CERN's supercollider | Brian Cox

1,242,991 views ・ 2008-04-29

TED


Please double-click on the English subtitles below to play the video.

00:19
This is the Large Hadron Collider.
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It's 27 kilometers in circumference.
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It's the biggest scientific experiment ever attempted.
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Over 10,000 physicists and engineers
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from 85 countries around the world
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have come together over several decades
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to build this machine.
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What we do is we accelerate protons --
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so, hydrogen nuclei --
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around 99.999999
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percent the speed of light.
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Right? At that speed, they go around
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that 27 kilometers 11,000 times a second.
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And we collide them with another beam of protons
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going in the opposite direction.
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We collide them inside giant detectors.
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They're essentially digital cameras.
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And this is the one that I work on, ATLAS.
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You get some sense of the size --
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you can just see these EU standard-size
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people underneath.
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(Laughter)
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You get some sense of the size: 44 meters wide,
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22 meters in diameter, 7,000 tons.
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And we re-create the conditions that were present
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less than a billionth of a second after the universe began
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up to 600 million times a second
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inside that detector -- immense numbers.
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And if you see those metal bits there --
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those are huge magnets that bend
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electrically charged particles,
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so it can measure how fast they're traveling.
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This is a picture about a year ago.
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Those magnets are in there.
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And, again, a EU standard-size, real person,
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so you get some sense of the scale.
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And it's in there that those mini-Big Bangs will be created,
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sometime in the summer this year.
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And actually, this morning, I got an email
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saying that we've just finished, today,
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building the last piece of ATLAS.
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So as of today, it's finished. I'd like to say
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that I planned that for TED,
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but I didn't. So it's been completed as of today.
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(Applause)
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Yeah, it's a wonderful achievement.
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So, you might be asking, "Why?
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Why create the conditions that were present
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less than a billionth of a second after the universe began?"
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Well, particle physicists are nothing if not ambitious.
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And the aim of particle physics is to understand
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what everything's made of, and how everything sticks together.
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And by everything I mean, of course,
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me and you, the Earth, the Sun,
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the 100 billion suns in our galaxy
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and the 100 billion galaxies
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in the observable universe.
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Absolutely everything.
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Now you might say, "Well, OK, but why not just look at it?
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You know? If you want to know what I'm made of, let's look at me."
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Well, we found that as you look back in time,
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the universe gets hotter and hotter,
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denser and denser, and simpler and simpler.
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Now, there's no real reason I'm aware of for that,
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but that seems to be the case.
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So, way back in the early times of the universe,
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we believe it was very simple and understandable.
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All this complexity, all the way to these wonderful things --
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human brains -- are a property of an old
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and cold and complicated universe.
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Back at the start, in the first billionth of a second,
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we believe, or we've observed, it was very simple.
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It's almost like ...
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imagine a snowflake in your hand,
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and you look at it, and it's an incredibly complicated,
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beautiful object. But as you heat it up,
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it'll melt into a pool of water,
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and you would be able to see that, actually, it was just made
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of H20, water.
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So it's in that same sense that we look back in time
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to understand what the universe is made of.
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And, as of today, it's made of these things.
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Just 12 particles of matter,
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stuck together by four forces of nature.
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The quarks, these pink things, are the things that make up protons and neutrons
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that make up the atomic nuclei in your body.
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The electron -- the thing that goes around
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the atomic nucleus --
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held around in orbit, by the way, by the electromagnetic force
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that's carried by this thing, the photon.
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The quarks are stuck together by other things called gluons.
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And these guys, here, they're the weak nuclear force,
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probably the least familiar.
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But, without it, the sun wouldn't shine.
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And when the sun shines, you get copious quantities
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of these things, called neutrinos, pouring out.
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Actually, if you just look at your thumbnail --
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about a square centimeter --
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there are something like 60 billion neutrinos per second
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from the sun, passing
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through every square centimeter of your body.
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But you don't feel them, because the weak force
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is correctly named --
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very short range and very weak,
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so they just fly through you.
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And these particles have been discovered
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over the last century, pretty much.
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The first one, the electron, was discovered in 1897,
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and the last one, this thing called the tau neutrino,
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in the year 2000. Actually just --
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I was going to say, just up the road in Chicago. I know it's a big country,
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America, isn't it?
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Just up the road.
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Relative to the universe, it's just up the road.
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(Laughter)
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So, this thing was discovered in the year 2000,
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so it's a relatively recent picture.
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One of the wonderful things, actually, I find,
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is that we've discovered any of them, when you realize how tiny they are.
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You know, they're a step in size
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from the entire observable universe.
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So, 100 billion galaxies,
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13.7 billion light years away --
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a step in size from that to Monterey, actually,
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is about the same as from Monterey to these things.
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Absolutely, exquisitely minute,
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and yet we've discovered pretty much the full set.
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So, one of my most illustrious forebears
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at Manchester University, Ernest Rutherford,
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discoverer of the atomic nucleus,
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once said, "All science is either physics
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or stamp collecting."
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Now, I don't think he meant to insult
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the rest of science,
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although he was from New Zealand, so it's possible.
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(Laughter)
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But what he meant was that what we've done, really,
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is stamp collect there.
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OK, we've discovered the particles,
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but unless you understand the underlying
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reason for that pattern -- you know, why it's built the way it is --
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really you've done stamp collecting. You haven't done science.
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Fortunately, we have
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probably one of the greatest scientific achievements of the twentieth century
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that underpins that pattern.
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It's the Newton's laws, if you want,
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of particle physics.
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It's called the standard model -- beautifully simple mathematical equation.
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You could stick it on the front of a T-shirt,
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which is always the sign of elegance.
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This is it.
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(Laughter)
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I've been a little disingenuous, because I've expanded it out
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in all its gory detail.
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This equation, though, allows you to calculate everything --
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other than gravity -- that happens in the universe.
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So, you want to know why the sky is blue, why atomic nuclei stick together --
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in principle, you've got a big enough computer --
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why DNA is the shape it is.
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In principle, you should be able to calculate it from that equation.
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But there's a problem.
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Can anyone see what it is?
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A bottle of champagne for anyone that tells me.
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I'll make it easier, actually, by blowing one of the lines up.
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Basically, each of these terms
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refers to some of the particles.
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So those Ws there refer to the Ws, and how they stick together.
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These carriers of the weak force, the Zs, the same.
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But there's an extra symbol in this equation: H.
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Right, H.
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H stands for Higgs particle.
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Higgs particles have not been discovered.
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But they're necessary: they're necessary
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to make that mathematics work.
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So all the exquisitely detailed calculations we can do
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with that wonderful equation
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wouldn't be possible without an extra bit.
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So it's a prediction:
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a prediction of a new particle.
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What does it do?
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Well, we had a long time to come up with good analogies.
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And back in the 1980s, when we wanted the money
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for the LHC from the U.K. government,
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Margaret Thatcher, at the time, said,
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"If you guys can explain, in language
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a politician can understand,
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what the hell it is that you're doing, you can have the money.
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I want to know what this Higgs particle does."
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And we came up with this analogy, and it seemed to work.
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Well, what the Higgs does is, it gives mass to the fundamental particles.
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And the picture is that the whole universe --
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and that doesn't mean just space, it means me as well, and inside you --
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the whole universe is full of something called a Higgs field.
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Higgs particles, if you will.
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The analogy is that these people in a room
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are the Higgs particles.
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Now when a particle moves through the universe,
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it can interact with these Higgs particles.
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But imagine someone who's not very popular moves through the room.
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Then everyone ignores them. They can just pass through the room very quickly,
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essentially at the speed of light. They're massless.
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And imagine someone incredibly important
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and popular and intelligent
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walks into the room.
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They're surrounded by people, and their passage through the room is impeded.
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It's almost like they get heavy. They get massive.
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And that's exactly the way the Higgs mechanism works.
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The picture is that the electrons and the quarks
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in your body and in the universe that we see around us
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are heavy, in a sense, and massive,
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because they're surrounded by Higgs particles.
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They're interacting with the Higgs field.
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If that picture's true,
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then we have to discover those Higgs particles at the LHC.
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If it's not true -- because it's quite a convoluted mechanism,
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although it's the simplest we've been able to think of --
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then whatever does the job of the Higgs particles
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we know have to turn up
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at the LHC.
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So, that's one of the prime reasons we built this giant machine.
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I'm glad you recognize Margaret Thatcher.
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Actually, I thought about making it more culturally relevant, but --
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(Laughter)
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anyway.
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So that's one thing.
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That's essentially a guarantee of what the LHC will find.
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There are many other things. You've heard
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many of the big problems in particle physics.
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One of them you heard about: dark matter, dark energy.
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There's another issue,
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which is that the forces in nature -- it's quite beautiful, actually --
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seem, as you go back in time,
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they seem to change in strength.
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Well, they do change in strength.
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So, the electromagnetic force, the force that holds us together,
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gets stronger as you go to higher temperatures.
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The strong force, the strong nuclear force, which sticks nuclei together,
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gets weaker. And what you see is the standard model --
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you can calculate how these change -- is the forces,
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the three forces, other than gravity,
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almost seem to come together at one point.
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It's almost as if there was one beautiful
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kind of super-force, back at the beginning of time.
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But they just miss.
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Now there's a theory called super-symmetry,
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which doubles the number of particles in the standard model,
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which, at first sight, doesn't sound like a simplification.
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But actually, with this theory,
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we find that the forces of nature
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do seem to unify together, back at the Big Bang --
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absolutely beautiful prophecy. The model wasn't built to do that,
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but it seems to do it.
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Also, those super-symmetric particles
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are very strong candidates for the dark matter.
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So a very compelling theory
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that's really mainstream physics.
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And if I was to put money on it, I would put money on --
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in a very unscientific way -- that
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that these things would also crop up at the LHC.
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Many other things that the LHC could discover.
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But in the last few minutes, I just want to give you
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a different perspective
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of what I think -- what particle physics
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really means to me -- particle physics and cosmology.
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And that's that I think it's given us a wonderful
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narrative -- almost a creation story,
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if you'd like -- about the universe,
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from modern science over the last few decades.
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And I'd say that it deserves,
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in the spirit of Wade Davis' talk,
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to be at least put up there with these wonderful creation stories
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of the peoples of the high Andes and the frozen north.
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This is a creation story, I think, equally as wonderful.
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The story goes like this: we know that
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the universe began 13.7 billion years ago,
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in an immensely hot, dense state,
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much smaller than a single atom.
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It began to expand about
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a million, billion, billion, billion billionth
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of a second -- I think I got that right -- after the Big Bang.
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Gravity separated away from the other forces.
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The universe then underwent
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an exponential expansion called inflation.
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In about the first billionth of a second or so,
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the Higgs field kicked in, and the quarks
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and the gluons and the electrons
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that make us up got mass.
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The universe continued to expand and cool.
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After about a few minutes,
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there was hydrogen and helium in the universe. That's all.
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The universe was about 75 percent hydrogen,
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25 percent helium. It still is today.
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It continued to expand
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about 300 million years.
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Then light began to travel through the universe.
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It was big enough to be transparent to light,
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and that's what we see in the cosmic microwave background
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that George Smoot described
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as looking at the face of God.
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After about 400 million years, the first stars formed,
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and that hydrogen, that helium, then began to cook
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into the heavier elements.
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So the elements of life --
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carbon, and oxygen and iron,
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all the elements that we need to make us up --
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were cooked in those first generations of stars,
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which then ran out of fuel, exploded,
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threw those elements back into the universe.
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They then re-collapsed into another generation
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of stars and planets.
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And on some of those planets, the oxygen, which had been created
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in that first generation of stars, could fuse with hydrogen
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to form water, liquid water on the surface.
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On at least one, and maybe only one of those planets,
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primitive life evolved,
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which evolved over millions of years into
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things that walked upright and left footprints
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about three and a half million years ago in the mud flats of Tanzania,
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and eventually
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left a footprint on another world.
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And built this civilization,
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this wonderful picture,
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that turned the darkness into light,
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and you can see the civilization from space.
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As one of my great heroes, Carl Sagan, said,
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these are the things -- and actually, not only these,
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but I was looking around -- these are the things,
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like Saturn V rockets, and Sputnik,
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and DNA, and literature and science --
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these are the things that hydrogen atoms do
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when given 13.7 billion years.
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Absolutely remarkable.
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And, the laws of physics. Right?
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So, the right laws of physics --
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they're beautifully balanced.
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If the weak force had been a little bit different,
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then carbon and oxygen wouldn't be stable
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inside the hearts of stars,
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and there would be none of that in the universe.
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And I think that's
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a wonderful and significant story.
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50 years ago, I couldn't have told that story,
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because we didn't know it.
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It makes me really feel that
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that civilization --
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which, as I say, if you believe
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the scientific creation story,
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has emerged purely as a result of the laws of physics,
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and a few hydrogen atoms --
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then I think, to me anyway,
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it makes me feel incredibly valuable.
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So that's the LHC.
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The LHC is certainly, when it turns on in summer,
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going to write the next chapter of that book.
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And I'm certainly looking forward with
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immense excitement to it being turned on.
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Thanks.
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(Applause)
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Original video on YouTube.com
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