- 2 days ago
Category
📚
LearningTranscript
00:10At the beginning of time, at the instant of the Big Bang, there was a single all-embracing
00:16force of unparalleled power. As the universe cooled, this superforce lost its unity and
00:22divided into the forces and particles of our universe. Today, physicists are searching
00:28for the basic law that could uncover that lost unity. In fact, this was the lifelong goal
00:33of the most famous physicist of our time, Albert Einstein. Einstein gave the world a
00:40new theory of gravity and produced the equation that revolutionized physics, E equals mc squared.
00:49Yet, the greater part of his life was spent trying to extend his ideas into a complete
00:54description of all phenomena. Einstein did not succeed.
01:04But now, finally, we may be on the brink of uncovering for ourselves what Einstein never knew.
01:18Major funding for NOVA is provided by this station and other public television stations nationwide.
01:25Additional funding was provided by the Johnson & Johnson family of companies, supplying health
01:30health care products worldwide. And Allied Corporation, a world leader in advanced technology products
01:39for the aerospace, automotive, chemicals and electronics industries.
01:43major funding for NOVA is provided by the Johnson & Johnson family of companies.
02:09In the beginning, when space and time started in the hot fireball world, we were able to
02:13see what we call the Big Bang. The whole universe could be described by a single, all-embracing law.
02:20But as time passed, the universe cooled. Simplicity became complexity, and the familiar world developed
02:27of change and diversity.
02:37Today, the original simplicity has vanished from sight, but maybe it could be recaptured if the fundamental
02:43laws of matter could be worked out.
02:48The discovery of an all-embracing law is a goal which physicists have sought throughout history.
02:53A single, complete theory to explain all physical phenomena, life, the universe, and everything.
03:08According to a new generation of physicists, we may now be close to discovering that original simplicity,
03:14finding the all-embracing law which would tie all physics together.
03:23I think it's an enormously healthy time in physics. The controversies are very, very productive, and eventually, this may work
03:32out.
03:32And we will find out what the real theory of the universe is.
03:38I think what happens here is that you have people who really feel that they are learning something about the
03:46universe here.
03:47People are excited. They feel that new physics is opening up.
03:52People want to leave their mark in physics, and they feel that, in fact, there is a chance here that
03:58this is important.
04:00Today's physicists are coming up with ever more daring theories, encompassing more fundamental ideas.
04:07And this approach is leading them farther away from direct experimental testing.
04:20In fact, physics may be facing a dilemma.
04:26As physicists finally approach the ultimate theory, so they may lose contact with the experimental tools that have traditionally unlocked
04:34nature's secrets.
04:34New machines for direct testing will require temperatures so high that they may be physically impossible to construct.
04:42And, as the goal of unification gets ever nearer, physicists may have to rely more and more on the mathematical
04:48elegance and inner simplicity of their theories alone.
04:54If ever a scientist believed in the power of aesthetics to produce truth, it was Albert Einstein.
05:03He's most famous for the theory of general relativity, a totally new way of understanding gravity.
05:09Yet, the greater part of his working life was spent trying to extend his ideas into a complete description of
05:14all phenomena, as he called it, a unified field theory.
05:21In 1928, the equations of Einstein's latest attempt at unification were even posted in the windows of Selfridges, the famous
05:29London store.
05:30Crowds gathered to look at them.
05:37But Selfridges was overconfident.
05:40Einstein's equations for a unified theory never quite worked out.
05:46The most famous scientist in history died knowing that his life's goal was unrealized.
05:53But since Einstein, the search for a single fundamental theory has continued.
05:58It's a story that takes us to the limit of experiment.
06:02Deep underground, where giant tanks of water are waiting for evidence of an extremely rare occurrence, the decay of a
06:09proton.
06:11And out into the wider universe in search of missing neutrinos, thought to have been created 15 billion years ago
06:18by the Big Bang.
06:20And down into the innermost parts of the atom, where particle accelerators collide matter and antimatter in tiny recreations of
06:28the start of the universe.
06:31Science has known for a hundred years that all the objects in the world are made up of the same
06:35sort of particles.
06:37A tree is a complex arrangement of atoms and molecules, but all the constituent parts are known.
06:44Scaled down some thousand times, we see the individual cells and fibers.
06:49Smaller as much again are individual molecules.
06:53Each atom reveals layers of electrons around a nucleus of tightly packed protons and neutrons.
06:59And at the smallest level known, there are quarks, which make up each proton or neutron.
07:05And there are also electrons which orbit the nucleus.
07:10We can also look outwards to the farthest reaches of the universe.
07:14A million trees would barely span our own Earth.
07:17The 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 Big Bang,
07:36when 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 instant.
07:50But 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.
08:01Scientists today recognize four of them.
08:04Gravity is the dominant force. Nothing in the cosmos escapes it.
08:09It keeps the planets in their orbits and holds the galaxies together.
08:16The electromagnetic force is familiar to us as light and radio waves.
08:20It also binds atoms together into molecules and electrons to the nuclei of atoms.
08:26Gravity and electromagnetism were the only forces known until the 1940s,
08:31when two new forces were found, operating at the tiniest distances,
08:36actually within the nuclei of atoms.
08:39The weak force is responsible for the slow disintegration of the atomic nuclei,
08:44which causes radioactive decay.
08:46We can also see the force in action during the cataclysmic explosion of an aging star,
08:52a supernova.
08:58The strong force, also a recent discovery,
09:01actually holds the nucleus of the atom together,
09:04making ordinary matter possible.
09:07This force is so strong that the nucleus is a million times harder to break apart than the atom itself.
09:19The goal of an ultimate theory is to show that these four very different forces are, in fact, related.
09:25That in the distant fireball of the Big Bang, they were unified into one primal force.
09:34The belief is that as energy and temperature approach those of the Big Bang,
09:39the once separate forces blend, become equal in strength, and reveal their hidden unity.
09:46No known accelerator experiment will ever be able to journey into the far regions where all four forces are unified.
09:53The energies required are just too high.
09:56But there may be stepping stones which will point the way to a full synthesis.
10:01And 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 force.
10:12A new monument has been added to the landscape.
10:16But it took over ten years for three theoretical physicists, each working independently,
10:22to sketch out just how these two forces were linked.
10:28In 1960, Sheldon Glashow took the first step.
10:32Then Steven Weinberg and Abdus Salam expanded on his work in 1967.
10:37The 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 awarded the Nobel Prize for Physics in
10:551979.
10:57The Nobel Prize is a distinguished award, but not definitive proof of a theory.
11:03There was more to be done.
11:07Reinberg 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.
11:27Carlo Rubia, an experimental physicist, took on the job of finding the W and Z bosons.
11:33Two new subatomic particles predicted by the Electroweak theory.
11:38We're now in the countdown.
11:40In 1982, the European Laboratory for Particle Physics in Geneva, known as CERN,
11:45was the site 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 four-mile circumference almost to the
12:00speed of light and then smash them against a fixed target.
12:03The extreme heat or high-energy states which result from these collisions yield traces of subatomic particles which can be
12:10seen in no other way.
12:13First proton injection.
12:16The problem was, in order to find the W and the Z particles, Rubia and his colleagues knew they had
12:22to generate a collision that would create temperatures a hundred times higher than were currently possible.
12:28Second proton injection.
12:33Rather than smash the proton beams against a fixed target, Rubia's inspiration was to use the same accelerator to guide
12:40a second beam of negatively charged antiprotons in the opposite direction.
12:47You must give us the last antiproton interlock condition and the antiprotons are in.
12:56Since 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 them both nearly to the
13:10speed of light.
13:16When these two particles collide, if the impact is just right, they annihilate each other in a great explosion.
13:27Much of the energy of the explosion is converted into matter, creating new particles that fly apart, leaving mere traces
13:35of their fleeting existence.
13:39It's from the direction, velocity and shape of these tracks that the particles themselves are deduced.
13:45This is a very spectacular event.
13:48You see a very energetic track emerging from the vertex here in this direction.
13:53And it's emerging at a large angle to the instant proton-antiproton direction.
13:59This is exactly what we would expect if we had a W produced in the center here.
14:04The experiment not only proved the existence of the W and Z particles, but showed that they had exactly the
14:11mass predicted by the electroweak theory.
14:14It's a high mass stuff.
14:16Very high mass.
14:17The transverse energy is small, but it's only 10 G.
14:19In 1984, the Nobel Prize for Physics was shared this time by experimental physicist Carlo Rubia and CERN's senior engineer
14:28Simon Vandermeer.
14:32In physics, theory and experiment are intimately connected.
14:36Here, theory provoked experiment.
14:39Inspired by the electroweak theory, the CERN team figured out how to expand the limits of technology.
14:48They were able to create a high energy collision, which allowed the two forces to display their common ancestry.
14:56Just long enough to confirm two-fold unification.
15:01The internal consistency of the theory combined with experimental verification has led to an almost universal acceptance of the electroweak
15:09connection.
15:11But the goal is to unite all the forces.
15:14So the next step is to go beyond two-fold unification to develop a theory which predicts that at even
15:20higher energies, there is a more distant monument.
15:23One which brings the strong force into the scheme and unites it with the weak and electromagnetic into a three
15:30-fold link.
15:35It'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 be as large as the
15:46Earth itself.
15:47With dim prospects for such colossal machines, physicists may become ever more dependent on their theories alone.
15:57One important theoretical tool which is being used to unravel the link between forces and predict new particles is the
16:04concept of symmetry.
16:06Symmetry is a familiar idea from everyday life. We see it in nature and art.
16:11But in science it has a slightly wider meaning.
16:14To best understand this, we must forget our preconceptions and embrace a new definition.
16:20A checkerboard remains a checkerboard even when the black and white squares are interchanged.
16:26This is the way to imagine symmetry in science.
16:28We 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 has moved, the drawing still looks the same.
16:45Just like the checkerboard.
16:50This simple idea of symmetry has far-reaching results.
16:54To understand the whole universe, there must be laws which are true everywhere.
16:59On the moon, for example.
17:01And on Earth as well.
17:03That'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.
17:15He required that the laws of nature be the same for an observer standing still
17:20as for someone moving at constant speed.
17:23This symmetry led to a revolution in thought
17:26and a new way of looking at space and time called special relativity.
17:30And out of this has come the famous formula E equals MC squared.
17:37But Einstein went one step further.
17:40He demanded that the laws of nature also be the same for an accelerating observer.
17:45He had recognized a new symmetry.
17:47He had seen how the effect of gravity on an object
17:50was indistinguishable from the effect of acceleration.
17:54This recognition enabled him to create one of the most beautiful scientific works of our time.
18:00Einstein's theory of general relativity.
18:02Essentially the product of the simple idea of symmetry.
18:09But if there is as much symmetry in nature as physicists claim,
18:13why is it not more apparent?
18:15This can be understood by the principle of hidden symmetry.
18:19To see how symmetries can be hidden, let's think of an ordinary magnet.
18:24When we heat up the magnet to a very high temperature,
18:27it loses its magnetism and becomes a lump of metal.
18:30No north pole or south pole.
18:33Uniform throughout.
18:35A tiny scientist living inside this lump of metal
18:38would see the individual magnetic particles as a random yet symmetrical arrangement.
18:43No matter how the magnet world was rotated, she would see the same pattern.
18:48To her, this is symmetry.
18:50But if we cool the magnet, its individual magnetic particles line up in a particular direction.
18:56The magnet chooses a north and south pole.
18:59Now, as our scientist surveys her domain,
19:02in one direction she sees the blue ends of the magnet particles.
19:05And when the magnet rotates, she sees the red end instead.
19:10Although in the cold magnet there seems to be more order,
19:13in fact, the magnet has lost the symmetry of rotation.
19:17The perfect symmetry that had been obvious at high temperatures is now hidden.
19:23The laws of physics haven't changed.
19:27Even though the state of the magnet has.
19:30Physicists believe, as with the formation of the north and south poles in a magnet,
19:34that the four forces came into being as the universe cooled,
19:38hiding the perfect symmetry of the Big Bang.
19:41Although the goal is to ultimately unify the four forces,
19:45they are finding that even three-fold unification is a distant landmark.
19:49The theories which unite the strong electromagnetic and weak forces are called grand unified theories.
19:57There's no machine powerful enough to test them in the same way that the electroweak force was tested at CERN.
20:04But the grand unified theories do make three concrete predictions about the existence of matter
20:09that don't require high energies for confirmation.
20:13If any one were found to be true, it would be strong evidence that physics is on the right track.
20:21The first and perhaps most startling is the prediction that the basic building block of matter, the proton, should decay.
20:29Such decay is predicted by the symmetry principle.
20:32It works like this.
20:33Different particles are affected by different forces.
20:36For example, quarks are affected by the strong force, which binds them into protons,
20:42while electrons feel only the electroweak force.
20:44So 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 up a proton,
21:08and the particle would literally fly apart.
21:13Since nearly everything in the universe is made up of protons,
21:17the unification theory implies that given enough time, our entire world will disintegrate.
21:22It sounds alarming, but the process is so rare that in this tank of water only one or two protons
21:28are expected to decay a month.
21:31The experimenters hope that by waiting and watching long enough, they'll be able to spot a proton breaking up and
21:37sending off photons,
21:38or tiny flashes of light, to the 2048 sensitive photo tubes lining the walls.
21:48It's a long wait.
21:50In fact, a team from the University of Michigan, the University of California at Irvine, and the Brookhaven Laboratory,
21:56has been standing by to observe a decay since the summer of 1982.
22:01Okay, so we can then shut off this run.
22:05The snag is that cosmic rays may mimic the process.
22:09So the IMB team buries its experiment some 2,000 feet underground in the caves of a salt mine near
22:16Lake Erie.
22:17Several similar experiments have found homes in equally exotic surroundings.
22:22But even at these depths, some unwanted particles still get through.
22:30At the University of Michigan, computers are busy trying to spot the rare patterns of light that would signal proton
22:36decay.
22:42A reconstruction of exactly when each photo tube was hit reveals some quite distinctive features.
22:48But are they what's expected?
22:52Proton decay should be recognizable by characteristic back-to-back signals,
22:57the light from which will illuminate just a few photo tubes in any cross section of the tank.
23:02There are two types of cosmic ray particles which produce signals that can confuse the experimenters.
23:08One 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.
23:22The second offending particle, the neutrino, interacts with the water and produces a light pattern very similar to proton decay.
23:31Since 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.
23:41The experiment's gone extremely well.
23:41We have not found the expected events which were on the grand, the simplest version of grand 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 for them.
24:00So far, the evidence for proton decay remains inconclusive.
24:05The second prediction of the grand unified theories is the existence of an unusual particle called 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 sources of electric fields.
24:29A few years after his theory, these particles were discovered.
24:32They are called electrons.
24:34There could also exist particles that are the sources of magnetic fields, from which magnetic fields come.
24:41Imagine 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 field comes.
24:53If I may make a picture on this quark.
24:58An electron, for example, E for electron, is a source of electric field.
25:03That 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.
25:14It's a fundamental particle which is the source of magnetic field lines.
25:20A magnetic monopole, a hypothetical particle, from which magnetic lines of force would come out in all directions.
25:32Now, the only kinds of magnetic systems we can make are things that look like this.
25:38Magnets. Magnets are things that have a north pole and a south pole.
25:42They are, they do produce a magnetic field, but the magnetic field comes from one side and goes to the
25:50other.
25:51Has lines of force that look like this.
25:56Now, 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 and a
26:07south pole.
26:07But it doesn't work like that, because a north pole is created here and a south pole is created here.
26:13You end up with a smaller magnet.
26:16You can imagine doing this again and again, continually cutting a magnet into smaller pieces.
26:22You 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.
26:40According to three-fold unification, these monopoles would be very heavy particles.
26:45So heavy that current accelerators are unable to create them.
26:49You'd need an accelerator a hundred trillion times hotter than what we have today.
26:55There was an accelerator of just that kind once and only once in the history of the universe.
27:00The original Big Bang, the tremendous explosion from which our universe evolved and is still exploding, this explosion was of
27:11an immense energy, far beyond energy, any energy we can produce or will produce in the laboratory.
27:17It was energetic enough to make magnetic monopoles if there are such things.
27:22If such exotic particles do exist, where does one start to look for them? Do physicists have any guidelines?
27:30Now the logic that is employed in this search is that which the French call the logic of the lamppost,
27:37which goes as follows.
27:39Suppose you go back to your home at night, a little drunk and walking, and when you get to your
27:45doorstep, you find that you have lost your keys.
27:47Where are you going to go back and look for your keys? Well, you will look for your keys under
27:52the lampposts, because should they be in the dark, you wouldn't find them anyway.
27:57The best place to find monopoles seems to be underground, where researchers also look for proton decay.
28:04Monopoles flying through matter are expected to trigger or catalyze the decay of a number of nucleons.
28:10Imagine a monopole moving through the detector, catalyzes one nucleon decay, catalyzes another nucleon decay, and so on.
28:17So we would see a sequence of nucleon decays separated by a short time interval.
28:23And that's a very characteristic signal. We look for that. We haven't found any evidence for it.
28:29But the fact that no monopoles have been found is not conclusive evidence that the Grand Unified Theories are wrong.
28:36After all, no one knows how many monopoles there are or where in the universe they might be.
28:44The third prediction from the Grand Unified Theories concerns the ever-elusive neutrino.
28:50This particle, produced by nuclear reactions in the sun, was originally thought to have no mass at all, like a
28:57photon of light.
28:58But recent work suggests that it may have a mass after all.
29:02Some scientists are now going to great lengths to measure it.
29:05One of the best places to look for neutrinos is under the core of a pressurized water reactor.
29:11Such nuclear power generators provide an abundant and controlled source of neutrinos.
29:19If a neutrino was found to have any mass at all, it would support not only three-fold unification,
29:25but also theories about the fate of the entire universe as well.
29:30Many neutrinos were left over from the Big Bang, and it is possible that they have clustered around galaxies,
29:37and are flying like moons if they have a non-zero mass around the galaxy.
29:40So it is possible that the galaxies are actually ensembles of neutrinos, more than anything else,
29:47with a little bit of ordinary matter in the middle.
29:51On the other hand, for the universe as a whole, you know that we believe it started in a Big
29:57Bang.
29:57We still see the galaxies flying away from each other as a consequence of this original bank.
30:02Now, there is a force opposing the separation of the galaxies,
30:06and that is the gravitational force of each galaxy onto each other,
30:09that 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,
30:20because the mass in between them is not enough to recollapse them,
30:24or the in-between possibilities where the galaxies will separate till they eventually come to stop.
30:30Or there is enough mass to have the galaxies eventually come back.
30:36Those 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 Bang,
30:46about a thousand million neutrinos per atom of ordinary hydrogen,
30:50it is enough that they have a very, very tiny mass,
30:53to 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,
31:04and one of them is whether neutrinos have 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.
31:18In 1984, they concluded that the neutrino seems indeed to have a mass one ten-thousandth that of an electron.
31:27To date, no one has been able to duplicate this experiment.
31:30The conclusions are tantalizing, but not as yet confirmed.
31:35The results of all the experiments on three-fold unification are so far inconclusive.
31:41No protons have yet decayed.
31:43No monopoles have come through our detectors,
31:46and the neutrino mass experiments remain tentative.
31:49It seems to a growing number of physicists that they should reject the constraints of the experimental lamplight,
31:55which allows them to look only in certain places.
31:58They believe that substantial further progress can only come about
32:02by seeking an even more ambitious 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 three-fold unification,
32:16because only there can one imagine that gravity will show any unity with the other forces.
32:21To go this far is not only to go way beyond experimental testing, but also to encounter immense difficulties in
32:28the theory.
32:29After all, the attempt to include gravity eluded even Einstein.
32:33But that story may have an ironic twist.
32:39In 1919, the very year that Einstein achieved world fame,
32:44Theodore Calusa, a young German physicist, made a remarkable discovery.
32:50He took Einstein's equations of gravity and wrote them down as if they applied to a different world.
32:56Not the four-dimensional world of Einstein, but a mathematical universe with an extra fifth dimension.
33:03To his amazement, he discovered that he had actually, when rubbing off the fifth dimension, the fifth coordinate, explicitly from
33:17the equations,
33:18he found that he had written down not only the theory of Einstein's gravity in four dimensions, the normal gravity,
33:26but also Maxwell's electromagnetism on the right-hand side of the equations.
33:32And 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.
33:49In mathematics, an extra dimension is a matter of algebra.
33:53One 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.
34:11But we can add an 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.
34:22We'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.
34:45We can perform tricks for the flatlander.
34:48To him, this disc 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.
35:04It was quite obvious who should be told about his discovery.
35:07What 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.
35:18The idea that this can be achieved, that is to say the unification of electromagnetism and gravity can be achieved
35:27through 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.
35:51There was always this, Einstein asked a question or made a suggestion and then my father did something about it,
36:03sent it to Einstein, Einstein repeated or asked another question and so on.
36:11There are five or six letters of this sort.
36:16And 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
36:34electricity 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.
36:45Calusa's idea was picked up and improved by Oskar Klein in Sweden.
36:50But both men lived to see it become little more than an historical curiosity.
37:00Calusa's disappointment must have been enormous.
37:02At 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.
37:13His son was a small boy of nine at the time and he used to sit in his father's study
37:18while he was working.
37:19Usually the father would work quietly by himself.
37:23But one day it was quite different.
37:28He sat completely still for several seconds.
37:34And then he whisked very sharply and banged the table.
37:43And he stood up and...
37:46But he remained completely motionless for several seconds.
37:51And then he began to...
37:57And then he began to...
37:58The...
37:59An area...
38:01The last part of an area...
38:04Of Figaro.
38:05So...
38:06So...
38:08Yeah,
38:09And then...
38:10That's...
38:12That's...
38:13That's...
38:17That's...
38:18That's...
38:29It's...
38:37Equipped with the multidimensional world of Kaluza and the guiding principle of symmetry,
38:42physicists have produced daring new theories that attempt to unify not only the four forces,
38:47but all particles as well.
38:50Today, Kaluza-Klein theories have been resurrected in a 10 or 11-dimensional form
38:55in connection with a new kind of symmetry,
38:57which goes under the grandiose title of supersymmetry.
39:01There is hot debate as to whether it's the correct road for theoretical physics to follow,
39:06but at the moment, supersymmetry is one of the boldest attempts
39:10to produce a single theory of all forces and matter in the universe.
39:15In fact, supersymmetry goes even better than that
39:18because not only is it compatible with the unification of gravity,
39:22you can actually show that supersymmetry implies gravity.
39:27And in fact, if we didn't already know about Einstein's general theory of relativity,
39:33supersymmetry would force us to invent it.
39:38The followers of supersymmetry met in Bonn in 1984.
39:45They are here studying the mathematical foundations of a theory
39:49which is quite far from experimental verification,
39:52but the theories have commanded attention because of their internal beauty.
39:57Today, these ideas seem very abstract and belief in them requires a giant leap of faith.
40:03But as the ultimate judge of physics is mathematical consistency in combination with real-world events,
40:10these physicists hope that the theory will eventually lead them to make contact with experiment.
40:19The ideas in the new theories seem to fit together elegantly, like the pieces of a puzzle.
40:25One of the pieces is the multidimensional idea of Kaluza and Klein.
40:29It's an extraordinary idea, but there are some physicists who believe we are living in a ten or eleven-dimensional
40:35world.
40:38The reason we don't notice the extra dimensions, they claim, is that they are curled up very small,
40:44so their effects are only felt indirectly.
40:47The universe may have started with ten or eleven equal dimensions,
40:50but at some stage a number of them collapsed,
40:53leaving the three dimensions of space and one of time that we see today.
40:58If these ideas are right, then the history of the universe begins with just one thing,
41:03a multidimensional field which is the ancestor of all today's particles and forces.
41:09Quickly, the cooling universe loses its extra dimensions.
41:12The single force splits into four, and in 15 billion years, we observe the results.
41:33There's one other thing that physicists demand of a fundamental law of the universe.
41:38It must provide a unique description of just one kind of world.
41:42This would mean that if science were in possession of the true fundamental theory,
41:47you could ask whether the laws of physics could have made the sky green and the trees blue,
41:53and the answer would be no.
41:54These things are not possible.
41:57The fundamental theory says that there is only one way for things to be.
42:02Some of the new theories seem to have that property of uniqueness.
42:06They achieve it because the constraints of symmetry
42:09narrow down the choices open to the scientists.
42:14Well, physicists have very fertile imaginations,
42:17and so there are lots of different theories they could think of
42:20which might correspond to the real world.
42:23And so to narrow down the choice,
42:25we like to invoke this idea of symmetry
42:27in the hope that we can eventually pin down the correct theory.
42:32And as a crude analogy,
42:33let's imagine that each one of these shapes represents a possible theory of elementary particles.
42:40Now you'll notice that we've been careful to choose shapes that have the property that if you flip them around
42:47their 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 the symmetry of the electra-weak forces.
42:58We're fairly confident that the electra-weak theory is a good theory,
43:02so we're not interested in theories that don't have that symmetry.
43:06But we want to go a step further.
43:09We also want to incorporate the symmetry of the strong interactions.
43:12So, by analogy, let's suppose that this corresponds to flipping around a horizontal axis.
43:19Now we see that some of the shapes remain the same, whereas other shapes do not.
43:25In other words, some theories have the symmetry of the strong interactions, other theories don't.
43:31And so let's eliminate all those theories that don't have the symmetry of the strong interactions.
43:36Well, we've managed to narrow down the choices a little, but we've still a long way to go.
43:42However, at this stage, it's no longer clear what the next symmetry should be.
43:47Suppose we say, for the sake of argument, that it's supersymmetry.
43:51Let's represent supersymmetry by rotation about a diagonal axis.
43:57Once again, some of the shapes remain the same.
44:01Others do not.
44:02And so we can eliminate all those theories that don't obey the principle of supersymmetry.
44:10If, on the other hand, we demand maximal supersymmetry,
44:13that's to say the most supersymmetry that the mathematics will allow,
44:17which we can represent by rotation about every conceivable axis,
44:22then we rule out all but one unique theory.
44:26The question, of course, is, have we painted ourselves into a corner?
44:30Is this one unique theory actually describing the world in which we live?
44:47All the proposed new theories are complicated.
44:51To believe in them, you have to be persuaded by their mathematical elegance.
44:55Not everybody is.
44:59Sheldon Glashow looks at these new developments with skepticism.
45:04It's just some kind of abstract elegance.
45:07In fact, I'm thankful to supersymmetry
45:09because there are something like a thousand high-energy theoretical physicists in the world.
45:14A large fraction of these people are working on supersymmetry.
45:17That keeps them out of my hair,
45:19leaves some room for me to do other things which have a better chance of working out.
45:25Many of my friends have been doing supersymmetry for the past 20 years.
45:29It's a vast endeavor.
45:31It's a fascinating theory.
45:33It's an ingenious theory.
45:34It has accomplished, in terms of explaining phenomena, absolutely nothing.
45:41It does predict the existence of new particles.
45:44In fact, as you know, there are 17 particles in our bestiary at present,
45:49in the standard theory, it doubles them.
45:52It says there are precisely 34, maybe more, fundamental particles.
45:56It gives them nice names.
45:59Weenos and Beenos and Fotinos and Gluenos,
46:03Sleptons and Squarks.
46:05The trouble is that not one of these new predicted particles have been found.
46:10I like new theories that predict new particles that are found in the laboratory.
46:14I do not like new theories that predict all sorts of things
46:18which are not found and perhaps cannot be found.
46:22On reflection, I don't think this is really a fair criticism,
46:26because what really matters is not how the theory looks
46:29at the comparatively low energies that we study today,
46:33low, that is, compared with the typical energy of the gravitational interaction.
46:37What really matters is whether the underlying fundamental theory,
46:41which we don't see in its pristine form at these comparatively low energies,
46:47whether that underlying theory is beautiful and simple.
46:51And when you come to supersymmetry and supergravity theories,
46:54even though the theory you end up with at low energies
46:57appears to be rather clumsy, doubling and so on,
47:01the actual underlying theory is the epitome of simplicity and elegance.
47:07Although supersymmetry is compelling to many theorists,
47:11in 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,
47:33each particle would look and behave like 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.
47:45This 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,
47:59like 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.
48:13The vibrating string is now in a different internal state,
48:17and so exhibits new attributes.
48:19It may have a different charge, or even a different mass.
48:22To a distant observer, it seems like a totally different particle.
48:27Strangely enough, many of the mathematical problems
48:30that have plagued all preceding attempts at four-fold unification
48:33disappear with this picture of the universe.
48:37But the ideas being explored by superstring theory
48:41have no chance of direct verification,
48:43so the only way for physicists to judge the quality of this theory
48:46is from its low-energy predictions,
48:49mathematical consistency, and internal elegance.
48:56In physics, simplicity and elegance are allied to beauty.
49:00Keats' famous line,
49:01Beauty is truth, truth beauty,
49:03is actually borne out in the practice of physics.
49:06It doesn't just say that the truth is beautiful.
49:09It says they are the same thing.
49:11If you have beauty, then you must have truth,
49:14and vice versa.
49:16This is what supersymmetrists hope about their theories,
49:19that truth is guaranteed by elegance.
49:23Einstein plainly felt that this had happened
49:25with his theory of general relativity.
49:27He declared it too beautiful to be false.
49:34The problem is that it only takes one contradictory experiment
49:38to disprove a theory.
49:39And when the stage is reached
49:41where theory has gone beyond direct experimentation,
49:44scientists will be left wondering
49:46whether their ideas were beautiful enough.
49:49That's Abdus Salam's warning
49:51about Kaluza-Klein and multidimensional theories.
49:54I must confess that one cannot say
49:59that the aesthetics of man
50:01are the same as the aesthetics of the Lord.
50:04They may be very, very different.
50:06I do not, I would not like to say
50:09that this is the final theory,
50:11but I would like it to be correct,
50:13if it's possible, to test it properly.
50:24Since 1983, the experiment
50:27which confirmed the electroweak theory
50:29has begun producing new data
50:31which doesn't fit in with any theory.
50:35News from CERN, announced by Carlo Rubia,
50:38is the observation of some strange new effects,
50:41some surprising anomalies.
50:45The events in question are characterized
50:47by an unpredicted imbalance
50:49in the particles produced,
50:50more off to one side than to the other.
50:53This cannot be reconciled by today's standard model,
50:56and if true, implies that the model may be incomplete.
51:01So far there are about five
51:03very curious new types of phenomena
51:05that have been reported from CERN.
51:08Some of them are called zen events.
51:10They're events where particles come streaming out
51:12in one direction,
51:13nothing comes out of the other side,
51:15the sound of one hand clapping.
51:17It's a strange business,
51:19and these curious anomalies
51:21simply don't fit in the standard theory.
51:24They're not part of it.
51:26They strongly suggest to me
51:28that we may be missing something very important.
51:31Perhaps one possibility
51:33is another kind of force,
51:35a force above and beyond
51:36the weak interactions,
51:38the electromagnetic interactions,
51:40and the strong interactions,
51:41and different also from gravity.
51:43A new force, the fifth force.
51:45Perhaps we are just getting a dim view
51:48of the fifth and perhaps the most important new force
51:51at high energy
51:53from Carlo Rubia and his work at CERN.
51:56If there's a fifth force,
51:57we'll have to put that together with the other forces.
52:00We'll have to make a fourfold unification
52:02before we can make a true unification
52:05of all the forces with graphing.
52:07Things might get a lot more complicated
52:09before they get simpler.
52:13On the other hand,
52:15there is a truly remarkable possibility.
52:18Excitement is mounting
52:19that buried within the debris
52:20that produced the W and Z
52:22may lie the first traces
52:23of one of the extra particles
52:25predicted by supersymmetry.
52:29Could the new data from CERN
52:31be the first evidence of a Fotino
52:33or a Slepton or a Squark?
52:36Or could it be something
52:37that will force physicists
52:38to revise their ideas completely?
52:40Well, I think it's highly improbable
52:42that you get such a good idea.
52:44It could be years before an answer is found.
52:47The solution to this and other puzzles
52:49may only come with the creation
52:51of even higher energy collisions
52:52involving even larger machines.
52:54The world of physics has plans
52:57which will take at least a decade
52:59to develop.
53:02Already under construction
53:03at CERN in Geneva
53:04is a large electron-positron ring
53:07measuring six miles across,
53:09which will be,
53:10when it is completed in 1988,
53:12the biggest machine on Earth.
53:20In the United States,
53:21plans are already underway
53:23for the Superconducting Supercollider,
53:25or SSC.
53:27This accelerator will cost $3 billion,
53:29and, if ever built,
53:31will consist of a circular tunnel
53:32as much as 100 miles long.
53:39Superconducting magnet technology
53:41would drive and steer the particles
53:43on their epic journey,
53:44ending in collisions with energies
53:46as much as 80 times as great
53:48as the events which are producing
53:49today's puzzles.
53:51People often come to me
53:52and they say,
53:53what is this that you're doing for?
53:56Why should the United States government
53:58spend millions and millions of dollars
54:00to build a new machine?
54:01Will it lead to a new kind of toothpaste
54:03or something like that?
54:04And I have to say to them
54:06that mostly the answer is no.
54:09What I usually say is this.
54:10I say that people differ from other animals
54:14in that they have curiosity.
54:16They look at the stars with wonder.
54:19We might try to teach dolphins
54:21and chimpanzees to speak,
54:23and sometimes we're successful,
54:25but they're sure not going to look at the sky
54:27and imagine constellations.
54:29This is the way in which people,
54:31or at least little children,
54:32differ from animals.
54:34Little children are curious.
54:36My kids ask me,
54:37where does the sun go at night,
54:38and how come I can suck a soda
54:41up through a straw?
54:42Questions like this.
54:44Later in life,
54:45they are trained
54:46not to ask questions of this kind.
54:48Not all of them.
54:49Some of them maintain
54:50this primordial human quality
54:52of curiosity.
54:53Some of these people become artists,
54:55like the man who made that.
54:57Some become composers.
54:58Some become physicists.
55:00Some become astronomers.
55:01These people, in a sense,
55:03have kept the faith.
55:04They really want to know
55:05what's going on.
55:14It's hard to imagine a time
55:16when all our questions
55:17will be answered.
55:19When there are no more puzzles to solve.
55:22When most physicists are agreed
55:24on the nature of the universe.
55:27And even if they think they've found out,
55:30how will they know if they are right?
55:33As long as these questions remain,
55:36the search for the ultimate theory
55:38will continue.
57:39To purchase film or video copies of this program for educational use, call toll-free 1-800-621-2131.
57:46In Illinois or Alaska, call Collect 312-940-1260.
Comments