There's a force of nature that's baffled the most famous names in the history of science.
Galileo laid the foundations but didn't get any further.
Newton thought it was the work of God.
And even Einstein, Albert Einstein failed to solve it.
It's a mystery that lies at the heart of everything...
..from the Big Bang and the beginning of time...
..to the existence of life on Earth.
From strange distortions in the cosmos
to the smallest stuff of matter.
It's a puzzle that's led to the most abusive slanging matches in modern science.
But I think that within my lifetime
we may succeed where many of the greatest brains in history failed,
and finally solve one of the biggest mysteries of the universe.
I'm Brian Cox,
particle physicist.
I have one of the best jobs in the world.
I have to find out what are the fundamental building blocks of the universe.
How do they stick together, how do they work and, with a bit of luck, find out why they're there at all.
I've spent the last ten years looking at the smallest stuff in the universe.
But I'm interested in the biggest questions you could possibly ask.
Why do I exist? Why do you exist?
Why is the Earth the way it is? Why is the universe the way it is?
Why is the universe built in a way that life can exist at all?
At the root of all these questions lies a force of nature
that surrounds us, penetrates us and binds the galaxy together.
The key to a much deeper understanding
of the universe, and even our place within it, is gravity.
It was gravity that made our sun ignite five billion years ago.
Without gravity there'd be no planets,
no stars,
no galaxies,
nothing.
If we want to know why the universe is built the way it is,
we need a complete understanding of this elusive force.
But there's something missing in our understanding of what gravity is and how gravity works.
Getting to the bottom of the problem has vexed scientists as far back as the Ancient Greeks.
But in the late 1600s, in a small village in Lincolnshire,
the question of gravity was tackled head on by one of the granddaddies of modern physics.
This is the home of Sir Isaac Newton.
Film about gravity - apple.
It's a cliche but the story goes that it was in this orchard that Newton was sat,
thinking about the universe, and an apple fell on Newton's head, and got him thinking about what it is
that makes the apple fall, what force pulls the apple towards the ground?
Newton suggested the apple falls because of a force of attraction
that naturally exists between the apple and the Earth.
It's this force that we know as gravity.
But Newton's real genius was not to just stop with the apple but to ask the question,
is the same force that causes the apple to fall here on Earth also responsible
for the movement of much bigger things out there in the cosmos?
Newton believed that gravity is a force that acts throughout the entire universe.
In 1686, he finally managed to break it down
into one single mathematical equation.
Newton's understanding of gravity is actually incredibly simple - that the force
between two objects depends on only two things, the mass of the objects and the distance they are apart.
So, the more massive the objects, the stronger the force,
and, the further the objects are apart, the weaker the force.
See, it's easy to show actually.
Got a pen?
So this is Newton's law of gravitation.
The force is equal to the masses of the two objects,
divided by the square of the distance apart of the objects.
And then there's Newton's gravitational constant, that just
sets the scale - it tells you the overall strength of gravity.
With one beautiful bit of maths, Newton had figured out gravity,
but not just here on Earth.
The Moon seemed to orbit the Earth exactly as he predicted,
as did the planets orbiting around the sun.
Newton believed we live in a universe in which ultimately
the movement of everything can be predicted.
Newton's universal law of gravitation is one of the most important turning points in physics,
and that's because it really is universal.
It allows you to predict not only how things move under the influence of gravity here on Earth
but how the stars and planets and even galaxies move, all the way across the universe.
ARCHIVE: Ignition sequence start.
Nearly 300 years after the falling apple...
..it was Newton's ability to predict how the Moon orbits the Earth
that allowed us to take a giant leap.
That's one small step for man,
one giant leap for mankind.
Newton's law of gravity was crucial in allowing us
to navigate from the Earth to the Moon.
But we now know Newton isn't entirely correct.
I've come to El Paso in Texas, right on the Mexican border.
I'm here to discover what's wrong with Newton.
Where are the keys?
Now we're all ready and now you're stopping us. Because it's funny!
We're heading off across America, to try and solve the mystery of gravity.
I think the most exciting thing that we'd ever done, as the human race, is to land on the Moon.
It happened just in my lifetime I was just over one year old when Armstrong and Aldrin touched down.
So I don't remember it, but what I remember is growing up with it.
Back in '69, Neil and Buzz left more than footprints behind.
They offloaded a special set of mirrors that could be used to test Newton's theory of gravity.
Those mirrors have played an important role
here at one of the last surviving outposts of the Apollo space mission.
This is the McDonald Observatory, four hours' drive from El Paso.
We've arranged to meet up with veteran Apollo scientist Peter Shelus.
This is one of the photographs which shows this reflector package.
This is a set of mirrors which are very specially constructed
so any incoming ray of light gets reflected exactly back.
The reflector on the Moon is really only about 18 inches square,
not very much larger than this photograph.
You can see some of the footprints.
You can see a sandwich bag left on the surface - I don't think that was anybody's lunch!
The mirrors left on the Moon allow Peter to make a very accurate measurement.
Using a telescope with a built-in laser, Peter can precisely measure
the distance from the Earth to the Moon.
We orient the telescope so that it is facing the Moon.
The laser light, coming out of the telescope, then goes directly up to the Moon.
It can be reflected by the reflector
and it then comes right back through the tube again,
makes its way through the optics and we sense it inside the building.
OK, there it is.
Look at that.
There's a really big crater, you can see the shadow in there.
'Timing how long it takes the laser beam to go out and bounce back,
'Peter can precisely calculate the distance to the Moon.
'But trying to hit that tiny mirror, so far away,
'requires very careful alignment and a bit of perseverance.'
We may send out a thousand million billion photons,
whereas coming back...coming back into the telescope might be ten.
Ten! Or five, or none!
So it is still a very hard experiment because everything has to work just right.
How accurately can you make that measurement, off Neil and Buzz's reflector and back again?
One to three centimetres. Over a quarter of a million miles.
Over a quarter of a million miles out, quarter of a million miles back.
By taking accurate measurements
of the distance between the Earth and the Moon,
day after day, year after year, for nearly four decades,
an incredibly precise map of the Moon's orbit has been produced.
But the results have thrown up something very odd.
The actual orbit of the Moon is different to that predicted by Newton.
It turns out that simple Newton's laws of gravity
really don't answer all of the questions.
For the data that existed, it was good.
Newton really had a good formula.
But, as we get better and better data,
If you use Newton's law of gravity to predict where the Moon should be,
then the Moon is in the wrong place.
Peter's results disagree with Newton's by about ten metres.
That may not sound much, but it means Newton got it wrong.
You've got to explain your observations.
And Newton's gravitational theory just doesn't do it any more.
The observations are so accurate that we need something else.
This is an amazing result.
We've relied on Newton for 300 years -
his equations certainly appear to work really well.
Yet it seems that there's more to gravity than Newton realised.
Newton's understanding of gravity was good enough to allow us to fly from the Earth
to the Moon, to cross a quarter of a million miles of space
to land on the Moon and then fly all the way back again.
But it's kind of got to make you laugh to think that you can go all the way to the Moon and back
using something that's ultimately just an approximation.
To find out what on Earth is wrong with gravity, we need to go beyond Newton.
The problem lies not so much in what he understood but in what he failed to address altogether.
# Gravity
# Is working against me... #
There's a problem with Newton's theory of gravity,
and that's that it just allows us to predict how things move under its influence.
It doesn't say anything about why gravity exists or even how it works.
It just allows you to calculate things. Newton knew this, of course.
He essentially just said that it's down to God.
In fact, he said that the most beautiful system of the sun, the planets and the comets
could only proceed under the dominion and counsel of an intelligent being.
In other words, I'll give you the tools to calculate how the objects move around
but don't ask me how or why that is, that's down to God.
To solve this fundamental flaw, we've got to take gravity out of the hands of the divine.
We've got to discover for ourselves how gravity works.
But our journey has only just begun.
We've still got a long way ahead of us.
Set out at three o'clock, we did it by four, we'd only lost two men.
It's not about giving information any more, it's about them feeling the journey.
That's brilliant! Driving across the desert to do physics!
Our quest has brought us to Kitt Peak, about 80 kilometres west of Tucson in southern Arizona.
Since the first telescope was built here back in the 1950s,
this mountaintop has witnessed some of the most important discoveries in cosmology.
Kitt Peak's one of the most famous observatories in the world.
It's the place where, about 30 years ago now,
something very strange was observed about the fabric of the cosmos.
We've come here to see a little piece of the night sky, 7.8 billion light years from Earth.
That little piece of sky has given us a glimpse into the inner workings of gravity.
But outside the weather's not good.
They're not opening the telescopes tonight.
But here's what they saw all those years ago.
Astronomers were looking into the sky to find
distant galaxies, billions of light years away.
And they found this.
At first sight it looks like two different galaxies.
In fact, they gave them different names, 957 and 561.
But when they looked more closely they found that they look identical in every way.
It's incredibly strange. It's almost like there are two twin galaxies,
The interpretation is, this is a picture of one single galaxy.
This certainly confused the astronomers,
but they soon realised that the cause of this strange cosmic mirage
had been predicted nearly a hundred years ago.
There's one man who, for me, really did think outside the box.
He was the first celebrity scientist,
hailed by many as the greatest physicist of all time.
At the turn of the 20th century it was Albert Einstein
who opened our minds to a completely new way of looking at the universe.
Einstein's universe is made of something called space time.
Now, space is what we see around us - it's got length and breadth and height.
And time...well, it just ticks along.
But in Einstein's universe they're woven together into a fabric.
Space and time are not separate, they're one and the same thing.
And that fabric is called spacetime.
This strange idea of spacetime is certainly radical.
In one sweeping action, Einstein's theory of relativity
completely changed our picture of the universe.
Newton's universe was kind of a stage, an arena in which everything happens.
It was like a box, exactly as you'd imagine it, and the stars
and the planets and us are just going about our business inside the box.
Now, Einstein's genius was to realise that you don't need a box, there's just spacetime.
And everything that happens in the universe affects the spacetime,
and the spacetime affects everything that happen in the universe.
In Newton's universe there's just empty space.
The stars and galaxies have an effect on each other,
but that's it.
Einstein's universe is completely different,
it has an internal fabric, the spacetime.
The celestial bodies are all embedded within this fabric, and they all interact with it.
In Einstein's universe, the planets, stars and galaxies actually warp,
bend and distort the spacetime.
It's this interaction of matter with the fabric of the cosmos
that helps explain the weird sightings on Kitt Peak.
That image of duplicate galaxies can be explained by the bending of spacetime.
What's happening is that light from a distant galaxy
is passing by a galaxy or even cluster of galaxies on the way to the Earth.
Now, in that cluster there could be millions or tens of billions of stars,
huge amount of mass, which bends and curves the space.
So the light from the distant galaxy curves around the cluster.
And from our perspective on Earth this bending action
causes us to see multiple images of the distant galaxy.
This explanation has far wider-reaching implications
than simply describing strange astronomical oddities.
It lies at the very heart of Einstein's understanding of gravity.
Einstein believes that it's this bending of spacetime that actually explains gravity's existence.
Einstein didn't see gravity as Newton did,
as a kind of force of attraction between two bodies, a star and planet, for example.
He sees gravity as a result of space and time, of spacetime, being bent.
Einstein says that our planet is distorting the spacetime.
And it's this curving of the fabric of the universe that creates the effect we feel as gravity.
The bigger the mass, or the nearer you are to an object, the more curved
the spacetime becomes, and so the stronger is the effect of gravity.
It sounds impossible to prove, yet the fact that spacetime is distorted by the Earth
is something many of us have to contend with every day,
whether we know it or not.
Einstein's understanding of gravity is crucial for the correct working
of one of the most useful innovations of the 20th century.
SATNAV: Select destination.
It's the gadget that's revolutionised how we get around.
It's what we've relied on to navigate across America.
SATNAV: Calculating route.
It's the global positioning system, or GPS.
Right turn in 4.9 miles.
We're heading to GPS headquarters, just south of Denver, Colorado,
but we're running a bit late.
'Approaching U-turn.'
What were you using, a GPS satellite navigation system?
Where were you going? GPS headquarters.
Did you get there on time?
No, we got lost!
in Colorado Springs.
It's a maximum security military installation.
base without a runway.
It's the home of the global positioning system.
Half an hour late and we're quickly taken under the wing of Major Bandit Brant.
Gentlemen. Yes, sir.
Well, welcome to the second space operations squadron, give you a tour as we walk down through here.
It's from this one room that the whole GPS network is controlled.
Running the floor today is Captain Chris Maddocks.
You must have the biggest impact
of any military crew in the world on ordinary people.
Typically, civilian users aren't really our first thought, because I'm a war fighter.
We think bombs on targets, planes landing safely.
Soldiers not getting lost in the desert.
But secondary to that, we do think there are people using what is it, Sam Sam or Tom Tom?
Tom Tom. Tom Tom. All these users have the ability to get from point A to point B because of what we do.
The global positioning system works by using a fleet of satellites orbiting the Earth.
It's these satellites that are ultimately controlled by the American military.
How many satellites are up there?
We have 31 satellites up in the constellation. Minimum is 24 satellites.
So, you can afford to lose seven of them?
Hopefully not. On your watch, particularly. Hopefully not.
For the controllers of the GPS, time is everything.
'US naval observatory master clock,
'at the tone, mountain daylight time, 18 hours, 48 minutes, five seconds...'
For the global positioning system to work,
the clocks on board the satellites
have to be exactly synchronised with time on Earth.
But for the satellites, orbiting 18,000 kilometres above our planet,
Einstein predicts something very strange.
He predicts that in orbit,
time itself runs at a different speed to that on the Earth's surface.
It's incredible for anyone to suggest that time goes at a different rate on the ground
than it does in space.
What's the difference?
Well, the difference is gravity,
the closer you are to the Earth, the stronger the gravitational field
the further you are up into space the weaker the gravitational field.
What Einstein said was that the stronger the gravitational field, the slower time ticks.
The weaker it is, the faster time ticks.
The link between the speed of time and the strength of gravity
is all down to Einstein's prediction that the Earth distorts the space time.
If you put something heavy in space like a planet, a star, the Earth,
then that heavy thing bends the space, it curves the space.
But space and time are intimately linked.
So, does the Earth also bend time?
Well, yes, it does.
In the reduced gravity up in orbit,
time really does tick a bit faster than time on Earth.
To keep everything in sync,
the controllers have to dial-in a time correction.
Pretest 35. Check this one, SA step two, go. Step forward, it's a good order, no windows.
Step 6 updating on the B string avtech one's come up and comms good.
You have good visibility and ascension till 21:52,
and good alt viz at Diego, no open jobs.
You've got to allow for the fact that time runs at a different rate on the ground than it does in orbit,
if you don't, then your GPS system will drift, not by a few centimetres,
as you might think, but by ten, 11, 12 kilometres a day.
This morning we got lost. It didn't work, can you believe that
And then it took us into a field about a mile away.
Our response to that is the constellation is healthy
and producing an accurate navigation signal.
What you mean is you're an idiot!
With that, it was time to leave.
'Calculating route.'
'Approaching U-turn.'
You got it wrong, again!
The fact that GPS operates in the way it does,
shows that Einstein's idea of bending space time
is an accurate description of how gravity works here on Earth.
But Einstein's understanding of gravity is not complete,
something is missing.
It may hold true for the Earth and the other planets even for the movement of galaxies
but Einstein knew that his theory of gravity doesn't apply to the whole universe.
It fails to work in the most violent and turbulent places in the cosmos.
But if we want a complete picture of the universe
we must know how gravity behaves everywhere.
We've come to America's Deep South, not far from New Orleans.
These are the famous bayou swamplands of Louisiana.
It's out here
that scientists are trying to peer deep into the darkest and most brutal corners of the universe.
Louisiana's one of those places that you always think of as being...
well, laden with black magic and things,
certainly not a rational exploration of the universe.
In these alligator-infested backwoods,
the final piece in the puzzle of Einstein's universe is being put to the test.
This place stands at the leading edge of the exploration of gravity.
Joe Giami is the head man.
Gravity will probably and hopefully confuse us for a long time
before we figure out what it really is,
and scientists are happy when confused and chasing something fun.
Rising out of the swamp in the shape of a giant L,
this is the Laser Interferometer Gravitational Wave Observatory
or LIGO, for short.
Any signal we see is gonna be from something really, really interesting and cool.
Data from those sources would be valuable
to learn things about gravity and it's nature.
This machine was built as an observatory,
a chance to witness violent galactic events
beyond anything we've ever seen before.
One of the things I hope to see is when you get two stars called neutron stars.
A neutron star is probably twice or three times as heavy as the sun,
but compressed into a ball about ten kilometres across, so the size of a city.
And there are places where there can be two of those things
orbiting around each other at about 100 or even 1,000 times a second.
The incredibly dense neutron stars spin round each other,
churning up the space time.
As they spiral in, going faster and faster,
Einstein predicts this sort of violent cosmic event
will create something called gravitational waves.
But what exactly is a gravitational wave?
It's not that easy to describe.
If a wave came through this room it'd...what can I say?
Eh...ripples, yeah.
Space time isn't just something that's...
you know up there amongst the stars, it's here.
It's in front of me, and it's inside me.
So, when I move, I disturb it - I send out ripples in it.
It's just like if I jump into a swimming pool and start swimming.
I'll send out ripples on the surface of the water.
It's the same with space time.
In theory, these waves would cause space and time to stretch and shrink
as they pass through the universe.
These waves are physical distortions in our reality.
They really are stretching and contracting the space and the time that we're in.
But trying to see these gravitational waves
using the LIGO machine is proving very difficult.
Gravity waves cause links to change in one direction differently than the other direction.
If I were very stretchy,
and a gravitational wave was going through me,
I would get shorter one way, and longer the other way.
The machine works by using a laser beam
to measure the distance between two sets of mirrors
suspended at the ends of the two 4km long tubes.
From here you can see all the key components.
Running off to the right there and also running down under our feet
are tubes that carry the light to the end stations.
There's a mirror here and one 4km that way.
When the gravity wave comes through the distance between those mirrors changes.
They're basically just fancy rulers. That's right.
But even after five years in continuous operation,
the team hasn't been able to observe any violent gravitational hotspots.
This is because they still haven't detected Einstein's elusive gravitational waves.
This is one piece of nature we haven't really observed right yet,
to see gravitational waves, whether they really affect things here the way we think they do.
We don't know where the sources are that we're looking for,
so we have to look farther and farther out until we catch one.
In the most extreme places in the universe,
Einstein is still on dodgy ground.
As we travel deeper into space and time
we're beginning to realise that Einstein's universe may unravel.
But to know the cosmos, we need to know how gravity works everywhere.
In the most sinister of cosmic phenomena,
in the dark heart of a black hole,
Einstein has no answers.
And his idea of gravity completely fails
in the most violent event in history.
At the Big Bang, the origin of everything,
the universe was incredibly hot,
incredibly dense and incredibly small.
All matter was condensed into a space smaller than a single atom.
And here lies the problem.
Much as he tried,
Einstein never managed to answer the question of how gravity works
when things get very small.
Einstein gave us a beautiful theory of gravity,
it tells you how planets orbit around stars,
it tells you how galaxies orbit around each other,
it tells you how the universe evolved.
But Einstein himself knew that there was a problem,
right at the heart of the theory.
Einstein's theory of gravity doesn't work at all
if you come into the world of the small,
so the sub-atomic particles that make up my body.
Einstein's theory has nothing to say at all about gravity
in the realm of the atoms and molecules
and sub-atomic particles that make up the world.
This is Einstein's greatest failure.
His calculations just come up "error".
At the smallest scale, his whole theory simply falls apart.
But we have to know how gravity works at the smallest distances
if we want to know how it all began.
Einstein's theory of relativity just can't provide the answer.
The maths just doesn't work on the smallest distance scales.
So the answers probably won't lie up there in the realm of the galaxies,
but in here - in the world of the atom, the stuff of matter.
This is the world of quantum mechanics,
which is what I do for a living.
It's in quantum theory that we hope to find the answers
that Einstein searched for
to understand how gravity behaved at the very beginning of time.
If we can figure out how gravity works at the level of the smallest sub-atomic particles,
then maybe we can finish what Newton and Einstein started,
and form a complete picture of this mysterious force of gravity.
To achieve this goal,
we have to try to recreate the conditions of the Big Bang here on Earth,
and peer deep into the heart of the sub-atomic world.
'This place is Fermilab, and I used to work here.
It's home to the Tevatron particle accelerator.
and seeing what comes out.
What we do is we take protons, and we accelerate them around that way,
and anti-matter protons, send them around that way,
and they pass by here 50,000 times a second,
very close to the speed of light,
and then we collide them together, we smash them together.
It's though collisions like these that the nature of matter has been revealed.
But the force of gravity still sits outside what we know.
One of the ways we might get to the truth about gravity
is to try and fit it into the beautiful framework we have
that describes the sub-atomic world.
Quantum mechanics predicts that the force of gravity should be transmitted by a particle.
We call this particle the graviton.
If we could just find these gravitons,
then we might at last arrive at a quantum theory of gravity,
a universal theory that will work everywhere in the cosmos.
For eight years,
Greg Landsberg has been using Fermilab's particle accelerator
to try to create gravitons.
These particles, though we haven't quite seen them,
so what I'm telling you is...
Haven't quite seen them?! That's right. It's our hypothesis,
so we don't quite know if this is true.
on gravitons to see them,
so we have to find some other means.
It's amazing that the way to see the graviton is by NOT observing it,
by observing it's missing.
To see something that's missing,
Greg is effectively looking for missing energy.
Typically, when you bash things together,
the energy of the original particles should be the same
as the total energy of all the particles coming out.
But if you were to make a graviton in that collision,
then our detectors are certainly not capable of seeing it,
so the graviton will take energy away from the collision.
Energy will appear to disappear.
So, the old control room. I haven't been here for years!
So what this picture tells us... it's called event display.
The height of these bars is how much energy is released in this collision
in that particular direction.
There's a collision in the middle, and the stuff's spraying out.
What we're trying to do is to sum all this energy,
to see if something is missing.
If you look at this display,
you see a lot of energy going in this direction,
but very little on the other side, and this yellow bar,
in fact, represents the fraction of energy which is missing.
So if you see that, that means that something escaped. That's right.
If gravitons ARE created,
Greg believes the reason why they would disappear
is because they vanish into a place beyond our reality,
into some sort of extra dimension.
Now, we're all familiar with the three dimensions of our world,
you know, there's up and down and north and south and east and west.
But what scientists like Greg are proposing
is that there can be extra hidden, unseen dimensions.
It sounds ridiculous, and it IS impossible to picture,
but theoretically, it's possible,
and it's also possible that gravitons, the particles of gravity,
can spend most of their time in those extra dimensions.
If gravitons really are created,
and they escape in these extra dimensions, you would never see them.
So although it might sound like a very odd hypothesis and odd concept,
really, nothing prevents us of thinking in this direction,
especially if we can solve these mysteries.
The graviton may really be the final piece in the puzzle.
Newton could predict the effects of gravity.
Einstein worked out why it exists.
But by finding a graviton, we might at last truly understand gravity.
Does Greg stand any chance of finding his graviton?
You know, it's still just possible.
When this machine started up, it was very possible,
but it seems now that probably the Tevatron is just too small to do it.
So we're gonna all move, I mean myself, Greg,
and pretty much everyone that works here,
certainly in a couple of years,
we're gonna all move to Geneva where we've built one of these machines,
but a lot bigger, and then the search will continue.
We now know exactly where we stand
in our quest for a complete explanation of gravity.
The solution to a deeper understanding of gravity
will certainly lie in the world of the small, the quantum world.
It's in the marriage of Einstein's theory of gravity with the quantum theories of sub-atomic particles.
But nobody has any idea just how long this might take.
We could see something, a particle accelerator, tomorrow,
that shows us the way to our quantum theory of gravity.
Or some Einstein, some Newton, some Galileo, some Da Vinci
could just appear on the scene and simplify everything.
Understanding how gravity works everywhere in the cosmos,
and crucially, at the beginning of time,
will bring us ever closer to a theory of everything.
Knowing gravity will mean that we can better understand
why the universe is built the way it is,
and that's surely the biggest question you can ask.
But the journey that lies ahead is not going to be easy.
If there are things that I listen to,
you listen to, that you think, "Well, I don't understand that",
then you're in good company, because nobody understands it.
You dig deeper and it gets more and more complicated,
and you get confused,
and it's tricky, and it's hard, right, it's hard,
but it's beautiful.
# The laws of gravity are very, very strict
# And you're just bending them for your own benefit...#