"Stephen Hawking's Universe" is made possible
by Alfred P. Sloan foundation to enhance public understanding
of the role of science and technology,
the Arthur Vining Davis foundations,
the corporation for public broadcasting,
and viewers like you.
Corporate funding is provided by Amgen,
unlocking the secrets of life through biotechnology.
At Amgen, we produce medicines
that improve people's lives today
and bring hope for tomorrow.
Stephen Hawking: In the last hundred years,
our understanding of the universe
has advanced far farther than in previous centuries.
We have discovered that the universe and time itself
had a beginning 15 billion years ago.
There was a cosmic explosion of energy
called the big bang.
The energy produced
all of the matter in the universe,
from stars and galaxies to our own planet
and even ourselves.
Yet one question still needs an answer.
How did the big bang begin?
We need to know the laws
that held at the moment of creation
when the universe sprang into existence.
Are these initial laws over and above the laws
that tell us how the universe evolves?
Or is there a theory of everything
that governs the universe at all times
and determines how it begins and develops?
Narrator: "I shall never believe," said Einstein,
"that god plays dice with the world,"
words that might bring gloom
to the gambling capital of the east.
Atlantic City has two sides --
one that's flush with big casinos,
one old and simple as a small town.
Today, physicists are grappling
with a dual universe --
one great as all the cosmos, one infinitesimally small,
both a puzzle to sydney Coleman.
Coleman: physics starts out by trying to explain
the sort of phenomena that occur in everyday life --
balls bouncing and planets round and round the sun,
and all that stuff.
And that's also pretty much the sort of stuff
that you encounter in everyday life,
and your tacit assumptions about those things
and how they behave are deeply embedded
in the language of everyday speech.
That's how the language of everyday speech developed.
Narrator: But physics has now gone beyond the familiar.
Theorists like Coleman spend their days
making imaginary journeys into strange new worlds,
far removed from everyday life.
as physics develops
and physicists want to find out more and more,
they try and understand physics
which reveals itself only under extreme conditions --
on the inside of an atom, in a high-energy accelerator,
in a quasar, during the beginning of the universe.
Now it would be really remarkable if the concepts
of everyday speech continued to be valid
when we extend the universe of study so enormously.
It's only natural that,
as we get farther and farther from everyday experience,
the theories we have to describe all this new stuff
in addition to everyday experience,
should look less and less intuitive.
Why should your intuitions have developed
to be good inside a quasar?
Your ancestors did not spend any time inside quasars.
So things seem to get,
from our viewpoint, our earth-bound viewpoint,
stranger and stranger.
Narrator: That the universe is vast and expanding
is accepted wisdom.
That it began at a tiny point
is accepted as well.
Each extreme has its own theory to describe it.
Coleman: When you trace the evolution of the universe
backwards in time, you inevitably find yourself
being pushed towards the physics of the very small.
Narrator: The world of the minute
has its own peculiar laws.
And it was at this scale,
millions of times smaller than a single atom,
that the universe began.
The study of the subatomic realm
is called quantum mechanics.
Woman: Two foundation stones, really,
on which we've built current modern picture
of the universe and the matter in it
are quantum mechanics and general relativity.
Einstein was instrumental in both of those theories.
He was a founder of quantum theory
and the sole inventor of general relativity.
And the picture that they give us of the universe
is a very good one in the sense,
we can make a lot of predictions
and explain a lot of phenomena.
But the picture is really only partial in many ways.
And one of the problems is that the two theories,
in fact don't fit together
Narrator: Einstein described
the large-scale universe,
a realm where gravity
is the dominant force.
Quantum mechanics concerns
the behavior of atomic particles,
governed by forces wholly different.
But a complete theory of the universe
has to embrace everything,
from the tiniest traces to the largest galaxy.
Dowker: Einstein believed
that he could find a way to make them fit,
because the methods that he had applied
to problems in physics before had always worked.
He'd been very successful in unifying things.
He trusted his instincts.
So his instinct was that there should be a theory
which described the two theories together.
Narrator: In his twilight years,
Einstein pursued a quest he alone believed in.
He went his own way,
dreaming of a single theory of everything.
Dowker: He spent decades on this work.
He worked basically alone.
I think that no one else shared his view
that this was the way to go in unification.
So he was very solitary,
and he was working by himself
up until the day he died.
Narrator: Pages of his notes were found at his bedside,
but his unifying theory was unfinished.
He had failed to realize his dream.
But Einstein, as always, was ahead of his time.
Four decades later,
his quest is being pursued by others.
Theorists are rallying to find a single equation
that can resolve the old contradiction
between quantum mechanics and relativity.
They, too, are looking for a theory of everything.
Hawking: at the beginning, the universe is a single point.
the next instant, it is enormous.
To understand this properly, we need a theory of everything,
which is still just beyond our grasp.
However, we already
have some ideas why the expansion
of the early universe was precisely what it was.
Narrator: In their effort to uncover the ultimate mystery,
scientists have intuition and intellect to guide them.
Yet slowly their search is being rewarded,
one fledgling theory at a time,
for they do have one more resource at their disposal.
With new technology comes new insight.
Observation offers inspiration.
giant particle accelerators, such as SLAC,
in Palo Alto, California,
smash atoms into each other.
These collisions create miniature explosions
producing energies, temperatures,
and pressures that mimic
the very conditions of the big bang.
In the 1970s, a striking portrait
of the early universe emerged --
one poised on a cosmic knife edge.
Man: What was always needed,
and nobody had really pointed this out,
was that you had to assume
that the expansion rate of the early universe
was tuned almost exactly right --
that is, almost exactly the right expansion rate
so that the universe would be just on the verge
of eternal expansion versus eventual collapse.
If one talks about the universe
at a time of about one second after the big bang,
this tuning, this precise fixing of the expansion rate,
had to be done to an accuracy of about 15 decimal places.
If the universe just expanded
one part in the 15th decimal place
faster than we thought it had,
it would fly apart
without galaxies ever having a chance to form.
If the universe at one second after the big bang
were expanding with one number less
in the 15th decimal place than what we thought,
then the universe would collapse
before galaxies had ever had a chance to form.
To make the universe work,
the universe had to be perched just on this borderline.
Narrator: For 15 billion years,
expansion has run its course in perfect measure.
What fluke of physical law
managed to strike this uncanny balance?
Alan Guth was pondering equations of immense complexity.
Yet the questions he was grappling with
were so simple,
they were the kind posed by a child.
Man: When I was still a kid,
i asked myself a question --
well, how could it happen
that in different parts of the universe expansion
started simultaneously?
Who gave the signal?
How can I understand it?
And then I thought that maybe when I would grow older
I will open the books
which are written by clever professors,
and I will find out the answer.
When I grew older,
I found that people did not know that the question exists.
Narrator: A probing mind is a restless one.
Andrei Linde, a russian,
has unlocked a secret of creation.
Linde: During the last 15 years,
we've learned that the question can be answered.
Narrator: Linde, like Guth, now lives in the United States.
But in the '70s,
they were on opposite sides of the world,
unbeknownst to each other, simultaneously working
on the same remarkable theory called "inflation."
so, would you give me a glass of water?
Sure.
Narrator: Linde and Guth found a model
for the early universe in the simplest of phenomena.
If energy had somehow
been trapped in a vacuum then released,
space and time could have expanded,
like so many bubbles.
Perhaps these bubbles had collided, united,
then rapidly expanded as one vast bubble,
a symmetrical universe, growing smoothly, quickly,
and evenly in all directions.
Linde in Moscow and Guth in California
were kindred spirits.
Both needed to do detailed calculations
to see if the idea could work.
One winter's evening in 1979,
Guth opened a notebook and began to write.
Guth: I had not yet calculated everything through, that night,
enough to convince myself that it was a fascinating idea
and that it would probably work.
The next morning
I raced back to SLAC, and actually I kept track
of my personal biking records to SLAC,
and I set a new record that morning.
Once I got there, I whipped out my notebook
and started continuing the calculations,
and by, I guess, the end of the morning,
I convinced myself that it did fit together.
Narrator: Linde was also making headway.
But it wasn't long before his proverbial bubble burst.
The numbers simply weren't adding up.
Across the globe, at the same time,
inflation was turning out to be deflating.
Guth: As I continued to work on inflation,
I did however discover that there was a serious problem
in the way that inflation finally ended.
It happened just like water boils.
A bubble would form here, a bubble would form there,
the bubbles would grow and collide
and form an incredible morass of matter
with tremendous non-uniformities in it.
Would look, in fact, nothing whatever
like our universe looks like.
This was a serious problem that clearly required a modification.
Thank you.
You're welcome, sir.
Narrator: Still, Guth went ahead and published his work.
Despite its flaws, the theory
caused a sensation.
Guth: All of a sudden
my career had just changed overnight dramatically,
And it was an amazing experience that every scientist
should have a chance to have once in his life.
Narrator: In Russia, it's against scientific tradition
to publish an idea without
all the details worked out.
Linde had labored long and hard,
only to be outdone by his own principles.
Worse, he feared his precious theory
might be compromised by its premature unveiling.
Today, at long last,
comes a rare meeting of the minds.
Linde: I don't know whether you know or not,
but I had an ulcer
which was induced by your work,
in some sense,
because when I heard about all these ideas,
i was really, literally, thinking in these terms --
that god could not be so stupid
to lose this opportunity
to make the world in such a economical way.
And when I found a solution,
the ulcer is gone.
Well, so sometimes physics helps.
Narrator: Linde had a new idea.
What if just one bubble of energy had inflated
and become our universe?
Linde: It was about 11:00 at night,
and I could not keep myself from, well,
this feeling of happiness.
And I came to my wife and eventually waked her up,
and I told her, "look, it seems that I know
how the universe could have emerged."
I first announced a new inflationary scenario
in the meeting of quantum gravity in Moscow,
which occurred in october '81.
And at that time, many very good physicists in Moscow,
and the star of the meeting was Steve Hawking.
Hawking: I gave a seminar
with Andrei translating.
When I said there was a difficulty
with Guth's idea of bubbles in collision,
Andrei said that the whole universe
could be a single bubble.
I objected,
because the bubble would have been bigger
than the universe at the time.
Linde: In the middle of his talk,
he told that there was a very interesting idea
of Andrei Linde recently.
This was just my talk the previous day,
and I was, oh, my heaven, he's translating it.
And then he says
but this model, this idea does not work,
and let me explain why.
And he starts talking and talking,
and I'm translating it,
and for a half an hour,
in the face of all the institute,
I was explaining to them why he knew inflation
just simply cannot work.
Narrator: Humiliation came in double doses to Andrei Linde.
In front of respected colleagues,
he saw his theory demolished.
Linde: And then I told Steve,
"Would you like to actually understand the details of this?"
and he told me, "Sure."
And then we disappeared for two hours.
All the institute was trying to catch steve everywhere,
and the famous physicist disappeared.
The whole institute was in panic.
Hawking: Linde and Guth had given us an important idea.
Inflation accounts so neatly
for the way the universe has to expand,
I'm sure it must be part of the final picture.
But inflation by itself
does not explain the start of the universe.
We still need a theory of everything for that.
And applying the theory
to the beginning of the universe would be difficult,
because my own work had shown
that the equations would break down
at the big bang.
Coleman: You can take
Einstein's equations and run them backwards in time,
not for a real universe,
which is complicated, full of
lumps and irregularities,
but for a simplified model of the universe,
where matter is distributed smoothly and uniformly
throughout the universe.
And when you did run it backwards in time,
you found, eventually, there was a point in which
everything came together at a single point,
where gravitational fields became infinitely strong,
energy densities became infinitely high.
Technically we call it a singularity.
Narrator: It is the netherworld of physical law.
A singularity like the big bang is a realm beyond comprehension,
where logic is replaced by chance...
where matter is ruled by mere probability,
and scientists must resort to summing up
the rolls of the dice.
Coleman: Physicists like to solve equations.
They like to say,
if this is the way things are now,
this is the way they'll be a year from now.
Once you hit a singularity, you can't do that.
The equations blow up,
and you don't know what to do with it.
This is disturbing.
People don't like singularities.
Narrator: The best bet
for solving the mysteries of singularities
is quantum mechanics.
Coleman: Quantum mechanics is probably the strangest thing
human minds have ever thought up.
I think if 1,000 philosophers were to work for a 1,000 years,
trying to think up something of maximum strangeness,
they wouldn't have thought up
anything as strange as quantum mechanics.
Narrator: Think of it as a game of chance.
Quantum mechanics is based on Werner Heisenberg's
"Uncertainty principle."
A subatomic particle
is too small to actually see directly.
We can never know with precision
where anything that small really is.
But as it moves,
it traces a path we can try to predict.
We can venture a bet of its probable position.
As it turns out, the uncertainties
taken together add up to revelations altogether certain.
Coleman: Strange as it is, it is apparently
the way the universe works
that enables us to make predictions
about all sorts of processes involving atoms
or elementary particles colliding,
That are verified by experiment to amazing degrees of accuracy.
Narrator: The problem is the laws of uncertainty
only make sense for the universe
as a whole at its moment of creation.
They can't be applied to the universe today,
to the stars and planets governed by gravity,
and with motions described by relativity.
Coleman: A lot of people have been trying to combine
quantum mechanics with gravity over the years,
a quantum mechanical replacement
for Einstein's general relativity.
Hawking: I wanted to resolve the problem of the singularity.
After all, I was largely responsible
for raising it in the first place.
Maybe one could choose a path around it.
Coleman: Hawking saw that the uncertainty
that came when you tried
to combine quantum mechanics and gravity
was in fact an escape route,
and could be used to get away from this --
avoid the singularity problem,
which he himself had done so much to raise.
In a remarkable paper
done in collaboration with James Hartle,
Hawking was able to solve
a very, very simplified model of the universe.
Hawking: Jim Hartle and I showed
how a universe like our own
could be born without the troublesome singularity.
It involved the use of what is called imaginary time.
This may sound like science fiction,
but it is a well-defined scientific concept
that science fiction borrowed.
The idea was that in imaginary time
the universe has no boundary,
no beginning or end.
It just curls round on itself like the surface of the earth.
Coleman: It was a complete quantum mechanical description
of everything that could be said
about this simplified model of the universe,
and it had no singularities.
It's possible that quantum mechanics
is the answer to the problem of the singularity.
Hawking: I have to make it clear
that the no-boundary universe is just a proposal,
but it has some interesting implications.
Without boundaries,
the universe has no beginning and no end.
We don't have to explain its creation.
The universe simply exists.
But the consequences of the no-boundary proposal
cannot be worked out fully
without a complete quantum theory of gravity
that will unite general relativity
and quantum mechanics.
We are back to the search for a theory of everything.
Narrator: While others turn to the heavens for their models,
cosmologist Lee Smolin looks a little closer to home.
The answer to his universe is not contained
in any mathematical equation.
Smolin: The hope was that there would be one simple law
which would have a unique solution,
which would explain
how the universe is,
the history of the universe, and so forth.
And that hope that all the questions
would be answered in a single law
is what has not happened.
So I wondered about this a great deal.
And I was thinking about this
at the same time that I was reading about biology.
That led me to begin to wonder
whether the answers to some of the questions
in elementary particle physics
did not rest in a single unique theory,
but maybe would be a result of historical accident,
and maybe there could be a process by which,
through a series of developments
in the early history of the universe,
somehow the universe chose what its parameters were.
The wonderful thing about the biological world
is that it's so complicated.
There are so many different species,
they're so beautiful in so many different ways,
and one would think that one could not possibly explain this,
which is of course what people thought before Darwin.
What Darwin discovered
is that there is a rational way to understand
how such enormous variety and complexity
can come to be in the natural world,
without being put there in the first place.
And the basic idea is that you have some population
which can reproduce itself,
that when it does so,
there are small, random changes in the characteristics,
and that these characteristics lead to differences
in how well the creatures survive.
Narrator: Smolin's theory of everything
has a familiar ring.
it's inspired by darwin's idea of natural selection.
Smolin: The universe, like the biological world,
seems to have discovered all sorts of ways
to keep itself out of equilibrium and to keep
an enormous variety of things going on.
And the universe also invents life,
which is very impressive,
and many cosmologists have wondered,
how could it be that all of this
improbable structure and organization comes to be,
out of the world that evolves out of the big bang.
Narrator: Imagine the universe as a product
of the same evolutionary processes
that later gave rise to us.
Smolin: If one studies astronomy
on scales much, much larger than the Earth --
for example, the disc of a spiral galaxy --
one discovers it's a complex, self-organized system,
somewhat akin to biology on a much simpler level.
It turns out that
the ideas by which we understand the patterns on sea shells
or the stripes on an animal's coat
are very close to the ideas by which we understand
how the galaxies get
their beautiful spiral structures.
What occurred to me was maybe the explanation
for why the parameters of the laws of physics
are right to produce all this complexity
is like the explanation of biology.
The new possibility which Darwin gave us
is that a system can have all the beauty
and variety and complexity of our world
and be assembled from itself,
that it can organize itself over time.
What 20th-century science
is leading to is, in my view --
and of course, could be wrong --
the culmination of this view of the universe
as something which does create itself and assemble itself.
Of course, it's a new idea,
and it's very, very far from being demonstrated,
although I must say that I'm very struck by the fact
that it wasn't proved wrong yet.
But the idea that maybe the universe as a whole
organized itself by some natural process
makes one feel more at home.
Narrator: What preceded creation?
The theorists who are exploring the question
are pioneers, standing alone at the frontiers
of an impenetrable wilderness.
For Andrei Linde, this lonely pursuit
was taking its toll.
'85 was the first year of perestroika,
so the first year of perestroika,
Gorbachev just came to power,
and they started reconstructing everything,
which is a translation of the word perestroika,
the reconstruction.
And as a first step,
they'd completely forbidden us to send our papers abroad,
so I had a feeling that I am living with my mouth shut.
I cannot tell others what I am doing,
and this was pretty depressing.
So I became so much depressed
that I actually became simply ill,
and now I was lying in the bed
for about a month and a half, and then, all of a sudden,
there was a call from academy of sciences.
They told me that I must go to italy
to give some popular lectures on astronomy.
And I told them, "I am ill, I cannot go."
Narrator: He'd suffered years of frustration
and months of repression.
Now Linde was suddenly free to say what he liked.
He had 24 hours to find something worth saying.
Linde: After this year with the mouth shut,
they are suggesting to me that if I do something,
then tomorrow it will be sent there
by diplomatic mail without any approvement,
without any signatures,
without any of this bureaucratic work.
Tomorrow it will be in Italy.
On the other hand, it must be done just immediately,
and I am really sick.
I just cannot.
I took my head like that, and I started thinking,
"What can I invent within half an hour or so?
"I will write it today in the evening,
"and tomorrow I'll send it to Italy.
What can I do within half an hour?"
And within half an hour,
I have got a theory of self-reproducing universe.
Narrator: In Linde's new theory,
inflation must have produced a multitude of universes.
Instead of just one growing, there had to be many --
each universe different,
each the product of its own big bang.
In time, they will seed other universes
so the process goes on forever.
Linde had experienced his own conceptual big bang.
Out of depression had come pure inspiration.
Linde: When I was really going to Italy,
I had four papers written
on the theory of self-reproducing universe.
I smuggled them to Italy without any permission,
and I came to Rome, and I gave lectures in Rome.
I came to Torino, I gave lectures in Torino.
I came to Trieste, and I gave the lectures,
and then they delivered my body to the railway station
and put me into a luxurious sleeping wagon,
and I looked into myself in the mirror --
this was '86, where I was 38 years old.
I looked in the mirror
and I have seen the body of an old person,
slowly moving from Trieste into the direction of Rome.
and then, after a while, I became healthy again.
And since that time I did not have such a depression,
which in a certain sense may be unfortunate.
Hawking: Smolin and Linde's evolutionary theories
have failed to catch on.
Most cosmologists, like me,
still want to find a single explanation
of a single universe.
Narrator: In 1985, a promising new theory emerged,
raising hopes the search would soon be over.
You're tuned to WBAI, 99.5 fm on your dial.
Coming up next, "Explorations" with dr. Michio Kaku.
Welcome. This is "Exploration"
This is dr. Michio Kaku,
professor of theoretical physics,
and this is a program devoted to science
and the fantastic discoveries as we explore the universe,
and of course, super string theory,
the theory that will perhaps
give us an explanation for the entire universe.
Some people say the instant of the big bang,
the universe was a dot.
The new picture is that it's like a bowl of noodles,
a bowl of noodles where we have
thousands and millions of little strings,
vibrating at the instant of time,
that exploded, creating
the enormous diversity of matter and energy
that we see around us.
Super string theory is so bizarre, so strange,
that we were not destined to see this theory
in the 20th century.
Many of us believe that it's really 21st-century physics
that fell accidentally
into the 20th century.
Narrator: Bubbles have their proponents,
uncertainty has its adherents,
but strings are the stuff of zealots.
It's based on a rarefied branch of mathematics,
and it's an idea so ahead of its time
that its time may not yet have come.
Kaku: Einstein spent the last 30 years of his life
trying to create a theory of everything,
a theory of black holes, of galaxies,
and a theory of atoms, of light, of force.
So we have two great theories of physics --
the theory of the very big, Einstein's theory of relativity,
and the theory of the very small,
the quantum theory.
And these two theories
they are incompatible.
One is smooth, beautiful, like marble,
and the other one is coarse and grainy like wood.
And to get them to meet together has been the object
of the last 50 years of intense investigation.
Today, we think we have it.
We think we have the super string theory,
which is perhaps the most fantastic,
the most marvelous theory ever proposed
in the history of science.
Narrator: String theory borders on mysticism.
It contemplates a universe
strewn with minute strands of space-time.
Kaku: Strings are extremely tiny,
like 100 billion billion times smaller than a proton,
so let me explain.
Take an atom, and expand it to the size of the solar system.
If the atom were the size of our solar system,
then a string is much smaller than that.
A string is the size of an atom.
That is how incredibly tiny this all is.
We also think that once upon a time
the universe was the size of a string.
When strings move, they vibrate.
And when they vibrate,
each note of this vibrating string
corresponds to a particle.
So if I had a microscope
that could peer into an electron or proton,
i'd see a vibrating string.
My own body is essentially a symphony of vibrating strings.
But when strings move, they force the space around it
to curl up, to bend,
exactly as Einstein had predicted.
Narrator: Strings are the theorist's darling.
They are a structure hatched specifically to cater
to the discrepancies
in the divergent theories of physics.
True, they are wholly abstract, and have little basis
in reality so far,
but at least they may
provide the ties that bind
the two great schools of thought.
We physicists have been puzzled by the fact
that we have matter, like atoms,
and we have forces, like gravity,
that attract atoms.
Now we realize that this dichotomy
between force and matter
is really not a dichotomy at all.
These are nothing but vibrations of the same string.
One string that vibrates could be a quark.
Another string that vibrates could be an electron.
But yet another string that vibrates
could be light, a photon, or Einstein's theory of gravity.
Narrator: String theory, at its heart,
is a search for perfection,
to conjure a vision of creation
of consummate order and purity of form.
Kaku: Now, if you look at clouds or rocks or mountains,
we don't see symmetry at all.
But as we go backwards in time,
as we get closer and closer to the big bang,
we realize that there's a beautiful,
gorgeous, magnificent symmetry
that we begin to see emerging as we go backwards in time.
Now, we believe
that at the instant of the big bang
there was perfect symmetry.
The only theory which gives us this perfect symmetry
is the super string theory.
Narrator: Theorists today are walking a fine line
between models of the universe based on images
we can make concrete,
and concepts that seem, for now, beyond the imagination.
Kaku: These equations are well-defined,
they're well-known,
but some people think that perhaps we humans
are not smart enough to solve them.
Think of a duck or a monkey.
Why should a duck or a monkey understand calculus
or electric fields or black holes?
And why is it that we have the power
to understand the big bang and the black holes?
And then the question is,
are we smart enough to understand
the theory of everything?
At the present time, no.
Hawking: By the end of the '80s,
I and a number of other physicists
were beginning to wonder if string theory
really was the ultimate theory of the universe.
Narrator: In fact, string theory is no theory at all,
for a theory, by definition, must venture some predictions
that will ultimately be put to the test of reality.
Sublime and conceptually perfect as string theory is,
it needs someone to come to its rescue.
Kaku: In the last several years,
we've been in the wilderness.
the mathematics has proven too difficult
to solve super string theory.
The theory is smarter than we are.
The creative engine behind super string theory
is ed Witten of Princeton.
In fact, scientific american once said that Ed Witten is
"the smartest man on earth."
And if anyone is smart enough to solve super string theory,
it's probably going to be Ed Witten.
Witten: String theory is a mathematical structure
of a richness and subtlety we don't understand well.
There are many pieces of it that we've come to understand,
and they, by themselves,
are quite elaborate stories in their own right.
We don't yet have
a complete overview of the whole subject.
It seemed pretty clear that if there was a chance
to go way beyond our familiar understanding of physics,
string theory was the most ambitious prospect.
It also was clear then, as it is now,
that it is a very long-term proposition.
Narrator: Ed Witten has taken on the challenge
of tackling some of the most difficult mathematics
in the scientific world.
Witten: I wasn't originally interested in maths.
I was interested in doing physics.
And I remember very well
having some reticence
for quite some time about
making the 100% commitment,
of really deciding that was going to be my life.
Narrator: Witten's quest is to turn out
countless consuming mathematical constructions.
One, he hopes, will someday get strings
to actually describe the world.
Witten: The question was,
how realistic was it as a theory of nature?
My main interest was to make it more realistic.
For a few years there were very exciting developments,
and then we went through a period
where the progress was slower and more subtle.
We were dotting i's and crossing t's
and understanding details.
We were discovering things that were strange and beautiful,
but perhaps not of such wide ramifications
as the things done in the mid-'80s.
So things were slow
and the developments, I guess, were more mathematical.
String theory, as it had developed by the mid-'80s,
was characterized by the fact
that there were five theories we knew about.
And that raised the rather curious question
which was always a little bit embarrassing.
If one of those theories describes our universe,
then who lives in other four universes?
we've come to understand
that those five theories we've been studying
are all limiting cases of one bigger picture.
In the last couple of years, the picture has really changed
through something which is called duality.
Duality is a relationship between two different theories,
which isn't obvious.
If it's obvious, you don't dignify it
by the name "duality."
So we have different pictures.
And it's not that one is correct
and the other one isn't correct.
One of them is more useful
for answering one set of questions.
The other is more useful
for answering another set of questions.
And the power of the theory
comes largely from understanding
that these different points of view
which sound like they're
about different universes
actually work together in describing one model.
And I might say that 10 years ago
it just looked impossible that those theories
would turn out to all be one,
so it's a big conceptual upheaval
to understand that there's only one theory
which is our candidate for nature.
To make an analogy
with the blind men and the elephant,
there is the guy who discovered the trunk,
and there's the guy who discovered the tail,
and there's the guy who discovered the ear.
And in the past we thought
they were five different things.
Now we know there is one elephant.
We still don't understand that elephant too well.
Narrator: Witten remains convinced
string theory can be borne out.
His conviction has its price.
The new world he's charting is a lonely one.
It is populated only by strange and abstract ideas,
by many dimensions,
rather than the three the rest of us know.
A lot of people, even professional physicists,
in my opinion, don't fully grasp the scope and richness
of the structure involved.
People may tend to be too impatient for quick results
in some cases.
I think that there are a lot of reasons
to think that a structure
which is so rich and so physical
and which has been the source,
the continued source of so many beautiful discoveries,
must be on the right track.
Narrator: Witten is widely regarded
as the heir apparent to Einstein.
On he struggles, with little assurance
his work can be completed in his lifetime.
Witten: When you are doing a calculation,
it's usually on some very specific detail.
That's a tiny, tiny piece of the big picture.
And you're hoping that that piece will shed light
on the big picture.
Sometimes it does, but usually it doesn't.
Often times you come home
at the end of the day,
and you know exactly the amount you knew
at the beginning of the day.
But sometimes you know a little bit more.
I think that this investigation
is the richest thing that physicists can tackle now.
How far we'll get in our lifetimes,
there's no way to know.
We might get the answers we dream of getting.
We might fall well short.
But I think we can accomplish something,
a faith which i'd say is well-vindicated
by the duality revolution of the last couple of years.
I think we can accomplish more in the future,
and getting as far as we can is the best we can do.
Hawking: 20 years ago,
I said there was a 50/50 chance
we would have a complete picture of the universe
in the next 20 years.
That is still my estimate today, but the 20 years starts now.
it's very hard to build
a fully consistent quantum theory of gravity.
The string theorists think they have one.
They may or may not be right.
They haven't yet pushed their theory far enough
so you can compare
the consequences of string theory to experiment,
and that's what you ultimately need.
Narrator: While theorists around the world
pursue their lone predictions,
many are pinning their hopes
on a singular mission.
Neil Turok is preparing for a journey into the unknown.
He's about to explore a place called the past.
When he gets there,
he'll tell us what it looks like.
Turok: Imagine you were trying to navigate across a continent,
and you had a map which only showed features
greater than 100 miles across.
It wouldn't be much use in finding your way
along a particular route.
But if you have a map that has a resolution of a mile,
then that becomes much more useful.
Narrator: Turok is setting out
to make the map of all maps with a satellite
he plans to help launch early in the 21st century.
It's called the Planck explorer.
Turok: what we'll do is look out,
map the whole sky at a very high resolution.
Basically, this is equivalent to making a map of the Earth
where you show all the rivers and the mountains
and the valleys in exquisite detail.
And this map will contain a vast amount of information.
It will give us
the best picture we have of the universe.
Narrator: the Planck explorer
will be able to detect energy that was emitted
billions of years ago at the dawn of the universe.
For a study that has too long
searched for answers in the mind's eye,
it might provide a vision of sheer clarity.
Turok: It is a map of the universe
at very early times.
We're not sure quite when the radiation
from the big bang was emitted from the plasma
in the early universe,
but when we look out and we see the sky,
we're looking directly
at different patches of hot plasma,
and they are going to be
at slightly different temperature,
and so this will be a map
of the temperature variations on the sky.
Narrator: In those subtle vestiges of the big bang
are the secrets of its inception.
They will bear the signature of creation,
and with any luck,
the revelation that will clinch which theory wins the day.
The time may soon be at hand to know the ultimate truth.
I think people are usually
excessively confident about the theories,
because there has been an absence of data,
and that's allowed people
to be confident about the theories.
The current theories there are, are all based
on very clever ideas and very imaginative ideas,
but what's really good about them is
they do give you a well-defined framework
within which you can make predictions.
Narrator: We've already glimpsed the temperature fluctuations
of the big bang, but never in sufficient detail.
each theory of everything predicts a different outcome
to turok's experiment.
Perhaps he will at last settle the question,
or perhaps he'll only raise more.
Turok: We're in the wonderful situation now
where over the next 5 or 10 years,
the theory is going to be beaten to death,
or theories that we have will be beaten to death
in terms of making predictions.
That will all be settled,
and they'll all say exactly
what they expect to find on the sky.
And then this satellite will fly
and will map the sky to very high precision,
and we'll see what happens.
It's a very exciting time to be involved.
it's a unique opportunity in science where you're told,
within 10 years we're going to have the data
that will prove or disprove
any theory of how structure formed in the universe.
And you've got 10 years,
so we'll see if anyone gets it right.
Hawking: It could be that in a few years
we will have a complete theory that is confirmed by experiment.
It would be a remarkable achievement,
perhaps the ultimate triumph of science.
But knowing how the universe works
is not enough to tell us why it exists.
To find the answer to that question
would be to know the mind of God.
To learn more about "Stephen Hawking's Universe,"
visit PBS online at the internet address
on your screen.
-- captions by vitac -- burbank, pittsburgh, tampa, and washington, d.c.
"Stephen Hawking's Universe" was made possible
by Alfred P. Sloan foundation to enhance public understanding
of the role of science and technology,
the arthur vining davis foundations,
the corporation for public broadcasting,
and viewers like you.
Corporate funding is provided by Amgen,
unlocking the secrets of life through biotechnology.
At Amgen, we produce medicines
that improve people's lives today
and bring hope for tomorrow.