[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.00,0:00:08.54,Default,,0000,0000,0000,,Some of the issues that are important
Dialogue: 0,0:00:08.54,0:00:10.48,Default,,0000,0000,0000,,if you want to have people in space
Dialogue: 0,0:00:10.48,0:00:12.03,Default,,0000,0000,0000,,for long periods of time.
Dialogue: 0,0:00:12.03,0:00:14.07,Default,,0000,0000,0000,,One is that people will tend to lose
Dialogue: 0,0:00:14.07,0:00:15.57,Default,,0000,0000,0000,,bone and muscle mass.
Dialogue: 0,0:00:15.57,0:00:16.53,Default,,0000,0000,0000,,We know this.
Dialogue: 0,0:00:16.53,0:00:18.48,Default,,0000,0000,0000,,If you have to put a cast on your leg,
Dialogue: 0,0:00:18.48,0:00:20.48,Default,,0000,0000,0000,,and you take the cast off after a few weeks,
Dialogue: 0,0:00:20.48,0:00:23.61,Default,,0000,0000,0000,,you'll see that your muscles have shrunk in size.
Dialogue: 0,0:00:23.61,0:00:25.91,Default,,0000,0000,0000,,And if you measured the bone strength,
Dialogue: 0,0:00:25.91,0:00:28.81,Default,,0000,0000,0000,,you'd also see that might have gone down a little bit, too.
Dialogue: 0,0:00:28.81,0:00:32.09,Default,,0000,0000,0000,,And so, it's very interesting that our body has that ability
Dialogue: 0,0:00:32.09,0:00:34.40,Default,,0000,0000,0000,,to adapt to the loads that are put on it,
Dialogue: 0,0:00:34.40,0:00:36.47,Default,,0000,0000,0000,,so that bones and muscles aren't static,
Dialogue: 0,0:00:36.47,0:00:37.94,Default,,0000,0000,0000,,they're always changing.
Dialogue: 0,0:00:37.94,0:00:40.21,Default,,0000,0000,0000,,While we think of bone as being a solid thing
Dialogue: 0,0:00:40.21,0:00:41.88,Default,,0000,0000,0000,,that doesn't change very much,
Dialogue: 0,0:00:41.88,0:00:43.36,Default,,0000,0000,0000,,it changes too.
Dialogue: 0,0:00:43.36,0:00:45.62,Default,,0000,0000,0000,,And it turns out that in weightlessness,
Dialogue: 0,0:00:45.62,0:00:46.98,Default,,0000,0000,0000,,you lose bone.
Dialogue: 0,0:00:46.98,0:00:49.17,Default,,0000,0000,0000,,And then you also cause the muscles
Dialogue: 0,0:00:49.17,0:00:51.49,Default,,0000,0000,0000,,that work against gravity,
Dialogue: 0,0:00:51.49,0:00:53.21,Default,,0000,0000,0000,,what are called the postural muscles,
Dialogue: 0,0:00:53.21,0:00:56.29,Default,,0000,0000,0000,,they'll start to shrink and lose strength.
Dialogue: 0,0:00:56.29,0:00:58.19,Default,,0000,0000,0000,,There are other things in the cardiovascular system,
Dialogue: 0,0:00:58.19,0:00:59.79,Default,,0000,0000,0000,,the heart and blood vessels.
Dialogue: 0,0:00:59.79,0:01:01.13,Default,,0000,0000,0000,,And if you think about it,
Dialogue: 0,0:01:01.13,0:01:03.62,Default,,0000,0000,0000,,standing up in gravity
Dialogue: 0,0:01:03.62,0:01:05.79,Default,,0000,0000,0000,,means you have to work against gravity
Dialogue: 0,0:01:05.79,0:01:08.16,Default,,0000,0000,0000,,in order to keep blood pumping to your head.
Dialogue: 0,0:01:08.16,0:01:11.18,Default,,0000,0000,0000,,So, if you couldn't keep blood pumping in the head,
Dialogue: 0,0:01:11.18,0:01:13.54,Default,,0000,0000,0000,,you'd pass out every time you stood up
Dialogue: 0,0:01:13.54,0:01:15.28,Default,,0000,0000,0000,,because when you're lying down,
Dialogue: 0,0:01:15.28,0:01:17.15,Default,,0000,0000,0000,,you don't have to push against gravity.
Dialogue: 0,0:01:17.15,0:01:18.36,Default,,0000,0000,0000,,But when you stand up,
Dialogue: 0,0:01:18.36,0:01:19.74,Default,,0000,0000,0000,,you got to work against gravity
Dialogue: 0,0:01:19.74,0:01:21.40,Default,,0000,0000,0000,,to keep blood flowing to your head.
Dialogue: 0,0:01:21.40,0:01:22.57,Default,,0000,0000,0000,,And your heart and blood vessels
Dialogue: 0,0:01:22.57,0:01:24.54,Default,,0000,0000,0000,,have a really nicely worked-out system
Dialogue: 0,0:01:24.54,0:01:27.22,Default,,0000,0000,0000,,to make that happen every time.
Dialogue: 0,0:01:28.72,0:01:32.24,Default,,0000,0000,0000,,But that system can also change in weightlessness.
Dialogue: 0,0:01:32.24,0:01:34.21,Default,,0000,0000,0000,,And then the other area that changes
Dialogue: 0,0:01:34.21,0:01:36.49,Default,,0000,0000,0000,,is the system that has to do with balance.
Dialogue: 0,0:01:36.49,0:01:38.49,Default,,0000,0000,0000,,Again, maintaining your balance
Dialogue: 0,0:01:38.49,0:01:41.38,Default,,0000,0000,0000,,is something that you're doing against gravity, right?
Dialogue: 0,0:01:41.38,0:01:43.46,Default,,0000,0000,0000,,If you didn't have gravity present,
Dialogue: 0,0:01:43.46,0:01:45.95,Default,,0000,0000,0000,,you wouldn't have to worry about falling.
Dialogue: 0,0:01:45.95,0:01:48.24,Default,,0000,0000,0000,,But you obviously do have to worry about falling,
Dialogue: 0,0:01:48.24,0:01:50.90,Default,,0000,0000,0000,,and we have a very highly developed sense of balance
Dialogue: 0,0:01:50.90,0:01:52.47,Default,,0000,0000,0000,,to keep us upright
Dialogue: 0,0:01:52.47,0:01:53.84,Default,,0000,0000,0000,,and to prevent us from falling.
Dialogue: 0,0:01:53.84,0:01:55.89,Default,,0000,0000,0000,,And when you see what skaters do,
Dialogue: 0,0:01:55.89,0:01:59.26,Default,,0000,0000,0000,,you realize just how exquisite a system it is.
Dialogue: 0,0:01:59.26,0:02:00.76,Default,,0000,0000,0000,,But when you go into weightlessness,
Dialogue: 0,0:02:00.76,0:02:02.59,Default,,0000,0000,0000,,your balance system changes.
Dialogue: 0,0:02:02.59,0:02:03.99,Default,,0000,0000,0000,,You don't really notice it
Dialogue: 0,0:02:03.99,0:02:05.02,Default,,0000,0000,0000,,while you are in weightlessness,
Dialogue: 0,0:02:05.02,0:02:06.94,Default,,0000,0000,0000,,but when you come back,
Dialogue: 0,0:02:06.94,0:02:08.02,Default,,0000,0000,0000,,you do notice it,
Dialogue: 0,0:02:08.02,0:02:08.94,Default,,0000,0000,0000,,that your balance has changed
Dialogue: 0,0:02:08.94,0:02:10.36,Default,,0000,0000,0000,,and you have a little bit of trouble
Dialogue: 0,0:02:10.36,0:02:11.82,Default,,0000,0000,0000,,maintaining your balance.
Dialogue: 0,0:02:11.82,0:02:14.90,Default,,0000,0000,0000,,And what it shows is that while you're in space,
Dialogue: 0,0:02:14.90,0:02:17.63,Default,,0000,0000,0000,,your brain is trying to allow you
Dialogue: 0,0:02:17.63,0:02:19.66,Default,,0000,0000,0000,,to function in weightlessness.
Dialogue: 0,0:02:19.66,0:02:22.15,Default,,0000,0000,0000,,And so, it re-adapts you to be weightless,
Dialogue: 0,0:02:22.15,0:02:24.22,Default,,0000,0000,0000,,which you don't notice until you come back
Dialogue: 0,0:02:24.22,0:02:26.74,Default,,0000,0000,0000,,and find out that you're now back on Earth
Dialogue: 0,0:02:26.74,0:02:29.80,Default,,0000,0000,0000,,with a balance system that's been adapted to space.
Dialogue: 0,0:02:29.80,0:02:33.44,Default,,0000,0000,0000,,You know, all life developed here on Earth
Dialogue: 0,0:02:33.44,0:02:35.43,Default,,0000,0000,0000,,with gravity being present,
Dialogue: 0,0:02:35.43,0:02:39.22,Default,,0000,0000,0000,,so life evolved under the influence of gravity,
Dialogue: 0,0:02:39.22,0:02:41.95,Default,,0000,0000,0000,,and then we grow up with gravity being present,
Dialogue: 0,0:02:41.95,0:02:43.82,Default,,0000,0000,0000,,so we learn how to walk
Dialogue: 0,0:02:43.82,0:02:44.85,Default,,0000,0000,0000,,and catch a ball
Dialogue: 0,0:02:44.85,0:02:46.44,Default,,0000,0000,0000,,and ice skate
Dialogue: 0,0:02:46.44,0:02:47.12,Default,,0000,0000,0000,,or whatever,
Dialogue: 0,0:02:47.12,0:02:49.50,Default,,0000,0000,0000,,all with gravity being present.
Dialogue: 0,0:02:49.50,0:02:53.79,Default,,0000,0000,0000,,And what if you were to grow up without gravity?
Dialogue: 0,0:02:53.79,0:02:57.03,Default,,0000,0000,0000,,What about the systems that depend on gravity,
Dialogue: 0,0:02:57.03,0:02:58.83,Default,,0000,0000,0000,,like your muscles
Dialogue: 0,0:02:58.83,0:03:00.80,Default,,0000,0000,0000,,or your balance system
Dialogue: 0,0:03:00.80,0:03:03.58,Default,,0000,0000,0000,,or the heart and blood vessels?
Dialogue: 0,0:03:03.58,0:03:05.33,Default,,0000,0000,0000,,Would they develop normally,
Dialogue: 0,0:03:05.33,0:03:07.93,Default,,0000,0000,0000,,or would they be different in some way?
Dialogue: 0,0:03:07.93,0:03:08.96,Default,,0000,0000,0000,,One reason why you might think
Dialogue: 0,0:03:08.96,0:03:11.58,Default,,0000,0000,0000,,that it would go down a different pathway
Dialogue: 0,0:03:11.58,0:03:12.92,Default,,0000,0000,0000,,is from an experiment
Dialogue: 0,0:03:12.92,0:03:14.61,Default,,0000,0000,0000,,that was done some time ago
Dialogue: 0,0:03:14.61,0:03:16.59,Default,,0000,0000,0000,,by two neuroscientists
Dialogue: 0,0:03:16.59,0:03:18.36,Default,,0000,0000,0000,,called Hubel and Wiesel.
Dialogue: 0,0:03:18.36,0:03:21.67,Default,,0000,0000,0000,,And what they did is they had a kitten,
Dialogue: 0,0:03:21.67,0:03:24.55,Default,,0000,0000,0000,,and they put a patch over the eye of the kitten.
Dialogue: 0,0:03:24.55,0:03:27.20,Default,,0000,0000,0000,,And then the kitten grew up to be a cat,
Dialogue: 0,0:03:27.20,0:03:29.68,Default,,0000,0000,0000,,and they removed the patch.
Dialogue: 0,0:03:29.68,0:03:31.96,Default,,0000,0000,0000,,And so, the question is,
Dialogue: 0,0:03:31.96,0:03:34.92,Default,,0000,0000,0000,,can the cat see out of that eye?
Dialogue: 0,0:03:34.92,0:03:37.24,Default,,0000,0000,0000,,Now, there's nothing wrong with the eye, right?
Dialogue: 0,0:03:37.24,0:03:39.21,Default,,0000,0000,0000,,But it just hasn't seen anything,
Dialogue: 0,0:03:39.21,0:03:41.65,Default,,0000,0000,0000,,there hasn't been any light coming in.
Dialogue: 0,0:03:41.65,0:03:45.51,Default,,0000,0000,0000,,And the answer is that the cat can't see out of that eye
Dialogue: 0,0:03:45.51,0:03:48.53,Default,,0000,0000,0000,,because what happens is that the brain
Dialogue: 0,0:03:48.53,0:03:51.47,Default,,0000,0000,0000,,goes down a different pathway when it develops
Dialogue: 0,0:03:51.47,0:03:53.99,Default,,0000,0000,0000,,and the connections that would ordinarily develop
Dialogue: 0,0:03:53.99,0:03:56.36,Default,,0000,0000,0000,,to that eye don't develop.
Dialogue: 0,0:03:56.36,0:03:58.57,Default,,0000,0000,0000,,And that can't be undone,
Dialogue: 0,0:03:58.57,0:04:00.38,Default,,0000,0000,0000,,that's a permanent change.
Dialogue: 0,0:04:00.38,0:04:02.01,Default,,0000,0000,0000,,So, the brain of that cat
Dialogue: 0,0:04:02.01,0:04:05.31,Default,,0000,0000,0000,,is fundamentally different from the brain of a cat
Dialogue: 0,0:04:05.31,0:04:07.88,Default,,0000,0000,0000,,that grew up seeing out of that eye.
Dialogue: 0,0:04:07.88,0:04:10.97,Default,,0000,0000,0000,,That cat grew up with a different brain, in essence.
Dialogue: 0,0:04:10.97,0:04:11.84,Default,,0000,0000,0000,,So, then you wonder,
Dialogue: 0,0:04:11.84,0:04:13.62,Default,,0000,0000,0000,,well, what about gravity?
Dialogue: 0,0:04:13.62,0:04:15.44,Default,,0000,0000,0000,,What if you don't have the forces
Dialogue: 0,0:04:15.44,0:04:17.34,Default,,0000,0000,0000,,that gravity produces?
Dialogue: 0,0:04:17.34,0:04:19.73,Default,,0000,0000,0000,,Is your balance organ going to develop
Dialogue: 0,0:04:19.73,0:04:21.30,Default,,0000,0000,0000,,in the same way,
Dialogue: 0,0:04:21.30,0:04:22.87,Default,,0000,0000,0000,,or will it be different?
Dialogue: 0,0:04:22.87,0:04:24.54,Default,,0000,0000,0000,,If somebody grew up in space,
Dialogue: 0,0:04:24.54,0:04:27.45,Default,,0000,0000,0000,,could they come back to Earth and function,
Dialogue: 0,0:04:27.45,0:04:30.70,Default,,0000,0000,0000,,or would they really be a different person?