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  • Have you ever been floating in a swimming pool,

    你是否曾在泳池上漂浮,

  • all comfy and warm, thinking,

    暖洋洋地想著:

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

    「啊!要是能當個太空人就酷斃了!

  • You could float out in outer space,

    你可以在外太空漂浮

  • look down at the Earth and everything.

    鳥瞰地球的一切

  • It'd be so neat!"

    這種感覺肯定棒透了!」

  • Only that's not how it is at all.

    遺憾的是,現實是殘酷的。

  • If you are in outer space,

    你如果在外太空,

  • you are orbiting the Earth,

    你會繞著地球運轉,

  • it's called free fall.

    這就是所謂「自由落體」。

  • You're actually falling towards the Earth.

    你其實正筆直地朝地球落下,

  • Alright, think about this for a moment.

    嗯,這樣想一下好了,

  • That's the feeling you get

    這種感覺就像是,

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

    「你坐的雲霄飛車爬到至高點,然後

  • going, like, "Whoooooaaaahhhh!"

    咻-哇哇挖嗄啊啊啊!」的那種感覺

  • Only you're doing this the whole time

    只差在你會這樣下去,

  • you're orbiting the Earth

    繞著地球轉。

  • for two,

    兩個,

  • three,

    三個,

  • four

    四個,

  • hours,

    小時

  • days,

    甚至好幾天,

  • whatever it takes, right?

    無論多久,是吧?

  • So, how does orbiting work?

    那繞地公轉的原理是什麼呢?

  • Let's take a page from Isaac Newton.

    這時候就有請牛頓老師為我們解釋了,

  • He had this idea,

    他先這麼想的,

  • a little mental experiment.

    進行一個小小的思想實驗。

  • You take a cannon,

    你搬出一座大砲,

  • you put it on top of a hill.

    放在小山巔上,

  • If you shoot the cannon ball,

    假使你發射一枚砲彈,

  • it goes a little bit away.

    它飛不遠就落地了。

  • But if you shoot it harder,

    但若你發射的更有力一些,

  • it goes far enough so that it lands

    它就能飛衝地更遠,最終落在

  • a little bit past the curvature of Earth.

    地球曲線的較深處。

  • Well, you can imagine

    想得更遠些,

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

    如果你以很快很快的速度把炮彈發射出去,

  • it would go all the way around the Earth

    它會開始一路繞地球轉,

  • and come back, boom!

    踅了一圈回來,咚!

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

    命中你的屁屁或之類的。

  • Let's zoom way back

    現在把鏡頭拉回外太空,

  • and put you in a little satellite

    將你放進一個人造衛星,

  • over the North Pole of the Earth

    以北極上空為起始點,

  • and consider north to be up.

    並視北方為向上的方向。

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

    你理應落下然後撞上地球,

  • But you are actually moving sideways really fast.

    但實際上你沿切線方向快速移動,

  • So, when you fall down,

    因此當你落下時,

  • you're going to miss.

    你會與地球擦身而過。

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

    最終你飛到地球的西端點,

  • falling down,

    向南方掉下去,

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

    但現在地球把你往側面拉,

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

    於是把你吸回來,

  • and you fall down,

    然而你持續落下,

  • and so you miss the Earth again,

    你再度與它擦肩而過。

  • and now you're under the Earth.

    現在你位於地球正下方,

  • And the Earth is going to pull you up,

    它會將你往上拉,

  • but you're moving sideways still.

    但你依然沿切線移動,

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

    結果你三度與地球失之交臂。

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

    現在你位處地球的東端點,

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

    向上移動的同時,地球把你拉往一旁,

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

    於是你會往一旁落向地球,

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

    但正因你向上移動,搞到最後仍然與地球無緣。

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

    現在,你再次回到地球的正上方,

  • over the North Pole,

    北極上空,

  • going sideways and falling down,

    不斷沿切線移動,同時往地球落下。

  • and yep, you guessed it.

    沒錯,同你猜測的,

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

    你會因為移動迅速而持續與地球擦身而過。

  • In this way, astronauts orbit the Earth.

    太空人就是照這個原理繞著地球轉。

  • They're always falling towards the Earth,

    他們不停落向地球,

  • but they're always missing,

    但終究還是撞不著它。

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

    所以他們始終都在落下,

  • They feel like they're falling,

    他們也感到自己正在落下,

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

    所以,嗯,習慣就好啦。

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

    從技術上說,假設你衝得夠快,猛然跌飛出去,

  • you could miss the Earth.

    你也許再也碰不著地球了。

  • But there's a big problem.

    但,問題來了。

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

    首先,你必須每秒狂奔8公里,

  • That's 18,000 miles an hour,

    相當於時速18,000英里,

  • just over Mach 23!

    甚至比23倍音速還快!

  • The second problem:

    問題二:

  • If you're going that fast,

    要是你真能跑那麼快,

  • yes, you would orbit the Earth

    你的確會繞著地球轉,

  • and come back where you came from,

    然後回到原點,

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

    然而一路上會有大量的空氣等著你,

  • alright, much less people and things.

    甭提更礙事的人們和東西。

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

    你會因與大氣過度摩擦而燒得精光。

  • So, I do not recommend this.

    所以,我勸你別這麼做。

Have you ever been floating in a swimming pool,

你是否曾在泳池上漂浮,

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B1 中級 中文 TED-Ed 地球 外太空 發射 北極 太空人

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

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    阿多賓 發佈於 2014 年 11 月 28 日
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