[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.52,0:00:03.16,Default,,0000,0000,0000,,When you look at footage or\Nphotographs of astronauts
Dialogue: 0,0:00:03.16,0:00:06.98,Default,,0000,0000,0000,,in space, it doesn't look like\Nthere's any gravity at work
Dialogue: 0,0:00:06.98,0:00:07.51,Default,,0000,0000,0000,,here.
Dialogue: 0,0:00:07.51,0:00:10.08,Default,,0000,0000,0000,,Everything is not falling\Ndown in one direction.
Dialogue: 0,0:00:10.08,0:00:12.81,Default,,0000,0000,0000,,In fact, it's not even\Nclear what up or down is.
Dialogue: 0,0:00:12.81,0:00:14.39,Default,,0000,0000,0000,,Everything just floats around.
Dialogue: 0,0:00:14.39,0:00:15.90,Default,,0000,0000,0000,,If I were to push\Noff of this wall,
Dialogue: 0,0:00:15.90,0:00:17.92,Default,,0000,0000,0000,,I would just float\Nin that direction.
Dialogue: 0,0:00:17.92,0:00:22.25,Default,,0000,0000,0000,,So it doesn't look like there's\Nthis overarching influence
Dialogue: 0,0:00:22.25,0:00:26.55,Default,,0000,0000,0000,,like gravity that's trying\Nto pull everything down.
Dialogue: 0,0:00:26.55,0:00:29.76,Default,,0000,0000,0000,,But the question is that\Nthese astronauts are still
Dialogue: 0,0:00:29.76,0:00:32.88,Default,,0000,0000,0000,,not too far away from\Na supermassive body.
Dialogue: 0,0:00:32.88,0:00:36.19,Default,,0000,0000,0000,,In fact, the space shuttle\Ngets up only a couple
Dialogue: 0,0:00:36.19,0:00:38.83,Default,,0000,0000,0000,,of hundred miles above\Nthe surface of the Earth.
Dialogue: 0,0:00:38.83,0:00:41.00,Default,,0000,0000,0000,,So the space shuttle, if I\Nwere to draw it to scale,
Dialogue: 0,0:00:41.00,0:00:43.64,Default,,0000,0000,0000,,would probably be\Nright about there.
Dialogue: 0,0:00:43.64,0:00:47.68,Default,,0000,0000,0000,,And we know that the force of\Ngravity between two objects
Dialogue: 0,0:00:47.68,0:00:51.67,Default,,0000,0000,0000,,is equal to big G, the\Ngravitational constant, times
Dialogue: 0,0:00:51.67,0:00:55.00,Default,,0000,0000,0000,,the mass of the first\Nobject, times the mass
Dialogue: 0,0:00:55.00,0:00:59.06,Default,,0000,0000,0000,,of the second object over\Nthe distance between the two
Dialogue: 0,0:00:59.06,0:01:00.83,Default,,0000,0000,0000,,objects squared.
Dialogue: 0,0:01:00.83,0:01:02.55,Default,,0000,0000,0000,,And if the space\Nshuttle is right here,
Dialogue: 0,0:01:02.55,0:01:06.59,Default,,0000,0000,0000,,only a few hundred miles above\Nthe surface of the Earth,
Dialogue: 0,0:01:06.59,0:01:08.57,Default,,0000,0000,0000,,this r isn't that different.
Dialogue: 0,0:01:08.57,0:01:10.52,Default,,0000,0000,0000,,It's a little bit\Nfurther than if you
Dialogue: 0,0:01:10.52,0:01:11.89,Default,,0000,0000,0000,,were at the surface\Nof the Earth.
Dialogue: 0,0:01:11.89,0:01:16.27,Default,,0000,0000,0000,,Remember that r is measured from\Nwherever you are to the center,
Dialogue: 0,0:01:16.27,0:01:17.89,Default,,0000,0000,0000,,from the center of\Nthe Earth, or really
Dialogue: 0,0:01:17.89,0:01:20.10,Default,,0000,0000,0000,,the center of the object\Nto the center of the Earth.
Dialogue: 0,0:01:20.10,0:01:22.95,Default,,0000,0000,0000,,The center of the Earth\Nrepresents most of the distance
Dialogue: 0,0:01:22.95,0:01:23.45,Default,,0000,0000,0000,,here.
Dialogue: 0,0:01:23.45,0:01:25.23,Default,,0000,0000,0000,,So if I'm at the\Nsurface of the Earth
Dialogue: 0,0:01:25.23,0:01:27.44,Default,,0000,0000,0000,,or if I'm just a few hundred\Nmiles above the surface
Dialogue: 0,0:01:27.44,0:01:30.88,Default,,0000,0000,0000,,of the Earth, it's not going\Nto change r that dramatically,
Dialogue: 0,0:01:30.88,0:01:33.60,Default,,0000,0000,0000,,especially in terms\Nof percentage.
Dialogue: 0,0:01:33.60,0:01:35.87,Default,,0000,0000,0000,,So when you look at it this\Nway, it seems pretty clear
Dialogue: 0,0:01:35.87,0:01:38.76,Default,,0000,0000,0000,,that the force of\Ngravity for someone who
Dialogue: 0,0:01:38.76,0:01:42.05,Default,,0000,0000,0000,,is in space only a few\Nhundred miles above the Earth
Dialogue: 0,0:01:42.05,0:01:46.14,Default,,0000,0000,0000,,should not be that different\Nthan the force of gravity
Dialogue: 0,0:01:46.14,0:01:48.90,Default,,0000,0000,0000,,for someone who is on\Nthe surface of the Earth.
Dialogue: 0,0:01:48.90,0:01:51.54,Default,,0000,0000,0000,,So my question to\Nyou is, what gives?
Dialogue: 0,0:01:51.54,0:01:53.96,Default,,0000,0000,0000,,If there should be\Ngravity in space,
Dialogue: 0,0:01:53.96,0:01:55.52,Default,,0000,0000,0000,,how can we see all\Nof these pictures
Dialogue: 0,0:01:55.52,0:01:58.66,Default,,0000,0000,0000,,of people floating\Naround like this?
Dialogue: 0,0:01:58.66,0:02:02.03,Default,,0000,0000,0000,,And the answer is that\Nthere is gravity in space,
Dialogue: 0,0:02:02.03,0:02:05.15,Default,,0000,0000,0000,,and that these people\Nactually are falling.
Dialogue: 0,0:02:05.15,0:02:08.40,Default,,0000,0000,0000,,They're just moving fast\Nenough relative to the Earth
Dialogue: 0,0:02:08.40,0:02:09.71,Default,,0000,0000,0000,,that they keep missing it.
Dialogue: 0,0:02:09.71,0:02:11.75,Default,,0000,0000,0000,,And let me show you what\NI'm talking about there.
Dialogue: 0,0:02:16.22,0:02:18.03,Default,,0000,0000,0000,,Let's say I'm sitting\Nhere in Africa,
Dialogue: 0,0:02:18.03,0:02:20.76,Default,,0000,0000,0000,,and I were to shoot\Nsomething, if maybe I
Dialogue: 0,0:02:20.76,0:02:22.31,Default,,0000,0000,0000,,have a really good\Nsling shot, and I
Dialogue: 0,0:02:22.31,0:02:25.83,Default,,0000,0000,0000,,were to sling something super\Nfast and maybe at a 45 degree
Dialogue: 0,0:02:25.83,0:02:27.97,Default,,0000,0000,0000,,angle, it might take\Noff a little bit
Dialogue: 0,0:02:27.97,0:02:29.70,Default,,0000,0000,0000,,and eventually\Nhit another point.
Dialogue: 0,0:02:29.70,0:02:32.16,Default,,0000,0000,0000,,And this would actually already\Nbe a super duper slingshot.
Dialogue: 0,0:02:32.16,0:02:34.86,Default,,0000,0000,0000,,I just made it travel a couple\Nof thousand miles or at least
Dialogue: 0,0:02:34.86,0:02:36.18,Default,,0000,0000,0000,,over 1,000 miles.
Dialogue: 0,0:02:36.18,0:02:38.12,Default,,0000,0000,0000,,If I make it go a\Nlittle bit faster,
Dialogue: 0,0:02:38.12,0:02:40.62,Default,,0000,0000,0000,,if I put a little\Nbit more force on,
Dialogue: 0,0:02:40.62,0:02:43.66,Default,,0000,0000,0000,,if I just propelled the\Nprojectile a little bit faster,
Dialogue: 0,0:02:43.66,0:02:45.19,Default,,0000,0000,0000,,it might go a\Nlittle bit further,
Dialogue: 0,0:02:45.19,0:02:47.34,Default,,0000,0000,0000,,but it will eventually\Nfall back to the Earth.
Dialogue: 0,0:02:47.34,0:02:50.48,Default,,0000,0000,0000,,Let's try to propel it a\Nlittle bit faster than that.
Dialogue: 0,0:02:50.48,0:02:52.63,Default,,0000,0000,0000,,Then it'll still\Nfall to the Earth.
Dialogue: 0,0:02:52.63,0:02:54.92,Default,,0000,0000,0000,,Let's propel it even\Nfaster than that.
Dialogue: 0,0:02:54.92,0:02:57.93,Default,,0000,0000,0000,,Well then, it's still eventually\Ngoing to fall to the Earth.
Dialogue: 0,0:02:57.93,0:02:59.68,Default,,0000,0000,0000,,I think you might see\Nwhere this is going.
Dialogue: 0,0:02:59.68,0:03:01.21,Default,,0000,0000,0000,,Let's go even faster than that.
Dialogue: 0,0:03:01.21,0:03:02.94,Default,,0000,0000,0000,,So if we go even\Nfaster than that,
Dialogue: 0,0:03:02.94,0:03:04.40,Default,,0000,0000,0000,,eventually it'll\Nfall to the Earth.
Dialogue: 0,0:03:04.40,0:03:07.49,Default,,0000,0000,0000,,Even faster than\Nthat, so if you were
Dialogue: 0,0:03:07.49,0:03:10.63,Default,,0000,0000,0000,,to throw an object\Neven faster than that,
Dialogue: 0,0:03:10.63,0:03:14.12,Default,,0000,0000,0000,,it would then go really far\Nand then fall to the Earth.
Dialogue: 0,0:03:14.12,0:03:15.49,Default,,0000,0000,0000,,I think you see\Nwhat's happening.
Dialogue: 0,0:03:15.49,0:03:17.81,Default,,0000,0000,0000,,Every time you go\Nfaster and faster,
Dialogue: 0,0:03:17.81,0:03:20.64,Default,,0000,0000,0000,,you throw this projectile\Nfaster and faster,
Dialogue: 0,0:03:20.64,0:03:24.07,Default,,0000,0000,0000,,it gets further and\Nfurther, up to some velocity
Dialogue: 0,0:03:24.07,0:03:27.54,Default,,0000,0000,0000,,that you release\Nthis projectile,
Dialogue: 0,0:03:27.54,0:03:30.05,Default,,0000,0000,0000,,and whenever it's trying\Nto fall to the Earth,
Dialogue: 0,0:03:30.05,0:03:32.73,Default,,0000,0000,0000,,it's going so fast that it\Nkeeps missing the Earth.
Dialogue: 0,0:03:32.73,0:03:36.71,Default,,0000,0000,0000,,So it'll keep going around and\Naround and around the Earth,
Dialogue: 0,0:03:36.71,0:03:40.91,Default,,0000,0000,0000,,and a projectile like that\Nwould essentially be in orbit.
Dialogue: 0,0:03:40.91,0:03:42.38,Default,,0000,0000,0000,,So what's happening\Nis if there was
Dialogue: 0,0:03:42.38,0:03:46.14,Default,,0000,0000,0000,,no gravity for that projectile,\Nif there was no gravity,
Dialogue: 0,0:03:46.14,0:03:51.44,Default,,0000,0000,0000,,the projectile would just\Ngo straight away into space.
Dialogue: 0,0:03:51.44,0:03:54.32,Default,,0000,0000,0000,,But because there's gravity,\Nit's constantly pulling it
Dialogue: 0,0:03:54.32,0:03:57.75,Default,,0000,0000,0000,,towards the center of\Nthe Earth, or the center
Dialogue: 0,0:03:57.75,0:04:00.02,Default,,0000,0000,0000,,of that projectile and\Nthe center of the Earth
Dialogue: 0,0:04:00.02,0:04:01.78,Default,,0000,0000,0000,,are being pulled\Ntowards each other,
Dialogue: 0,0:04:01.78,0:04:03.53,Default,,0000,0000,0000,,I guess is a better\Nway to think about it.
Dialogue: 0,0:04:03.53,0:04:05.46,Default,,0000,0000,0000,,The force of gravity\Nis doing that.
Dialogue: 0,0:04:05.46,0:04:07.43,Default,,0000,0000,0000,,And so it's curving its path.
Dialogue: 0,0:04:07.43,0:04:10.45,Default,,0000,0000,0000,,And if it's going fast enough,\Nif the projectile or whatever
Dialogue: 0,0:04:10.45,0:04:12.45,Default,,0000,0000,0000,,object we're talking about\Nis going fast enough,
Dialogue: 0,0:04:12.45,0:04:15.70,Default,,0000,0000,0000,,it'll just keep going\Nround and round the Earth.
Dialogue: 0,0:04:15.70,0:04:20.19,Default,,0000,0000,0000,,And since there is almost,\Npretty much, for most purposes
Dialogue: 0,0:04:20.19,0:04:24.19,Default,,0000,0000,0000,,no air if you go high enough,\Nespecially the altitude
Dialogue: 0,0:04:24.19,0:04:28.05,Default,,0000,0000,0000,,that the space shuttle\Nis, no noticeable drag,
Dialogue: 0,0:04:28.05,0:04:29.90,Default,,0000,0000,0000,,this thing can\Njust keep on going
Dialogue: 0,0:04:29.90,0:04:31.37,Default,,0000,0000,0000,,for a substantial\Namount of time.
Dialogue: 0,0:04:31.37,0:04:33.20,Default,,0000,0000,0000,,Although there is just\Na little bit of drag,
Dialogue: 0,0:04:33.20,0:04:37.03,Default,,0000,0000,0000,,and that's why over time you\Ndo have satellites slow down,
Dialogue: 0,0:04:37.03,0:04:39.74,Default,,0000,0000,0000,,because there is just a\Nlittle bit of air resistance.
Dialogue: 0,0:04:39.74,0:04:42.47,Default,,0000,0000,0000,,So the answer to\Nthis conundrum is
Dialogue: 0,0:04:42.47,0:04:45.26,Default,,0000,0000,0000,,that there actually is gravity.
Dialogue: 0,0:04:45.26,0:04:47.41,Default,,0000,0000,0000,,It's not a gravity-free\Nenvironment.
Dialogue: 0,0:04:47.41,0:04:50.66,Default,,0000,0000,0000,,It's just that the astronauts\Nand the space shuttle
Dialogue: 0,0:04:50.66,0:04:52.76,Default,,0000,0000,0000,,and everything else that's\Nin the space shuttle,
Dialogue: 0,0:04:52.76,0:04:55.23,Default,,0000,0000,0000,,it's all falling,\Nbut it's moving
Dialogue: 0,0:04:55.23,0:04:57.45,Default,,0000,0000,0000,,fast enough that it\Nnever hits the Earth.
Dialogue: 0,0:04:57.45,0:04:58.77,Default,,0000,0000,0000,,It keeps missing the Earth.
Dialogue: 0,0:04:58.77,0:05:01.57,Default,,0000,0000,0000,,It keeps going round\Nand round and round,
Dialogue: 0,0:05:01.57,0:05:04.86,Default,,0000,0000,0000,,but it is completely under\Nthe influence of gravity.
Dialogue: 0,0:05:04.86,0:05:07.47,Default,,0000,0000,0000,,If they were to just\Nslow themselves down,
Dialogue: 0,0:05:07.47,0:05:11.18,Default,,0000,0000,0000,,if they were to just brake\Nrelative to the Earth,
Dialogue: 0,0:05:11.18,0:05:14.24,Default,,0000,0000,0000,,and if they were to just\Nput their brakes on right
Dialogue: 0,0:05:14.24,0:05:17.91,Default,,0000,0000,0000,,over there, they would all\Njust plummet to the Earth.
Dialogue: 0,0:05:17.91,0:05:21.60,Default,,0000,0000,0000,,So there's nothing special\Nabout going 300 or 400 miles up
Dialogue: 0,0:05:21.60,0:05:24.50,Default,,0000,0000,0000,,into space, that all of a\Nsudden gravity disappears.
Dialogue: 0,0:05:24.50,0:05:26.58,Default,,0000,0000,0000,,The influence of gravity,\Nactually on some level,
Dialogue: 0,0:05:26.58,0:05:27.46,Default,,0000,0000,0000,,it just keeps going.
Dialogue: 0,0:05:27.46,0:05:29.66,Default,,0000,0000,0000,,You can't, it might\Nbecome unnoticeably
Dialogue: 0,0:05:29.66,0:05:31.85,Default,,0000,0000,0000,,small at some point,\Nbut definitely
Dialogue: 0,0:05:31.85,0:05:33.89,Default,,0000,0000,0000,,for only a couple of\Nhundred miles up in the air,
Dialogue: 0,0:05:33.89,0:05:35.94,Default,,0000,0000,0000,,there is definitely\Ngravity there.
Dialogue: 0,0:05:35.94,0:05:38.19,Default,,0000,0000,0000,,It's just they're in orbit,\Nthey're going fast enough.
Dialogue: 0,0:05:38.19,0:05:39.87,Default,,0000,0000,0000,,So if they just keep\Nfalling, they're
Dialogue: 0,0:05:39.87,0:05:41.46,Default,,0000,0000,0000,,never going to hit the Earth.
Dialogue: 0,0:05:41.46,0:05:42.96,Default,,0000,0000,0000,,And if you want to\Nsimulate gravity,
Dialogue: 0,0:05:42.96,0:05:45.97,Default,,0000,0000,0000,,and this is actually how\NNASA does simulate gravity,
Dialogue: 0,0:05:45.97,0:05:47.98,Default,,0000,0000,0000,,is that they will put\Npeople in a plane,
Dialogue: 0,0:05:47.98,0:05:49.96,Default,,0000,0000,0000,,and they call it\Nthe vomit rocket
Dialogue: 0,0:05:49.96,0:05:51.92,Default,,0000,0000,0000,,because it's known\Nto make people sick,
Dialogue: 0,0:05:51.92,0:05:54.03,Default,,0000,0000,0000,,and they'll make them go\Nin a projectile motion.
Dialogue: 0,0:05:54.03,0:05:57.29,Default,,0000,0000,0000,,So if this is the ground,\Nin a projectile path
Dialogue: 0,0:05:57.29,0:05:59.70,Default,,0000,0000,0000,,or in a parabolic\Npath I should say,
Dialogue: 0,0:05:59.70,0:06:02.37,Default,,0000,0000,0000,,so the plane will\Ntake off, and it
Dialogue: 0,0:06:02.37,0:06:07.80,Default,,0000,0000,0000,,will do a path exactly the\Nsame as something in free fall
Dialogue: 0,0:06:07.80,0:06:09.52,Default,,0000,0000,0000,,or in a parabolic path.
Dialogue: 0,0:06:09.52,0:06:11.49,Default,,0000,0000,0000,,And so anyone who's\Nsitting in that plane
Dialogue: 0,0:06:11.49,0:06:13.57,Default,,0000,0000,0000,,will experience free fall.
Dialogue: 0,0:06:13.57,0:06:16.01,Default,,0000,0000,0000,,So if you've ever been\Nin, if you've ever right
Dialogue: 0,0:06:16.01,0:06:18.12,Default,,0000,0000,0000,,when you jump off of a\Nor if you've ever bungee
Dialogue: 0,0:06:18.12,0:06:21.85,Default,,0000,0000,0000,,jumped or skydived\Nor even the feeling
Dialogue: 0,0:06:21.85,0:06:23.94,Default,,0000,0000,0000,,when a roller coaster is\Ngoing right over the top,
Dialogue: 0,0:06:23.94,0:06:25.73,Default,,0000,0000,0000,,and it's pulling you\Ndown, and your stomach
Dialogue: 0,0:06:25.73,0:06:28.78,Default,,0000,0000,0000,,feels a little ill, that\Nfeeling of free fall, that's
Dialogue: 0,0:06:28.78,0:06:31.72,Default,,0000,0000,0000,,the exact same feeling\Nthat these astronauts feel
Dialogue: 0,0:06:31.72,0:06:34.19,Default,,0000,0000,0000,,because they're in a\Nconstant state of free fall.
Dialogue: 0,0:06:34.19,0:06:37.39,Default,,0000,0000,0000,,But that is an\Nindistinguishable feeling from,
Dialogue: 0,0:06:37.39,0:06:40.57,Default,,0000,0000,0000,,if you were just in deep space\Nand you weren't anywhere close
Dialogue: 0,0:06:40.57,0:06:45.74,Default,,0000,0000,0000,,any noticeable mass, that is\Nan identical feeling that you
Dialogue: 0,0:06:45.74,0:06:50.29,Default,,0000,0000,0000,,would feel to having no\Ngravitational force around you.
Dialogue: 0,0:06:50.29,0:06:52.34,Default,,0000,0000,0000,,So hopefully that clarifies\Nthings a little bit.
Dialogue: 0,0:06:52.34,0:06:54.46,Default,,0000,0000,0000,,To someone who's just\Nsitting in the space shuttle,
Dialogue: 0,0:06:54.46,0:06:56.28,Default,,0000,0000,0000,,and if they had no\Nwindows, there's
Dialogue: 0,0:06:56.28,0:06:58.02,Default,,0000,0000,0000,,no way of them\Nknowing whether they
Dialogue: 0,0:06:58.02,0:07:00.00,Default,,0000,0000,0000,,are close to a massive\Nobject and they're just
Dialogue: 0,0:07:00.00,0:07:03.65,Default,,0000,0000,0000,,in free fall around it, they're\Nin orbit, or whether they're
Dialogue: 0,0:07:03.65,0:07:06.30,Default,,0000,0000,0000,,just completely far away\Nfrom any massive object,
Dialogue: 0,0:07:06.30,0:07:09.08,Default,,0000,0000,0000,,and they really are in\Na state of or in a place
Dialogue: 0,0:07:09.08,0:07:11.28,Default,,0000,0000,0000,,where there's very\Nlittle gravity.