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TED2008

Brian Cox: CERN's supercollider

March 3, 2008

"Rock-star physicist" Brian Cox talks about his work on the Large Hadron Collider at CERN. Discussing the biggest of big science in an engaging, accessible way, Cox brings us along on a tour of the massive project.

Brian Cox - Physicist
Physicist Brian Cox has two jobs: working with the Large Hadron Collider at CERN, and explaining big science to the general public. He's a professor at the University of Manchester. Full bio

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Double-click the English subtitles below to play the video.
This is the Large Hadron Collider.
00:19
It's 27 kilometers in circumference.
00:22
It's the biggest scientific experiment ever attempted.
00:24
Over 10,000 physicists and engineers
00:27
from 85 countries around the world
00:30
have come together over several decades
00:32
to build this machine.
00:34
What we do is we accelerate protons --
00:36
so, hydrogen nuclei --
00:38
around 99.999999
00:40
percent the speed of light.
00:44
Right? At that speed, they go around
00:46
that 27 kilometers 11,000 times a second.
00:48
And we collide them with another beam of protons
00:52
going in the opposite direction.
00:54
We collide them inside giant detectors.
00:57
They're essentially digital cameras.
00:59
And this is the one that I work on, ATLAS.
01:01
You get some sense of the size --
01:03
you can just see these EU standard-size
01:05
people underneath.
01:07
(Laughter)
01:09
You get some sense of the size: 44 meters wide,
01:11
22 meters in diameter, 7,000 tons.
01:14
And we re-create the conditions that were present
01:17
less than a billionth of a second after the universe began
01:20
up to 600 million times a second
01:23
inside that detector -- immense numbers.
01:25
And if you see those metal bits there --
01:29
those are huge magnets that bend
01:31
electrically charged particles,
01:33
so it can measure how fast they're traveling.
01:35
This is a picture about a year ago.
01:37
Those magnets are in there.
01:39
And, again, a EU standard-size, real person,
01:41
so you get some sense of the scale.
01:43
And it's in there that those mini-Big Bangs will be created,
01:46
sometime in the summer this year.
01:48
And actually, this morning, I got an email
01:50
saying that we've just finished, today,
01:52
building the last piece of ATLAS.
01:54
So as of today, it's finished. I'd like to say
01:56
that I planned that for TED,
01:58
but I didn't. So it's been completed as of today.
02:00
(Applause)
02:03
Yeah, it's a wonderful achievement.
02:07
So, you might be asking, "Why?
02:09
Why create the conditions that were present
02:11
less than a billionth of a second after the universe began?"
02:13
Well, particle physicists are nothing if not ambitious.
02:16
And the aim of particle physics is to understand
02:19
what everything's made of, and how everything sticks together.
02:22
And by everything I mean, of course,
02:25
me and you, the Earth, the Sun,
02:27
the 100 billion suns in our galaxy
02:30
and the 100 billion galaxies
02:33
in the observable universe.
02:35
Absolutely everything.
02:37
Now you might say, "Well, OK, but why not just look at it?
02:39
You know? If you want to know what I'm made of, let's look at me."
02:41
Well, we found that as you look back in time,
02:44
the universe gets hotter and hotter,
02:47
denser and denser, and simpler and simpler.
02:50
Now, there's no real reason I'm aware of for that,
02:53
but that seems to be the case.
02:55
So, way back in the early times of the universe,
02:58
we believe it was very simple and understandable.
03:00
All this complexity, all the way to these wonderful things --
03:03
human brains -- are a property of an old
03:06
and cold and complicated universe.
03:08
Back at the start, in the first billionth of a second,
03:11
we believe, or we've observed, it was very simple.
03:14
It's almost like ...
03:16
imagine a snowflake in your hand,
03:18
and you look at it, and it's an incredibly complicated,
03:20
beautiful object. But as you heat it up,
03:23
it'll melt into a pool of water,
03:26
and you would be able to see that, actually, it was just made
03:29
of H20, water.
03:31
So it's in that same sense that we look back in time
03:34
to understand what the universe is made of.
03:36
And, as of today, it's made of these things.
03:39
Just 12 particles of matter,
03:42
stuck together by four forces of nature.
03:44
The quarks, these pink things, are the things that make up protons and neutrons
03:48
that make up the atomic nuclei in your body.
03:51
The electron -- the thing that goes around
03:54
the atomic nucleus --
03:56
held around in orbit, by the way, by the electromagnetic force
03:58
that's carried by this thing, the photon.
04:01
The quarks are stuck together by other things called gluons.
04:03
And these guys, here, they're the weak nuclear force,
04:06
probably the least familiar.
04:08
But, without it, the sun wouldn't shine.
04:10
And when the sun shines, you get copious quantities
04:12
of these things, called neutrinos, pouring out.
04:14
Actually, if you just look at your thumbnail --
04:17
about a square centimeter --
04:20
there are something like 60 billion neutrinos per second
04:23
from the sun, passing
04:26
through every square centimeter of your body.
04:28
But you don't feel them, because the weak force
04:30
is correctly named --
04:32
very short range and very weak,
04:34
so they just fly through you.
04:36
And these particles have been discovered
04:38
over the last century, pretty much.
04:40
The first one, the electron, was discovered in 1897,
04:42
and the last one, this thing called the tau neutrino,
04:44
in the year 2000. Actually just --
04:47
I was going to say, just up the road in Chicago. I know it's a big country,
04:49
America, isn't it?
04:52
Just up the road.
04:55
Relative to the universe, it's just up the road.
04:58
(Laughter)
05:01
So, this thing was discovered in the year 2000,
05:03
so it's a relatively recent picture.
05:05
One of the wonderful things, actually, I find,
05:08
is that we've discovered any of them, when you realize how tiny they are.
05:10
You know, they're a step in size
05:13
from the entire observable universe.
05:15
So, 100 billion galaxies,
05:17
13.7 billion light years away --
05:19
a step in size from that to Monterey, actually,
05:22
is about the same as from Monterey to these things.
05:25
Absolutely, exquisitely minute,
05:28
and yet we've discovered pretty much the full set.
05:31
So, one of my most illustrious forebears
05:35
at Manchester University, Ernest Rutherford,
05:38
discoverer of the atomic nucleus,
05:40
once said, "All science is either physics
05:42
or stamp collecting."
05:44
Now, I don't think he meant to insult
05:46
the rest of science,
05:49
although he was from New Zealand, so it's possible.
05:51
(Laughter)
05:54
But what he meant was that what we've done, really,
05:56
is stamp collect there.
05:58
OK, we've discovered the particles,
06:00
but unless you understand the underlying
06:02
reason for that pattern -- you know, why it's built the way it is --
06:04
really you've done stamp collecting. You haven't done science.
06:07
Fortunately, we have
06:10
probably one of the greatest scientific achievements of the twentieth century
06:12
that underpins that pattern.
06:15
It's the Newton's laws, if you want,
06:17
of particle physics.
06:19
It's called the standard model -- beautifully simple mathematical equation.
06:21
You could stick it on the front of a T-shirt,
06:24
which is always the sign of elegance.
06:26
This is it.
06:29
(Laughter)
06:31
I've been a little disingenuous, because I've expanded it out
06:33
in all its gory detail.
06:35
This equation, though, allows you to calculate everything --
06:37
other than gravity -- that happens in the universe.
06:39
So, you want to know why the sky is blue, why atomic nuclei stick together --
06:42
in principle, you've got a big enough computer --
06:45
why DNA is the shape it is.
06:47
In principle, you should be able to calculate it from that equation.
06:49
But there's a problem.
06:52
Can anyone see what it is?
06:55
A bottle of champagne for anyone that tells me.
06:59
I'll make it easier, actually, by blowing one of the lines up.
07:02
Basically, each of these terms
07:05
refers to some of the particles.
07:07
So those Ws there refer to the Ws, and how they stick together.
07:09
These carriers of the weak force, the Zs, the same.
07:12
But there's an extra symbol in this equation: H.
07:15
Right, H.
07:17
H stands for Higgs particle.
07:19
Higgs particles have not been discovered.
07:21
But they're necessary: they're necessary
07:24
to make that mathematics work.
07:26
So all the exquisitely detailed calculations we can do
07:28
with that wonderful equation
07:30
wouldn't be possible without an extra bit.
07:32
So it's a prediction:
07:34
a prediction of a new particle.
07:36
What does it do?
07:38
Well, we had a long time to come up with good analogies.
07:40
And back in the 1980s, when we wanted the money
07:42
for the LHC from the U.K. government,
07:45
Margaret Thatcher, at the time, said,
07:47
"If you guys can explain, in language
07:49
a politician can understand,
07:51
what the hell it is that you're doing, you can have the money.
07:53
I want to know what this Higgs particle does."
07:56
And we came up with this analogy, and it seemed to work.
07:58
Well, what the Higgs does is, it gives mass to the fundamental particles.
08:00
And the picture is that the whole universe --
08:03
and that doesn't mean just space, it means me as well, and inside you --
08:05
the whole universe is full of something called a Higgs field.
08:08
Higgs particles, if you will.
08:11
The analogy is that these people in a room
08:13
are the Higgs particles.
08:15
Now when a particle moves through the universe,
08:17
it can interact with these Higgs particles.
08:19
But imagine someone who's not very popular moves through the room.
08:22
Then everyone ignores them. They can just pass through the room very quickly,
08:25
essentially at the speed of light. They're massless.
08:28
And imagine someone incredibly important
08:31
and popular and intelligent
08:33
walks into the room.
08:35
They're surrounded by people, and their passage through the room is impeded.
08:38
It's almost like they get heavy. They get massive.
08:41
And that's exactly the way the Higgs mechanism works.
08:44
The picture is that the electrons and the quarks
08:47
in your body and in the universe that we see around us
08:49
are heavy, in a sense, and massive,
08:52
because they're surrounded by Higgs particles.
08:54
They're interacting with the Higgs field.
08:56
If that picture's true,
08:59
then we have to discover those Higgs particles at the LHC.
09:01
If it's not true -- because it's quite a convoluted mechanism,
09:05
although it's the simplest we've been able to think of --
09:07
then whatever does the job of the Higgs particles
09:10
we know have to turn up
09:12
at the LHC.
09:14
So, that's one of the prime reasons we built this giant machine.
09:16
I'm glad you recognize Margaret Thatcher.
09:19
Actually, I thought about making it more culturally relevant, but --
09:21
(Laughter)
09:24
anyway.
09:27
So that's one thing.
09:29
That's essentially a guarantee of what the LHC will find.
09:31
There are many other things. You've heard
09:34
many of the big problems in particle physics.
09:36
One of them you heard about: dark matter, dark energy.
09:38
There's another issue,
09:41
which is that the forces in nature -- it's quite beautiful, actually --
09:43
seem, as you go back in time,
09:45
they seem to change in strength.
09:47
Well, they do change in strength.
09:49
So, the electromagnetic force, the force that holds us together,
09:51
gets stronger as you go to higher temperatures.
09:54
The strong force, the strong nuclear force, which sticks nuclei together,
09:57
gets weaker. And what you see is the standard model --
10:00
you can calculate how these change -- is the forces,
10:03
the three forces, other than gravity,
10:05
almost seem to come together at one point.
10:07
It's almost as if there was one beautiful
10:09
kind of super-force, back at the beginning of time.
10:11
But they just miss.
10:14
Now there's a theory called super-symmetry,
10:16
which doubles the number of particles in the standard model,
10:18
which, at first sight, doesn't sound like a simplification.
10:21
But actually, with this theory,
10:23
we find that the forces of nature
10:25
do seem to unify together, back at the Big Bang --
10:27
absolutely beautiful prophecy. The model wasn't built to do that,
10:30
but it seems to do it.
10:33
Also, those super-symmetric particles
10:35
are very strong candidates for the dark matter.
10:37
So a very compelling theory
10:39
that's really mainstream physics.
10:41
And if I was to put money on it, I would put money on --
10:43
in a very unscientific way -- that
10:45
that these things would also crop up at the LHC.
10:47
Many other things that the LHC could discover.
10:50
But in the last few minutes, I just want to give you
10:53
a different perspective
10:56
of what I think -- what particle physics
10:58
really means to me -- particle physics and cosmology.
11:00
And that's that I think it's given us a wonderful
11:03
narrative -- almost a creation story,
11:06
if you'd like -- about the universe,
11:09
from modern science over the last few decades.
11:11
And I'd say that it deserves,
11:14
in the spirit of Wade Davis' talk,
11:16
to be at least put up there with these wonderful creation stories
11:18
of the peoples of the high Andes and the frozen north.
11:21
This is a creation story, I think, equally as wonderful.
11:25
The story goes like this: we know that
11:29
the universe began 13.7 billion years ago,
11:31
in an immensely hot, dense state,
11:34
much smaller than a single atom.
11:37
It began to expand about
11:39
a million, billion, billion, billion billionth
11:41
of a second -- I think I got that right -- after the Big Bang.
11:44
Gravity separated away from the other forces.
11:48
The universe then underwent
11:50
an exponential expansion called inflation.
11:52
In about the first billionth of a second or so,
11:55
the Higgs field kicked in, and the quarks
11:57
and the gluons and the electrons
11:59
that make us up got mass.
12:02
The universe continued to expand and cool.
12:04
After about a few minutes,
12:07
there was hydrogen and helium in the universe. That's all.
12:09
The universe was about 75 percent hydrogen,
12:12
25 percent helium. It still is today.
12:15
It continued to expand
12:18
about 300 million years.
12:20
Then light began to travel through the universe.
12:22
It was big enough to be transparent to light,
12:24
and that's what we see in the cosmic microwave background
12:26
that George Smoot described
12:28
as looking at the face of God.
12:30
After about 400 million years, the first stars formed,
12:32
and that hydrogen, that helium, then began to cook
12:35
into the heavier elements.
12:37
So the elements of life --
12:39
carbon, and oxygen and iron,
12:41
all the elements that we need to make us up --
12:43
were cooked in those first generations of stars,
12:45
which then ran out of fuel, exploded,
12:48
threw those elements back into the universe.
12:50
They then re-collapsed into another generation
12:53
of stars and planets.
12:55
And on some of those planets, the oxygen, which had been created
12:58
in that first generation of stars, could fuse with hydrogen
13:01
to form water, liquid water on the surface.
13:04
On at least one, and maybe only one of those planets,
13:07
primitive life evolved,
13:10
which evolved over millions of years into
13:13
things that walked upright and left footprints
13:15
about three and a half million years ago in the mud flats of Tanzania,
13:17
and eventually
13:20
left a footprint on another world.
13:22
And built this civilization,
13:24
this wonderful picture,
13:26
that turned the darkness into light,
13:28
and you can see the civilization from space.
13:31
As one of my great heroes, Carl Sagan, said,
13:33
these are the things -- and actually, not only these,
13:36
but I was looking around -- these are the things,
13:38
like Saturn V rockets, and Sputnik,
13:40
and DNA, and literature and science --
13:43
these are the things that hydrogen atoms do
13:45
when given 13.7 billion years.
13:47
Absolutely remarkable.
13:51
And, the laws of physics. Right?
13:53
So, the right laws of physics --
13:55
they're beautifully balanced.
13:57
If the weak force had been a little bit different,
13:59
then carbon and oxygen wouldn't be stable
14:01
inside the hearts of stars,
14:03
and there would be none of that in the universe.
14:05
And I think that's
14:08
a wonderful and significant story.
14:10
50 years ago, I couldn't have told that story,
14:12
because we didn't know it.
14:14
It makes me really feel that
14:16
that civilization --
14:18
which, as I say, if you believe
14:20
the scientific creation story,
14:22
has emerged purely as a result of the laws of physics,
14:24
and a few hydrogen atoms --
14:27
then I think, to me anyway,
14:29
it makes me feel incredibly valuable.
14:32
So that's the LHC.
14:34
The LHC is certainly, when it turns on in summer,
14:36
going to write the next chapter of that book.
14:39
And I'm certainly looking forward with
14:42
immense excitement to it being turned on.
14:44
Thanks.
14:46
(Applause)
14:48

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Brian Cox - Physicist
Physicist Brian Cox has two jobs: working with the Large Hadron Collider at CERN, and explaining big science to the general public. He's a professor at the University of Manchester.

Why you should listen

Based at the University of Manchester, Brian Cox works at CERN in Geneva on the ATLAS experiment, studying the forward proton detectors for the Large Hadron Collider there. He's a professor at the University of Manchester, working in the High Energy Physics group, and is a research fellow of the Royal Society.

He's also become a vital voice in the UK media for explaining physics to the public. With his rockstar hair and accessible charm, he's the go-to physicist for explaining heady concepts on British TV and radio. (If you're in the UK, watch him on The Big Bang Machine.) He was the science advisor for the 2007 film Sunshine. He answers science questions every Friday on BBC6 radio's Breakfast Show.

The original video is available on TED.com
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