Dark matter: The matter we can't see - James Gillies

暗物質: 我們看不見的物質 - James Gillies

Translator: Andrea McDonough Reviewer: Jessica Ruby

譯者: Jephian Lin 審譯者: Geoff Chen

The ancient Greeks had a great idea:

古代希臘人有一個偉大的想法：

The universe is simple.

宇宙是簡單的。

In their minds,

在他們心中，

all you needed to make it were four elements:

要建構宇宙只須要四種元素：

earth,

土、

air,

fire,

空氣、

火、

and water.

還有水。

As theories go, it's a beautiful one.

就像它的理論一樣， 這是美麗的。

It has simplicity and elegance.

既簡單、又優雅。

It says that by combining

理論中認為

the four basic elements in different ways,

藉由四種元素的不同組合，

you could produce all the wonderful diversity of the universe.

可以產生宇宙萬物。

Earth and fire, for example,

比如說土加火，

give you things that are dry.

就會有一些乾的東西。

Air and water, things that are wet.

而空氣加水，就會得到濕的東西。

But as theories go, it had a problem.

但依照這理論， 會有一個問題。

It didn't predict anything that could be measured,

它沒辦法預測出任何 可以測量的事物，

and measurement is the basis of experimental science.

而測量又是實驗科學的基礎。

Worse still, the theory was wrong.

更糟的是，這理論是錯的。

But the Greeks were great scientists of the mind

但希臘人仍是 思想上偉大的科學家，

and in the 5th century B.C.,

在西元前 5 世紀，

Leucippus of Miletus came up

米勒都的留基伯（Leucippus of Miletus）

with one of the most enduring scientific ideas ever.

提出有史以來 最經得起考驗的科學思想之一。

Everything we see is made up

我們看到的每樣東西

of tiny, indivisible bits of stuff called atoms.

都由微小、看不見的東西組成， 這東西稱作原子。

This theory is simple and elegant,

這個理論既簡單又優雅，

and it has the advantage

而它超越 土、空氣、水、火的理論

over the earth, air, fire, and water theory

而它超越 土、空氣、水、火的理論

of being right.

更接近事實。

Centuries of scientific thought and experimentation

幾世紀以來的 科學思想及實驗

have established that the real elements,

證實了實體的物質，

things like hydrogen,

像是氫氣、

carbon,

and iron,

碳、

還有鐵，

can be broken down into atoms.

都可以分解成原子。

In Leucippus's theory, the atom is the smallest,

在留基伯的理論中，原子是最小的、

indivisible bit of stuff that's still recognizable

看不見的物質， 但仍然可以作區分，

as hydrogen,

像是氫原子、

carbon,

碳原子、

or iron.

鐵原子。

The only thing wrong with Leucippus's idea

留基伯的想法裡， 唯一有問題的是

is that atoms are, in fact, divisible.

事實上原子也還可以再細分。

Furthermore, his atoms idea turns out

而且，他的原子說最終

to explain just a small part

只解釋了宇宙組成 的一小部份。

of what the universe is made of.

只解釋了宇宙組成 的一小部份。

What appears to be the ordinary stuff of the universe

平常所見到的物質， 實際上在宇宙中

is, in fact, quite rare.

非常稀少。

Leucippus's atoms, and the things they're made of,

留基伯討論的原子、 還有它們組成的物質，

actually make up only about 5%

事實上只佔了 我們知道的物質

of what we know to be there.

的大約 5%。

Physicists know the rest of the universe,

物理學家認為其餘的宇宙，

95% of it,

就是那 95%，

as the dark universe,

是暗宇宙，

made of dark matter and dark energy.

由暗物質和暗能量組成。

How do we know this?

我們怎麼知道？

Well, we know because we look at things

嗯，我們會知道是因為

and we see them.

我們有觀察到。

That might seem rather simplistic,

這聽起來蠻簡單的，

but it's actually quite profound.

但實際上有點複雜。

All the stuff that's made of atoms is visible.

所有原子組成的物質 是看得見的。

Light bounces off it, and we can see it.

它會反射光線， 然後我們就看得到。

When we look out into space,

當我們觀察宇宙時，

we see stars and galaxies.

我們會看到星星和銀河。

Some of them, like the one we live in,

有些就像我們居住的地方一樣，

are beautiful, spiral shapes, spinning gracefully through space.

很美麗、有螺旋的結構、 優雅地在太空中旋轉。

When scientists first measured the motion

當科學家在 1930 年代 第一次

of groups of galaxies in the 1930's

觀測一群星系時，

and weighed the amount of matter they contained,

並同時估算它們的質量，

they were in for a surprise.

科學家們大為震驚。

They found that there's not enough visible stuff

他們發現 並沒有足夠的可見物質

in those groups to hold them together.

讓這些星系群 靠在一起。

Later measurements of individual galaxies

之後對單獨星系的觀察

confirmed this puzzling result.

證實了這個謎樣的結果。

There's simply not enough visible stuff in galaxies

星系裡就是沒有足夠的 可見物質

to provide enough gravity to hold them together.

來提供足夠的重力 讓它們靠在一起。

From what we can see,

從我們的觀測之中，

they ought to fly apart, but they don't.

它們應該向外飛走， 但並沒有。

So there must be stuff there

所以一定有什麼東西

that we can't see.

是我們看不到的。

We call that stuff dark matter.

我們把這東西稱作 暗物質。

The best evidence for dark matter today

現今關於暗物質 最有力的證據

comes from measurements of something

來自於對於一種叫作

called the cosmic microwave background,

宇宙背景微波輻射的觀測，

the afterglow of the Big Bang,

也就是大爆炸後 留下的餘光，

but that's another story.

但這是另一段故事了。

All of the evidence we have

所有我們掌握的證據

says that dark matter is there

都說明了暗物質的存在，

and it accounts for much of the stuff

而在天空中

in those beautiful spiral galaxies

那些美麗的螺旋星系中

that fill the heavens.

它佔據了大部份的質量。

So where does that leave us?

這告訴我們什麼？

We've long known that the heavens

長久以來我們知道

do not revolve around us

天空並不是繞著我們旋轉，

and that we're residents of a fairly ordinary planet,

而我們只是 一顆平凡行星上的居民，

orbiting a fairly ordinary star,

繞著一顆平凡的恆星、

in the spiral arm of a fairly ordinary galaxy.

座落在一個平凡星系的螺旋臂上。

The discovery of dark matter took us

暗物質的發現 帶領我們

one step further away from the center of things.

更進一步了解 物質的本質。

It told us that the stuff we're made of

這告訴我們 組成我們的物質

is only a small fraction of what makes up the universe.

只是組成宇宙的物質 其中的一小部份。

But there was more to come.

但是不只這樣。

Early this century,

在這世紀初，

scientists studying the outer reaches of the universe

研究宇宙外部的科學家

confirmed that not only is everything moving apart

證實了不只是

from everything else,

物質與物質之間不斷遠離，

as you would expect in a universe

就如同你想像

that began in hot, dense big bang,

宇宙誕生於 高溫、高密度的大爆炸一樣，

but that the universe's expansion

這宇宙向外的擴張

also seems to be accelerating.

似乎正在加速。

What's that about?

這代表什麼？

Either there is some kind of energy

要不就是有某種能量

pushing this acceleration,

促成這樣的加速，

just like you provide energy to accelerate a car,

就像是你提供能量 讓一輛車加速一樣；

or gravity does not behave exactly as we think.

要不就是重力 和我們想的不完全一樣。

Most scientists think it's the former,

大多數科學家相信 前者是對的，

that there's some kind of energy driving the acceleration,

也就是有某種能量 促成這種加速，

and they called it <i>dark energy</i>.

他們把它叫作 暗物質。

Today's best measurements allow us to work out

現今最好的觀測 讓我們可以計算

just how much of the universe is dark.

宇宙有多少部份 是屬於暗的。

It looks as if dark energy makes up

看似暗能量佔了

about 68% of the universe

大約 68% 的宇宙，

and dark matter about 27%,

而暗物質佔了 27%，

leaving just 5% for us

剩的 5% 才是

and everything else we can actually see.

所有其它我們看得到的東西。

So what's the dark stuff made of?

所以這些黑暗的東西 是由什麼組成的？

We don't know,

but there's one theory, called <i>supersymmetry</i>,

我們並不知道，

但有一個理論， 叫作「超對稱理論」，

that could explain some of it.

可以解釋一些。

Supersymmetry, or SUSY for short,

超對稱（supersymmetry）， 或簡稱 SUSY，

predicts a whole range of new particles,

預測了一系列新的粒子，

some of which could make up the dark matter.

其中的一些 可以組成暗物質。

If we found evidence for SUSY,

如果我們找到 超對稱的證據，

we could go from understanding 5% of our universe,

我們就可以從 對宇宙那 5% 的認識，

the things we can actually see,

也就是我們看得到的那些，

to around a third.

進展到 大約 1/3。

Not bad for a day's work.

還算不錯。

Dark energy would probably be harder to understand,

暗能量可能 更難去了解，

but there are some speculative theories out there

但有些猜測的理論

that might point the way.

也許指出了方向。

Among them are theories that go back

其中有些 可以追溯到

to that first great idea of the ancient Greeks,

古希臘人那第一個偉大的想法，

the idea that we began with several minutes ago,

也就是幾分鐘前 我們起頭的想法，

the idea that the universe must be simple.

這想法說明宇宙必須是簡單的。

These theories predict that there is just a single element

這些理論 預測所有的宇宙萬物

from which all the universe's wonderful diversity stems,

只由單一一種東西組成，

a vibrating string.

一條振動的絃。

The idea is that all the particles we know today

這想法是說 我們今天知道的所有粒子

are just different harmonics on the string.

只是這條絃上不同的波。

Unfortunately, string theories today

不幸的是，絃論現今

are, as yet, untestable.

還沒辦法證實。

But, with so much of the universe waiting to be explored,

然而，宇宙中還有 這麼多事物等著去探索，

the stakes are high.

這賭注太大了。

Does all of this make you feel small?

這所有的東西 讓你覺得藐小嗎？

It shouldn't.

不應該這樣。

Instead, you should marvel

相反地， 你應該讚嘆

in the fact that, as far as we know,

──至少到目前為止──

you are a member of the only species in the universe

你是這宇宙中 唯一一個開始了解

able even to begin to grasp its wonders,

宇宙奧秘的物種 其中的一員，

and you're living at the right time

而且你生對時代

to see our understanding explode.

來見證這知識的爆炸。