Imagine you could find an explanation for everything in the Universe,
from the smallest events possible to the biggest.
This is the dream which has captivated the most brilliant scientists
since Einstein.
Now they think they may have found it.
The theory is breathtaking
and it has an extraordinary conclusion:
that the Universe we live in is not the only one.
There could be an infinite number of universes
each with a different law of physics.
Our universe could be just one bubble
floating in an ocean of other bubbles.
Everything you're about to hear is true.
At least, in this universe it is.
For almost a hundred years science has been haunted by a dark secret:
that there might be mysterious hidden worlds beyond our human senses.
Mystics had long claimed there were such places.
They were, they said, full of ghosts and spirits.
The last thing science wanted was to be associated with such superstition,
but ever since the 1920s
physicists have been trying to make sense of an uncomfortable discovery.
When they tried to pinpoint the exact location of atomic particles like electrons
they found it was utterly impossible.
They had no single location.
When one studies the properties of atoms one found that the reality is far stranger
than anybody would have invented in the form of fiction.
Particles really do have the possibility of, in some sense,
being in more than one place at one time.
The only explanation which anyone could come up with
is that the particles don't just exist in our Universe.
They flit into existence in other universes, too
and there are an infinite number of these parallel universes,
all of them slightly different.
In effect, there's a parallel universe
in which Napoleon won the Battle of Waterloo.
In another the British Empire held on to its American colony.
In one you were never born.
Essentially anything that can happen does happen in one of the alternatives
which means that superimposed on top of the Universe that we know of
is an alternative universe where Al Gore is President and Elvis Presley is still alive.
This idea was so uncomfortable that for decades scientists dismissed it,
but in time parallel universes would make a spectacular comeback.
On the ice rink I am communing with the fundamental laws of physics.
At the instant of creation we believe that the Universe was symmetrical,
it was pure, it was elegant.
Without friction Newtonian laws are laid bare,
simple, elegant and beautiful,
pure, noble, elemental, just like it was at the beginning of time.
When I was a child of eight my elementary school teacher came in the room
and announced that a great scientist had just died
and on the evening news that night, everyone was flashing pictures of his desk
with the unfinished manuscript of his greatest work.
I wanted to know what was in that manuscript.
Years later I found out that it was the attempt of Albert Einstein
to create a Theory of Everything, a theory of the Universe
and I wanted to be part of that quest.
Einstein never achieved his goal of a Theory of Everything,
but again and again others have thought they were on the brink of this ultimate achievement.
This was always wishful thinking
until recently.
A revolution occurred in the 1980s.
In universities across the world new ideas in science streamed forth.
Finally, it seemed, everything in the Universe was about to be explained.
In Britain the famous physicist Stephen Hawking,
was even so confident he claimed physics was ready to read the mind of God.
There would soon be no big scientific problems left.
One idea was the most revolutionary of all.
It seemed a sure fire Theory of Everything
and captured the imagination of scientists like Burt Ovrut.
It was all to do with string.
It has been thought since Physics began that matter was made up of particles.
We had changed that point of view now. We now think that matter is made up of little strings.
For years it had been an article of faith
that all the matter in the Universe was made of tiny, invisible particles.
Now suddenly the particle physicists discovered they'd been studying the wrong thing.
The particles were really tiny, invisible strings.
The theory was called String Theory
and it maintained that matter emanated from these tiny strings like music.
You can think of it as a violin string or a guitar string.
If you pluck it in a certain way you get a certain frequency,
but if you pluck it a different way you can get more frequencies on this string
and in fact you have different notes.
Nature is made of all the little notes, the musical notes,
that are played on these super-strings.
All of a sudden we realised the Universe is a symphony
and the laws of physics are harmonies of a super-string.
But if String Theory was to become Einstein's missing Theory of Everything
it would have to pass one test.
It would have to explain a rather special event:
the birth of the Universe.
The origins of the Universe had always been the special subject of the cosmologists
who studied the big world of stars and galaxies.
They, too, felt they were on the verge of a great triumph,
a complete understanding of how the world had begun.
They'd long known things had started with a giant explosion - the Big Bang.
But by now cosmologists had refined the idea.
They had worked backwards in time from the present day,
closer and closer to the instant of the Big Bang.
Their work was incredibly precise.
We have confidence in extrapolating back from the present
to when the first stars and galaxies formed and the Universe was only a billion years old,
or extrapolating back farther to when the first atoms were formed,
when the Universe was a few hundred thousand years old,
or when the first nuclei formed when the Universe was only a few seconds old.
Physics was now actually ready to talk about these bizarre sounding events in the Universe,
fractions of a second and even billionths and billionths and billionths of a second,
10-35 seconds after the instant of the Big Bang. Absolutely fantastic.
If everything in the Universe was to be explained
then String Theory and the Big Bang would now seamlessly merge
and they'd complement each other perfectly.
After all, one concerned the birth of the Universe
and the other all the matter in it.
It was surely a foregone conclusion.
Physics seemed to be on the edge of glory,
but it all went terribly wrong.
Try as they might they just couldn't get the two ideas to merge
and then, after 10 years of struggling, something even worse happened:
their two pet theories now began to self-destruct.
The first problem appeared with the Big Bang.
The cosmologists had assumed that as they worked backwards in time
they would eventually work their way back all the way to the beginning of the Big Bang.
There would be no awkward gaps,
but after years of end-less refinement there was one gap which refused to disappear,
the most important one of all.
The fundamental problem of cosmology is that the laws of physics as we know them
break down at the instant of the Big Bang.
Well some people say what's wrong with that,
what's wrong with having the laws of physics collapse?
Well for a physicist this is a disaster.
All our lives we've dedicated to the proposition that the Universe obeys knowable laws,
laws that can be written down in the language of mathematics
and here we have the centrepiece of the Universe itself,
a missing piece beyond physical law.
The very beginning of the Big Bang
was the single biggest mystery in all of cosmology.
It was called the singularity.
When you extrapolate Einstein's general Theory of Relativity back to the beginning
you discover what we call a singularity, a cosmic singularity,
which is to say that the equations blow up.
But the problem with the Big Bang was soon overshadowed.
The strings were in trouble, too.
The hope had been that String Theory
would evolve into the single definitive explanation for the Universe,
but as more and more people worked on it something puzzling happened.
The physicists found a second version of it and then a third.
Soon they had found five different String Theories.
That wasn't single and it didn't sound very definitive.
Five, even though it's not a very large number, is too large
for us because we would like to have a more unique theory than that
and this definitely was a problem, was a great crisis,
so a lot of time was spent studying those individual five theories,
but in the back of our minds always was why are there five of these things,
shouldn't there only be one?
String Theory had begun to unravel.
It seemed as if the dream of a Theory of Everything was as far away as ever.
Cynics began to come out and say that String Theory is too hard, it's a dead end,
it's simply not the way to go and it's not the Theory of Everything,
it's the theory of nothing.
But just as the scientists were about to give up hope,
a new and startling discovery would be made.
This would inspire them to begin their quest again
and force them at last to confront their least popular idea: parallel universes.
When String Theory fell apart, not everyone was distraught.
Some people even seemed to relish the fact.
If String Theory really was this so-called Theory of Everything
five theories of everything seems like an embarrassment of riches.
Michael Duff had been the rising star of an earlier idea called super gravity.
String Theory had displaced it and almost destroyed Duff's career.
Physics tend to be dictated by fad and fashion.
There are the gurus who dictate the direction in which new ideas grow.
It was a very lonely time in many ways.
When I tried to get graduate students interested many of them would say:
well, look, you may be right and you may be wrong,
but if I work in super gravity I'm not going to find a job.
What made the experience of the super gravity guys so galling
was that their theory wasn't so very different
from String Theory to begin with.
In fact, the main disagreement between them
was a point of detail which, to outsiders, could seem like nitpicking.
It was about the number of dimensions in the Universe.
We normally think of ourselves as living in a three-dimensional world.
We can move in three ways:
left or right, up or down, and forwards and backwards,
but physics liked adding extra dimensions.
Einstein suggested time should be a fourth dimension.
Then someone suggested a fifth spatial dimension and then a sixth.
The numbers just kept growing.
The extra dimensions were spaces in the Universe which we could never perceive.
Most were microscopically small
but scientists believed they were really there.
String Theory had been convinced there were in total exactly 10 dimensions.
Now if you have a little oscillating string it has to have enough room to oscillate properly
and when one works this out mathematically you find it,
it just got a very clear answer. It had to be in 10 dimensional space.
Ten dimensions.
Nine spatial dimensions and one time.
Super gravity though had been convinced there were exactly eleven dimensions.
The equations of super gravity took their simplest and most elegant form
when written in this 11 dimensional framework.
There was a war between the tenth dimension and the eleventh dimension.
In the 10-dimensional bandwagon we had string theorists, hundreds of them,
working to tease out all the properties of the known universe
from one framework: a vibrating string
and then we had this small band of outcasts, outlaws, working in the eleventh dimension.
In a final desperate move
the string theorists tried adding one last thing to their cherished idea.
They added the very thing they had spent a decade rubbishing:
the eleventh dimension.
Now something almost magical happened to the five competing String Theories.
The answer turned out to be - and it really was absolutely remarkable,
I mean it really is remarkable - it turns out that they were all the same.
These five String Theories turned out to be simply different manifestations
of a more fundamental theory,
precisely this theory which we had discarded back in the early 1980s.
In 11 dimensions looking from the mountain-top, looking down
you could see String Theory as being part of a much larger reality,
reality of the eleventh dimension.
Well it was a wonderful feeling
to think that all those years spent in the eleventh dimension
were not completely wasted.
The two camps had been absolutely certain the other was wrong.
Now, suddenly, they realised their ideas complemented each other perfectly.
With the addition of one extra dimension
String Theory made sense again,
but it had become a very different kind of theory.
What happened to the string?
The tiny invisible strings of String Theory
were supposed to be the fundamental building blocks of all the matter in the Universe,
but now, with the addition of the eleventh dimension,
they changed.
They stretched and they combined.
The astonishing conclusion was that all the matter in the Universe
was connected to one vast structure: a membrane.
In effect our entire Universe is a membrane.
The quest to explain everything in the Universe could begin again
and at its heart would be this new theory.
It was dubbed Membrane Theory, or M Theory,
but so enigmatic and profound did the idea seem
that some thought M should stand for other things.
M Theory.
Where M stands for magic, mystery or membrane.
M Theory.
Physicists get kind of dreamy-eyed when they talk about M Theory.
M Theory.
Maybe M stands for mother, the mother of all strings.
Maybe it's magic. Maybe it's the majesty,
the majesty of a comprehensive theory of the Universe.
M Theory.
Magical mystery, madness.
M Theory.
With M Theory it seemed at last
there was a theory which might explain everything in the Universe,
but before they could decide if this was true
the scientists needed to know more about this new eleventh dimension.
It quickly became clear it was a place
where all the normal rules of common-sense have been abandoned
For one thing it is both infinitely long, but only a very small distance across.
That eleventh dimension will, at its maximum size,
could be something like a trillionth of a millimetre.
Well this is 10 to the -20 of a millimetre.
That's taking a millimetre and dividing it by 10 with 20 zeros after it,
so that's very, very small.
That means that it exists only one trillionth of a millimetre
from every point in our three-dimensional world.
It's closer than your clothes to your body
and yet we can't sense it.
In this mysterious space our membrane Universe is floating.
At first no one could imagine how that worked.
Then some suggested it might float like a thin rubber sheet.
Others that it might be more like a bubble which vibrated
as it was blown aimlessly across hyperspace.
If all this wasn't surreal enough, it was then proposed
that there might be another membrane universe
pulsating at the opposite end of the eleventh dimension.
At first this idea wasn't taken very seriously,
but eventually it would be re-examined
for physics was about to ask whether our Universe was really alone.
It began with Lisa Randall.
People look at rock climbing saying it's of course very physical,
but you also find that you can concentrate on one little thing.
I like solving problems, I like games, I like figuring things out.
Randall had been fascinated by an apparently inexplicable phenomenon:
the weakness of gravity.
There are various forces we see in nature.
Most of them we understand at some level
and then there's gravity
which seems very different.
The gravitational force is extremely weak in comparison with the other forces.
Now you might look around and say gravity doesn't seem weak,
but if you think about it you have the entire Earth pulling on you
and yet you can manage to pick things up.
Gravity certainly does not look weak in everyday life.
It's responsible for keeping our feet on the ground
and keeping Earth spinning around the Sun and so on,
but actually gravity is incredibly weak compared to the, to the other forces.
This is easy to appreciate if you take an ordinary refrigerator magnet
and stick it on top of a metal pin.
We all know this fridge magnet will actually pick that pin up off the table,
so that sort of dramatically illustrates how feeble gravity is
compared even to the magnetic force of a tiny fridge magnet.
It turns out that there are very new ideas on how to explain the weakness of gravity
if we have extra dimensions.
When M Theory emerged,
Randall and her colleagues wondered if it might provide the explanation.
Could gravity be leaking from our Universe
into the empty space of the eleventh dimension?
Gravity might only appear to be weak
even though it's fundamentally just as strong as everything else
because it dilutes its strength out in all these extra dimensions that we can't see.
Randall tried to calculate
how gravity could leak
from our membrane Universe
into empty space,
but she couldn't make it work.
Then she heard the theory
that there might be another membrane in the eleventh dimension.
Now she had a really strange thought.
What if gravity wasn't leaking from our Universe but to it?
What if it came from that other universe?
On that membrane, or brane, gravity would be as strong as the other forces,
but by the time it reached us it would only be a faint signal.
Now when she reworked her calculations everything fitted exactly.
If you were to imagine that there are two membranes.
Say there's one in which we sit
and one in which
if there's other stuff it sits there,
but not our particles, not the stuff that we're made of
and not the stuff that we see forces associated with.
If we lived anywhere else in the extra dimension,
we would see gravity as very weak
because it's mostly spending its time near the other brane.
We only see the tail end of gravity.
The weakness of gravity could at last be explained,
but only by introducing the idea of a parallel universe.
Randall's idea opened a Pandora's Box.
Now suddenly physicists all over the world
piled into the eleventh dimension trying to solve age-old problems
and every time it seemed the perfect explanation
was another parallel universe.
Everywhere they looked,
it seemed they began to find more and more of them.
From every corner of the eleventh dimension
parallel universes came crawling out of the woodwork.
Some took the form of three-dimensional membranes,
like our own universe.
Others, were merely sheets of energy.
Then there were cylindrical and even looped membranes.
But in no time at all,
the eleventh dimension seemed to be jam-packed full of membranes.
We began to ask ourselves the question:
who lives in the eleventh dimension?
We have intersecting membranes, we have membranes with holes in them,
we have membranes that look like doughnuts
or have many different kinds of doughnut holes.
We're just littered with different kinds of membranes.
This eleventh dimension not only had
the membrane, which was the bubble-like or sheet-like object,
but it had a whole wealth of different branes of varying dimensions,
unfortunately called pea branes.
Each of these membranes was a possible other universe.
M Theory had unwittingly made the idea
of parallel universes respectable again.
In another universe the proton may be unstable,
in which case atoms would dissolve,
and DNA cannot form
and therefore there's no intelligent life in these universes.
Perhaps it's a universe of electrons and electricity
perhaps a universe of lightening bolts and neutrinos, but
no stable matter.
The other universes are parallel to ours and may be quite close to ours,
but of which we'd never be aware.
They may be completely different
with completely different laws of nature operating.
It may not all have life, but some fraction of them will have life
and whatever that fraction is if there's an infinite number of these universes
there'll be an infinite number of universes that have living civilisations.
Some of these universes may look just like ours,
except perhaps you're not there.
M Theory was getting stranger and stranger,
but could it really be a theory which explained everything in our Universe?
To have any chance of that
it would have to do something no other rival theory had ever been able to do.
It would have to make sense of the baffling singularity
at the beginning of the Big Bang.
M Theory was about to come up with a suitably outrageous answer
and parallel universes would be at the very heart of it.
I was a teenager, I don't remember quite when it was
and I don't remember precisely why
my father and I were down in Manhattan at the harbour.
One of the great ocean liners at the time was the Michelangelo
and it was in harbour I remember on the west side of Manhattan,
must have been near 42nd Street.
It was a remarkable sight
It's an enormous ship,
let's say 150 or 200ft high,
and the entire superstructure in the front of the ship,
the entire bow had been just crushed
by a wave which had blown out all of the windows
in the forward bulkhead right up to the bridge.
This is one of what they call a white wave, or a rogue wave
which had hit the Michelangelo and done all this damage.
What's interesting is that there are waves
somewhat similar to this which inhabit the higher dimensions
and then you can imagine if you had this huge
rogue wave moving through the higher dimension,
if it slams into another wave
you're going to have a tremendous cataclysmic collision.
Waves had long fascinated Burt Ovrut.
Now they were just about to turn M Theory upside down.
At the beginning of 2001 the received wisdom
was that the eleventh dimension was a tranquil place
with membrane universes gently floating in it,
but Burt suggested a much more exciting idea.
Universes moving through the eleventh dimension like giant, turbulent waves.
These things can move. They are not static,
they're, you know, like everything else in the world they can move around
and there's not much room for them to move in.
In fact if they move they're very likely to bang into each other.
In fact they either move away from each other, or they bang into each other,
and one thing that had occurred to me very early on is what happens if they collide?
To a new generation of cosmologists like Neil Turok
Burt's vision of the eleventh dimension sounded intriguing,
but he and his colleagues had other things on their mind.
They were still wrestling with the big problems of cosmology.
Was there a beginning? Did time continue before the Big Bang?
Where did the Universe come from?
Above all, they were still trying to solve the biggest problem of all:
what caused the very start of the Big Bang, the singularity?
Nobody has a solution for the singularity problem
other than essentially by hand starting the Universe at a certain time
and saying let's go from there and let's not worry about what happened before
and that's very unsatisfactory.
This is the deepest problem in cosmology.
If you can get through the singularity
you're on your way to a complete theory of the Universe.
Most cosmologists have begun to think they might never find a solution.
They'd almost given up completely, which is when Turok and his colleagues
heard Burt explain his idea properly for the first time.
At a conference in Cambridge pioneers of M Theory
had been brought together to explore its implications.
Burt was the star of the show. His vision of a violent eleventh dimension
wowed the assembled physicists and caught the attention of the cosmologists.
We heard about a vast variety of ideas.
The ideas that struck both Neil and myself most strongly
were the ideas that Burt presented.
On the last day of the conference
Neil Turok, Paul Steinhardt and Burt decided to take time out.
They went to see a play.
We wanted to see the play Copenhagen
which was being performed in London at the time
and the three of us took the train down to London one evening
and we had whatever it was, an hour or so on the train
to sit and talk about these ideas.
On the journey they began to throw ideas around.
Three physicists, one train, and the biggest secret about our Universe:
what caused the Big Bang.
I think people get the wrong impression about about scientists in that
they think in an orderly, rigid way from step 1 to step 3.
What really happens that often you make some imaginative leap
which at the time may seem nonsensical.
you capture the field at those stages it looks like poetry
in which you are imagining without yet proving.
Paul, Burt and me were sitting together on the train
and just free associating.
One of us, maybe it was me, began by saying
"Oh, well why can't we make a universe out of collision?", and
Neil sort of pitching in and saying "Well,
if you did that then you could create all the matter and radiation of the Universe",
so we had this conversation, one of us completing the sentences of the other
in which we kind of just, just let our imaginations go.
And as we went along,
at least I learned more and more about how it might be possible
to have these brane collisions produce all of the effects of the early Universe
and in particular it's just easy to do with my hands,
when they collide you might have a Big Bang.
And the Big Bang is the aftermath of some encounter between two parallel worlds.
But how could such a collision go on to cause the world we know?
The Universe we live in has vast clumps of matter we call stars and galaxies.
We know that things are not smooth out in the Universe.
In fact we have little clumps, we have stars, we have galaxies,
we have quasars, we have clumps of matter.
Now they had to explain how the collision of two parallel universes
could go on to create these lumps of matter.
Was there something about the membranes, or branes, which could explain it?
People tended to think of branes as being
flat, perfect sheets, geometrical plains,
but I think to us it was clear that that picture could not be correct.
It cannot be perfectly flat. It has to ripple.
What would happen as these branes approach
that there are ripples in the surface of each brane
and when they come together they don't hit at exactly the same time, same place,
but in fact they hit at different points and at different times.
We found that as the brane moves it literally ripples,
so when the collision takes place it imparts those ripples into real matter.
The parallel universes move through the eleventh dimension like waves
and like any wave these would ripple.
It was the ripples which went on to cause the clumps of matter after the Big Bang.
They finally had their complete explanation of the birth of our Universe
and now they could do something even more profound.
They could take the laws of physics back in time
to the moment of the Big Bang and through to the other side.
The existence of branes before the singularity
implies there was time before the Big Bang.
Time could, can be followed through the initial singularity.
You sort of go back and back and back
until you get near the place where the expansion would have taken place
and then it just sort of changes into another world.
When the branes collide
the collision of those can be explained within M Theory,
so it just simply enters the realm of mathematics and science now
rather than being a, an unknown point that exploded.
The singularity had disappeared
and it had taken them just under an hour.
Then we went to see the play.
This idea is so new it's only begun to be discussed,
but if it's accepted it will mean Einstein's missing theory has finally been found.
M Theory may really be able to explain everything in the Universe,
but the victory will be bittersweet,
for at the end of its long quest, science has discovered
that the Universe it sought to explain may be nothing special.
It is nothing more than one of an infinite number of membranes,
just one of the many universes which make up the multiverse.
The latest understanding of the multiverse
is that there could be an infinite number of universes
each with a different law of physics.
Big Bangs probably take place all the time.
Our Universe co-exists with other membranes, other universes
which are also in the process of expansion.
Our Universe could be just one bubble floating in an ocean of other bubbles.
But this isn't quite the end of the story.
Now that the Theory of Everything may have been found some are keen to use it.
Physics is preparing for the ultimate flight of fancy:
to make a universe of its very own
without any mysteries or unanswered questions at all.
I in fact have worked with several other people for some period of time
on the question of whether or not it's in principle possible
to create a new universe in the laboratory.
Whether or not it really works we don't know for sure.
It looks like it probably would work.
It's actually safe to create a universe in your basement.
It would not displace the universe around it
even though it would grow tremendously.
It would actually create its own space as it grows
and in fact in a very short fraction of a second
it would splice itself off completely from our Universe
and evolve as an isolated closed universe
growing to cosmic proportions
without displacing any of the territory that we currently lay claim to.