What we can learn from galaxies far, far away - Henry Lin

从遥远的星系中我们能学到什么 - 亨利·林

翻译人员: Qingqing Mao 校对人员: Qiwen Lu

Here are some images of clusters of galaxies.

这里有一些星系团的图片。

They're exactly what they sound like.

正如它们的名字，

They are these huge collections of galaxies,

它们是成团的星系，

bound together by their mutual gravity.

依靠互相之间的引力集合在一起。

So most of the points that you see on the screen

你在屏幕上看到的大部分亮点

are not individual stars,

都不是一颗颗的恒星，

but collections of stars, or galaxies.

而是星系——成群的恒星。

Now, by showing you some of these images,

看着这些图片，

I hope that you will quickly see that

我希望你很快能看出

galaxy clusters are these beautiful objects,

星系团非常地漂亮。

but more than that,

然而更重要的是，

I think galaxy clusters are mysterious,

我认为星系团是神秘的，

they are surprising,

令人诧异的，

and they're useful.

而且是有用的。

Useful as the universe's most massive laboratories.

它们可以用作宇宙中质量最大的实验室。

And as laboratories, to describe galaxy clusters

作为实验室来说，描述星系团

is to describe the experiments

即是描述

that you can do with them.

我们可以用它们来做些什么实验。

And I think there are four major types,

我认为有四类主要的实验。

and the first type that I want to describe

我想说的第一种是

is probing the very big.

探测极大。

So, how big?

多大？

Well, here is an image of a particular galaxy cluster.

这里有一个星系团的图片。

It is so massive that the light passing through it

它的质量如此之大，

is being bent, it's being distorted

以至于穿过它的光线会被弯折，

by the extreme gravity of this cluster.

光线被这个星系团的极大引力所扭曲。

And, in fact, if you look very carefully

事实上，如果你仔细看

you'll be able to see rings around this cluster.

你能看到环绕着星系团的环状影像。

Now, to give you a number,

用数字来说，

this particular galaxy cluster

这个星系团的质量

has a mass of over one million billion suns.

超过一千万亿个太阳的质量。

It's just mind-boggling how massive these systems can get.

这些系统的质量之大令人难以想象。

But more than their mass,

但是不仅是它们的质量，

they have this additional feature.

它们还有其他特征。

They are essentially isolated systems,

它们本质上是孤立的系统。

so if we like, we can think of them

我们可以把它们想象为

as a scaled-down version of the entire universe.

一个缩小版的宇宙。

And many of the questions that we might have

我们对于宇宙在大尺度上的

about the universe at large scales,

很多问题

such as, how does gravity work?

——比如说，引力如何工作？——

might be answered by studying these systems.

都有可能通过研究这些系统来得到解答。

So that was very big.

以上是关于极大。

The second things is very hot.

第二点是极热。

Okay, if I take an image of a galaxy cluster,

如果我们拍摄一个星系团的照片，

and I subtract away all of the starlight,

然后我把所有恒星光都移除，

what I'm left with is this big, blue blob.

剩下的是这么一团蓝色。

This is in false color.

这个是假彩色影像。

It's actually X-ray light that we're seeing.

我们所看到的其实是X光影像。

And the question is, if it's not galaxies,

问题是，如果不是星系，

what is emitting this light?

那这些光是由什么所发出的呢？

The answer is hot gas,

答案是炙热的气体，

million-degree gas --

百万度的气体。

in fact, it's plasma.

实际上，那是等离子体。

And the reason why it's so hot

它们如此炙热的原因

goes back to the previous slide.

需要从上一张幻灯片里找。

The extreme gravity of these systems

这些系统中极强的引力

is accelerating particles of gas to great speeds,

极大地加速了气体粒子，

and great speeds means great temperatures.

高速意味着高温。

So this is the main idea,

这是主要的想法，

but science is a rough draft.

但是其中的科学还是一个草稿。

There are many basic properties about this plasma

这些等离子的很多基本性质

that still confuse us,

依然困扰着我们，

still puzzle us,

依然是难题，

and still push our understanding

依然推动着我们

of the physics of the very hot.

对于极高温物理的认识。

Third thing: probing the very small.

第三点：探测极小。

Now, to explain this, I need to tell you

为了解释这一点，我需要告诉你们

a very disturbing fact.

一个令人不安的事实。

Most of the universe's matter

宇宙中的大部分物质

is not made up of atoms.

都不是原子构成的。

You were lied to.

你们都被骗了。

Most of it is made up of something very, very mysterious,

大部分物质都是由非常神秘得东西构成的，

which we call dark matter.

我们称其为暗物质。

Dark matter is something that doesn't like to interact very much,

暗物质很不喜欢相互作用，

except through gravity,

除了引力作用。

and of course we would like to learn more about it.

当然我们想知道更多。

If you're a particle physicist,

如果你是一个粒子物理学家，

you want to know what happens when we smash things together.

你想知道当我们把东西对撞在一起时会发生什么。

And dark matter is no exception.

暗物质也不例外。

Well, how do we do this?

那么我们要如何做？

To answer that question,

为了回答这个问题，

I'm going to have to ask another one,

我先要提另一个问题：

which is, what happens when galaxy clusters collide?

星系团对撞会发生什么？

Here is an image.

这里有一幅图片。

Since galaxy clusters are representative

由于星系团是宇宙的一个缩影，

slices of the universe, scaled-down versions.

一个缩小版的宇宙。

They are mostly made up of dark matter,

它们大部分是由暗物质构成的，

and that's what you see in this bluish purple.

这是你们在图中所见的蓝紫色部分。

The red represents the hot gas,

红色部分代表了高温气体。

and, of course, you can see many galaxies.

当然，你还能看到很多星系。

What's happened is a particle accelerator

这里所发生的

at a huge, huge scale.

是一个在超大尺度上的“粒子加速器”。

And this is very important,

这一点非常重要，

because what it means is that very, very small

因为这意味着，

effects that might be difficult to detect in the lab,

实验室里很难探测到的一些极小的效应

might be compounded and compounded

可能不断累积到了

into something that we could possibly observe in nature.

我们可以观测到的东西里。

So, it's very funny.

这个非常有趣。

The reason why galaxy clusters

为什么星系团

can teach us about dark matter,

能告诉我们暗物质的知识？

the reason why galaxy clusters

为什么星系团

can teach us about the physics of the very small,

能告诉我们极小尺度上的物理？

is precisely because they are so very big.

正是因为它们如此巨大。

Fourth thing: the physics of the very strange.

第四种：极其怪异的物理学。

Certainly what I've said so far is crazy.

我刚才所说的已然很疯狂了。

Okay, if there's anything stranger

要是还有更奇怪的东西，

I think it has to be dark energy.

我认为那一定是暗能量。

If I throw a ball into the air,

如果我把一个球扔向空中，

I expect it to go up.

我预料它会向上走，

What I don't expect is that it go up

但是我不会期待

at an ever-increasing rate.

它向上走得越来越快。

Similarly, cosmologists understand why

类似地，宇宙学家明白

the universe is expanding.

为什么宇宙在膨胀，

They don't understand why it's expanding

但是他们不明白

at an ever-increasing rate.

为什么宇宙膨胀会加速。

They give the cause of this

他们给引起这种加速膨胀的原因

accelerated expansion a name,

取了一个名字，

and they call it dark energy.

称其为暗能量。

And, again, we want to learn more about it.

同样，我们想要知道更多。

So, one particular question that we have is,

一个问题是，

how does dark energy affect the universe

暗能量如何

at the largest scales?

在大尺度上影响宇宙？

Depending on how strong it is,

取决于暗能量的强度，

maybe structure forms faster or slower.

结构可能会形成得更快或更慢。

Well, the problem with the large-scale structure

问题是，宇宙的大尺度结构

of the universe is that it's horribly complicated.

是非常复杂的。

Here is a computer simulation.

这里有一个计算机模拟。

And we need a way to simplify it.

我们需要一个方法来简化它。

Well, I like to think about this using an analogy.

我喜欢用一个类比来思考这个问题。

If I want to understand the sinking of the Titanic,

如果我想要了解泰坦尼克号的沉没过程，

the most important thing to do

最重要的事情

is not to model the little positions

不是去找出船体的

of every single little piece of the boat that broke off.

每一块小碎片的位置。

The most important thing to do is

最重要的是

to track the two biggest parts.

追踪最大的那两块。

Similarly, I can learn a lot about the universe

同样，我可以

at the largest scales

通过追踪宇宙中最大的碎片

by tracking its biggest pieces

来学到大尺度上的宇宙的很多知识。

and those biggest pieces are clusters of galaxies.

这些最大的碎片就是星系团。

So, as I come to a close,

随着我快要讲完了，

you might feel slightly cheated.

你可能略有上当受骗的感觉。

I mean, I began by talking about

我的意思是，在一开始

how galaxy clusters are useful,

我说星系团是有用的，

and I've given some reasons,

而且我已经给出了一些理由。

but what is their use really?

但是他们的用处到底是什么？

Well, to answer this,

为了回答这个，

I want to give you a quote by Henry Ford

我想引用亨利·福特的一句话。

when he was asked about cars.

当他被问及汽车的时候，

He had this to say:

他曾说过：

"If I had asked people what they wanted,

“如果我当年去问顾客他们想要什么，

they would have said faster horses."

他们会说：“更快的马”。”

Today, we as a society are faced

今日，我们社会

with many, many difficult problems.

面临着很多很多的难题。

And the solutions to these problems are not obvious.

这些问题并无明显的答案。

They are not faster horses.

答案不是更快的马。

They will require an enormous amount of

解答它们将会需要大量

scientific ingenuity.

科学的巧思。

So, yes, we need to focus,

所以，我们需要集中，

yes, we need to concentrate,

我们需要专注，

but we also need to remember that

但是我们也需要记得，

innovation, ingenuity, inspiration --

创新、巧思、灵感

these things come

这些东西的出现

when we broaden our field of vision

需要我们开拓视野，

when we step back

需要我们重新审视，

when we zoom out.

需要我们纵观全局。

And I can't think of a better way to do this than

而研究我们周围的宇宙

by studying the universe around us. Thanks.

正是最好的方法。谢谢。

(Applause)

（掌声）