1
00:00:14,636 --> 00:00:16,835
Have you ever been floating
in a swimming pool,

2
00:00:16,859 --> 00:00:18,525
all comfy and warm, thinking,

3
00:00:18,549 --> 00:00:20,371
"Man, it'd be cool to be an astronaut!

4
00:00:20,395 --> 00:00:23,900
You could float out in outer space,
look down at the Earth and everything.

5
00:00:23,924 --> 00:00:25,082
It'd be so neat!"

6
00:00:25,106 --> 00:00:26,689
Only that's not how it is at all.

7
00:00:26,713 --> 00:00:29,252
If you are in outer space,
you are orbiting the Earth:

8
00:00:29,276 --> 00:00:31,210
it's called free fall.

9
00:00:31,234 --> 00:00:33,240
You're actually falling towards the Earth.

10
00:00:33,264 --> 00:00:35,952
Think about this for a moment:
that's the feeling you get

11
00:00:35,976 --> 00:00:40,265
if you're going over the top
of a roller coaster, going, like, "Whoa!"

12
00:00:40,289 --> 00:00:41,442
Only you're doing this

13
00:00:41,466 --> 00:00:43,466
the whole time you're orbiting the Earth,

14
00:00:43,490 --> 00:00:45,587
for two, three, four hours, days.

15
00:00:45,611 --> 00:00:46,826
Whatever it takes, right?

16
00:00:46,850 --> 00:00:48,540
So, how does orbiting work?

17
00:00:48,564 --> 00:00:50,481
Let's take a page from Isaac Newton.

18
00:00:50,505 --> 00:00:52,616
He had this idea,
a little mental experiment:

19
00:00:52,640 --> 00:00:53,882
You take a cannon,

20
00:00:53,906 --> 00:00:55,265
you put it on top of a hill.

21
00:00:55,289 --> 00:00:56,647
If you shoot the cannonball,

22
00:00:56,671 --> 00:00:57,956
it goes a little bit away.

23
00:00:57,980 --> 00:00:59,275
But if you shoot it harder,

24
00:00:59,299 --> 00:01:01,899
it goes far enough so that it lands

25
00:01:01,923 --> 00:01:04,117
a little bit past the curvature of Earth.

26
00:01:04,141 --> 00:01:06,889
Well, you can imagine if you shot
it really, really, hard,

27
00:01:06,913 --> 00:01:08,891
it would go all the way around the Earth

28
00:01:08,915 --> 00:01:12,146
and come back -- boom! -- and hit you
in the backside or something.

29
00:01:12,170 --> 00:01:14,664
Let's zoom way back
and put you in a little satellite

30
00:01:14,688 --> 00:01:16,268
over the North Pole of the Earth

31
00:01:16,292 --> 00:01:17,892
and consider north to be up.

32
00:01:17,916 --> 00:01:19,991
You're going to fall down
and hit the Earth.

33
00:01:20,015 --> 00:01:23,923
But you are actually moving
sideways really fast.

34
00:01:23,947 --> 00:01:25,272
So when you fall down,

35
00:01:25,296 --> 00:01:26,589
you're going to miss.

36
00:01:26,613 --> 00:01:29,853
You're going to end up on the side
of the Earth, falling down,

37
00:01:29,877 --> 00:01:32,600
and now the Earth is pulling
you back in sideways.

38
00:01:32,624 --> 00:01:34,781
So it's pulling you back in
and you fall down,

39
00:01:34,805 --> 00:01:38,130
and so you miss the Earth again,
and now you're under the Earth.

40
00:01:38,154 --> 00:01:41,346
The Earth is going to pull you up,
but you're moving sideways still.

41
00:01:41,370 --> 00:01:43,292
So you're going to miss the Earth again.

42
00:01:43,316 --> 00:01:46,054
Now you're on the other side
of the Earth, moving upward,

43
00:01:46,078 --> 00:01:47,843
and the Earth's pulling you sideways.

44
00:01:47,867 --> 00:01:49,446
So you're going to fall sideways,

45
00:01:49,470 --> 00:01:51,978
but you're going to be moving up
and so you'll miss.

46
00:01:52,002 --> 00:01:54,968
Now you're back on top of the Earth
again, over the North Pole,

47
00:01:54,992 --> 00:01:56,713
going sideways and falling down,

48
00:01:56,737 --> 00:01:58,008
and yep -- you guessed it.

49
00:01:58,032 --> 00:02:01,035
You'll keep missing
because you're moving so fast.

50
00:02:01,059 --> 00:02:03,459
In this way, astronauts orbit the Earth.

51
00:02:03,483 --> 00:02:05,894
They're always falling towards the Earth,

52
00:02:05,918 --> 00:02:09,475
but they're always missing, and therefore,
they're falling all the time.

53
00:02:09,499 --> 00:02:12,534
They feel like they're falling,
so you just have to get over it.

54
00:02:12,558 --> 00:02:16,729
So technically, if you ran
fast enough and tripped,

55
00:02:16,753 --> 00:02:18,991
you could miss the Earth.

56
00:02:19,015 --> 00:02:20,375
But there's a big problem.

57
00:02:20,399 --> 00:02:24,208
First, you have to be going
eight kilometers a second.

58
00:02:24,232 --> 00:02:26,431
That's 18,000 miles an hour,

59
00:02:26,455 --> 00:02:28,217
just over Mach 23!

60
00:02:28,881 --> 00:02:30,031
The second problem:

61
00:02:30,055 --> 00:02:31,316
If you're going that fast,

62
00:02:31,340 --> 00:02:34,733
yes, you would orbit the Earth
and come back where you came from,

63
00:02:34,757 --> 00:02:36,536
but there's a lot of air in the way,

64
00:02:36,560 --> 00:02:37,901
much less people and things.

65
00:02:37,925 --> 00:02:40,219
So you would burn up
due to atmospheric friction.

66
00:02:40,243 --> 00:02:42,845
So, I do not recommend this.