ted演讲稿98377

精品文库Brian Cox: CERNs supercolliderThis is the Large Hadron Collider. Its 27 kilometers in circumference. Its 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. Theyre 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 theyre traveling. This is a picture about a year ago. Those magnets are in there. And, again, a EU standard-size, real person, so you get some sense of the scale. And its 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 weve just finished, today, building the last piece of ATLAS. So as of today, its finished. Id like to say that I planned that for TED, but I didnt. So its been completed as of today. (Applause) Yeah, its 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 everythings made of, and how everything sticks together. And by everything I mean, of course, me and you, the Earth, the Sun, the 100 billion suns in our galaxy and the 100 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 Im made of, lets 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, theres no real reason Im 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 weve observed, it was very simple. Its almost like . imagine a snowflake in your hand, and you look at it, and its an incredibly complicated, beautiful object. But as you heat it up, itll melt into a pool of water, and you would be able to see that, actually, it was just made of H20, water. So its in that same sense that we look back in time to understand what the universe is made of. And, as of today, its 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 thats carried by this thing, the photon. The quarks are stuck together by other things called gluons. And these guys, here, theyre the weak nuclear force, probably the least familiar. But, without it, the sun wouldnt 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 like 60 billion neutrinos per second from the sun, passing through every square centimeter of your body. But you dont 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 its a big country, America, isnt it? Just up the road. Relative to the universe, its just up the road. (Laughter) So, this thing was discovered in the year 2000, so its a relatively recent picture. One of the wonderful things, actually, I find, is that weve discovered any of them, when you realize how tiny they are. You know, theyre 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 weve 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 dont think he meant to insult the rest of science, although he was from New Zealand, so its possible. (Laughter) But what he meant was that what weve done, really, is stamp collect there. OK, weve discovered the particles, but unless you understand the underlying reason for that pattern - you know, why its built the way it is - really youve done stamp collecting. You havent done science. Fortunately, we have probably one of the greatest scientific achievements of the twentieth century that underpins that pattern. Its the Newtons laws, if you want, of particle physics. Its 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) Ive been a little disingenuous, because Ive expanded it out in all its 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, youve 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 theres a problem. Can anyone see what it is? A bottle of champagne for anyone that tells me. Ill 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 Zs, the same. But theres an extra symbol in this equation: H. Right, H. H stands for Higgs particle. Higgs particles have not been discovered. But theyre necessary: theyre necessary to make that mathematics work. So all the exquisitely detailed calculations we can do with that wonderful equation wouldnt be possible without an extra bit. So its 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 U.K. government, Margaret Thatcher, at the time, said, If you guys can explain, in language a politician can understand, what the hell it is that youre 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 doesnt 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 whos 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. Theyre massless. And imagine someone incredibly important and popular and intelligent walks into the room. Theyre surrounded by people, and their passage through the room is impeded. Its almost like they get heavy. They get massive. And thats 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 theyre surrounded by Higgs particles. Theyre interacting with the Higgs field. If that pictures true, then we have to discover those Higgs particles at the LHC. If its not true - because its quite a convoluted mechanism, although its the simplest weve been able to think of - then whatever does the job of the Higgs particles we know have to turn up at the LHC. So, thats one of the prime reasons we built this giant machine. Im glad you recognize Margaret Thatcher. Actually, I thought about making it more culturally relevant, but - (Laughter) anyway. So thats one thing. Thats essentially a guarantee of what the LHC will find. There are many other things. Youve heard many of the big problems in particle physics. One of them you heard about: dark matter, dark energy. Theres another issue, which is that the forces in nature - its 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. Its almost as if there was one beautiful kind of super-force, back at the beginning of time. But they just miss. Now theres a theory called super-symmetry, which doubles the number of particles in the standard model, which, at first sight, doesnt 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 wasnt built to do that, but it seems to do it. Also, those super-symmetric particles are very strong candidates for the dark matter. So a very compelling theory thats 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 thats that I think its given us a wonderful narrative - almost a creation story, if youd like - about the universe, from modern science over the last few decades. And Id 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. Thats 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 thats 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 maybe only one of those planets, primitive life evolved, which evolved over millions of years into things that walked up