Patricia Burchat: Shedding light on dark matter

翻译人员: Donghua Lin 校对人员: Wang Qian

As a particle physicist, I study the elementary particles

作为一名粒子物理学家，我研究基本粒子

and how they interact on the most fundamental level.

以及它们如何在微观上如何相互作用

For most of my research career, I've been using accelerators,

对于我大部分的研究，我一直在使用加速器，

such as the electron accelerator at Stanford University, just up the road,

例如在斯坦福大学路边的电子加速器

to study things on the smallest scale.

去在微观上研究物质。

But more recently, I've been turning my attention

但是最近，我的注意力转向了

to the universe on the largest scale.

宏观上整个宇宙。

Because, as I'll explain to you,

因为，正如我将要对你们解释的，

the questions on the smallest and the largest scale are actually very connected.

宏观和微观上的问题其实是非常相关的。

So I'm going to tell you about our twenty-first-century view of the universe,

所以我将要告诉你们关于我们21世纪的宇宙观，

what it's made of and what the big questions in the physical sciences are --

它是由什么构成的，以及什么是物理学中的一些大问题---

at least some of the big questions.

至少是它们中的一些大问题。

So, recently, we have realized

最近，我们意识到

that the ordinary matter in the universe --

宇宙中的普通物质---

and by ordinary matter, I mean you, me,

我指的普通物质，我的意思是你，我

the planets, the stars, the galaxies --

行星，横星，银河系---

the ordinary matter makes up only a few percent

普通物质仅仅占据

of the content of the universe.

宇宙组成的一小部分。

Almost a quarter, or approximately a quarter

近乎四分之一，或者大约四分之一

of the matter in the universe, is stuff that's invisible.

的宇宙组成是一些不可见的东西。

By invisible, I mean it doesn't absorb in the electromagnetic spectrum.

不可见，我指的是它不吸收地磁波谱。

It doesn't emit in the electromagnetic spectrum. It doesn't reflect.

在光谱中不放射电磁波。它不反射电磁波。

It doesn't interact with the electromagnetic spectrum,

它在电磁波谱照射下不发生反应，

which is what we use to detect things.

而这却是我们如何用来检测物质的方法。

It doesn't interact at all. So how do we know it's there?

它根本不反应。所以我们如何知道它们在那？

We know it's there by its gravitational effects.

我的得知它们存在通过引力效应。

In fact, this dark matter dominates

实际上，这种暗物质

the gravitational effects in the universe on a large scale,

宏观上统治宇宙中的引力效应，

and I'll be telling you about the evidence for that.

我将会告诉你们它的证据。

What about the rest of the pie?

派的其它部分是什么呢？

The rest of the pie is a very mysterious substance called dark energy.

这个派的其它部分是一种十分神秘的物质，叫做暗能量。

More about that later, OK.

一会再讨论它。

So for now, let's turn to the evidence for dark matter.

所以现在，我们来谈谈暗物质存在的证据。

In these galaxies, especially in a spiral galaxy like this,

在这些星系中，尤其是在一个像这样的螺旋星系中，

most of the mass of the stars is concentrated in the middle of the galaxy.

大部分的质量集中在星系的中央。

This huge mass of all these stars keeps stars in circular orbits in the galaxy.

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。

So we have these stars going around in circles like this.

所以我们看到这些恒星沿圆圈这样运动。

As you can imagine, even if you know physics, this should be intuitive, OK --

如你所想，即使你不知道物理----这应该是很直观的，

that stars that are closer to the mass in the middle will be rotating at a higher speed

这些靠近中心的恒星将会以更高的速度旋转，

than those that are further out here, OK.

相比于在外面的这些。

So what you would expect is that if you measured the orbital speed of the stars,

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，

that they should be slower on the edges than on the inside.

它们（速度）应该是边缘的比里面的慢。

In other words, if we measured speed as a function of distance --

换言之，如果我们测量速度作为距离的函数---

this is the only time I'm going to show a graph, OK --

这是我唯一一次展示图表，好吗？

we would expect that it goes down as the distance increases

我们会期待它（速度）会减小

from the center of the galaxy.

随着距离星系中央的路程增加。

When those measurements are made,

当这些被测量，

instead what we find is that the speed is basically constant,

反而，我们发现这个速度基本上是一个常数，

as a function of distance.

作为距离的函数。

If it's constant, that means that the stars out here

如果它（速度）是一个常数，这意味着外面的恒星

are feeling the gravitational effects of matter that we do not see.

正在感受到一些我们看不到物质所施加的引力效应。

In fact, this galaxy and every other galaxy

事实上，这个星系以及每一个其它的星系

appears to be embedded in a cloud of this invisible dark matter.

似乎被内嵌在一团我们看不到的暗物质中。

And this cloud of matter is much more spherical than the galaxy themselves,

这团物质比星系本身更加类似于球形，

and it extends over a much wider range than the galaxy.

而且它们（暗物质）比星系本身延伸至更广的范围。

So we see the galaxy and fixate on that, but it's actually a cloud of dark matter

所以，我们注视着这个星系，但是它其实实在一团

that's dominating the structure and the dynamics of this galaxy.

决定它们结构与动态的暗物质中。

Galaxies themselves are not strewn randomly in space;

星系本身并不是任意地散布在空间中；

they tend to cluster.

它们趋向于聚集在一起。

And this is an example of a very, actually, famous cluster, the Coma cluster.

这是一个实际上非常著名的星系团：后发座（Coma）星系团。

And there are thousands of galaxies in this cluster.

而且这个星系团中有数以千计的星系。

They're the white, fuzzy, elliptical things here.

它们是这些白色的，模糊的，椭圆的东西。

So these galaxy clusters -- we take a snapshot now,

所以，这些星系团——我们现在拍一张照，

we take a snapshot in a decade, it'll look identical.

十年后我们拍一张照——它们将会看起来一模一样。

But these galaxies are actually moving at extremely high speeds.

但是这些星系团其实在以极高的速度运动。

They're moving around in this gravitational potential well of this cluster, OK.

它们其实在这个星系团的引力势阱中运动。

So all of these galaxies are moving.

所以，这些星系在运动。

We can measure the speeds of these galaxies, their orbital velocities,

我们可以测量这些星系的速率，它们的轨道速度，

and figure out how much mass is in this cluster.

并算出星系团中有多少质量。

And again, what we find is that there is much more mass there

并且再一次，我们发现的这里有更多的质量

than can be accounted for by the galaxies that we see.

相比于我们实际看到的星系所能证明的。

Or if we look in other parts of the electromagnetic spectrum,

或者我们看其它部分的电磁波谱，

we see that there's a lot of gas in this cluster, as well.

我们看到这里也有很多气体。

But that cannot account for the mass either.

但是那也不能解释这些质量。

In fact, there appears to be about ten times as much mass here

事实上，这里有大约10倍多的质量

in the form of this invisible or dark matter

以暗物质存在

as there is in the ordinary matter, OK.

相比于普通物质。

It would be nice if we could see this dark matter a little bit more directly.

如果我们能更直接地看到暗物质，那会更好

I'm just putting this big, blue blob on there, OK,

我只放一个大的蓝色的水泡在这里，

to try to remind you that it's there.

试图提醒你它们（暗物质）在这里。

Can we see it more visually? Yes, we can.

我们能更形象地看到它们嘛？是的，我们可以。

And so let me lead you through how we can do this.

那么让我帮助你们了解如何这样做。

So here's an observer:

那么这里是一个观察器：

it could be an eye; it could be a telescope.

它可以是一只眼睛；它可以是一个望远镜。

And suppose there's a galaxy out here in the universe.

假设在宇宙中有一个星系。

How do we see that galaxy?

我们如何能看到那个星系？

A ray of light leaves the galaxy and travels through the universe

一束光离开星系并穿过宇宙

for perhaps billions of years

经过了也许几十亿年

before it enters the telescope or your eye.

在它进入望远镜或者你的眼睛之前。

Now, how do we deduce where the galaxy is?

现在，你如何猜测星系的位置？

Well, we deduce it by the direction that the ray is traveling

嗯，我们猜测它的位置根据光线传播

as it enters our eye, right?

进入我们眼睛的方向？

We say, the ray of light came this way;

例如，这束光这样出来，

the galaxy must be there, OK.

星系一定在那。

Now, suppose I put in the middle a cluster of galaxies --

现在，假设我在屏幕中央放一个星系团---

and don't forget the dark matter, OK.

别忘了还有暗物质，好吗？

Now, if we consider a different ray of light, one going off like this,

现在，如果我们考虑另外一束像这样离开的光线，

we now need to take into account

我们现在需要考虑

what Einstein predicted when he developed general relativity.

爱因斯坦当他发展广义相对论的时候，曾经预言过的（现象）。

And that was that the gravitational field, due to mass,

那就是由于有质量，引力场

will deflect not only the trajectory of particles,

不仅会使粒子的运动轨迹偏转，

but will deflect light itself.

而且会使光本身偏转。

So this light ray will not continue in a straight line,

所以这束光不会沿直线行进，

but would rather bend and could end up going into our eye.

相反会弯曲然后最终进入我们的眼睛

Where will this observer see the galaxy?

这个观察器会在哪里看到星系呢？

You can respond. Up, right?

你们可以回答我。上面，对吗？

We extrapolate backwards and say the galaxy is up here.

我们倒推然后确定星系在这里。

Is there any other ray of light

这里还有其它的

that could make into the observer's eye from that galaxy?

可以进入观察者眼睛的光线嘛？

Yes, great. I see people going down like this.

是的，非常好。我看到人们做向下的姿势。

So a ray of light could go down, be bent

一束光也可以往下走，然后弯曲

up into the observer's eye,

进入观察者的眼睛，

and the observer sees a ray of light here.

这个观察着便会在这里看到一束光。

Now, take into account the fact that we live in

现在，考虑我们生活在

a three-dimensional universe, OK,

三维宇宙的事实

a three-dimensional space.

一个三维空间。

Are there any other rays of light that could make it into the eye?

还有其它光线可以进入我们的眼睛嘛？

Yes! The rays would lie on a -- I'd like to see -- yeah, on a cone.

是的，光线可以排列在一个---我希望看到---对了，一个圆锥形

So there's a whole ray of light -- rays of light on a cone --

所以，许多束光会在一个圆锥上---

that will all be bent by that cluster

它们都被弯曲过

and make it into the observer's eye.

然后进入观察者的眼睛。

If there is a cone of light coming into my eye, what do I see?

如果有锥形的光进入我的眼睛，我看到了什么？

A circle, a ring. It's called an Einstein ring. Einstein predicted that, OK.

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

Now, it will only be a perfect ring if the source, the deflector

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

and the eyeball, in this case, are all in a perfectly straight line.

以及我们的眼球，在这个情况下，恰好在一条直线上。

If they're slightly skewed, we'll see a different image.

如果它们被略微偏转，我们将会看到一个不同的图像

Now, you can do an experiment tonight over the reception, OK,

你们今晚在招待会后可以做一个试验，

to figure out what that image will look like.

去看到这个图像会是什么样子。

Because it turns out that there is a kind of lens that we can devise,

因为我们可以设计一种透镜，

that has the right shape to produce this kind of effect.

它（透镜）有产生这种现象的合适的形状。

We call this gravitational lensing.

我们称它为引力透镜。

And so, this is your instrument, OK.

所以，这是你们的仪器

(Laughter).

（笑声）

But ignore the top part.

但是忽略上部。

It's the base that I want you to concentrate, OK.

我希望你们关注它的底座。

So, actually, at home, whenever we break a wineglass,

所以实际上，在家里，不管何时我们打碎一个玻璃酒杯，

I save the bottom, take it over to the machine shop.

我保留它的底部，把它送去机械修理店。

We shave it off, and I have a little gravitational lens, OK.

我们把它剃掉，然后我就有了一个引力透镜。

So it's got the right shape to produce the lensing.

所以，它有合适产生透镜效果的形状。

And so the next thing you need to do in your experiment

所以，你在实验中需要做的下一件事情，

is grab a napkin. I grabbed a piece of graph paper -- I'm a physicist. (Laughter)

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）

So, a napkin. Draw a little model galaxy in the middle.

那么，一张餐巾纸。在中间画一个小小的星系模型。

And now put the lens over the galaxy,

然后现在把透镜放到星系上，

and what you'll find is that you'll see a ring, an Einstein ring.

你将看到的是，一个爱因斯坦环。

Now, move the base off to the side,

现在，把底座移到另一边，

and the ring will split up into arcs, OK.

然后，这个圆环会分裂成一些弧形。

And you can put it on top of any image.

你可以把它放到任何图像上。

On the graph paper, you can see

在坐标纸上你可以看到

how all the lines on the graph paper have been distorted.

这些线是如何被扭曲的。

And again, this is a kind of an accurate model

再一次说明，这是一种非常精确的模型

of what happens with the gravitational lensing.

去解释引力透镜产生的现象。

OK, so the question is: do we see this in the sky?

那么，问题是：我们在天空中看到这个吗？

Do we see arcs in the sky when we look at, say, a cluster of galaxies?

当我们看一个星系团的时候，我们能看到弧形吗？

And the answer is yes.

答案是:是的。

And so, here's an image from the Hubble Space Telescope.

这是来自哈勃望远镜的图像。

Many of the images you are seeing

你看到的许多图像

are earlier from the Hubble Space Telescope.

来自早期的哈勃望远镜。

Well, first of all, for the golden shape galaxies --

嗯，首先，关于这些金色的星系---

those are the galaxies in the cluster.

它们是在星系团中的一些星系。

They're the ones that are embedded in that sea of dark matter

它们嵌在一团暗物质中

that are causing the bending of the light

因而引起了光的弯曲

to cause these optical illusions, or mirages, practically,

引起了这些视错觉，或者差不多，蜃景，

of the background galaxies.

来自后面的星系。

So the streaks that you see, all these streaks,

所以你看到条纹，所有这些条纹，

are actually distorted images of galaxies that are much further away.

其实都是更远出的扭曲的星系的图像。

So what we can do, then, is based on how much distortion

那么我们能做的，就是根据扭曲程度的大小

we see in those images, we can calculate how much mass

来自这些图像，我们可以计算出

there must be in this cluster.

在这团星系中一定有多少质量。

And it's an enormous amount of mass.

质量的总额是十分庞大的。

And also, you can tell by eye, by looking at this,

所以，你可以通过观察它（图像），辨别

that these arcs are not centered on individual galaxies.

这些弧线的中心不是某一个星系；

They are centered on some more spread out structure,

它们（弧线）以一个更加扩散的的结构为中心。

and that is the dark matter

这就是暗物质

in which the cluster is embedded, OK.

星系嵌入其中。

So this is the closest you can get to kind of seeing

这是最接近于看到

at least the effects of the dark matter with your naked eye.

至少通过肉眼看到暗物质的影响。

OK, so, a quick review then, to see that you're following.

那么，一个非常快的回顾，以知道你们正在跟随。

So the evidence that we have

我们有的证据

that a quarter of the universe is dark matter --

证明这¼是暗物质---

this gravitationally attracting stuff --

这些以引力作用吸引的东西---

is that galaxies, the speed with which stars orbiting galaxies

（证据）是这些行星围绕星系运动的速率

is much too large; it must be embedded in dark matter.

（速率）过大；它（行星）一定嵌在暗物质中

The speed with which galaxies within clusters are orbiting is much too large;

星系在星系团中的圆周运动速度太大了；

it must be embedded in dark matter.

它（星系）一定嵌在暗物质中

And we see these gravitational lensing effects, these distortions

我们看到了这些引力透镜的效应。这些扭曲（的现象）

that say that, again, clusters are embedded in dark matter.

再次证明，星系团嵌在暗物质中。

OK. So now, let's turn to dark energy.

好。现在我们转向暗能量。

So to understand the evidence for dark energy, we need to discuss something

所以为了了解暗能量的证据，我们需要讨论一些

that Stephen Hawking referred to in the previous session.

史蒂芬霍金前一段谈到的现象。

And that is the fact that space itself is expanding.

那就是宇宙正在扩张的事实。

So if we imagine a section of our infinite universe --

所以如果我们想象无限宇宙中一小部分，

and so I've put down four spiral galaxies, OK --

然后我放4个漩涡星系，

and imagine that you put down a set of tape measures,

假设你放一套卷尺，

so every line on here corresponds to a tape measure,

这里的每一条线对以一个卷尺---

horizontal or vertical, for measuring where things are.

水平的或垂直的---用来测量东西的位置。

If you could do this, what you would find

如果你可以这样做，你将发现的是

that with each passing day, each passing year,

每过去一天，每过去一年，

each passing billions of years, OK,

每过去几十亿年

the distance between galaxies is getting greater.

星系间的距离正在变得更大。

And it's not because galaxies are moving

然而这并不是因为星系在运动

away from each other through space.

在空间中互相远离；

They're not necessarily moving through space.

他们不一定在动。

They're moving away from each other

他们正在远离对方

because space itself is getting bigger, OK.

因为空间本身正在扩张。

That's what the expansion of the universe or space means.

这是宇宙或者空间扩张的意思。

So they're moving further apart.

所以他们正运动地越来越远。

Now, what Stephen Hawking mentioned, as well,

史蒂芬霍金也提到的，

is that after the Big Bang, space expanded at a very rapid rate.

在大爆炸之后，宇宙空间以非常快的速率扩张。

But because gravitationally attracting matter

但是因为制造引力的物质

is embedded in this space,

嵌在这个空间中，

it tends to slow down the expansion of the space, OK.

它（暗物质）倾向于减慢空间扩张的速率。

So the expansion slows down with time.

所以扩张的速率随着时间减慢。

So, in the last century, OK, people debated

所以，上个世纪，人们辩论

about whether this expansion of space would continue forever;

宇宙是否会永远扩张，

whether it would slow down, you know,

是否会减慢，

will be slowing down, but continue forever;

或者是否会减慢，但是永远进行。

slow down and stop, asymptotically stop;

或者减慢并停止，接近停止。

or slow down, stop, and then reverse, so it starts to contract again.

或者减慢，停止，然后在颠倒，再重新收缩。

So a little over a decade ago,

所以十多年后，

two groups of physicists and astronomers

两组物理学家和天文学家

set out to measure the rate at which

着手测量

the expansion of space was slowing down, OK.

宇宙减速扩张的速率。

By how much less is it expanding today,

通过它今天少扩张了多少，

compared to, say, a couple of billion years ago?

用于和几十亿年前比较。

The startling answer to this question, OK, from these experiments,

这个问题的令人吃惊的答案是，根据这些实验，

was that space is expanding at a faster rate today

宇宙本身今天正在以更快的速率扩张，

than it was a few billion years ago, OK.

相比于几十亿年前。

So the expansion of space is actually speeding up.

所以宇宙空间的扩张正在加速。

This was a completely surprising result.

这是完全令人惊讶的结果。

There is no persuasive theoretical argument for why this should happen, OK.

没有令人信服的理论依据解释为什么这会发生。

No one was predicting ahead of time this is what's going to be found.

没有人事先预言了什么将会被发现。

It was the opposite of what was expected.

它（实验结果）和我们的期望是相反的。

So we need something to be able to explain that.

所以我们需要一些东西去解释它。

Now it turns out, in the mathematics,

现在，在数学中，

you can put it in as a term that's an energy,

你可以放入一项成为能量。

but it's a completely different type of energy

但是它是一种不同的能量

from anything we've ever seen before.

和我们见过的都不一样。

We call it dark energy,

我们叫它暗能量，

and it has this effect of causing space to expand.

而且它有使宇宙扩张的影响。

But we don't have a good motivation

但是我们现在还没有很好的动机

for putting it in there at this point, OK.

去（在数学中）放入这样一项。

So it's really unexplained as to why we need to put it in.

所以，无法解释为什么我们需要放入这样一项。

Now, so at this point, then, what I want to really emphasize to you,

现在，这个时候，我想强调的是，

is that, first of all, dark matter and dark energy

首先，暗物质和暗能量

are completely different things, OK.

是完全不同的东西。

There are really two mysteries out there as to what makes up most of the universe,

它们是宇宙中关于组成成分的两个谜题，

and they have very different effects.

而且它们影响不同。

Dark matter, because it gravitationally attracts,

暗物质，因为它的引力效应，

it tends to encourage the growth of structure, OK.

它倾向于促成固定结构的形成。

So clusters of galaxies will tend to form,

所以这些星系构成的星系团会形成，

because of all this gravitational attraction.

原因是引力作用。

Dark energy, on the other hand,

暗能量，另一方面，

is putting more and more space between the galaxies,

在星系之间产生越来越多的空间。

makes it, the gravitational attraction between them decrease,

使它们之间的引力作用减小，

and so it impedes the growth of structure.

因为它（暗能量）阻碍了固定结构的形成。

So by looking at things like clusters of galaxies,

通过看这些星系的星系团，

and how they -- their number density,

以及它们如何----它们的数密度---

how many there are as a function of time --

---它们的数量以时间为函数，

we can learn about how dark matter and dark energy

我们可以了解暗物质、暗能量

compete against each other in structure forming.

如何在结构的形成上互相竞争。

In terms of dark matter, I said that we don't have any,

在暗物质方面，我说过我们没有任何

you know, really persuasive argument for dark energy.

真正有说服力的论据来解释暗能量。

Do we have anything for dark matter? And the answer is yes.

我们有暗物质的证据嘛？答案是：是的。

We have well-motivated candidates for the dark matter.

我们有非常好的动机给暗能量指定一个候选人。

Now, what do I mean by well motivated?

现在，我指的“好动机”是什么？

I mean that we have mathematically consistent theories

我的意思是说我们有数学上统一的理论

that were actually introduced

被引入

to explain a completely different phenomenon, OK,

去解释一个完全不同的现象

things that I haven't even talked about,

一些我还没有讨论到的现象，

that each predict the existence

（现象）每个预言了

of a very weakly interacting, new particle.

新的弱作用粒子。。

So, this is exactly what you want in physics:

这正是在物理中你想要的：

where a prediction comes out of a mathematically consistent theory

当一个预言从相容的数学理论中推断出来

that was actually developed for something else.

然后实际上被发展用以解释其它东西。

But we don't know if either of those

但是我们不知道是否他们中的一个

are actually the dark matter candidate, OK.

其实是暗物质的候选者。

One or both, who knows? Or it could be something completely different.

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。

Now, we look for these dark matter particles

现在，我们寻找这些暗物质粒子

because, after all, they are here in the room, OK,

因为毕竟它们在这里，在这个房间里，

and they didn't come in the door.

而且它们不进门。

They just pass through anything.

它们仅仅穿越一切。

They can come through the building, through the Earth --

它们穿过建筑，穿过地球；

they're so non-interacting.

它们如此不活泼。

So one way to look for them is to build detectors

所以一种寻找它们的方式是修建探测器

that are extremely sensitive to a dark matter particle coming through and bumping it.

对于暗物质粒子穿过碰撞它极度敏感的探测器。

So a crystal that will ring if that happens.

一种晶体振子在它发生时会振动。

So one of my colleagues up the road and his collaborators

我的一个同事和他的合作者在路边

have built such a detector.

已经修建了一个这样的探测器。

And they've put it deep down in an iron mine in Minnesota,

他们把它（探测器）深深地放在明尼苏达州的底下铁矿中，

OK, deep under the ground, and in fact, in the last couple of days

底下非常深的地方。实际上，在过去的几天里

announced the most sensitive results so far.

至今所公布过的最敏锐的结果显示。

They haven't seen anything, OK, but it puts limits on what the mass

他们没有看到任何东西，但是这给暗物质的质量

and the interaction strength of these dark matter particles are.

以及相互酌强度作了限制。

There's going to be a satellite telescope launched later this year

今年将会有卫星望远镜发射。

and it will look towards the middle of the galaxy,

它将会关注星系中心，

to see if we can see dark matter particles annihilating

以观测是否我们可以看到暗物质湮灭

and producing gamma rays that could be detected with this.

并产生可以用这种方式检测到的γ射线。

The Large Hadron Collider, a particle physics accelerator,

那个大的强子碰撞器，一个粒子物理加速器，

that we'll be turning on later this year.

今年将会开启。

It is possible that dark matter particles might be produced

很可能暗物质离子会产生于

at the Large Hadron Collider.

大的强子碰撞机。

Now, because they are so non-interactive,

现在，因为它们如此不活泼，

they will actually escape the detector,

他们其实将会逃离探测器，

so their signature will be missing energy, OK.

所以，它们的署名将会是丢失的能量。

Now, unfortunately, there is a lot of new physics

不幸的是，很多新的物理量

whose signature could be missing energy,

它们（物理量）可以代表能量损失，

so it will be hard to tell the difference.

所以，很难辨别它们（代表能量损失的物理量）。

And finally, for future endeavors, there are telescopes being designed

最终，关于未来的努力，现在有设计的望远镜

specifically to address the questions of dark matter and dark energy --

专门研究暗物质和暗能量：

ground-based telescopes, and there are three space-based telescopes

一些地面望远镜。而且现在又3架以空间为基地的望远镜

that are in competition right now

现在正在竞争

to be launched to investigate dark matter and dark energy.

被发射以研究暗物质和暗能量。

So in terms of the big questions:

所以，关于这些大问题：

what is dark matter? What is dark energy?

什么是暗物质？什么是暗能量?

The big questions facing physics.

是物理学面对的大问题。

And I'm sure you have lots of questions,

而且，我确定你们有很多问题。

which I very much look forward to addressing

我期待着在接下来的

over the next 72 hours, while I'm here. Thank you.

我在这里的72小时讨论它们（问题）。好的。谢谢。

(Applause)

（掌声）