What Is Reality? Horizon

There is a strange and mysterious world surrounding us.

For most of the time it's hidden from our senses.

I've always loved detective mysteries, and this is really the greatest mystery ever.

It's one of the simplest and yet most profound questions in science.

The search to understand the nature of reality.

But on this quest, common sense is no guide.

Quantum mechanics says that I can pass through that wall.

How often will it happen? Very rarely.

But wait long enough and it will happen.

Looking for clues has taken scientists to the frontiers of what is possible to know.

From black holes...

to the deepest structures of space and time.

And what they're discovering may change our understanding of reality forever.

Don't you find this confusing? I find this very confusing.

It's almost impossible to talk about using ordinary human language.

This search has attracted some of the finest minds in physics today.

But be warned.

Once you've entered their reality, yours may never look the same again.

Reality, for most us, is familiar, comforting and reliable.

It all sort of makes sense.

Trees grow vertically, footballs follow well-known laws of motion

and all our actions take place reassuringly in just three dimensions of space.

But physicists see it a little differently.

Reality is much weirder than it seems.

I feel like I'm standing still

but I'm actually zooming at 67,000 miles an hour around the sun.

I feel kind of solid, but I'm mostly empty space.

And all this stuff going on here with the game, maybe the flow of time is just an illusion.

The search to understand reality has led physicists far beyond surface appearances

to try and uncover its most fundamental laws and structures.

But when it comes to defining it,

reality turns out to be very, very elusive.

Is that it? You're going to ask me, what is reality? Oh, boy.

-What is reality?

-What...?

HE STAMMERS

You want something even shorter than what I said? What?

Reality is the philosophical concept which we attach to something which is real.

That doesn't help, right?

I might say reality is the set of things that we know to be the case.

Like what?

Like the fact that we're sitting here, talking,

like the fact that the world is quantum mechanical,

the fact that the universe has been around for 13.8 billion years,

the fact it's hard to get a date on Saturday night.

That's reality.

There's no escaping the fact that understanding reality is a truly daunting challenge.

But that hasn't stopped physicists from attempting the impossible,

trying to find out what it's all made of.

And for centuries, they've approached this question with a surprisingly simple technique.

They smash reality to smithereens.

Welcome to reality HQ, otherwise known as Fermilab,

a high energy physics laboratory near Chicago.

This is Professor Jacobo Konigsberg, particle hunter,

and one of the few people on the planet who can personally claim

to have helped discover a bit of reality.

The machine Konigsberg gets to play with every day is the most powerful particle accelerator in America.

The Tevatron.

But like everything to do with reality, it's hidden from sight.

We're looking at the Tevatron,

the Fermilab proton-antiproton collider.

It's ten metres underground.

These are the fields outside Batavia, Illinois.

Gorgeous day to look at it.

And as we speak,

underground you're having about ten million proton-antiproton collisions occurring every second.

It's been working for 20 years

and every day we basically push the boundaries of what's known.

It's the chocolate factory. We love it.

What goes on beneath these fields in the Tevatron

are some of the most violent collisions in the universe.

Deep underground in a four-mile vacuum pipe,

encased by superconducting magnets,

they smash together two subatomic particles

at close to the speed of light.

Their aim is to find, among the debris of these collisions, the elementary particles of reality.

Tiny and indestructible.

But there's just one hitch with this dramatic method.

When you collide a single proton with a single antiproton and you create this point of energy,

out of a single collision you can actually generate hundreds of particles,

hundreds of different particles that one, as a physicist, needs to try to identify.

Working out which of these are elementary,

is a problem that's defined particle physics for over 60 years

and has required an extraordinary coming together of theory and experiment.

The problem started with atoms,

once thought to be the only elementary particles.

When experimenters first broke into them, they discovered even smaller bits inside.

Electrons and neutrons and protons.

But when they tried to smash protons up...

they encountered a different kind of problem.

Small particles need high energies to wrench them apart,

which meant building bigger and bigger machines.

But what came out of these fabulous feats of engineering was a big surprise.

To the experimenters' delight, the first proton collisions

produced not just a handful of new particles but hundreds.

And when it came to identifying them,

they realised they needed help.

To work out what was going on, the experimenters turned to theoreticians,

the maths geniuses who solve physics problems with the pure power of thought.

This is Professor Frank Wilczek, a Nobel prize-winning theoretical physicist.

-How are you?

-Just fine! I got a collection of whoopie pies...

He lives in Cambridge, Massachusetts.

But he comes out to the beautiful countryside of New Hampshire to do his thinking.

Wilczek is one of the key architects of our current best description of reality,

the standard model of elementary particles.

This model is a detailed description of the basic building blocks of matter

and the forces that bind them.

-We got you a good selection of fundamental bits of reality.

-Yeah, you certainly have!

When the experiments were actually done, there was a big shock

because what happened was people found that when they collided two protons really hard together,

out came totally new and unexpected particles,

like K mesons, omega baryons pi mesons, electrons,

neutrinos, other mesons.

They ran out of names because the Greek alphabet is only so big.

There were such a bewildering variety of these baryons and mesons

that together, they became known as the particle zoo.

A whole new layer of reality had being discovered,

but the question no-one could answer was,

which ones were elementary?

They were discovered experimentally

with no underlying theoretical understanding of what was happening.

So the theorists, who wanted to get down to a simple description of nature,

thought they were ready to almost close the book on the laws of nature, were totally stymied

and had to go back to the drawing board.

Faced with having to explain these unexpected particles,

the theorists tried to come up with a simple and beautiful solution.

They wondered if the zoo would make sense

if it were actually combinations of fewer more basic units.

They called this new set of particles the quarks.

Altogether, six quarks were described by the theory.

Up and down quarks, strange and charm, and bottom and top.

At first, no-one believed they were real.

Then hints of them began to show up

and before long, these imaginary particles were actually discovered,

one by one, until the theory hit a roadblock.

The top quark was still missing.

Either they hadn't found it yet or it didn't exist,

an unthinkable proposition.

So together, the theorists and the experimenters decided to take a gamble.

They invested billions of dollars in a new class of accelerator,

massively more powerful than anything that had gone before.

By 1990, Jacobo Konigsberg had joined the hunt for the top quark.

He had at his disposal the biggest toy in particle physics,

the shiny new Tevatron, and a beautiful theory to guide him.

All eyes were on Fermilab.

Jacobo's team were looking for something so small, it had no discernible size.

They didn't know its mass.

And if it existed at all, it was extremely rare.

It was predicted to be the heaviest of the quarks.

But even if it did turn up, it would only last a trillionth of a trillionth of a second.

Finding the top quark was really, really very difficult.

We had to create thousands of billions of those collisions

in order to finally detect a few dozen of them that produced top quarks.

As if creating the collisions wasn't hard enough,

analysing the fleeting fragments of reality they produced

depended on the perfect performance of the most intricate scientific instruments ever built,

the collision detectors.

This is one of the pieces of the detector.

It's a big chamber

that has very, very tiny wires running across it,

it's full of gas,

and as particles come out of the collision point,

they leave tiny traces of ions that are picked up by these wires,

and then you can reconstruct the actual trajectory of each of the particles

as they emerge from the collision point.

This helped us tremendously.

So this is a piece of history

and we have it here shown as one of the most magnificent pieces of apparatus

that have helped us to decode reality.

Jacobo's team searched for the top quark for four years.

His handwritten diaries record their frustrated ambitions.

Over six million collisions, but still no top quark.

Then one day, everyone came together for a meeting.

This is the room where, after years and years of taking data,

we finally realised we had discovered a new particle,

we had discovered the top quark.

January 21st, 1995.

The first reaction from the whole room was silence, and then we broke into an applause.

Everybody was in disbelief

because it all had come together after so many years of hard work,

so many years of searches through many accelerators,

we finally had it here, and we were convinced beyond any doubt

that this was going to become part of reality.

The top quark was here to exist, to stay and here to be part of the history of scientific discoveries

So the feeling was ecstasy - pure ecstasy.

We all feel, I think, that this is our baby.

It's the particle that we unveiled and now we're studying and taking care of.

With the discovery of the top quark Physicists are close to understanding

one of the greatest mysteries of reality - what it's all made of.

They've finally tamed the particle zoo into an elegant set of unbreakable bits called

the Standard Model of Elementary Particles.

Six quarks, their six electron cousins - the leptons,

and four particles that carry force.

Together, these 16 pieces make up the world we see around us.

It's an amazing achievement

to have drilled down through the visible world

to the bottom layer of reality itself.

But there's a puzzle at the heart of this picture.

You like the fact that you're seeing it, you like the fact that you can explain how these characters

interact with each other, and who they are and what their basic properties are.

But then you don't know why there are so many, you want to think, what drives those numbers?

What's so magical about six quarks? What's so magical about six leptons? Why six?

Every time in history where we've had a really complicated description of reality,

someone has come along and unified this into something beautifully elegant.

And right now I think our best understanding of physics, again,

is just a bit too complicated to be the real deal.

While particle physicists dream of simplicity,

there's a whole other branch of physics that questions

whether reality as we know it can even be said to exist at all.

Welcome to the weird world of quantum reality...

..where nothing is quite as it seems.

Here, in Vienna, experimental physicist Anton Zeilinger

is about to unlock the mysteries of the quantum world.

He's going to perform a remarkable experiment that puts the very existence of reality into question.

Known to physicists as the double-slit experiment,

it's remarkable because it reveals two astonishing paradoxes about the nature of reality

That no-one can fully explain.

I'm now showing you the two-slit experiment

which contains one of the basic mysteries of quantum mechanics.

It is very simple.

We have a laser, we have a two-slit assembly

where the light can only go through two slit openings and we have an observation screen.

The experiment has one crucial feature - Zeilinger can control his laser beam so that it fires

single particles of light, called photons, through the slits.

Just single particles.

Lets do the experiment with a camera that's able to detect individual photons.

We have to cover it now because of the background light.

Sven, can you help me?

As the laser fires single photons, some will pass through the slits, some will bounce off.

Gradually, a pattern will emerge.

Now you see the photons arrive one by one at the camera.

Here's one, here's one, here's one.

So they really behave as mini bullets.

What would you expect them to do at the double-slit setup?

You would expect some of them going through this slit,

some going through this slit, so we would expect two stripes,

But what you get is something completely different.

Even though only single photons of light are being fired through the slits,

they don't create two lines. They mysteriously create three.

According to physics, this pattern of multiple stripes is what you get

when you shine a beam of light at the two slits.

Because when it's a beam, light behaves like a wave,

creating a classic pattern of light and dark stripes

But it's totally incomprehensible how SINGLE particles of light can create this wave pattern.

There's a contradiction here.

On the one hand, we have individual particles which can go through one slit only at a time.

On the other hand, we have the stripes which indicate they are waves which go through both slits.

How can something go through one slit and both slits at the same time?

The idea that a single particle of light can somehow split in two

and go through both slits at once

goes against all the laws of nature that we know.

From a basic intuitive point of view, this is not possible to understand

if you stick to a picture of reality as we are used to in everyday life.

Over the last two decades, Zeilinger and his colleagues have tested quantum theory to its limits.

They've even proved that it's not just photons that behave strangely, but atoms and molecules, too.

You might ask, why can't we observe quantum reality?

But this is where things gets even more weird.

If you put detectors by the slits, the mysterious behaviour stops.

The photons behave just like bullets.

Take the detectors away...

the multiple stripes mysteriously reappear.

What's going on?

Rather astonishingly, it seems that we can change the way reality behaves...

just by looking at it.

But this also means that reality has a secret life of its own.

We know what the particle is doing at the source when it is created.

We know what it is doing at the detector, when it's registered,

but we do not know what it is doing in between.

We cannot describe that with our everyday language.

If you're finding this hard to get your head round, don't worry - you're in good company.

The paradoxes of quantum theory drove even Albert Einstein to despair.

There's a famous story from the history of physics.

One day, Albert Einstein

asked his friend, Niels Bohr, a Danish physicist,

"Do you really believe the moon is not there, when nobody looks?"

Bohr's answer was, "Can you prove to me the opposite?

"Can you prove to me that the moon is there when nobody looks?" This is not possible.

For more than 70 years, physicists have debated what quantum theory means for reality.

Zeilinger's detective work may yet lead us to an answer.

Quantum physics is an exciting theory because it is extremely precise,

it is mathematically beautiful and it describes everything.

It just doesn't make sense.

So reality turns out to be stranger than we ever imagined.

Everything has the power to be in two places at once.

But we'll never see it.

It's all very peculiar.

You'd be wrong to think you can ignore it, because quantum reality

might be about to change our lives in a big way.

Here at MIT is a physicist who sees, in reality's strange behaviour,

enormous power and opportunity.

Seth Lloyd is aiming to revolutionise our lives,

with a new class of computers, like nothing the world has ever seen.

This is a quantum computer. It actually happens to be

the best and most powerful quantum computer of its kind in the world.

It runs on superconducting circuits that are cooled to within

a few thousands of a degree of absolute zero.

And it contains in its guts a little tiny bit

where a current going round like this represents a zero,

and a current going like that represents a one

and a current going both directions at once is zero and one.

And that's what's going on in here at the moment.

Whereas a normal computer bit can only represent a zero or a one, a quantum computer bit can be zero

AND one at the same time.

Link these multi-tasking bits together

and they can do vast numbers of calculations simultaneously, opening up new worlds of possibility.

Quantum mechanics is weird and quantum computers use quantum weirdness

to process information in ways that ordinary classical computers could never even comprehend of doing.

As a result, even a tiny quantum computer with a few hundred quantum bits in it could be more powerful

than a classical computer the size of the whole universe.

What's unique and impressive about Seth's engineering of the quantum world

is that, for the first time ever,

he's opening up a line of communication between our reality and quantum reality.

Quantum bits are very small, really teeny, cannot see it with the naked eye,

cannot see it through a microscope.

But you need this whole roomful of equipment to tickle this quantum bit and get information

from our human scale down to this extremely microscopic scale where quantum bits actually live.

If you talk to them just right, and massage them

till they're happy enough, then you can get them to do what you want.

Sounds easy

but Seth has to overcome the most mysterious rule of reality -

the fact that his quantum bits stop being able to do two things at once

as soon as he tries to observe them.

The quantumness of reality is apparently very sensitive.

This is actually one of the main problems with building large-scale quantum computers

because it doesn't take just me or you to look at something and make the computer fail,

it can just be some passing electron wandering around,

bounces off this little superconducting loop and says WHOA!

The electrons in there are going around like that, that's enough to mess up your quantum computation.

Seth clearly faces some of the most difficult technical challenges science has ever known.

That's going up again.

But if he overcomes them, quantum computing has a huge potential to change our world.

It's very real.

My favourite use for quantum computers

is to use them to understand the weird features of the universe.

Classical computers - lets face it - they kind of think the way we do,

they're not so good for understanding quantum mechanics.

If we're ever really to understand how this quantum universe works at bottom, we need quantum computers

to serve as our intuition, for understanding the fundamental workings of the universe.

Seth's computer depends on things being in two places at once for its power...

..but there's a growing number of physicists who don't believe that

this is what reality is really like at all.

They think the answer to this puzzle lies beyond our universe.

Just checking to see whether reality is still there.

Max Tegmark is a cosmologist. He's studied the greatest mysteries

of the universe, from the big bang to black holes.

When it comes to explaining how reality works,

he draws his inspiration from one of the most bewildering ideas in cosmology...

parallel worlds.

This theory says that beyond the edges of our universe

there are an infinite number of other universes.

It sounds like the stuff of science fiction...

that there's another you living more than a trillion trillion light years away.

But it's not the only version of this theory.

Max thinks that parallel worlds don't just exist beyond our universe.

They're here, millimetres away. And they're being created all the time.

I'm here right now

but there are many, many different

Maxes in parallel universes doing completely different things.

Some branched off from this universe very recently

and might look exactly the same except they've put on a different shirt.

Other Maxes may have never moved to the US in the first place or never been born.

This vision of reality says that any time we go to work,

there'll be another universe where we stay at home.

There are universes where we all have different careers.

There are also universes where we don't even exist.

It's a disturbing idea, developed in the 1950s,

but for Max, it's the best and only solution to the paradox at the heart of quantum reality.

The big problem with quantum mechanics is that the little

particles that we're all made of can be in multiple places at once,

yet I'm made of little particles and you never see me in two places at once, so what's going on here?

Max thinks that the maths of quantum theory is telling us something remarkable.

So whenever the equations say that this tennis ball is in

many different places at once, what that really means is that

our reality is branched out into multiple universes and in each one, the ball's in a definite place.

According to this theory, when the photon of light faces two slits...

it doesn't split in two.

It splits the world in two.

Every photon in the double slit experiment creates a new parallel world...

..which means what we think of as reality is just one

of an infinite number of realities, each one slightly different from the next.

However strange this theory sounds,

Max believes you have to accept reality as you find it.

Like if I get a parking ticket, there's always a parallel universe where I didn't.

On the other hand, there's yet another universe where my car was stolen,

so you win some, you lose some. But seriously...

my job as a scientist isn't to tell the universe how to conform to my preconceptions of how it should be,

but to look at the universe and find out how it really works.

It seems that whatever our senses are telling us about reality,

we only get to experience a fraction of what's really going on.

Take it as it comes, you know - we've been humiliated before by the vast universe,

since Copernicus, since the discovery of the distant galaxies,

the Big Bang, and, er, this is a dis... this is another

sort of humiliation where... er, we're finding that our thought... our ordinary, er, sensing

of the world is so very, very partial, we only see tiny averages of this very rich structure.

Quantum reality is about the strangest discovery that physics has ever made.

But it's also fantastically powerful.

Not only has it helped to create our modern computer age but it's helped us understand all kinds of phenomena

from the shining of stars, to the colour of gold.

It's changed our relationship to reality forever, philosophically and practically.

But that relationship might be about to change again.

In the last few decades, an astonishing new idea has been taking shape.

An extraordinary vision of what reality might be

that combines every field of physics from quantum to the Big Bang.

If it's true, it will trigger a bigger change in thinking about reality than anything we've seen.

And it all began one day in San Francisco.

Professor Lenny Susskind is one of America's most eminent theoretical physicists.

Back in 1981, he was developing a theory about how matter was made out of strings,

when a local entrepreneur asked him to host a small, private science conference.

Susskind invited a British cosmologist to give a talk.

It was Stephen Hawking, and the lecture he gave about black holes

was to change the course of Lenny's life.

That's where Stephen dropped the bombshell that left us so confused for 20 years.

At the time, Stephen Hawking was the pre-eminent scholar working on black holes.

He'd achieved amazing insights into the inner workings of these mysterious objects.

Black holes are the most terrifying places in the universe.

Created when a giant star dies, at their dark hearts is a point of infinite gravity,

so powerful, nothing can escape it - not even light.

Lenny was expecting to learn something interesting about black holes.

What he didn't expect was for Hawking's new theory to challenge everything he knew about reality.

I had absolutely no idea at the time

that this was going to change my life for the next 20 years.

Stephen began to talk about black holes and told us a story which seemed so crazy and so strange.

It seemed absolutely wildly impossible - that black holes

would violate all the principles of physics that we knew.

Hawking's revelation was that black holes, instead of lasting forever, as everyone thought,

eventually disappear,

leaving no trace of anything,

including something physicists consider a fundamental part of reality - information.

If information was lost in ordinary circumstances in this room, that would be bad,

because then all kinds

of weird stuff would start happening, like,

the hour of time could start going backwards,

you know, clocks might not work, we all might disappear like that.

The fact that information is conserved in ordinary physics, is at the very basics of physical law.

Today information is as important a part of reality as matter and energy.

Everything physical contains information.

It's the description of what something is - its colour, its mass, its location.

And crucially, like energy, information can never be destroyed.

I just knew, or felt, deep in my gut, that Stephen had to be wrong.

That lecture set me on a mission, you bet, and that mission was to reconcile the two

competing and conflicting points of view about black holes -

that they eat information and evaporate but information is not allowed to be lost.

As Lenny drove home that night, he knew his first task was to learn as much about his subject

as possible - mysterious and terrifying black holes.

Every black hole has a boundary known as the event horizon.

It's the point of no return.

If you pass it, you'll never escape the black hole's gravitational pull.

If you get too close to a black hole,

you're done. If you get sucked into it,

nothing can come out, not even your screams, not even your...

radio transmission for help, nothing.

If anything passes the event horizon,

it takes its information with it.

Lenny had to find some way for black holes to evaporate

without destroying the information inside them.

But the physics of black holes is so complicated that he wrestled with the problem for the next 12 years.

Then in 1993, one fine day in Stanford, Lenny wandered into the physics department

and saw something that gave him an amazing insight into what the true nature of reality might be.

The insight...

to what became known as the Holographic Principle simply happened one day

when I was walking in the physics department and came upon a hologram.

Well, when I saw the hologram it occurred to me that there's

a very big difference between a hologram and an ordinary picture.

When you see a hologram you can look around it and you can see what's behind the lady's head there.

Not just the surface, but you can see what's behind her,

there's a sense in which it's really capturing three-dimensionality.

It was capturing the full three-dimensional

structure of the room and everything behind her, so when I passed it by,

almost jokingly I said to myself, maybe the horizon of a black hole is something like a hologram.

The stuff that falls into the black hole is three-dimensional.

The stuff of the horizon is two-dimensional.

But maybe in some way, the stuff of the horizon is like a hologram,

capturing the full three- dimensionality of the things that fell into the black hole.

Holograms are created from information encoded on a flat surface.

Lenny realised that if black holes were like holograms,

then there's only one place where their information could be stored - the event horizon,

which would mean it would never fall in and it would never be destroyed.

Not only did Lenny's insight help save information from black holes,

but it lead to a new mathematical tool, called the holographic principle,

that says all three-dimensional objects can be encoded in only two dimensions.

The holographic principle has morphed from a wild speculative almost crackpot idea.

Complete consensus has formed around it.

It is almost completely accepted across theoretical physics.

It has gone from being a wild idea to being an everyday tool of theoretical physics.

But Lenny didn't stop there.

He and other physicists made a truly shocking leap of the imagination.

They asked - what if the whole of reality is a hologram?

Projected from our own event horizon -

the far edges of the universe.

Maybe the real information in the world is not where it seems to be.

Maybe it's way out far away at the boundaries of the universe

and that it's completely wrong to think that things fall into black holes,

rather the black hole and things that fell into them are really holograms,

or really images of things taking place very, very far away.

If Lenny is right and the ultimate nature of reality is holographic,

it would mean our three dimensions are an illusion,

that we're being projected from information that's stored at the outer reaches of our universe.

It's an incredible vision...

but if you think you understand it, you probably don't.

OK, I think I'm getting it, so that...

Don't think you're getting it, cos you're not getting it

and the reason you're not getting it is because nobody get it.

There are some times when we...

It's like quantum mechanics - nobody understands quantum mechanics.

We know how to use it and we know how to make predictions of it, but nobody has their heads around it.

It seems utterly bizarre that the ultimate nature of reality might be holographic.

That at the edge of our universe, there might be a shimmering sheet

of information that describes the entire universe within,

including you and me and everyone we know.

But incredibly, this theory is about to be put to the test.

We maybe on the brink of finding out that the world is a hologram.

Back at Fermilab,

a unique million dollar experiment is just beginning.

Expert technicians are building an extraordinary machine they call the holometer.

Designed to be so sensitive, it can measure the smallest units of space and time.

It's the brain-child of Professor Craig Hogan,

the Director of the Centre for Particle Astrophysics at Fermilab,

who became intrigued by an unexplained sound, recorded by scientists in Germany.

WHITE NOISE

This recording is noise picked up by a gravitational wave detector.

But it's not gravitational waves.

Hogan thinks that buried within it might be the sound of holographic reality.

So he's designed an experiment to test his theory.

Hogan's holometer will bounce beams of light between mirrors,

timing how long the beams take to return.

It will be able to detect infinitesimally small delays, or as he calls it -

fuzziness in space and time.

So this is one of the beam tubes of our holometer.

It's a six inch steel pipe and we're going to bolt them together

in one big tube, 40 metres long

and do that five different times

and the laser light's going to go down the centre of the tube.

So before we do that, we have to clean them out

cos the optics are super precise, need to be kept super clean.

Right now, they're cleaning out the end station,

this is this sardine-can like object,

it's where the business guts of the holometer are going to be.

It's where the mirrors and so on that are doing the precise measurement are going to be.

Ultimately, this machine might tells us that space time is sitting still.

If the light goes out the two arms and comes back at exactly the same time and there's no extra jitter

then that's a classical space time,

but it could be that we'll find a little bit of air or fuzziness

in there and that would be the clue that we live inside a hologram.

Craig thinks that if reality really is holographic

then the closer you look at it, the more insubstantial it will be,

like a photograph

enlarged over and over again.

This fuzziness will disturb his laser beam and that's the evidence he's looking for.

Well, it's very exciting to actually be building a machine with this kind of

precision to be able to do this, you know, we're measuring

the arrival time of wave fronts of light to a very small fraction the size of an atomic nucleus.

And timing those pulses to microsecond accuracy.

Nobody's ever done that before, nobody's ever tested to see

whether space time actually stands still at that level.

If Craig Hogan proves that reality is holographic,

it will be one of the most important discoveries in physics.

It may cause as big a change in thinking as the revelations of quantum theory.

But if there's one thing that stands out about all the theories used,

to probe and explore reality today,

it's this - their best and most perfect expression is not in words, it's in maths.

The connection between mathematics and reality is a miracle, but it works.

It's actually unreasonable how well mathematics works,

why should the world behave according to mathematical laws?

It is not only that it becomes easier to describe with mathematics

as you go deeper and deeper into reality,

mathematics becomes the only way to describe reality.

If our most detailed knowledge of reality, from fundamental particles to ripples in space time,

is really best described in maths,

could it be that the ultimate definition of reality is staring us in the face?

Cosmologist Max Tegmark seems to be fond of radical explanations of reality

and it's no different when it comes to maths.

Instead of just accepting mathematical order in the world,

he's been trying to figure out why it exists and where it comes from.

He thinks he has a solution.

To me, maths is the window on the universe.

It's the master key to understanding what's out there.

I wouldn't say I'm completely monogamous with equations,

but there are just a very few I love the most.

I love them because they describe exactly what's going on

outside the window in our universe.

These equations describe how light behaves.

This equation describes how gravity behaves.

This equations describes how atoms behave.

These equations describe what happens when you go really fast near the speed of light

And it's just amazing to me that a little bit of scribbles like this

can capture the essence of what's going on in this very complicated looking universe out there.

Galileo way back in the renaissance already remarked that nature seems

to be a book written in the language of mathematics.

This all came after Galileo,

so why are we discovering even more and more

mathematical regularities out there, what is it telling us?

I think the universe isn't just described by math...

I think it is math.

I think our entire universe is a giant mathematical structure that we are a part of.

And that, that's the reason why the more we study physics

the more mathematical regularities we keep discovering.

Max's theory pushes at the edges of physics and into the realm of philosophy,

conjuring up the oldest question of all -

what is real?

I think the universe is a mathematical object, it's just out there,

existing,

in a sort of platonic sense, it's not that it's existing inside

of space, and time, but space and time exists inside of it.

And that really changes our perspective of it and that

really means that reality is very different from how it seems.

If Max is right, maths isn't a language we've invented,

but a deep structure we're gradually uncovering like archaeologists.

An abstract, unchanging entity that has no beginning and no end.

As we peel back the layers, we're discovering the code.

Strange as it seems, it's a comforting theory

because if reality is a mathematical object,

understanding it might be within our reach.

If I'm wrong, it means fundamental physics is going to eventually hit a roadblock

beyond which we can't understand reality any better.

If I'm right, then there is no roadblock

and everything is, in principle, understandable to us.

And I think that will be wonderful because we'll only be limited by our own imagination.

These two grand visions of reality - the mathematical structure and the cosmic hologram,

represent theoretical thinking at its most imaginative and beautiful.

They may lead us towards a bright future or they may end up being discarded

because as all physicists know, nothing becomes real without being put to the test.

Few know this more acutely than the scientists at Fermilab.

Right now they're engaged in the greatest race of modern physics -

trying to find a bit of reality that's been missing for 40 years.

It's the most important particle of all - the Higgs Boson.

Nobody really understands the origin of mass and the Higgs particle

was introduced to explain why different particles

have different masses.

So, it is important because it answers one of the most fundamental unknowns

in reality, in particle physics, mass makes reality and we don't know where it comes from.

It's round-the-clock work, and people running computer codes,

sifting through the data, finding new ways of looking for

the Higgs because you can get incredibly creative.

In fact, this is one of the things that happens here, that you start doing the easy analysis,

the easy way to look for things and as it gets harder, you get more and more creative...

The Higgs is now Fermilab's number one priority,

but they aren't the only ones looking for it.

They have competition...

..from the biggest particle accelerator of them all -

the Large Hadron Collider in Geneva.

It's more than three times as powerful.

So it may yet be the one that discovers the Higgs first.

Meanwhile, the Tevatron continues its ten million collisions a day.

I feel really proud of this machine.

It's been a beauty of an instrument for many years

and hopefully it will help us find unveil one more secret of reality in the very near future.

Billions of dollars have been poured into this quest

and thousands of physicists around the world are looking for the Higgs Boson,

but it's still theoretical.

What if we don't find it?

OK, so if we don't find anything that has the properties

that are expected of this Higgs Boson

or some combination of things that can do the job,

we'll really, really, really have to rethink a lot of what we thought we knew...

That won't happen, we'll find something!

It may be that we are standing on the verge of a new version of reality.

We have these clues, quantum mechanics, relativity,

the holographic principle, a few others,

and it's just waiting around for somebody to really

put it together into, what does it really say about reality?

Physicists have redefined reality by close measurement and observation of the material world.

They've drilled down to the bottom layer,

discovered that we can change reality just by looking at it...

..and begun to sense that information encoded at the edge of our universe,

could be more important than matter.

But in the end, reality is perhaps best defined

as an intelligent conversation with the universe,

that will continue as long as we're around to ask questions.

It's human nature to keep asking questions,

it's fun and it's challenging and it's what makes us human.

If there is an ultimate version of reality, I think it's a long way before we get there...

so I don't want to be part of that.

I would guess that there are limits to what we can understand,

but old people always think there are limits to what we can understand,

it's the young people who push past those limits.

MUSIC: "Is That All There Is" by Peggy Lee

Subtitles by Red Bee Media Ltd

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