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動画の字幕をクリックしてすぐ単語の意味を調べられます!
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Can you read in the car?
If so, consider yourself pretty lucky.
For about one-third of the population,
looking at a book while moving along in a car
or a boat
or train
or plane
quickly makes them sick to their stomach.
But why do we get motion sickness in the first place?
Well, believe it or not,
scientists aren't exactly sure.
The most common theory has to do
with mismatched sensory signals.
When you travel in a car,
your body is getting two very different messages.
Your eyes are seeing the inside of a vehicle,
which doesn't seem to be moving.
Meanwhile, your ear is telling your brain
that you're accelerating
Wait, your ear?
Yeah, your ear actually
has another important function besides hearing.
In its innermost part lies a group of structures
known as the vestibular system,
which gives us our sense of balance and movement.
Inside there are three semicircular tubules
that can sense rotation,
one for each dimension of space.
And there are also two hair-lined sacks
that are filled with fluid.
So when you move,
the fluid shifts and tickles the hairs,
telling your brain
whether you are moving horizontally
or vertically.
With all these combined,
your body can sense
which direction you're moving in,
how much you've accelerated,
and even at what angle.
So, when you are in the car,
your vestibular system correctly senses your movement,
but your eyes don't see it,
especially if they are glued to a book.
The opposite can happen, too.
Say you are sitting in a movie theater
and the camera makes a broad, sweeping move.
This time it's your eyes
that think you're moving
while your ear knows that you're sitting still.
But why does this conflicting information
have to make us feel so terrible?
Scientists aren't sure about that either,
but they think that there's an evolutionary explanation.
As you know, fast moving vehicle and video recordings
have only existed in the last couple of centuries,
barely a blink in evolutionary time.
For most of our history,
there just wasn't that much
that could cause this kind of sensory mix-up
except for poisons.
And because poisons
are not the best thing for survival,
our bodies evolved a very direct
but not very pleasant way
to get rid of whatever we might have eaten
that was causing the confusion.
This theory seems pretty reasonable,
but it leaves a lot of things unexplained
like why women are more affected
by motion sickness than men,
or why passengers get more nauseous
than drivers.
Another theory suggests
that the cause may have more to do
with the way some unfamiliar situations
make it harder to maintain
our natural body posture.
Studies have shown
that being immersed in water
or just changing your stance
can greatly reduce the effects
of motion sickness.
But, again, we don't really know what's going on.
We all do know some of the more common remedies
for car queasiness --
looking at the horizon,
chewing gum,
taking over-the-counter pills --
but none of these are totally reliable
nor can they handle
really intense motion sickness
and sometimes the stakes
are far higher than just not being bored
during a long car ride.
At NASA, where astronauts are hurled into space
at 17,000 miles per hour,
motion sickness is a serious problem.
So, in addition to researching
the latest space-age technologies,
NASA also spends a lot of time
trying to figure out
how to keep astronauts from vomiting up
their carefully prepared space rations.
Much like understanding the mysteries of sleep
or curing the common cold,
motion sickness remains one of those
seemingly simple problems that,
despite amazing scientific progress,
we still know very little about.
Perhaps one day the exact cause
of motion sickness will be found,
and with it,
a completely effective way to prevent it,
but that day is still on the horizon.
コツ:単語をクリックしてすぐ意味を調べられます!

読み込み中…

【TED-Ed】The mystery of motion sickness - Rose Eveleth

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Go Tutor 2014 年 2 月 25 日 に公開
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