为什么地球是一座监狱以及如何逃离它：英语精读讲义

We are prisoners on Earth. 習語

我们是地球上的囚徒。

The universe taunts us 習語

宇宙在嘲弄我们，

by showing us all the places we can't ever visit.

向我们展示了那些我们永远无法到达的地方。

However, if our species wants to have a long-term future, 語法

然而，如果人类想要有长远的未来，

we have to escape our prison.

我们就必须逃离这座监狱。

But what's keeping us here in the first place? 短語搭配

可是，究竟是什么把我们困在了这里？

Turns out we owe the universe 講解

原来，我们欠了宇宙

a debt that is 4.5 billion years old.

一笔长达45亿年的债务。

Everything with mass in the universe attracts every other thing with mass.

宇宙中所有有质量的物体都会吸引其他有质量的物体。

We call this phenomenon gravity.

我们把这种现象称为引力。

The closer you are to a big chunk of mass,

离一块大质量物体越近，

the stronger the attraction

吸引力就越强，

or the more you're pulled in.

也就是你被拉向它的力量越大。

This effect traps us on Earth.

这种效应将我们困在地球上。

We can imagine this as being prisoners in a gravity prison

我们可以把它想象成被困在引力监狱

or a gravity well. 文化背景

或者是引力阱中的囚徒。

It's not a literal well, 語法

它不是一口真正的井，

but a handy concept to understand how this works.

而是一个方便理解其工作原理的概念。

Being in a gravity prison means

身处引力监狱意味着

that you owe gravity energy.

你欠了引力的能量。

But how can you owe energy?

但你怎么会欠能量呢？

Because in our universe,

因为在我们的宇宙中，

things don't want to change their speed or direction.

物体不想改变它们的速度或方向。

To convince them to move,

为了迫使它们移动，

you have to expend energy. 短語搭配

必须消耗能量。

Billions of years ago,

数十亿年前，

the gravitational attraction of trillions of trillions of dust particles

围绕太阳运行的数以万亿乘万亿计的尘埃颗粒之间的引力

orbiting our sun pulled them together

将它们拉到一起，

until they formed a planet. 語法

直到形成了一颗行星。

This process used energy

这一过程消耗了能量，

and created the gravity well we're now a part of.

并创造了我们现在身处的引力阱。

The deeper you are inside a gravity well,

你在引力阱里陷得越深，

the more energy you owe gravity.

欠引力的能量就越多。

If you don't find a way to get enough energy,

如果你找不到获取足够能量的方法，

you're not able to leave,

你就无法离开，

no matter what you do. 語法

无论你做什么。

Because your atoms were once part of the dust

因为你的原子曾经是那些尘埃的一部分，

that the universe expended energy on

宇宙正是消耗了能量，

to get to this place.

才把它们带到了这里。

Okay.

好吧。

Hmm.

嗯。

Let's summarize all of that again. 表達脈絡

让我们重新总结一下。

Objects in the universe don't like to move.

宇宙中的物体不喜欢移动。

You have to convince them to do so with energy.

你必须用能量来迫使它们移动。

Gravity used energy

引力消耗了能量，

to convince the parts that make up our planet 短語動詞

迫使构成我们星球的各部分

to move together.

聚拢在一起。

This created a gravity prison in the process, 短語搭配

在这个过程中，它创造了一个引力监狱，

trapping us.

困住了我们。

To escape it,

要逃离它，

we need to repay it with energy.

我们需要用能量来偿还。

Okay.

好。

How do we do that?

我们要怎么做呢？

To get into space,

要进入太空，

we need to go through a complicated process 短語動詞

我们需要经历一个复杂的

of exchanging energy.

能量交换过程。

For this purpose,

为此，

we build a negative potential energy repaying machines,

我们建造了“负势能偿还机”，

known by their more boring name, 短語搭配

也就是名字更无趣的

rockets.

火箭。

Rockets work by using some of the most energetic chemical reactions humans know about 語法

火箭通过利用人类已知最剧烈的化学反应工作，

to basically explode fuel in a controlled way.

基本上就是以受控的方式引爆燃料。

This converts chemical energy into kinetic energy. 短語搭配

这将化学能转化为动能。

The exhaust of the reaction is directed outwards

反应产生的废气向外排出，

and pushes the rocket away from Earth.

将火箭推离地球。

By expending a lot of energy, 語法

通过消耗大量能量，

we are increasing our gravitational potential energy,

我们正在增加自身的重力势能，

which is a complicated way 表達脈絡

这种说法有点复杂，

to say that we're paying back our energy debt to gravity.

实际上就是说我们在偿还欠引力的能量债。

But it's actually a lot trickier than that.

但实际上事情要棘手得多。

When you burn fuel to get into orbit,

当你燃烧燃料进入轨道时，

you lose lots of energy to heat,

大量的能量会以热能、

the exhaust,

废气，

and atmospheric drag, 用詞

和大气阻力的形式流失，

so you actually need much more.

所以你实际上需要多得多的能量。

And you can't just pile a huge amount of really explosive dangerous fuel

而且你不能简单地把一大堆极具爆炸危险的燃料

close to your payload

堆在有效载荷旁边

and detonate it.

然后引爆。

You need a controlled burn, 用詞

你需要受控燃烧，

which is complicated and makes your rocket very heavy,

这是非常复杂的，而且会让你的火箭变得很重，

which means it has more mass.

意味着它有更大的质量。

The more mass something has, 語法

物体的质量越大，

the more energy you need to convince it to move.

你就需要越多的能量来迫使它移动。

So you need more fuel to lift up your rocket.

所以你需要更多燃料来升起火箭。

But if you need more fuel,

但是如果需要更多燃料，

that means you need more rocket to carry that fuel.

这意味着你需要更大的火箭来装载那些燃料。

But this makes your rocket heavier,

但这会让你的火箭变得更重，

thus requiring more fuel, 語法

从而需要更多燃料，

which requires more rocket to carry that new fuel,

进而需要更大的火箭来装载那些新加的燃料，

and so on. 短語搭配

如此循环。

At the end of this madness,

在这种疯狂的恶性循环结束时，

you need closer to a 100 times the weight of your payload

你需要近乎有效载荷100倍的重量

to launch.

才能完成发射。

Ariane 6,

阿丽亚娜6号，

for example,

比如，

the European rocket,

就是欧洲的一款火箭，

will weigh 800 tons

它重达800吨，

and should be able to transport 10 tons into geostationary transfer orbit

能够将10吨有效载荷送入地球同步转移轨道，

or 20 tons into medium Earth orbit.

或者将20吨送入中地球轨道。

But a rocket can only produce so much thrust, 語法

但一枚火箭产生的推力是有限的，

so there's a maximum weight

所以存在一个最大重量，

after which it just won't take off. 短語動詞

超过这个重量它就飞不起来。

If you add too much weight,

如果你增加过多重量，

it won't lift off,

它就无法升空，

so you can't just build bigger and bigger fuel tanks. 語法

所以你不能一直建造越来越大的燃料箱。

This is the tyranny of the rocket equation, 習語

这就是“火箭方程的暴政”，

and it means spaceflight will never become easy.

它意味着太空飞行永远不会变得容易。

But wait, 表達脈絡

但是等等，

it gets worse.

事情会变得更糟。

Getting to space is still not good enough.

进入太空仍不够好。

You're still inside the gravity prison

你仍然处于引力监狱中，

at the edge of space

位于太空边缘，

and will crash back to Earth.

而且还会坠回地球。

Staying in space 語法

留在太空

is much harder than getting there.

比进入太空难得多。

To get to a stable position

要到达一个稳定的位置，

where it can stay for a while,

并能在那里停留一段时间，

the rocket has to reach low Earth orbit. 文化背景

火箭必须进入近地轨道。

To do this,

为此，

you need a lot of kinetic energy,

你需要巨大的动能，

which means going extremely fast.

也就是必须飞得极快。

At an altitude of about 100 km,

在大约100公里的高空，

this is 8 km per second,

这个速度是每秒8公里，

28,000 km per hour,

时速28000公里，

fast enough to travel around Earth 語法

快到足以绕地球一圈，

in 90 minutes.

只需90分钟。

Here,

在这里，

we can use a trick.

我们可以用个把戏。

Instead of flying straight up, 語法

与其垂直向上飞，

we can go sideways.

不如向侧面移动。

Earth is a sphere.

地球是一个球体。

So if you're going sideways fast enough,

所以如果你向侧面移动得足够快，

even though you're falling towards Earth, 語法

即使你正在跌向地球，

the ground will curve away beneath you.

地面会在你下方弯曲并远离你。

So as long as you're above the atmosphere, 語法

所以只要你在大气层之上，

about 100 km up,

也就是大约100公里高，

you'll be able to stay up there in orbit.

你就能留在上面，保持在轨道中。

This is what the ISS does,

国际空间站就是这样做的，

falling around Earth, 文化背景

绕着地球“跌落”，

expending energy from time to time 短語搭配

时不时消耗一点能量

to stay fast enough.

以保持足够快的速度。

If we look at orbits in scale,

如果我们按比例来看轨道，

we see that near Earth orbit is laughably close to Earth.

我们会发现近地轨道其实离地球非常近。

To deploy,

要部署

for example,

比如，

satellites or leave for other planets,

卫星，或者飞往其他行星，

requires another round of energy debt repayment. 短語搭配

就需要偿还新一轮的能量债务。

Getting to orbit

进入轨道

is the most difficult part of spaceflight

是目前太空飞行中

for us right now.

对我们来说最困难的部分。

For example,

例如，

if we want to send a rocket to Mars,

如果我们想向火星发射火箭，

half the energy is necessary just to get into orbit,

一半的能量仅用于进入轨道，

and the other half for the 55 million km to Mars.

另一半用于飞向火星的5500万公里。

Therefore,

因此，

to be as effective as possible, 語法

为了尽可能高效，

rockets aren't built in one giant piece.

火箭不会被建造成一个巨大的整体。

Instead,

相反，

we use multi-stage rockets. 文化背景

我们使用多级火箭。

You don't need to carry an empty fuel tank,

因为不需要携带空的燃料箱，

so rockets drop it.

所以火箭会将其抛弃。

Rockets today shed their boosters and main stage 用詞

如今的火箭会抛弃助推器和主级，

as they ascend,

在它们升空的过程中，

with each successive stage being its own fully contained rocket, 語法

连续的每一级本身就是一枚完全独立的火箭，

complete with its own engine and fuel. 短語搭配

配备着自己的发动机和燃料。

Okay.

好吧。

So this is why getting to space 表達脈絡

这就是为什么进入太空

is hard.

如此困难。

If you feel all of this seems really complicated,

如果你觉得这一切似乎真的很复杂，

don't worry.

别担心。

It's literally rocket science. 習語

这真的就是“火箭科学”。

This video was made possible in part 短語搭配

本视频的部分制作资金

by a sponsorship by Airbus Safran Launchers and Arianespace,

得到了空客赛峰发射器公司和阿丽亚娜空间公司的赞助，

who are getting their new Ariane 6 rocket

他们正准备将新的阿丽亚娜6号火箭

ready to launch

准备好发射

into space in 2020. You can learn more about the rocket here.

并在2020年送入太空。你可以在这里了解更多关于该火箭的信息。

And as always,

和往常一样，

if you like what we do,

如果你喜欢我们的作品，

please consider supporting us on patreon.com.

请考虑在 patreon.com 上支持我们。

It really helps us out a lot.

这对我们帮助很大。

If you're craving more space stuff now,

如果你现在还想看更多有关太空的内容，

here's a playlist for you.

这里的播放列表适合你。