Original subtitles

What is nothing?

It's an extremely, extremely difficult question to answer,

because if you think about it,

wherever you look around you, there always seems to be something there.

Things appear almost impossible to escape from.

Even just trying to imagine true nothingness

seems like an impossible task.

But this is more than just a philosophical question.

I have here a box. What would happen

if I were to remove everything I possibly could from inside it?

All the air, dust, every last single atom,

until there was no thing left.

What, then, exists inside the space in the box?

Is it really nothing?

You might wonder why this matters.

Well, emptiness is what makes up almost the entire universe.

Even the atoms that make up our bodies

and the physical world around us comprise mostly of empty space.

This film tells the story

of how we've begun to understand what is known as the void,

or the vacuum.

Emptiness, or simply nothing.

It's about reality at the very furthest reaches of human perception.

A place where the deepest mysteries of the universe may be held.

This film reveals how,

using ingenious technology,

humans have transcended their physical senses,

and found ways to understand and probe the universe

at the smallest scales.

Today, we believe the void contains nature's deepest secrets.

It might even explain why we exist at all.

And that's because, to the best of our knowledge,

the entire universe appeared nearly 14 billion years ago

out of nothing.

For over 1,000 years,

our understanding of empty space was defined by one man -

the Greek philosopher Aristotle.

To Aristotle, the concept of nothingness was deeply disturbing.

It seemed to present all sorts of problems and paradoxes.

He came to believe that nature would forever fight against

the creation of true nothingness.

As he put it, nature abhors a vacuum.

These words stuck for over 1,000 years, because after Aristotle,

people who attempted to make empty space faced an uphill struggle.

It seemed nature was indeed doing everything in its power

to stop them.

Well, the whole mystery of nothingness

is contained inside this simple drinking straw.

Let me demonstrate. If I suck out the air from the top of the straw...

..more air immediately rushes in to fill the space left behind.

And even more weirdly, if I block off the bottom of the straw and suck...

..the walls of the straw collapse in on themselves.

It's as though the universe won't allow me to make nothingness.

And it gets even weirder. If I take a sip of my drink...

..and pinch off the top,

then it seems nature is so intent on stopping me

that even the law of gravity is suspended.

So it's not hard to understand why people believed

that it was impossible to make truly empty space.

But there is a very simple explanation

for why a straw behaves like this -

a reason that would come as a profound shock to the people who worked it out.

By the 17th century, some strange exceptions were being found

to nature's abhorrence of empty space.

And it was beginning to seem

like there may be ways of tricking nothingness into existence.

The man who would finally do what Aristotle thought impossible

was an Italian Jesuit called Evangelista Torricelli.

Torricelli's experiment would, for the first time,

create and capture empty space for long enough to begin to study it.

This is how the experiment went, with a tube filled with mercury

and a finger really strongly clamped over the end.

The tube was then turned upside down

and then placed into the bath of mercury.

At this point, the mercury was released.

You can now see it dropping down.

And then it stops.

So I guess the important thing is that...

that isn't trapped air.

We started with a tube filled with mercury, and all we did was we let it drain out.

But it doesn't drain out completely, it reaches a level and stops.

Torricelli's experiments had not only created an airless space,

it had also shown that the atmosphere has a specific weight.

The reason my straw crumples when I suck the air out

is because of the pressure of the atmosphere that surrounds it.

But Torricelli's apparatus was overcoming this

by using the extreme weight of mercury and a rigid glass tube.

The level of mercury in his tube

was a measure of the weight of the atmosphere.

The level is, of course, determined by the weight of the mercury on the one hand,

and the weight of the air pressing down on the other.

And so the two balance out, like scales.

They'd found a way to weigh the atmosphere.

And Torricelli wrote this fantastic phrase.

He said, "Noi viviamo sommersi nel fondo d'un pelago d'aria elementare."

"We live at the bottom of an ocean of air."

Suddenly, the air really was a substance.

But I guess the real mystery for me now is, what's inside here?

Could this really be nothingness?

Indeed.

In revealing that the air has a weight

and that it's pushing down on us all the time, filling any space it can,

Torricelli had managed to create an empty space,

a type of nothingness that could now be studied.

Over 1,000 years of thinking about the way nature worked

was beginning to crumble.

Medieval philosophy, much influenced by Aristotle, supposed,

reasonably enough, that there is no such thing as empty space in nature.

And yet here is a pretty simple device -

a long, thin glass tube with some liquid in it -

which is able to produce, says Torricelli, an empty space,

thus showing that Aristotle and his disciples are wrong.

How can you show that centuries of philosophical tradition are wrong

just by doing a trick?

That didn't seem right at all.

But Torricelli was right,

and it would fall to philosopher and scientist Blaise Pascal

to develop and refine his work.

As Pascal began investigating Torricelli's ideas,

he discovered even more peculiar properties.

In Paris, he carried a mercury tube to the top of a huge tower

and recorded the mercury dropping to a lower level than it had been on the ground.

It seemed the pressure of the air fell as you went higher.

Pascal's experiments would lead to the realisation that the Earth

is cocooned in an atmosphere that rapidly thins out the higher you go...

..eventually becoming the cold, silent expanse of space.

Torricelli and Pascal had begun to unravel a profound truth -

nothing is everywhere.

Our Earth is merely a tiny speck of dust,

floating through a vast expanse

of an utterly silent, inhospitable void.

Nature doesn't abhor a vacuum.

A vacuum is nature's default state.

So what was this vast, empty space?

Now it was possible to make it on Earth,

scientists became deeply curious.

What exactly were the properties of nothingness?

After Torricelli and Pascal's experiments,

many scientists became fascinated

with studying the properties of the vacuum.

And they found some very odd things.

For instance, placing a ringing bell inside it became silent,

you couldn't hear it from the outside,

because, having removed all the air,

there was no medium to carry the sound waves.

Most intriguingly, although you couldn't hear the bell,

you could still see it.

This means light must be travelling through the vacuum.

But how could it do this?

For those scientists carrying out experiments with the vacuum,

there was just one simple conclusion.

The vacuum wasn't empty after all.

The fact that they could see inside it

meant that there still had to be something left in there.

Just as air carries sound waves,

they believed there had to be a medium carrying the light waves.

And whatever it was, it was proving very difficult to get rid of.

The nothingness that had been glimpsed by Torricelli and Pascal

now appeared to be a something -

a mysterious substance which carried waves of light.

And if that this substance existed in our vacuums on Earth,

it meant that it also existed out there.

It appeared once again that nothingness could not exist in nature.

Everything in the universe appeared to be sitting within an invisible medium,

what scientists called the luminiferous aether.

It was clear for many reasons, many good reasons,

that light was a kind of wave.

But if light is a kind of wave, what's it a wave in?

Sound waves are waves in air, light waves are waves in what came to be called,

from the early 1800s, the luminiferous aether,

the light-carrying fluid that fills all space.

If there's a fluid that fills all space, if light is a wave, nowhere is empty,

because light travels everywhere.

So at the very moment when it seemed absolutely plausible

that there can be empty space, it is obvious that there isn't.

And that there's this stuff called aether that carries light.

The problem was that this aether

appeared to be so subtle and so intangible

that it eluded all attempts to measure it.

It wouldn't be until the end of the 19th century that an experiment

would be built that was sensitive enough to reveal the truth.

The experiment would take place in the United States,

and Albert Michelson, the scientist who conducted it,

would go on to become America's first Nobel Prize winner.

From a young age, Michelson had relished tackling

the particularly difficult practical problems in physics.

He'd earned his reputation

by making extremely precise measurements of the speed of light.

Having completed his work on light, Michelson travelled to Europe

to spend some time amongst some of the best scientists in the world.

And it was there that he became fascinated with the topic

that everyone was talking about - the mysterious luminiferous aether.

One idea in particular captured his imagination.

It had been proposed that if you could measure the speed of light accurately enough,

it might just be possible

to actually deduce the properties of the aether.

And this is how.

If there was an aether, then as the Earth orbited the sun,

we should be able to detect its presence.

It would be like sticking your hand out of the window of a moving car.

You feel the rush of wind as the car travels through the air.

Michelson realised that if this picture of the aether was true,

then two light beams should travel at different speeds on Earth,

depending on the direction they were moving through this aethereal wind.

The difficulty was actually in making such a measurement.

It seemed like an almost impossible task.

The problem is this.

The speed of light is over 186,000 miles per second.

Now that's pretty nifty.

In comparison, the Earth virtually crawls around its orbit.

So the difference in speeds between those two light beams would be tiny -

something like one part in 100 million.

So the precision needed to get any sort of meaningful result

was way beyond anything that scientists thought was possible at the time.

But not so the headstrong Michelson.

He began to work his way round the problem.

He started to develop techniques and precision instruments

that he believed would be capable of unlocking the secrets of the aether.

From 1881, Michelson was taking measurements,

and tweaking and refining his apparatus.

But it wouldn't be until 1887

at the Case School of Applied Science in Cleveland, Ohio,

that Michelson would finally build a machine sensitive enough

to give him some definitive answers.

There he joined forces with another scientist, Edward Morley,

to conduct what was to become one of the most notorious experiments in physics.

The original apparatus was set in a solid block of sandstone,

and then suspended in a bath of mercury

to remove any vibrations that might affect the measurements.

It was incredibly hi-tech and very expensive.

Think of it as an 1880s version of the Large Hadron Collider.

OK, so here's how it works. Light is emitted

from this source.

In the middle is something called a beam splitter,

which divides the light up into two parts.

Over here are two mirrors,

which reflect the light back to the middle

where they recombine at the beam splitter.

The light is sent down to this detector. Now,

Now, because of the wave-like properties of light,

you see a very specific pattern here.

Basically, if the light has travelled at the same speed along the two paths,

then you see a bright spot in the middle of the pattern.

So here's the really clever part.

Michelson and Morley reasoned

that if the Earth really was moving through a stationary aether,

the experiment should behave in a very different way.

Let's look at what happens when we simulate the effect of an aether.

The light leaves the detector

and gets split.

Now here's the key.

The light that travels against the aether and back again

covers this journey in a different time

to the light travelling across the aether.

This means that when the light waves recombine,

they now interfere with each other.

This interference means that the image

will have a dark spot at its centre.

See this, and you know that the void must be filled

with a stationary medium through which the Earth is moving.

Of course I can't be sure exactly

what was going through the minds of Michelson and Morley

as they began their experiment,

but it is a safe bet that, given the scientific consensus at the time,

they were convinced that the aether really existed.

So they would have been sure that they would have found light

travelling at different speeds as it moved in different directions.

But it didn't.

No matter how they rotated their apparatus,

they always found light travelled at the same speed.

Michelson and Morley had gained an extraordinary and accurate result.

But the idea of the luminiferous aether was so ingrained

that they believed simply that their experiments had failed.

So what is going on?

Why didn't Michelson and Morley's experiment reveal the result they were expecting?

How could light always be travelling at the same speed?

Well, the answer is simple. The aether doesn't exist.

No matter what light is doing, how it is travelling,

it doesn't need to be carried along by this mysterious stuff that pervades the vacuum.

So how does light move through empty space?

Well, by the end of the 19th century,

light was known to be in fact

a combination of fluctuating electric and magnetic fields.

But it would take the genius of Einstein in 1905

to reveal that this picture of light doesn't need an aether.

He showed that it has the weird property

of being able to propagate through completely empty space.

So the message from the failure of Michelson and Morley's experiment is this -

there is no aether.

Maybe the vacuum is really empty.

If only it were that simple.

Almost as soon as Michelson and Morley had revealed,

by accident, that you really could have nothing...

..scientists began to discover some very weird properties of nature.

In the 100 years that followed Michelson and Morley's experiments,

physics and our understanding of the vacuum

has been totally transformed.

But what drove this huge shift was not simply scientific curiosity.

But the fact that in the late 19th century,

the vacuum and its many applications had become big business.

Industry was finding ever more ingenious ways

to make money out of nothing.

Understanding and harnessing the vacuum turned out

to lead to a wealth of new technologies that we just take for granted today.

Everything from the light bulb to the television

were only made possible

because they could contain within them small volumes of vacuum.

The filament inside a light bulb can glow for long periods

because it is contained within a vacuum.

Expose it to air and it would simply burn out in seconds.

As cities around the world began to electrify,

the demand for light bulbs grew massively.

The engineers became ever more skilled at creating cheap, efficient vacuums.

This technology would give rise to a huge range of gadgets -

everything from the valves in radios and early computers

to the television.

But all the technological innovations that came from harnessing the vacuum

would pale into insignificance when compared to what scientists

would soon find out about the fundamental nature of reality.

Because vacuum technology was getting so much cheaper,

and more efficient,

scientists all over the world could use it as a tool for research.

In empty space, nature's tiniest constituents could now be studied

without interference from the contaminant-filled air of the outside world.

This revolutionised physics.

Because of the vacuum, X-rays were discovered in 1895.

The following year, the electron was identified for the first time.

And in 1909, Ernest Rutherford would use vacuums

to help reveal the strange structure of the atom.

These discoveries were all feeding into a radically new picture

of the way nature works at its smallest and most fundamental level.

It was a theory that would come to be known as quantum mechanics.

And the submicroscopic world it describes behaves very differently

to the world we are used to.

This is a world where, against all common sense,

it seems impossible to ever truly have nothing.

This is the classical world,

action and reaction.

Cause and effect.

It is sensible, certain and knowable.

But the quantum world soon revealed itself to be very different.

There was one discovery that was particularly troubling

and it's known as Heisenberg's Uncertainty Principle.

In everyday life we are used to doubt, to uncertainty.

How can we be sure that something is this way or that way?

Well, it turns out that nature itself is based on indeterminacy,

in uncertainty.

The world of quantum physics, the microscopic world, is a world of uncertainty.

It's a world where you can never be sure of what is going to happen.

Not because your measurements are not good enough, simply because,

at a very fundamental level, nature itself is based on uncertainty.

OK, I would like to get across the essence of Heisenberg's Uncertainty Principle.

I'm going to use a non-mathematical analogy.

We have to be careful here -

it is just an analogy so we shouldn't push it too far.

I have here two identical memory sticks.

On the first one is a high-resolution image.

It is a picture of me having a game of pool.

We can see it is very detailed.

In fact, I can zoom in...

..even quite closely onto the pool ball.

And you see, even at this magnification,

I can still see the precise position, I can see the edges of the ball very detailed.

But what I don't know is how fast the ball is moving

or what is going to happen next.

Now, on the second memory stick is another file. It's a very different kind of file.

It is a movie.

The important thing to note is that the file is the same size

as the high-resolution image.

Now, have a look at this.

Now we can see the whole movie playing out. It is the same scene,

but you can see all the balls moving.

But if I zoom in on some detail...

..very quickly the balls become fuzzy and blurred.

So for the same amount of information,

although I've gained knowledge about how the balls are moving,

I've lost information about their exact positions.

So with the more I know about where something is,

the less I know about how it is moving.

In the quantum world,

I cannot at the same time know both these quantities exactly.

Unfortunately, there is no way around this.

Heisenberg showed in his mathematics

that this is in an inescapable feature of reality at this scale.

OK, so what has all this quantum weirdness

got to do with nothing?

Well, you see, Heisenberg's Uncertainty Principle can be expressed in a different way,

in terms of a balance between two other quantities - energy and time.

Now, this is going to sound quite complicated,

but it's very important, so I'm going to try and explain.

You see, if I were to examine

a small volume of empty space inside this box, then I could

in principle know how much energy it contains very precisely.

But, if I were able to slow time down,

things would start to get very strange.

OK, so we are now looking at a tiny interval of time that has been stretched out.

Heisenberg's uncertainty principle

tells us that because I'm looking at a smaller interval of time,

I've lost precise information about the exact energy in the box.

If I could examine an even smaller interval of time,

and an even smaller volume inside the box,

then Heisenberg's equation suggests something truly bizarre could happen.

I will be so uncertain about how much energy there is in that part of the box,

that there is a chance it could contain

enough energy to create particles literally out of nowhere...

..provided that somehow they went away again very quickly.

Heisenberg's uncertainty principle seemed to suggest that

in truly tiny amounts of time and space, something could come from nothing.

But then what? If particles could pop into existence, where do they go?

Why don't we see these particles appearing all around us?

The vacuum, contrary to what one normally expects from the vacuum,

is alive.

It's alive with what physicists call quantum fluctuations.

In the vacuum, little packets of energy appear and disappear

very, very quickly.

This is perfectly allowed by the laws of physics.

It's all allowed but it has an name,

it is called Heisenberg's uncertainty principle,

which tells us that you can

borrow energy from nothing, so long as you pay it back quickly enough.

The vacuum is alive.

Bizarre though these ideas seem, they are, I promise you, fundamental to our universe.

To see how this can be,

our story of nothing takes us to one of the most

gifted and oddest characters in the whole history of physics.

Behind me is Bishop Road Primary School in Bristol

and almost 100 years ago,

it was attended by two students who were destined for greatness.

One of them, Archibald Leach, would go on to conquer Hollywood,

becoming better known as Cary Grant.

The other was a quiet, shy and rather intense boy two years younger than Grant,

who would become one of the greatest scientists Britain has ever produced,

the theoretical physicist Paul Dirac.

Even by the standards of theoretical physicists,

Dirac was a very queer bird.

He was not someone you'd go for a beer with.

Intensely focused,

man of extremely few words, very, very little empathy

and someone of rectilinear thought.

These personality traits were key to Dirac's genius,

but they often resulted in difficult or awkward

social situations with his peers.

Even in casual conversation, Dirac would never speak unnecessarily.

He'd often leave these long pauses in between sentences while

he worked out the most precise and concise way of expressing himself.

Friends had jokingly coined the term a Dirac, which stands for

the smallest number of words it is possible to speak in one hour,

while still taking part in a conversation.

It is a sort of unit of shyness.

Dirac's unusual personality had its roots

in a difficult and troubled childhood.

But from a young age, he had found solace in the classroom.

In particular, he excelled at both mathematics and technical drawing.

This was something that cultivated his visual imagination.

In maths classes, he was looking at mathematical symbols.

He was looking at similar things, but in a geometric way in his technical drawing class.

It is very, very suggestive of the way he looked at physics later on

because he always stressed that he was pre-eminently a visualiser.

He was someone who had a geometric look at physics.

He was not interested per say in mathematical symbols.

Rather he wanted a visual sense of what was going on in the mathematics.

Dirac continued his visual training, doing a degree in engineering

before go to Cambridge to study mathematics.

It would be here that Dirac would begin to unravel the deepest mysteries of the vacuum

and uncover what was really going on in empty space.

But his insight sprang from a seemingly unrelated difficulty.

By 1928, physics was struggling with a big problem.

The two most important theories

that described how the universe worked didn't agree with each other.

On the one hand, you had Einstein's special theory of relativity

encapsulated in the famous equation E=mc2.

It was a beautiful, simple and elegant theory

that describes the behaviour of things close to the speed of light.

On the other hand, you had Planck's discovery of the quantum

and the revolution that followed describing the bizarre rules of the very, very small.

The problems arose when trying to describe situations where things were small enough

for quantum effects to be felt,

but travelling fast enough for special relativity to be important.

Specifically, there were huge problems trying to describe

the electron, a tiny particle whizzing around inside an atom.

If both of these theories were true, then they should be able to be used

together to give a mathematical description of the electron.

But what if this couldn't be done?

What if quantum physics and special relativity couldn't be married?

This would mean one or other of these two cornerstones of physics had to be wrong.

A way had to be found for the two theories to be married together.

It would be Dirac who would achieve this.

Dirac's unification of the special theory and the rules of the quantum world

would rank as one of the greatest mathematical accomplishments of the 20th century.

And it would lead inadvertently to a radical new picture of nothing.

To get a non mathematical sense of what he did, and how he did it,

I've come to the cinema to see one of Dirac's favourite films, 2001 A Space Odyssey.

Understanding why it appealed to him

helps give us an insight into how he managed to solve this great problem.

If you look at 2001, it was, as Kubrick has said, a demonstration

that you could make a really good movie script without words

but with a power of the visual imagery.

Now, that in some ways is very closely analogous

to Dirac's a theoretical physics

because, for him, what was central, were the mathematical equations.

And more over, he had a visual sense of what those equations meant.

The abstract images of 2001 appealed to Dirac

because they captivated his brilliant visual imagination.

It was this highly developed and unusual way of thinking,

honed in his schooldays, that would enable him in 1928

to visualise a unique way of describing the electron.

It was a description that finally managed to unite Einstein's

special theory of relativity and the weird world of quantum mechanics.

Today, it's known simply as the Dirac equation.

It may look like a small collection of symbols,

but to a mathematician this equation is profoundly beautiful.

A complex and symmetrical synthesis of mathematical ideas, expressed with stunning clarity.

This is the commemorative plaque at Bishop Road, Paul Dirac's primary school.

And on it, his famous equation.

Within these few symbols lie profound truths about the universe.

But don't be deceived by its apparent simplicity,

think of this equation as the tip of a giant mathematical iceberg.

Each of these terms relate to entire branches of mathematics

and the particular relationships between them.

Beneath this equation, are mathematical ideas that

have been developed and honed by many, many other great individuals.

If you think of a poem, you can think of it as the most supercharged

kind of language, the way you compress meaning

into a very, very brief area on the page.

Dirac was producing equations that had that kind of concision

and you can then unpack them,

just as you re-read a Shakespeare sonnet and see more and more in it, more and more elegance.

Same with the Dirac equation, you find an equation there

you can keep finding things that were not obvious on first reading.

In fact, Dirac once said that the equation was smarter than he was

because it actually gave more stuff out than he put into it.

There was one particularly odd thing the equation seemed to be saying to Dirac.

Something that would redefine the concept of empty space forever.

In his description of the electron, Dirac had been forced to use a collection of four equations

represented by the symbol gamma,

in order to make special relativity and quantum mechanics fit together.

But the need for four equations seemed strange.

To Dirac and other physicists in the 1920s, the first two were quite recognisable.

They described the behaviour of an electron as it had been observed in the laboratory.

But the second two were very strange.

They seemed to be saying there was some other type of electron that could exist.

One that had never been seen before.

So, this is the normal world we are familiar with.

And here, scaled up many, many times

is a regular electron of the type contained within

the trillions of atoms that make up this table,

me and everything else in the universe.

Dirac realised that these mysterious new elements in his equation

predicted the existence of a strange new kind of particle.

In some ways, just like the electron, and yet at the same time very, very different.

Dirac gradually became convinced that the new parts of his equation

were describing something

that could be thought of as an anti-electron.

In many ways, it was like the mirror image of an electron,

having opposite properties like electric charge.

And, in principle an anti-electron could form part of an anti-atom,

and many anti-atoms could fit together

to make an anti-matter table, or even an anti-me.

But the weirdness didn't end there.

Dirac realised that if things and anti-things ever met each other,

they would instantly annihilate,

turning all their mass into energy...

EXPLOSION

Disappearing completely.

Here, finally was the answer to the riddle of empty space.

Heisenberg's uncertainty principle had suggested that matter could

pop into existence for incredibly short periods of time.

Now, Dirac had provided the mechanism

by which matter could be created out of the vacuum...

..and just as quickly, disappear again.

So, let's take another look at our box.

Whenever a particle pops out of empty space,

so simultaneously does its anti-particle.

Although this sounds completely ridiculous, let me assure you it is true.

So, whenever you try to remove everything you can from empty space,

it's still always awash with all these fluctuations.

Within nothingness, there's a kind of fizzing, a dynamic dance

as pairs of particles and anti-particles

borrow energy from the vacuum for brief moments

before annihilating and paying it back again.

Dirac's theory of the electron and the idea of anti-matter

gives us a completely new picture of the vacuum.

Before you could think about the vacuum as empty space, so to speak.

relativity had said, you don't need an aether,

so the picture was of the vacuum being empty.

But when you bring relativity and quantum theory together

then you have for certain, this notion of electron and anti-electron pairs

just appearing out of the vacuum.

So you can think of these pairs just sprouting all over the place in the vacuum.

So, the vacuum goes from being nothing

to being a place absolutely teeming with matter, anti-matter creation.

Dirac's ideas about empty space were refined and developed

into what is known today as quantum field theory.

And these strange fleeting things within nothing

became known as virtual particles.

So it seems, nothingness is in fact a seething mass of virtual particles,

appearing and disappearing

trillions of times in the blink of an eye.

I've come to Imperial College London

to see the effects of these virtual particles myself.

Thanks to a brilliant experiment by an American scientist called Willis Lamb,

we now have a way to conclusively show

there is activity within apparent nothingness.

But in order to glimpse it,

you have to peer deep within a single atom

and amazingly Lamb found an ingenious way to do this.

So, what did Lamb do?

Well, his experiment relies on the quantum rules of the atom.

Within atoms, electrons have very specific, discreet energies

in the way they orbit around the nucleus.

His experiment showed that if the vacuum really was full

of these hidden fluctuations,

then these would cause the electrons' orbit

to wobble ever-so-slightly.

Think of it as an analogy as though the electron is a plane

flying along and hitting turbulence

forcing it to move up to a slightly higher altitude.

So this is how the experiment works.

Contained within this vacuum chamber are a small number of atoms.

While Lamb used microwaves in his original experiments,

in this version, the team at Imperial are using lasers to probe the electrons.

Now, if you think this all looks very complex, just remember

how small a measurement it is we are trying to make here.

This apparatus has to be sensitive enough to pick up minute changes

in the behaviour of something that is itself, extremely tiny.

Imagine we could scale up the wobble in electron that's being measured

to the size of this apple.

That would mean this vacuum chamber behind me, would scale up to being a trillion miles in size.

The vacuum chamber would be something like

100 times the size of the entire solar system.

It would take light about 40 days just to travel from the top down to the bottom.

So, what is going on in there?

OK, so let me first fire up the laser in the experiment behind me.

What this monitor will show us is exactly what's going on inside the vacuum chamber

down at the minutest scales.

Now, look at this peak that's appeared.

BUZZING

It may not look very exciting,

but it's telling us something really remarkable.

This is measuring the amount the electron is being wobbled about by the vacuum itself.

If the vacuum were truly empty, this peak wouldn't exist,

we'd just get a flat line.

What this is telling us is that however hard we try

to remove everything we can from space, we can never get it truly empty.

Everywhere in the universe, space is filled with this vacuum

that has a deep, mysterious energy.

But it doesn't end there.

When using the mathematics laid out by Heisenberg, Dirac and others,

you can calculate the amount the electron should be affected.

When you run the real physical experiment, the answer you get

matches the theory to one part in a million.

The theory of quantum mechanics is the most accurate

and powerful description of the natural world that we have.

But there's a much more dramatic way

in which we can see the effects of these quantum fluctuations.

And that's because they're written into the stars.

Today, our best theories tell us

that as the universe sprang from the vacuum, it expanded very rapidly.

And this means that the rules of the quantum world should have

contributed to the large-scale structure of the entire cosmos.

When our universe first came into existence, it was many times smaller than a single atom.

And down at this size it's governed not by the classical rules we're

familiar with, but by the weird rules of the quantum world.

This is for me, one of the most profound and beautiful ideas in the whole of science.

That it's quantum reality that has

shaped the structure of the universe we see today.

Our universe is just the quantum world inflated many, many times.

Nothing really has shaped everything.

And what's more, we now have a way to see this.

This is a picture of the first light that was released after the Big Bang.

Think of it as a baby photo of everything.

This incredible picture was taken by a team of researchers at NASA

led by Professor George Smoot.

This is like taking a

picture of an embryo that's 12 hours after conception,

compared to taking a picture

of a person who is 50 years old.

It's in the same perspective.

And 12 hours, you may have two cells, this is very early and yet we are seeing what's equivalent

of the DNA, the blueprint for how the universe is going to develop.

With the help of highly sensitive satellites,

George Smoot and his team were able to study this image

of the embryonic universe in amazing detail.

And when they did, tiny variations in its temperature were revealed.

It soon became apparent that the tiny differences in temperature

are in fact the scars left by the quantum vacuum on our universe.

EXPLOSION

These irregularities created in the first moments of existence

by the teeming quantum vacuum meant the matter of the universe

didn't spread out completely evenly.

EXPLOSION

Rather, it formed vast clumps that would evolve into

the galaxies and clusters of galaxies that make up the universe today.

The application of quantum physics to cosmology,

to the universe as a whole

was revolutionary.

It really changed our entire perception

of the evolution of the universe,

because it turns out that quantum physics provides a natural mechanism

through quantum fluctuations

to see into the early universe with small irregularities that would later grow to make galaxies.

The thought is really overwhelming, the idea that an object

with billions of stars like the Milky Way began life as a quantum fluctuation,

what we call a fluctuation of the vacuum,

an object of sub-microscopic scales, it really is mind boggling.

It now appears as if the quantum world, the place we once thought of

as empty nothingness has actually shaped everything we see around us.

What happens is, something that was a small fluctuation,

a tiny quantum fluctuation, becomes our galaxy.

Or becomes a cluster of galaxies because there are lots of quantum fluctuations,

so it answers one of the questions we have -

why are there 100 billion galaxies in our viewpoint?

Well, in a drop of water,

there's many more than 100 million quantum fluctuations,

in an atom there's that many, the vacuum has all of this bubbling going on all the time.

The teeming, seething activity of the vacuum, of nothing,

and the quantum fluctuations within it...

..were the seeds, seeds which grew into the universe we see today.

This idea gives rise to one final revelation.

Today, our best theories about the cosmos tell us

that at the beginning of time, the universe sprang from the vacuum.

Creating not only vast amounts of matter, but also the strange stuff

that was predicted by Paul Dirac...

..anti-matter.

But the universe we see today is made of matter,

nearly all of the anti-matter seems to have vanished.

EXPLOSION

According to common theory,

the Big Bang produced equal amounts of matter and anti-matter.

But as the universe cooled down,

matter and anti-matter annihilated almost perfectly, but not quite.

For every billion particles of matter and anti-matter,

one was left behind.

The matter and anti-matter that annihilated to produce radiation

gave rise to the heat of the Big Bang

that we see today in the form of the microwave background radiation.

The little particle that was left behind, for every billion

that annihilated is what makes galaxies, stars, planets and people.

So, we are simply the debris of a huge annihilation

of matter and anti-matter at the beginning of time.

EXPLOSION

The leftovers of an unimaginable explosion.

All these insights have arisen

from simply trying to understand what nothing really is.

What we once thought of as the void

now seems to hold within it,

the deepest mysteries of the entire universe.

In the 400 years or so since Torricelli and Pascal

began exploring vacuums here on Earth,

we've begun to understand in ever greater detail the world's at the very limits of our perception.

And in doing so, we've uncovered the strange truth about reality itself.

There's a profound connection between the nothingness

from which we originated

and the infinite in which we are engulfed.

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