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引力波的发现意味着什么 – 译学馆
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引力波的发现意味着什么

What the discovery of gravitational waves means | Allan Adams

13亿年前
1.3 billion years ago,
在一个无比遥远的星系
in a distant, distant galaxy,
两个黑洞陷入了一个漩涡之中
two black holes locked into a spiral,
以不可阻挡之势冲向彼此
falling inexorably towards each other
然后相撞
and collided,
由此将等同于三个太阳的物质
converting three Suns’ worth of stuff
在十分之一秒内转化成了纯能量
into pure energy in a tenth of a second.
在那短暂的一瞬间
For that brief moment in time,
碰撞产生的光芒
the glow was brighter than all the stars
令已知宇宙中所有星系中的
in all the galaxies
所有恒星都黯然失色
in all of the known Universe.
那是一个名副其实的
It was a very

big bang.
然而它们并没有 以光的形式释放能量
But they didn’t releasetheir energy in light.
因为它们是黑洞
I mean, you know, they’re black holes.
所有产生的能量 都被注入时间和空间本身
All that energy was pumpedinto the fabric of space and time itself,
使宇宙以引力波的形式延展
making the Universe explodein gravitational waves.
让我来对所涉及的 时间标度做一下说明
Let me give you a senseof the timescale at work here.
13亿年前
1.3 billion years ago,
地球上刚出现了多细胞生物
Earth had just managed to evolvemulticellular life.
在那之后 地球上的生物不断进化
Since then, Earth has made and evolved
珊瑚 鱼类 植物 恐龙 人类相继出现 当然 还有互联网
corals, fish, plants, dinosaurs, peopleand even — God save us — the Internet.
大约25年前
And about 25 years ago,
一群极具冒险精神的人
a particularly audacious set of people —
麻省理工学院的瑞伊·维斯
Rai Weiss at MIT, Kip Thorneand Ronald Drever at Caltech —
以及加州理工学院的 奇普·索恩和罗纳德·德雷弗
decided that it would be really neat
产生了一个他们认为 非常了不起的想法:
to build a giant laser detector
一群极具冒险精神的人,
with which to searchfor the gravitational waves
来搜寻由黑洞撞击等产生的引力波
from things like colliding black holes.
大多数人都觉得他们疯了
Now, most people thought they were nuts.
但也有很多人认为 他们是了不起的疯子
But enough people realizedthat they were brilliant nuts
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
that the US National Science Foundationdecided to fund their crazy idea.
由此 经历了这几十年的发展
So after decades of development,
通过不断的建设和构想
construction and imagination
以及惊人数量的辛勤工作
and a breathtaking amount of hard work,
他们最终建成了这台 名为LIGO的探测器:
they built their detector, called LIGO:
全称叫做“激光干涉引力波观测台”
The Laser InterferometerGravitational-Wave Observatory.
在过去的几年中
For the last several years,
LIGO的准确性得到了巨大的提升
LIGO’s been undergoinga huge expansion in its accuracy,
其探测能力也有了惊人的进步
a tremendous improvementin its detection ability.
所以现在它可以被称为“高端LIGO”
It’s now called Advanced LIGO as a result.
2015年9月初
In early September of 2015,
LIGO进行了最后一次试运行
LIGO turned on for a final test run
辨识出了少量滞留的细节
while they sorted outa few lingering details.
随后 在2015年9月14日
And on September 14 of 2015,
即探测器正式运行数天后
just days after the detectorhad gone live,
由黑洞撞击所产生的引力波
the gravitational wavesfrom those colliding black holes
经过了地球
passed through the Earth.
它经过了我们每一个人
And they passed through you and me.
它也经过了那台探测器
And they passed through the detector.
[音频]斯科特·休斯:在我生命中只有两个时刻
(Audio) Scott Hughes:There’s two moments in my life
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.
另一个是我父亲病逝前 我与他告别的时候
The other is when I had to say goodbyeto my father when he was terminally ill.
可以说我从事这项事业就是为了这一刻
You know, it was the payoffof my career, basically.
我为其付出努力的事情 都不再是科幻小说了![大笑]
Everything I’d been working on –it’s no longer science fiction! (Laughs)
艾伦·亚当斯:这是我的好友兼合作伙伴
Allan Adams: So that’s my very good friendand collaborator, Scott Hughes,
斯科特·休斯 麻省理工学院理论物理学家
a theoretical physicist at MIT,
他研究产生于黑洞的引力波
who has been studyinggravitational waves from black holes
以及其传递给像LIGO这样的观测台的信号
and the signals that they could imparton observatories like LIGO,
已经有23年之久
for the past 23 years.
现在让我来简单介绍一下 什么是引力波
So let me take a moment to tell youwhat I mean by a gravitational wave.
引力波是以时间和
A gravitational wave is a ripple
空间的形式产生的波动
in the shape of space and time.
当引力波通过时
As the wave passes by,
它将空间及其中的所有事物
it stretches space and everything in it
向同一方向拉伸
in one direction,
同时将其在另一方向上压缩
and compresses it in the other.
这使得许多广义相对论教授
This has led to countless instructorsof general relativity
在课堂上说明广义相对论时 都跳起了滑稽的舞蹈
doing a really silly dance to demonstratein their classes on general relativity.
“拉伸再扩展 拉伸再扩展”
“It stretches and expands,it stretches and expands.”
研究引力波的难点在于
So the trouble with gravitational waves
它们太微弱了;微弱得不合常理
is that they’re very weak;they’re preposterously weak.
就拿9月14日穿过我们的引力波为例
For example, the waves that hit uson September 14 —
确实 在其作用下 我们每一个人都被
and yes, every single one of youstretched and compressed
拉伸和压缩了
under the action of that wave —
但这个过程中一个普通人被拉伸了
when the waves hit, they stretchedthe average person
10的21次方分之一
by one part in 10 to the 21.
也就是小数点后20个零
That’s a decimal place, 20 zeroes,
再加1个一
and a one.
这就是为什么 人们认为LIGO的研究者们都是疯子
That’s why everyone thoughtthe LIGO people were nuts.
即使使用5千米长的激光探测器 ——这本身就很疯狂
Even with a laser detector five kilometerslong — and that’s already crazy —
他们还是需要以比原子核半径的
they would have to measurethe length of those detectors
千分之一还小的单位来测量那些
to less than one thousandthof the radius of the nucleus
探测器的长度
of an atom.
这真是超乎常人所能想象
And that’s preposterous.
在其关于万有引力的 经典著作的末尾
So towards the endof his classic text on gravity,
LIGO的联合发明人奇普·索恩
LIGO co-founder Kip Thorne
对引力波的探索进行了如下描述
described the huntfor gravitational waves as follows:
他说:“要建成这样的探测器
He said, “The technical difficultiesto be surmounted
需要克服巨大的
in constructing such detectors
技术难题
are enormous.
但是 物理学家都是天才
But physicists are ingenious,
再加上公众的广泛支持
and with the supportof a broad lay public,
所有的难关都会被攻克”
all obstacles will surely be overcome.”
这本著作出版于1973年
Thorne published that in 1973,
42年后 他才获得了成功
42 years before he succeeded.
让我们回到LIGO的话题上来
Now, coming back to LIGO,
斯科特总是说
Scott likes to say that LIGOacts like an ear
LIGO的运作方式 更像是耳朵而非眼睛
more than it does like an eye.
让我来解释一下这句话的意思
I want to explain what that means.
可见光的波长
Visible light has a wavelength, a size,
比我们身边的事物都要短
that’s much smallerthan the things around you,
比如人的五官
the features on people’s faces,
或是你们的手机
the size of your cell phone.
这样的波长非常有用处
And that’s really useful,
因为它令人们借助来自
because it lets you make an imageor a map of the things around you,
身边场景的不同位置的光线
by looking at the lightcoming from different spots
获得周围事物的直观影像
in the scene about you.
声音就不同了
Sound is different.
人们能听到的声音的波长 可以达到50英尺
Audible sound has a wavelengththat can be up to 50 feet long.
这使得声音很难
And that makes it really difficult —
事实上 从实用意义来讲 根本不可能
in fact, in practical purposes,impossible — to make an image
去形成你所在意的事物的直观影像
of something you really care about.
比如你的孩子长什么样子
Your child’s face.
相反 我们通过声音
Instead, we use soundto listen for features like pitch
来辨识音高 声调 节奏 音量等特征
and tone and rhythm and volume
以此来推断声音背后的故事
to infer a story behind the sounds.
爱丽丝正在讲话
That’s Alice talking.
鲍勃插话进来了
That’s Bob interrupting.
鲍勃真是不分场合
Silly Bob.
引力波也有同样的作用
So, the same is trueof gravitational waves.
我们虽然不能通过引力波 获得宇宙中事物的直观影像
We can’t use them to make simple imagesof things out in the Universe.
但通过倾听
But by listening to changes
引力波振幅和频率的变化
in the amplitude and frequencyof those waves,
我们能够听出它们所传达的故事
we can hear the storythat those waves are telling.
至少LIGO接收到的
And at least for LIGO,
波频在人们能听到的范围内
the frequencies that it can hearare in the audio band.
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 patternsinto pressure waves and air, into sound,
我们就能确实地听到 宇宙传达给我们的信息
we can literally hearthe Universe speaking to us.
比如 以这种形式倾听引力波
For example, listening to gravity,just in this way,
我们就能获得很多 有关两个黑洞撞击的信息
can tell us a lot about the collisionof two black holes,
这也是我的同事斯科特 花了大量时间探索的事情
something my colleague Scott has spentan awful lot of time thinking about.
[音频]斯科特:如果两个黑洞没有旋转
(Audio) SH: If the two black holesare non-spinning,
你听到的是“嗡——”一声鸣响
you get a very simple chirp: whoop!
如果这两个黑洞高速旋转 响声是相同的
If the two bodies are spinningvery rapidly, I have that same chirp,
但调制却发生了变化
but with a modulation on top of it,
听起来就像这样:嗡——嗡——嗡
so it kind of goes: whir, whir, whir!
可以说这就是旋转 在波形图上留下的只言片语
It’s sort of the vocabulary of spinimprinted on this waveform.
艾伦:在2015年9月14日
AA: So on September 14, 2015,
一个我将永远铭记的日子
a date that’s definitelygoing to live in my memory,
LIGO听到了这样的声音:
LIGO heard this:
[嗡鸣声]
[Whirring sound]
懂得如何倾听它的人知道 这个声音来自
So if you know how to listen,that is the sound of —
斯科特:……两个质量均为太阳30倍左右的黑洞
(Audio) SH: … two black holes,each of about 30 solar masses,
以相当于搅拌机运转的速度
that were whirling around at a rate
旋转时所发出的声音
comparable to what goes onin your blender.
艾伦:我们有必要停下来好好想想 这意味着什么
AA: It’s worth pausing hereto think about what that means.
两个黑洞 宇宙中密度最高的物体
Two black holes, the densest thingin the Universe,
其中一个的质量是太阳的29倍
one with a mass of 29 Suns
另一个是太阳的36倍
and one with a mass of 36 Suns,
它们以每秒钟100次的速度 绕着彼此旋转
whirling around each other100 times
然后相互碰撞
per second before they collide.
想象一下其中的能量
Just imagine the power of that.
简直不可思议
It’s fantastic.
我们之所以知道这一切 是因为我们听到了它们
And we know it because we heard it.
而这就是LIGO的长远价值所在
That’s the lasting importance of LIGO.
它为我们提供了一种前所未有的
It’s an entirely new wayto observe the Universe
观察宇宙的途径
that we’ve never had before.
通过这一途径 我们可以倾听宇宙
It’s a way that lets us hear the Universe
倾听不可见的事物
and hear the invisible.
在实践中甚至是理论上
And there’s a lot out therethat we can’t see —
宇宙中的许多事物都是不可见的
in practice or even in principle.
举个例子 超新星
So supernova, for example:
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
I would love to know why very massivestars explode in supernovae.
这很有价值
They’re very useful;
它们帮助我们 获得了许多有关宇宙的信息
we’ve learned a lotabout the Universe from them.
问题是 所有有趣的物理现象 都发生在内核
The problem is, all the interestingphysics happens in the core,
而内核掩藏在数千公里厚的
and the core is hidden behindthousands of kilometers
铁 碳 硅元素之下
of iron and carbon and silicon.
这些元素不透光 我们永远无法看穿它们
We’ll never see through it,it’s opaque to light. Gravitational waves
而引力波却能穿过铁;
go through iron as if it were glass —
就像穿过完全透明的玻璃一样
totally transparent.
再举个例子 大爆炸
The Big Bang: I would loveto be able to explore
我很想研究 宇宙初始的时刻发生的一切
the first few moments of the Universe,
但是我们已经无法看到了
but we’ll never see them,
因为大爆炸本身 已经被其发出的余辉所掩盖
because the Big Bang itselfis obscured by its own afterglow.
利用引力波
With gravitational waves,
我们有可能看到其最初的状态
we should be able to seeall the way back to the beginning.
或许 最重要的是
Perhaps most importantly,
我肯定宇宙中还有很多事物
I’m positive that thereare things out there
是我们见所未见的
that we’ve never seen
或是永不可见的
that we may never be able to see
甚至是我们无法想象的
and that we haven’t even imagined —
我们只能通过倾听 去发现这一切
things that we’ll onlydiscover by listening.
事实上 在运行之初
And in fact, evenin that very first event,
LIGO就发现了 我们意想不到的事物
LIGO found things that we didn’t expect.
下面的录音来自我的同事 一位LIGO合作研究的主要成员
Here’s my colleague and one of the keymembers of the LIGO collaboration,
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 starswhich 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.
它们是来自于史前时代 古老而巨大的存在
They’re these massive thingsthat are old, from prehistoric times,
而黑洞则像是恐龙的骨骼化石
and the black holes are kind of likethe dinosaur bones
我们通过它们进行考古研究
with which we do this archeology.
这给了我们一个全新的视角
So it lets us really geta whole nother angle
去思考宇宙中存在的事物
on what’s out there in the Universe
思考星体的形成过程 当然 最终要去思考
and how the stars came to be,and in the end, of course,
人类在宇宙混沌中的发展之道
how we came to be out of this whole mess.
亚伦:我们当下的挑战
AA: Our challenge now
就是要更加大胆尝试
is to be as audacious as possible.
LIGO让我们知道如何去建造 精密的探测器
Thanks to LIGO, we know howto build exquisite detectors
人类在宇宙混沌中的发展之道。
that can listen to the Universe,
倾听其中的低簌与鸣响
to the rustle and the chirp of the cosmos.
我们的工作是要大胆想象 并建造新的观测台
Our job is to dream up and buildnew observatories —
在地球上和太空中建立
a whole new generation of observatories —
全新一代的观测台
on the ground, in space.
我是说 还有什么事能比 倾听宇宙大爆炸更为美妙呢?
I mean, what could be more gloriousthan listening to the Big Bang itself?
我们的工作就是创造伟大的梦想
Our job now is to dream big.
跟我们一起梦想吧!
Dream with us.
谢谢
Thank you.
[掌声]
(Applause)

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引力波的发现对我们接下来的生活会有什么影响呢?让我们听听Allan Adams对此的理解。

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