What the discovery of gravitational waves means | Allan Adams

翻译人员: Yan Ge 校对人员: Huazhe Xie

1.3 billion years ago,

13亿年前，

in a distant, distant galaxy,

在一个无比遥远的星系，

two black holes locked into a spiral,

两个黑洞陷入了一个漩涡之中，

falling inexorably towards each other

以不可阻挡之势冲向彼此，

and collided,

然后相撞，

converting three Suns' worth of stuff

由此将等同于三个太阳的物质

into pure energy in a tenth of a second.

在十分之一秒内转化成了纯能量。

For that brief moment in time,

在那短暂的一瞬间，

the glow was brighter than all the stars

碰撞产生的光芒

in all the galaxies

令已知宇宙中所有星系中的

in all of the known Universe.

所有恒星都黯然失色。

It was a very

那是一个名副其实的

big

大——

bang.

爆炸。

But they didn't release their energy in light.

然而它们并没有 以光的形式释放能量。

I mean, you know, they're black holes.

因为它们是黑洞。

All that energy was pumped into the fabric of space and time itself,

所有产生的能量 都被注入时间和空间本身，

making the Universe explode in gravitational waves.

使宇宙以引力波的形式延展。

Let me give you a sense of the timescale at work here.

让我来对所涉及的 时间标度做一下说明。

1.3 billion years ago,

13亿年前，

Earth had just managed to evolve multicellular life.

地球上刚出现了多细胞生物。

Since then, Earth has made and evolved

在那之后，地球上的生物不断进化，

corals, fish, plants, dinosaurs, people and even -- God save us -- the Internet.

珊瑚、鱼类、植物、恐龙、人类相继出现， 当然，还有互联网。

And about 25 years ago,

大约25年前，

a particularly audacious set of people --

一群极具冒险精神的人，

Rai Weiss at MIT, Kip Thorne and Ronald Drever at Caltech --

麻省理工学院的瑞伊·维斯，

以及加州理工学院的 奇普·索恩和罗纳德·德雷弗，

产生了一个他们认为 非常了不起的想法：

decided that it would be really neat

to build a giant laser detector

他们想要制造 一台庞大的激光探测器，

with which to search for the gravitational waves

来搜寻由黑洞撞击等产生的引力波。

from things like colliding black holes.

Now, most people thought they were nuts.

大多数人都觉得他们疯了。

But enough people realized that they were brilliant nuts

但也有很多人认为 他们是了不起的疯子，

that the US National Science Foundation decided to fund their crazy idea.

所以美国国家科学基金会决定 为他们这一疯狂的想法提供资金支持。

So after decades of development,

由此，经历了这几十年的发展，

construction and imagination

通过不断的建设和构想，

and a breathtaking amount of hard work,

以及惊人数量的辛勤工作，

they built their detector, called LIGO:

他们最终建成了这台 名为LIGO的探测器：

The Laser Interferometer Gravitational-Wave Observatory.

全称叫做“激光干涉引力波观测台”。

For the last several years,

在过去的几年中，

LIGO's been undergoing a huge expansion in its accuracy,

LIGO的准确性得到了巨大的提升，

a tremendous improvement in its detection ability.

其探测能力也有了惊人的进步。

It's now called Advanced LIGO as a result.

所以现在它可以被称为“高端LIGO”。

In early September of 2015,

2015年9月初，

LIGO turned on for a final test run

LIGO进行了最后一次试运行，

while they sorted out a few lingering details.

辨识出了少量滞留的细节。

And on September 14 of 2015,

随后，在2015年9月14日，

just days after the detector had gone live,

即探测器正式运行数天后，

the gravitational waves from those colliding black holes

由黑洞撞击所产生的引力波

passed through the Earth.

经过了地球。

And they passed through you and me.

它经过了我们每一个人。

And they passed through the detector.

它也经过了那台探测器。

(Audio) Scott Hughes: There's two moments in my life

（音频）斯科特·休斯： 在我生命中只有两个时刻

给予过我比这更为强烈的情感冲击。

more emotionally intense than that.

一个是我女儿出生的时候。

One is the birth of my daughter.

The other is when I had to say goodbye to my father when he was terminally ill.

另一个是我父亲病逝前 我与他告别的时候。

You know, it was the payoff of my career, basically.

可以说我从事这项事业就是为了这一刻，

Everything I'd been working on -- it's no longer science fiction! (Laughs)

我为其付出努力的事情 都不再是科幻小说了！（大笑）

Allan Adams: So that's my very good friend and collaborator, Scott Hughes,

艾伦·亚当斯： 这是我的好友兼合作伙伴，

斯科特·休斯， 麻省理工学院理论物理学家，

a theoretical physicist at MIT,

who has been studying gravitational waves from black holes

他研究产生于黑洞的引力波

and the signals that they could impart on observatories like LIGO,

以及其传递给 像LIGO这样的观测台的信号

for the past 23 years.

已经有23年之久。

So let me take a moment to tell you what I mean by a gravitational wave.

现在让我来简单介绍一下 什么是引力波。

A gravitational wave is a ripple

引力波是以时间和

in the shape of space and time.

空间的形式产生的波动。

As the wave passes by,

当引力波通过时，

it stretches space and everything in it

它将空间及其中的所有事物

in one direction,

向同一方向拉伸，

and compresses it in the other.

同时将其在另一方向上压缩。

This has led to countless instructors of general relativity

这使得许多广义相对论教授

doing a really silly dance to demonstrate in their classes on general relativity.

在课堂上说明广义相对论时 都跳起了滑稽的舞蹈，

"It stretches and expands, it stretches and expands."

“拉伸再扩展，拉伸再扩展。”

So the trouble with gravitational waves

研究引力波的难点在于

is that they're very weak; they're preposterously weak.

它们太微弱了； 微弱得不合常理。

For example, the waves that hit us on September 14 --

就拿9月14日穿过我们的引力波为例，

and yes, every single one of you stretched and compressed

确实，在其作用下， 我们每一个人都被

under the action of that wave --

拉伸和压缩了——

when the waves hit, they stretched the average person

但这个过程中平均每个人仅被拉伸了

by one part in 10 to the 21.

10的21次方分之一。

That's a decimal place, 20 zeroes,

也就是小数点后20个零，

and a one.

再加1个一。

That's why everyone thought the LIGO people were nuts.

这就是为什么 人们认为LIGO的研究者们都是疯子。

Even with a laser detector five kilometers long -- and that's already crazy --

即使使用5千米长的激光探测器， ——这本身就很疯狂，

they would have to measure the length of those detectors

他们还是需要以比原子核半径的

to less than one thousandth of the radius of the nucleus

千分之一还小的单位来测量那些

of an atom.

探测器的长度。

And that's preposterous.

这真是超乎常人所能想象。

So towards the end of his classic text on gravity,

在其关于万有引力的 经典著作的末尾，

LIGO co-founder Kip Thorne

LIGO的联合发明人奇普·索恩

described the hunt for gravitational waves as follows:

对引力波的探索进行了如下描述，

He said, "The technical difficulties to be surmounted

他说：“要建成这样的探测器，

in constructing such detectors

需要克服巨大的

技术难题。

are enormous.

But physicists are ingenious,

但是，物理学家都是天才，

and with the support of a broad lay public,

再加上公众的广泛支持，

all obstacles will surely be overcome."

所有的难关都会被攻克。”

Thorne published that in 1973,

这本著作出版于1973年，

42 years before he succeeded.

42年后，他才获得了成功。

Now, coming back to LIGO,

让我们回到LIGO的话题上来，

Scott likes to say that LIGO acts like an ear

斯科特总是说，

LIGO的运作方式 更像是耳朵而非眼睛。

more than it does like an eye.

I want to explain what that means.

让我来解释一下这句话的意思。

Visible light has a wavelength, a size,

可见光的波长

比我们身边的事物都要短，

that's much smaller than the things around you,

the features on people's faces,

比如人的五官，

the size of your cell phone.

或是你们的手机。

And that's really useful,

这样的波长非常有用处，

because it lets you make an image or a map of the things around you,

因为它令人们借助来自

身边场景的不同位置的光线，

by looking at the light coming from different spots

in the scene about you.

获得周围事物的直观影像。

Sound is different.

声音就不同了。

Audible sound has a wavelength that can be up to 50 feet long.

人们能听到的声音的波长 可以达到50英尺。

And that makes it really difficult --

这使得声音很难——

in fact, in practical purposes, impossible -- to make an image

事实上，从实用意义来讲， 根本不可能，

of something you really care about.

去形成你所在意的事物的直观影像。

Your child's face.

比如你的孩子长什么样子。

Instead, we use sound to listen for features like pitch

相反，我们通过声音

来辨识音高、声调、节奏、音量等特征，

and tone and rhythm and volume

to infer a story behind the sounds.

以此来推断声音背后的故事。

That's Alice talking.

爱丽丝正在讲话。

That's Bob interrupting.

鲍勃插话进来了。

Silly Bob.

鲍勃真是不分场合。

So, the same is true of gravitational waves.

引力波也有同样的作用。

We can't use them to make simple images of things out in the Universe.

我们虽然不能通过引力波 获得宇宙中事物的直观影像，

But by listening to changes

但通过倾听

in the amplitude and frequency of those waves,

引力波振幅和频率的变化，

we can hear the story that those waves are telling.

我们能够听出它们所传达的故事。

And at least for LIGO,

至少LIGO接收到的

the frequencies that it can hear are in the audio band.

波频在人们能听到的范围内。

所以，如果我们把波形 转化为压力波和空气波，即声音，

So if we convert the wave patterns into pressure waves and air, into sound,

we can literally hear the Universe speaking to us.

我们就能确实地听到 宇宙传达给我们的信息。

For example, listening to gravity, just in this way,

比如，以这种形式倾听引力波，

can tell us a lot about the collision of two black holes,

我们就能获得很多 有关两个黑洞撞击的信息，

something my colleague Scott has spent an awful lot of time thinking about.

这也是我的同事斯科特 花了大量时间探索的事情。

(Audio) SH: If the two black holes are non-spinning,

（音频）斯科特： 如果两个黑洞没有旋转，

你听到的是“嗡——”一声鸣响。

you get a very simple chirp: whoop!

If the two bodies are spinning very rapidly, I have that same chirp,

如果这两个黑洞高速旋转， 响声是相同的，

but with a modulation on top of it,

但调制却发生了变化，

so it kind of goes: whir, whir, whir!

听起来就像这样：嗡——嗡——嗡——

It's sort of the vocabulary of spin imprinted on this waveform.

可以说这就是旋转 在波形图上留下的只言片语。

AA: So on September 14, 2015,

艾伦：在2015年9月14日，

a date that's definitely going to live in my memory,

一个我将永远铭记的日子，

LIGO heard this:

LIGO听到了这样的声音：

[Whirring sound]

（嗡鸣声）

So if you know how to listen, that is the sound of --

懂得如何倾听它的人知道， 这个声音来自——

(Audio) SH: ... two black holes, each of about 30 solar masses,

斯科特： ......两个质量均为太阳30倍左右的黑洞，

that were whirling around at a rate

以相当于搅拌机运转的速度

comparable to what goes on in your blender.

旋转时所发出的声音。

AA: It's worth pausing here to think about what that means.

艾伦：我们有必要停下来好好想想 这意味着什么。

Two black holes, the densest thing in the Universe,

两个黑洞， 宇宙中密度最高的物体，

one with a mass of 29 Suns

其中一个的质量是太阳的29倍，

and one with a mass of 36 Suns,

另一个是太阳的36倍，

whirling around each other 100 times per second

它们以每秒钟100次的速度 绕着彼此旋转，

before they collide.

然后相互碰撞。

Just imagine the power of that.

想象一下其中的能量。

It's fantastic.

简直不可思议。

And we know it because we heard it.

我们之所以知道这一切， 是因为我们听到了它们。

That's the lasting importance of LIGO.

而这就是LIGO的长远价值所在。

It's an entirely new way to observe the Universe

它为我们提供了一种前所未有的

that we've never had before.

观察宇宙的途径。

It's a way that lets us hear the Universe

通过这一途径， 我们可以倾听宇宙，

and hear the invisible.

倾听不可见的事物。

And there's a lot out there that we can't see --

在实践中甚至是理论上，

宇宙中的许多事物都是不可见的。

in practice or even in principle.

So supernova, for example:

举个例子，超新星——

I would love to know why very massive stars explode in supernovae.

我非常想知道为什么恒星质量 达到一定程度时就会发生超新星爆发。

They're very useful;

这很有价值，

we've learned a lot about the Universe from them.

它们帮助我们 获得了许多有关宇宙的信息。

The problem is, all the interesting physics happens in the core,

问题是，所有有趣的物理现象 都发生在内核，

and the core is hidden behind thousands of kilometers

而内核掩藏在数千公里厚的

of iron and carbon and silicon.

铁、碳、硅元素之下。

We'll never see through it, it's opaque to light.

这些元素不透光， 我们永远无法看穿它们。

Gravitational waves go through iron as if it were glass --

而引力波却能穿过铁；

就像穿过完全透明的玻璃一样。

totally transparent.

The Big Bang: I would love to be able to explore

再举个例子，大爆炸。

我很想研究 宇宙初始的时刻发生的一切，

the first few moments of the Universe,

but we'll never see them,

但是我们已经无法看到了，

because the Big Bang itself is obscured by its own afterglow.

因为大爆炸本身 已经被其发出的余辉所掩盖。

With gravitational waves,

利用引力波，

we should be able to see all the way back to the beginning.

我们有可能看到其最初的状态。

Perhaps most importantly,

或许，最重要的是，

I'm positive that there are things out there

我肯定宇宙中还有很多事物

that we've never seen

是我们见所未见的，

that we may never be able to see

或是永不可见的，

and that we haven't even imagined --

甚至是我们无法想象的——

things that we'll only discover by listening.

我们只能通过倾听 去发现这一切。

And in fact, even in that very first event,

事实上，在运行之初，

LIGO found things that we didn't expect.

LIGO就发现了 我们意想不到的事物。

Here's my colleague and one of the key members of the LIGO collaboration,

下面的录音来自我的同事， 一位LIGO合作研究的主要成员，

麻省理工学院的马特·埃文斯，

Matt Evans, my colleague at MIT, addressing exactly that:

他提到的正是这一点——

(Audio) Matt Evans: The kinds of stars which produce the black holes

马特·埃文斯：我们现在 观察到的这两个黑洞，

that we observed here

它们源自的恒星 可以说是宇宙中的恐龙。

are the dinosaurs of the Universe.

They're these massive things that are old, from prehistoric times,

它们是来自于史前时代 古老而巨大的存在，

and the black holes are kind of like the dinosaur bones

而黑洞则像是恐龙的骨骼化石，

我们通过它们进行考古研究。

with which we do this archeology.

So it lets us really get a whole nother angle

这给了我们一个全新的视角，

on what's out there in the Universe

去思考宇宙中存在的事物，

and how the stars came to be, and in the end, of course,

思考星体的形成过程， 当然，最终要去思考

how we came to be out of this whole mess.

人类在宇宙混沌中的发展之道。

AA: Our challenge now

亚伦：我们当下的挑战

is to be as audacious as possible.

就是要更加大胆尝试。

Thanks to LIGO, we know how to build exquisite detectors

LIGO让我们知道如何去建造 精密的探测器，

that can listen to the Universe,

以此来倾听宇宙，

to the rustle and the chirp of the cosmos.

倾听其中的低簌与鸣响。

Our job is to dream up and build new observatories --

我们的工作是要大胆想象 并建造新的观测台——

a whole new generation of observatories --

在地球上和太空中建立

on the ground, in space.

全新一代的观测台。

I mean, what could be more glorious than listening to the Big Bang itself?

我是说，还有什么事能比 倾听宇宙大爆炸更为美妙呢？

Our job now is to dream big.

我们的工作就是创造伟大的梦想。

Dream with us.

跟我们一起梦想吧！

Thank you.

谢谢。

(Applause)

（掌声）