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

譯者: Hao Li 審譯者: 杏儀 歐陽

Here are some images of clusters of galaxies.

這是一些星團的照片。

They're exactly what they sound like.

它們貌如其名，

They are these huge collections of galaxies,

是多個星系的龐大集合。

bound together by their mutual gravity.

它們通過相互的引力而吸引在一起。

So most of the points that you see on the screen

因此，你在屏幕上看到的大部分的點

are not individual stars,

並非是單獨的恆星，

but collections of stars, or galaxies.

而是一系列恆星， 或者是我們所稱之星系。

Now, by showing you some of these images,

現在看了​​這些圖片之後

I hope that you will quickly see that

我希望你已經發現，

galaxy clusters are these beautiful objects,

星團是多麼美麗的物體，

but more than that,

但絕非僅限於此

I think galaxy clusters are mysterious,

我認為星團神秘莫測、

they are surprising,

令人嘆為觀止，

and they're useful.

並且具有巨大使用價值。

Useful as the universe's most massive laboratories.

其價值，就如同是 宇宙裡規模最大的實驗室。

And as laboratories, to describe galaxy clusters

要描述星團，就跟評估一個實驗室一樣，

要去描述這個實驗室 能讓你做的實驗。

is to describe the experiments

that you can do with them.

And I think there are four major types,

我認為這包括四種主要類型：

and the first type that I want to describe

我想描述的第一類

is probing the very big.

是探測「極大」。

So, how big?

到底有多大？

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

這是某個星團的照片。

It is so massive that the light passing through it

它的質量非常大， 以至於光在經過的時候，

is being bent, it's being distorted

也會由於其引力的作用，

by the extreme gravity of this cluster.

而發生彎曲。

And, in fact, if you look very carefully

事實上，如果你仔細看，

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

你能夠看到這個星團周圍的光環。

Now, to give you a number,

如果要給出一個具體數字，

this particular galaxy cluster

這個星團的質量

has a mass of over one million billion suns.

有超過10的15次方個太陽那麼大。

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

這些系統質量之巨大 簡直讓人瞠目結舌。

But more than their mass,

但除了質量巨大這個特點之外，

they have this additional feature.

它們還有其他特殊之處。

They are essentially isolated systems,

這些星系基本上可以是孤立的系統。

so if we like, we can think of them

如果願意的話，我們可以將它們

as a scaled-down version of the entire universe.

想像為整個宇宙的縮小版。

And many of the questions that we might have

我們對於宏觀的宇宙

about the universe at large scales,

還存在很多疑問。

such as, how does gravity work?

比如，引力是怎麼起作用的？

might be answered by studying these systems.

這些問題可能可以通過 研究這些系統來找到答案。

So that was very big.

這，就是「極大」。

The second things is very hot.

第二個，是「極熱」。

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

好的，如果我拿出一幅星團的照片，

and I subtract away all of the starlight,

去掉其中所有的星光，

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

剩下的，只是這個巨大的藍色斑塊。

This is in false color.

當然，這些顏色都不是真的。

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

我們實際看到的是X射線。

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

但問題是，假如發出X射線的，不是這些星系，

what is emitting this light?

又是什麼呢？

The answer is hot gas,

答案是高溫氣體，

million-degree gas --

一百萬度的氣體。

in fact, it's plasma.

事實上，這些氣體是等離子。

And the reason why it's so hot

而它們的溫度如此之高的原因，

goes back to the previous slide.

在於前一張幻燈片。

The extreme gravity of these systems

這些系統的超強引力

is accelerating particles of gas to great speeds,

將氣體粒子加速到非常高的速度，

and great speeds means great temperatures.

而高速則意味著高溫。

So this is the main idea,

這是主要的推測，

but science is a rough draft.

但是科學畢竟是一副草圖。

There are many basic properties about this plasma

其中尚存在等離子氣體的很多基本特徵，

that still confuse us,

讓我們無法解釋，

still puzzle us,

仍然是個謎，

and still push our understanding

仍需不斷增加我們對超高溫物理的理解。

of the physics of the very hot.

Third thing: probing the very small.

第三個是：研究「極小」。

Now, to explain this, I need to tell you

要解釋這個類型，我要向大家說

a very disturbing fact.

一件讓人困擾的事實。

Most of the universe's matter

宇宙中的大部分物質

is not made up of atoms.

並非由原子構成。

You were lied to.

你們以前都被騙了。

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

宇宙的大部分物質是由一種 非常神秘的物質組成，

which we call dark matter.

我們稱之為暗物質。

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

暗物質並不喜歡與周圍物質反應，

除非是在有引力的情況下。

except through gravity,

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

當然，我們也希望更多地了解暗物質。

If you're a particle physicist,

假設你是粒子物理學家，

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

你會想知道，物體撞擊時，會出現什麼情況。

And dark matter is no exception.

暗物質也不例外。

Well, how do we do this?

那麼，我們該怎麼做呢？

To answer that question,

為了回答這個問題，

I'm going to have to ask another one,

我們不得不提出另一個問題。

which is, what happens when galaxy clusters collide?

那就是：要是星團發生碰撞，會有什麼結果？

Here is an image.

這是一張照片。

Since galaxy clusters are representative

既然我們可以把星團

slices of the universe, scaled-down versions.

看作縮小版的宇宙。

They are mostly made up of dark matter,

星團大部分也是由暗物質構成，

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

就是你所看到的藍紫色的那些。

The red represents the hot gas,

紅色代表高溫氣體，

and, of course, you can see many galaxies.

當然，你可以看到很多星系。

What's happened is a particle accelerator

這些就相當於

at a huge, huge scale.

一部巨型粒子加速器。

And this is very important,

這很重要，

because what it means is that very, very small

因為這意味著

那些難以在實驗室裡 檢測到的細微現象

effects that might be difficult to detect in the lab,

might be compounded and compounded

可能由於基數不斷地疊加，

into something that we could possibly observe in nature.

而使我們於自然界觀測得到。

So, it's very funny.

相當有趣。

The reason why galaxy clusters

為什麼星團可以 教我們暗物質的知識？

can teach us about dark matter,

the reason why galaxy clusters

為什麼星團可以指導我們 「極小」物質之物理？

can teach us about the physics of the very small,

is precisely because they are so very big.

這正正是因為星團相當巨型。

Fourth thing: the physics of the very strange.

第四個：「奇異」之物的物理。

Certainly what I've said so far is crazy.

我剛才說的聽上去已經很瘋狂了，

Okay, if there's anything stranger

但是，如果有比那些更瘋狂的，

I think it has to be dark energy.

我認為就是暗能量了。

If I throw a ball into the air,

我把一個球扔向空中，

I expect it to go up.

我會預計它將上升，

What I don't expect is that it go up

但是我不會想到

at an ever-increasing rate.

球會以持續加速度上升。

Similarly, cosmologists understand why

同樣道理，宇宙學家們理解

the universe is expanding.

為什麼宇宙在膨脹。

They don't understand why it's expanding

但他們不理解的是

at an ever-increasing rate.

為什麼宇宙膨脹的速度持續加快。

They give the cause of this

他們給引起加速膨脹的原因

accelerated expansion a name,

取了個名字，

and they call it dark energy.

叫做暗能量。

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

同樣，我們希望更多地了解暗能量。

So, one particular question that we have is,

其中一個問題是

how does dark energy affect the universe

暗能量是如何在 最大程度上影響宇宙？

at the largest scales?

Depending on how strong it is,

這取決於能量的強弱，

maybe structure forms faster or slower.

或者結構的形成的快慢。

Well, the problem with the large-scale structure

但是這個擁有如此大型結構的 宇宙所存在的問題是

of the universe is that it's horribly complicated.

宇宙大得恐怖。

Here is a computer simulation.

這是一張電腦模擬圖。

And we need a way to simplify it.

我們需要想方法簡化它。

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

我喜歡用類比的方式來看待它。

If I want to understand the sinking of the Titanic,

如果我想理解鐵達尼號沉沒的過程，

the most important thing to do

最重要的，

is not to model the little positions

不是去模擬船身所有碎片的位置。

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

The most important thing to do is

最重要的是，

to track the two biggest parts.

追踪船體最大的兩個斷裂快的位置。

Similarly, I can learn a lot about the universe

同樣，我可以通過追踪

at the largest scales

宇宙中最大的部件，

by tracking its biggest pieces

對宇宙有最大程度的了解，

and those biggest pieces are clusters of galaxies.

而最大的部件就是這些星團。

So, as I come to a close,

現在我即將結尾。

you might feel slightly cheated.

大家可能覺得有點上當了。

I mean, I began by talking about

我的意思是，

how galaxy clusters are useful,

一開始我談到星團具有哪些價值。

and I've given some reasons,

我也給了一些理由。

but what is their use really?

但是他們真正的用處在哪裡呢？

Well, to answer this,

為了回答這個

I want to give you a quote by Henry Ford

我要引用亨利·福特的一句話。

when he was asked about cars.

當有人問他關於汽車的事情時，

He had this to say:

他這樣說：

"If I had asked people what they wanted,

「如果我之前問人們他們想要什麼，

they would have said faster horses."

他們只會回答說，更快的馬。」

Today, we as a society are faced

如今，我們社會面臨很多、很多棘手的問題。

with many, many difficult problems.

And the solutions to these problems are not obvious.

這些問題的解決之道並非顯而易見。

They are not faster horses.

辦法不是「更快的馬」。

They will require an enormous amount of

而是需要更多的科學智慧。

scientific ingenuity.

So, yes, we need to focus,

所以沒錯，我們需要有針對性，

yes, we need to concentrate,

我們需要專心，

but we also need to remember that

但我們也要謹記，

innovation, ingenuity, inspiration --

創新、創造力和靈感，

these things come

當我們開闊眼界時，

when we broaden our field of vision

當我們退後一步時，

when we step back

當我們聚焦問題時，

when we zoom out.

這三樣——創新、創造力和靈感——自會來到。

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

要做到以上，恐怕除了 研究學習我們周圍的宇宙，

by studying the universe around us. Thanks.

就別無其他更好的辦法了。謝謝。

(Applause)

（掌聲）