[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Some of the issues that are important
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,if you want to have people in space
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,for long periods of time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,One is that people will tend
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to lose bone and muscle mass.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,We know this.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,If you have to put a cast on your leg
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and you take the cast off after a few weeks,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you'll see that your muscles have shrunk in size.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And if you measured the bone strength,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you'd also see that might have gone down a little bit, too.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And so, it's very interesting that our body has that ability
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to adapt to the loads that are put on it,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,so that bones and muscles aren't static,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,they're always changing.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,While we think of bone as being this solid thing
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that doesn't change very much,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,it changes too.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And it turns out that in weightlessness,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you lose bone.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And then you also cause the muscles
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that work against gravity,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,what are called the postural muscles,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,they'll start to shrink and lose strength.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,There are other things in the cardiovascular system,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,the heart and blood vessels.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And if you think about it,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,standing up in gravity
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,means you have to work against gravity
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,in order to keep blood pumping to your head.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, if you couldn't keep blood pumping in your head,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you'd pass out every time you stood up
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,because when you're lying down,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you don't have to push against gravity.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,But when you stand up,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you got to work against gravity
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to keep blood flowing to your head.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And your heart and blood vessels
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,have a really nicely worked-out system
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to make that happen every time.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,But that system can also change in weightlessness.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And then the other area that changes
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is the system that has to do with balance.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Again, maintaining your balance
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is something that you're doing against gravity, right?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,If you didn't have gravity present,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you wouldn't have to worry about falling.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,But you obviously do have to worry about falling
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and we have a very highly developed sense of balance
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to keep us upright
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and to keep us from falling.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And when you see what skaters do,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you realize just how exquisite a system it is.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,But when you go into weightlessness,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,your balance system changes.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You don't really notice it
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,while you are in weightlessness,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,but when you come back,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,you do notice it,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that your balance has changed
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and you have a little bit of trouble
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,maintaining your balance.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And what it shows is that while you're in space,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,your brain is trying to allow you
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,to function in weightlessness.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So it re-adapts you to be weightless,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,which you don't notice until you come back
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and find out that you are now back on Earth
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,with a balance system that's been adapted to space.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,You know, all life developed here on Earth
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,with gravity being present,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,so life evolved under the influence of gravity,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and then we grow up with gravity being present,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,so we learn how to walk
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and catch a ball
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and ice skate
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or whatever,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,all with gravity being present.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And what if you were to grow up without gravity?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,What about the systems that depend on gravity,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,like your muscles
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or your balance system
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or the heart and blood vessels?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Would they develop normally,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or would they be different in some way?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,One reason why you might think
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,it would go down a different pathway
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is from an experiment
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that was done some time ago
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,by two neuroscientists
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,called Hubel and Wiesel.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And what they did, was they had a kitten
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and they put a patch over the eye of the kitten.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And then the kitten grew up to be a cat,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,and they removed the patch.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And so, the question is,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,can the cat see out of that eye?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Now, there's nothing wrong with the eye, right?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,But it just hasn't seen anything,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,there's no,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,it hasn't been any light coming in.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And the answer is that the cat can't see out of that eye
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,because what happens is that the brain
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,goes down a different pathway
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,when it develops and the connections
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that would ordinarily develop to that eye
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,don't develop.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,And that can't be undone,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that's a permanent change.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, the brain of that cat
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,is fundamentally different from the brain of a cat
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that grew up seeing out of that eye.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,That cat grew up with a different brain, in essence.
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,So, then you wonder
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,what about gravity?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,What if you don't have the forces
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,that gravity produces?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,Is your balance organ going to develop
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,in the same way,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or will it be different?
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,If somebody grew up in space,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,could they come back to Earth and function,
Dialogue: 0,9:59:59.99,9:59:59.99,Default,,0000,0000,0000,,or would they really be a different person?