a proper tail . but in humans and other apes , the cells in the tail are programmed to die a few weeks after they appear . vary rarely though , a mutation allows the ancestral blueprint to prevail and a human baby will be born with a true vestigial tail . the most adorable vestigial behavior is the palmar grasp reflex , where infants up until they ’ re about 6 months old have this incredible grasp on whatever you put in their hand . there ’ s a similar reflex for their feet . i wanted to show you this great piece of footage from the 1930s where they demonstrated this behavior . these babies are only 1 month old and you can see that their inner monkey can support their entire weight .
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your body is a temple , but it ’ s also a museum of natural history . look closely and you ’ ll see parts that aren ’ t there because you need them but because your animal ancestors did .
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what are tailbones made out of ?
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it 's the first sense you use when you 're born . one out of every fifty of your genes is dedicated to it . it must be important , right ? okay , take a deep breath through your nose . it 's your sense of smell , and it 's breathtakingly powerful . as an adult , you can distinguish about 10,000 different smells . here 's how your nose does it . smell starts when you sniff molecules from the air into your nostrils . 95 % of your nasal cavity is used just to filter that air before it hits your lungs . but at the very back of your nose is a region called the olfactory epithelium , a little patch of skin that 's key to everything you smell . the olfactory epithelium has a layer of olfactory receptor cells , special neurons that sense smells , like the taste buds of your nose . when odor molecules hit the back of your nose , they get stuck in a layer of mucus covering the olfactory epithelium . as they dissolve , they bind to the olfactory receptor cells , which fire and send signals through the olfactory tract up to your brain . as a side note , you can tell a lot about how good an animal 's sense of smell is by the size of its olfactory epithelium . a dog 's olfactory epithelium is 20 times bigger than your puny human one . but there 's still a lot we do n't know about this little patch of cells , too . for example , our olfactory epithelium is pigmented , and scientists do n't really know why . but how do you actually tell the difference between smells ? it turns out that your brain has 40 million different olfactory receptor neurons , so odor a might trigger neurons 3 , 427 , and 988 , and odor b might trigger neurons 8 , 76 , and 2,496,678 . all of these different combinations let you detect a staggeringly broad array of smells . olfactory neurons are always fresh and ready for action . they 're the only neuron in the body that gets replaced regularly , every four to eight weeks . once they are triggered , the signal travels through a bundle called the olfactory tract to destinations all over your brain , making stops in the amygdala , the thalamus , and the neocortex . this is different from how sight and sound are processed . each of those signals goes first to a relay center in the middle of the cerebral hemisphere and then out to other regions of the brain . but smell , because it evolved before most of your other senses , takes a direct route to these different regions of the brain , where it can trigger your fight-or-flight response , help you recall memories , or make your mouth water . but even though we 've all got the same physiological set-up , two nostrils and millions of olfactory neurons , not everybody smells the same things . one of the most famous examples of this is the ability to smell so-called `` asparagus pee . '' for about a quarter of the population , urinating after eating asparagus means smelling a distinct odor . the other 75 % of us do n't notice . and this is n't the only case of smells differing from nose to nose . for some people , the chemical androstenone smells like vanilla ; to others , it smells like sweaty urine , which is unfortunate because androstenone is commonly found in tasty things like pork . so with the sweaty urine smellers in mind , pork producers will castrate male pigs to stop them from making androstenone . the inability to smell a scent is called anosmia , and there are about 100 known examples . people with allicin anosmia ca n't smell garlic . those with eugenol anosmia ca n't smell cloves . and some people ca n't smell anything at all . this kind of full anosmia could have several causes . some people are born without a sense of smell . others lose it after an accident or during an illness . if the olfactory epithelium gets swollen or infected , it can hamper your sense of smell , something you might have experienced when you were sick . not being able to smell anything can mess with your other senses , too . many people who ca n't smell at all also ca n't really taste the same way the rest of us do . it turns out that how something tastes is closely related to how it smells . as you chew your food , air is pushed up your nasal passage , carrying with it the smell of your food . those scents hit your olfactory epithelium and tell your brain a lot about what you 're eating . without the ability to smell , you lose the ability to taste anything more complicated than the five tastes your taste buds can detect : sweet , salty , bitter , sour , and savory . so , the next time you smell exhaust fumes , salty sea air , or roast chicken , you 'll know exactly how you 've done it and , perhaps , be a little more thankful that you can .
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the inability to smell a scent is called anosmia , and there are about 100 known examples . people with allicin anosmia ca n't smell garlic . those with eugenol anosmia ca n't smell cloves . and some people ca n't smell anything at all . this kind of full anosmia could have several causes .
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many people who ca n't smell anything also ca n't ________ .
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far beneath the palace of the treacherous king minos , in the damp darkness of an inescapable labryinth , a horrific beast stalks the endless corridors of its prison , enraged with a bloodlust so intense that its deafening roar shakes the earth . it is easy to see why the minotaur myth has a long history of being disregarded as pure fiction . however , there 's a good chance that the minotaur and other monsters and gods were created by our early ancestors to rationalize the terrifying things that they saw in the natural world but did not understand . and while we ca n't explain every aspect of their stories , there may be some actual science that reveals itself when we dissect them for clues . so , as far as we know , there have never been human-bull hybrids . but the earliest material written about the minotaur does n't even mention its physical form . so that 's probably not the key part of the story . what the different tellings do agree upon , however , is that the beast lives underground , and when it bellows , it causes tremendous problems . the various myths are also specific in stating that genius inventor daedalus , carved out the labyrinth beneath the island of crete . archeological attempts to find the fabled maze have come up empty handed . but crete itself has yielded the most valuable clue of all in the form of seismic activity . crete sits on a piece of continental crust called the aegean block , and has a bit of oceanic crust known as the nubian block sliding right beneath it . this sort of geologic feature , called a subduction zone , is common all over the world and results in lots of earthquakes . however , in crete the situation is particularly volatile as the nubian block is attached to the massive buoyant continental crust that is africa . when the nubian block moves , it does not go down nearly as easily or as steeply as oceanic crust does in most other subduction zones . instead , it violently and abruptly forces sections of the mediterranean upwards in an event called uplift , and crete is in uplift central . in the year 2014 , crete had more than 1300 earthquakes of magnitude 2.0 or higher . by comparison , in the same period of time , southern california , a much larger area , experienced a mere 255 earthquakes . of course , we do n't have detailed seismic records from the days of king minos , but we do know from fossil records and geologic evidence that crete has experienced serious uplift events that sometimes exceeded 30 feet in a single moment . contrast this for a moment with the island of hawaii , where earthquakes and volcanic activity were tightly woven to legends surrounding pele , a goddess both fiery and fair . like the minotaur , her myths included tales of destruction , but they also contained elements of dance and creation . so why did hawaii end up with pele and crete end up with the minotaur ? the difference likely comes down to the lava that followed many of hawaii 's worst earthquakes . the lava on hawaii is made of basalt , which once cooled , is highly fertile . within a couple of decades of terrible eruptions , islanders would have seen vibrant green life thriving on new peninsulas made of lava . so it makes sense that the mythology captured this by portraying pele as creator as well as a destroyer . as for the people of crete , their earthquakes brought only destruction and barren lands , so perhaps for them the unnatural and deadly minotaur was born . the connections between mythical stories and the geology of the regions where they originated teach us that mythology and science are actually two sides of the same coin . both are rooted in explaining and understanding the world . the key difference is that where mythology uses gods , monsters and magic , science uses measurements , records and experiments .
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so , as far as we know , there have never been human-bull hybrids . but the earliest material written about the minotaur does n't even mention its physical form . so that 's probably not the key part of the story .
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where did the ancient greeks believe the minotaur lived ?
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there are some shark species that seem to do okay in aquariums . you ’ ll see a lot of nurse sharks , zebra sharks , some reef sharks and sand tiger sharks . but not the great white . for decades , aquariums have tried to contain the world ’ s largest predatory fish . institutions like marineland , seaworld and the steinhart aquarium repeatedly took in white sharks during the 1970s , 80s and 90s , at times drawing huge crowds . but they never lasted long . some needed help swimming . none of them would eat . the longest one lasted was just 16 days . a 1984 report by the steinhart aquarium put it this way : `` in most cases it could be said that all these captive sharks were merely in the process of dying , with some taking longer than others . '' they had constructed an elaborate transport tank with a harness and iv fluids , but still couldn ’ t keep the sharks alive . it wasn ’ t until 2004 that the monterey bay aquarium proved that it was possible to keep white sharks for at least six months . it took a massive effort , and no one ’ s done it since . jon hoech : our approach was one of sort of a systematic , logical sequence of things leading up to our success and it started with designing a tank . the monterey bay aquarium had a million gallon , egg-shaped tank , 35 feet deep , designed for open-ocean animals like tuna and sharks . so you need a big tank . you also need a small shark . adult great whites reach 15 feet on average . the monterey bay aquarium nabbed one in 2004 that was 4 feet , 4 inches , less than a year old . that made it easier to move and easier to keep . jon hoech : when they ’ re young they feed on fish . and as they get older they transition to feeding more on mammals . and so we were targeting the age bracket where we knew we were more able to feed their natural diet . and once they collected the shark , they didn ’ t take it straight to the aquarium . instead , the monterey bay team set up a 4 million gallon pen right there in the ocean . that way they could monitor the shark and see if it would feed before they moved it into a transport tank to travel from southern california where the sharks were born up to the aquarium . sharks , like all fish , need to have water continually passing through their gills in order to get oxygen . most species can open and close their mouths to pump the water through . but white sharks and a couple dozen other species don ’ t do that . to breathe , they have to move forward through the water with their mouths open . that ’ s why white sharks start to weaken as soon as they ’ re caught in a net . and that ’ s why they needed a custom built transport tank with mobile life support . jon hoech : everything from oxygen sensors and video cameras and lighting and filtration systems that were needed for what turned out to roughly be 9 to 11 hour transport time . aquarium attendance jumped 30 percent while the shark was on display . after 6 and a half months , they decided to release it because it had killed 2 other sharks . over the next 6 years , the aquarium displayed 5 more baby white sharks - some they paid fishermen to hand over , some they caught themselves . their stays ranged from just 11 days up to 5 months . the monterey bay aquarium had succeeded in doing what no one else could . but it did take a toll on the sharks . they developed visible sores from bumping into the sides of the tank . sean van sommeran : we actually snuck in with photographers and took pictures of the sharks as they were beginning to attrit and fail due to the constant scraping against the walls basically . as we viewed it , it was a vase of flowers that would be kept for the visitors . historically , aquariums kept sharks that lived near the seabed or near reefs . that makes sense - it ’ s easier to recreate those habitats in a tank . but in recent decades , aquariums have wanted to bring in bigger , more pelagic sharks , those that spend time roaming the open ocean . they ’ ve even been able to exhibit the largest shark in the world , the whale shark , if they have a big enough tank . but pelagic sharks are used to being able to swim long distances without obstructions , changing directions only as they please . so the faster-moving sharks like the white shark , mako shark , and blue shark , they have trouble with walls when they ’ re put in a tank . that ’ s what was happening with the monterey bay aquarium ’ s sixth white shark in 2011 . they decided to release it after 55 days and its tracking tag revealed that the shark died shortly after being released . they ’ re not sure why . but since then , they haven ’ t tried bring in another great white shark . jon hoech : it ’ s just a very very very resource intensive program and we felt like we had accomplished our goal of introducing the general public to a live white shark . it took a huge , carefully planned system to keep a white shark alive . and even then , the sharks didn ’ t quite fit there . we can ’ t seem to stop trying though . earlier this year , an 11.5-foot great white shark was taken to an aquarium in okinawa , japan after getting caught in a fisherman 's net . it was the only adult white shark ever to be put on display , and within 3 days it was dead . i wanted show you a great resource online called the biodiversity heritage library - it ’ s the product of a couple dozen museums and libraries all agreeing to scan millions of pages from books related to biodiversity . they ’ ve got a bunch of great albums on flickr , including one that 's all about sharks . some of these go back to the 16th and 17th centuries , back when the naturalists used to call sharks “ sea dogs ” which is funny because as we now know sharks were roaming the oceans for about 300 million years before the first mammals showed up .
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as we viewed it , it was a vase of flowers that would be kept for the visitors . historically , aquariums kept sharks that lived near the seabed or near reefs . that makes sense - it ’ s easier to recreate those habitats in a tank .
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why do aquariums usually keep sharks that live near reefs ?
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