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.
The evolutionary purpose of dreaming--like the evolutionary purpose of virtually everything
else we do--is to make us more successful animals tomorrow than we were yesterday.
So if during non-REM sleep, the brain is taking data from past experience and fiddling with
it to figure out how that might relate to the future, in REM sleep, the brain’s actually
trying to experience the future in order to test possibilities.
So, maybe you’re making out with your algebra teacher on Jay-Z’s yacht while wearing a
banana suit.
What of it?
Does it mean you subconsciously want to make out with your teacher?
Maybe, but not necessarily.
Does the banana suit have something to do with penises?
I dunno - -who am I, Freud?
The thing is, during REM sleep you can try that experience out with no consequences whatsoever.
Another benefit of REM sleep is that it helps us process emotions that our dunderheaded
waking brains aren’t really equipped to handle.
Although the content of our dreams might be wacky, the emotions attached to them are absolutely
real.
Remember, your dreaming brain is charged with working on real-life problems, so if you feel
really angry at your boyfriend in your dream, chances are you’re probably pretty pissed
at him--or maybe someone else you’re close to--in real life.
The stories our dreams create are essentially attempts to give our emotions a narrative
that can kind of suck the poison out of them and give them a form our brain can deal with
better.
In fact, people who can’t experience REM sleep often experience other psychiatric disorders.
So, dreams help regulate traffic between our experiences, our emotions and our memories,
so we can dial down the crazy.
And hey--if the outcome makes your rational brain uncomfortable, well....
That’s just how sausage is made, folks.
Since I’m on the topic of weird dreams and REM sleep, a lot of you have said you’d
like to know more about what’s called lucid dreaming.
This is when you become aware of the fact that you’re dreaming and can actually direct
the narrative of the dream.
Since REM sleep is simulation time in the brain, lucid dreaming is basically a simulation
that lets a portion of your conscious brain in on the action.
Most of us can probably recall at least one lucid dream, and about 1 in 10 of us have
them regularly.
Some lucid dreamers can even communicate with researchers studying them through gestures
like eye movements and hand-squeezes.
What ultimately separates lucid dreams from regular old REM sleep may lie in the physiology
of the brain.
During non-REM sleep, the cerebral cortex -- that’s your gray matter -- loses its
ability to associate with other parts of the brain.
This is probably why those dreams are more boring and less complex.
But once a dreamer reaches REM sleep, the cortex becomes active again and begins talking
to other areas of the brain -- except for this one little part of the cortex--called
the dorsolateral prefrontal cortex -- that doesn’t reactivate.
This is the region right about at your left temple that’s responsible for, among other
things, applying memories to other situations, like planning stuff and predicting outcomes.
This helps explain why REM sleep dreams are so weird -- your brain literally can’t tell
what’s going to happen next.
But during lucid dreaming, the dorsolateral prefrontal cortex actually does wake up, which
is probably why we regain a sense of self-awareness and can plot out stories for ourselves.
Some people claim lucid dreaming can help cure reccurring nightmares or even help cure
depression and anxiety.
The jury’s still out on that, but dreaming itself--all kinds of dreaming--is definitely
useful, and even imperative, to the function of the brain.
So, why are you still awake?
Go take a nap or something!
First thing you should know if you’re having a hard time getting some shuteye, is that
you’re wired to sleep regular hours...going to bed the same time each night and waking
up at the same time each morning.
Having a regular wake-up time seems to correlate pretty highly with the ability to fall asleep
consistently.
This is because it keeps you aligned with what’s known as your circadian rhythm, your
body’s natural tendency to stay in sync with the cycles of day and night.
And you know what controls your body’s circadian rhythm more than anything?
Light.
A lot of the help you get falling asleep comes from hormones -- they lower your heart rate
and reduce your blood pressure and basically let you relax.
The key player here is the hormone melatonin, and it’s regulated by your exposure to light.
In darkness, it flows freely.
But when you’re exposed to light -- whether natural or artificial -- the release of melatonin
stops.
So you know what that means?
No phones or laptops in bed!
The light emitted by electronics simulates sunlight, and confuses your body into not
knowing that it’s time to sleep.
So scientists suggest at least an hour of screen-free time before bed...though I am
completely incapable of that myself.
Another obvious enemy of sleep: caffeine [pic].
Even though you might think that cup of coffee after dinner might only affect you for an
hour or so, studies have shown that caffeine consumption as much as TWELVE HOURS before
bedtime is linked with insomnia.
And even the way you //think// about sleep can affect your sleep patterns.
Worrying about not getting enough sleep is a common enough cause of insomnia that it
has its own name, Sleep Onset Insomnia.
But you know what’s weird?
A lot of the time, when we feel like we can’t sleep -- we actually ARE sleeping.
When scientists rouse patients in the first or second stages of sleep, more than 60% of
them say that they weren’t sleeping, even though they were.
Now, of course, there’s a whole class of medications that will help you sleep, from
antihistamines to the pharmaceuticals known as hypnotics, which include Ambien and Lunesta.
However, research has shown that while patients [pic] //can// fall asleep faster on hypnotics,
the effect is small, adding only about 15 minutes to their sleep times.
Other studies indicate that //our minds// are significantly more powerful than any medications.
In double-blind studies, patients who were simply //told// that they were taking a sleep
drug ended up sleeping far better than patients who were told they weren’t.
So, if you want to know how to sleep, the answer is right there in your head.
As part of our work answering the world’s most asked questions, we asked you, our scishow
viewers, some questions...and one was how many hours per night you sleep.
Bad news: Only 10% of you are sleeping more than eight hours per night, and eight and
a half is the doctor-recommended amount.
And OVER HALF of you report having trouble getting to sleep at least once per week.
Oh but wait...we haven’t gotten to the fun part...MEANINGLESS CORRELATIONS!!!
The best sleepers for countries where we had enough data to make a judgement were Saudi
Arabians, with 76 percent reporting that they experience insomnia infrequently or never.
Most of Europe scored better than average, with The Netherlands, Russia, and Spain all
sleeping relatively soundly.
The English speakers in the US, UK, and Australia all had some of the worst scores.
And, finally, unsurprisingly, our staggeringly unscientific survey reports that people who
commonly drink coffee, soda, energy drinks or tea are all more likely to suffer from
insomnia.
Though maybe they’re just drinking those things because they’re so tired!
So now that you know all about migraines, hypothetical cats, and sleep, on to the serious
questions!
Why?
WHY do we have baby teeth?
Missing teeth… not so cute on the lead singer of the Pogues, but pretty dang cute on a smiling
toddler.
But why do humans have baby teeth, and why do we lose them?
Humans, like most mammals, are diphyodonts [dye-FYE-oh-donts], meaning we grow two sets
of teeth in our lifetimes -- a permanent set of adult teeth, and a deciduous set of baby
teeth.
Deciduous teeth are smaller and fewer in number, because a toddler’s jaws are tiny and could
never fit a full set of 32 adult teeth.
Poor kids would look like something out of a horror movie.
So, instead, we begin life with 20 smaller teeth, which start erupting out of our gums
when we’re about six months old and are fully in by the time we’re two and a half.
Just like our permanent teeth, deciduous teeth grow in pairs.
Meaning that when two incisors erupt from the lower jaw, you can bet that two incisors
will soon erupt from the upper jaw.
This allows our mouths to bite down and chew evenly, and helps ensure that our jaws grow
and wear down evenly, too.
Now, as we get bigger, we need more teeth.
But instead of wedging these new teeth in between the old ones, we lose the old teeth
and grow a whole new set.
That’s why baby teeth are called deciduous -- just like the leaves on deciduous trees,
they’ll shed at a specific stage of development.
Four new molars erupt in the back of our mouths when we’re around five or six years old.
Then our deciduous incisors -- which are right here [points to teeth in front of mouth] fall
out and are replaced with permanent incisors.
By the time we reach puberty, we have an almost-full set of 28 permanent teeth.
The last four emerge later in life.
These are the so-called “wisdom teeth,” molars in the back of our mouths.
They were a good idea some 100 million years ago when our jaws were bigger.
But evolution has made our mouths smaller, and now these molars crowd out other teeth
and can cause pain, which is why a lot of us get them pulled.
And being a diphyodont is actually kind of a disadvantage in other ways, too.
While it sounds nice to have an extra set of something, we only get two sets of teeth
in our lives.
Polyphyodonts [pol-ee-fye-o-donts], on the other hand, can grow and regenerate teeth
multiple times.
These include alligators, fish and even some mammals, like elephants, who can regenerate
their teeth up to six times, to help them enjoy long lives of grinding up plants.
But /our/ second set of teeth will just keep wearing and breaking over time, so take care
of them while you can, because they’re the only ones you’ll get!
Our final FAQ that we’ll share with you today is one I’m pretty sure everyone has
wondered about whenever you’ve really stopped and thought about your eyebrows.
Or arm hair.
Or any hair.
You’re probably quite happy that your armpit hair isn’t dragging on the floor.
So it’s good that there’s a system to prevent that.
But what is that system?
Us humans grow hair all over our bodies -- except on our palms and the soles of our feet.
But some of it, like leg hair, stops growing, while the hair on our heads just seems to
grow out forever.
That’s because every hair on your body goes through the same cycle -- growing for a while
and then falling out -- but each /type/ of hair spends a different amount of time growing,
and grows at a different speed.
Every hair begins the same way, in a phase of the cycle called anagen.
During anagen, blood flow starts to ramp up at the base of the follicle, feeding oxygen
to specialized stem cells.
These cells begin rapidly dividing and producing keratinocytes [ker-AT-in-oh-sites], which
form the root of the hair.
As the expanding mass of keratinocytes is pushed toward the surface of the skin, the
cells die, releasing a protein called keratin [CARE-a-tin], which holds the strand of hair
together.
Eventually that strand pops out of your skin.
So the visible part of the hair is entirely dead, which is why, thankfully, it doesn’t
hurt to get your hair cut -- though try explaining that to a three-year-old.
During anagen, hair can grow up to 1 and a quarter centimeters every month, depending
on where it’s located on your body.
The second phase is called catagen [CAT-a-jen], and lasts about two weeks.
Here, the blood supply is cut off at the bottom of the follicle, which stops the production
of new keratinocytes.
So for that particular hair, the party is over.
The follicle then shrinks to about a sixth of its original size, and the existing hair
strand is pushed closer the surface.
The third phase is called telogen [TELL-o-jen], otherwise known as the resting phase, where
the follicle remains dormant for one to four months.
Finally, the hair is released, or shed, when the follicle dilates, and starts the anagen
phase again.
So, how long a hair on your body gets, depends on how long it’s in the anagen phase, and
how /fast/ it grows during that time.
The hair on your scalp, for example, stays in anagen for two to six years, which is why
it can grow so long.
Other hair types, like eyebrows and eyelashes and body hair have a short anagen phase -- only
30 to 45 days.
But they also grow much more slowly, with eyebrows, for instance, growing only 4.2 millimeters
every month.
This is my eyebrow closeup.
Hey...
As for how your hairs know when to grow and when to stop, that’s something scientists
are still trying to figure out.
It’s known that genetics can lead to longer or shorter anagen phases in certain hair types.
But the current thinking is that your hairs get their instructions -- by way of chemical
growth signals -- from stem cells in the skin.
And considering how extremely inconvenient it would be for all of the hairs on your body
and all mammals’ bodies to just continue growing forever, it makes sense that there’s
a system for making sure they don’t grow too long.
Thanks for watching this Frequently Asked Compilation video.
Please keep asking us questions!
You can ask in the comments, on Patreon, Tumblr, Facebook, Snapchat, email, via pigeon--if
you can figure that out, we’ll have questions for you too!
And in the meantime, keep getting smarter with us by going to youtube.com/scishow to
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