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  • Have you ever been floating in a swimming pool,

  • all comfy and warm, thinking,

  • "Man, it'd be cool to be an astronaut!

  • You could float out in outer space,

  • look down at the Earth and everything.

  • It'd be so neat!"

  • Only that's not how it is at all.

  • If you are in outer space,

  • you are orbiting the Earth,

  • it's called free fall.

  • You're actually falling towards the Earth.

  • Alright, think about this for a moment.

  • That's the feeling you get

  • if you're going over the top of a roller coaster,

  • going, like, "Whoooooaaaahhhh!"

  • Only you're doing this the whole time

  • you're orbiting the Earth

  • for two,

  • three,

  • four

  • hours,

  • days,

  • whatever it takes, right?

  • So, how does orbiting work?

  • Let's take a page from Isaac Newton.

  • He had this idea,

  • a little mental experiment.

  • You take a cannon,

  • you put it on top of a hill.

  • If you shoot the cannon ball,

  • it goes a little bit away.

  • But if you shoot it harder,

  • it goes far enough so that it lands

  • a little bit past the curvature of Earth.

  • Well, you can imagine

  • if you shot it really, really, really hard,

  • it would go all the way around the Earth

  • and come back, boom!

  • and, like, hit you in the backside or something.

  • Let's zoom way back

  • and put you in a little satellite

  • over the North Pole of the Earth

  • and consider north to be up.

  • You're going to fall down and hit the Earth.

  • But you are actually moving sideways really fast.

  • So, when you fall down,

  • you're going to miss.

  • You're going to end up on the side of the Earth,

  • falling down,

  • and now the Earth is pulling you back in sideways.

  • Alright, and so it's pulling you back in

  • and you fall down,

  • and so you miss the Earth again,

  • and now you're under the Earth.

  • And the Earth is going to pull you up,

  • but you're moving sideways still.

  • So, you're going to miss the Earth again.

  • Now, you're on the other side of the Earth,

  • moving upward and the Earth's pulling you sideways.

  • Alright, so you're going to fall sideways,

  • but you're going to be moving up and to a miss.

  • And now you're back on top of the Earth again,

  • over the North Pole,

  • going sideways and falling down,

  • and yep, you guessed it.

  • You'll keep missing because you're moving so fast.

  • In this way, astronauts orbit the Earth.

  • They're always falling towards the Earth,

  • but they're always missing,

  • and therefore, they're falling all the time.

  • They feel like they're falling,

  • so you just have to kind of get over it.

  • So, technically, if you ran fast enough and tripped,

  • you could miss the Earth.

  • But there's a big problem.

  • First, you have to be going 8 kilometers a second.

  • That's 18,000 miles an hour,

  • just over Mach 23!

  • The second problem:

  • If you're going that fast,

  • yes, you would orbit the Earth

  • and come back where you came from,

  • but there's a lot of air in the way,

  • alright, much less people and things.

  • So, you would burn up due to atmospheric friction.

  • So, I do not recommend this.

Have you ever been floating in a swimming pool,

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B1 TED-Ed earth sideways falling outer space orbiting

【TED-Ed】Free falling in outer space - Matt J. Carlson

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    阿多賓 posted on 2014/11/28
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