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.
在 1915 年,也就是 100 多年前, 爱因斯坦发表了他的相对论理论, 这个理论的名字虽然听起来很奇怪, 但是它解释了万有引力。 该理论指出,所有物质(包括星球) 都会互相吸引, 这并不是由于牛顿所提出的瞬时力, 而是因为所有的事物—— 包括我们人类以及所有的星球—— 使富有弹性的时空结构出现了褶皱。
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.
我们活在时空中, 时空联系了我们所有的人, 这种感觉就像我们躺在床垫上, 使其发生了形变。 再次重申,万物运动 不是依照牛顿的法则, 而是因为它们之间有时空曲率, 它们按照这些平滑的曲线运动。 就好像床垫轻微陷了下去, 使枕边人向我们靠近了一样。
(Laughter)
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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.
一年以后的 1916 年, 爱因斯坦从他的理论中得出: 引力波是存在的, 当万物移动的时候就会产生引力波。 比如,当两颗恒星围着彼此旋转 并在时空中产生褶皱, 这些褶皱携带着来自系统的能量, 这两颗恒星就会互相靠近。 不过,他也预计 这种作用力太微小, 不大可能对其进行测量。 但我想告诉各位的是, 经过多个国家上百名科学家 数十载的埋头钻研, 终于,在 2015 年, 我们首次观测到了引力波。
It's a rather long story. It started 1.3 billion years ago. A long, long time ago, in a galaxy far, far away --
这是个漫长的故事, 一切从 13 亿年前开始。 很久很久以前, 在一个非常非常遥远的星系——
(Laughter)
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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.
两个黑洞相互围绕着对方转动, 用我自己的话说,就像在“跳探戈舞”一样。 刚开始速度很慢, 但随着它们不断释放引力波, 开始加速接近对方, 直至彼此都以光速转动, 最终融合成一个黑洞, 它的质量是太阳的 60 倍, 但却被压缩进了 只有 360 公里大小的空间, 相当于我所居住的 路易斯安那州的面积。 这个奇妙的作用产生的引力波 把黑洞融合的消息 传递到了宇宙的其他角落。
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?
我们花了很长时间才发现了引力波, 因为我们必须找出距离的变化 才能测量引力波。 我们想要测量经度和距离。 当引力波在 2015 年 经过地球, 它们改变了所有的距离—— 包括你们所有人, 以及你们和我之间的距离, 还有我们的高度—— 我们每个人的尺寸 都缩放了一点点。 科学家预测其变化与距离成正比。 但这种变化很小: 即使是比我那微不足道的身高 变化大许多的距离, 其变化也是极微小的。 假如地球和太阳之间的距离 仅发生了一个原子直径那么小的改变, 我们能够测量到这个变化吗? 应该怎样进行测量呢?
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, 加州理工学院和麻省理工学院的 一些有远见的物理学家—— 基普·索恩(Kip Thorne)、罗纳德·德瑞福 (Ron Drever)和莱纳·魏斯(Rai Weiss)—— 认为可以利用激光来测量 相距几公里远的镜子间的距离, 从而精确地测量出引力波, 这个项目花费了许多年, 无数的科学家做了大量的工作, 不断研发技术和细化想法。 然后二十年过去了, 大约在三十年前, 他们开始在美国建立两个 巨大的引力波探测器 和两个干涉仪。 每一台仪器都有 4000 米长, 一台位于路易斯安那州利文斯顿 一片美丽的森林中, 另一台位于华盛顿州汉福德的 一片沙漠之中。
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.
干涉仪有激光发射器, 激光从仪器中心发射出去, 穿过 4000 米的真空, 再被镜子反射回来。 我们测量两臂之间 距离的差值。 这些探测器都非常非常灵敏, 是世界上最精确的仪器。 那么我们为什么要制造两台呢? 这是因为我们要测量的信号来自太空, 但是镜子却总是在移动, 所以为了区分引力波效应—— 这是天体物理效应, 应该会出现在两个探测器上—— 我们可以把引力波 和局部效应区分开来, 并体现在其中一个探测仪上。
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.
2015 年 9 月, 我们在探测仪上 完成了第二代技术的安装, 但是我们仍未取得最佳的灵敏度—— ——即使是两年后的今天也没有—— 但是我们迫不及待地想要收集数据。 我们不认为自己能够有什么发现, 但是我们已经准备好 收集相当于几个月的数据。 然后,大自然震惊了我们。
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 年的 9 月 14 日, 我们在两个探测器中 都发现了一条引力波。 在两个探测器中, 我们都检测到了一条信号, 振幅和频率 呈周期性增减。 两台探测器探测到的信号都是一样的。 它们就是引力波! 而且不仅如此——在分析这种波形的同时, 我们能够判断,它们来自于 十亿年前几个黑洞 融合产生的黑洞。 那真的是——
(Applause)
(掌声)
that was fantastic.
那真是非常奇妙。
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,我们都无法相信这个事实。 过了很久我们才回过神来。 对我们来说,这是一个惊喜。 我们花费了数月的时间说服自己, 我们真的探测到了引力波, 因为我们不想有任何地方出错。 这的确是真的,而且为了确保 探测器真的能够测量这些信号, 在同年的十二月, 我们又测量到了另一个引力波, 比首次探测到的要小。 首次探测的引力波 在 4000 米的距离内产生了 相当于千分之四个 质子大小的差距。 是的,虽然第二次 探测信号比第一次要微弱, 但是以我们的标准, 这一结果仍然十分具有说服力。 尽管这实际上是 时空波而不是声波, 我们依旧喜欢把它们 转换成声音信号,去聆听它们。 我们管它叫作“宇宙的旋律”。 我想让大家听一听 这段旋律的前两个音符。
(Chirping sound)
(鸣声)
(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.
(鸣声) 第二个较为短促的声音是 在两个黑洞融合的 最后一秒内产生的, 在那一瞬间, 它们释放出了巨大的能量—— 其规模相当于三个太阳 全部转化成的能量, 遵循那道著名的方程: E = mc^2。 还记得这个吗? 我们太喜欢这段旋律了, 还伴着它跳了段舞。 我们再听一遍。
(Chirping sound)
(鸣声)
(Chirping sound) It's the music of the universe!
(鸣声) 这就是宇宙的旋律!
(Applause)
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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?
人们现在经常问我: “引力波究竟有什么用? 既然你们现在已经探测到了引力波, 下一步要做什么?” 引力波可以被用来做什么呢?
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."
当他们问博尔赫斯(Jorge Luis Borges, 阿根廷作家、诗人),“诗存在的意义是什么?” 他回答道: “绘画的意义是什么? 爱抚的意义是什么? 咖啡香味的意义又是什么?” 他还说: “诗的意义是为了美好、 是为了感情、为了生活而存在的。”
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.
这一点与了解宇宙—— 出于人类渴望了解 万物如何运作的好奇心, 是相似的。 自古以来,人类—— 在我们每一个人还是孩子的时候—— 当我们第一次仰望星空, 看到那些星星的时候, 我们会好奇: “星星是什么?” 正是这种好奇造就了人类。 这也是我们研究科学的原因。
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.
我们认为,引力波的意义在于, 我们打开了一条新的探索宇宙的通道。 在那以前,我们只能通过电磁波 看到来自恒星的光芒。 而现在,我们却可以 听到来自宇宙的声音, 甚至是那些不会发光的东西, 比如引力波。
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Thank you.
谢谢大家!
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But are they useful? Can't we derive any technology from gravitational waves?
但是它们到底有什么用呢? 我们能借助引力波 发展一些新的科技吗?
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.
是的,或许可以。 但是这可能会花费更久的时间, 我们已经开发了探测引力波的技术, 但是对于引力波本身, 也许我们 100 年后 才会发现它们的真正用途。 但是把科学转变成技术 会花费很久的时间, 这也并不是我们做这些事的原因。 所有的科技都是 从科学中发展出来的, 但是我们从事科学是为了享受。 那剩下还有什么要做的? 还有很多。 太多了,这还只是一个开始。
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.
随着我们把探测器做得越来越精确—— 我们仍有很多的工作需要做—— 我们不仅会发现更多的黑洞, 并且能够去分类总结—— 究竟有多少,在哪里, 尺寸究竟有多大; 我们还将能观测到其它的物质: 我们会观测到 中子星融合并转化为黑洞 以及黑洞的诞生过程; 银河系里旋转的恒星 产生的正弦波; 银河系中超新星的爆炸。 我们还将会看到新事物的完整波谱。
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.
我们认为, 我们为人类增加了一种新的感官: 除了视觉, 我们还能够去聆听。 这是天文学的一次革命, 就像伽利略发明了天文望远镜一样。 就像人们把声音 加入了无声电影中一样。 这一切仅仅只是个开始。 我们也认为, 通向科学的道路仍旧十分漫长—— 尽管非常有趣,但也很长—— 同时,我们这个庞大的、 由来自众多国家的科学家组成的 国际组织,会齐心协力 帮助建设那条道路: 我们正在照亮前路—— 尽管有时会遇到艰难险阻—— 并且建设一条可能是 通向宇宙的高速公路。
Thank you.
谢谢大家!
(Applause)
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