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  • More than six thousand light years from the surface of the earth,

    距離地球表面六千多萬光年,

  • a rapidly spinning neutron star

    有一急速旋轉的中子星

  • called the Black Widow pulsar, blasts its companion brown dwarf star with radiation

    它的輻射使得它的伴星── 褐矮星產生爆炸,

  • as the two orbit each other every 9 hours.

    兩顆星每 9 小時互繞一次。

  • Standing on our own planet,

    在地球上,

  • you might think you're just an observer of this violent ballet.

    可能你以為自己只是這場暴力芭蕾的旁觀者,

  • But in fact, both stars are pulling you towards them.

    但事實上,這兩顆星正把你拉向它們,

  • And you're pulling back,

    同時你在往回拉,

  • connected across trillions of kilometers

    連接數兆公里

  • by gravity.

    通過萬有引力(重力) 。

  • Gravity is the attractive force between two objects with mass

    萬有引力是兩個有質量的 物體的相互吸引力量──

  • any two objects with mass.

    任何兩個有質量的物體。

  • Which means that every object in the universe attracts every other object:

    即是宇宙中任何兩個物體 都具有互相吸引的性質:

  • every star, black hole,

    每一個星球、黑洞、

  • human being, smartphone, and atom

    人類、手機、與原子

  • are all constantly pulling on each other.

    都不斷有互相吸引的力量。

  • So why don't we feel pulled in billions of different directions?

    為什麼我們沒有感受到 從四方八面而來的拉力呢?

  • Two reasons: mass and distance.

    兩個原因:質量與距離。

  • The original equation describing the gravitational force between two objects

    最早描述兩個物體引力的方程式

  • was written by Isaac Newton in 1687.

    是出於 1687 的艾薩克·牛頓。

  • Scientists' understanding of gravity has evolved since then,

    從那時起,科學家 對引力的了解更進化了,

  • but Newton's Law of Universal Gravitation

    但牛頓的萬有引力定律

  • is still a good approximation in most situations.

    在大部分情況下 仍然是相當好的粗略估算。

  • It goes like this:

    萬有引力是這樣的:

  • the gravitational force between two objects

    兩個物體間的引力

  • is equal to the mass of one

    相等於一個物體的質量

  • times the mass of the other,

    乘以另外一個物體的質量,

  • multiplied by a very small number

    再乘以一個小數目,

  • called the gravitational constant,

    叫做引力常數,

  • and divided by the distance between them, squared.

    然後除以兩個物體距離的平方。

  • If you doubled the mass of one of the objects,

    如果你將其中一個物體的質量加倍,

  • the force between them would double, too.

    它們中間的引力會變為雙倍,

  • If the distance between them doubled,

    如果將兩者距離增加增一倍,

  • the force would be one-fourth as strong.

    引力強度就會等於之前的四分之一。

  • The gravitational force between you and the Earth pulls you towards its center,

    你與地球之間的引力 將你拉向地球的中心點,

  • a force you experience as your weight.

    就是你所體驗到的重量。

  • Let's say this force is about 800 Newtons

    舉個例,假設你站在海平面上時的引力

  • when you're standing at sea level.

    是 800 牛頓 。

  • If you traveled to the Dead Sea,

    如果你到死海,

  • the force would increase by a tiny fraction of a percent.

    引力的增加很微小,

  • And if you climbed to the top of Mount Everest, the force would decrease

    假如你爬到珠穆朗瑪峰山頂上,引力將會減少,

  • but again, by a minuscule amount.

    減弱的幅度仍然很小。

  • Traveling higher would make a bigger dent in gravity's influence,

    走到高一些的地方會削弱多一點引力,

  • but you won't escape it.

    但你不能逃避引力。

  • Gravity is generated by variations in the curvature of spacetime

    重量是由時空曲率變異所產生的──

  • the three dimensions of space plus time

    空間的三個維度加上時間──

  • which bend around any object that has mass.

    會因任何具有質量的物體而彎曲。

  • Gravity from Earth reaches the International Space Station,

    來自地球的重力到達國際太空站

  • 400 kilometers above the earth,

    距離地表 400 公里

  • with almost its original intensity.

    幾乎是原來的強度。

  • If the space station was stationary on top of a giant column,

    如果太空站固定在巨大的柱上,

  • you'd still experience ninety percent

    仍可感受到 90%

  • of the gravitational force there that you do on the ground.

    來自地球表面的引力

  • Astronauts just experience weightlessness

    太空人感受不到重力,

  • because the space station is constantly falling towards earth.

    是因為太空站一直向地球方向墜落。

  • Fortunately, it's orbiting the planet fast enough that it never hits the ground.

    幸運的是,它繞地球飛行的速度 快到足以讓它永遠不會掉落地面。

  • By the time you made it to the surface of the moon,

    等你到了月球的表面

  • around 400,000 kilometers away,

    離地球大概是 40 萬公里遠,

  • Earth's gravitational pull would be

    在那裡的地球引力

  • less than 0.03 percent of what you feel on earth.

    只剩下不到你在地球上感受的 0.03%。

  • The only gravity you'd be aware of would be the moon's,

    你只會察覺到來自月球的引力,

  • which is about one sixth as strong as the earth's.

    約是地球引力的六分之一。

  • Travel farther still

    離得更遠一些,

  • and Earth's gravitational pull on you will continue to decrease,

    地球的引力會繼續減少,

  • but never drop to zero.

    但不會是零。

  • Even safely tethered to the Earth,

    即使牢牢地拴在地球上,

  • we're subject to the faint tug of distant celestial bodies and nearby earthly ones.

    我們仍受到遙遠天體和鄰近地球天體的微弱影響。

  • The Sun exerts a force of about half a Newton on you.

    太陽對你施加大概 0.5 牛頓的力量。

  • If you're a few meters away from a smartphone, you'll experience

    若你距離手機幾米遠,你會感受到

  • a mutual force of a few piconewtons.

    彼此間有一兆分之一牛頓的拉力。

  • That's about the same as the gravitational pull

    這樣就好似仙女座星系

  • between you and the Andromeda Galaxy,

    與我們之間的引力,

  • which is 2.5 million light years away

    該星系在 2.5 百萬光年遠處,

  • but about a trillion times as massive as the sun.

    但其質量大約是太陽的一兆倍。

  • But when it comes to escaping gravity,

    談到擺脫重力時

  • there's a loophole.

    有個漏洞。

  • If all the mass around us is pulling on us all the time,

    如果所有環繞我們的質量, 整天地拉向我們,

  • how would Earth's gravity change

    地球的引力如何改變呢?

  • if you tunneled deep below the surface,

    如果你深入地下,

  • assuming you could do so without being cooked or crushed?

    假設你不會被煮熟或壓碎?

  • If you hollowed out the center of a perfectly spherical Earth

    如果你在地心 掏空了一個完美的球形──

  • which it isn't, but let's just say it were

    這只是個理論上的假設──

  • you'd experience an identical pull from all sides.

    你就會感受到來自四面八方 同樣大的拉力。

  • And you'd be suspended, weightless,

    因此你就會懸浮及失重,

  • only encountering the tiny pulls from other celestial bodies.

    只會感受到其他天體的微少牽引。

  • So you could escape the Earth's gravity in such a thought experiment

    你能在這樣的假想實驗中 避開地球的引力──

  • but only by heading straight into it.

    但也只能一頭鑽進去想想罷了。

More than six thousand light years from the surface of the earth,

距離地球表面六千多萬光年,

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B1 中級 中文 美國腔 TED-Ed 引力 地球 物體 質量 牛頓

你要走多遠才能擺脫引力?- Rene Laufer (How far would you have to go to escape gravity? - Rene Laufer)

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    11101130 發佈於 2021 年 01 月 14 日
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