字幕表 動画を再生する 英語字幕をプリント We get asked a lot of questions here at SciShow. Sometime we get a question that has maybe never been asked before in the history of questions, and sometimes we get questions that are so universally wondered, that they get asked over and over again. So, we've compiled some of those frequent asks into one place, here, so hopefully, if you've ever wondered these curious questions, you can get a whole bunch of answers right now. Recently, Patreon patron, Rob Margolis, reminded us of two of these questions that come up a lot. The first, I hope you're not wondering right now, but if you are, I hope you recover quickly and can watch this video about what causes migraines. If you've never had a migraine, you might think it's just a really bad headache. But if you've ever had them, or you know someone who does, you know that they're much worse -- and much more complicated -- than that. A true migraine is a multi-symptom disorder of the central nervous system that affects the brain. But, yes, really bad headaches are a major component of it -- probably the single most significant and identifiable component. But it usually lasts longer than a normal headache -- anywhere from 4 hours to several days// -- and brings a whole array of other symptoms with it. Most migraine sufferers experience extreme sensitivity to light and sound, and sometimes smells. They also commonly experience nausea, vomiting, even fainting. What little relief they can find is generally only achieved by being very still in a dark, silent room until the symptoms pass. And believe it or not, it gets worse. Migraines also cause problems both before and after the headache. It's different for everyone, but the ordeal can start with symptoms as seemingly minor as constipation, weird food cravings, neck stiffness, or excessive yawning. As the symptoms worsen, people generally enter a phase called aura, in which they may experience things like vision disturbances -- like seeing shapes or lights, blurred or doubled vision, or even loss of vision -- “pins and needles” sensations in the extremities, weakness, and sometimes even slurred speech. Now, you might notice that these sound a lot like the symptoms of a stroke, and in fact migraines have so many things in common with strokes that doctors sometimes have to do tests to determine which disorder they're dealing with. After the headache has passed, most migraine sufferers experience a period of weakness and fatigue that can last from a few hours to a few days. Obviously this isn't the sort of thing that anyone wants to experience. So what causes it? Can it be controlled? Or at least treated? Doctors think migraines are probably caused by a sharp drop in your brain's levels of serotonin -- a neurotransmitter that plays a key role in regulating things like sleep and mood. And once that imbalance strikes, it causes a whole cascade of effects. But what triggers this imbalance is complicated and uncertain. We do know that one of the most important factors is genetics. If one or both of your parents has experienced a migraine, odds are that you will too. For reasons that we don't understand, women are far more likely to have migraines than men, and they're even more likely to experience one during times of hormonal changes, like puberty, menstruation, ovulation, pregnancy, when using hormonal contraceptives or hormone replacements, and menopause. Beyond that, everyone's triggers are different. For many people, it may depend on stress, their activity level or their sleep schedule -- all things in which serotonin plays a role. And still others may be triggered by things as seemingly random as bright lights, loud sounds, unusual or strong smells, or even weather changes. The //treatment// of migraines is further evidence that it's not just a headache. It's true that the headache itself can sometimes be treated with pain relievers, although they're often less effective. In addition to pain relief, migraine sufferers may take medications that try to treat the source of attacks, like by controlling the constriction of blood vessels in the brain, blood pressure, serotonin levels, and inflammation. So clearly a migraine is more than just a bad headache, remember that when you hang out with people who get them. If they're in a bad way, the biggest favor you can give them is just to let them be by themselves in a dark room. You can just keep watching SciShow //quietly//. Rob's second question is another that comes up a lot, but is less painful...for humans anyway. Welcome to I Don't Think It Means What You Think It Means, where we look at bits of scientific theory that've wiggled their way into popular culture and taken on a life of their own. Today we're talking about Schrodinger's Cat, a famous thought experiment devised by Austrian physicist Erwin Schrodinger, who helped piece physics back together after Einstein and his crew blew a giant honkin' hole in it back in the early 20th century. It can't really be overstated how much of a giant crap circus the 1920's were for physicists. Until then, everything had pretty much just been good old-fashioned Newtonian physics -- where you could observe objects moving, and predict how they'd react to various forces. But then along came new research into subatomic particles that showed they didn't act predictably at all. In fact, sometimes stuff seemed to be two things at once. Like, an electron in a beam might act like a particle sometimes and like a wave at other times. And to make things even more -- [heaves tense sigh, sort of like hyperventilating]-- the more you try to observe and measure these particles, the less naturally they seem to behave. Sphincter-say-what, now? [js: Um, it's from Wayne's World and I think I'm trying to bring it back.] My friends, welcome to one of the biggest mind-flogs of quantum mechanics; it's called superposition -- the idea that a particle can exist in all of its theoretically possible states at the same time. So Schrodinger came up with this thought experiment to help folks understand it: Say you have a cat and you put it in a steel chamber for an hour with a vial of deadly gas, a Geiger counter, a hammer, and a tiny bit of something radioactive. OK just bear with me. Now say there's a 50/50 chance that one of the radioactive atoms is going to decay within that hour. If one of the atoms decays, the Geiger counter is going to trigger the hammer, shattering the vial of poisonous gas. Really, Schrodinger? This is not the best way to get people behind the idea of funding the sciences. So, there's a 50% chance at the end of the hour that the vial has been broken and the cat is dead, and an equally good chance that the vial hasn't broken and the cat's just kickin' it, wondering what's for supper. But, what's actually happening in the box? According to quantum mechanics, any one of those radioactive atoms would be in a superposition of being both decayed and not decayed at the same time. Because that's how quantum objects act. So then that decayed atom will have both killed and not killed the cat, right? Well that's the logical conclusion but the cat isn't a quantum object. The cat is a big normal thing that obeys old-fashioned Newtonian laws. So it, just like ever other cat in history is either alive or dead. Schrodingers point, at least one of them is that the object is subject to two separate sets of laws that can't be reconciled. In order to know whether the atom is decayed or not is to open the box as see if the cat is dead. But in quantum mechanics, the state of superposition can't be observed. So when the evil mad scientist finally opens the chamber, to observe, the superposition collapses once the outcome is ensured. Today, Schrodinger's Cat is talked about as some undead zombie cat or discussed at being dead and not dead, alive in the box. But Schrodingers point wasn't to prove you can make a cat both alive and dead but instead prove that the quantum world doesn't mesh well with the normal world. Alternatively the point the universe is pretty freakin' weird. There are other interpretations of quantum mechanics that resolve the paradox but none of them are easy to test. My favorite is of course the “Many Worlds” interpretation that states at the end of the experiment and at the end of the superposition, alternate universes are created. But in this case, one in which the cat is alive and one in which the cat is dead. And to be clear I don't like this interpretation because it's the most likely one, I like it because it's such a excellent plot device for science fiction novels. Dreaming is one of the weirdest thing we do. I mean, I don't want to diminish all the other strange crap our bodies are capable of, 'cause a lot of it is cracked out on so many levels. But dreams are a special kind of crazy. No matter how many dreams you have in your life, every once in a while you wake up like, “WHAT THE HELL WAS THAT?” But as with everything else, science is helping us understand why we dream, what our brains are up to when they do it, and why dreaming may be critically important to the functioning of our awake brains. Try to stay awake for this, 'cause it's really cool. People have been trying to understand dreams since--well, since there've been people. But the person we associate most with the science of dreaming is probably Sigmund Freud. In 1899 he wrote The Interpretation of Dreams, where he suggested that dreams were largely symbolic and allowed us to sort through the repressed wishes that piled up in our unconscious minds. And most of those wishes involve weird sex stuff. Freud was kinduva perv, if you must know. It wasn't until the 1950s, when scientists became able to read the electrical activity of the brain, that we began to understand what a dreaming brain was actually up to. Two researchers at the University of Chicago -- Eugene Aserinsky and Nathaniel Kleitman -- pioneered this research by hooking people up to the newly-invented EEG machine and monitoring their brain activity while they slept. What they thought they'd find was that a sleeping brain was a resting brain, but they discovered exactly the opposite. They found that brain activity fluctuates in a predictable pattern over a period of about 90 minutes. This cycle takes sleepers from an initial period of drifting off, gradually into a really deep sleep with slower brain activity, back into almost-waking. And this stage of sleep where the sleepers were aaaaalmost awake again was the most interesting: brain activity in this phase was almost identical to when people were awake. But even more weird, during this stage, the subjects became functionally paralyzed--the only parts of their bodies that moved were their eyes, which darted back and forth under their eyelids. So Aserinsky and Kleitman called this period R.E.M. sleep, after the rapid eye movement that characterized it. They also called it “paradoxical sleep,” because the subjects seemed to be awake, according to their brain activity, even though they were basically dead to the world. I guess they figured these names were better than “Sexually Aroused Sleep,” which is another rather common feature of this stage. But another thing the scientists found was that if REM sleepers were awakened, they reported having really vivid dreams that were often emotionally intense. It wasn't the only stage of sleep in which the subjects dreamed, but it was the time they reported having the most lifelike dreams. It turns out that every 90 minutes or so, during the final stage of the sleep cycle, the brain phases into the R.E.M. sleep and our brains start creating crazy narratives that last maybe 20 or 30 minutes. This is when you have those really vibrant dreams that can easily be confused with reality. So WHYYYYY so busy, Sleeping Brain? And what's so important about dreaming that you have to paralyze your entire body in order to have really realistic dreams? Well, there are probably several answers, but one of them is that during all periods of dreaming, our brains are making important connections between real-life experiences that will help us in our waking lives. These days, researchers are finding that Freud was wrong about dreams in one important way: We don't dream much about our hidden desires. We mostly dream about what we did today. While we sleep, our brains are sorting through what happened while we were awake, deciding which new experiences were important enough to remember and which should get tossed, searching for links between seemingly unrelated events that might be able to help us be a more successful human tomorrow. And it's actually really important that we do this while we're asleep, because our conscious, waking brains are generally too controlling to allow this kind of creative problem-solving. And this dream-time activity helps our waking brains be better at things that require making connections and thinking outside the box. Dreams have actually been responsible for some really important inventions and discoveries in history. For instance, Dimitri Mendeleev came up with a system for the structure of the periodic table of elements in a dream after months of grueling conscious thought was getting him nowhere. And research shows that our brains are much better at solving puzzles if they're allowed to take a nap in the middle of doing one. In a study in 2004, for instance, subjects were asked to search for links between two sets of numbers. The subjects who napped solved the puzzle about 60% of the time, whereas only 25% non-nappers were able to do it. In another study, where people were asked to find connections between seemingly unrelated words, those who lapsed into R.E.M. sleep between sessions solved 40% more puzzles than those who didn't. So dreams are all about making associations and finding patterns that our waking brains have a hard time detecting. But it seems to work in slightly different ways in non-REM sleep than in REM sleep. During non-R.E.M. sleep, you dream, but the dreams aren't necessarily vivid, and they're often about something you've been doing or thinking about a lot. During these stages, people often report dreaming about kind of boring stuff -- like if you spent a lot of time in the car during the day, that night you might dream about driving down a long street, stopping at a series of stop lights. This might seem lame, but it's actually useful to the brain in its own way: it's telling itself things it already knows--like “when you're driving a car, you're supposed to stop at the stop lights.” So in non-REM sleep, it's basically reinforcing existing connections. But in REM sleep, we get to test out that reinforced knowledge in a context that is virtually indistinguishable from real life. It's like our brain running simulations. So if you've been driving to your grandparents' house in Boca Raton all day, and in non-REM sleep you spend a good 20 minutes practicing stopping at traffic lights, during REM sleep your brain might have you trying to steer a steamroller through Manhattan from the backseat. REM dreams can be very lifelike and very stressful, but that's part of it: A vivid REM dream is an opportunity to safely let us try something difficult. Because our brains aren't here to make friends. Our brains are here to win.