What the discovery of gravitational waves means | Allan Adams

譯者: Wei Chang 審譯者: 瑞文Eleven 林Lim

1.3 billion years ago,

十三億年前，

in a distant, distant galaxy,

在一個極為遙遠的星系中，

two black holes locked into a spiral,

有兩個黑洞陷入漩渦，

falling inexorably towards each other

無法抗拒地往對方靠近，

and collided,

最終相撞。

converting three Suns' worth of stuff

在僅僅十分之一秒之內，

into pure energy in a tenth of a second.

將接近三個太陽的物質 轉換成了純粹的能量。

For that brief moment in time,

在那短暫的時間裡，

the glow was brighter than all the stars

發出的光芒比我們所知的宇宙中

in all the galaxies

所有星系中的任何星球

in all of the known Universe.

都要明亮。

It was a very

那是一場大

big

爆

bang.

炸。

But they didn't release their energy in light.

但它們並未將能量以光的形式釋放。

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

我是說，你知道的， 它們是黑洞嘛。

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

所有能量被壓縮進時空之中，

making the Universe explode in gravitational waves.

並以重力波的形式爆炸， 擴及整個宇宙。

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

讓我帶你們了解這個過程的時間軸。

1.3 billion years ago,

十三億年前，

Earth had just managed to evolve multicellular life.

地球上才剛要形成多細胞生命。

Since then, Earth has made and evolved

從那時起，地球上已誕生並孕育

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

珊瑚、魚類、植物、恐龍、人類， 以及....感謝老天...網路。

And about 25 years ago,

大約 25 年前，

a particularly audacious set of people --

一群膽子特別大的人：

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

麻省理工學院的Rai Weiss 、 加州理工學院的 Kip Thorne 和 Ronald Drever

decided that it would be really neat

認為建造一台巨大的 雷射探測儀，

to build a giant laser detector

並用來搜尋來自黑洞碰撞合併 之類事件的重力波，

with which to search for the gravitational waves

會是件非常美妙的事情。

from things like colliding black holes.

Now, most people thought they were nuts.

大多數人覺得他們瘋了。

But enough people realized that they were brilliant nuts

但已有足夠的人了解 他們是很傑出的瘋子，

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

因此美國國家科學基金會 決定資助這個瘋狂的點子。

So after decades of development,

所以經過了幾十年的發展、

construction and imagination

建造、想像，

and a breathtaking amount of hard work,

和數量驚人的艱苦工作後，

they built their detector, called LIGO:

他們打造出自己的探測儀， 取名為「LIGO」：

The Laser Interferometer Gravitational-Wave Observatory.

雷射干涉儀重力波觀測天文台。

For the last several years,

在過去幾年間，

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

LIGO 的精準度經過大幅改善，

a tremendous improvement in its detection ability.

在其偵測能力上有了卓越的進步。

It's now called Advanced LIGO as a result.

因此，它現在被稱為「進階版 LIGO」。

In early September of 2015,

在 2015 年 9 月上旬，

LIGO turned on for a final test run

LIGO 啟動進入最終測試階段，

while they sorted out a few lingering details.

人們找出了一些仍待解決的細節。

And on September 14 of 2015,

然後在 2015 年 9 月 14 號，

just days after the detector had gone live,

就在探測儀啟動幾天後，

the gravitational waves from those colliding black holes

來自那些碰撞的黑洞的重力波

passed through the Earth.

經過了地球。

And they passed through you and me.

它們穿過你和我。

And they passed through the detector.

它們穿過了探測儀。

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

（語音） Scott Hughes： 在我生命中，只有兩個時刻

比那時更讓我情緒激動。

more emotionally intense than that.

一是我女兒出生。

One is the birth of my daughter.

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

另一個則是必須和我 重症末期的父親道別。

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

你懂的，這基本上 是我職涯顛峰時刻，

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

我所努力耕耘的一切－－ 終於不再是科幻小說了！（笑聲）

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

Allan Adams：這是我的 好友兼夥伴，Scott Hughes，

a theoretical physicist at MIT,

麻省理工學院的理論物理學家，

who has been studying gravitational waves from black holes

他研究來自黑洞的重力波，

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

以及他們從 LIGO 等 觀測器材上得知的信號，

for the past 23 years.

長達 23 年。

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

讓我花一些時間解釋 何謂「重力波」。

A gravitational wave is a ripple

重力波是一種處於 時間與空間中的波。

in the shape of space and time.

As the wave passes by,

當重力波經過，

it stretches space and everything in it

它會從一個方向伸展空間， 和空間中的所有事物。

in one direction,

and compresses it in the other.

並在另一側壓縮空間。

This has led to countless instructors of general relativity

這使得無數講述重力波的講師

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

在課堂上瘋狂亂舞， 只為模擬重力波。

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

「它伸展然後膨脹、 它伸展然後膨脹。」

So the trouble with gravitational waves

關於重力波的問題是，

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

它們非常的微弱； 它們極不合理的微弱。

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

以 9 月 14 號襲擊我們的 重力波為例。

and yes, every single one of you stretched and compressed

還有當然，你們每個人 都在那個波的影響下

under the action of that wave --

伸展並壓縮。

when the waves hit, they stretched the average person

當那陣波襲來， 它們平均將每個人

by one part in 10 to the 21.

伸長了 10 的 21 次方分之一倍。

That's a decimal place, 20 zeroes,

也就是小數點後接上 20 個零後

and a one.

再接上1。

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

這就是為什麼大家都覺得 開發 LIGO 的人是瘋子。

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

即使雷射探測儀有五公里長 ，這已經很瘋狂了。

they would have to measure the length of those detectors

他們還得用比原子核半徑的千分之一

to less than one thousandth of the radius of the nucleus

更小的單位來測量 這些探測儀的長度。

of an atom.

And that's preposterous.

這太荒謬了！

So towards the end of his classic text on gravity,

因此，在 LIGO 協同開發者 Kip Thorne

LIGO co-founder Kip Thorne

撰寫的重力波經典論文結尾，

described the hunt for gravitational waves as follows:

他如此形容捕獲重力波的行動，

He said, "The technical difficulties to be surmounted

他說：「要建造出這樣的探測儀，

in constructing such detectors

必須克服的困難，

are enormous.

無以計數。

But physicists are ingenious,

但物理學家具有高度創造力，

and with the support of a broad lay public,

以及有了來自廣大民眾的支持，

all obstacles will surely be overcome."

一切障礙都能被克服。」

Thorne published that in 1973,

Thorne 在 1973 年發表此文章，

42 years before he succeeded.

距離他成功還有 42 年。

Now, coming back to LIGO,

現在，回到 LIGO 上，

Scott likes to say that LIGO acts like an ear

Scott 喜歡說 LIGO 的角色 比較像耳朵，

more than it does like an eye.

而非眼睛。

I want to explain what that means.

我解釋一下這是什麼意思。

Visible light has a wavelength, a size,

可見光的波長、尺寸

that's much smaller than the things around you,

遠遠小於你身邊的東西，

the features on people's faces,

小於人們臉上的器官、

the size of your cell phone.

你的手機大小。

And that's really useful,

這對我們來說很方便，

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

因為藉由觀察來自 你所處環境中不同位置的光線，

by looking at the light coming from different spots

你可以建立週圍物品的景象或地圖。

in the scene about you.

Sound is different.

聲音就不同了。

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

可聽見的聲音波長 最長可達 50 呎(15.24m)。

And that makes it really difficult --

這使得要為你所關注的物品 建立影像變得很困難。

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

of something you really care about.

事實上，實務運用是不可能的。

Your child's face.

例如你孩子的臉。

Instead, we use sound to listen for features like pitch

取而代之的是， 我們運用聲音來聆聽

and tone and rhythm and volume

音高、聲調、節奏和音量等特性，

to infer a story behind the sounds.

以推論這些聲音背後的故事。

That's Alice talking.

那是 Alice 在說話。

That's Bob interrupting.

那是 Bob 在插嘴。

Silly Bob.

笨蛋 Bob。

So, the same is true of gravitational waves.

重力波也是一樣的。

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

我們無法運用它們來建立 宇宙中事物的簡單影像，

But by listening to changes

但藉由聆聽這些波中

in the amplitude and frequency of those waves,

幅度和頻率的變化，

we can hear the story that those waves are telling.

我們可以聽出 這些波訴說的故事。

And at least for LIGO,

至少對 LIGO 來說，

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

它能聽見的頻率位於音頻帶內。

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

因此如果我們將波的圖形轉換成 壓力波和氣壓、

轉換成聲音， 我們就能聽見宇宙正在對我們說話。

we can literally hear the Universe speaking to us.

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

例如，用這種方法「聆聽」重力波，

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

它可以告訴我們 關於兩個黑洞相互碰撞的事，

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

這是我同事 Scott 花了 非常多時間在思考的事情。

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

（錄音）SH： 如果兩個黑洞並未旋轉，

你會得到一聲簡單的音調：呼！

you get a very simple chirp: whoop!

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

如果兩個物體非常快速的旋轉， 我得到一樣的聲音，

but with a modulation on top of it,

但會有所不同，

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

所以聽起來會像是：呼咿呼咿呼咿！

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

這有點像是這類旋轉 在波形圖上留下的字彙。

AA: So on September 14, 2015,

AA： 在 2015 年 9 月 14 日，

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

這個日期肯定會 深深烙印在我回憶中，

LIGO heard this:

LIGO 聽到這個聲音：

[Whirring sound]

（呼咿聲）

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

如果你知道怎麼聆聽， 這個聲音是

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

（錄音）SH：……兩個黑洞， 兩者皆約 30倍太陽質量大小，

that were whirling around at a rate

以與你家攪拌機差不多的速度

comparable to what goes on in your blender.

旋轉著。

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

AA：這值得我們暫停一下， 思考這意味著什麼。

Two black holes, the densest thing in the Universe,

兩個黑洞，宇宙中密度最高的事物，

one with a mass of 29 Suns

一個是29倍的太陽質量、

and one with a mass of 36 Suns,

另一個則是36倍太陽質量，

whirling around each other 100 times per second

在它們碰撞前，

以每秒 100 圈的速度 繞著彼此旋轉。

before they collide.

Just imagine the power of that.

想想看這其中的能量。

It's fantastic.

太奇妙了。

And we know it because we heard it.

我們會知道這件事， 則是因為我們聽見了。

That's the lasting importance of LIGO.

這是 LIGO 長存的重要性。

It's an entirely new way to observe the Universe

這是觀測宇宙的全新方法，

that we've never had before.

前所未見。

It's a way that lets us hear the Universe

這方法讓我們能聆聽宇宙，

and hear the invisible.

及那些無形的東西。

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

外頭有許多我們看不見的東西。

in practice or even in principle.

無論是實務，甚至原理。

So supernova, for example:

以超新星為例：

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

我想要知道為什麼巨大的星球 會爆炸形成超新星。

They're very useful;

超新星很有用，

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

我們觀察它們， 學到許多有關宇宙的事。

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

問題是，所有有趣的物理現象 都發生在核心中，

and the core is hidden behind thousands of kilometers

而核心藏身在數千公尺厚

of iron and carbon and silicon.

的鐵、碳和矽之內。

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

我們永遠無法看見裡面， 因為它是不透光的。

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

重力波則穿透了鐵， 彷彿它是玻璃般

totally transparent.

完全透明。

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

大霹靂。我希望能夠探索

the first few moments of the Universe,

宇宙形成的起初幾秒，

but we'll never see them,

但我們永遠無法看見，

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

因為大霹靂被己身的餘暉所遮蔽了。

With gravitational waves,

藉由重力波，

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

我們應該能一路追溯回源頭。

Perhaps most importantly,

也許最重要的是，

I'm positive that there are things out there

我確定在地球外頭

that we've never seen

有我們從未見過、

that we may never be able to see

我們也許永遠無法見到，

and that we haven't even imagined --

以及我們從未能想像的事物。

things that we'll only discover by listening.

那些事物，我們只能靠聆聽去發現。

And in fact, even in that very first event,

事實上，即使在非常早期，

LIGO found things that we didn't expect.

LIGO 曾發現 出乎我們意料之外的東西。

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

這是我同事，和 LIGO 合作團隊中的一位關鍵人物：

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

Matt Evans，我在 麻省理工學院的同事，他說：

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

（錄音）Matt Evans： 我們觀察到的

that we observed here

那種能產生黑洞的星球，

are the dinosaurs of the Universe.

是宇宙中的恐龍。

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

它們是那些古老、來自 史前時代的巨大東西，

and the black holes are kind of like the dinosaur bones

而黑洞就像是恐龍化石，

with which we do this archeology.

我們所做的則是考古學。

So it lets us really get a whole nother angle

這讓我們得到另一個全新視角

on what's out there in the Universe

來了解宇宙中存在什麼東西，

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

以及星球如何轉變，還有當然，

how we came to be out of this whole mess.

我們自己在這團混沌中的出路。

AA: Our challenge now

AA： 我們目前的挑戰是

is to be as audacious as possible.

要盡可能地大膽、創新。

Thanks to LIGO, we know how to build exquisite detectors

感謝 LIGO，我們懂得如何 建造精細的探測儀

that can listen to the Universe,

以聆聽宇宙，

to the rustle and the chirp of the cosmos.

聆聽時空中的沙沙聲和啾啾聲。

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

我們工作是要擁有夢想， 並在地表上、在太空中

a whole new generation of observatories --

打造新的天文臺，

on the ground, in space.

一整個新世代的天文臺。

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

我是指，還有什麼事會比聆聽 大霹靂本身更偉大呢？

Our job now is to dream big.

我們當下的任務就是要盡情作夢。

Dream with us.

跟我們一起作夢吧。

Thank you.

謝謝各位。

(Applause)

（掌聲）