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

如何向遠在天邊的宇宙學習 - 林亨利

譯者: Ying Wang

Here are some images of clusters of galaxies.

螢幕上顯示的是 多簇聚集於宇宙中的銀河星團

They're exactly what they sound like.

它們聽起來就跟你眼前看到的一樣

They are these huge collections of galaxies,

是多群為數龐大的銀河系所組成

bound together by their mutual gravity.

彼此藉由相對引力互相牽引著

So most of the points that you see on the screen

所以你們在螢幕上看到的每個光點

are not individual stars,

都不只是單單一顆發光的恆星

but collections of stars, or galaxies.

而是恆星群，或是銀河星群

Now, by showing you some of these images,

現在，藉由這些影像分享

I hope that you will quickly see that

我希望你們能很快注意到

galaxy clusters are these beautiful objects,

這些銀河星群不僅美麗

but more than that,

但其更深層的意義是

I think galaxy clusters are mysterious,

這些銀河星團 不為人知且神秘的一面

they are surprising,

它們美得令人驚艷

and they're useful.

卻也有它的存在價值

Useful as the universe's most massive laboratories.

整個宇宙就像浩瀚無窮的實驗室

And as laboratories, to describe galaxy clusters

就如同所有實驗室，想要理解個銀河星團

is to describe the experiments

就如同準備實驗過成一樣

that you can do with them.

有異曲同工之妙

And I think there are four major types,

就我個人而言，可分為四種型式

and the first type that I want to describe

第一類型便是

is probing the very big.

繼續探索無窮宇宙

So, how big?

所以，宇宙到底有多大？

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

我們來看看這其中特別的銀河星團群

It is so massive that the light passing through it

這星團簇大到，每當光經過星團

is being bent, it's being distorted

就會轉彎，光會被扭曲

by the extreme gravity of this cluster.

在這星團極端異常的重力下

And, in fact, if you look very carefully

假如你看得夠仔細的話

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

你會看到類似環型的光圍繞著星團

Now, to give you a number,

現在，我們來談談實際數據

this particular galaxy cluster

這個特別的銀河星團

has a mass of over one million billion suns.

有將近十兆顆太陽的質量

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

銀河星團竟然可以 大到如此令人吃驚的地步

But more than their mass,

除了探討質量之外

they have this additional feature.

它們還有其他特質

They are essentially isolated systems,

基本上它們已經 型成獨立的星團系統

so if we like, we can think of them

因此我們可以把這些銀河星團想成

as a scaled-down version of the entire universe.

整個宇宙的縮小版

And many of the questions that we might have

很多類似的問題

about the universe at large scales,

比如說探討宇宙規模大小

such as, how does gravity work?

或者是，重力如何運作...等問題

might be answered by studying these systems.

都可藉由研究這些銀河星團得到解答

So that was very big.

這就是我所說的「向無窮盡探索」

The second things is very hot.

第二個實驗論點是─「找非常熱點」

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

假如我擷取一張銀河星團的影像

and I subtract away all of the starlight,

並將所有星光的色澤用電腦抽掉

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

影像會變成像這團藍色巨大 看起來又濕又厚的一團雲狀物

This is in false color.

這顏色已失真

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

大家看到的其實是X光線的殘影

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

問題來了，如果把所有光源都抽掉之後

what is emitting this light?

是哪種能源形成這背後的另一道光影

The answer is hot gas,

答案是「帶有熱源的氣體」

million-degree gas --

溫度高達一百萬度的氣體

in fact, it's plasma.

這種氣體被稱為 宇宙中的「等離子氣體」

And the reason why it's so hot

此氣體之所以會如此熱的原因

goes back to the previous slide.

可以追述到先前的投影片

The extreme gravity of these systems

巨大銀河星團中極端的重力

is accelerating particles of gas to great speeds,

會加速氣體中原子的運動速率

and great speeds means great temperatures.

速度越會產生的熱能會越大

So this is the main idea,

這便是主旨所在

but science is a rough draft.

不過科學講的都是大概的草圖

There are many basic properties about this plasma

等離子氣體富有某些特性

that still confuse us,

至今依然無解

still puzzle us,

令科學家們摸不著頭緒

and still push our understanding

也在挑戰我們既有對宇宙的認知

of the physics of the very hot.

以及物理學上對熱能的理解

Third thing: probing the very small.

第三點我想闡述的是：「探索最小值」

Now, to explain this, I need to tell you

現在，在解釋這論點前，我必須告訴你

a very disturbing fact.

一個令人不安的事實

Most of the universe's matter

這宇宙絕大部分 的物質組成最小粒子

is not made up of atoms.

並非原子

You were lied to.

你們都被騙了

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

這宇宙絕大部分的物質是由一種 非常、非常神祕的

which we call dark matter.

被稱為「黑色物質(dark matter)」所組成

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

黑物質不喜歡跟外界有太多互動

except through gravity,

直到遇上了重力

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

當然我們必須對此 進行更深入的研究

If you're a particle physicist,

假如你是個粒子物理學家

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

你想知道當所有東西撞擊在一起 會發生甚麼事

And dark matter is no exception.

黑物質也不例外

Well, how do we do this?

很好，那我們如何進行實驗呢？

To answer that question,

回答這問題之前

I'm going to have to ask another one,

我得再問你們另外一個問題

which is, what happens when galaxy clusters collide?

也就是，為甚麼 銀河星團會彼此產生撞擊？

Here is an image.

這裡有張影像給各位提示

Since galaxy clusters are representative

當我們把銀河星團視為具代表性的

slices of the universe, scaled-down versions.

整個宇宙的小縮影

They are mostly made up of dark matter,

它們大部分也都由黑物質組成

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

這也就是你看到 這到接近藍紫色的團狀物

The red represents the hot gas,

紅色的部分代表熱氣

and, of course, you can see many galaxies.

當然你可以看到許多銀河聚集在一起

What's happened is a particle accelerator

會加速粒子間的運動速度

at a huge, huge scale.

以一種極大的規模改變速率

And this is very important,

這點非常重要

because what it means is that very, very small

因為這非常、非常小的物質

effects that might be difficult to detect in the lab,

影響所及之處 可能是在實驗室中無法被察覺出來

might be compounded and compounded

我們可能經過層層組合

into something that we could possibly observe in nature.

把這黑色物質組合至 肉眼能辨識的程度

So, it's very funny.

這實在很有趣

The reason why galaxy clusters

銀河星團之所以可以教導我們

can teach us about dark matter,

有關黑色物質的原因

the reason why galaxy clusters

銀河星團之所以可以教導我們

can teach us about the physics of the very small,

物理世界中的最小物質的原因

is precisely because they are so very big.

正是因為銀河星團夠大

Fourth thing: the physics of the very strange.

第四個論點是： 「探索物理學中最奇特的未知」

Certainly what I've said so far is crazy.

到目前為止我談論的一切 聽起來確實瘋狂

Okay, if there's anything stranger

很好，最難以理解的部分

I think it has to be dark energy.

我想應該是黑色能量這部分

If I throw a ball into the air,

假如我拋一顆球進空中

I expect it to go up.

我期待它往空中運行

What I don't expect is that it go up

出乎我意料之外的是

at an ever-increasing rate.

它往上運行的速度不斷增加

Similarly, cosmologists understand why

同理可證，宇宙學家便理解

the universe is expanding.

為何整個宇宙一直在擴張

They don't understand why it's expanding

他們不懂為什麼 整個宇宙的擴張速度

at an ever-increasing rate.

一直在增加

They give the cause of this

他們把這個莫名始擴張速度

accelerated expansion a name,

加快的力量命名為

and they call it dark energy.

「黑色能量」

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

於是，再一次的，我們想要研究更多

So, one particular question that we have is,

我們會想問的最特別的問題便是

how does dark energy affect the universe

黑色能量如何以最大的規模

at the largest scales?

影響整個宇宙

Depending on how strong it is,

這得視黑色能量的力道有多強

maybe structure forms faster or slower.

或許結構行成的速度快或慢

Well, the problem with the large-scale structure

針對這種大規模結構的研究難題是

of the universe is that it's horribly complicated.

宇宙的所有現象極其複雜

Here is a computer simulation.

這邊我們為各位展示電腦模擬

And we need a way to simplify it.

我們需要找方法試著簡化它

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

我想用一個類比式的比喻 來敘述這個問題

If I want to understand the sinking of the Titanic,

假設我想了解 鐵達尼號是如何沈入海

the most important thing to do

最首要作的事情

is not to model the little positions

不會是聚焦在 船身的碎片或其他小細節

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

來判斷沈船的主因

The most important thing to do is

反而最重要的是

to track the two biggest parts.

把船身分為兩段來探討沈船的原因

Similarly, I can learn a lot about the universe

同樣地，用這樣的方式 我可以從宇宙中

at the largest scales

學到很多宏觀性的概念

by tracking its biggest pieces

藉由追蹤宇宙中的大規則

and those biggest pieces are clusters of galaxies.

銀河星團便是 這些大規則中的一部分

So, as I come to a close,

因此我這以如此斷然下結論

you might feel slightly cheated.

你可能覺得這有點像作弊

I mean, I began by talking about

我的意思是，當我開始談論

how galaxy clusters are useful,

研究銀河星團有甚麼實質的好處

and I've given some reasons,

並分享其它好處的原因

but what is their use really?

但它們到底有甚麼用處？

Well, to answer this,

在回答這個問題之前

I want to give you a quote by Henry Ford

我想要跟你們引用亨利‧福特的一段話

when he was asked about cars.

每當他被問到有關車子的問題時

He had this to say:

他都會說上這麼一段話

"If I had asked people what they wanted,

「當我問其他人他們想要甚麼？」

they would have said faster horses."

「他們總會回答，他們想要更快的馬。」

Today, we as a society are faced

今日，我們的社會面臨

with many, many difficult problems.

為數眾多且層出不窮的難題

And the solutions to these problems are not obvious.

而且這些問題的解答 皆尚未明朗化

They are not faster horses.

這些問題並非大眾所期待的快馬

They will require an enormous amount of

這些問題需要大量的

scientific ingenuity.

科學性的創造力

So, yes, we need to focus,

是的，沒錯，我們必須要專注

yes, we need to concentrate,

沒錯，我們必須要專注

but we also need to remember that

但同時我們也該記得

innovation, ingenuity, inspiration --

革新、創造力、靈感...

these things come

這些皆來自於

when we broaden our field of vision

我們拓展自己的視野

when we step back

當我們退後一步看全局

when we zoom out.

當我們縮焦觀看全局

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

我想沒有比研究我們現有宇宙現象

by studying the universe around us. Thanks.

來得更適合的方式。 謝謝大家

(Applause)

(掌聲)