How Small is the Universe? Horizon

Astronomers have long tried to understand our place as tiny specs

in the vastness of the universe.

But there is another expanse of the universe to explore,

a bizarre realm in which we are giants,

the weird world of the very small.

This is a journey into the heart of matter,

a journey down the biggest rabbit hole in history...

It's perfectly possible that in the high-energy end of our data,

right now we are occasionally making miniature black holes.

..a journey smaller than you can see, smaller than an atom,

where nothing is what it seems...

The more fundamental things are,

the nicer it is to look inside them.

..into a wonderland which seems far removed from reality...

Gravity is leaking into the extra dimensions.

..down to the very smallest structure of the universe.

We should expect space time to be not smooth as we presently imagine,

but more like the foam of a cappuccino.

The journey to find the smallest thing

may take us into another universe altogether.

But then of course, when you're down to this scale,

you may have the whole universe in your hand.

And at the bottom of the rabbit hole,

we may find that our universe is just one of many.

On top of an extinct volcano in the Canary Islands

a strange telescope called MAGIC stands guard.

It's on a ten-second stand-by

to respond to the most violent explosions in the cosmos.

With its laser-aligned panels, it is detecting the fallout

from cosmic rays that have travelled half way across the universe.

And it's helping physicists answer an eternal question.

Well, at the end of the day, the question comes up, why do we exist,

and not only we as mankind, but why does this planet exist,

the solar system, the universe?

If you want to know why the universe exists, you need to look,

not to the very big, but to the very small.

And it turns out there need to be a very small number of parameters

very finely adjusted for the universe to be as it is

and for us to sit in this universe, to be able to observe it.

So I think this tells why it's important to understand

how the laws of nature work.

And the strangest thing about MAGIC,

is that it's not really a telescope at all.

It's the eyepiece of the biggest microscope in the world.

It's just one of the incredible tools scientists have developed

in their ongoing search for the smallest thing in the universe.

Look at that!

The nucleus and the electrons going around the atom.

The exploration of the most distant,

unreachable territory in our universe is challenging

the minds of our greatest scientists.

-Very nice.

-This is very complex, very complicated.

Am I getting there? Aargh!

As you look smaller and smaller,

no-one knows if there will ever be an end.

Well, with me you'll see the more determination to find the next layer.

I'm going to need a bigger collider soon.

So we split, even split the nucleus.

The hunt for the smallest thing in the universe

is challenging our understanding

of the very nature of space and time.

Yes. This is it. This is the smallest piece.

That is the smallest thing, isn't it?

Nice analogy!

The search for the smallest building blocks of the universe

is one of the oldest in science.

For almost 1,000 years, this medieval cathedral has looked over

the streets of Aachen in Germany,

an enduring monument of stone and glass.

But if you look really, really closely,

all is not what it seems.

Professor Joachim Mayer is a man with a unique view on the world.

He sees the bizarre changes that come about

when you view the world in terms

of the building blocks of stuff -

atoms.

Where you or I might see red, he sees gold.

There are always two parts of your brain.

If you look, if you come in as a human being

but as a scientist as well,

you are stunned by what people have built in these medieval times.

And then you ask yourself what kind of materials did they use?

If you look for example at these glass windows, it's very well known

that actually nanotechnology is used in some of the colours, for example

gold nanoparticles actually, produce the most durable red colour

which can be produced. And it's still a miracle to us

how in these ancient times, you know, the people found out

that this is the most efficient way to produce a red colour.

The red is just an illusion caused by the massive difference in scale

between the tiny clumps of gold atoms and us -

the giants who see red.

It's one of the reasons

scientists are obsessed with reaching the smallest scales.

Things don't just get smaller, they change.

Scientists have thought for a long time

what are the smallest building blocks of our matter,

and you can see beautiful matter around us.

But just how small are these building blocks?

If we start on the familiar scale of a human

and zoom in ten times closer,

we get to the size of a face.

Magnify by ten once more, and we are looking at the iris of an eye.

100 times closer and we can see a human hair,

magnified 10,000 times.

Microscopes have unveiled a world

smaller than the wavelength of light.

But the ability to see individual atoms has, until recently,

been a dream.

As microscopes have got bigger and more powerful,

they have allowed us to peer ever smaller.

It was the ancient Greeks who first dreamed up the idea of atoms.

100 years ago, scientists proved they exist.

But it's only in the last ten years

that we've actually been able to see them.

And now, behind these doors,

Joachim Mayer has a machine that gives us the best possible view.

MUSIC: "Also Sprach Zarathustra" by Richard Strauss

It looks like a giant coffee maker!

So this is our new PICO instrument,

which has been installed about a year ago.

And with its special new corrector for the chromatic aberration,

is really a very unique machine which really offers us new possibilities.

I think with its new capabilities, we consider it

as the best electron microscope in the world.

Being the best electron microscope in the world,

PICO is very sensitive to its surroundings.

Even a person's body heat would disturb it,

so PICO has to be operated remotely.

And, safely isolated from humans,

PICO is able to unveil the secret world of the very small.

We start our investigations at a very small magnification,

which is equivalent to the highest magnification, which you can actually reach

with a light microscope. At this magnification,

the diameter of a human hair would be about that size.

And now we can in magnification

go at least a factor of 1,000 higher.

And now we start to see the structure,

actually these black dots are individual gold nanoparticles.

And now you can see the individual atoms

as they appear in this individual nanoparticle.

So we see individual atoms aligned in the structure.

It's hard to imagine just how small these dots of matter really are.

But consider that each of us contains

about seven billion, billion, billion atoms.

That's more than the number of stars in the entire universe.

PICO is, quite simply, the most powerful microscope in the world.

After magnifying things a billion times, we can actually see

the individual atoms that make up everything in the universe.

This is the smallest thing we can see.

It may well be the smallest thing we'll ever be able to see.

These atoms look reassuringly like what you'd expect -

solid round balls of stuff.

But this is merely an illusion.

If you want to find out what an atom really looks like,

you need a whole new way of looking.

Professor Andy Parker is trying to find things

smaller than anyone has ever found.

Well, the way to look inside an atom

is to fire something at it very fast,

and if you hit it hard enough it you can break it into little bits.

He's using the most expensive experiment

in the history of physics,

one he helped design.

At 17 miles long, and buried 100 metres underground,

it is the biggest, and most famous particle accelerator in the world -

the Large Hadron Collider.

The ring goes right over behind the apartment blocks there,

and then it goes five miles in that direction,

roughly to the horizon,

it comes round under the base of the mountains to here,

and it sweeps back round,

past those buildings there and back to point one.

But once you start looking inside an atom, nothing is what it seems.

People always imagine atoms as billiard balls,

they've seen pictures of atoms as billiard balls

or with a little electron going round quite a big nucleus,

and this is a completely false picture.

If you blew up an atom to the size of the Large Hadron Collider,

so it would be five miles in that direction...

..all around there on that piece of landscape...

..then the nucleus would be about ten centimetres across,

about the size of this tennis ball.

So all the mass, all the weight of the atom

is condensed into this tiny little nucleus,

and the whole space around it is empty, apart from these few electrons buzzing around.

The illusion of solidity

comes from the fuzzy cloud of charged electrons.

But on their own,

they weigh virtually nothing and occupy no space.

You need to go a 100,000 times smaller

to get to the nucleus - a fizzing ball of protons and neutrons.

The challenge here at the LHC,

is to look inside the protons by smashing them to pieces.

It's brute force and ignorance really.

You are taking two things, which are very, very small,

you don't really know what's inside them to start with,

and you hit them together as hard as you can

and they smash into tiny fragments and since you really don't know

what the elaborate structure is inside, it's kind of like

colliding two clocks together and then sweeping up the mess

that you get and trying to figure out how the clock works.

And you can't do it in a subtle way.

There's no screwdriver to take a proton to bits

and there's no plan of what's inside

so you have to hit them very hard, then the fragments come flying out

and from that we can try and work out,

how all the cogs and gearwheels fit back together to make a proton.

The debris from the proton collisions

is detected by a vast machine called ATLAS.

Everything interesting happens at the centre,

that's where the particles collide.

This engineering mock-up shows just one section of the real machine.

And the sensitive instrument at its very heart is the part made by Andy.

So I'm in the middle of the mock-up of ATLAS,

and this is where all the action happens.

The beams would come in from both ends through the centre here.

This would of course be filled with detectors, but the beam pipe

would run right through the centre and the particles, which are

travelling in vacuum at almost the speed of light, collide head on

just here, and do their stuff and then all the debris comes flying out

and it flies through the detector layers...

..and that's the debris that we use to reconstruct the collision

that happens right here in the middle.

And what you find when you smash a proton to pieces,

is that it too is largely empty space.

It is made of three tiny fundamental particles called quarks.

But to reach the size of a quark we have to zoom in

1,000 times smaller.

Some of the earliest machines used to probe the atom

were bubble chambers, that produced exquisite pictures

of the heart of matter.

What you see here is a sudden explosion of particles from nowhere

in the liquid of the bubble chamber and that is because

a neutrino has hit an atomic nucleus there and smashed it to pieces,

and we see the particles flying off.

And that's anti-matter.

That's matter and anti-matter being created from pure energy.

Very, very beautiful image.

So this is the map or a part of the map, of what nature can do.

So it's part of the map of the universe.

But now, after 80 years of smashing, the map is complete.

In the summer of 2012 scientists at the LHC,

announced the discovery of the famous Higgs particle.

It's the final piece of what's called the Standard Model -

a set of 17 fundamental particles

including quarks and electrons

that make up everything we know.

But for physicists like Andy

it's not the end of the story.

Everyone's heard about the Higgs

but the story goes much beyond that.

In fact my main interest is beyond the Higgs.

Like any great explorer, Andy is not satisfied

that this is the end of the journey.

There may be plenty more to discover.

OK so we're in the ATLAS main control room,

where the experiment crew, shift crew here are sitting taking data today.

This is live data coming from the detector -

collisions that are happening now.

Collisions are happening 40 million times every second.

And as the energy of the collisions increases,

Andy will be able to look on smaller and smaller scales,

even delving inside the so-called fundamental particles.

Fundamental particles is a myth, I think.

It looks at the moment

as if quarks and electrons are point-like particles.

We can't see any size to them but that is just because

we haven't been able to measure very short distances around them.

What I'd like to see is what's going on inside them.

So we're looking for the innards of the quarks

by smashing them together as hard as we can.

In the search for the smallest piece of the universe,

part of the problem may be knowing when to stop.

Each new layer reveals great secrets.

But does this search have an end?

Or within every small thing,

is there another...

..and another?

Perhaps the best known of all the fundamental particles

is the electron.

It underpins much of our modern lives,

from computers to street lights to televisions.

But for theoretical physicist professor Jeroen van den Brink,

the electron might not be as fundamental as we think.

The more fundamental things are,

the nicer it is to look inside them.

Physics it's always that something appears to be fundamental,

and just because we believe it's fundamental we take the next step

and try to look what's inside it.

Jeroen's idea was that, rather than smashing electrons into pieces,

he could find a different way to split its properties...

the very properties that make it so useful.

So the electron has three fundamental properties,

charge, spin and orbital and theoretically

it's definitely possible to split those three parts of the electron.

If you do the mathematics

there is no problem in doing that.

If you do the quantum mechanics, it's completely allowed.

So in principle you can split the electron,

at least you can do it on paper.

If you want to want to do it in practice, you need this...

Watch your head here.

..the Swiss Light Source,

a million watt light bulb.

This is an in vacuum undulator.

The Swiss Light Source is in fact the Swiss X-ray Source.

We have digital BPM systems.

Inside the ring, under the care of Dr Andreas Ludeke,

a beam of electrons creates the ultimate X-ray laser.

This is a superconducting cavity.

It's one of the most powerful, highly focused, narrow X-ray beams

in the world.

We have a high intense magnetic field in the middle.

The perfect tool for probing down to the size of an electron.

Jeroen's partner in electron splitting,

the man who devised and runs the experiment,

is Dr Thorsten Schmitt.

So here we are in the so-called optical hutch,

where all the crucial optical elements -

mirrors which are optimized for X-rays and which are used

for shaping the beam quality are sitting.

-I can see it here.

-Yeah.

So when I come here I go to the equipment, I look at it,

I admire it and then I go back and sit behind a computer

or take my pen and paper and start to do the mathematics.

I do not really understand what the stuff out here is exactly doing

and I believe, I'm sure Thorsten does and they do the experiments.

We have X-rays, which are coming in and hit a sample,

and we will then in the end analyse the X-rays, which are re-emitted

or scattered off from the sample.

When the X-ray beam strikes,

the electrons split into new quasi-particles.

These particles, called spinons, orbitons and holons,

carry the properties of the electron,

and can travel off in different directions.

This is actually the picture that tells the whole story.

The most important part is here, this red part,

and what's important is that it's wavy.

And this waviness tells us that what happened in this experiment

is that the electron was split into spinons and orbitons.

So this is the picture

that is the experimental proof that the electron has been split.

Are you proud of that picture?

I'm very proud of the picture.

So the electron can be split into these three different particles,

but, really, what can you do with those particles when you have them?

I don't have a good answer to that.

It's just cool to make these, make this electron that is so

fundamental, that's so part... That's the first fundamental particle

that was discovered, to see it split into its three different parts.

That's what I like about the experiment.

The electron has, in one sense, been split in three.

But it's a measure of just how weird things are down here

that it's still considered to be fundamental.

Down at this scale,

we just have to accept that the rules become deeply strange.

And if we reach down even further,

we may have to throw out the rule book altogether.

Back at the LHC, far beyond the Higgs,

smaller than the innards of a quark, Andy Parker believes ATLAS

could reveal something that, at this tiny scale, shouldn't really exist.

So this great big building here is at the top of the ATLAS pit.

100 metres straight down is the detector,

which is operating at the moment,

so we're not allowed in the building for safety reasons.

He is hoping to make one of the most fearsome objects in the universe -

a black hole...

Si je produis des problemes pour Atlas, je suis "eeeek"!

..a place where gravity is so vastly strong that nothing -

not even light - can escape.

Problem is, if they open it, that could set off the pit alarms.

It takes the entire mass of an imploding star,

condensed into the space of a small town,

to create the extreme gravitational pull of a black hole.

They are normally vast, and live at the centre of galaxies.

And yet Andy Parker is trying conjure a micro black hole

right here at CERN, using just a couple of protons.

It's perfectly possible that in the high-energy end of our data

right now we are occasionally making miniature black holes.

The protons are colliding below us, they come together,

they have a lot of energy in them. And gravity cares about energy.

It's the same as mass as far as gravity is concerned.

So if you put a lot of energy in a small space,

as we're doing right now,

then you could potentially form a quantum-sized black hole.

A very, very tiny black hole.

It wouldn't be stable, it wouldn't last a long time

and eat the planet, it would disappear in a puff of radiation,

and we would see that puff of radiation in our detector.

The only way it would be possible to make these micro black holes,

at least 20,000 times smaller than a proton,

is if, on the level of the really, really small, we discover

that gravity is vastly stronger than it seems in everyday life.

And that would change our view of the familiar world,

and challenge something we all take for granted -

that we live in a world of three-dimensional space.

So this seems to be a perfectly ordinary three-dimensional world.

There are three ways I can go.

I can go forwards and backwards, side to side, up and down.

There can't be anything much more than that, can there?

So if I want to go up the tower, for example, over there,

I go sideways, I go forwards and I go up.

Seems to be the only possibilities.

But not necessarily.

If we could conjure up an extra dimension,

it could explain how you get super gravity at the tiny scale.

Because, although gravity seems strong in our everyday lives,

it's actually pretty feeble.

Gravity is a puzzle.

It's very, very much weaker than the other forces -

actually a million, million, million times weaker than the other forces.

It feels strong to us - right here,

I'm feeling uncomfortable about gravity pulling me over the edge.

But that's because there's a whole planet there pulling me downwards.

The other forces that are hard at work holding the world together,

including the electromagnetic force,

are all vastly stronger than gravity.

So here's a little magnet.

And this key, being held down

by all the atoms in the entire planet pulling towards the centre.

And this feeble little magnet can overcome

the gravity of the whole planet quite easily.

Now, why is gravity so weak?

Well, one possible explanation is that it's not actually weak.

It's just as strong as the other forces,

but we're missing part of it,

and gravity is leaking into the extra dimensions,

and so when we calculate the strength of gravity,

we're only seeing the piece that's in 3D.

Most of our gravity could be leaking off into the fourth dimension.

All we get is the leftovers.

This would account for the feebleness of gravity,

but where could this fourth dimension be hiding?

Well, if there is an extra dimension, it's everywhere.

The question is, why can't we see it?

All the others we can go off to infinity along these directions

but maybe the reason we can't see the fourth dimension is that

it's actually curled up.

If you went into it, you'd go round in a little circle

and come back on yourself, just like if you travelled on the surface

of the Earth far enough, you'd come back to where you started.

But this would be on a very, very small scale.

Hiding an extra dimension may sound tricky,

but it's all a matter of scale.

It's a very strange concept,

but you can see it for people who live in a flat world.

If we look down on the people down below, then they're

moving around on a surface, which is pretty much flat, and looked at

from this large distance up, it just looks completely flat

and they move about, they cannot go up and down because they can't fly.

From a great height, the tiny people seem to live in two dimensions.

But if we zoom into the same scale as the ant people,

you realise they can actually move up and down as well.

Similarly, if we could get down to a small enough scale,

we might find there is a fourth dimension curled up.

It may sound an outlandish theory,

but if Andy spots his baby black holes, all this would be true.

If we did see evidence of black holes at the LHC, that would be

absolutely amazing because it tells us that everything we think

we know about gravity, general relativity and so on, isn't right.

Then you would have demonstrated that the world is not

three-dimensional, but four-dimensional or more.

And you would have made a black hole in the lab.

So you get the Nobel Prize for making a black hole in the lab,

you get the Nobel Prize for proving general relativity wrong,

and you get the Nobel Prize

for demonstrating that the universe is multi-dimensional.

I mean, how cool is that?

On our journey to find the smallest thing in the universe,

things have indeed become deeply strange.

We have dived down a rabbit hole into a bizarre wonderland

where extra dimensions may lie curled and hidden from our view.

But that's just the beginning of the weirdness.

As we look even smaller, beyond even the reach

of the Large Hadron Collider, we have to rely on theory alone.

Professor Michael Green is a founding father

of one of the strangest theories in physics.

A theory that tells us that the universe is made of strings.

String theory starts off simply enough,

but it leads to some mind-boggling conclusions.

The fundamental particles, instead of being point-like objects

are now thought of as being string-like objects.

Instead of the 17 particles in the standard model,

everything is made from a single object -

an incredibly tiny loop of string.

The characteristic feature of a string, which makes it

different from a point is that it can vibrate

and the different modes of vibration, the different notes, if you like,

are seen as different kinds of particles.

So there's this very appealing,

almost poetic way in which string theory describes all the particles

in terms of different notes on a string.

It's like the music of the spheres almost.

It's a beautifully neat idea.

Each note from the vibrating string produces a different particle.

There are, however, one or two problems.

These strings are so small

that no-one has ever seen anything remotely stringy.

Depending on one's viewpoint, the size of these strings

can vary an awful lot,

from scales, which are sort of

a millionth of a millionth of the size of a nucleus,

to scales, which are much, much smaller than that.

If string theory turned out to be true,

then a string would be the smallest thing in the universe.

The trouble is, once we get this small, the whole notion of small

and big may get turned completely upside down.

Supposing these are quarks and electrons, photons, the particles

that constitute the standard model. Now we've got a problem because

if you believe that they're made of something smaller, that's fine.

You'll find something smaller inside.

But if you believe in a theory like string theory,

then the notion of smallness no longer means the same.

Ah, I haven't actually reached it. It's even smaller than that.

And there's an even smaller one than that.

I have a little speck here, so that must be the smallest thing.

But then of course when you're down to this scale,

you may have the whole universe in your hand,

because the, the universe itself started

from something this scale and expanded into everything we know.

So this thing, which you think is the smallest constituent,

may in fact be the thing that contains all of us.

So the notion, the difference between...

Oops, I hadn't even got there.

I dropped it, I dropped the little universe.

The notion that this is the smallest constituent is paradoxically

not at odds with the statement that it may also be the whole universe.

String theory is underpinned by some fiendishly complex maths.

But to make it work out,

the theory invokes not just one new dimension,

but says that we live in 11 dimensional hyperspace.

If you could describe exactly how these extra dimensions

are curled up, you'd be able to describe the exact nature

of everything in the universe.

The trouble is, there's more than one way to curl them up.

So the equations of string theory

have very large numbers of solutions, a humungously large number,

any one of which might describe a possible universe

with its own laws of physics,

its own kinds of particles and its own kinds of forces.

This whole body of solutions of string theory has been called

the landscape string theory.

Each peak in the landscape represents a different solution -

a different possible universe.

With each one just as likely to exist as the next.

Most of these solutions would describe universes

which are completely absurd.

The typical ones would be the ones, which came into being and either

ceased to exist after a very, very short time or exploded in such a way

that matter exploded apart and never formed galaxies in the first place.

The fact that our universe has existed for long enough

for galaxies to form and evolve and planets to form and for life to form

and us to exist tells us that we are living in a very untypical universe.

If they could find the right solution - the right one

out of 1 followed by 500 zeros,

we'd have a neat explanation for everything in our universe.

So the fascinating thing is the multiverse idea

has been around for some time in astrophysics,

but they didn't have a theoretical way of understanding it.

And then along came string theory and then the two got wedded.

Whichever way you look - whether up to the largest scale

or down to the very smallest, our universe may not be alone.

But for now, string theory remains a theory,

with no experimental evidence

for any of its mind-boggling predictions.

As we look down in scale, things get increasingly cloudy.

To stand a chance of seeing strings, we'd need a particle accelerator

a million, billion times bigger than the LHC.

Is this, then, the end of the line for the explorers

searching for the smallest thing in the universe?

It turns out there could well be a bottom of the rabbit hole -

an ultimate limit of how small we can go.

And there may be a way to reach this ultimate destination -

it's just a rather roundabout route to get there.

Dr Giovanni Amelino-Camelia is a theoretical physicist,

who 12 years ago came up with an idea that could lead us

to the ultimate destination at the bottom of the rabbit hole.

An idea that may lead us to question the very fabric of the universe -

the three dimensions of space and one of time, known as space-time.

Space time to an ordinary person is space time.

What is space time? There is no answer.

To us, space time is, er... Do you understand what I'm trying to say?

The challenge is that I don't have anything to work with

because the person who listen to me thinks know space time very well,

but then if I asked what is space time, he would have no answer.

Space time, they think they know very well what it is.

"For God's sake, space time! You know!"

But "you know" is all they can say.

So your audience is the worst,

because they think they know a lot about this subject.

But then they know nothing, completely nothing.

You see what I'm trying to say? It's very tricky.

If we have any notion of space-time, it is that it is smooth.

We can move smoothly from one cafe to another,

can be reasonably sure how long a journey will take.

But maybe not if you get small enough.

The ultimate small destination is known as the Planck length.

It is the theoretical limit of how small anything can possibly be.

Some speculate that this could be the ultimate level.

I mean, this could be where the laws of nature are fundamentally written.

But to get to the Planck length, you have to look a hundred,

million, billion times smaller than a quark.

At this tiniest of scales,

we may find answers not just about the smallest lump of stuff,

but about the very nature of space

and time in which all the stuff sits.

What could be conceptually more fascinating than

learning about the structure of space time?

But our current theories with all their limitations suggest

that at this Planck scale that we're talking about,

we should expect space time to, to be not smooth as we imagine

but more like, well, more like the foam of a cappuccino

and actually perhaps in, in a violently dynamical way.

The Planck length is where the rules of the large

and the rules of the small collide in a heady brew

called quantum gravity.

It's a seething tempest of space and time known as space-time foam, where

the very fabric of space and time twist and turn in every direction.

It is where the two great pillars of modern physics,

general relativity and quantum mechanics,

may finally be reconciled.

If we could understand what is happening down here,

we could end up with a theory of everything.

We are really far, far away from, from this realm,

and yet some of the most conceptually striking questions

about what, how is the universe made,

what are its basic rules, appear to reside in this distant scale.

So it's... At one side, we have this feeling of not having

any access to it, and yet it appears to be the place where

most of the answers we are seeking are somehow hidden.

All roads in physics lead to the Planck length.

But until recently,

no-one had a clue how we would ever know anything about it.

It was a problem Giovanni was determined to solve,

seeking inspiration and reassurance in the cafes of Rome.

I never understood what triggers an idea.

And it's kind of reassuring to be reminded that all this is

all about small - important, conceptually important,

but small - I'm still here, the Coliseum is still there.

When you're stuck chasing a certain answer,

you often discover that all it took to find the answer

was to look at the same problem from a different angle.

MOBILE PHONE RINGS

From the office.

Pronto.

12 years ago, Giovanni had a flash of inspiration

that we could reach the unreachable.

Over the last decade or so, what we started to figure out is

that it is possible to get indirect information on the Planck scale.

We cannot build a microscope that show us, shows us

the structure of space time at the Planck scale,

but we can get indirect evidence about the Planck scale

structure of space time is made.

Any explorer will tell you that if the way ahead is blocked,

you have to set off in a new direction.

Instead of trying to look directly down at the smallest scale,

the idea is to look up at the very biggest scale possible -

the entire universe.

It's an idea that is now reality...

..and a trick that is now being performed by the MAGIC telescope.

The idea is to use the vastness of the universe

as a giant magnifying glass.

Dr Robert Wagner is using this unique instrument to peer

at some of the most distant and cataclysmic events in the universe.

Under good conditions, as we have them right now,

we record 200 gamma ray or cosmic ray showers per second.

The Earth is constantly being bombard by high-energy cosmic rays,

gamma rays, the most energetic form of light.

But Robert is looking for the most extreme of these -

gamma ray bursts from colliding neutron stars or exploding

black holes in distant galaxies.

Gamma ray bursts are very violent events in the universe

and one key characteristic of them is that we cannot predict them.

So they can take place at any time at any place on the sky.

We get the information from satellite experiments.

This information is transmitted in an automatic way down here,

it takes about ten seconds, and then the telescopes will fully

automatically go to those gamma ray burst locations.

With these light weight telescopes

we're able to move to any point in the sky within only 20 seconds.

Those bursts last anything between one and 1,000 seconds.

Most of the bursts are really short lived.

So it's of great essence to be there as fast as possible.

Catching these violent but fleeting events

takes many nights of patient observing.

Well, this is a place I go right after the observations,

and this of course gives a quite different feeling

from looking at screens.

You look at the real sky and actually the stuff

we are observing and hoping to detect is somewhere up there.

Those black holes and galaxies, they are so far very away,

but at the same time, when you come here,

you realise they are real because, you know, all the photons

which hit my eye right now from those stars, they are real.

Although Robert spends his nights looking out

into the far reaches of the cosmos, he is actually trying to find out

how the universe works on the very smallest scale.

Things up there are so very, very far away.

The farthest galaxy we are looking at is shining light at the time

when the universe was just half its age,

it takes the light 7 billion years to get to here.

So that's a distance which, personally,

I cannot imagine, myself, right? It's a very abstract number.

At the same time, the scales we are looking at if we want to get to

the shortest scales are as similar small as this distance is large.

So it's really hard to imagine these things on scales,

which we see here on Earth.

But Robert's not really interested in the explosions themselves.

They act as the biggest particle accelerator in the universe,

way more powerful than anything we could ever achieve here on Earth.

He is interested in what happens to the particles,

in this case, photons, while they travel towards us

on their 7-billion year journey

through what seems like smooth, empty space.

But any distortions in the structure of space-time at the Planck scale

would affect photons of different energies in different ways.

Essentially, it's quite comparable to cars driving on a road.

A big car will not feel the fine structure of the road,

it will just roll along and will be, you know, just as fast as normal.

Whereas a small car, like a model car,

will feel every tiny ripple in the structure of the street.

The large car would be the low-energy photon,

because there is nearly no interaction with the structure

or the ripples in the road.

Whereas the small car would be the high-energy photon,

because it's smaller, there are more interactions with the road,

and this makes the photon travel slower.

The difference in speed is tiny.

But the length of the journey, half way across the universe,

could magnify the effect into something we might be able to see.

We just let those photons travel along the universe,

and of course they travel for billions of light years,

and only that long travel time makes this tiny effect visible to us,

which is to say, after such long travel,

we expect a few seconds' delay of photons of different energies,

and of course this is a delay which can easily be measured

with the MAGIC telescopes.

In 2005, just a few months after switching on the telescopes,

a gamma ray outburst from an active galactic nucleus tickled

the MAGIC mirrors, giving Robert his first tantalising glimpse

down to the smallest place in the universe.

It was the first time ever we observed such an effect,

or, to put it in cautious words, the hint of such an effect.

So clearly we were absolutely stunned.

Soon, we realised there is something in this data, which is extraordinary.

As soon as we dig deeper and deeper in the data,

it became apparent that photons of different energies may have

different arrival times at the instrument.

Those photons had to travel billions of light years.

The effect was on the order of seconds, maybe five seconds.

The Planck length is so small

that after a race of seven billion years,

the photons finished with a gap of just five seconds.

There are two possibilities here.

The first is that the photons rather inexplicably set off

five seconds apart.

The other explanation is more revolutionary.

This five-second delay could be our first glimpse of the smallest thing

in the universe, the first evidence of a lumpiness in space-time.

If true, it would shatter one of the most basic rules of physics.

To put it in simple terms, the speed of light is not constant.

It is dependent on the energy of the photon.

And that's revolutionary

because it's one of the fundamental laws of physics.

Einstein predicted speed of light is a constant,

no matter what you do, no matter where you are.

Under no circumstances should there be

a difference in the speed of light.

The conclusion from our measurements that this is not the case

would mean quite a revolution of physics.

The MAGIC observations provide a tantalising glimpse

of what awaits us at the smallest structures of space.

But to get there,

we've had to harness the entire expanse of the universe.

The journey to the very small is one of the most epic in science.

It takes us beyond the limits of what we can see...

..inside fundamental particles,

which may not be so fundamental after all...

..through a wonderland of extra dimensions and multiple universes...

..down to the smallest place in the universe,

a place that could change the face of physics.

And surely we expect a revolution in the laws of physics not

smaller than the one that took us from Newton's laws

to quantum mechanics a century ago.

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