Brian Cox :CERN大型強子對撞機

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http://dotsub.com/view/65e9648d-2955-47f7-9dea-3700f5d1b925
Brian Cox :CERN大型強子對撞機
这就是大型强子对撞机 它周长27公里 是有史以来开展过最大的科学实验 超过10000名物理学家和工程师 来自全球85个国家 共同在几十年的时间里 建造了这部机器 我们用它将质子—— 也就是氢原子核—— 的运动速度加到 光速的99.999999% 了解？以这种速度，他们每秒 环绕27公里的轨道11000次 然后我们使它与另一束 来自相反方向的质子相撞 我们使质子在巨型探测器内对撞
探测器基本上就是数码相机 而这是我所任职的那台，ATLAS 你可以得到些尺寸上的概念 你可以看到这些欧洲标准尺寸 的人在那下面
（笑）
你能有点概念：44米长 直径22米，重7000吨。 我们所要重塑的 是宇宙形成十亿分之一秒后的状态 每秒制造大约6亿次这一状态 在这个探测器内部——天文数字 如果你看到那里的那些小金属块 它们是巨型磁铁，用于弯折 带电粒子 使探测器能够测算出粒子运动的速度 这是大概一年前的照片 有那些磁铁在上面 再一次重申，有一个欧洲标准身高的人 在那里给你一些尺寸上的概念 这就是那些迷你大爆炸将要被批量制造的地方 在今年夏天的时候
事实上，今天早晨，我收到一封邮件 说我们今天刚刚完成 建造ATLAS的最后一个环节 就是说今天，我们竣工了。我想说 这是我特意为TED安排的 但实际上不是。不过无论怎样，它完成了
（鼓掌）
没错，这是项伟大的成就 那，你可能会问，“为什么？ 为什么要制造那个 宇宙形成十亿分之一秒后的状态？” 嗯，如果没有野心就当不成粒子物理学家 而粒子物理学的目标就是要了解 所有一切是从何而来，又如何组建 当然，所谓“一切”，我的意思是 我和你，地球，太阳 我们银河系中的几千亿个太阳 和存在在可观测的宇宙中 的那几千亿个银河系 绝对是一切事物
现在你可能会说，“那，好吧，但是干嘛不直接观察它？ 明白么？如果你想知道我是拿什么做的，那我们就来看看我。“ 嗯，我们发现，当你回溯时间， 宇宙会越来越热 越来越致密，越来越单一 现今为止我不能告诉你我为什么知道这个 不过事实貌似就是如此 所以，回到宇宙形成初期 我们认为它是非常简单易懂的 所有繁复的衍生，所有这些美妙的事物—— 包括人脑——都是 一个古老，苍凉而又精密的宇宙的产物 在宇宙的起点，第一个十亿分之一秒 我们相信，或者我们发现，它是非常纯粹的
这就好像 想象你手里有一片雪花 当你观察它，会发现它是如此精致 如此美丽的事物。但当你散发出热量 它就会融化成一小滩水 这时你就能看到其实它不过是 H2O，水形成的 同样道理可以解释为什么我们从初始状态 开始认知宇宙的形成 如今我们发现，它由这些形成 12种物质微粒 在4种自然力的作用下结合在一起 夸克，这些粉色的东西，是构成质子和中子的粒子 质子和中子组成你身体里的原子核 电子——那个绕着 原子核运动的东西—— 被制约在一个由电磁力控制的轨道上 而电磁力由这个东西携带，光子 将夸克结合在一起的东西叫做胶子
然后是这些家伙，这儿，他们是弱核力 大概是最不为人所知的 但是如果没有它们太阳就不会发光 当太阳发光的时候，大量的 中微子被放射出来 事实上，如果你看向你的指甲—— 大概一平方厘米的面积——那儿大概有 每秒大概有600亿个中微子 来自太阳，穿过 你身上的每一个平方厘米 但是你感觉不到他们，因为 弱力这个名字不是白起的 非常短暂非常微弱 所以它们可以直接穿过你
这些粒子被发现的过程 几乎持续了上世纪整整一世纪 第一个，电子，是1897年被发现的 然而最后一个，这个叫做陶子微中子的东西 是2000年被发现的。其实—— 我刚才想说，就是在马路那头的芝加哥，但是我反应过来了 美国超大的，是吧？ 就在马路那头 相对宇宙来说就在马路那头
（笑）
所以，这整套东西是2000年被完整发现的 可以说是一个非常年轻的成就 我发现这之中一个非常美妙的事 实际上是，无论发现任何一个都是一样，当你意识到它们竟是如此的微小 就好像，它们的数量级 基本等同于整个可观测的宇宙的数量级 就是说，1000亿个银河系 137亿光年的距离—— 和康乐区（加州一小镇）相比的数量级差 实际上就差不多是康乐区和这些小东西相比的数量级差 完全的，极致的微小 但我们几乎还是全部发现了它们
嗯，我有一个著名的前辈 在曼彻斯特大学，鄂尼斯特，拉特福德 原子核的发现者 曾经说：所有的科学不是物理 就是集邮 呃，我不认为他是故意羞辱 其它的科学 不过他是新西兰人，所以也说不准
（笑）
但是他的意思其实是，我们所做的一切 其实就是在集邮—— 好，我们发现了这些粒子 但是除非你明白了这背后 这现象的原理——就是，为什么它们如此集结—— 那你所做的就是集邮——你没有把它总结成科学 幸运的是，我们总结出来了 可能是20世纪最伟大的科学成就之一 这现象背后的理论 如果你愿意，可以把它想成 粒子物理界的牛顿定律 它叫做”标准模型“——漂亮简单的数学等式 你可以把它贴在T恤胸前 显示你是一个文化人 这就是它
（笑）
我有点不老实，因为我把它展开了 所有血淋淋的细节 不过这个等式，允许你计算任何事—— 除了引力——只要是在这个宇宙里的 假设你想知道为什么天是蓝的，为什么原子核结合在一起—— 理论上来说，如果你有一台足够强大的电脑—— 为什么DNA是这样的 原则上讲，你应该可以通过这个等式计算出来
但是这有一个问题 谁能看出来是什么？ 谁告诉我问题在哪奖一瓶香槟 我把难度降低点儿吧， 把其中的一行放大 基本上，这上面每一个参数 都代表一个粒子 就是说，那些W就代表弱力，还有粒子是如何结合的 同样道理这些Z代表弱力的携带者 但是这个等式里多了一个符号，H 对，H H代表希格斯介子 我们还没发现希格斯介子 但是它们是必要的—— 没有它们等式就无法成立 所以，所有理论上用这个美妙等式 所能做出的精确计算 都不能缺少这关键的一点 所以这是个推论 对一个新粒子的预测
它是干什么的？ 嗯，我们花了很长时间去想拿什么跟它类比才合适 上世纪80年代，当时我们想向英国政府 申请资金继续在LHC的工作 撒切尔夫人，当时她当政，跟我们说 “如果你们能用 政治家听的懂的语言解释清楚 你们在搞什么鬼东西，我就拨给你们钱， 我想知道这个希格斯介子是干嘛的。” 于是我们想出了这个比较合适的类比 这样，希格斯介子是干嘛的呢？它给予基本粒子质量 也就是说整个宇宙—— 不光是太空，也包括我，还有你—— 整个宇宙都充斥着这种叫做希格斯场的东西 希格斯介子，如果你绕不过来
这个比方是这样的：这些在屋子里的人 他们就是希格斯介子 当一个粒子穿过宇宙 它就会与希格斯介子发生联系 但是假设一个不怎么受欢迎的人穿过这个房间 那样所有人都会无视他。它们（粒子）就能很快的穿过空间 基本以光速穿过。它们没有质量 但是如果是一个无比重要 人气爆高智慧超群的人 穿过这个房间 她就会被人们团团围住，前进的路也障碍重重 就好像它们（粒子）变沉重了，变大了 这就是希格斯介子的工作机制 也就是说电子和夸克 这些组成我们和我们可见的宇宙的粒子 之所以重，或者在某种意义上说，大 是因为它们被希格斯介子所包围 它们与希格斯场产生联系
如果这推论是真的 那么我们就必须在LHC发现这些希格斯介子 如果不是——因为这是一个非常繁复的机制 虽然它已经是我们能想到的最简单的一个—— 那无论这个担任希格斯介子角色的东西是什么 我们知道它都会 出现在LHC 这就是我们建造这个庞然大物的主要原因之一 你们能认出撒切尔太好了 真的，我还想我应该找个更具文化共通性的——
（笑） 随便啦 所以这基本上 是LHC一定能获得的成果之一
还有很多别的东西，你一定听说过 很多别的粒子物理领域中的大课题 其中你听过暗物质，暗能量 这是另外一个课题 就是自然力——这个现象非常奇妙—— 当你回到过去，就能看到 它们的力度会随着时间推移而变化 对，它们真的会变 就像电磁力，把我们结合在一起的力 温度越高越强 而强力，或者说核力，使原子核结合在一起的力 温度越高越弱。在这里你看到的是标准模型—— 你可以计算出这些力如何变化—— 除了引力以外的三种力—— 它们几乎相交于一点 就好像那里有一种美妙的 超级自然力，形成于时间之始 但它们还是岔开了
现在有一种理论叫做“超对称性理论” 它将标准模型中的粒子数翻倍 这乍一看不像是在简化问题 但事实是，当我们这样做 我们发现这三个自然力 似乎真的在宇宙大爆炸的时候融为一体 无比完美的预言。建这个模型的时候人们没有想到 能够得到的如此巨大的回报 还有，这些超对称粒子 非常有可能就是暗物质 一个非常迷人的理论 这是目前的主流物理 如果我要给现代物理投资，我肯定投给它—— 用一个非科学的方式表达我的意思—— 而这些问题的答案也会在LHC得到 LHC还能发现很多其它东西
但是在最后的几分钟里，我只想给你们 提供一个不同的角度 关于我认为粒子物理 到底意义何在——粒子物理和宇宙学 这就是我认为它们给了我们一个美妙的 诠释——你可以把它想成 一个关于宇宙形成的故事—— 这诠释来自于近几十年的现代科学 而它至少能够 ——本着韦德讲话的精神—— 与那些意义深远的关于安第斯高山人和北方冰原人们 的开拓事迹相比肩 我想，这是一个同样伟大的故事
故事是这样的：我们知道 宇宙形成于137亿年前 起始于一个极度高温致密的状态 体积远比一个原子更小 在大爆炸 10亿亿亿亿亿分之一秒后 开始扩张——我觉得我没记错数据—— 引力与其它力分隔开来 宇宙开始进入一个 呈指数级扩张的阶段，叫做暴涨期 在大约十亿分之一秒后 希格斯场形成，然后夸克 胶子和电子这些基本粒子 获得了质量 宇宙继续扩展，冷却 大概几分钟以后 氢和氦出现在宇宙中。就是这样 宇宙由75%的氢和 25%的氦形成，直到今天仍是这样
它继续扩张了大约 3亿年 光线开始穿过宇宙空间 此时的宇宙已经大到足以透明 而这就是我们所看到的宇宙微波背景 乔治斯穆特所说的 直视上帝的面孔 大约4亿年后，第一颗星形成 然后氢啊氦啊，开始结合 形成重元素 于是生命元素—— 碳，氧和铁 所有我们生命所必须的元素—— 在第一代恒星中孕育而成 但此时恒星寿命已尽，它们爆炸 将那些元素重新抛回宇宙 它们再次挤压，形成新一代的 恒星和行星
在其中的一些行星上，那些在第一代恒星上 形成的氧元素与氢元素结合 形成了水。星球表面的液态水 在其中至少一个，或许是唯一一个行星上 初态生命诞生 它们经过几百万年的进化 学会了直立行走并且于 350万年前在坦桑尼亚的泥原上留下了脚印 直到最终 踏上了另一颗星球的表面 他们建立了文明 这一光辉的图景 用电光照亮黑暗 使这世界能够瞭然于宇宙 就像我的一位偶像，卡尔撒甘所说 这些——事实上不止这些 当我环视四周——这些东西 神农五号运载火箭，伴侣号卫星 DNA，文学，科学——这些就是 一粒被赋予了137亿年时间的氢原子 所造就的世界
绝对的神奇 还有，就是物理定律，对吧？ 所以，真正的物理定律 都精妙地平衡 如果弱力有一点点偏差 那么就不能形成星球内部 稳定的氧和碳 宇宙里就不会存在任何星球 我认为这是一个 辉煌壮美的故事 50年前我是无法讲述这个故事的 因为那时我们不知道一切是怎么回事 这让我越来越笃定的认为 文明的发展—— 前提是，如果你相信 科学的创始学说—— 完全是物理定律和几个氢原子的 演化结果 于是我认为，至少对我自己来说 这文明无比珍贵
这就是LHC 当LHC在这个夏天被启动， 它必将会书写这文明发展的崭新篇章 而我也会怀着无比激动的心情 期待着这一天的到来 谢谢
（鼓掌）

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Brian Cox on CERN's supercollider
This is the Large Hadron Collider. It's 27 kilometers in circumference; it's the biggest scientific experiment ever attempted. Over 10,000 physicists and engineers from 85 countries around the world have come together over several decades to build this machine. What we do is we accelerate protons -- so, hydrogen nuclei -- around 99.999999 percent the speed of light. Right? At that speed, they go around that 27 kilometers 11,000 times a second. And we collide them with another beam of protons going in the opposite direction. We collide them inside giant detectors.

They're essentially digital cameras. And this is the one that I work on, ATLAS. You get some sense of the size -- you can just see these EU standard-size people underneath.

(Laughter)

You get some sense of the size: 44 meters wide, 22 meters in diameter, 7,000 tons. And we re-create the conditions that were present less than a billionth of a second after the universe began -- up to 600 million times a second inside that detector -- immense numbers. And if you see those metal bits there -- those are huge magnets that bend electrically-charged particles, so it can measure how fast they're traveling. This is a picture about a year ago. Those magnets are in there. And, again, an EU standard-size real person, so you get some sense of the scale. And it's in there that those mini-Big Bangs will be created, sometime in the summer this year.

And actually, this morning, I got an email saying that we've just finished, today, building the last piece of ATLAS. So as of today, it's finished. I'd like to say that I planned that for TED, but I didn't. So it's been completed as of today.

(Applause)

Yeah, it's a wonderful achievement. So, you might be asking, "Why? Why create the conditions that were present less than a billionth of a second after the universe began?" Well, particle physicists are nothing if not ambitious. And the aim of particle physics is to understand what everything's made of, and how everything sticks together. And by "everything" I mean, of course, me and you, the Earth, the Sun, the hundred billion suns in our galaxy and the hundred billion galaxies in the observable universe. Absolutely everything.

Now you might say, "Well, OK, but why not just look at it? You know? If you want to know what I'm made of, let's look at me." Well, we found that as you look back in time, the universe gets hotter and hotter, denser and denser, and simpler and simpler. Now, there's no real reason I'm aware of for that, but that seems to be the case. So, way back in the early times of the universe, we believe it was very simple and understandable. All this complexity, all the way to these wonderful things -- human brains -- are a property of an old and cold and complicated universe. Back at the start, in the first billionth of a second, we believe, or we've observed, it was very simple.

It's almost like ... imagine a snowflake in your hand, and you look at it, and it's an incredibly complicated, beautiful object. But as you heat it up, it'll melt into a pool of water, and you would be able to see that actually it was just made of H20, water. So it's in that same sense that we look back in time to understand what the universe is made of. And as of today, it's made of these things. Just 12 particles of matter, stuck together by four forces of nature. The quarks, these pink things, are the things that make up protons and neutrons that make up the atomic nuclei in your body. The electron -- the thing that goes around the atomic nucleus -- held around in orbit, by the way, by the electromagnetic force that's carried by this thing, the photon. The quarks are stuck together by other things called gluons.

And these guys, here, they're the weak nuclear force, probably the least familiar. But without it the sun wouldn't shine. And when the sun shines, you get copious quantities of these things called neutrinos pouring out. Actually, if you just look at your thumbnail -- about a square centimeter -- there are something there are something like 60 billion neutrinos per second from the sun, passing through every square centimeter of your body. But you don't feel them because the weak force is correctly named. Very short range and very weak, so they just fly through you.

And these particles have been discovered over the last century, pretty much. The first one, the electron, was discovered in 1897, and the last one, this thing called the tau neutrino, in the year 2000. Actually just -- I was going to say, just up the road in Chicago. I know it's a big country, America, isn't it? Just up the road. Relative to the universe, it's just up the road.

(Laughter)

So, this thing was discovered in the year 2000, so it's a relatively recent picture. One of the wonderful things, actually, I find, is that we've discovered any of them, when you realize how tiny they are. You know, they're a step in size from the entire observable universe. So 100 billion galaxies, 13.7 billion light years away -- a step in size from that to Monterey, actually, is about the same as from Monterey to these things. Absolutely, exquisitely minute, and yet we've discovered pretty much the full set.

So, one of my most illustrious forebears at Manchester University, Ernest Rutherford, discoverer of the atomic nucleus, once said, "All science is either physics or stamp collecting." Now, I don't think he meant to insult the rest of science, although he was from New Zealand, so it's possible.

(Laughter)

But what he meant was that what we've done, really, is stamp collect there -- OK, we've discovered the particles, but unless you understand the underlying reason for that pattern -- you know, why it's built the way it is -- really you've done stamp collecting -- you haven't done science. Fortunately, we have probably one of the greatest scientific achievements of the 20th century that underpins that pattern. It's the Newton's laws, if you want, of particle physics. It's called the "standard model" -- beautifully simple mathematical equation. You could stick it on the front of a t-shirt, which is always the sign of elegance. This is it.

(Laughter)

I've been a little disingenuous, because I've expanded it out in all it's gory detail. This equation, though, allows you to calculate everything -- other than gravity -- that happens in the universe. So you want to know why the sky is blue, why atomic nuclei stick together -- in principle, you've got a big enough computer -- why DNA is the shape it is. In principle, you should be able to calculate it from that equation.

But there's a problem. Can anyone see what it is? A bottle of champagne for anyone that tells me. I'll make it easier, actually, by blowing one of the lines up. Basically, each of these terms refers to some of the particles. So those Ws there refer to the Ws, and how they stick together. These carriers of the weak force, the Zeds, the same. But there's an extra symbol in this equation: H. Right, H. H stands for Higgs particle. Higgs particles have not been discovered. But they're necessary -- they're necessary to make that mathematics work. So all the exquisitely detailed calculations we can do with that wonderful equation wouldn't be possible without an extra bit. So it's a prediction -- a prediction of a new particle.

What does it do? Well, we had a long time to come up with good analogies. And back in the 1980s, when we wanted the money for the LHC from the UK government, Margaret Thatcher, at the time, said, "If you guys can explain, in language a politician can understand, what the hell it is that you're doing, you can have the money. I want to know what this Higgs particle does." And we came up with this analogy and it seemed to work. Well, what the Higgs does is, it gives mass to the fundamental particles. And the picture is that the whole universe -- and that doesn't mean just space, it means me as well, and inside you -- the whole universe is full of something called a Higgs field. Higgs particles, if you will.

The analogy is that these people in a room are the Higgs particles. Now when a particle moves through the universe, it can interact with these Higgs particles. But imagine someone who's not very popular moves through the room. Then everyone ignores them. They can just pass through the room very quickly, essentially at the speed of light. They're massless. And imagine someone incredibly important and popular and intelligent walks into the room. They're surrounded by people, and their passage through the room is impeded. It's almost like they get heavy. They get massive. And that's exactly the way the Higgs mechanism works. The picture is that the electrons and the quarks in your body and in the universe that we see around us are heavy, in a sense, and massive, because they're surrounded by Higgs particles. They're interacting with the Higgs field.

If that picture's true, then we have to discover those Higgs particles at the LHC. If it's not true -- because it's quite a convoluted mechanism, although it's the simplest we've been able to think of -- then whatever does the job of the Higgs particles we know have to turn up at the LHC. So that's one of the prime reasons we built this giant machine. I'm glad you recognize Margaret Thatcher. Actually, I thought about making it more culturally relevant, but -- (Laughter) anyway. So that's one thing. That's essentially a guarantee of what the LHC will find.

There are many other things. You've heard many of the big problems in particle physics. One of them you heard about: dark matter, dark energy. There's another issue, which is that the forces in nature -- it's quite beautiful, actually -- seem, as you go back in time, they seem to change in strength. Well, they do change in strength. So the electromagnetic force, the force that holds us together, gets stronger as you go to higher temperatures. The strong force, the strong nuclear force, which sticks nuclei together, gets weaker. And what you see is the standard model -- you can calculate how these change -- is the forces -- the three forces, other than gravity -- almost seem to come together at one point. It's almost as if there was one beautiful kind of super-force, back at the beginning of time. But they just miss.

Now there's a theory called supersymmetry, which doubles the number of particles in the standard model. Which, at first sight, doesn't sound like a simplification. But actually, with this theory, we find that the forces of nature do seem to unify together, back at the Big Bang. Absolutely beautiful prophecy. The model wasn't built to do that, but it seems to do it. Also, those supersymmetric particles are very strong candidates for the dark matter. So a very compelling theory that's really mainstream physics. And if I was to put money on it, I would put money on -- in a very unscientific way -- that that these things would also crop up at the LHC. Many other things that the LHC could discover.

But in the last few minutes, I just want to give you a different perspective of what I think -- what particle physics really means to me -- particle physics and cosmology. And that's that I think it's given us a wonderful narrative -- almost a creation story, if you'd like -- about the universe, from modern science over the last few decades. And I'd say that it deserves, in the spirit of Wade Davis' talk, to be at least put up there with these wonderful creation stories of the peoples of the high Andes and the frozen north. This is a creation story, I think, equally as wonderful.

The story goes like this: we know that the universe began 13.7 billion years ago, in an immensely hot, dense state, much smaller than a single atom. It began to expand about a million billion billion billion billionth of a second -- I think I got that right -- after the Big Bang. Gravity separated away from the other forces. The universe then underwent an exponential expansion called inflation. In about the first billionth of a second or so, the Higgs field kicked in, and the quarks and the gluons and the electrons that make us up got mass. The universe continued to expand and cool. After about a few minutes, there was hydrogen and helium in the universe. That's all. The universe was about 75 percent hydrogen, 25 percent helium. It still is today.

It continued to expand about 300 million years. Then light began to travel through the universe. It was big enough to be transparent to light, and that's what we see in the cosmic microwave background that George Smoot described as looking at the face of God. After about 400 million years, the first stars formed, and that hydrogen, that helium, then began to cook into the heavier elements. So the elements of life -- carbon, and oxygen and iron, all the elements that we need to make us up -- were cooked in those first generations of stars, which then ran out of fuel, exploded, threw those elements back into the universe. They then re-collapsed into another generation of stars and planets.

And on some of those planets, the oxygen which had been created in that first generation of stars could fuse with hydrogen to form water, liquid water on the surface. On at least one, and on maybe only one of those planets, primitive life evolved, which evolved over millions of years into things that walked upright and left footprints about three and a half million years ago in the mud flats of Tanzania, and eventually left a footprint on another world. And built this civilization, this wonderful picture, that turned the darkness into light, and you can see the civilization from space. As one of my great heroes, Carl Sagan, said, these are the things -- and actually, not only these, but I was looking around -- these are the things, like Saturn V rockets, and Sputnik, and DNA, and literature and science -- these are the things that hydrogen atoms do when given 13.7 billion years.

Absolutely remarkable. And, the laws of physics. Right? So, the right laws of physics -- they're beautifully balanced. If the weak force had been a little bit different, then carbon and oxygen wouldn't be stable inside the hearts of stars, and there would be none of that in the universe. And I think that's a -- a wonderful and significant story. 50 years ago I couldn't have told that story, because we didn't know it. It makes me really feel that that civilization -- which, as I say, if you believe the scientific creation story, has emerged purely as a result of the laws of physics, and a few hydrogen atoms -- then I think, to me anyway, it makes me feel incredibly valuable.

So that's the LHC. The LHC is certainly, when it turns on in summer, going to write the next chapter of that book. And I'm certainly looking forward with immense excitement to it being turned on. Thanks.

(Applause)