A little over 100 years ago, in 1915, Einstein published his theory of general relativity, which is sort of a strange name, but it's a theory that explains gravity. It states that mass -- all matter, the planets -- attracts mass, not because of an instantaneous force, as Newton claimed, but because all matter -- all of us, all the planets -- wrinkles the flexible fabric of space-time.
大約一百多年前,在 1915 年, 愛因斯坦發表了他的廣義相對論, 這個理論命名有點奇怪, 但它的說明對象是重力。 這個理論指出質量── 所有物質和星球──會互相吸引, 並非基於牛頓所提出的瞬時力, 而是因為所有物質, 包括我們人類和所有星球, 使富彈性的時空結構出現了皺摺。
Space-time is this thing in which we live and that connects us all. It's like when we lie down on a mattress and distort its contour. The masses move -- again, not according to Newton's laws, but because they see this space-time curvature and follow the little curves, just like when our bedmate nestles up to us because of the mattress curvature.
我們活在時空中, 時空聯繫我們所有人, 情況好比我們躺在牀墊上, 使其形狀發生改變。 我重申,質量移動 並非基於牛頓定律, 而是基於時空曲率, 物質跟隨那些微弱的曲線移動, 就好像牀墊凹了下去, 使枕邊人向我們靠攏一樣。
(Laughter)
(笑聲)
A year later, in 1916, Einstein derived from his theory that gravitational waves existed, and that these waves were produced when masses move, like, for example, when two stars revolve around one another and create folds in space-time which carry energy from the system, and the stars move toward each other. However, he also estimated that these effects were so minute, that it would never be possible to measure them. I'm going to tell you the story of how, with the work of hundreds of scientists working in many countries over the course of many decades, just recently, in 2015, we discovered those gravitational waves for the first time.
一年後,在 1916 年, 愛因斯坦從自己的理論 推論出重力波的存在, 重力波在質量移動時產生, 比如當兩個星體互繞著對方轉動, 在時空造成帶有系統能量的摺皺, 星體便互相靠近。 不過,他預計 其作用太微小, 不大可能加以測量。 但我想告訴你 上百名在眾多國家工作的科學家 是怎樣埋頭苦幹數十載, 終於在最近 2015 年, 首次觀測到重力波。
It's a rather long story. It started 1.3 billion years ago. A long, long time ago, in a galaxy far, far away --
這是個漫長的故事, 一切從 13 億年前開始。 很久很久以前, 在一個遙遠的星系,
(Laughter)
(笑聲)
two black holes were revolving around one another -- "dancing the tango," I like to say. It started slowly, but as they emitted gravitational waves, they grew closer together, accelerating in speed, until, when they were revolving at almost the speed of light, they fused into a single black hole that had 60 times the mass of the Sun, but compressed into the space of 360 kilometers. That's the size of the state of Louisiana, where I live. This incredible effect produced gravitational waves that carried the news of this cosmic hug to the rest of the universe.
兩個黑洞互繞著對方轉動, 我會說它們就好像在「跳探戈」。 剛開始速度很慢, 但隨著它們釋放重力波, 它們加速接近對方, 直至彼此都以光速轉動, 最終融合成一個黑洞, 它的質量是太陽的 60 倍, 但給壓縮成 360 公里的空間, 正是我所定居的 路易斯安那州的面積。 這個奇妙的作用產生了重力波, 把黑洞融合的消息傳開去。
It took us a long time to figure out the effects of these gravitational waves, because the way we measure them is by looking for effects in distances. We want to measure longitudes, distances. When these gravitational waves passed by Earth, which was in 2015, they produced changes in all distances -- the distances between all of you, the distances between you and me, our heights -- every one of us stretched and shrank a tiny bit. The prediction is that the effect is proportional to the distance. But it's very small: even for distances much greater than my slight height, the effect is infinitesimal. For example, the distance between the Earth and the Sun changed by one atomic diameter. How can that be measured? How could we measure it?
我們花了很長時間才發現重力波, 因為我們須找出距離的變化 才能測量重力波。 我們想要量度經度、距離。 當重力波經過地球, 時為 2015 年, 它們改變了所有距離, 包括你們所有人之間的距離, 你和我之間的距離, 還有我們的高度, 我們每個人都伸長又縮小了少許。 科學家預測其變化與距離成正比。 但變化很小, 即使是比我那細微的身高 變化大許多的距離, 其變化也是極微小的。 假如地球和太陽之間的距離 僅改變了一原子直徑, 我們可以測量到這個變化嗎? 我們可以怎樣進行測量呢?
Fifty years ago, some visionary physicists at Caltech and MIT -- Kip Thorne, Ron Drever, Rai Weiss -- thought they could precisely measure distances using lasers that measured distances between mirrors kilometers apart. It took many years, a lot of work and many scientists to develop the technology and develop the ideas. And 20 years later, almost 30 years ago, they started to build two gravitational wave detectors, two interferometers, in the United States. Each one is four kilometers long; one is in Livingston, Louisiana, in the middle of a beautiful forest, and the other is in Hanford, Washington, in the middle of the desert.
50 年前, 加州理工學院和麻省理工學院 一些有遠見的物理學家, 例如:基普·索恩、 朗納·德瑞福、萊納·魏斯, 他們認為可以利用雷射 量度公里以外的鏡子間的距離, 從而精確地測量距離。 為了發展這項科技和意念, 科學家耗費了大量時間、人力和物力。 20 年後, 即大約 30 年前, 他們開始在美國建造兩座干涉儀, 它們是重力波探測儀器。 干涉儀每座長四公里; 一座位於路易斯安那州利文斯頓, 在美麗的森林中央, 另一座位於華盛頓漢福德, 在沙漠之中。
The interferometers have lasers that travel from the center through four kilometers in-vacuum, are reflected in mirrors and then they return. We measure the difference in the distances between this arm and this arm. These detectors are very, very, very sensitive; they're the most precise instruments in the world. Why did we make two? It's because the signals that we want to measure come from space, but the mirrors are moving all the time, so in order to distinguish the gravitational wave effects -- which are astrophysical effects and should show up on the two detectors -- we can distinguish them from the local effects, which appear separately, either on one or the other.
干涉儀備有雷射, 可從中心發送, 雷射通過四公里的真空距離後, 給鏡子反射回原點。 我們會計算兩臂所測量的距離的差。 這些探測儀非常,非常靈敏, 是世上最精密的儀器。 為什麼要有兩座? 那是因為我們想要測量 來自太空的訊號, 而鏡子總是在移動, 為了識別重力波的作用── 重力波是天體物理學的作用, 會在兩座探測儀上顯現出來── 我們可以把重力波從分開出現的 局部作用中區分出來, 那些效果將在其中一座干涉臂可見。
In September of 2015, we were finishing installing the second-generation technology in the detectors, and we still weren't at the optimal sensitivity that we wanted -- we're still not, even now, two years later -- but we wanted to gather data. We didn't think we'd see anything, but we were getting ready to start collecting a few months' worth of data. And then nature surprised us.
在 2015 年九月, 我們正在完成在探測儀上 裝置第二代技術的工作, 我們仍未取得期望的最佳靈敏度── 即使兩年後的今天 仍未達至最佳效果── 但我們希望收集數據。 我們認為將不會有什麼發現, 但已準備要收集數個月份量的數據。 然後,大自然給我們送上驚喜。
On September 14, 2015, we saw, in both detectors, a gravitational wave. In both detectors, we saw a signal with cycles that increased in amplitude and frequency and then go back down. And they were the same in both detectors. They were gravitational waves. And not only that -- in decoding this type of wave, we were able to deduce that they came from black holes fusing together to make one, more than a billion years ago. And that was --
在 2015 年 9 月 14 日, 我們在兩座探測儀 都發現到重力波。 在兩座探測儀, 我們都看見了一個訊號, 振幅和頻率周期性上升然後下跌。 而且兩座儀器 探測到的訊號都是一樣。 它們是重力波。 分析這種波動不但讓我們得出結論: 它們是在超過十億年前, 多個黑洞合而為一時造成的, 而且那是……
(Applause)
(掌聲)
that was fantastic.
那是非常美妙。
At first, we couldn't believe it. We didn't imagine this would happen until much later; it was a surprise for all of us. It took us months to convince ourselves that it was true, because we didn't want to leave any room for error. But it was true, and to clear up any doubt that the detectors really could measure these things, in December of that same year, we measured another gravitational wave, smaller than the first one. The first gravitational wave produced a difference in the distance of four-thousandths of a proton over four kilometers. Yes, the second detection was smaller, but still very convincing by our standards. Despite the fact that these are space-time waves and not sound waves, we like to put them into loudspeakers and listen to them. We call this "the music of the universe." I'd like you to listen to the first two notes of that music.
最初,我們無法相信這是事實, 我們沒想像過會發生 這樣的事情,直至後來; 對我們來說,這是一個驚喜。 我們花了數個月時間說服自己, 因為我們不希望有任何出錯的地方。 然而,那是真的,釋除疑惑後, 探測儀真的能測量那些能量, 同年 12 月, 我們測量到另一重力波, 比首次探測所得的波動小。 首次探測到的重力波 產生的距離相差為 每四公里四千分之一質子。 沒錯,第二次探測所得較為微小, 但按我們的標準來說, 結果仍是可信的。 雖然這些是時空波動,而非聲波, 但我們喜歡用擴音器 來傾聽這些波動, 並稱之為「宇宙的音樂」。 我希望你們也來聽聽這支音樂的首兩個音符。
(Chirping sound)
(鳴聲)
(Chirping sound) The second, shorter sound was the last fraction of a second of the two black holes which, in that fraction of a second, emitted vast amounts of energy -- so much energy, it was like three Suns converting into energy, following that famous formula, E = mc2. Remember that one? We love this music so much we actually dance to it. I'm going to have you listen again.
(鳴聲) 第二個較為短促的聲音是 在一秒的最終的兩個黑洞, 在那一瞬間,它們釋出巨大能量, 能量之高好比 把三個太陽轉換成能量, 遵從那道有名的方程式: E = mc2. 你還記得嗎? 我們很喜歡這音樂,事實上還跳舞。 我將讓你再聽一遍。
(Chirping sound)
(嗚聲)
(Chirping sound) It's the music of the universe!
(嗚聲) 這是宇宙的音樂!
(Applause)
(掌聲)
People frequently ask me now: "What can gravitational waves be used for? And now that you've discovered them, what else is there left to do?" What can gravitational waves be used for?
現在人們經常問我: 「重力波可以用來做什麼?」 「你現在已經發現了重力波, 還剩下什麼要做?」 重力波可以用來做什麼?
When they asked Borges, "What is the purpose of poetry?" he, in turn, answered, "What's the purpose of dawn? What's the purpose of caresses? What's the purpose of the smell of coffee?" He answered, "The purpose of poetry is pleasure; it's for emotion, it's for living."
人們問波赫士:「詩歌有何作用?」 他接著回答: 「黎明有何作用? 愛撫有何作用? 咖啡有何作用?」 他回答: 「詩歌的作用是帶來愉悅; 為情感而存在,為生活而存在。」
And understanding the universe, this human curiosity for knowing how everything works, is similar. Since time immemorial, humanity -- all of us, everyone, as kids -- when we look up at the sky for the first time and see the stars, we wonder, "What are stars?" That curiosity is what makes us human. And that's what we do with science.
而去理解宇宙的慾望, 這種人類對萬物如何運作的好奇心 是很相像的。 自古以來,人類── 當我們所有人 每個人還是孩子時── 首次仰望天空,看見星星, 我們好奇: 「星星是什麼來的?」 那種好奇心是人的特性, 也是我們發展科學的原因。
We like to say that gravitational waves now have a purpose, because we're opening up a new way to explore the universe. Until now, we were able to see the light of the stars via electromagnetic waves. Now we can listen to the sound of the universe, even of things that don't emit light, like gravitational waves.
我們會說重力波現在有用途了, 因為我們開拓了探索宇宙的新方式。 之前我們能夠使用電磁波 來觀測星光, 現在,我們能夠聽到宇宙的聲音, 即使那些東西並不會放光, 比如像重力波。
(Applause)
(掌聲)
Thank you.
謝謝。
(Applause)
(掌聲)
But are they useful? Can't we derive any technology from gravitational waves?
但它們實用嗎? 我們不能用重力波開發任何科技嗎?
Yes, probably. But it will probably take a lot of time. We've developed the technology to detect them, but in terms of the waves themselves, maybe we'll discover 100 years from now that they are useful. But it takes a lot of time to derive technology from science, and that's not why we do it. All technology is derived from science, but we practice science for the enjoyment. What's left to do? A lot. A lot; this is only the beginning.
能夠的, 但需要很長時間。 我們已經發展了技術去探測重力波, 但就重力波而言, 可能我們將在 一百年後才發現其用處。 從科學到科技需要大量時間, 但並非我們實行的原因。 所有科技都從科學而來, 但我們從事科學是為了享受。 還剩下什麼要做? 很多。 很多;這只是個開始。
As we make the detectors more and more sensitive -- and we have lots of work to do there -- not only are we going to see more black holes and be able to catalog how many there are, where they are and how big they are, we'll also be able to see other objects. We'll see neutron stars fuse and turn into black holes. We'll see a black holes being born. We'll be able to see rotating stars in our galaxy produce sinusoidal waves. We'll be able to see explosions of supernovas in our galaxy. We'll be seeing a whole spectrum of new sources.
隨著我們使探測儀更趨靈敏── 那已經是很大的工作量, 我們不單會看見更多黑洞, 能夠紀錄黑洞的數量、位置和大小, 我們還能夠看見其他物體。 我們將可以看見中子星 融合並轉化為黑洞。 我們將可以看見黑洞誕生。 我們將可以看見銀河的星星旋轉, 產生正弦波。 我們將可以看見超新星 在我們的銀河爆炸。 我們將會看見新事物的完整波譜。
We like to say that we've added a new sense to the human body: now, in addition to seeing, we're able to hear. This is a revolution in astronomy, like when Galileo invented the telescope. It's like when they added sound to silent movies. This is just the beginning. We like to think that the road to science is very long -- very fun, but very long -- and that we, this large, international community of scientists, working from many countries, together as a team, are helping to build that road; that we're shedding light -- sometimes encountering detours -- and building, perhaps, a highway to the universe.
我們想說 我們為人類增加了新感官: 現在,除了看得見, 我們能聽得見。 這在天文學是一項革新, 像伽利略發明了望遠鏡一樣。 情形好比人們為默片增加了聲音。 這只是個開始。 我們認為 科學的路很漫長── 很有趣,但很漫長, 而我們這些科學家 是一個龐大的國際性團體, 來自眾多國家,組成一個團隊, 正協助建設這條路; 我們照亮道路—儘管有時會遇上此路不通 — 並且建設一條可能是 直達宇宙的高速公路。
Thank you.
多謝各位。
(Applause)
(掌聲)