太空中的枪：英语精读讲义

Hey, Vsauce.

嗨，Vsauce。

Michael here.

我是 Michael。

And what do you say we get outta here? 講解

要不我们离开这儿吧？

To space and into an orbit.

去太空，进入轨道。

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

这样我们就能四处漂浮，摆脱重力的影响。

Except not really. 表達脈絡

但其实并不是。

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

绕地球运行的航天员，受到的引力其实和你我此刻感受到的几乎一样。

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

最大的区别是，那些航天员一直在朝地球坠落，

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

但他们的角速度非常大，坠落的速度恰好和地球表面从他们下方弯曲远离的速度一样快。

Now, of course,

当然，

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

这没什么新鲜的……牛顿大炮早就告诉过我们了。

Gravity makes stuff fall,

重力会让物体下落，

and in particular

更确切地说，

Newton realized that it makes objects accelerate towards the Earth

牛顿发现，重力会让物体朝地球加速，

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

而加速度大小与物体水平移动得有多快无关。

That's called relativity.

这就叫相对性。

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

当然，绕轨道运行其实就是坠落，

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

只不过在坠落时，你的水平速度快到足以让地球表面更快地从脚下弯离。

In order to successfully fall and miss the Earth, 習語

要想在坠落时成功错过地球，

unless you dug a tunnel, 語法

除非你挖了一条隧道，

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

否则你得以接近每小时 1.7 万英里，也就是每秒 8 千米的速度飞行。

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

所以，还没等你享受这趟旅程，你多半早就因与空气摩擦而烧成灰了。

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

当然，牛顿的思想实验是以地球为对象，

but on something smaller like the Moon,

但如果换成月球这样更小的天体，

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

大炮不需要以那么高的速度发射炮弹，就能让它完成一圈轨道运行。

In fact,

事实上，

if you had a powerful enough gun 語法

如果你有一把威力足够大的枪，

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

在月球上把枪对准地平线开火，然后等上一会儿，

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

同一颗子弹就可能从后面击中你的后脑勺。

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

Henry 计算得出，子弹的速度必须达到约每秒 1,600 米，

which is exactly how fast the Paris gun fires. 語法

这恰好就是“巴黎大炮”的炮弹初速。

Now, that's a powerful gun.

这把枪的威力可真大。

It's no squirt gun. 習語

它可不是什么水枪。

But if you had a squirt gun out there in space

但如果你在太空中有一把水枪，

and you fired a stream of water at the Sun,

并朝太阳射出一股水流，

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

得用多少水才能浇灭太阳？

I mean, in general 表達脈絡

我是说，一般来说，

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

把水浇到滚烫的东西上，会让它损失一些热量，

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

尤其是在太空中，水会冻成冰。

But here's the issue. 表達脈絡

但问题来了。

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

太阳并不是一大团正在燃烧的氢。

Instead,

实际上，

the Sun is powered by fusion. 用詞

太阳的能量来自核聚变。

Fusion of hydrogen nuclei,

也就是氢原子核的聚变，

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

这有点像构成水的氢和氧之间形成的化学键，

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

只不过尺度小得多，能量也强大得多。

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

在我被一边冲来的核物理学家和另一边冲来的化学家扑倒之前，

let me explain.

先听我解释。

A bond of any sort,

任何一种“键”，

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

无论存在于行星、分子、原子、原子核还是夸克之间，

is just a happenstance where two or more particles together

都不过是这样一种偶然情况：两个或更多粒子结合在一起时，

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

其总能量比彼此分开时更低。

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

就像你结婚之后，税反而少交了。

So, when you form a bond,

所以，当一个键形成时，

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

原本两个独立粒子所多出的那部分能量就会释放出来。

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

又因为有个叫作 E=mc² 的小关系式，

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

这实际上意味着，这一对粒子的质量也会稍微减少。

For example,

举个例子，

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

每次聚变反应都会把少量氢的质量转化成光。

Sunlight, for example,

比如太阳光，

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

就意味着太阳每年会损失 1×10^17 千克的质量。

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

这相当于一颗中等大小的小行星。

But stars have a lot of mass.

但恒星拥有巨大的质量。

And the more massive a star is, 語法

而且恒星的质量越大，

the hotter it burns.

燃烧得就越热。

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

往太阳里加入大量的水，只会增加它的质量。

So, it would burn brighter, 表達脈絡

所以，它会燃烧得更明亮，

not go out.

而不会熄灭。

Of course, it would also burn faster,

当然，它也会燃烧得更快，

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

这意味着它的寿命会更短。

For instance,

例如，

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

如果你往太阳里加入相当于 20 个太阳质量的水，

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

就会把它目前还有 50 亿年的预期寿命

to only a few hundred million more years.

缩短到只剩几亿年。

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

不过，还有一种更快的方法能让太阳熄灭。

Take that water or whatever material you want 語法

把那些水，或者任何你想用的物质，

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

以一种能让所有物质四散开来的方式射入太阳，

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

使其密度不再达到发生核聚变所需的临界值。

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

无论你选择哪种熄灭太阳的方法，

both would be a disaster.

两种都会造成一场灾难。

Literally.

从字面意义上说。

Disaster 文化背景

Disaster（灾难）这个词，

from dis meaning against

源自意为“对抗”的 dis，

and aster meaning star.

以及意为“星星”的 aster。

You would have literally turned our own star against us. 習語

你确实会让我们自己的恒星反过来与我们为敌。

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

如果你不知怎么能像变魔术一样出现在星系际空间，从而躲过这场灾难，

here's a fun experiment to try.

那里有个有趣的实验可以试试。

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

掏出你的枪，开一枪。

That bullet will be forever alone. 習語

那颗子弹将永远孤独。

That's because the universe is expanding,

这是因为宇宙正在膨胀，

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

如果你距离最近的星系团有几百万秒差距，

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

那些星系平均每过一秒就会再远离你 200 千米。

In space terms, 短語搭配

以太空的尺度来说，

200 km/s is pretty slow. 用詞

每秒 200 千米其实相当慢。

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

这也就勉强赶得上太阳系绕银河系中心运行的速度。

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

而更靠近银河系中心的恒星，公转速度可以快上 10 倍。

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

但一颗小小的子弹每秒只能飞几千米，

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

根本不可能追上那些不断远去的星系，

ever.

永远都不可能。

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

这让你意识到，与宇宙的尺度相比，我们是多么渺小。

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

但也会让你意识到，我们所有人在地球上彼此有多么接近。

Of course,

当然，

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

要从地球的一边去往另一边，

you have to fly over half the sphere.

你得飞越半个球面。

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

那么，如果有一条隧道直接贯穿地球呢？

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

让我们转到我的频道 MinutePhysics，看看会发生什么。

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

点击这里，我们在地球另一边见。

Oh, and as always,

对了，还是那句话，

thanks for watching.

谢谢观看。