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• So what is gravity?

萬有引力是甚麼？

• I bet most of you think it's:

我想你們大多會想起：

• "What goes up,

“上了去的東西

• must come down!" Is that right?

一定會跌下來！” 哈，對了

• Well, sorta, but not really.

唔，差不多吧，但不完全如此

• Technically, the law of gravity is an equation.

學術上，萬有引力是一條公式

• It is: F = G x M1 x M2 / R^2,

如果Ｆ等於Ｇ乘Ｍ１乘Ｍ２除以Ｒ的平方

• where G is the universal gravitational constant,

而Ｇ是萬有引力常數

• M1 and M2 are the masses of the two objects,

Ｍ１和Ｍ２是兩個物體的質量

• and R is the distance between them squared.

Ｒ是它倆的距離的平方

• That was easy, right?

這個容易，對嗎？

• Probably not. What does this actually mean?

也許不。但這公式是甚麼意思？

• Well it means that - well, everything is attracted to everything else.

它的意思是：任何物體都會互相吸引

• What I mean by that is if you have two objects, any two objects,

這句話的意思是如果你有兩個物體，任何兩物體

• they are attracted to each other. OK.

它們會互相吸引。

• Let's try and wrap our minds around this.

好，讓我們專心想想

• What happens when you drop a rock off a cliff?

當你從懸崖掉下一塊石頭，會出現甚麼情況？

• It falls to the earth. Right?

這石會跌落地面，對嗎？

• Well, yes, but something else happens.

嗯，對的。但還有其他事情發生

• You see, the law of gravity says that both objects,

你看，萬有引力定律說兩個物體

• the rock and the earth, are attracted to each other.

即石頭和地球，會互相吸引

• This means that the rock falls towards the earth,

意思是石頭會跌向地球

• and the earth falls towards the rock.

而地球會跌向那石頭

• Wait a second - you mean to tell me that if - the earth falls up to meet the rock?

等一等－－你意思是 地球會迎着石頭向上跌嗎？

• Yes, that's exactly what I'm saying.

是的，我的意思正是這樣

• And the reason you don't see the earth fall up to meet the rock

你看不到地球迎着石頭往上跌的原因

• is because the objects move towards each other proportionate to their respective masses.

是因為兩個物體會按 它們質量的比例向對方移動

• The earth is much much much more massive than the rock,

地球的質量比石頭多得很

• so it moves a very very small distance,

所以它只移動了一個非常小的距離

• and the rock is much less massive, so it moves farther

而石頭的質量小的多，因此它相對於地球而言

• with respect to the earth.

移動得遠一點

• Maybe a better way to understand gravity is to take two teenagers

可能更容易明白萬有引力的方法，是叫兩個小伙子

• in spacesuits, and place them far out in space - away from all the planets and the stars.

穿上太空衣，然後放他們在外太空，遠離所有行星和恆星

• It turns out they will be attracted to each other.

我們會發現他倆會互相吸引

• I'm not talking about that kind of attraction.

我說的不是這種吸引力

• See, they have mass, and since they have mass,

看，他們有質量，而由於他們有質量

• they will move towards each other.

他們會移近對方

• They are attracted to each other.

他們會被互相吸引

• Maybe one more thing might help. Have you ever played with two magnets?

或許另一樣東西會有幫助 你試過玩兩塊磁石嗎？

• You know, the magnets with the north and the south poles?

就是有南極和北極的磁石

• When you take the magnets and put them closer to each other,

當你把兩塊磁石移近對方

• they move together. They are attracted to each other.

它們會連接起來，它們會互相吸引

• And the closer they are, the stronger the attraction.

它們的距離越近，吸引力越大

• Think of the mass of the object like the strength of a magnet

試把物體的質量想為磁石的長度

• and the distance between the objects like the distance between the two magnets.

而物體的距離就像兩塊磁石之間的距離

• Now understand, I'm not saying that gravity and magnetism are the same,

要明白，我不是說萬有引力和磁力是一樣的東西

• they just behave in a similar way.

只不過它們有類似的行為

• Let's think of one other thing - astronauts.

讓我們想想另一樣東西－－太空人

• You know, astronauts, they weigh less on the moon

你知道，太空人在月球上的體重

• than on the earth. Why is that?

較在地球上較輕。為甚麼呢？

• Well you see, the moon is less massive than the earth.

你看，月球的質量較地球小得多

• Therefore it has a smaller gravitational pull on the astronaut.

因此它對太空人的引力便較小

• It's like the moon is a weaker magnet.

就好像月球是一塊較弱的磁石

• They aren't as attracted to each other.

它們之間的吸引力沒那麼大

• Distance also plays a role. Think back to playing with a magnet.

距離也有影響。回想把玩磁石的時候

• The pull of the magnets towards each other

磁石間的吸引力

• are stronger when they are closer together. The same is true of gravity.

在它們較接近對方時較大 同樣情況也適用於萬有引力

• For example, the sun is the most massive object near the earth.

例如，太陽是地球附近質量最大的物體

• It dictates most of the gravitational forces in our solar system.

它操控了我們太陽系內的大部份萬有引力

• It is very very massive. But it is relatively far away,

它的質量非常龐大。但由於它相對較遠

• so even though the sun is a much stronger magnet, so to speak,

因此可以說太陽是一塊強得多的磁石

• it is a long ways away.

但是它離我們很遠

• Therefore the attraction isn't as strong.

因此它的吸引力不那麼強

• So let's look back at that law of gravity.

讓我們回看萬有引力定律

• The equation: F = G x M1 x M2 / R ^2.

這公式：Ｆ等於Ｇ乘Ｍ１，Ｍ２，除以Ｒ的平方

• You see the force of gravity is equal to a number.

你看到萬有引力相等於一個數字

• That's that universal gravitational constant G

那就是萬有引力常數Ｇ

• times the mass of object one, times the mass of object two.

乘第一個物體的質量，再乘第二個物體的質量

• Think of M1 being the mass of the sun

設想Ｍ１是太陽的質量

• and M2 being the mass of the earth.

而Ｍ２是地球的質量

• And then we divide by the distance between them squared.

然後我們除以它們之間距離的平方

• This determines the force of attraction between the sun and earth.

便計算出太陽和地球之間的萬有引力

• You could just as easily plug in your mass

你也可以代入你自己的質量

• and the earth's mass and the distance between you and the center of the earth,

和地球的質量，和你和地心之間的距離

• and find out how much you are attracted to the earth,

從而得出你被吸引往地球的力

• and the earth attracted to you.

和地球被你吸引的力

• So, what's gravity?

究竟萬有引力是甚麼？

• Everything is attracted to everything else.

任何東西之間都會互相吸引

• Everything. Oh, one last thing,

任何東西。噢，我忘了一件事

• just to make you wonder. What causes gravity?

我想你想想。萬有引力的成因是甚麼？

• Why are two objects with mass attracted to each other?

為甚麼兩個有質量的物體會互相吸引？

• Well, the answer is -

嗯，答案是

• We don't know.

我們不知道

• The cause of gravity remains a mystery to scientists.

萬有引力的成因對科學家來說仍是個謎

• We don't really know conclusively what causes gravity.

我們真的未能確實知道萬有引力的成因

• It is one of the great mysteries of science.

這是科學界其中一個大奧秘

So what is gravity?

B1 中級 中文 TED-Ed 萬有引力 質量 磁石 物體 地球

# 【TED-Ed】什麼是萬有引力？ How to think about gravity - Jon Bergmann

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VoiceTube   發佈於 2013 年 05 月 11 日