TED2008
Patricia Burchat: Shedding light on dark matter
派翠西亞柏莎一窺暗物質清晰面貌
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物理學家派翠西亞柏莎帶我們領略-構成宇宙的兩大基本成分：暗物質和暗能量。兩者相加合，佔宇宙的96%，無法直接測量的到，但是卻有無與倫比的影響！
Patricia Burchat - Particle physicist
Patricia Burchat studies the structure and distribution of dark matter and dark energy. These mysterious ingredients can't be measured in conventional ways, yet form a quarter of the mass of our universe. Full bio
Patricia Burchat studies the structure and distribution of dark matter and dark energy. These mysterious ingredients can't be measured in conventional ways, yet form a quarter of the mass of our universe. Full bio
Double-click the English transcript below to play the video.
00:18
As a particle physicist, I study the elementary particles
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身為粒子物理學家的我,研究最基本的粒子
00:22
and how they interact on the most fundamental level.
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我研究,粒子和粒子之間,如何在最基礎層次上交互作用
00:25
For most of my research career, I've been using accelerators,
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多數研究生涯中,我一向都在使用加速器
00:28
such as the electron accelerator at Stanford University, just up the road,
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就像離此不遠的史丹福大學,也有一台一樣的,那種電子加速器。
00:31
to study things on the smallest scale.
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粒子物理學家,向來是從最細微,最小尺度來研究物質
00:34
But more recently, I've been turning my attention
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但是最近，我的注意力轉向了
00:36
to the universe on the largest scale.
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宇宙間最大尺度的物質。那是什麼?
00:39
Because, as I'll explain to you,
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稍後我將立刻向各位解釋-但是,我為什麼轉移注意力呢？
00:41
the questions on the smallest and the largest scale are actually very connected.
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因為,最小和最大尺度兩者間,其實有微妙的高度關聯
00:45
So I'm going to tell you about our twenty-first-century view of the universe,
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所以,我即將要談,21世紀對宇宙的最新看法
00:50
what it's made of and what the big questions in the physical sciences are --
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宇宙的構成成分是什麼，目前物理學最熱門的議題為何?
00:53
at least some of the big questions.
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即便不能完整含括全部最重要議題,至少也含有其中好幾個。
00:55
So, recently, we have realized
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最近，我們意識到
00:58
that the ordinary matter in the universe --
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宇宙中的普通物質
01:00
and by ordinary matter, I mean you, me,
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我說的「普通」物質,也就是你,我自己
01:03
the planets, the stars, the galaxies --
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行星，恆星，銀河系
01:05
the ordinary matter makes up only a few percent
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這些都是算為普通物質,且只不過佔宇宙的
01:08
of the content of the universe.
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幾個百分比而已
01:10
Almost a quarter, or approximately a quarter
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近乎四分之一，或者大約四分之一
01:13
of the matter in the universe, is stuff that's invisible.
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宇宙中的物質,全是些看不見的東西
01:16
By invisible, I mean it doesn't absorb in the electromagnetic spectrum.
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所謂不可見，我指的是它不吸收電磁波
01:20
It doesn't emit in the electromagnetic spectrum. It doesn't reflect.
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在電磁波頻譜中,它既不放射,也不反射。
01:23
It doesn't interact with the electromagnetic spectrum,
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它和電磁波譜,沒有互動可言
01:25
which is what we use to detect things.
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而電磁波,正是我們平常用來檢測物質的方法
01:27
It doesn't interact at all. So how do we know it's there?
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當它根本對電磁波不作反應,你如何知道它存在呢？
01:30
We know it's there by its gravitational effects.
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透過重力效應,是可以知道的。
01:32
In fact, this dark matter dominates
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事實上,在宇宙中,大尺度物質
01:35
the gravitational effects in the universe on a large scale,
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的重力效應,全是由「暗物質」在操縱
01:38
and I'll be telling you about the evidence for that.
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相關證據,稍後我會再和各位分享
01:40
What about the rest of the pie?
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現在先講,這大餅圖中,還有一大塊無名,那是什麼？
01:42
The rest of the pie is a very mysterious substance called dark energy.
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剩下的一大塊,是一種稱為「暗能量」,極神秘物質
01:46
More about that later, OK.
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細節,稍後再說
01:48
So for now, let's turn to the evidence for dark matter.
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現在，我們來談談「暗物質存在」的證據
01:51
In these galaxies, especially in a spiral galaxy like this,
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在這些星系中，尤其是在一個像這樣的螺旋星系中
01:54
most of the mass of the stars is concentrated in the middle of the galaxy.
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大部分恆星的「質量」(mass)都集中在星系的中央附近
01:59
This huge mass of all these stars keeps stars in circular orbits in the galaxy.
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這是很巨大的質量。也因為它,恆星在星系中,沿著圓形軌道在運動
02:06
So we have these stars going around in circles like this.
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所以我們看到這些恒星沿圓圈這樣運動
02:09
As you can imagine, even if you know physics, this should be intuitive, OK --
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不難想像-這和懂不懂物理沒差別-直覺上就應該知道
02:13
that stars that are closer to the mass in the middle will be rotating at a higher speed
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比較靠近星系質量中央的恆星,繞行運轉時,速度較高
02:19
than those that are further out here, OK.
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和外圈的恆星相比,同意嗎
02:22
So what you would expect is that if you measured the orbital speed of the stars,
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如果你測量這些恒星運動的軌道速度
02:27
that they should be slower on the edges than on the inside.
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應該是邊緣的會比裏面的慢
02:31
In other words, if we measured speed as a function of distance --
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換句話說，如果我們以速度作為距離的函數
02:33
this is the only time I'm going to show a graph, OK --
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這篇短講不會有很多圖表,這是唯一一張
02:35
we would expect that it goes down as the distance increases
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我們認為,速度會隨它和星系中央的距離增加
02:39
from the center of the galaxy.
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而減慢
02:41
When those measurements are made,
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當我們實際進行測量的時候
02:42
instead what we find is that the speed is basically constant,
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出乎意料，我們卻發現這些速度都是幾乎不變動的「恆量」
02:45
as a function of distance.
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當你以距離為函數
02:47
If it's constant, that means that the stars out here
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若它為恆量時,這意味著,這些恆星
02:50
are feeling the gravitational effects of matter that we do not see.
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正感受得到,一些我們看不見的物質所產生的重力效應
02:54
In fact, this galaxy and every other galaxy
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這個星系以及其他每一個星系
02:57
appears to be embedded in a cloud of this invisible dark matter.
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似乎都是內嵌在這樣一個不可見的暗物質雲層中
03:02
And this cloud of matter is much more spherical than the galaxy themselves,
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而這片物質雲,比星系本身,更加的接近於球形
03:06
and it extends over a much wider range than the galaxy.
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而且這片物質雲的範圍,比星系本身更廣得多
03:10
So we see the galaxy and fixate on that, but it's actually a cloud of dark matter
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所以,當我們看見的是星系,注視著的,是星系,但實際上那背後有一團暗物質雲
03:14
that's dominating the structure and the dynamics of this galaxy.
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主導著這星系的結構和運動
03:19
Galaxies themselves are not strewn randomly in space;
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這些星系,在太空中,並非任意的散佈
03:22
they tend to cluster.
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它們有成群聚合的傾向
03:24
And this is an example of a very, actually, famous cluster, the Coma cluster.
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舉一個例,非常有名的后髮座（Coma）星系團
03:27
And there are thousands of galaxies in this cluster.
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這個星系團中有數以千計的星系
03:30
They're the white, fuzzy, elliptical things here.
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這些白色的，模糊的，橢圓的東西就是星系
03:33
So these galaxy clusters -- we take a snapshot now,
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這些星系團-我們幫它拍一張照片
03:36
we take a snapshot in a decade, it'll look identical.
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十年後再拍一張,它還是一點都不會改變
03:39
But these galaxies are actually moving at extremely high speeds.
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但是,星系團,其實是在極高速的運動狀態中
03:43
They're moving around in this gravitational potential well of this cluster, OK.
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它們其實是在這個星系團的一個「重力勢阱」中運動著
03:48
So all of these galaxies are moving.
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所以,所有這些星系都在運動
03:50
We can measure the speeds of these galaxies, their orbital velocities,
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我們可以藉由測量這些運動，它們的軌道速率
03:54
and figure out how much mass is in this cluster.
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計算得出星系團中有多少「質量」
03:56
And again, what we find is that there is much more mass there
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再一次，我們發現實際上那裏的質量
04:00
than can be accounted for by the galaxies that we see.
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要比按照「看得見的」星系,計算得出的結果還多
04:04
Or if we look in other parts of the electromagnetic spectrum,
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當我們看其他部分的電磁波譜
04:06
we see that there's a lot of gas in this cluster, as well.
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也看得到星系團裏有很多氣體
04:09
But that cannot account for the mass either.
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但那些氣體並不能解釋這些質量的存在
04:11
In fact, there appears to be about ten times as much mass here
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事實上，這裏多出來的質量大約有10倍
04:14
in the form of this invisible or dark matter
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是以暗物質型態,存在著
04:17
as there is in the ordinary matter, OK.
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暗物質是普通物質的10倍。
04:21
It would be nice if we could see this dark matter a little bit more directly.
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我想,如果大家都能更直接地看到暗物質,豈不更妙
04:25
I'm just putting this big, blue blob on there, OK,
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所以,我在這裏放一個大藍色泡泡
04:27
to try to remind you that it's there.
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提醒你們:「暗物質就在那兒!」
04:29
Can we see it more visually? Yes, we can.
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但,是否可以在視覺上「看」見它呢？可以。
04:32
And so let me lead you through how we can do this.
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現在我帶大家實際瞭解,怎樣看見暗物質：
04:34
So here's an observer:
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這裏是一個觀察者
04:36
it could be an eye; it could be a telescope.
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無論是一隻眼睛；或者也可以是一個望遠鏡
04:38
And suppose there's a galaxy out here in the universe.
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假設在宇宙中有一個星系
04:40
How do we see that galaxy?
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我們怎樣看得到那個星系的呢？
04:42
A ray of light leaves the galaxy and travels through the universe
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一束光從那星系離開、穿過宇宙
04:45
for perhaps billions of years
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經過了也許幾十億年
04:47
before it enters the telescope or your eye.
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然後進入望遠鏡,或映入你的眼簾中
04:50
Now, how do we deduce where the galaxy is?
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現在,你如何猜測星系的位置在哪裡？
04:53
Well, we deduce it by the direction that the ray is traveling
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嗯,我們按光線來的方向,去猜,它的位置
04:56
as it enters our eye, right?
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當光線抵達我們的眼睛時,我們就是這樣猜的
04:58
We say, the ray of light came this way;
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例如，這束光這樣出來
05:00
the galaxy must be there, OK.
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我猜星系一定在那。
05:02
Now, suppose I put in the middle a cluster of galaxies --
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現在,假設我在螢幕中央放一個星系團--
05:06
and don't forget the dark matter, OK.
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別忘了,連暗物質也在那兒
05:08
Now, if we consider a different ray of light, one going off like this,
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現在，如果我們考慮,另外一束這樣走的光線
05:12
we now need to take into account
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我們現在需要考慮
05:14
what Einstein predicted when he developed general relativity.
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當愛因斯坦他發展出廣義相對論時,曾經預言過的
05:17
And that was that the gravitational field, due to mass,
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也就是,由於有「質量」的關係而發生的「重力場」
05:21
will deflect not only the trajectory of particles,
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不僅會使粒子的運動軌跡偏轉
05:24
but will deflect light itself.
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而且也會使光本身偏轉
05:27
So this light ray will not continue in a straight line,
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所以這束光不會沿直線行進
05:30
but would rather bend and could end up going into our eye.
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而是，會彎曲，並最終仍抵達、進入我們的眼睛
05:34
Where will this observer see the galaxy?
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這個觀察者,會看到的星系,是在哪裡呢？
05:37
You can respond. Up, right?
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你們會回答。上面。對嗎？
05:41
We extrapolate backwards and say the galaxy is up here.
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我們向後倒推，然後斷定星系在這裏
05:44
Is there any other ray of light
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這裏還有其他,也從這個星系而來,
05:45
that could make into the observer's eye from that galaxy?
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並且也進入觀察者眼睛的光線嗎？
05:48
Yes, great. I see people going down like this.
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是的,非常好。我看到你們有人比向下的手勢。
05:51
So a ray of light could go down, be bent
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一束光,它也可以往下走,然後彎曲
05:53
up into the observer's eye,
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並進入觀察者的眼睛,
05:55
and the observer sees a ray of light here.
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這觀察著便會在這裏,看到一束光。
05:57
Now, take into account the fact that we live in
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現在,考慮到,我們生活在一個
05:59
a three-dimensional universe, OK,
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有三度空間的宇宙中
06:01
a three-dimensional space.
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太空是三度空間的
06:03
Are there any other rays of light that could make it into the eye?
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那麼,還有其他光線,可以進入我們的眼睛嗎？
06:06
Yes! The rays would lie on a -- I'd like to see -- yeah, on a cone.
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是的，光線可以排列呈現-按你們比出來的手勢-它是個,圓錐形
06:12
So there's a whole ray of light -- rays of light on a cone --
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所以,許多束光,匯聚成一個圓錐形
06:14
that will all be bent by that cluster
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意思是,這些光都經過了星系團的彎曲
06:16
and make it into the observer's eye.
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然後進入觀察者的眼睛裡
06:19
If there is a cone of light coming into my eye, what do I see?
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因為有呈圓錐形的光,這樣進入我的眼睛,所以,我會看到什麼？
06:24
A circle, a ring. It's called an Einstein ring. Einstein predicted that, OK.
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一個圓圈,或環形。這被稱為「愛因斯坦環」--因為愛因斯坦首先預測到這個現象
06:28
Now, it will only be a perfect ring if the source, the deflector
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當然,弧形原本應該是相當完美的弧,前提是,如果光源,偏導體和眼球
06:33
and the eyeball, in this case, are all in a perfectly straight line.
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正好全都在一條筆直的線上
06:38
If they're slightly skewed, we'll see a different image.
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如果它們被略微偏轉，我們將會看到一個不同的圖像
06:41
Now, you can do an experiment tonight over the reception, OK,
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你們今晚就可以在接待櫃檯,做一個試驗
06:44
to figure out what that image will look like.
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你就看到這個圖像會是什麼樣子
06:47
Because it turns out that there is a kind of lens that we can devise,
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因為我們可以設計一種透鏡
06:51
that has the right shape to produce this kind of effect.
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它的形狀,很合適用來產生這種現象
06:54
We call this gravitational lensing.
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我們稱它為重力透鏡
06:56
And so, this is your instrument, OK.
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所以,這就是你們的儀器
06:59
(Laughter).
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（笑聲）
07:00
But ignore the top part.
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但是請忽略上半部
07:03
It's the base that I want you to concentrate, OK.
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只看它底座的部分就好了
07:06
So, actually, at home, whenever we break a wineglass,
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所以,我家無論誰打破一隻高腳酒杯
07:08
I save the bottom, take it over to the machine shop.
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我都把底部留著用,先拿到玻璃店去
07:10
We shave it off, and I have a little gravitational lens, OK.
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把頭切掉,然後重力透鏡就出現了,妙吧
07:14
So it's got the right shape to produce the lensing.
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它的形狀很合適產生透鏡效果
07:16
And so the next thing you need to do in your experiment
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這個實驗的下一步驟就是
07:18
is grab a napkin. I grabbed a piece of graph paper -- I'm a physicist. (Laughter)
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找一張餐巾紙-本人是物理學者,所以我會拿一張有學問一點的方格紙.(笑聲)
07:22
So, a napkin. Draw a little model galaxy in the middle.
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ok,拿一張餐巾紙。在正中央畫一個小小的星系模型。
07:26
And now put the lens over the galaxy,
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然後把透鏡挪到星系正上方
07:29
and what you'll find is that you'll see a ring, an Einstein ring.
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然後你將看到一個,愛因斯坦環
07:32
Now, move the base off to the side,
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把杯底透鏡往旁邊挪一點
07:35
and the ring will split up into arcs, OK.
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環會分裂成好幾個弧
07:38
And you can put it on top of any image.
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把它移到任何圖像上都可以
07:40
On the graph paper, you can see
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在方格紙上你可以看到
07:41
how all the lines on the graph paper have been distorted.
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方格的線條產生怎樣的扭曲
07:43
And again, this is a kind of an accurate model
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所以，你可以說,這是一種非常精確的模型
07:46
of what happens with the gravitational lensing.
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用來解釋「重力透鏡」產生的現象為何
07:48
OK, so the question is: do we see this in the sky?
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下一個問題：在天空中,我們看的到這現象嗎?
07:52
Do we see arcs in the sky when we look at, say, a cluster of galaxies?
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當我們觀察一個星系團的時候,看的到弧形嗎?
07:56
And the answer is yes.
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答案是:可以。
07:58
And so, here's an image from the Hubble Space Telescope.
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這是來自哈柏望遠鏡的圖像。
08:00
Many of the images you are seeing
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現在看到的許多圖像
08:02
are earlier from the Hubble Space Telescope.
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來自稍早的哈柏望遠鏡拍攝所得
08:04
Well, first of all, for the golden shape galaxies --
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首先,先說這些金色的星系
08:06
those are the galaxies in the cluster.
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它們是星系團中的星系
08:09
They're the ones that are embedded in that sea of dark matter
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也被內嵌在一團暗物質中
08:13
that are causing the bending of the light
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那團暗物質,就是使光發生彎曲的物質
08:15
to cause these optical illusions, or mirages, practically,
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就是它們,引起了我們對「後景星系」
08:18
of the background galaxies.
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的視錯覺,或者說,幻影
08:20
So the streaks that you see, all these streaks,
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你所看到的這些條紋,所有這些條紋
08:23
are actually distorted images of galaxies that are much further away.
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其實都是來自更遠處的星系,扭曲的圖像
08:27
So what we can do, then, is based on how much distortion
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我們能做的,就是根據所見的這些圖像
08:30
we see in those images, we can calculate how much mass
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扭曲程度的大小,計算出在這團星系中
08:34
there must be in this cluster.
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可能有多少的「質量」
08:36
And it's an enormous amount of mass.
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這個質量的總量是非常龐大的
08:38
And also, you can tell by eye, by looking at this,
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你也可以藉由觀察它（圖像）而得知一個現象
08:40
that these arcs are not centered on individual galaxies.
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這些弧線的中心並不是些單一的星系
08:44
They are centered on some more spread out structure,
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這些弧線的中心,是一些更廣,更大的結構
08:48
and that is the dark matter
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那個結構,就是暗物質
08:52
in which the cluster is embedded, OK.
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星系團,是被嵌入在暗物質中的
08:55
So this is the closest you can get to kind of seeing
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這是最接近於看到
08:57
at least the effects of the dark matter with your naked eye.
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以肉眼看得到的暗物質效果
09:00
OK, so, a quick review then, to see that you're following.
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非常快的回顧一下剛才所說的，希望你們都還跟的上。
09:03
So the evidence that we have
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我們有證據顯示
09:05
that a quarter of the universe is dark matter --
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證明宇宙有1/4是,暗物質
09:07
this gravitationally attracting stuff --
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這是些,受重力作用,被吸引住的東西
09:09
is that galaxies, the speed with which stars orbiting galaxies
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這些恆星,圍繞星系運動的速率太大
09:13
is much too large; it must be embedded in dark matter.
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必須被嵌在暗物質中
09:16
The speed with which galaxies within clusters are orbiting is much too large;
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是星系在星系團中,運動速度太大
09:20
it must be embedded in dark matter.
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以至於星系也必須,被嵌在暗物質裡
09:22
And we see these gravitational lensing effects, these distortions
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從我們所看到的這些重力透鏡的效應,這些扭曲
09:26
that say that, again, clusters are embedded in dark matter.
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我們說,這證明,星系團是嵌在,暗物質中
09:29
OK. So now, let's turn to dark energy.
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好。現在我們轉向「暗能量」
09:33
So to understand the evidence for dark energy, we need to discuss something
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所以為了瞭解暗能量的證據，我們需要討論一些
09:36
that Stephen Hawking referred to in the previous session.
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史蒂芬霍金在上一段節目中談到的那個現象,
09:40
And that is the fact that space itself is expanding.
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也就是宇宙正在擴張的事實。
09:44
So if we imagine a section of our infinite universe --
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所以如果我們想像無限宇宙中一小部分，
09:49
and so I've put down four spiral galaxies, OK --
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我放4個漩渦星系，
09:52
and imagine that you put down a set of tape measures,
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假設你放一支卷尺
09:56
so every line on here corresponds to a tape measure,
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也就是,這裏的每一條線都對應一個卷尺
09:58
horizontal or vertical, for measuring where things are.
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水平或垂直,好測量東西的位置。
10:02
If you could do this, what you would find
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這樣一來，你將發現
10:04
that with each passing day, each passing year,
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時間每過去一天，或一年，
10:07
each passing billions of years, OK,
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或經過的是幾十億年
10:10
the distance between galaxies is getting greater.
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星系間的距離正在變得更大。
10:13
And it's not because galaxies are moving
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然而這並不是因為星系正在彼此因移動而
10:14
away from each other through space.
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在空間中,漸行漸遠
10:17
They're not necessarily moving through space.
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以空間來講,它們不一定是「在動」。
10:19
They're moving away from each other
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有此漸行漸遠的現象,是因
10:21
because space itself is getting bigger, OK.
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空間本身正在擴張。
10:24
That's what the expansion of the universe or space means.
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這是宇宙或者空間擴張的意思。
10:28
So they're moving further apart.
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它們相隔越來越遠。
10:30
Now, what Stephen Hawking mentioned, as well,
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正如史蒂芬霍金也提到的，
10:34
is that after the Big Bang, space expanded at a very rapid rate.
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在大爆炸之後，宇宙空間以非常快的速率擴張。
10:40
But because gravitationally attracting matter
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但是因為重力而發出吸引效應的物質
10:44
is embedded in this space,
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嵌在這個空間中,
10:46
it tends to slow down the expansion of the space, OK.
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而它是傾向於減慢空間擴張速率的。
10:49
So the expansion slows down with time.
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所以擴張的速率就隨著時間經過,而減慢。
10:52
So, in the last century, OK, people debated
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上個世紀，大家都在辯論著
10:56
about whether this expansion of space would continue forever;
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宇宙擴張，是否會永遠持續下去
11:01
whether it would slow down, you know,
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或者是否會減慢
11:03
will be slowing down, but continue forever;
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逐漸減速,但永遠持續的擴張
11:05
slow down and stop, asymptotically stop;
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或者漸漸減速,趨近於停止
11:10
or slow down, stop, and then reverse, so it starts to contract again.
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還是減速,停止,然後開始反轉,再次從收縮開始另一個循環
11:15
So a little over a decade ago,
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這辯論持續了近十多年,
11:17
two groups of physicists and astronomers
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兩組物理學家和天文學家
11:22
set out to measure the rate at which
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開始著手測量 宇宙擴張
11:24
the expansion of space was slowing down, OK.
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正在減速的速率是多少
11:28
By how much less is it expanding today,
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這是藉由比較
11:30
compared to, say, a couple of billion years ago?
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它今天和幾十億年前相比,減少了多少擴張。
11:33
The startling answer to this question, OK, from these experiments,
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根據實驗結果，答案是令人吃驚的，
11:38
was that space is expanding at a faster rate today
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宇宙今天正在以更快的速率擴張，
11:42
than it was a few billion years ago, OK.
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這是和幾十億年前相比
11:45
So the expansion of space is actually speeding up.
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所以,事實上,宇宙空間的擴張正在加速。
11:48
This was a completely surprising result.
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這是令人非常驚訝的結果。
11:51
There is no persuasive theoretical argument for why this should happen, OK.
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沒有令人信服的理論依據能解釋這種情形的發生原因。
11:57
No one was predicting ahead of time this is what's going to be found.
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先前，從來都沒有人預言過會有這樣的發現。
12:00
It was the opposite of what was expected.
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它和預期的是完全相反的。
12:02
So we need something to be able to explain that.
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所以我們需要某些東西可以解釋這現象。
12:05
Now it turns out, in the mathematics,
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現在我們的發現是,在數學中，
12:07
you can put it in as a term that's an energy,
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你可以把「能量」這個名詞放在這個解釋裡。
12:11
but it's a completely different type of energy
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但它是一種和我們所見過的任何一種能量，
12:12
from anything we've ever seen before.
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都完全不同的能量
12:14
We call it dark energy,
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我們叫它暗能量，
12:16
and it has this effect of causing space to expand.
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而且,它具有使宇宙發生「擴張」效果的影響力
12:19
But we don't have a good motivation
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只是,在動機的部份
12:21
for putting it in there at this point, OK.
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目前我們還缺乏一個比較好的說明。
12:23
So it's really unexplained as to why we need to put it in.
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這動機要從何解釋起,有點難。
12:26
Now, so at this point, then, what I want to really emphasize to you,
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現在,我想強調的是
12:30
is that, first of all, dark matter and dark energy
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首先,暗物質和暗能量
12:32
are completely different things, OK.
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是完全不同的東西。
12:34
There are really two mysteries out there as to what makes up most of the universe,
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談到宇宙的組合成分,這兩樣東西恰似兩大謎題
12:38
and they have very different effects.
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它們的影響,也是天差地別
12:41
Dark matter, because it gravitationally attracts,
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暗物質,因為它的重力發生引力,
12:44
it tends to encourage the growth of structure, OK.
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它傾向於促成固定結構的形成。
12:48
So clusters of galaxies will tend to form,
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所以星系傾向於集結構成星系團，
12:51
because of all this gravitational attraction.
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原因是重力帶來的吸引作用。
12:53
Dark energy, on the other hand,
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另一方面，暗能量，
12:55
is putting more and more space between the galaxies,
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卻在星系之間產生越來越多的空間。
12:59
makes it, the gravitational attraction between them decrease,
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它會使星系之間的重力吸引作用-漸漸減小,
13:02
and so it impedes the growth of structure.
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因此暗能量也就阻礙了結構的成形。
13:05
So by looking at things like clusters of galaxies,
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藉由觀察星系團，
13:08
and how they -- their number density,
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它們數量上的密度如何
13:12
how many there are as a function of time --
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以時間為函數，它們的數量是多少
13:14
we can learn about how dark matter and dark energy
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我們可以比較瞭解暗物質、暗能量
13:18
compete against each other in structure forming.
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彼此如何在結構的形成上互相競爭。
13:21
In terms of dark matter, I said that we don't have any,
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先前我說過,我們沒有
13:24
you know, really persuasive argument for dark energy.
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任何真正有說服力的論述能解釋暗能量。
13:28
Do we have anything for dark matter? And the answer is yes.
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我們有解釋暗物質的證據嗎？是的，我們有。
13:31
We have well-motivated candidates for the dark matter.
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好幾種學說論述都有相當有力的假設動機。
13:34
Now, what do I mean by well motivated?
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所謂“相當有力”指的是什麼？
13:37
I mean that we have mathematically consistent theories
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我的意思是說我們有數學上前後一致性的理論
13:42
that were actually introduced
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可以導入導出並解釋
13:44
to explain a completely different phenomenon, OK,
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一種很不一樣的現象
13:47
things that I haven't even talked about,
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一些我還沒有討論到的現象，
13:49
that each predict the existence
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它們預言到
13:52
of a very weakly interacting, new particle.
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弱作用力的新粒子。
13:55
So, this is exactly what you want in physics:
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這才是你在物理中所想要的：
13:57
where a prediction comes out of a mathematically consistent theory
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從數學上合理一致的理論建立起來的某個假設
14:01
that was actually developed for something else.
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經過實際發展後變成可以解釋其他事物的一個假設。
14:03
But we don't know if either of those
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但我們無從得知兩者是否都是
14:06
are actually the dark matter candidate, OK.
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可用來解釋暗物質的最佳答案
14:09
One or both, who knows? Or it could be something completely different.
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二者之一為是,或,以上皆是?以上皆非?沒人說的準
14:12
Now, we look for these dark matter particles
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雖然說我們是在尋找這些暗物質粒子
14:14
because, after all, they are here in the room, OK,
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不過,說到底,其實它們根本就在這裏,就在這個房間裏，
14:17
and they didn't come in the door.
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它們也沒從門口進來
14:18
They just pass through anything.
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因為,暗物質粒子是能穿透一切的。
14:20
They can come through the building, through the Earth --
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它們穿得過建築,穿得過地球;
14:22
they're so non-interacting.
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它們非常懶得打交道
14:24
So one way to look for them is to build detectors
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所以要找到它們的一種方式,是建造探測器
14:27
that are extremely sensitive to a dark matter particle coming through and bumping it.
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一台對暗物質粒子穿過,會極度敏感的探測器,甚至還會碰撞暗物質粒子。
14:31
So a crystal that will ring if that happens.
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是一種在發生暗物質粒子穿越時,會振動的水晶。
14:34
So one of my colleagues up the road and his collaborators
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我的一個同事和他的合作者
14:36
have built such a detector.
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已經建造了這樣一個探測器。
14:38
And they've put it deep down in an iron mine in Minnesota,
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他們把探測器放在明尼蘇達州某處很深的地底鐵礦坑中，
14:41
OK, deep under the ground, and in fact, in the last couple of days
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非常深的地底。前幾天
14:44
announced the most sensitive results so far.
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他們剛公佈過目前最敏銳的結果,顯示：
14:47
They haven't seen anything, OK, but it puts limits on what the mass
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他們還沒看到任何東西，但他們為暗物質的質
14:50
and the interaction strength of these dark matter particles are.
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以及相互作用強度作出了參考限制質。
14:53
There's going to be a satellite telescope launched later this year
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現在已發射衛星望遠鏡
14:57
and it will look towards the middle of the galaxy,
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將會探訪星系中心，
15:00
to see if we can see dark matter particles annihilating
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看看我們是否可以觀測到暗物質粒子湮滅
15:02
and producing gamma rays that could be detected with this.
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能製造出它偵測的到的伽瑪射線
15:06
The Large Hadron Collider, a particle physics accelerator,
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大型強子碰撞器 - 一個粒子物理加速器，
15:09
that we'll be turning on later this year.
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於2008年年底啟用
15:12
It is possible that dark matter particles might be produced
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或許,這台機器能製造出
15:15
at the Large Hadron Collider.
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暗物質粒子。
15:17
Now, because they are so non-interactive,
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因為暗物質粒子是如此不活潑，
15:18
they will actually escape the detector,
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他們其實會逃離探測器，
15:21
so their signature will be missing energy, OK.
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留下來的證據是些消失的能量。
15:24
Now, unfortunately, there is a lot of new physics
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不幸的是，很多新的物理學
15:27
whose signature could be missing energy,
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也一直不停的製造出「丟失的能量」
15:29
so it will be hard to tell the difference.
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所以，兩者之間，很難辨別
15:31
And finally, for future endeavors, there are telescopes being designed
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最後,放眼未來,我們正努力設計新的望遠鏡
15:36
specifically to address the questions of dark matter and dark energy --
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專門研究暗物質和暗能量：
15:40
ground-based telescopes, and there are three space-based telescopes
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有一些是地面的望遠鏡。而現在又有3架漫遊太空中的太空望遠鏡
15:43
that are in competition right now
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它們彼此熱烈競爭
15:45
to be launched to investigate dark matter and dark energy.
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都以研究暗物質和暗能量主要目標。
15:48
So in terms of the big questions:
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所以，回答這些大問題：
15:50
what is dark matter? What is dark energy?
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什麼是暗物質？什麼是暗能量?
15:52
The big questions facing physics.
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是物理學的大哉問
15:54
And I'm sure you have lots of questions,
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我想你們一定有很多問題。
15:57
which I very much look forward to addressing
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我期待著在接下來的
15:59
over the next 72 hours, while I'm here. Thank you.
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72小時當中和你們面對面的討論。謝謝。
16:01
(Applause)
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（掌聲）
ABOUT THE SPEAKER
Patricia Burchat - Particle physicistPatricia Burchat studies the structure and distribution of dark matter and dark energy. These mysterious ingredients can't be measured in conventional ways, yet form a quarter of the mass of our universe.
Why you should listen
Patricia Burchat studies the universe's most basic ingredients -- the mysterious dark energy and dark matter that are massively more abundant than the visible stars and galaxies. She is one of the founders of the BaBar Collaboration at the Stanford Linear Accelerator Center, a project that's hoping to answer the question, "If there are as many anti-particles as there are particles, why can't we see all these anti-particles?"
She's a member of the Large Synoptic Survey Telescope project, which will allow scientists to monitor exploding supernovae and determine how fast the universe is expanding -- and map how mass is distributed throughout the universe. She's also part of Fermilab Experiment E791, studying the production and decay of charmed particles. Burchat received a Guggenheim Fellowship in 2005.
Patricia Burchat | Speaker | TED.com