The Big Bang Machine

13.7 billion years after it all began,

we're about to go back to the beginning of time.

'With the largest and most complex scientific experiment ever attempted.

'The Large Hadron Collider, or LHC,

'has just one simple but audacious aim -

'to recreate the conditions of the Big Bang...

'..in an attempt to answer the most profound questions about our universe.'

The goal of particle physics is to understand the universe in which we live.

We want to know why things are the way they are, how they work, what everything is...

we want to understand.

If you're going to go for the big questions then you have to go for it.

There is no point in sort of messing around if you really want to understand how the universe ticks.

The LHC is what you need.

When the switch is thrown, this could be either the beginning of the end,

when we find that our theories of what existed just after the Big Bang are right,

or it could be the end of the beginning where we discover that the universe is more mysterious

and more beautiful than we could possibly have imagined.

The Large Hadron Collider spans the French/Swiss border just outside Geneva.

It's the largest particle accelerator ever constructed.

I'm Brian Cox and I've been helping build it,

along with thousands of other scientists at CERN, the European Organisation for Nuclear Research.

This is the experiment, if you like, Q1, Q2, Q3.

One of the scientists overseeing the launch

of the biggest experiment since NASA sent men to the moon is Paul Collier.

It's going to be a like a moon shot where you see CAPCOM - "Go, go!"

-There's going to be a bank of experts saying, "Mind it's all right."

-Probably yes.

You must get asked this all the time. Is there a button? Who's going to press it?

There is not at the moment a button, but I'm considering buying one,

but the LHC is not like... it's not like a rocket.

There will not be a countdown, there will not be a button to press.

Unfortunately, the buttons we have are all computer sequences

which we have to go through to prepare the machine.

In a few days, it'll be standing room only

as the world's most eminent particle physicists

gather to watch this remarkable machine spring to life.

What's the scene going to be like on the day that the first beam goes around LHC?

What's it going to feel like in this control room?

Yeah, it's going to be an interesting time and quite exciting.

The first thing I should say is there will be two people on duty here,

one physicist and one technical engineer,

so, if you like, two people will be doing the work, and then probably 200 people will be watching them work.

And of course we will have to... we will have to keep control of that.

It's brilliant, actually, it's fascinating.

All of us who work at CERN hope that this will become the world's most renowned Big Bang laboratory.

That here we'll discover something so fundamental that it will change our understanding of the cosmos.

Because right now even the brightest minds and the best theories

all fall short of explaining what occurred as the universe burst into existence.

Physics is stuck and the only thing left to do is recreate the universe

as it was a fraction of a second after the Big Bang, and that's what the LHC's designed to do,

to smash bits of matter together at energies never before achieved

so we can stare at the face of creation.

Every civilisation has its own creation story.

The ancient Chinese, Indian mystics and Christian theologians

all place a divine creator at the heart of their creation stories.

Science too has an elaborate story that describes the universe's genesis.

It tells us how the fundamental constituents of the cosmos took on their form.

The difference with this story is that we can test it.

We can find out if it's true by tearing matter apart and looking at the pieces.

All you need is a machine powerful enough to restage the first moments after creation.

In the beginning there was nothing.

No space, no time, just endless nothing.

Then, 13.7 billion years ago, from nothing...

..came everything.

The universe exploded into existence.

From that fireball of energy emerged the simplest building blocks of matter.

Finding experimental evidence of these fundamental entities has become the holy grail of physics.

Well, the universe is an object that is not stable.

It is expanding and cooling, it's doing things.

It was therefore different in the past and will be in the future.

It has a history, it has a life, it has an evolution.

As the early universe grew, its mysterious primeval constituents

transformed themselves into atoms, then molecules and eventually stars and planets.

Now, billions of years on from the Big Bang, the universe is so complex

that all traces of the enigmatic building blocks are lost.

Understanding the evolution of the universe requires understanding what it is made of.

As it turns out, most of that of which the universe is made

are things that we do not understand at all.

But we hope that the LHC is about to bridge this profound gap in our knowledge

by peering further back in time than ever before.

The LHC is truly colossal.

Its accelerator ring is 27 kilometres long,

big enough to encircle a small city.

And around it we've built four enormous experiments

that will investigate the Big Bang in exquisite new detail.

This is my experiment, the experiment that I work on, Atlas,

and what you can see is just the surface buildings.

The experiment is actually 100 metres below the ground which is where the LHC is,

and basically this is just a building that covers cranes where we winch everything down.

And it's pretty much the last time

that not only TV crews, but me and the people who built it will be able to go down

because once it starts operating, the whole area becomes a radiation area, it becomes mildly radioactive.

You've always got to be worried when you see those things.

One of the most expensive bits of Atlas, if not the most, was digging the cavern.

We even have iris scanners, so a little bit of science fiction.

It's down here in caverns brimming with the latest technology that the Big Bangs will be made.

We just take little bits of matter, little bits of this stuff and accelerate them to as close

to the speed of light as we can get and then smash them together right in the middle of that detector

to recreate the conditions that were present back at the beginning of time.

The bits of matter we're going to fire around the LHC are called protons.

They come from a family of particles that give the collider its name, the Hadrons.

Protons are going to fly around here so close to the speed of light

that they go round this 27km tunnel 11,000 times a second.

The ring has two barrels that will shoot beams of protons around in opposite directions.

When they collide, they'll have the energy equivalent to an aircraft carrier steaming at 30 knots.

All this energy will be focused into a space just a fraction of the width of a human hair.

The resulting explosion will be so intense that no-one's quite sure what will happen.

This machine really is a leap into the unknown.

I mean it's often said with scientific experiments but I think in this case it's absolutely right.

We're, we're a step, something like a factor of ten in energy so it's a huge jump up in energy.

It's a huge jump up in the number of times we can smash particles together per second.

It collides protons together so often that your chances of seeing something incredibly interesting

and profound are increased way beyond anything that we've had before

and I can think of no better place to be actually at the moment.

This is exciting.

The dream of understanding the building blocks from which the universe is constructed

has inspired the greatest minds for over two millennia.

People have wanted to understand the universe and the stuff around them

ever since they began to think about it.

People have always been making theories about what matter is made of.

But the universe like everybody else is made of little pieces which

need to be understood in order to understand how the universe works.

The earliest reference to this concept of the world being made up

of tiny indivisible pieces dates back to ancient India in the sixth century BC.

Two centuries on, the ancient Greeks were the first to call these pieces, atoms, which means uncuttable.

But incredibly it was only in the early 20th century that the concept of the solid atom was shattered...

..and the modern version of atomic theory was born.

This new theory described the atom as being made up of a number of even smaller pieces.

Around the particles which form the nucleus of the atom,

other electrically charged particles called electrons constantly revolve like planets around the sun.

This new sub-atomic theory inspired the great experimental physicist

Ernest Rutherford to invent the art of particle colliding.

And ever since, we've peeled away the atomic layers.

Far from being uncuttable, the atom appeared to be more and more like a Russian doll.

Today particle physicists are busy dreaming up ever more elaborate ways

to torture matter.

It almost seems like a paradox that the smaller the thing you are looking for,

the bigger the instrument you need.

This is Fermilab and I used to work here for three years.

It's a beautiful piece of midwestern prairie.

The reason I worked here is because over there

is the biggest particle accelerator that's operating in the world today.

'I served my apprenticeship on a machine here called the Tevatron.'

Under that lake there, there's a tube that carries a beam of protons one way

and anti-matter protons the other way and we accelerate them round 50,000 times a second.

Imagine that!

It's as close to the speed of light as we can get and then we smash them together, two places actually,

that red building there, which is called CDF and that blue building over there which is called D zero.

And their job is to just simply take a picture of those collisions.

Fermilab has been colliding particles for over 40 years.

Probing the atom's secrets.

Leading the way into this sub-atomic frontier was the renowned particle hunter, Leon Lederman.

We didn't know anything about these particles.

We knew about atoms, but we had no idea of the complexity of matter.

What puzzled Lederman was that the more they looked inside the atom,

the more fundamental particles they found.

The moment of discovery is really a series of moments.

The experiment has worked.

We think it's OK, and then finally, "Hey, look at that, there's an event!"

Eventually get enough data to say we're beginning to see a class of particles...

that must have a very important role in the evolution of the universe.

Because of the work of Lederman and other pioneers, scores of particles completely new to science emerged.

The up quark, the down quark,

the electron, the electron neutrino,

the W-plus and the W-minus.

As scientists made their discoveries they began to name these fundamental particles.

The charm quark, the strange quark, the muon, the mu neutrino.

With these building blocks they came to a remarkable understanding of the world.

The top quark, the bottom quark,

the tao and the tao neutrino,

the Z particle and the photon.

Now they could explain what anything and everything is made of.

That's the Standard Model... Oh, no! The gluon, mustn't forget the gluon.

The Standard Model has gone on to become the basis for all modern particle physics.

So this was a model that was developed in the 1960s.

The first experimental breakthroughs

showing that it might be true came in the 1970s and I would say,

was really established by experiments at CERN in the 1980s and the 1990s.

Experimental science has shown that the nature of matter is more complex than anyone had foreseen.

Rather than a single atom, it turns out that nature uses 16 different fundamental particles

to make everything we see in the cosmos.

The Standard Model itself is a triumph. We have not only

the particles but the mathematics that gives a huge coherence

to our world on the microscopic level.

The Standard Model accurately describes the essential constituents of the universe.

It's no exaggeration to say it's one of the most successful theories in the history of science.

And yet many physicists feel uneasy about the Standard Model.

The maths is too complex, even ugly.

When scientists talk about beauty in a physical theory, they mean that

it can describe a whole range of diverse phenomena with hopefully simple concepts and simple maths.

Take Einstein's theory of general relativity,

our theory of gravitation, you can write it down in one line.

Now the trouble with the Standard Model is,

well, it takes pages to write down but also there are elements in it that are mysterious, arbitrary even.

There's something spooky about this Standard Model.

It doesn't really work, so we know that there is something sick in our theory.

For example, we have at the moment what we call a Standard Model of particle physics, works great.

Only one small problem, if you write down the equations of this model

it would seem to suggest that no particles would have any mass.

Clearly that's not true.

For all its power, the Standard Model overlooked

one of the most basic fundamental properties of our world.

It was incomplete in its description of the universe.

What's missing is an explanation, a mechanism for how the fundamental particles acquire mass.

Now we know intuitively that the things in the world around us have mass.

We can feel it.

It's... Well, it's what makes stuff, stuff.

But what is mass and why does it exist?

Sounds simple but it's become one of the most difficult and challenging problems in physics.

There must have been a time in the early universe

when the particles became substantial and took on their mass.

The best theory we have to explain how this happened was dreamt up one day

by a British physicist Peter Higgs, whilst walking in the Scottish Highlands.

He came up with a theoretical mechanism that could explain

how some but not all particles attain mass.

The Higgs mechanism works by filling the universe with a field, the Higgs field,

and by the universe I don't just mean up there amongst the stars.

I mean here in front of me, and inside of me, and particles

acquire mass by interacting with the Higgs Field, by talking to it.

The theory is that every particle in the universe is traversing this invisible Higgs Field

and some particles like the quarks and electrons acquire mass as they pass through.

Whereas mass-less particles, particles like photons,

don't interact with the Higgs Field and they just pass through the universe at the speed of light.

The Higgs brings simplicity and beauty to a nature which looks too complicated.

It introduces a kind of symmetry and a kind of beauty to nature which gives us an understanding of

one of the most puzzling features of this little model I told you about, the Standard Model.

The Higgs Field may solve the problem of missing mass in the Standard Model

but the only trouble is we haven't been able to detect it yet.

But there is hope, because it's a law of quantum physics

that all fields must have an associated particle.

And it's a key prediction of this Higgs theory that there should be a quantum of this field, a particle

associated with it and that's what's called the Higgs boson.

Is there a Higgs particle, and if there is, how does it appear?

How does it come about to simplify our view of the world?

It would be a tremendous discovery.

If we can find this new fundamental particle, the Higgs boson,

then we'll be one step closer to understanding how the universe came to be the way it is.

No wonder Lederman called it the God particle.

The Higgs mechanism is our best attempt to repair the Standard Model

but over 40 years after it was first thought of,

the Higgs particle, the one thing that could prove the theory correct hasn't been found.

EXPLOSION

So the only way to prove the theory correct is to try and create the Higgs boson

for an instant inside a particle collider.

Some thought that Fermilab with its powerful Tevatron collider would have found it.

Fermilab is working day and night, night and day with a machine

that's ever increasing the number of collisions

but I would say probabilistically we won't find it.

Ever since the Higgs particle was dreamt up and despite billions of dollars worth of research,

Fermilab has not seen even a hint that the God particle exists.

So the hunt for the Higgs boson is about to step up a gear at CERN...

..where Europe is about to overtake America in the high-energy particle-hunting race.

Building an instrument capable of recreating the early universe

and finding the massive Higgs boson has taken decades.

We've had to devise new ways of handling uniquely, not one,

but the two most powerful proton beams ever created.

There'll be a beam of protons going that way in that pipe at almost the speed of light,

another beam of protons going that way in that pipe,

at almost the speed of light and they'll cross inside Atlas and recreate the conditions

that were present just after the beginning of the universe.

Fantastic.

A ring of 9,500 super-conducting magnets has been designed

to safely contain and control the direction of the proton beams.

13,000 amps of current to the magnets,

1.9 Kelvin minus 271 degrees, colder than the space between the galaxies to cool the magnets down

and then the two beam pipes, one there and one there.

All joined up, these magnets make a collider four times longer than Fermilab's Tethertron.

To put the scale of the experiment in context, each circuit the protons make

is the same distance as the half-way mark from England to France along the Channel Tunnel

and they'll do this 11,000 times a second.

To understand how we hope to transform two tiny protons

into a massive Higgs boson requires the help of a genius.

Einstein's astonishing insight into the connection between matter

and energy is the engine which drives all particle physics.

His theory used just five characters

but with them he had shown us the way to a modern form of alchemy.

Einstein's famous equation, E = mc2,

that basically says that energy and mass are two sides of the same coin.

They're basically the same thing and they're interchangeable.

In this idea I think that Einstein was truly the first.

Mass is just a form of energy.

That was a very deep insight of Einstein.

There's absolutely no question. And there was no precedent for that idea.

One thing we take for granted as particle physicists is that we can convert energy into mass.

We do it all the time. That's how the LHC essentially works.

It speeds protons around faster and faster, gives them more and more energy

and then smashes them together, and the idea is to make new particles, like the Higgs boson, for example,

that's many, many tens or even hundreds of times heavier than the protons that collided to make it.

So Einstein's most famous equation is at the heart of the hunt for the Higgs particle.

In effect, the Large Hadron Collider is a relativity machine.

When the ultra high-speed protons smash into one another, they'll have phenomenal amounts of energy.

Each collision can produce hundreds of new particles.

For a moment, we've created a mini Big Bang.

It's in these "events", as they're known,

that we hope for a fleeting moment that the massive Higgs particle will be seen

for the first time in 13.7 billion years.

These will be the highest-energy collisions we've ever made.

It's led some to wonder if we know what we're doing.

One of the wildest speculations is that the LHC will be capable

of creating black holes that will devour the Earth.

I get page after page of e-mails saying,

"You maniac, you're going to destroy the planet!"

What do you say to these people? You must get the same e-mails.

I've seen that too. It's what everybody wants to know about

cos it's such a cool idea, right? Here we have LHC,

looking at the universe at the earliest time. What if it could make black holes?

Wow! Two interesting things happening at the same time.

But personally speaking I think it's incredibly unlikely.

I don't think there's any way they can be made.

Don't forget, people take this very seriously.

When there was this theory that came out that we could make black holes,

CERN took it so seriously that they made this special risk assessment, really just to make sure

that there wasn't going to be anything untoward happening. So no-one need worry.

I really think that there's absolutely no way we are going

to make anything like that. It's just too strange a theory.

Even if black holes do show up, they will not destroy the Earth.

'Much more likely is that the LHC will create Higgs particles

'and we've had to go to extraordinary lengths to be sure of detecting them.'

Not one, but four colossal particle detectors have been installed

around the ring to take pictures of what happens when protons collide.

Early particle detectors also took photographs of similar events.

It's these pictures that first captured

the fundamental particles in the Standard Model.

Here is evidence for a neutrino caught on film.

This was the first glimpse of the W boson at CERN in the 1980s.

And the Z boson's scientific debut.

But the one missing picture,

the one that would go on the wall if we find it, is the Higgs boson.

The reason it's been so elusive is to do with its mass.

Our theories predict that the Higgs particle is immensely heavy

and it's a general rule in particle physics

that heavy particles are unstable.

They simply fall apart into lighter particles.

So if the Higgs is a real part of nature,

it would have long ago vanished from the early universe.

And today, even if we manage to recreate the Higgs,

-it'll disappear...

-EXPLOSION

..before we can see it.

Instead, we'll be hunting for its decay artefacts,

other Standard Model particles like W and Z bosons, quarks and muons.

This is a simulation of a single proton/proton collision at the LHC.

It's actually the simulation of the production of a Higgs particle.

Now, the Higgs particle you don't see, of course.

It just decays in a fraction of a second.

But what you do see is the smoking gun,

in this case, two very clear red tracks,

these two particles here, called muons,

that have gone straight out to the very edges of the detector.

And if we see not just one collision like this, but maybe 10, maybe 100,

then we'll have discovered the Higgs and for the first time

we'll understand the origin of mass in the universe.

That is if the experiment works.

Switching on the planet's largest particle collider is an anxious time for everyone.

The sheer magnitude of this complex machine

and the power in the beam

is something that nobody's ever done in the world,

and we have to not forget anything important that we destroy something.

It takes months to cool each section of the LHC down

to its operating temperature of less than minus 271 degrees Celsius,

no mean feat since this is colder than deep space.

And if anything fails, it'll be a major setback in the search for the Higgs.

It would take us two, three months to repair that part of the machine, even though it's based on a sector basis,

and it takes enormous time to warm up the whole sector

of 3.3 kilometres, the cryogenic, so there is a lot of time issues involved.

Even one week is too long so certainly two, three months is very long.

People are waiting for beam, waiting for physics. We can't afford that.

So CERN's management decided last year to cancel

an engineering run scheduled to test the entire ring.

Instead of beginning slowly with some safe but dull low-energy collisions,

the machine's first run will accelerate particles

to high energies straight away.

If it works, this incredible machine, this vast effort

of thousands of scientists and billions of Euros

is certain to change our understanding of the universe.

If the Higgs exists, then it'll be created here

in the centre of Atlas over the next few years.

If we don't see it, then it wouldn't help to build a bigger machine and a bigger accelerator.

It really means that the God particle doesn't exist.

And for some theorists, finding nothing at the LHC

is actually the most exciting prospect.

It can be argued that the most interesting discovery at the LHC

would be that we cannot find the Higgs,

proving practically that it isn't there.

That would mean that we really haven't understood something,

very deeply not understood something. That's a very good scene for science.

Revolutions sometimes come from the fact that you hit a wall

and you realise that you truly haven't understood anything.

The theorists may long for a revolution but most of us

are pretty sure that the Higgs boson is a real part of nature.

What are the chances we're ever going to solve the mystery of mass?

For the first time in a generation

we stand at a crossroads in physics

and that's what makes this place so exciting,

because nobody knows what the next steps are in our quest

to understand the universe,

but I'm convinced that this place will show us the way

to new physics.

Even if the Higgs boson does turn up at the launch party,

work at the Big Bang machine won't stop.

Beyond the mystery of mass lies a much thornier challenge

for the Standard Model, a puzzle that defeated even Einstein.

Why does the world appear to obey different rules?

There's the world of the small, the quantum world,

that the Standard Model explains so well,

and then there's the world of the large,

the world of stars and planets and galaxies.

The Standard Model has nothing to say about how they interact.

And it's a problem we've yet to solve.

When you want to understand the way the universe has evolved -

so what happened to it straight after it began and how it got to how it is today -

you've not only got to know about how many galaxies there are,

the way that stars work and the way that planets form...

..you've also got to know what the fundamental building blocks

of all those things are and how they interact together.

And in particular it's not only the stuff that's in the universe,

but the way that stuff talks to other stuff. It's about the forces.

If these forces didn't act on matter, nothing would happen.

The stars wouldn't shine,

the atoms that make up the planetary bodies would fall apart.

The universe would disintegrate.

It's the forces in the Standard Model which hold everything together.

There are four forces that we know of in the universe at the moment,

the thing called the strong force which sticks nuclei together...

This strong force is what binds the quarks together

to form the nucleus at the heart of the atom.

There's electro-magnetism, that kind of quite familiar force to everyone.

This force holds the electrons in orbit around the atomic nucleus.

And a thing called the weak force which is quite unfamiliar

but it allows the sun to shine, so it's incredibly important.

The weak force explains why some atoms undergo radioactive decay,

the process which fuels every star in the universe.

But, crucially, one force is missing from the Standard Model.

Gravity.

In the everyday world you and I inhabit,

clearly gravity is all around us.

It's what keeps you in your chair at home,

it's what keeps Earth in orbit around the Sun

and it's what holds our galaxy together.

And Einstein too thought gravity was pretty important.

His General Theory of Relativity beautifully describes

how every celestial body interacts with every other body

through this force.

'The universe on the grand scale can be entirely explained

'by Einstein's equations.'

But there's a problem.

The moment we try to merge General Relativity with the Standard Model,

we encounter immense difficulties,

so immense, in fact, that nobody's been able to work out how to do it.

They're completely incompatible pictures of the universe.

The problem is they're pictures of the same universe.

Something has to be wrong.

The Standard Model is incredibly powerful at describing the world of the small, the quantum world.

But as soon as you try to add gravity into the Standard Model equations, they break.

Einstein was searching for just one set of equations

that would work on both planets and particles,

nothing less than a theory of everything.

This was Einstein's greatest failure.

At the smallest distance scales, his theory just falls apart.

Einstein spent the last 30 years of his life trying to rectify the problem

but he never succeeded.

'53 years after Einstein's death his theory of everything still eludes us.'

This is CERN's theory corridor.

Inside each room is a theoretical physicist.

And inside the head of each theoretical physicist

is a different conception of our universe.

'The first physicist to coin the term "a theory of everything"

'was CERN's John Ellis.'

When we talk about a theory of everything,

we mean a theory of the fundamental constituents

of matter and the forces between them.

You can somehow think of it as a sort of cosmic genetic code, right?

In fact, the Standard Model already you can regard

as being a sort of genetic code for making up the regular visible matter in the universe.

All the visible matter in the universe is made up out of the same quarks and electrons and things

that we can measure in the laboratory.

Somehow or other, these things can be combined in all sorts of ways

to make people as complicated and bizarre as you or me.

The search for this cosmic genetic code is the ultimate quest for physicists.

We want to finish what Einstein started.

You might wonder why we believe the baffling complexity of the universe

can ever be reduced to a single theory.

The answer can be found back at the Big Bang.

If we journey back through time, the universe shrinks,

galaxies disappear and the stars evaporate into gas.

As we draw to within a couple of hundred thousand years of the Big Bang, the universe becomes opaque.

Eventually we approach the moment when atoms vanish.

Now things get really strange.

Seconds away from the Big Bang, the atomic nuclei break apart.

The universe is now so small and so hot

that only the naked fundamental particles of the Standard Model exist.

This is the time of the Higgs.

It's at this time that the LHC will spend most of its working life.

This is what this machine was designed to do, to open a window onto the time

when the Higgs ruled the universe.

But some of us believe that it may give us a glimpse of something even more profound.

Beyond the Higgs, the universe continues to condense.

Eventually even the fundamental particles

of the Standard Model disappear.

We are approaching the moment of the Big Bang itself.

In the instant of creation there must have been a time

when the universe was nothing more than a single, unimaginably hot,

fantastically small entity,

the entire universe was made of just one thing,

pregnant with possibilities.

Remarkably, we have a highly speculative theory

that attempts to describe this era.

It's called String Theory.

The String Theory concept is that particles, the objects that exist,

are actually vibrations of a single string

and like, like the notes of a piano,

they vibrate once or twice or three times, and each note corresponds to a different particle.

So if everything was just a note that you could play on the piano,

a single piano, maybe a single string, that would be a very simple idea.

String theory is certainly the best candidate we have for a theory of everything which would combine

all the different forces, all the different particles and make a decent cup of coffee.

These peculiar strings, if they exist,

are our best attempt to understand what might underpin everything.

They're unimaginably small,

they were the first things in the universe,

and they have multiplied to create every particle we see today.

Incredibly, String Theory may succeed

where the Standard Model fails...

..because when gravity is added to the Standard Model,

the equations break down and produce infinities.

These horrendous infinite answers come about,

we think, because we're treating the particles as being tiny little points

and when you bring these tiny little points together

the gravitational force becomes incredibly strong

and we don't know how to handle that.

Gravity can become so strong because point light particles

can get infinitely close together...

..and that means that the gravitational force between them

becomes infinitely strong.

Supposing the particles, instead of being tiny little points,

were sort of warm, fuzzy, extended things, right?

Then you could bring them together and the gravitational force would not blow up in your face.

So maybe that's the answer, maybe particles are not actually points

but actually extended objects, maybe they're pieces of string.

Strange as it may seem, by imagining a universe made of string,

we have a way of creating the extra space that gravity needs to work.

The extraordinary thing about String Theory is that, for the first time

in the history of physics, it offers a bridge

between the two contradictory descriptions of the world we see today -

the Standard Model of particle physics and Einstein's General Theory of Relativity.

It's a contender for a theory of everything.

What would Einstein have thought of our current attempts to bring General Relativity into the fold?

What would he have thought of String Theory?

I think he would have been delighted for a while.

That is to say, he would have been fascinated by the beauty of the theory

till he realised that it didn't have any convincing predictions

that we could check now. He would be very unhappy about that.

Einstein would have spurned String Theory

because so far nobody has produced a single prediction that we can put to the test.

It remains an intriguing but unprovable concept.

This is science at its most esoteric.

It's like philosophy, religion even, because all it has going for it is beauty.

We have a mathematical description of the first few moments after creation but nothing more.

To see far enough back in time to discover a string would require a collider the size of our galaxy.

For now, the LHC is as large as it gets,

although perhaps instead of creating a string we can search for one of its most remarkable properties.

The original idea was that, OK if they're not points, maybe they extend out

along some sort of line, might be a curvy line, like a piece of string.

That's named the String Theory.

In fact, people realised that that's not enough.

If they're going to be extended in one dimension,

they're probably extended in two dimensions, maybe three dimensions, maybe more dimensions.

So in fact String Theory nowadays is a bit of a wrong name, right?

And in fact people nowadays often talk about something called M Theory,

which is supposed to contain this idea that particles are not just extended in one dimension

but maybe M for many dimensions.

Multiple dimensions are notoriously difficult to imagine,

let alone detect,

yet one of the wildest hopes is that we might just catch sight

of an extra dimension at the LHC.

Space has three dimensions,

we all know that. But we think that maybe each point of our space

is actually not a point but a sort of little sphere

with extra dimensions inside.

And if we could penetrate into these little spheres at the energies

that we are exploring, maybe we'll find these extra dimensions.

That idea of extra dimensions is very connected with String Theory.

If we do detect another dimension at the LHC,

then we'll be able to show that the universe is at least a place where strings might feel at home,

a universe in which gravity and the other forces can harmoniously co-exist in our mathematics.

We'll be one step closer to completing our story of creation.

This is maybe the most important thing about the LHC.

For a long time now, we've been speculating about String Theory,

about extra dimensions,

but we haven't had hard facts to confront them with.

Now, if we find extra dimensions at the LHC, that would be kind of a hint

that String Theory might be right, but it wouldn't be a proof.

It would be, if you like, a smoking gun for String Theory.

But it would encourage us to think that maybe we were on the right track.

It would be a tremendous breakthrough,

but with today's technology

finding another dimension

is highly unlikely.

The LHC will allow us to explore the earliest times in the universe.

Within a few years it will tell us whether the Higgs boson, the God particle, really exists.

And it may even tell us that there are extra dimensions in the universe.

This is exploration.

It's a journey to the very edge of our understanding.

Today is the moment.

We don't know what the LHC is going to discover.

We've got all these ideas. They can't all be right, a lot of them are going to be proved to be wrong.

But if just one of them gets proved to be right,

then it's going to be the most exciting event in my scientific lifetime.

And, for me, that's what science at the Large Hadron Collider is all about.

It represents the noblest side of humanity -

our need to know.

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