太空中的槍：英語精讀講義

Hey, Vsauce.

嗨，Vsauce。

Michael here.

我是 Michael。

And what do you say we get outta here? 講解

不如我們離開這裡吧？

To space and into an orbit.

前往太空，進入軌道。

That way we could just float around and be free from the influence of gravity. 表達脈絡

這樣我們就能四處漂浮，擺脫重力的影響。

Except not really. 表達脈絡

但其實沒那麼回事。

Astronauts orbiting around the Earth experience pretty much the same gravitational pull that you and I are feeling right now. 片語搭配

繞著地球運行的太空人，受到的重力其實和你我此刻感受到的幾乎一樣。

The major difference is that those astronauts are falling constantly towards Earth, 表達脈絡

最大的差別是，那些太空人一直朝地球墜落，

but their angular velocity is so large that they're falling just as fast as Earth curves away from them. 文法

但他們的角速度非常大，墜落的速度恰好和地球表面從他們下方彎離的速度一樣快。

Now, of course,

當然，

this is nothing New...ton's cannon hasn't already taught us. 文法

這並不是什麼新鮮事……牛頓大砲早就告訴過我們了。

Gravity makes stuff fall,

重力會讓物體下墜，

and in particular

更確切地說，

Newton realized that it makes objects accelerate towards the Earth

牛頓發現，重力會讓物體朝地球加速，

the same amount independently of how fast they're moving horizontally. 片語搭配

而加速度大小與物體水平移動得有多快無關。

That's called relativity.

這就叫相對性。

And of course, orbiting is just falling, 表達脈絡

當然，繞軌道運行其實就是墜落，

but falling where you move horizontally fast enough that the Earth falls away faster. 文法

只不過在墜落時，你的水平速度快到足以讓地球表面更快地從腳下彎離。

In order to successfully fall and miss the Earth, 慣用語

想在墜落時成功錯過地球，

unless you dug a tunnel, 文法

除非你挖了一條隧道，

you'd need to be traveling at almost 17,000 mi/h or 8 km/s.

否則你得以接近每小時 17,000 英里，也就是每秒 8 公里的速度移動。

So, you'd probably incinerate from friction with the air well before you had a chance to enjoy the trip. 片語搭配

所以，還沒等你享受這趟旅程，你大概早就因為與空氣摩擦而燒成灰了。

Of course, Newton's thought experiment involved the Earth, 用詞

當然，牛頓的思想實驗是以地球為對象，

but on something smaller like the Moon,

但如果換成月球這類更小的天體，

the cannon wouldn't have to throw its projectile nearly as fast for it to complete an orbit. 片語搭配

大砲不必用那麼高的速度發射砲彈，就能讓它繞行一圈。

In fact,

事實上，

if you had a powerful enough gun 文法

如果你有一把威力夠強的槍，

on the Moon and you fired that gun at the horizon and then waited a little bit, 片語搭配

在月球上把槍對準地平線開火，然後等一會兒，

you could get hit in the back of the head by the same bullet. 文法

同一顆子彈就可能從後方擊中你的後腦勺。

Henry calculated that the bullet would have to travel about 1,600 m/s,

Henry 計算出，子彈的速度必須達到約每秒 1,600 公尺，

which is exactly how fast the Paris gun fires. 文法

這正好就是「巴黎大砲」的砲彈初速。

Now, that's a powerful gun.

這把槍的威力可真大。

It's no squirt gun. 慣用語

它可不是什麼水槍。

But if you had a squirt gun out there in space

但如果你在太空中有一把水槍，

and you fired a stream of water at the Sun,

並朝太陽射出一道水柱，

how much water would it take to put out the Sun? 文法

得用多少水才能澆熄太陽？

I mean, in general 表達脈絡

我的意思是，一般來說，

putting water on something hot would cause that something hot to lose some heat, 文法

把水澆到滾燙的東西上，會讓它流失一些熱量，

especially since the water will be frozen because it's out there in space.

尤其是在太空中，水會結成冰。

But here's the issue. 表達脈絡

但問題就在這裡。

The Sun is not a big ball of hydrogen on fire. 表達脈絡

太陽並不是一大團正在燃燒的氫。

Instead,

事實上，

the Sun is powered by fusion. 用詞

太陽的能量來自核融合。

Fusion of hydrogen nuclei,

也就是氫原子核的融合，

which is kind of like the chemical bonds between the hydrogen and oxygen that make up water, 講解

這有點像構成水的氫和氧之間形成的化學鍵，

except on a much smaller and much more powerful scale. 片語搭配

只不過尺度小得多，能量也強大得多。

Now, before I get tackled by nuclear physicists from one side and chemists from the other, 慣用語

在我被一邊衝來的核物理學家和另一邊衝來的化學家撲倒之前，

let me explain.

先讓我解釋一下。

A bond of any sort,

任何一種「鍵」，

whether between planets, molecules, atoms, nuclei or quarks, 文法

無論存在於行星、分子、原子、原子核還是夸克之間，

is just a happenstance where two or more particles together

都不過是這樣一種偶然情況：兩個或更多粒子結合在一起時，

have a lower total energy than when they were apart. 文法

總能量會比彼此分開時更低。

Like if you get married and your taxes go down. 表達脈絡

就像你結婚後，稅反而繳得更少。

So, when you form a bond,

所以，當一個鍵形成時，

that extra energy that the two solitary particles had is released.

原本兩個獨立粒子多出的那部分能量就會釋放出來。

And because of a little relation we call E=mc²,

又因為有個叫作 E=mc² 的小關係式，

this actually means that the mass of the pair goes down a little bit too. 表達脈絡

這其實表示，這一對粒子的質量也會稍微減少。

For example,

舉例來說，

every fusion reaction turns a little bit of hydrogenous mass into light. 片語搭配

每次核融合反應，都會把少量氫的質量轉化成光。

Sunlight, for example,

例如太陽光，

amounts to a loss of 100 quadrillion kilograms each year. 片語動詞

就代表太陽每年會損失 1×10^17 公斤的質量。

That's the equivalent of a medium-sized asteroid.

這相當於一顆中型小行星。

But stars have a lot of mass.

但恆星擁有巨大的質量。

And the more massive a star is, 文法

而恆星的質量越大，

the hotter it burns.

燃燒時就越熱。

And adding a bunch of water to the Sun would only cause it to be more massive.

往太陽裡加入大量的水，只會增加它的質量。

So, it would burn brighter, 表達脈絡

所以，它會燃燒得更明亮，

not go out.

而不會熄滅。

Of course, it would also burn faster,

當然，它也會燃燒得更快，

which means that its life would be shorter. 表達脈絡

這表示它的壽命會更短。

For instance,

例如，

if you were to add 20 solar masses of water to the Sun, 文法

如果你往太陽裡加入相當於 20 個太陽質量的水，

you would decrease its life expectancy from the current 5 billion years 片語搭配

就會把它目前還有 50 億年的預期壽命

to only a few hundred million more years.

縮短到只剩幾億年。

But there's a faster way to put out the Sun.

不過，還有一種更快的方法能讓太陽熄滅。

Take that water or whatever material you want 文法

把那些水，或任何你想用的物質，

and shoot it into the Sun in a way that causes everything to get spread out and scattered 講解

以一種能讓所有物質四散開來的方式射入太陽，

so that there's no longer the critical density needed for fusion to occur. 講解

讓密度不再達到發生核融合所需的臨界值。

Now, no matter which avenue of putting out the Sun you pick, 文法

無論你選擇哪一種熄滅太陽的方法，

both would be a disaster.

兩種都會釀成災難。

Literally.

完全是字面上的意思。

Disaster 文化背景

Disaster（災難）這個字，

from dis meaning against

源自意為「對抗」的 dis，

and aster meaning star.

以及意為「星星」的 aster。

You would have literally turned our own star against us. 慣用語

你真的會讓我們自己的恆星反過來與我們為敵。

If you were somehow able to avoid that disaster by magically appearing in intergalactic space, 文法

如果你不知怎麼能像變魔術一樣出現在星系際空間，藉此躲過這場災難，

here's a fun experiment to try.

那裡有個有趣的實驗可以試試。

Take out your gun and fire a bullet. 片語動詞

拿出你的槍，開一槍。

That bullet will be forever alone. 慣用語

那顆子彈將永遠孤單。

That's because the universe is expanding,

這是因為宇宙正在膨脹，

and if you were a few megaparsecs away from the nearest galactic cluster,

如果你距離最近的星系團有幾百萬秒差距，

on average those galaxies would be 200 km farther away from you every passing second. 片語搭配

那些星系平均每過一秒，就會再遠離你 200 公里。

In space terms, 片語搭配

以太空的尺度來說，

200 km/s is pretty slow. 用詞

每秒 200 公里其實相當慢。

It's barely as fast as the solar system orbits the center of the Milky Way. 文法

這也就勉強趕得上太陽系繞銀河系中心運行的速度。

And stars closer to the center of the galaxy can orbit 10 times faster.

而更靠近銀河系中心的恆星，繞行速度可以快上 10 倍。

But a measly bullet travels only a few kilometers every second 用詞

但一顆小小的子彈每秒只能飛幾公里，

and would have no chance of reaching the receding galaxies, 片語搭配

根本不可能追上那些不斷遠去的星系，

ever.

永遠都不可能。

It makes you realize how tiny we are compared to the scale of the universe. 表達脈絡

這讓你意識到，與宇宙的尺度相比，我們是多麼渺小。

But it also makes you realize how close together we all are here on Earth.

但也會讓你意識到，我們所有人在地球上彼此有多麼接近。

Of course,

當然，

to get from one side of the Earth to the other, 片語搭配

想從地球的一側到另一側，

you have to fly over half the sphere.

你得飛越半個球面。

So, what if instead there were a tunnel through the Earth? 文法

那麼，如果有一條隧道直接貫穿地球呢？

Let's jump over to my channel MinutePhysics to see what happens. 片語動詞

讓我們跳到我的頻道 MinutePhysics，看看會發生什麼事。

Click here and I'll see you on the other side. 慣用語

點這裡，我們在地球另一邊見。

Oh, and as always,

對了，一如往常，

thanks for watching.

謝謝收看。