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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,
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.



【TED-Ed】在外太空自由落體會怎樣?(Free falling in outer space - Matt J. Carlson)

12653 分類 收藏
阿多賓 發佈於 2014 年 11 月 29 日    李孟錡 翻譯    Mandy Lin 審核
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