TED2008
Patricia Burchat: Shedding light on dark matter
Patricia Burchat解释暗物质
Filmed:
Readability: 4.2
1,605,112 views
物理学家Patricia Burchat解释宇宙的两种基本组成物质：暗物质和暗能量。它们组成宇宙的96%，但是不能被直接地测量，然而它们的影响是非常大的。
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
0
0
4000
作为一名粒子物理学家，我研究基本粒子
00:22
and how they interact on the most fundamental level.
1
4000
3000
以及它们如何在微观上如何相互作用
00:25
For most of my research career, I've been using accelerators,
2
7000
3000
对于我大部分的研究，我一直在使用加速器，
00:28
such as the electron accelerator at Stanford University, just up the road,
3
10000
3000
例如在斯坦福大学路边的电子加速器
00:31
to study things on the smallest scale.
4
13000
3000
去在微观上研究物质。
00:34
But more recently, I've been turning my attention
5
16000
2000
但是最近，我的注意力转向了
00:36
to the universe on the largest scale.
6
18000
3000
宏观上整个宇宙。
00:39
Because, as I'll explain to you,
7
21000
2000
因为，正如我将要对你们解释的，
00:41
the questions on the smallest and the largest scale are actually very connected.
8
23000
4000
宏观和微观上的问题其实是非常相关的。
00:45
So I'm going to tell you about our twenty-first-century view of the universe,
9
27000
5000
所以我将要告诉你们关于我们21世纪的宇宙观，
00:50
what it's made of and what the big questions in the physical sciences are --
10
32000
3000
它是由什么构成的，以及什么是物理学中的一些大问题---
00:53
at least some of the big questions.
11
35000
2000
至少是它们中的一些大问题。
00:55
So, recently, we have realized
12
37000
3000
最近，我们意识到
00:58
that the ordinary matter in the universe --
13
40000
2000
宇宙中的普通物质---
01:00
and by ordinary matter, I mean you, me,
14
42000
3000
我指的普通物质，我的意思是你，我
01:03
the planets, the stars, the galaxies --
15
45000
2000
行星，横星，银河系---
01:05
the ordinary matter makes up only a few percent
16
47000
3000
普通物质仅仅占据
01:08
of the content of the universe.
17
50000
2000
宇宙组成的一小部分。
01:10
Almost a quarter, or approximately a quarter
18
52000
3000
近乎四分之一，或者大约四分之一
01:13
of the matter in the universe, is stuff that's invisible.
19
55000
3000
的宇宙组成是一些不可见的东西。
01:16
By invisible, I mean it doesn't absorb in the electromagnetic spectrum.
20
58000
4000
不可见，我指的是它不吸收地磁波谱。
01:20
It doesn't emit in the electromagnetic spectrum. It doesn't reflect.
21
62000
3000
在光谱中不放射电磁波。它不反射电磁波。
01:23
It doesn't interact with the electromagnetic spectrum,
22
65000
2000
它在电磁波谱照射下不发生反应，
01:25
which is what we use to detect things.
23
67000
2000
而这却是我们如何用来检测物质的方法。
01:27
It doesn't interact at all. So how do we know it's there?
24
69000
3000
它根本不反应。所以我们如何知道它们在那？
01:30
We know it's there by its gravitational effects.
25
72000
2000
我的得知它们存在通过引力效应。
01:32
In fact, this dark matter dominates
26
74000
3000
实际上，这种暗物质
01:35
the gravitational effects in the universe on a large scale,
27
77000
3000
宏观上统治宇宙中的引力效应，
01:38
and I'll be telling you about the evidence for that.
28
80000
2000
我将会告诉你们它的证据。
01:40
What about the rest of the pie?
29
82000
2000
派的其它部分是什么呢？
01:42
The rest of the pie is a very mysterious substance called dark energy.
30
84000
4000
这个派的其它部分是一种十分神秘的物质，叫做暗能量。
01:46
More about that later, OK.
31
88000
2000
一会再讨论它。
01:48
So for now, let's turn to the evidence for dark matter.
32
90000
3000
所以现在，我们来谈谈暗物质存在的证据。
01:51
In these galaxies, especially in a spiral galaxy like this,
33
93000
3000
在这些星系中，尤其是在一个像这样的螺旋星系中，
01:54
most of the mass of the stars is concentrated in the middle of the galaxy.
34
96000
5000
大部分的质量集中在星系的中央。
01:59
This huge mass of all these stars keeps stars in circular orbits in the galaxy.
35
101000
7000
这些恒星巨大的质量使得这些星星在星系中沿圆周运动轨道运动。
02:06
So we have these stars going around in circles like this.
36
108000
3000
所以我们看到这些恒星沿圆圈这样运动。
02:09
As you can imagine, even if you know physics, this should be intuitive, OK --
37
111000
4000
如你所想，即使你不知道物理----这应该是很直观的，
02:13
that stars that are closer to the mass in the middle will be rotating at a higher speed
38
115000
6000
这些靠近中心的恒星将会以更高的速度旋转，
02:19
than those that are further out here, OK.
39
121000
3000
相比于在外面的这些。
02:22
So what you would expect is that if you measured the orbital speed of the stars,
40
124000
5000
所以，你所期待的也许是如果你测量这些恒星运动的轨道速度，
02:27
that they should be slower on the edges than on the inside.
41
129000
4000
它们（速度）应该是边缘的比里面的慢。
02:31
In other words, if we measured speed as a function of distance --
42
133000
2000
换言之，如果我们测量速度作为距离的函数---
02:33
this is the only time I'm going to show a graph, OK --
43
135000
2000
这是我唯一一次展示图表，好吗？
02:35
we would expect that it goes down as the distance increases
44
137000
4000
我们会期待它（速度）会减小
02:39
from the center of the galaxy.
45
141000
2000
随着距离星系中央的路程增加。
02:41
When those measurements are made,
46
143000
1000
当这些被测量，
02:42
instead what we find is that the speed is basically constant,
47
144000
3000
反而，我们发现这个速度基本上是一个常数，
02:45
as a function of distance.
48
147000
2000
作为距离的函数。
02:47
If it's constant, that means that the stars out here
49
149000
3000
如果它（速度）是一个常数，这意味着外面的恒星
02:50
are feeling the gravitational effects of matter that we do not see.
50
152000
4000
正在感受到一些我们看不到物质所施加的引力效应。
02:54
In fact, this galaxy and every other galaxy
51
156000
3000
事实上，这个星系以及每一个其它的星系
02:57
appears to be embedded in a cloud of this invisible dark matter.
52
159000
5000
似乎被内嵌在一团我们看不到的暗物质中。
03:02
And this cloud of matter is much more spherical than the galaxy themselves,
53
164000
4000
这团物质比星系本身更加类似于球形，
03:06
and it extends over a much wider range than the galaxy.
54
168000
4000
而且它们（暗物质）比星系本身延伸至更广的范围。
03:10
So we see the galaxy and fixate on that, but it's actually a cloud of dark matter
55
172000
4000
所以，我们注视着这个星系，但是它其实实在一团
03:14
that's dominating the structure and the dynamics of this galaxy.
56
176000
5000
决定它们结构与动态的暗物质中。
03:19
Galaxies themselves are not strewn randomly in space;
57
181000
3000
星系本身并不是任意地散布在空间中；
03:22
they tend to cluster.
58
184000
2000
它们趋向于聚集在一起。
03:24
And this is an example of a very, actually, famous cluster, the Coma cluster.
59
186000
3000
这是一个实际上非常著名的星系团：后发座（Coma）星系团。
03:27
And there are thousands of galaxies in this cluster.
60
189000
3000
而且这个星系团中有数以千计的星系。
03:30
They're the white, fuzzy, elliptical things here.
61
192000
3000
它们是这些白色的，模糊的，椭圆的东西。
03:33
So these galaxy clusters -- we take a snapshot now,
62
195000
3000
所以，这些星系团——我们现在拍一张照，
03:36
we take a snapshot in a decade, it'll look identical.
63
198000
3000
十年后我们拍一张照——它们将会看起来一模一样。
03:39
But these galaxies are actually moving at extremely high speeds.
64
201000
4000
但是这些星系团其实在以极高的速度运动。
03:43
They're moving around in this gravitational potential well of this cluster, OK.
65
205000
5000
它们其实在这个星系团的引力势阱中运动。
03:48
So all of these galaxies are moving.
66
210000
2000
所以，这些星系在运动。
03:50
We can measure the speeds of these galaxies, their orbital velocities,
67
212000
4000
我们可以测量这些星系的速率，它们的轨道速度，
03:54
and figure out how much mass is in this cluster.
68
216000
2000
并算出星系团中有多少质量。
03:56
And again, what we find is that there is much more mass there
69
218000
4000
并且再一次，我们发现的这里有更多的质量
04:00
than can be accounted for by the galaxies that we see.
70
222000
4000
相比于我们实际看到的星系所能证明的。
04:04
Or if we look in other parts of the electromagnetic spectrum,
71
226000
2000
或者我们看其它部分的电磁波谱，
04:06
we see that there's a lot of gas in this cluster, as well.
72
228000
3000
我们看到这里也有很多气体。
04:09
But that cannot account for the mass either.
73
231000
2000
但是那也不能解释这些质量。
04:11
In fact, there appears to be about ten times as much mass here
74
233000
3000
事实上，这里有大约10倍多的质量
04:14
in the form of this invisible or dark matter
75
236000
3000
以暗物质存在
04:17
as there is in the ordinary matter, OK.
76
239000
4000
相比于普通物质。
04:21
It would be nice if we could see this dark matter a little bit more directly.
77
243000
4000
如果我们能更直接地看到暗物质，那会更好
04:25
I'm just putting this big, blue blob on there, OK,
78
247000
2000
我只放一个大的蓝色的水泡在这里，
04:27
to try to remind you that it's there.
79
249000
2000
试图提醒你它们（暗物质）在这里。
04:29
Can we see it more visually? Yes, we can.
80
251000
3000
我们能更形象地看到它们嘛？是的，我们可以。
04:32
And so let me lead you through how we can do this.
81
254000
2000
那么让我帮助你们了解如何这样做。
04:34
So here's an observer:
82
256000
2000
那么这里是一个观察器：
04:36
it could be an eye; it could be a telescope.
83
258000
2000
它可以是一只眼睛；它可以是一个望远镜。
04:38
And suppose there's a galaxy out here in the universe.
84
260000
2000
假设在宇宙中有一个星系。
04:40
How do we see that galaxy?
85
262000
2000
我们如何能看到那个星系？
04:42
A ray of light leaves the galaxy and travels through the universe
86
264000
3000
一束光离开星系并穿过宇宙
04:45
for perhaps billions of years
87
267000
2000
经过了也许几十亿年
04:47
before it enters the telescope or your eye.
88
269000
3000
在它进入望远镜或者你的眼睛之前。
04:50
Now, how do we deduce where the galaxy is?
89
272000
3000
现在，你如何猜测星系的位置？
04:53
Well, we deduce it by the direction that the ray is traveling
90
275000
3000
嗯，我们猜测它的位置根据光线传播
04:56
as it enters our eye, right?
91
278000
2000
进入我们眼睛的方向？
04:58
We say, the ray of light came this way;
92
280000
2000
例如，这束光这样出来，
05:00
the galaxy must be there, OK.
93
282000
2000
星系一定在那。
05:02
Now, suppose I put in the middle a cluster of galaxies --
94
284000
4000
现在，假设我在屏幕中央放一个星系团---
05:06
and don't forget the dark matter, OK.
95
288000
2000
别忘了还有暗物质，好吗？
05:08
Now, if we consider a different ray of light, one going off like this,
96
290000
4000
现在，如果我们考虑另外一束像这样离开的光线，
05:12
we now need to take into account
97
294000
2000
我们现在需要考虑
05:14
what Einstein predicted when he developed general relativity.
98
296000
3000
爱因斯坦当他发展广义相对论的时候，曾经预言过的（现象）。
05:17
And that was that the gravitational field, due to mass,
99
299000
4000
那就是由于有质量，引力场
05:21
will deflect not only the trajectory of particles,
100
303000
3000
不仅会使粒子的运动轨迹偏转，
05:24
but will deflect light itself.
101
306000
3000
而且会使光本身偏转。
05:27
So this light ray will not continue in a straight line,
102
309000
3000
所以这束光不会沿直线行进，
05:30
but would rather bend and could end up going into our eye.
103
312000
4000
相反会弯曲然后最终进入我们的眼睛
05:34
Where will this observer see the galaxy?
104
316000
3000
这个观察器会在哪里看到星系呢？
05:37
You can respond. Up, right?
105
319000
4000
你们可以回答我。上面，对吗？
05:41
We extrapolate backwards and say the galaxy is up here.
106
323000
3000
我们倒推然后确定星系在这里。
05:44
Is there any other ray of light
107
326000
1000
这里还有其它的
05:45
that could make into the observer's eye from that galaxy?
108
327000
3000
可以进入观察者眼睛的光线嘛？
05:48
Yes, great. I see people going down like this.
109
330000
3000
是的，非常好。我看到人们做向下的姿势。
05:51
So a ray of light could go down, be bent
110
333000
2000
一束光也可以往下走，然后弯曲
05:53
up into the observer's eye,
111
335000
2000
进入观察者的眼睛，
05:55
and the observer sees a ray of light here.
112
337000
2000
这个观察着便会在这里看到一束光。
05:57
Now, take into account the fact that we live in
113
339000
2000
现在，考虑我们生活在
05:59
a three-dimensional universe, OK,
114
341000
2000
三维宇宙的事实
06:01
a three-dimensional space.
115
343000
2000
一个三维空间。
06:03
Are there any other rays of light that could make it into the eye?
116
345000
3000
还有其它光线可以进入我们的眼睛嘛？
06:06
Yes! The rays would lie on a -- I'd like to see -- yeah, on a cone.
117
348000
6000
是的，光线可以排列在一个---我希望看到---对了，一个圆锥形
06:12
So there's a whole ray of light -- rays of light on a cone --
118
354000
2000
所以，许多束光会在一个圆锥上---
06:14
that will all be bent by that cluster
119
356000
2000
它们都被弯曲过
06:16
and make it into the observer's eye.
120
358000
3000
然后进入观察者的眼睛。
06:19
If there is a cone of light coming into my eye, what do I see?
121
361000
5000
如果有锥形的光进入我的眼睛，我看到了什么？
06:24
A circle, a ring. It's called an Einstein ring. Einstein predicted that, OK.
122
366000
4000
一个圆圈，一个环形。它被称作一个爱因斯坦环---爱因斯坦预言了它
06:28
Now, it will only be a perfect ring if the source, the deflector
123
370000
5000
那么，它仅仅会是一个完美的环形如果它的源，这个偏导物质
06:33
and the eyeball, in this case, are all in a perfectly straight line.
124
375000
5000
以及我们的眼球，在这个情况下，恰好在一条直线上。
06:38
If they're slightly skewed, we'll see a different image.
125
380000
3000
如果它们被略微偏转，我们将会看到一个不同的图像
06:41
Now, you can do an experiment tonight over the reception, OK,
126
383000
3000
你们今晚在招待会后可以做一个试验，
06:44
to figure out what that image will look like.
127
386000
3000
去看到这个图像会是什么样子。
06:47
Because it turns out that there is a kind of lens that we can devise,
128
389000
4000
因为我们可以设计一种透镜，
06:51
that has the right shape to produce this kind of effect.
129
393000
3000
它（透镜）有产生这种现象的合适的形状。
06:54
We call this gravitational lensing.
130
396000
2000
我们称它为引力透镜。
06:56
And so, this is your instrument, OK.
131
398000
3000
所以，这是你们的仪器
06:59
(Laughter).
132
401000
1000
（笑声）
07:00
But ignore the top part.
133
402000
3000
但是忽略上部。
07:03
It's the base that I want you to concentrate, OK.
134
405000
3000
我希望你们关注它的底座。
07:06
So, actually, at home, whenever we break a wineglass,
135
408000
2000
所以实际上，在家里，不管何时我们打碎一个玻璃酒杯，
07:08
I save the bottom, take it over to the machine shop.
136
410000
2000
我保留它的底部，把它送去机械修理店。
07:10
We shave it off, and I have a little gravitational lens, OK.
137
412000
4000
我们把它剃掉，然后我就有了一个引力透镜。
07:14
So it's got the right shape to produce the lensing.
138
416000
2000
所以，它有合适产生透镜效果的形状。
07:16
And so the next thing you need to do in your experiment
139
418000
2000
所以，你在实验中需要做的下一件事情，
07:18
is grab a napkin. I grabbed a piece of graph paper -- I'm a physicist. (Laughter)
140
420000
4000
就是找来一张餐巾纸。我找来了一张坐标纸；我是一个物理学家。（笑声）
07:22
So, a napkin. Draw a little model galaxy in the middle.
141
424000
4000
那么，一张餐巾纸。在中间画一个小小的星系模型。
07:26
And now put the lens over the galaxy,
142
428000
3000
然后现在把透镜放到星系上，
07:29
and what you'll find is that you'll see a ring, an Einstein ring.
143
431000
3000
你将看到的是，一个爱因斯坦环。
07:32
Now, move the base off to the side,
144
434000
3000
现在，把底座移到另一边，
07:35
and the ring will split up into arcs, OK.
145
437000
3000
然后，这个圆环会分裂成一些弧形。
07:38
And you can put it on top of any image.
146
440000
2000
你可以把它放到任何图像上。
07:40
On the graph paper, you can see
147
442000
1000
在坐标纸上你可以看到
07:41
how all the lines on the graph paper have been distorted.
148
443000
2000
这些线是如何被扭曲的。
07:43
And again, this is a kind of an accurate model
149
445000
3000
再一次说明，这是一种非常精确的模型
07:46
of what happens with the gravitational lensing.
150
448000
2000
去解释引力透镜产生的现象。
07:48
OK, so the question is: do we see this in the sky?
151
450000
4000
那么，问题是：我们在天空中看到这个吗？
07:52
Do we see arcs in the sky when we look at, say, a cluster of galaxies?
152
454000
4000
当我们看一个星系团的时候，我们能看到弧形吗？
07:56
And the answer is yes.
153
458000
2000
答案是:是的。
07:58
And so, here's an image from the Hubble Space Telescope.
154
460000
2000
这是来自哈勃望远镜的图像。
08:00
Many of the images you are seeing
155
462000
2000
你看到的许多图像
08:02
are earlier from the Hubble Space Telescope.
156
464000
2000
来自早期的哈勃望远镜。
08:04
Well, first of all, for the golden shape galaxies --
157
466000
2000
嗯，首先，关于这些金色的星系---
08:06
those are the galaxies in the cluster.
158
468000
3000
它们是在星系团中的一些星系。
08:09
They're the ones that are embedded in that sea of dark matter
159
471000
4000
它们嵌在一团暗物质中
08:13
that are causing the bending of the light
160
475000
2000
因而引起了光的弯曲
08:15
to cause these optical illusions, or mirages, practically,
161
477000
3000
引起了这些视错觉，或者差不多，蜃景，
08:18
of the background galaxies.
162
480000
2000
来自后面的星系。
08:20
So the streaks that you see, all these streaks,
163
482000
3000
所以你看到条纹，所有这些条纹，
08:23
are actually distorted images of galaxies that are much further away.
164
485000
4000
其实都是更远出的扭曲的星系的图像。
08:27
So what we can do, then, is based on how much distortion
165
489000
3000
那么我们能做的，就是根据扭曲程度的大小
08:30
we see in those images, we can calculate how much mass
166
492000
4000
来自这些图像，我们可以计算出
08:34
there must be in this cluster.
167
496000
2000
在这团星系中一定有多少质量。
08:36
And it's an enormous amount of mass.
168
498000
2000
质量的总额是十分庞大的。
08:38
And also, you can tell by eye, by looking at this,
169
500000
2000
所以，你可以通过观察它（图像），辨别
08:40
that these arcs are not centered on individual galaxies.
170
502000
4000
这些弧线的中心不是某一个星系；
08:44
They are centered on some more spread out structure,
171
506000
4000
它们（弧线）以一个更加扩散的的结构为中心。
08:48
and that is the dark matter
172
510000
4000
这就是暗物质
08:52
in which the cluster is embedded, OK.
173
514000
3000
星系嵌入其中。
08:55
So this is the closest you can get to kind of seeing
174
517000
2000
这是最接近于看到
08:57
at least the effects of the dark matter with your naked eye.
175
519000
3000
至少通过肉眼看到暗物质的影响。
09:00
OK, so, a quick review then, to see that you're following.
176
522000
3000
那么，一个非常快的回顾，以知道你们正在跟随。
09:03
So the evidence that we have
177
525000
2000
我们有的证据
09:05
that a quarter of the universe is dark matter --
178
527000
2000
证明这¼是暗物质---
09:07
this gravitationally attracting stuff --
179
529000
2000
这些以引力作用吸引的东西---
09:09
is that galaxies, the speed with which stars orbiting galaxies
180
531000
4000
（证据）是这些行星围绕星系运动的速率
09:13
is much too large; it must be embedded in dark matter.
181
535000
3000
（速率）过大；它（行星）一定嵌在暗物质中
09:16
The speed with which galaxies within clusters are orbiting is much too large;
182
538000
4000
星系在星系团中的圆周运动速度太大了；
09:20
it must be embedded in dark matter.
183
542000
2000
它（星系）一定嵌在暗物质中
09:22
And we see these gravitational lensing effects, these distortions
184
544000
4000
我们看到了这些引力透镜的效应。这些扭曲（的现象）
09:26
that say that, again, clusters are embedded in dark matter.
185
548000
3000
再次证明，星系团嵌在暗物质中。
09:29
OK. So now, let's turn to dark energy.
186
551000
4000
好。现在我们转向暗能量。
09:33
So to understand the evidence for dark energy, we need to discuss something
187
555000
3000
所以为了了解暗能量的证据，我们需要讨论一些
09:36
that Stephen Hawking referred to in the previous session.
188
558000
4000
史蒂芬霍金前一段谈到的现象。
09:40
And that is the fact that space itself is expanding.
189
562000
4000
那就是宇宙正在扩张的事实。
09:44
So if we imagine a section of our infinite universe --
190
566000
5000
所以如果我们想象无限宇宙中一小部分，
09:49
and so I've put down four spiral galaxies, OK --
191
571000
3000
然后我放4个漩涡星系，
09:52
and imagine that you put down a set of tape measures,
192
574000
4000
假设你放一套卷尺，
09:56
so every line on here corresponds to a tape measure,
193
578000
2000
这里的每一条线对以一个卷尺---
09:58
horizontal or vertical, for measuring where things are.
194
580000
4000
水平的或垂直的---用来测量东西的位置。
10:02
If you could do this, what you would find
195
584000
2000
如果你可以这样做，你将发现的是
10:04
that with each passing day, each passing year,
196
586000
3000
每过去一天，每过去一年，
10:07
each passing billions of years, OK,
197
589000
3000
每过去几十亿年
10:10
the distance between galaxies is getting greater.
198
592000
3000
星系间的距离正在变得更大。
10:13
And it's not because galaxies are moving
199
595000
1000
然而这并不是因为星系在运动
10:14
away from each other through space.
200
596000
3000
在空间中互相远离；
10:17
They're not necessarily moving through space.
201
599000
2000
他们不一定在动。
10:19
They're moving away from each other
202
601000
2000
他们正在远离对方
10:21
because space itself is getting bigger, OK.
203
603000
3000
因为空间本身正在扩张。
10:24
That's what the expansion of the universe or space means.
204
606000
4000
这是宇宙或者空间扩张的意思。
10:28
So they're moving further apart.
205
610000
2000
所以他们正运动地越来越远。
10:30
Now, what Stephen Hawking mentioned, as well,
206
612000
4000
史蒂芬霍金也提到的，
10:34
is that after the Big Bang, space expanded at a very rapid rate.
207
616000
6000
在大爆炸之后，宇宙空间以非常快的速率扩张。
10:40
But because gravitationally attracting matter
208
622000
4000
但是因为制造引力的物质
10:44
is embedded in this space,
209
626000
2000
嵌在这个空间中，
10:46
it tends to slow down the expansion of the space, OK.
210
628000
3000
它（暗物质）倾向于减慢空间扩张的速率。
10:49
So the expansion slows down with time.
211
631000
3000
所以扩张的速率随着时间减慢。
10:52
So, in the last century, OK, people debated
212
634000
4000
所以，上个世纪，人们辩论
10:56
about whether this expansion of space would continue forever;
213
638000
5000
宇宙是否会永远扩张，
11:01
whether it would slow down, you know,
214
643000
2000
是否会减慢，
11:03
will be slowing down, but continue forever;
215
645000
2000
或者是否会减慢，但是永远进行。
11:05
slow down and stop, asymptotically stop;
216
647000
5000
或者减慢并停止，接近停止。
11:10
or slow down, stop, and then reverse, so it starts to contract again.
217
652000
5000
或者减慢，停止，然后在颠倒，再重新收缩。
11:15
So a little over a decade ago,
218
657000
2000
所以十多年后，
11:17
two groups of physicists and astronomers
219
659000
5000
两组物理学家和天文学家
11:22
set out to measure the rate at which
220
664000
2000
着手测量
11:24
the expansion of space was slowing down, OK.
221
666000
4000
宇宙减速扩张的速率。
11:28
By how much less is it expanding today,
222
670000
2000
通过它今天少扩张了多少，
11:30
compared to, say, a couple of billion years ago?
223
672000
3000
用于和几十亿年前比较。
11:33
The startling answer to this question, OK, from these experiments,
224
675000
5000
这个问题的令人吃惊的答案是，根据这些实验，
11:38
was that space is expanding at a faster rate today
225
680000
4000
宇宙本身今天正在以更快的速率扩张，
11:42
than it was a few billion years ago, OK.
226
684000
3000
相比于几十亿年前。
11:45
So the expansion of space is actually speeding up.
227
687000
3000
所以宇宙空间的扩张正在加速。
11:48
This was a completely surprising result.
228
690000
3000
这是完全令人惊讶的结果。
11:51
There is no persuasive theoretical argument for why this should happen, OK.
229
693000
6000
没有令人信服的理论依据解释为什么这会发生。
11:57
No one was predicting ahead of time this is what's going to be found.
230
699000
3000
没有人事先预言了什么将会被发现。
12:00
It was the opposite of what was expected.
231
702000
2000
它（实验结果）和我们的期望是相反的。
12:02
So we need something to be able to explain that.
232
704000
3000
所以我们需要一些东西去解释它。
12:05
Now it turns out, in the mathematics,
233
707000
2000
现在，在数学中，
12:07
you can put it in as a term that's an energy,
234
709000
4000
你可以放入一项成为能量。
12:11
but it's a completely different type of energy
235
713000
1000
但是它是一种不同的能量
12:12
from anything we've ever seen before.
236
714000
2000
和我们见过的都不一样。
12:14
We call it dark energy,
237
716000
2000
我们叫它暗能量，
12:16
and it has this effect of causing space to expand.
238
718000
3000
而且它有使宇宙扩张的影响。
12:19
But we don't have a good motivation
239
721000
2000
但是我们现在还没有很好的动机
12:21
for putting it in there at this point, OK.
240
723000
2000
去（在数学中）放入这样一项。
12:23
So it's really unexplained as to why we need to put it in.
241
725000
3000
所以，无法解释为什么我们需要放入这样一项。
12:26
Now, so at this point, then, what I want to really emphasize to you,
242
728000
4000
现在，这个时候，我想强调的是，
12:30
is that, first of all, dark matter and dark energy
243
732000
2000
首先，暗物质和暗能量
12:32
are completely different things, OK.
244
734000
2000
是完全不同的东西。
12:34
There are really two mysteries out there as to what makes up most of the universe,
245
736000
4000
它们是宇宙中关于组成成分的两个谜题，
12:38
and they have very different effects.
246
740000
3000
而且它们影响不同。
12:41
Dark matter, because it gravitationally attracts,
247
743000
3000
暗物质，因为它的引力效应，
12:44
it tends to encourage the growth of structure, OK.
248
746000
4000
它倾向于促成固定结构的形成。
12:48
So clusters of galaxies will tend to form,
249
750000
3000
所以这些星系构成的星系团会形成，
12:51
because of all this gravitational attraction.
250
753000
2000
原因是引力作用。
12:53
Dark energy, on the other hand,
251
755000
2000
暗能量，另一方面，
12:55
is putting more and more space between the galaxies,
252
757000
4000
在星系之间产生越来越多的空间。
12:59
makes it, the gravitational attraction between them decrease,
253
761000
3000
使它们之间的引力作用减小，
13:02
and so it impedes the growth of structure.
254
764000
3000
因为它（暗能量）阻碍了固定结构的形成。
13:05
So by looking at things like clusters of galaxies,
255
767000
3000
通过看这些星系的星系团，
13:08
and how they -- their number density,
256
770000
4000
以及它们如何----它们的数密度---
13:12
how many there are as a function of time --
257
774000
2000
---它们的数量以时间为函数，
13:14
we can learn about how dark matter and dark energy
258
776000
4000
我们可以了解暗物质、暗能量
13:18
compete against each other in structure forming.
259
780000
3000
如何在结构的形成上互相竞争。
13:21
In terms of dark matter, I said that we don't have any,
260
783000
3000
在暗物质方面，我说过我们没有任何
13:24
you know, really persuasive argument for dark energy.
261
786000
4000
真正有说服力的论据来解释暗能量。
13:28
Do we have anything for dark matter? And the answer is yes.
262
790000
3000
我们有暗物质的证据嘛？答案是：是的。
13:31
We have well-motivated candidates for the dark matter.
263
793000
3000
我们有非常好的动机给暗能量指定一个候选人。
13:34
Now, what do I mean by well motivated?
264
796000
3000
现在，我指的“好动机”是什么？
13:37
I mean that we have mathematically consistent theories
265
799000
5000
我的意思是说我们有数学上统一的理论
13:42
that were actually introduced
266
804000
2000
被引入
13:44
to explain a completely different phenomenon, OK,
267
806000
3000
去解释一个完全不同的现象
13:47
things that I haven't even talked about,
268
809000
2000
一些我还没有讨论到的现象，
13:49
that each predict the existence
269
811000
3000
（现象）每个预言了
13:52
of a very weakly interacting, new particle.
270
814000
3000
新的弱作用粒子。。
13:55
So, this is exactly what you want in physics:
271
817000
2000
这正是在物理中你想要的：
13:57
where a prediction comes out of a mathematically consistent theory
272
819000
4000
当一个预言从相容的数学理论中推断出来
14:01
that was actually developed for something else.
273
823000
2000
然后实际上被发展用以解释其它东西。
14:03
But we don't know if either of those
274
825000
3000
但是我们不知道是否他们中的一个
14:06
are actually the dark matter candidate, OK.
275
828000
3000
其实是暗物质的候选者。
14:09
One or both, who knows? Or it could be something completely different.
276
831000
3000
一个或者两个都是，谁知道呢？或者它可以使一些完全不同的东西。
14:12
Now, we look for these dark matter particles
277
834000
2000
现在，我们寻找这些暗物质粒子
14:14
because, after all, they are here in the room, OK,
278
836000
3000
因为毕竟它们在这里，在这个房间里，
14:17
and they didn't come in the door.
279
839000
1000
而且它们不进门。
14:18
They just pass through anything.
280
840000
2000
它们仅仅穿越一切。
14:20
They can come through the building, through the Earth --
281
842000
2000
它们穿过建筑，穿过地球；
14:22
they're so non-interacting.
282
844000
2000
它们如此不活泼。
14:24
So one way to look for them is to build detectors
283
846000
3000
所以一种寻找它们的方式是修建探测器
14:27
that are extremely sensitive to a dark matter particle coming through and bumping it.
284
849000
4000
对于暗物质粒子穿过碰撞它极度敏感的探测器。
14:31
So a crystal that will ring if that happens.
285
853000
3000
一种晶体振子在它发生时会振动。
14:34
So one of my colleagues up the road and his collaborators
286
856000
2000
我的一个同事和他的合作者在路边
14:36
have built such a detector.
287
858000
2000
已经修建了一个这样的探测器。
14:38
And they've put it deep down in an iron mine in Minnesota,
288
860000
3000
他们把它（探测器）深深地放在明尼苏达州的底下铁矿中，
14:41
OK, deep under the ground, and in fact, in the last couple of days
289
863000
3000
底下非常深的地方。实际上，在过去的几天里
14:44
announced the most sensitive results so far.
290
866000
3000
至今所公布过的最敏锐的结果显示。
14:47
They haven't seen anything, OK, but it puts limits on what the mass
291
869000
3000
他们没有看到任何东西，但是这给暗物质的质量
14:50
and the interaction strength of these dark matter particles are.
292
872000
3000
以及相互酌强度作了限制。
14:53
There's going to be a satellite telescope launched later this year
293
875000
4000
今年将会有卫星望远镜发射。
14:57
and it will look towards the middle of the galaxy,
294
879000
3000
它将会关注星系中心，
15:00
to see if we can see dark matter particles annihilating
295
882000
2000
以观测是否我们可以看到暗物质湮灭
15:02
and producing gamma rays that could be detected with this.
296
884000
4000
并产生可以用这种方式检测到的γ射线。
15:06
The Large Hadron Collider, a particle physics accelerator,
297
888000
3000
那个大的强子碰撞器，一个粒子物理加速器，
15:09
that we'll be turning on later this year.
298
891000
3000
今年将会开启。
15:12
It is possible that dark matter particles might be produced
299
894000
3000
很可能暗物质离子会产生于
15:15
at the Large Hadron Collider.
300
897000
2000
大的强子碰撞机。
15:17
Now, because they are so non-interactive,
301
899000
1000
现在，因为它们如此不活泼，
15:18
they will actually escape the detector,
302
900000
3000
他们其实将会逃离探测器，
15:21
so their signature will be missing energy, OK.
303
903000
3000
所以，它们的署名将会是丢失的能量。
15:24
Now, unfortunately, there is a lot of new physics
304
906000
3000
不幸的是，很多新的物理量
15:27
whose signature could be missing energy,
305
909000
2000
它们（物理量）可以代表能量损失，
15:29
so it will be hard to tell the difference.
306
911000
2000
所以，很难辨别它们（代表能量损失的物理量）。
15:31
And finally, for future endeavors, there are telescopes being designed
307
913000
5000
最终，关于未来的努力，现在有设计的望远镜
15:36
specifically to address the questions of dark matter and dark energy --
308
918000
4000
专门研究暗物质和暗能量：
15:40
ground-based telescopes, and there are three space-based telescopes
309
922000
3000
一些地面望远镜。而且现在又3架以空间为基地的望远镜
15:43
that are in competition right now
310
925000
2000
现在正在竞争
15:45
to be launched to investigate dark matter and dark energy.
311
927000
3000
被发射以研究暗物质和暗能量。
15:48
So in terms of the big questions:
312
930000
2000
所以，关于这些大问题：
15:50
what is dark matter? What is dark energy?
313
932000
2000
什么是暗物质？什么是暗能量?
15:52
The big questions facing physics.
314
934000
2000
是物理学面对的大问题。
15:54
And I'm sure you have lots of questions,
315
936000
3000
而且，我确定你们有很多问题。
15:57
which I very much look forward to addressing
316
939000
2000
我期待着在接下来的
15:59
over the next 72 hours, while I'm here. Thank you.
317
941000
2000
我在这里的72小时讨论它们（问题）。好的。谢谢。
16:01
(Applause)
318
943000
3000
（掌声）
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