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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?

萬有引力是甚麼?

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B1 中級 中文 TED-Ed 萬有引力 質量 物體 地球 石頭

【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
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