What Einstein Never Knew
Albert Einstein did not live to find the answer. NOVA follows a new generation of physicists in their search to explain the mystery of the universe.
Transcript
00:00At the beginning of time, at the instant of the Big Bang, there was a single all-embracing
00:16force of unparalleled power.
00:19As the universe cooled, this super force lost its unity and divided into the forces and
00:24particles of our universe.
00:26Today, physicists are searching for the basic law that could uncover that lost unity.
00:32In fact, this was the lifelong goal of the most famous physicist of our time, Albert
00:36Einstein.
00:37Einstein gave the world a new theory of gravity and produced the equation that revolutionized
00:44physics, E equals mc squared.
00:50Yet the greater part of his life was spent trying to extend his ideas into a complete
00:54description of all phenomena.
00:59Einstein did not succeed.
01:05But now, finally, we may be on the brink of uncovering for ourselves what Einstein never
01:11knew.
01:19Major funding for NOVA is provided by this station and other public television stations
01:23nationwide.
01:26Additional funding was provided by the Johnson & Johnson family of companies, supplying health
01:30care products worldwide.
01:36And Allied Corporation, a world leader in advanced technology products for the aerospace,
01:40automotive, chemicals, and electronics industries.
01:53In the beginning, when space and time started in the hot fireball we call the Big Bang,
02:15the whole universe could be described by a single, all-embracing law.
02:21But as time passed, the universe cooled, simplicity became complexity, and the familiar world
02:27developed of change and diversity.
02:34Today, the original simplicity has vanished from sight, but maybe it could be recaptured
02:43if the fundamental laws of matter could be worked out.
02:49The discovery of an all-embracing law is a goal which physicists have sought throughout
02:53history, a single, complete theory to explain all physical phenomena, life, the universe,
03:00and everything.
03:09According to a new generation of physicists, we may now be close to discovering that original
03:13simplicity, finding the all-embracing law which would tie all physics together.
03:24I think it's an enormously healthy time in physics.
03:28The controversies are very, very productive, and eventually this may work out, and we will
03:33find out what the real theory of the universe is.
03:39I think what happens here is that you have people who really feel that they are learning
03:46something about the universe here.
03:48People are excited.
03:49They feel that new physics is opening up.
03:53People want to leave their mark in physics, and they feel that, in fact, there is a chance
03:58here that this is important.
04:00Today's physicists are coming up with ever more daring theories, encompassing more fundamental
04:06ideas, and this approach is leading them farther away from direct experimental testing.
04:20In fact, physics may be facing a dilemma.
04:27As physicists finally approach the ultimate theory, so they may lose contact with the
04:31experimental tools that have traditionally unlocked nature's secrets.
04:35New machines for direct testing will require temperatures so high that they may be physically
04:40impossible to construct.
04:43And as the goal of unification gets ever nearer, physicists may have to rely more and more
04:48on the mathematical elegance and inner simplicity of their theories alone.
04:55If ever a scientist believed in the power of aesthetics to produce truth, it was Albert
04:59Einstein.
05:03He's most famous for the theory of general relativity, a totally new way of understanding
05:08gravity.
05:09Yet, the greater part of his working life was spent trying to extend his ideas into
05:13a complete description of all phenomena, as he called it, a unified field theory.
05:22In 1928, the equations of Einstein's latest attempt at unification were even posted in
05:27the windows of Selfridges, the famous London store.
05:31Crowds gathered to look at them.
05:38But Selfridges was overconfident.
05:40Einstein's equations for a unified theory never quite worked out.
05:47The most famous scientist in history died knowing that his life's goal was unrealized.
05:54But since Einstein, the search for a single fundamental theory has continued.
05:59It's a story that takes us to the limit of experiment.
06:03Deep underground, where giant tanks of water are waiting for evidence of an extremely rare
06:08occurrence, the decay of a proton.
06:12And out into the wider universe in search of missing neutrinos, thought to have been
06:16created 15 billion years ago by the Big Bang.
06:21And down into the innermost parts of the atom, where particle accelerators collide matter
06:25and antimatter in tiny recreations of the start of the universe.
06:31Science has known for a hundred years that all the objects in the world are made up of
06:35the same sort of particles.
06:38A tree is a complex arrangement of atoms and molecules, but all the constituent parts are
06:43known.
06:45Scaled down some thousand times, we see the individual cells and fibers.
06:50Smaller as much again are individual molecules.
06:54Each atom reveals layers of electrons around a nucleus of tightly packed protons and neutrons.
07:00And at the smallest level known, there are quarks, which make up each proton or neutron.
07:06And there are also electrons which orbit the nucleus.
07:11We can also look outwards to the farthest reaches of the universe.
07:15A million trees would barely span our own Earth.
07:18The Earth and solar system itself are but tiny specks within a complex of galaxies.
07:23And galaxies in their turn are mere dots in the full span of the universe.
07:30We can now trace the history of our universe back to one billionth of a second after the
07:35Big Bang, when the universe was a hot soup of fundamental particles and forces.
07:44Physicists regard each tiny particle found today as a fossil record of that explosive
07:49instant.
07:51But at the moment, the most important characters in the story are not the particles themselves,
07:55but the forces which hold matter together and are the source of all change and motion.
08:02Scientists today recognize four of them.
08:05Gravity is the dominant force.
08:07Nothing in the cosmos escapes it.
08:09It keeps the planets in their orbits and holds the galaxies together.
08:17The electromagnetic force is familiar to us as light and radio waves.
08:21It also binds atoms together into molecules and electrons to the nuclei of atoms.
08:27Gravity and electromagnetism were the only forces known until the 1940s, when two new
08:32forces were found, operating at the tiniest distances, actually within the nuclei of atoms.
08:40The weak force is responsible for the slow disintegration of the atomic nuclei, which
08:45causes radioactive decay.
08:47We can also see the force in action during the cataclysmic explosion of an aging star,
08:52a supernova.
08:59The strong force, also a recent discovery, actually holds the nucleus of the atom together,
09:05making ordinary matter possible.
09:07This force is so strong that the nucleus is a million times harder to break apart than
09:12the atom itself.
09:19The goal of an ultimate theory is to show that these four very different forces are
09:24in fact related.
09:26That in the distant fireball of the Big Bang, they were unified into one primal force.
09:35The belief is that as energy and temperature approach those of the Big Bang, the once separate
09:40forces blend, become equal in strength, and reveal their hidden unity.
09:47No known accelerator experiment will ever be able to journey into the far regions where
09:52all four forces are unified.
09:54The energies required are just too high.
09:57But there may be stepping stones which will point the way to a full synthesis.
10:02And in fact, one theory has already taken the first momentous step.
10:06A connection has been made between two of the forces, the electromagnetic and the weak
10:11force.
10:12A new monument has been added to the landscape.
10:17But it took over ten years for three theoretical physicists, each working independently, to
10:22sketch out just how these two forces were linked.
10:29In 1960, Sheldon Blaschow took the first step.
10:33Then Steven Weinberg and Abdus Salam expanded on his work in 1967.
10:39The mathematical model they developed is known as the Electroweak Theory.
10:43Their work was initially ignored because the theory did not yield testable results.
10:48However, slowly enough experimental evidence did accumulate so that the three were jointly
10:53awarded the Nobel Prize for Physics in 1979.
10:58The Nobel Prize is a distinguished award, but not definitive proof of a theory.
11:03There was more to be done.
11:08Weinberg himself knew what was needed to convince the skeptics among his peers.
11:13We have to do all sorts of things.
11:14So we have to discover the W and the Z boson, for example, which will be done in April in
11:19Geneva.
11:28Carlo Rubbia, an experimental physicist, took on the job of finding the W and Z bosons,
11:34two new subatomic particles predicted by the Electroweak Theory.
11:37We're now in the countdown.
11:40In 1982, the European Laboratory for Particle Physics in Geneva, known as CERN, was the
11:46site of a spectacular collaboration involving hundreds of the world's top research physicists.
11:53The particle accelerator at CERN was built to accelerate beams of protons around its
11:58four-mile circumference almost to the speed of light and then smash them against a fixed
12:03target.
12:04The extreme heat or high-energy states which result from these collisions yield traces
12:09of subatomic particles which can be seen in no other way.
12:14First proton injection.
12:17The problem was, in order to find the W and the Z particles, Rubbia and his colleagues
12:22knew they had to generate a collision that would create temperatures a hundred times
12:26higher than were currently possible.
12:29Second proton injection.
12:34Rather than smash the proton beams against a fixed target, Rubbia's inspiration was to
12:39use the same accelerator to guide a second beam of negatively charged antiprotons in
12:44the opposite direction.
12:47You must give us the last antiproton interlock condition and the antiprotons are in.
12:57Since the proton and the antiproton have exactly the same mass and equal but opposite charges,
13:03the magnets of the accelerator can guide them in equal but opposite directions and accelerate
13:08them both nearly to the speed of light.
13:17When these two particles collide, if the impact is just right, they annihilate each
13:22other in a great explosion.
13:28Much of the energy of the explosion is converted into matter, creating new particles that fly
13:33apart, leaving mere traces of their fleeting existence.
13:40It's from the direction, velocity and shape of these tracks that the particles themselves
13:45are deduced.
13:46This is a very spectacular event.
13:48You see a very energetic track emerging from the vertex here in this direction and it's
13:54emerging at a large angle to the instant proton-antiproton direction.
14:00This is exactly what we would expect if we had a W produced in the center here.
14:05The experiment not only proved the existence of the W and Z particles, but showed that
14:10they had exactly the mass predicted by the electroweak theory.
14:20In 1984, the Nobel Prize for Physics was shared this time by experimental physicist Carlo
14:26Rubbia and CERN's senior engineer, Simon van de Meur.
14:33In physics, theory and experiment are intimately connected.
14:37Here, theory provoked experiment.
14:40Inspired by the electroweak theory, the CERN team figured out how to expand the limits
14:44of technology.
14:49They were able to create a high-energy collision which allowed the two forces to display their
14:54common ancestry, just long enough to confirm two-fold unification.
15:01The internal consistency of the theory combined with experimental verification has led to
15:07an almost universal acceptance of the electroweak connection.
15:12But the goal is to unite all the forces.
15:15So the next step is to go beyond two-fold unification to develop a theory which predicts
15:20that at even higher energies, there is a more distant monument.
15:24One which brings the strong force into the scheme and unites it with the weak and electromagnetic
15:29into a three-fold link.
15:36It's unlikely any accelerator team of the future would be able to confirm such a theory.
15:41They would need a machine so powerful that with today's technology, it would have to
15:45be as large as the Earth itself.
15:48With dim prospects for such colossal machines, physicists may become ever more dependent
15:53on their theories alone.
15:58One important theoretical tool which is being used to unravel the link between forces and
16:03predict new particles is the concept of symmetry.
16:07Symmetry is a familiar idea from everyday life.
16:10We see it in nature and art.
16:12But in science, it has a slightly wider meaning.
16:15To best understand this, we must forget our preconceptions and embrace a new definition.
16:21A checkerboard remains a checkerboard even when the black and white squares are interchanged.
16:26This is the way to imagine symmetry in science.
16:29We transform a system in some way and it ends up looking the same.
16:33The symmetric ice crystal can be rotated.
16:36And although the frame is moved, the drawing still looks the same.
16:46Just like the checkerboard.
16:51This simple idea of symmetry has far-reaching results.
16:55To understand the whole universe, there must be laws which are true everywhere.
16:59On the moon, for example, and on Earth as well.
17:04That's a constraint on all theories.
17:06They must be symmetric between any two places.
17:12Einstein looked at the universe and imposed another symmetry.
17:16He required that the laws of nature be the same for an observer standing still as for
17:21someone moving at constant speed.
17:24This symmetry led to a revolution in thought and a new way of looking at space and time
17:28called special relativity.
17:31And out of this has come the famous formula E equals mc squared.
17:38But Einstein went one step further.
17:40He demanded that the laws of nature also be the same for an accelerating observer.
17:46He had recognized a new symmetry.
17:48He had seen how the effect of gravity on an object was indistinguishable from the effect
17:52of acceleration.
17:55This recognition enabled him to create one of the most beautiful scientific works of
17:58our time, Einstein's theory of general relativity, essentially the product of a simple idea of
18:06symmetry.
18:10But if there is as much symmetry in nature as physicists claim, why is it not more apparent?
18:16This can be understood by the principle of hidden symmetry.
18:20To see how symmetries can be hidden, let's think of an ordinary magnet.
18:25When we heat up the magnet to a very high temperature, it loses its magnetism and becomes
18:30a lump of metal, no north pole or south pole, uniform throughout.
18:36A tiny scientist living inside this lump of metal would see the individual magnetic particles
18:40as a random yet symmetrical arrangement.
18:44No matter how the magnet world was rotated, she would see the same pattern.
18:48To her, this is symmetry.
18:51But if we cool the magnet, its individual magnetic particles line up in a particular
18:55direction.
18:56The magnet chooses a north and south pole.
19:00Now as our scientist surveys her domain, in one direction she sees the blue ends of the
19:04magnet particles.
19:06And when the magnet rotates, she sees the red end instead.
19:10Although in the cold magnet there seems to be more order, in fact, the magnet has lost
19:15the symmetry of rotation.
19:18The perfect symmetry that had been obvious at high temperatures is now hidden.
19:24The laws of physics haven't changed, even though the state of the magnet has.
19:31Physicists believe, as would the formation of the north and south poles in a magnet,
19:35that the four forces came into being as the universe cooled, hiding the perfect symmetry
19:40of the Big Bang.
19:42Although the goal is to ultimately unify the four forces, they are finding that even threefold
19:47unification is a distant landmark.
19:50The theories which unite the strong, electromagnetic and weak forces are called Grand Unified Theories.
19:58There's no machine powerful enough to test them in the same way that the electroweak
20:02force was tested at CERN.
20:04But the Grand Unified Theories do make three concrete predictions about the existence of
20:09matter that don't require high energies for confirmation.
20:14If any one were found to be true, it would be strong evidence that physics is on the
20:18right track.
20:22The first, and perhaps most startling, is the prediction that the basic building block
20:26of matter, the proton, should decay.
20:29Such decay is predicted by the symmetry principle.
20:32It works like this.
20:34Different particles are affected by different forces.
20:37For example, quarks are affected by the strong force, which binds them into protons, while
20:42electrons feel only the electroweak force.
20:46So if these two forces are linked by symmetry, then the particles are as well.
20:50So quarks and electrons must be interchangeable.
21:00A proton is a combination of three quarks.
21:03If one were to be replaced by an electron, the other two remaining would no longer make
21:08up a proton, and the particle would literally fly apart.
21:14Since nearly everything in the universe is made up of protons, the unification theory
21:18implies that given enough time, our entire world will disintegrate.
21:23It sounds alarming, but the process is so rare that in this tank of water only one or
21:27two protons are expected to decay a month.
21:31The experimenters hope that by waiting and watching long enough, they'll be able to spot
21:35a proton breaking up and sending off photons, or tiny flashes of light, to the 2048 sensitive
21:42photo tubes lining the walls.
21:49It's a long wait.
21:50In fact, a team from the University of Michigan, the University of California at Irvine, and
21:55the Brookhaven Laboratory has been standing by to observe a decay since the summer of
22:001982.
22:02Okay, so we can then shut off this run.
22:06The snag is that cosmic rays may mimic the process.
22:10So the IMB team buries its experiment some 2,000 feet underground in the caves of a salt
22:16mine near Lake Erie.
22:18Several similar experiments have found homes in equally exotic surroundings.
22:23But even at these depths, some unwanted particles still get through.
22:31At the University of Michigan, computers are busy trying to spot the rare patterns
22:35of light that would signal proton decay.
22:43A reconstruction of exactly when each photo tube was hit reveals some quite distinctive
22:47features.
22:48But are they what's expected?
22:52Proton decay should be recognizable by characteristic back-to-back signals, the light from which
22:58will illuminate just a few photo tubes in any cross-section of the tank.
23:03There are two types of cosmic ray particles which produce signals that can confuse the
23:08experimenters.
23:09One of these is the muon, produced high in the atmosphere.
23:13Thousands of these penetrate the tank each day.
23:16Its signal appears as complete walls of photo tubes lit up in a continuous swath of light.
23:23The second offending particle, the neutrino, interacts with the water and produces a light
23:27pattern very similar to proton decay.
23:32Since 1982, millions of events have been recorded.
23:35Most are unwanted background.
23:37But what of the remainder?
23:38The experiment's gone extremely well.
23:41We have not found the expected events which were on the grand, the simplest version of
23:48grand unified theories.
23:50This is a little bit disappointing and somewhat embarrassing to the theoreticians.
23:54But I would say at this moment it doesn't rule them out, but it's a little bit embarrassing
23:57for them.
24:01So far, the evidence for proton decay remains inconclusive.
24:06The second prediction of the grand unified theories is the existence of an unusual particle
24:11called a magnetic monopole.
24:13Sheldon Blasho explains.
24:15When Maxwell made his theory that put together electricity and magnetism, he noticed something.
24:22He noticed that there could exist particles that have an electric charge that are the
24:27sources of electric fields.
24:29A few years after his theory, these particles were discovered.
24:33They are called electrons.
24:35There could also exist particles that are the sources of magnetic fields from which
24:39magnetic fields come.
24:41He imagined that those particles also exist.
24:44But it seems they don't.
24:46Or at least until the present day, nobody has ever found a particle from which magnetic
24:51field comes.
24:52If I may make a picture on this piece of cork, an electron, for example, E for electron,
25:02is a source of electric field.
25:04That means coming from it, there's an electric field that points out in all different directions.
25:10Now a magnetic monopole is exactly the same thing.
25:15It's a fundamental particle which is the source of magnetic field lines.
25:21A magnetic monopole, a hypothetical particle, from which magnetic lines of force would come
25:27out in all directions.
25:32Now the only kinds of magnetic systems we can make are things that look like this, magnets.
25:39Magnets are things that have a north pole and a south pole.
25:43They are, they do produce a magnetic field, but the magnetic field comes from one side
25:50and goes to the other.
25:52Has lines of force that look like this.
25:57Now what a magnetic monopole is, is a north pole without an associated south pole.
26:02So you might say that's simple, just break the magnet in half and you have a north pole
26:07and a south pole.
26:08But it doesn't work like that because a north pole is created here and a south pole is created
26:13here and you end up with a smaller magnet.
26:17You can imagine doing this again and again, continually cutting a magnet into smaller
26:22pieces.
26:23You finally end up with a single atom, which is also a magnet, but it too has a north pole
26:28on one side and a south pole on the other.
26:31You can tear the atom apart, you end up with an electron.
26:34The electron is also a magnet, but it has both a north pole and a south pole.
26:41According to three-fold unification, these monopoles would be very heavy particles, so
26:46heavy that current accelerators are unable to create them.
26:49You'd need an accelerator a hundred trillion times hotter than what we have today.
26:56There was an accelerator of just that kind once and only once in the history of the universe.
27:01The original Big Bang, the tremendous explosion from which our universe evolved and is still
27:08exploding, this explosion was of an immense energy, far beyond energy.
27:14Any energy we can produce or will produce in the laboratory.
27:17It was energetic enough to make magnetic monopoles, if there are such things.
27:23If such exotic particles do exist, where does one start to look for them?
27:28Do physicists have any guidelines?
27:30Now, the logic that is employed in this search is that which the French call the logic of
27:37the lamppost, which goes as follows.
27:40Suppose you go back to your home at night, a little drunk and walking, and when you get
27:45to your doorstep, you find that you have lost your keys.
27:48Where are you going to go back and look for your keys?
27:50Well, you will look for your keys under the lamppost, because should they be in the dark,
27:56you wouldn't find them anyway.
27:58The best place to find monopoles seems to be underground, where researchers also look
28:02for proton decay.
28:05Monopoles flying through matter are expected to trigger or catalyze the decay of a number
28:09of nucleons.
28:10Imagine a monopole moving through the detector, catalyzes one nucleon decay, catalyzes another
28:15nucleon decay, and so on.
28:18So we would see a sequence of nucleon decays, separated by a short time interval.
28:24And that's a very characteristic signal.
28:26We look for that, we haven't found any evidence for it.
28:30But the fact that no monopoles have been found is not conclusive evidence that the grand
28:34unified theories are wrong.
28:36After all, no one knows how many monopoles there are or where in the universe they might
28:41be.
28:45The third prediction from the grand unified theories concerns the ever-elusive neutrino.
28:51This particle, produced by nuclear reactions in the sun, was originally thought to have
28:55no mass at all, like a photon of light.
28:58But recent work suggests that it may have a mass after all.
29:03Some scientists are now going to great lengths to measure it.
29:06One of the best places to look for neutrinos is under the core of a pressurized water reactor.
29:12Such nuclear power generators provide an abundant and controlled source of neutrinos.
29:20If a neutrino was found to have any mass at all, it would support not only threefold unification,
29:25but also theories about the fate of the entire universe as well.
29:31Many neutrinos were left over from the Big Bang, and it is possible that they have clustered
29:36around galaxies and are flying like moons if they have a non-zero mass around a galaxy.
29:41So it is possible that the galaxies are actually ensembles of neutrinos, more than anything
29:47else with a little bit of ordinary matter in the middle.
29:52On the other hand, for the universe as a whole, you know that we believe it started in a Big
29:57Bang.
29:58We still see the galaxies flying away from each other as a consequence of this original
30:02bang.
30:03Now, there is a force opposing the separation of the galaxies, and that is the gravitational
30:07force of each galaxy onto each other that is trying to stop the expansion.
30:12And there are three possibilities.
30:14Either the explosion was so energetic that the galaxies will fly forever apart because
30:21the mass in between them is not enough to re-collapse them, or the in-between possibilities
30:26where the galaxies will separate till they eventually come to a stop.
30:31Or there is enough mass to have the galaxies eventually come back.
30:37Those are an open, a flat, or a closed universe.
30:40Now, if neutrinos do have masses, since we believe many of them were made in the Big
30:45Bang, about a thousand million neutrinos per atom of ordinary hydrogen, it is enough that
30:51they have a very, very tiny mass to contribute so much to the mass, overall mass of the universe,
30:57that the neutrinos themselves will pull the galaxies back eventually.
31:01So the fate of the universe depends on very few things, and one of them is whether neutrinos
31:06have a mass or they don't.
31:09Perhaps the most promising measurement of the neutrino mass comes from a Soviet experiment
31:14undertaken at the Moscow Institute for Theoretical and Experimental Physics.
31:19In 1984, they concluded that the neutrino seems indeed to have a mass one ten-thousandth
31:24that of an electron.
31:27To date, no one has been able to duplicate this experiment.
31:31The conclusions are tantalizing, but not as yet confirmed.
31:36The results of all the experiments on three-fold unification are so far inconclusive.
31:42No protons have yet decayed, no monopoles have come through our detectors, and the neutrino
31:47mass experiments remain tentative.
31:50It seems to a growing number of physicists that they should reject the constraints of
31:54the experimental lamplight, which allows them to look only in certain places.
31:59They believe that substantial further progress can only come about by seeking an even more
32:04ambitious four-fold unification of all the forces, including gravity.
32:09To do this, they have to imagine energies beyond even the still unconfirmed point of
32:14three-fold unification, because only there can one imagine that gravity will show any
32:19unity with the other forces.
32:22To go this far is not only to go way beyond experimental testing, but also to encounter
32:27immense difficulties in the theory.
32:29After all, the attempt to include gravity eluded even Einstein.
32:34But that story may have an ironic twist.
32:40In 1919, the very year that Einstein achieved world fame, Theodor Kaluza, a young German
32:46physicist, made a remarkable discovery.
32:51He took Einstein's equations of gravity and wrote them down as if they applied to a different
32:55world.
32:56Not the four-dimensional world of Einstein, but a mathematical universe with an extra
33:01fifth dimension.
33:04To his amazement, he discovered that he had actually, when rubbing off the fifth dimension,
33:14the fifth coordinate, explicitly from the equations, he found that he had written down
33:21not only the theory of Einstein's gravity in four dimensions, the normal gravity, but
33:27also Maxwell's electromagnetism on the right-hand side of the equations.
33:33And so this was the first unification of Maxwell's electromagnetism with Einstein's gravity,
33:39achieved by extending space and time to five dimensions rather than four.
33:46An incredible and a miraculous idea.
33:50In mathematics, an extra dimension is a matter of algebra.
33:54One dimension, a line, is represented by one number, x.
33:59A two-dimensional surface by two numbers.
34:03Ordinary three-dimensional space by three numbers.
34:07You can't draw another dimension because there's no room for an extra line, but we can add
34:12an extra letter.
34:13In fact, mathematics can be done in any number of dimensions.
34:17Human brains are not wired in the right way to imagine life with an extra dimension.
34:23We're in the same position as a two-dimensional flatlander.
34:27In his world, he cannot imagine our space.
34:30If we push a pencil through his plane, he can't know where it's come from.
34:34All he sees is a circle which grows out of nothing for no apparent reason.
34:39Only flatland mathematicians can imagine the pencil which caused the phenomenon.
34:46We can perform tricks for the flatlander.
34:48To him, this disk is permanently stuck inside the ring.
34:52But with an extra dimension, it can be picked up and moved, leaving the flatlander mystified.
34:59Calusa performed just as amazing a trick in physics by mathematically adding an extra dimension.
35:05It was quite obvious who should be told about his discovery.
35:08What Calusa did was he sent the paper to Einstein and asked him to get it published.
35:14And Einstein's reaction to this idea is in his letter.
35:19The idea that this can be achieved, that is to say the unification of electromagnetism
35:25and gravity can be achieved through a five-dimensional world,
35:29has never occurred to me and would seem to be altogether new.
35:33I like your idea at first sight very much.
35:37This was in April 1990.
35:41Then a week later, he writes again, raising a few, what now appear to us, rather trivial points or difficulties.
35:52There was always this, Einstein asked a question or made a suggestion and then my father did something about it,
36:04sent it to Einstein, Einstein repeated it, asked another question and so on.
36:11There are five or six letters of this sort.
36:17And then suddenly in October 1921, two and a half years later, he writes himself to Calusa saying,
36:28I am now having second thoughts about having restrained you from publishing your idea on a unification of gravitation and electricity two years ago.
36:37I wish I shall present your paper, if you wish, I shall present your paper to the academy after all.
36:43And then he did.
36:46Calusa's idea was picked up and improved by Oskar Klein in Sweden.
36:51But both men lived to see it become little more than an historical curiosity.
37:00Calusa's disappointment must have been enormous.
37:03At the moment when he thought he saw how to combine gravity and electromagnetism,
37:07it must have seemed impossible to him for it to be merely an accident.
37:14His son was a small boy of nine at the time and he used to sit in his father's study while he was working.
37:20Usually the father would work quietly by himself.
37:24But one day it was quite different.
37:27He sat completely still for several seconds and then he whistled very sharply and banged the table.
37:44He stood up but he remained completely motionless for several seconds.
37:52And then he began to hum the last part of an aria of Figaro.
38:14Equipped with the multidimensional world of Calusa and the guiding principle of symmetry,
38:42physicists have produced daring new theories that attempt to unify not only the four forces but all particles as well.
38:50Today, Calusa-Klein theories have been resurrected in a 10 or 11 dimensional form
38:55in connection with a new kind of symmetry which goes under the grandiose title of supersymmetry.
39:02There is hot debate as to whether it's the correct road for theoretical physics to follow.
39:07But at the moment, supersymmetry is one of the boldest attempts to produce a single theory of all forces and matter in the universe.
39:15In fact, supersymmetry goes even better than that because not only is it compatible with the unification of gravity,
39:23you can actually show that supersymmetry implies gravity.
39:27And in fact, if we didn't already know about Einstein's general theory of relativity, supersymmetry would force us to invent it.
39:35The followers of supersymmetry met in Bonn in 1984.
39:43They are here studying the mathematical foundations of a theory which is quite far from experimental verification.
39:51But the theories have commanded attention because of their internal beauty.
39:55Today, these ideas seem very abstract and belief in them requires a giant leap of faith.
40:01But as the ultimate judge of physics is mathematical consistency in combination with real world events,
40:07these physicists hope that the theory will eventually lead them to make contact with experiment.
40:17The ideas in the new theories seem to fit together elegantly like the pieces of a puzzle.
40:23One of the pieces is the multidimensional idea of Calusa and Klein.
40:28It's an extraordinary idea, but there are some physicists who believe we are living in a 10 or 11 dimensional world.
40:38The reason we don't notice the extra dimensions they claim is that they are curled up very small,
40:42so their effects are only felt indirectly.
40:46The universe may have started with 10 or 11 equal dimensions,
40:50but at some stage a number of them collapsed, leaving the three dimensions of space and one of time that we see today.
40:56If these ideas are right, then the history of the universe begins with just one thing,
41:02a multidimensional field which is the ancestor of all today's particles and forces.
41:06Quickly the cooling universe loses its extra dimensions.
41:10The single force splits into four and in 15 billion years we observe the results.
41:26There's one other thing that physicists demand of a fundamental law of the universe.
41:32It must provide a unique description of just one kind of world.
41:36This would mean that if science were in possession of the true fundamental theory,
41:40you could ask whether the laws of physics could have made the sky green and the trees blue.
41:44And the answer would be no.
41:48These things are not possible.
41:52The fundamental theory says that there is only one way for things to be.
41:56Some of the new theories seem to have that property of uniqueness.
42:00They achieve it because the constraints of symmetry narrow down the choices open to the scientists.
42:04Well, physicists are very fertile imaginations,
42:08and so there are lots of different theories they could think of
42:12which might correspond to the real world.
42:16And so to narrow down the choice, we like to invoke this idea of symmetry
42:20in the hope that we can eventually pin down the correct theory.
42:24And as a crude analogy, let's imagine that each one of these shapes
42:28represents a possible theory of elementary particles.
42:32Now, you'll notice that we've been careful to choose shapes
42:36that have the property that if you look at the shape of a particle,
42:40you'll see that the shape of a particle has a shape.
42:44Shapes that have the property that if you flip them around their vertical axis,
42:48you get back to where you started from.
42:52So in the spirit of this analogy, let's suppose that this represents
42:56the symmetry of the electroweak forces.
43:00We're fairly confident that the electroweak theory is a good theory,
43:04so we're not interested in theories that don't have that symmetry.
43:08But we want to go a step further.
43:12So by analogy, let's suppose that this corresponds to
43:16flipping around a horizontal axis.
43:20Now we see that some of the shapes remain the same, whereas other shapes do not.
43:24In other words, some theories have the symmetry of the strong interactions,
43:28other theories don't, and so let's eliminate
43:32all those theories that don't have the symmetry of the strong interactions.
43:36Well, we've managed to narrow down the choices a little,
43:40but there's still a long way to go.
43:44However, at this stage, it's no longer clear what the next symmetry should be.
43:48Suppose we say, for the sake of argument, that it's supersymmetry.
43:52Let's represent supersymmetry by rotation about a diagonal axis.
43:56Once again, some of the shapes remain the same,
44:00others do not, and so we can eliminate
44:04all those theories that don't obey the principle of supersymmetry.
44:08If, on the other hand, we demand maximal supersymmetry,
44:12that's to say, the most supersymmetry that the mathematics will allow,
44:16which we can represent by rotation about every conceivable axis,
44:20then we rule out all but one unique theory.
44:24The question, of course, is, have we painted ourselves into a corner?
44:28Is this one unique theory actually describing the world in which we live?
44:38All the proposed new theories are complicated.
44:50To believe in them, you have to be persuaded by their mathematical elegance.
44:54Not everybody is.
44:58Sheldon Glashow looks at these new developments with skepticism.
45:02It's just some kind of abstract elegance.
45:06In fact, I'm thankful to supersymmetry,
45:10because there are something like a thousand high-energy theoretical physicists in the world.
45:14A large fraction of these people are working on supersymmetry.
45:18That keeps them out of my hair and leaves some room for me to do other things
45:22which have a better chance of working out.
45:26Many of my friends have been doing supersymmetry for the past 20 years.
45:30It's a vast endeavor, it's a fascinating theory, it's an ingenious theory.
45:34It has accomplished, in terms of explaining phenomena, absolutely nothing.
45:40It does predict the existence of new particles in it.
45:44In fact, as you know, there are 17 particles in our bestiary at present in the standard theory.
45:50It doubles them. It says there are precisely 34, maybe more, fundamental particles.
45:56It gives them nice names.
46:00Ouinos and binos and flotinos and gluinos,
46:04sleptons and squarks.
46:08The trouble is that not one of these new predicted particles have been found.
46:12I like new theories that predict new particles that are found in the laboratory.
46:16I do not like new theories that predict all sorts of things
46:20which are not found and perhaps cannot be found.
46:24I don't share criticism because what really matters is not how the theory looks
46:28at the comparatively low energies that we study today.
46:32Low, that is, compared with the typical energy of the gravitational interaction.
46:36What really matters is whether the underlying fundamental theory,
46:40which we don't see in its pristine form at these comparatively low energies,
46:46whether that underlying theory is beautiful and simple.
46:50And when you come to supersymmetry and supergravity theories,
46:54even though the theory you end up with at low energies appears to be rather clumsy,
46:58doubling and so on, the actual underlying theory
47:02is the epitome of simplicity and elegance.
47:06Although supersymmetry is compelling to many theorists,
47:10in 1984 a new twist began to take hold.
47:14This theory, called superstring theory, proposes a ten-dimensional world
47:18but then adds a strange new ingredient.
47:22Particles are not points in space but rather one-dimensional strings.
47:26At large distances, these strings would still look like points.
47:30But at the tiniest distances imaginable, each particle would look and behave
47:34like the closed loop of a rubber band.
47:38According to superstring theory, there is a single fundamental interaction
47:42from which all particles and forces emanate.
47:46This interaction can be visualized as either two strings combining into one
47:50or one string dividing into two.
47:54It's the resulting vibration of the string that determines its specific properties,
47:58like mass or charge.
48:02For example, the string at rest may behave like an electron.
48:06If disturbed by colliding with another string, it begins oscillating.
48:10The vibrating string is now in a different internal state
48:14and so exhibits new attributes.
48:18It may have a different charge or even a different mass.
48:22To a distant observer, it seems like a totally different particle.
48:26Strangely enough, many of the mathematical problems
48:30that have plagued all preceding attempts at fourfold unification
48:34disappear with this picture of the universe.
48:38The ideas being explored by superstring theory have no chance of direct verification.
48:42So the only way for physicists to judge the quality of this theory
48:46is from its low energy predictions, mathematical consistency,
48:50and internal elegance.
48:56In physics, simplicity and elegance are allied to beauty.
49:00Keats' famous line, beauty is truth, truth beauty,
49:04is actually borne out in the practice of physics.
49:08It doesn't just say that the truth is beautiful.
49:12It says they are the same thing.
49:16If you have beauty, then you must have truth, and vice versa.
49:20This is what supersymmetrists hope about their theories,
49:24that truth is guaranteed by elegance.
49:28Einstein plainly felt that this had happened with his theory of general relativity.
49:32The problem is that it only takes
49:36one contradictory experiment to disprove a theory.
49:40And when the stage is reached where theory has gone beyond direct experimentation,
49:44scientists will be left wondering whether their ideas were beautiful enough.
49:48That's Abdus Salam's warning about
49:52Kaluza Klein and multidimensional theories.
49:56I must confess that one cannot say
50:00that the aesthetics of man are the same as the aesthetics of the Lord.
50:04They may be very, very different.
50:08I would not like to say that this is the final theory,
50:12but I would like it to be correct, if it's possible, to test it properly.
50:24Since 1983, the experiment which confirmed the electroweak theory
50:28has begun producing new data which doesn't fit in with any theory.
50:32News from CERN,
50:36announced by Carlo Rubio, is the observation of some strange new effects,
50:40some surprising anomalies.
50:44The events in question are characterized by an unpredicted imbalance
50:48in the particles produced, more off to one side than to the other.
50:52This cannot be reconciled by today's standard model,
50:56and if true, implies that the model may be incomplete.
51:00So far, there are about five very curious new types of phenomena
51:04that have been reported from CERN.
51:08Some of them are called zen events.
51:12They're events where particles come streaming out in one direction,
51:16nothing comes out of the other side, the sound of one hand clapping.
51:20It's a strange business, and these curious anomalies
51:24are not part of it. They strongly suggest to me
51:28that we may be missing something very important.
51:32Perhaps one possibility is another kind of force,
51:36a force above and beyond the weak interactions, the electromagnetic interactions,
51:40and the strong interactions, and different also from gravity.
51:44A new force, the fifth force. Perhaps we are just getting a dim view
51:48of the fifth and perhaps the most important new force
51:52of high energy from Carlo Rubbia and his work at CERN.
51:56If there's a fifth force, we'll have to put that together with the other forces.
52:00We'll have to make a fourfold unification before we can make
52:04a true unification of all the forces with gravity.
52:08Things might get a lot more complicated before they get simple.
52:12On the other hand, there is a truly remarkable possibility.
52:16Excitement is mounting that buried within the debris
52:20that produced the W and Z may lie the first traces of one of the
52:24extra particles predicted by supersymmetry.
52:28Could the new data from CERN be the first evidence
52:32of a photino, or a slepton, or a squark?
52:36Or could it be something that will force physicists to revise their ideas completely?
52:40I think it's highly improbable.
52:44It could be years before an answer is found.
52:48Physics and other puzzles may only come with the creation of even higher energy collisions
52:52involving even larger machines.
52:56The world of physics has plans which will take at least a decade to develop.
53:00Already under construction at CERN in Geneva
53:04is a large electron-positron ring measuring six miles across,
53:08which will be, when it is completed in 1988,
53:12the biggest machine on Earth.
53:18In the United States, plans are already underway
53:22for the superconducting supercollider, or SSC.
53:26This accelerator will cost $3 billion and, if ever built,
53:30will consist of a circular tunnel as much as 100 miles long.
53:38Superconducting magnet technology would drive and steer the particles
53:42on their epic journey, ending in collisions with energies as much as
53:4680 times as great as the events which are producing today's puzzles.
53:50People often come to me and they say,
53:54what is this that you're doing for?
53:58Why should the United States government spend millions and millions of dollars to build a new machine?
54:02Will it lead to a new kind of toothpaste or something like that?
54:06And I have to say to them that mostly the answer is no.
54:10What I usually say is this.
54:14There are animals in that they have curiosity.
54:18They look at the stars with wonder.
54:22We might try to teach dolphins and chimpanzees to speak,
54:26and sometimes we're successful, but they're sure not going to look at the sky
54:30and imagine constellations.
54:34This is the way in which people, or at least little children, differ from animals.
54:38Little children are curious. My kids ask me, where does the sun go at night
54:42to ask questions like this.
54:46Later in life, they are trained not to ask questions of this kind.
54:50Not all of them. Some of them maintain this primordial human quality of curiosity.
54:54Some of these people become artists, like the man who made that.
54:58Some become composers. Some become physicists. Some become astronomers.
55:02These people, in a sense, have kept the faith.
55:06They really want to know what's going on.
55:12It's hard to imagine a time when all our questions will be answered.
55:16When there are no more puzzles to solve.
55:20When most physicists are agreed on the nature of the universe.
55:24And even if they think they've found out,
55:28how will they know if they are right?
55:32As long as these questions remain,
55:36the search for the ultimate theory will continue.
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