0:00:04 > 0:00:06Archive programmes chosen by experts.
0:00:06 > 0:00:09For this collection, Prof Alice Roberts has selected
0:00:09 > 0:00:13a range of programmes to celebrate Horizon's 50th anniversary.
0:00:13 > 0:00:16More Horizon programmes and other BBC Four Collections
0:00:16 > 0:00:18are available on BBC iPlayer.
0:01:06 > 0:01:08The important thing is first to steep yourself in the problem,
0:01:08 > 0:01:11to look at the puzzle, all the pieces of the puzzle.
0:01:11 > 0:01:14Turn them around, and look at them in different ways and try to put them
0:01:14 > 0:01:15together.
0:01:15 > 0:01:17Find out what's missing, what's the...
0:01:17 > 0:01:19at the root of the apparent paradox.
0:01:19 > 0:01:20And then...
0:01:22 > 0:01:25Then, usually, you find you can't do much more.
0:01:26 > 0:01:30And you put the work aside and do something else,
0:01:30 > 0:01:33and then at an odd moment you may get an idea.
0:01:33 > 0:01:35Apparently, the mind works on these things unconsciously
0:01:35 > 0:01:37once it's been fed.
0:01:38 > 0:01:43At night, you may wake up in the middle of the night and have an idea.
0:01:43 > 0:01:45Usually it turns out that it's nonsense!
0:01:45 > 0:01:46Sometimes it's right.
0:01:46 > 0:01:50And you might have an idea when you're shaving or driving your car.
0:01:50 > 0:01:55The strangeness theory came to me when I was explaining a wrong idea to
0:01:55 > 0:01:58somebody, I was explaining why that idea wouldn't work.
0:01:58 > 0:02:01I made a slip of the tongue, and I had the strangeness theory.
0:02:02 > 0:02:06I find I'm quite prolific with ideas.
0:02:06 > 0:02:09On the other hand, they tend to be wrong most of the time.
0:02:09 > 0:02:12Probably five out of each six ideas - I don't know,
0:02:12 > 0:02:15I don't have the right statistics.
0:02:15 > 0:02:22But I know that they come to me and if I want to explain them to somebody
0:02:22 > 0:02:24and get some criticism,
0:02:24 > 0:02:27and listen to myself explaining them to somebody else.
0:02:28 > 0:02:30I want to find out whether they are right or wrong
0:02:30 > 0:02:32and I have to do it in that way,
0:02:34 > 0:02:36Two years ago, Gell-Mann and Ne'eman
0:02:36 > 0:02:40predicted the existence of a fleeting particle of matter, which,
0:02:40 > 0:02:44if found, would resolve the puzzle of what matter is ultimately made of.
0:02:45 > 0:02:49This programme tells the story behind the dramatic two-year search for
0:02:49 > 0:02:51the particle and of the transformation of our ideas
0:02:51 > 0:02:53now that it's been found.
0:02:54 > 0:02:58The programme is introduced by one of the world's leading theoretical
0:02:58 > 0:03:00physicists, Richard Feynman.
0:03:00 > 0:03:03Progress in physics seems to come in fits and starts.
0:03:03 > 0:03:07The really great pinnacles, the revolutionary discoveries,
0:03:07 > 0:03:11the great transformations of ideas, come very infrequently.
0:03:11 > 0:03:14Perhaps in the last 200 years there's only been half a dozen such things.
0:03:14 > 0:03:17You might think of Newton's discovery of the laws of mechanics
0:03:17 > 0:03:18and gravitation,
0:03:18 > 0:03:22Maxwell's theory of electricity and magnetism,
0:03:22 > 0:03:25Einstein's theory or relativity, and, in the 20th century,
0:03:25 > 0:03:27the theory of quantum mechanics.
0:03:28 > 0:03:30I think we're due for a new one.
0:03:30 > 0:03:33I think very soon we'll have another great transformation of ideas,
0:03:33 > 0:03:37during which we discover the ultimate understanding of the forces
0:03:37 > 0:03:39between nuclear particles.
0:03:39 > 0:03:43Now, with every...great pinnacle of discovery, there is
0:03:43 > 0:03:46a long preliminary process of gathering information,
0:03:46 > 0:03:48sorting it down a little bit
0:03:48 > 0:03:51and getting it prepared to be understood.
0:03:51 > 0:03:53For example, for the law of gravitation there was first
0:03:53 > 0:03:56the observations of the motions of the planets,
0:03:56 > 0:03:58then a certain amount of partial understanding,
0:03:58 > 0:04:02such as Copernicus's idea that the planets went around the sun,
0:04:02 > 0:04:05and later Kepler's discovery that they went in ellipses.
0:04:05 > 0:04:09But the final ultimate law of gravitation required
0:04:09 > 0:04:11all this preliminary jockeying of the data around
0:04:11 > 0:04:13to understand it partially.
0:04:14 > 0:04:19In the same way, the future discovery of the laws of nuclear physics,
0:04:19 > 0:04:21nuclear interaction,
0:04:21 > 0:04:24is preceded by a partial summation of the information
0:04:24 > 0:04:28that's available so far, and just recently we've had one of the most
0:04:28 > 0:04:32important and dramatic reshufflings of our understanding.
0:04:32 > 0:04:34So, that I think we're almost ready
0:04:34 > 0:04:36to get the answer to the big question.
0:04:36 > 0:04:40What I want to tell you about today is the...
0:04:40 > 0:04:43this partial understanding that we've just achieved.
0:04:43 > 0:04:46Some time ago, things looked pretty simple.
0:04:46 > 0:04:52We just had a theory that the atoms had, on the outside, electrons,
0:04:52 > 0:04:56and, on the inside, nuclei, and that the nuclei were made of nothing
0:04:56 > 0:04:59but two particles in the world, the neutrons and the protons.
0:04:59 > 0:05:03And then, with such a simple picture, just two nuclear particles,
0:05:03 > 0:05:06the nuclear problem just to understand the simple law of force
0:05:06 > 0:05:08between neutron and proton.
0:05:08 > 0:05:11Probably some simple law like the electrical law that the force varies
0:05:11 > 0:05:13inversely as the square of the distance,
0:05:13 > 0:05:15or some other beautifully simple thing
0:05:15 > 0:05:16was all that had to be found out.
0:05:16 > 0:05:20So, a programme was launched to study the interactions of neutrons
0:05:20 > 0:05:23and protons and it was discovered, as time went on, that it
0:05:23 > 0:05:25all looked a little more complicated.
0:05:25 > 0:05:27Ultimately, that it was extremely complicated,
0:05:27 > 0:05:29that it was a s complicated as it could be,
0:05:29 > 0:05:30that the force between neutrons
0:05:30 > 0:05:32and protons depended on practically everything
0:05:32 > 0:05:36and that it depended on how far apart they were, in a very complicated way.
0:05:36 > 0:05:39It depends on which direction they're spinning, what direction
0:05:39 > 0:05:42they approach each other relative to the way they're spinning, and so on.
0:05:42 > 0:05:45In fact, it depends on everything that it can depend on and is as
0:05:45 > 0:05:46complicated as it can be,
0:05:46 > 0:05:49except for one little thing, which I'll mention later.
0:05:50 > 0:05:52Now, when a thing looks complicated
0:05:52 > 0:05:54it's possible that we're looking at it wrong
0:05:54 > 0:05:57and that we're missing some of the pieces of the puzzle.
0:05:57 > 0:05:58And, as a matter of fact, there was
0:05:58 > 0:06:01direct evidence that pieces were missing
0:06:01 > 0:06:03in the fact that in cosmic rays,
0:06:03 > 0:06:07the fast particles which come from the outside somewhere,
0:06:07 > 0:06:08in a study in cosmic rays,
0:06:08 > 0:06:12it was found that there were some new particles,
0:06:12 > 0:06:14other particles beside the neutron and proton.
0:06:14 > 0:06:15First there were some mesons,
0:06:15 > 0:06:17which were partially expected, and then there
0:06:17 > 0:06:20were another group of heavier objects,
0:06:20 > 0:06:22one of which was called the lambda meson.
0:06:22 > 0:06:25And it was found to disintegrate into a proton
0:06:25 > 0:06:26and one of the mesons sometimes.
0:06:26 > 0:06:31Sometimes it disintegrates into a neutron and one of the mesons.
0:06:31 > 0:06:35The cosmic rays also discovered still another particle called
0:06:35 > 0:06:37a cascade particle which itself disintegrates into a lambda.
0:06:39 > 0:06:43Now, progress with cosmic rays was very slow
0:06:43 > 0:06:47and was very much speeded up by the development of modern accelerators
0:06:47 > 0:06:49which produce particles as fast and as energetic
0:06:49 > 0:06:50as those in a cosmic ray,
0:06:50 > 0:06:53so that we, so to speak, brought the thing under our own control
0:06:53 > 0:06:54rather than having to wait
0:06:54 > 0:06:58for the odd fast particle and reaction to occur in nature.
0:06:58 > 0:07:00In addition, we've developed better instruments
0:07:00 > 0:07:02for observing the particles,
0:07:02 > 0:07:04instead of cloud chambers, bubble chambers.
0:07:04 > 0:07:06And with these bubble chambers and modern accelerators,
0:07:06 > 0:07:10the progress in finding new particles has rapidly increased.
0:07:10 > 0:07:13Five years ago, we were up to 30 particles.
0:07:13 > 0:07:16Now, we have 90 particles.
0:07:16 > 0:07:19So, the problem has got a little more complicated.
0:07:19 > 0:07:21We used to just worry about how the things acted.
0:07:21 > 0:07:24Now, we have to divide the problem into two parts,
0:07:24 > 0:07:25we have to go back a step.
0:07:25 > 0:07:28First, we have to decide what there is in the world,
0:07:28 > 0:07:30and then, how does this stuff act.
0:07:30 > 0:07:33We have to now figure out what the pattern is of available particles,
0:07:33 > 0:07:35in other words, what kind of a world,
0:07:35 > 0:07:38what the particles are that are in the world.
0:07:39 > 0:07:42First thing turns out that they come in families.
0:07:42 > 0:07:45For example, the neutron and proton are very similar.
0:07:45 > 0:07:48They are the same mass and they have other characteristics in common.
0:07:48 > 0:07:51But the most remarkable characteristic is this.
0:07:51 > 0:07:53That although the forces between neutrons and protons
0:07:53 > 0:07:56and protons and protons are very complicated,
0:07:56 > 0:07:59the force between a neutron and proton
0:07:59 > 0:08:01and between a proton and proton are the same.
0:08:01 > 0:08:04That's a very mysterious accident.
0:08:04 > 0:08:06It's only true of the nuclear part of the force, the electrical forces,
0:08:06 > 0:08:08of course, are different.
0:08:08 > 0:08:09One is charged and one is neutral.
0:08:09 > 0:08:11But the nuclear part of the forces, we've discovered,
0:08:11 > 0:08:13has one peculiar characteristic.
0:08:13 > 0:08:15That is, that you can change a neutron for a proton
0:08:15 > 0:08:18and it doesn't make any difference to the force.
0:08:18 > 0:08:22We say that the nuclear forces have a symmetry, they have a symmetry
0:08:22 > 0:08:26that you can change neutron to proton without making any difference.
0:08:26 > 0:08:28The fact that we use the word "symmetry" here
0:08:28 > 0:08:30is a kind of technical use of that word.
0:08:30 > 0:08:34What is a symmetrical thing, how would you define a symmetrical thing?
0:08:36 > 0:08:40One definition is that a symmetrical thing is something that you can do
0:08:40 > 0:08:42something to and it doesn't make any difference.
0:08:42 > 0:08:46This book, for example, I could turn it over and it looks the same.
0:08:46 > 0:08:49Something I can change something, do something to it,
0:08:49 > 0:08:50and it still looks the same.
0:08:50 > 0:08:52And we use the same word in the physics sense
0:08:52 > 0:08:54to represent the fact that
0:08:54 > 0:08:58I can change the neutron to a proton and the nuclear forces look the same.
0:08:58 > 0:09:00So, neutron and proton together form a family
0:09:00 > 0:09:02as far as nuclear forces are concerned.
0:09:02 > 0:09:04And it turns out that the cascade particle
0:09:04 > 0:09:07is a member of a family of two - one negative and one neutral.
0:09:07 > 0:09:10The lambda stands by itself, but there is another particle,
0:09:10 > 0:09:13a set of three particles that are similar, that also get exchanged.
0:09:13 > 0:09:18And produce a family of the kind that the neutron and proton produce.
0:09:18 > 0:09:21Besides families, we found out that there are hierarchies
0:09:21 > 0:09:23between these particles.
0:09:23 > 0:09:27For example, a lambda disintegrates into a neutron and a meson,
0:09:27 > 0:09:30or sometimes into a proton and a meson, and that it does very slowly,
0:09:30 > 0:09:33it takes a third of a billionth of a second.
0:09:33 > 0:09:36It sounds like that's pretty fast, but for nuclear reaction,
0:09:36 > 0:09:38nuclear particles, that's very slow.
0:09:38 > 0:09:40It should happen almost a billion times more rapidly
0:09:40 > 0:09:42if there weren't something in the way.
0:09:42 > 0:09:46In order to analyse this "something in the way" in these disintegrations,
0:09:46 > 0:09:49Prof Gell-Mann, here at Caltech,
0:09:49 > 0:09:54invented a method of description which describes this situation.
0:09:54 > 0:09:57He said that, in a sense, the lambda has a kind of character, that it
0:09:57 > 0:10:00has difficulty into disintegrating into a neutron and proton
0:10:00 > 0:10:01and he makes the rule
0:10:01 > 0:10:04that if you want to disintegrate with change of character,
0:10:04 > 0:10:04it should be slow.
0:10:04 > 0:10:07And thus, is able to associate character,
0:10:07 > 0:10:09a kind of character to the different particles,
0:10:09 > 0:10:11in which he gives a numerical number.
0:10:11 > 0:10:16He calls this number strangeness, he says this is strangeness number zero,
0:10:16 > 0:10:18this is strangeness one.
0:10:18 > 0:10:20You'd think actually he'd call it with a minus sign,
0:10:20 > 0:10:22but that's just an accident of history.
0:10:22 > 0:10:27But then it turns out that the cascade particle here can't directly
0:10:27 > 0:10:28disintegrate into neutron and proton,
0:10:28 > 0:10:30it disintegrates slowly into a lambda,
0:10:30 > 0:10:32and then the lambda into neutron and proton.
0:10:32 > 0:10:35So, the cascade particle has a character number minus two,
0:10:35 > 0:10:38being two steps removed in the slow disintegrations
0:10:38 > 0:10:39to the neutron and proton.
0:10:39 > 0:10:43That is some partial analysis of the particles that are in the world.
0:10:43 > 0:10:46There's these families, for interchange,
0:10:46 > 0:10:49and there are these hierarchies associated with the strangeness.
0:10:49 > 0:10:52Question is, is there any more symmetry in this system?
0:10:52 > 0:10:54For instance.
0:10:54 > 0:10:57Is it possible that an exchange of a neutron with a lambda
0:10:57 > 0:11:00might make no difference in nuclear forces?
0:11:00 > 0:11:02Or some other possible combinations.
0:11:02 > 0:11:06That if you change a P, a proton, to a sigma, a C, a cascade, to a sigma
0:11:06 > 0:11:10or something like that, into certain particular combinations,
0:11:10 > 0:11:11it makes no difference.
0:11:11 > 0:11:14People have tried very many attempts to find such additional symmetries.
0:11:14 > 0:11:16In order to help them, they've used the mathematics
0:11:16 > 0:11:18of what's called "group theory".
0:11:18 > 0:11:21Group theory is something that mathematicians have analysed a lot
0:11:21 > 0:11:23the problem of what happens if you exchange
0:11:23 > 0:11:25one thing with another and then something with something else.
0:11:25 > 0:11:27What is the net result of all that?
0:11:27 > 0:11:30So, that the mathematicians have prepared for the physicists
0:11:30 > 0:11:33the necessary mathematics, called "group theory", to analyse this.
0:11:33 > 0:11:38At any rate, many types of... possible systems of exchanges
0:11:38 > 0:11:42have been suggested to understand the way the world works
0:11:42 > 0:11:46and in each case, sometimes, you would predict something
0:11:46 > 0:11:48that wasn't exactly in accord with experiment
0:11:48 > 0:11:50and it didn't look very hopeful.
0:11:50 > 0:11:52As a matter of fact, I myself, after playing around with Gell-Mann,
0:11:52 > 0:11:55trying it together, we tried many combinations,
0:11:55 > 0:11:57we came to the conclusion that there probably wasn't
0:11:57 > 0:11:59any other symmetry in the system.
0:11:59 > 0:12:01The problem is very hard.
0:12:01 > 0:12:02Why should it be hard?
0:12:02 > 0:12:04If a thing is symmetrical, ordinarily,
0:12:04 > 0:12:06with one glance of the eye
0:12:06 > 0:12:08you could see immediately that it's symmetrical,
0:12:08 > 0:12:10so why is it that it's not possible to look right away
0:12:10 > 0:12:12at the character of the particles
0:12:12 > 0:12:13that are discovered and see the symmetry?
0:12:13 > 0:12:15There are two reasons.
0:12:15 > 0:12:17First, the symmetry is not perfect.
0:12:17 > 0:12:20In the case of the pattern that you can replace neutron by proton,
0:12:20 > 0:12:24that is very accurate, but it's not exactly perfect in nature
0:12:24 > 0:12:26because the two protons interact electrically
0:12:26 > 0:12:27while the neutrons don't,
0:12:27 > 0:12:29but if we leave out the electricity, it's quite perfect.
0:12:29 > 0:12:31The electricity is only one or so percent
0:12:31 > 0:12:33However, we know already,
0:12:33 > 0:12:35because the masses of these particles are so different,
0:12:35 > 0:12:37that any other symmetry that must be there
0:12:37 > 0:12:39must be quite a bit off, by 10 or 20%.
0:12:39 > 0:12:42To look for a somewhat symmetrical thing takes more skill
0:12:42 > 0:12:44than to notice a symmetrical thing.
0:12:44 > 0:12:47The other part of the problem is that we have missing parts.
0:12:47 > 0:12:51If you had a vase which you knew was nearly symmetrical
0:12:51 > 0:12:53and half of it was broken off, or nearly half of it was broken off,
0:12:53 > 0:12:56it would be a little bit hard to tell the character,
0:12:56 > 0:12:57the pattern of symmetry,
0:12:57 > 0:13:00so that, when there is only a limited number of particles,
0:13:00 > 0:13:01it gets somewhat difficult.
0:13:01 > 0:13:05For example, there was known a set of four particles
0:13:05 > 0:13:06in addition to this set,
0:13:06 > 0:13:10which belong together in the kind of family that these belong.
0:13:11 > 0:13:15Then it became clear that there was another set of three more
0:13:15 > 0:13:19that were similar for such exchanges
0:13:19 > 0:13:21and there was part of a suggestion,
0:13:21 > 0:13:24there was a suggestion made by Gell-Mann
0:13:24 > 0:13:26and independently by Prof Ne'eman
0:13:26 > 0:13:28of a certain particular pattern of interchanges
0:13:28 > 0:13:29among all these particles
0:13:29 > 0:13:34which would permit an understanding of what was known so far,
0:13:34 > 0:13:37but would only permit these four
0:13:37 > 0:13:41provided these three and another pair and...
0:13:41 > 0:13:46and still a third particle, all by itself, existed in the world.
0:13:46 > 0:13:49They, when they made this up, only knew about this
0:13:49 > 0:13:50and a little bit about that
0:13:50 > 0:13:53and were rather reluctant to suggest that it was true
0:13:53 > 0:13:55because there were so many missing pieces it was unbelievable.
0:13:55 > 0:13:58However, when these particles turned out to exist
0:13:58 > 0:14:01and to fit their triangle of interconnections,
0:14:01 > 0:14:05which they expected would occur, they became more...
0:14:05 > 0:14:09ambitious and suggested that, in fact, the theory is right.
0:14:09 > 0:14:12In order to make this theory right, however,
0:14:12 > 0:14:14this particle here was missing.
0:14:14 > 0:14:17Now, many of the other symmetry systems predicted new particles
0:14:17 > 0:14:20and many new particles were found, but, in the confusion,
0:14:20 > 0:14:23the particles had no particular special properties
0:14:23 > 0:14:25and one could make an accident
0:14:25 > 0:14:26that nature did have a particle
0:14:26 > 0:14:28something like what you are looking for.
0:14:28 > 0:14:30But this new particle that was predicted
0:14:30 > 0:14:32by the Gell-Mann-Ne'eman theory
0:14:32 > 0:14:37was very peculiar and unique in its characteristics.
0:14:37 > 0:14:43It had strangeness -3 and this theory predicted that there should exist
0:14:43 > 0:14:46a negatively charged particle with strangeness -3,
0:14:46 > 0:14:49which means that it would only be able to disintegrate
0:14:49 > 0:14:53in three steps before it got to neutron and proton.
0:14:53 > 0:14:55This was so unique and definite a prediction
0:14:55 > 0:14:59that the theory would be made and broken very easily by experiment.
0:15:00 > 0:15:02So, the very interesting question was,
0:15:02 > 0:15:04do they have the right pattern? Is there an extension,
0:15:04 > 0:15:07a new kind of additional symmetry among the particles,
0:15:07 > 0:15:09an additional fact to simplify our understanding,
0:15:09 > 0:15:12by which the families of two, three and so on
0:15:12 > 0:15:15can be combined in one element, two elements,
0:15:15 > 0:15:17and thus take on 90 particles
0:15:17 > 0:15:19and replace them by two, three or four groups?
0:15:19 > 0:15:22If so, of course, we're making enormous progress.
0:15:22 > 0:15:26The big question was, experimentally, does this omega minus exist or not?
0:15:26 > 0:15:30This was a moment that is characteristic of physics
0:15:30 > 0:15:33that's one of the big thrills and mysteries.
0:15:33 > 0:15:36How is it possible, by looking at a piece of nature,
0:15:36 > 0:15:40to guess how another part must look, where you have never been before?
0:15:40 > 0:15:41How is it...?
0:15:41 > 0:15:46It's only in modern times that man has really been able to guess
0:15:46 > 0:15:48what nature is going to do in situations
0:15:48 > 0:15:49that he's never looked at before
0:15:49 > 0:15:51and here is an example of it.
0:15:52 > 0:15:53With many strange particles,
0:15:53 > 0:15:55by looking at those which you have seen already,
0:15:55 > 0:15:56it is possible to guess
0:15:56 > 0:15:59that there must be something that you haven't looked at yet.
0:15:59 > 0:16:02The reason this is possible is partly man's ingenuity,
0:16:02 > 0:16:06but, obviously, more important is nature's inner simplicity.
0:16:06 > 0:16:09To look for this particle is a typical,
0:16:09 > 0:16:12dramatic scientific investigation,
0:16:12 > 0:16:18so the two ingenious men, Gell-Mann and Ne'eman, waited for two years
0:16:18 > 0:16:21to see whether nature recognised their ingenuity.
0:16:21 > 0:16:22And she did.
0:16:22 > 0:16:24The particle was found.
0:16:27 > 0:16:30Dr Gell-Mann, how confident did you feel during the two years
0:16:30 > 0:16:33you were waiting for your predictions to be checked?
0:16:33 > 0:16:37Oh, my confidence had its ups and downs.
0:16:37 > 0:16:40There were lots of other things going on besides omega minus.
0:16:42 > 0:16:46The search for the omega minus took two years at Brookhaven,
0:16:46 > 0:16:52but the theory of the higher symmetry made a number of other predictions
0:16:52 > 0:16:55besides the existence of omega minus
0:16:55 > 0:16:57and some of those were being confirmed.
0:16:57 > 0:17:01A couple of others looked a bit cloudy for part of the time and...
0:17:03 > 0:17:06So, I wasn't always sure that it would work out all right.
0:17:08 > 0:17:09How much is do you fight for your theories
0:17:09 > 0:17:12if it looks as if they have been proved wrong?
0:17:12 > 0:17:16Oh, well, it depends a lot, I think, on whether...
0:17:18 > 0:17:25..a really reliable experiment has definitely contradicted something.
0:17:25 > 0:17:28If that happens then you just drop the theory, it's no good,
0:17:28 > 0:17:30and you try a different tack.
0:17:30 > 0:17:34But if it's a very complicated experimental situation,
0:17:34 > 0:17:36the theory looks particularly beautiful,
0:17:36 > 0:17:37you might hope that there is
0:17:37 > 0:17:39something the matter with the experiment.
0:17:39 > 0:17:40They are awfully difficult in this field.
0:17:40 > 0:17:43They take a long time and they are very expensive
0:17:43 > 0:17:46and they're very hard to do and to...and to recheck,
0:17:46 > 0:17:48so that it quite often happens
0:17:48 > 0:17:52that an experimental result that is reported is really not right.
0:17:52 > 0:17:56Are you afraid to put a theory forward because it might be wrong?
0:17:56 > 0:18:00Yes, I am terrified of putting forward a theory
0:18:00 > 0:18:01- that I'm afraid would be wrong. - Why?
0:18:04 > 0:18:05Your reputation?
0:18:05 > 0:18:07No, it's just a personal quirk.
0:18:10 > 0:18:13Probably, I would be a lot happier if I didn't have to...
0:18:13 > 0:18:15to worry about that.
0:18:15 > 0:18:19There are lots of scientists who speculate quite freely
0:18:19 > 0:18:22and don't worry very much about whether their predictions
0:18:22 > 0:18:26are related to reality or not, but it bothers me terribly.
0:18:26 > 0:18:28In other things, too?
0:18:28 > 0:18:31Yes, it carries over into all kinds of things.
0:18:31 > 0:18:34It must be deeply rooted somewhere in my character.
0:18:34 > 0:18:39I remember in Paris, when I lived there in '59, '60,
0:18:39 > 0:18:41I would go to a party
0:18:41 > 0:18:44and then would come back and spend a sleepless night
0:18:44 > 0:18:46on account of some mistake in grammar that I knew I'd made.
0:18:46 > 0:18:50Do you set aside so many hours a day for thinking?
0:18:50 > 0:18:51Well, you could do that.
0:18:51 > 0:18:55It's not necessarily the time when you get ideas, though.
0:18:55 > 0:18:58I'd set aside a certain time, maybe, for...
0:18:58 > 0:19:00studying a problem if I were better organised.
0:19:00 > 0:19:04Actually, I don't really plan my life very much.
0:19:04 > 0:19:06What do you do with most of your time?
0:19:06 > 0:19:09Oh, I sort of drift from one thing to another.
0:19:09 > 0:19:11I do an awful lot of reading.
0:19:11 > 0:19:16Everything I'm interested in somehow smacks of natural history, I guess.
0:19:16 > 0:19:18Customs of primitive people,
0:19:18 > 0:19:21languages and the relations among them.
0:19:23 > 0:19:26You are always looking for patterns in nature?
0:19:26 > 0:19:27Yes.
0:19:28 > 0:19:31- Now, what's...? - Patterns in the way people think.
0:19:31 > 0:19:33Patterns in the elementary particles.
0:19:33 > 0:19:37It's all part of the same way of doing things, I suppose.
0:19:37 > 0:19:40Trying to spot the law, trying to spot the relationship.
0:19:40 > 0:19:43What's so special about the patterns in physics?
0:19:45 > 0:19:48Oh, the laws of the elementary particles are...
0:19:48 > 0:19:50are very special.
0:19:50 > 0:19:52The whole universe is made up of these little particles.
0:19:52 > 0:19:56The light from the most distant galaxy shows that there, too,
0:19:56 > 0:19:58the same laws hold.
0:20:00 > 0:20:03They, too, are made up of the same little particles that we are...
0:20:04 > 0:20:06..we are made up of.
0:20:06 > 0:20:11And their laws, the laws of the weak and the strong interactions,
0:20:11 > 0:20:14along with the laws of electromagnetism and gravity,
0:20:14 > 0:20:16determine how the...
0:20:16 > 0:20:19how all the bits of the universe work.
0:20:19 > 0:20:22They determine the behaviour of matter
0:20:22 > 0:20:25and it's fascinating to try to figure out what these laws are.
0:20:25 > 0:20:29Of course, you never get a final answer.
0:20:29 > 0:20:32We just keep going from one approximation to another,
0:20:32 > 0:20:35getting to understand things better and better.
0:20:35 > 0:20:37How many more useful years do you think
0:20:37 > 0:20:38you have as a theoretical physicist?
0:20:38 > 0:20:40Oh, I don't know.
0:20:40 > 0:20:42I figured some years ago that I'd probably be through at 30,
0:20:42 > 0:20:44so that we give me -4 years,
0:20:44 > 0:20:47but I guess I still have a few anyway.
0:20:49 > 0:20:51At the end of...
0:20:51 > 0:20:55a certain time, most theoretical physicists seem to, er,
0:20:55 > 0:20:59lose their flexibility and I suppose that will happen to me, too.
0:20:59 > 0:21:00Maybe it has already happened.
0:21:00 > 0:21:03What happens when you and, say, Feynman get together?
0:21:03 > 0:21:05Do you get into heated arguments?
0:21:05 > 0:21:07Oh, we have wonderful arguments!
0:21:08 > 0:21:09Back and forth.
0:21:09 > 0:21:12"No, you can't do that! It won't work!
0:21:12 > 0:21:15"You'll get the magnetic moment of the sigma wrong!" or...
0:21:15 > 0:21:18"The decay mode won't be the right one!"
0:21:18 > 0:21:21or... "The branching ratio will come out wrong!"
0:21:21 > 0:21:23"Yes, it will be perfectly all right."
0:21:23 > 0:21:25"You don't understand what I'm doing. I'm really doing it this way."
0:21:25 > 0:21:30We don't get mad at each other at all, but we scream and yell and...
0:21:32 > 0:21:34What about your relationship with Ne'eman?
0:21:34 > 0:21:38Oh, I've had some very fine conversations with him, too,
0:21:38 > 0:21:39this year.
0:21:39 > 0:21:43You know, we started completely independently and...
0:21:43 > 0:21:48In 1961, when I was thinking of the eightfold way, January 1961,
0:21:48 > 0:21:52and wrote it up and sent off for preprint...
0:21:54 > 0:21:57..it crossed his preprint in the mail.
0:21:57 > 0:22:01He was working at Imperial College London and...
0:22:01 > 0:22:04when I sent off my paper, I got his
0:22:04 > 0:22:06on the same subject with about the same ideas -
0:22:06 > 0:22:09the eightfold-way pattern, he called it something else.
0:22:11 > 0:22:16And then I was told that he was a colonel in the Israeli army
0:22:16 > 0:22:18and I imagined he must be rather a fascinating person
0:22:18 > 0:22:20and it turned out to be very true.
0:22:20 > 0:22:24And, luckily, he's been able to spend the last year here at Caltech.
0:22:26 > 0:22:30Dr Ne'eman, as a colonel in the Israeli army,
0:22:30 > 0:22:33how did you come to be interested in particle physics?
0:22:33 > 0:22:36Oh, well, this is mainly because of London traffic, really.
0:22:36 > 0:22:39- Really? - It's... Yes.
0:22:39 > 0:22:41I came to London to do physics
0:22:41 > 0:22:43and the reason I had accepted this idea
0:22:43 > 0:22:45of becoming a military attache in England
0:22:45 > 0:22:49was that it was given to me as an opportunity
0:22:49 > 0:22:53to combine it with studies which I had asked for at the time.
0:22:53 > 0:22:56And I was interested in general relativity.
0:22:56 > 0:22:58I knew that Bondi was in London
0:22:58 > 0:23:01and there was a good group working in general relativity,
0:23:01 > 0:23:03so I came to England to do that.
0:23:03 > 0:23:10Now, our embassy is in Kensington and when I looked and saw London,
0:23:10 > 0:23:12I realised that there was really no hope
0:23:12 > 0:23:15to combine a job of a military attache in Kensington
0:23:15 > 0:23:16with studies at King's,
0:23:16 > 0:23:18which was on the other side of Trafalgar Square,
0:23:18 > 0:23:20so I looked for something nearer
0:23:20 > 0:23:22and I found the Imperial College
0:23:22 > 0:23:26at five minutes' walking distance from the embassy,
0:23:26 > 0:23:31so I went to Imperial College and I found Salam.
0:23:31 > 0:23:34I think I was really lucky, in fact.
0:23:34 > 0:23:35Probably...
0:23:35 > 0:23:39an extremely lucky thing that happened to me because...
0:23:39 > 0:23:40if...
0:23:40 > 0:23:42Well, I might have been in...
0:23:42 > 0:23:44done interesting things in general relativity,
0:23:44 > 0:23:48but I think elementary particle physics is...
0:23:48 > 0:23:53more of a frontier now and I was very lucky to...
0:23:53 > 0:23:56really to get to work with Salam
0:23:56 > 0:24:02because he is certainly one of the best men in that field
0:24:02 > 0:24:07and the whole choice of my subject was influenced
0:24:07 > 0:24:12by the fact that he was a man who believed in this type of solution,
0:24:12 > 0:24:15he believed in symmetries in general
0:24:15 > 0:24:21as a possible answer to problems in elementary particle physics
0:24:21 > 0:24:25and I got very interested in that.
0:24:25 > 0:24:27How old were you when you joined Salam?
0:24:27 > 0:24:29Oh, I...
0:24:29 > 0:24:31Well, about 33...
0:24:31 > 0:24:3332, 33, I think.
0:24:33 > 0:24:37Isn't that about the age when most theoretical physicists are giving up?
0:24:37 > 0:24:40Well, I had asked myself that question.
0:24:42 > 0:24:45I thought, in fact, that this was
0:24:45 > 0:24:48probably the last chance I had to go into physics,
0:24:48 > 0:24:52but I was afraid that I might have missed the bus, as you say.
0:24:52 > 0:24:54And, er...
0:24:54 > 0:24:56It was like a challenge and...
0:24:56 > 0:25:01On the other hand, after I saw that it was working out well,
0:25:01 > 0:25:03I got thinking about this question,
0:25:03 > 0:25:05whether there is really a limiting age,
0:25:05 > 0:25:09whether one has to be really young.
0:25:09 > 0:25:14My theory about it is that you have to be young in the profession,
0:25:14 > 0:25:16young in a material sense.
0:25:16 > 0:25:18I think that within ten years
0:25:18 > 0:25:23you do anything interesting you can do in a certain field.
0:25:23 > 0:25:24You've asked all the questions
0:25:24 > 0:25:26and you've either found answers or not.
0:25:26 > 0:25:31And then you are just really treading on the same ground all the time.
0:25:31 > 0:25:35How did you feel during the two-year wait for the Brookhaven results?
0:25:35 > 0:25:37Two years...
0:25:37 > 0:25:38Well, nothing really.
0:25:38 > 0:25:41It was last week that was extremely bad.
0:25:41 > 0:25:42We...
0:25:42 > 0:25:47I was attending a conference at Miami and Maurice Goldhaber,
0:25:47 > 0:25:51the director of Brookhaven, was there and, sitting near the swimming pool,
0:25:51 > 0:25:55he was telling me that they had gone through 60,000 feet of film
0:25:55 > 0:25:58and were not finding anything.
0:25:58 > 0:26:02I was a bit shocked and I came back here
0:26:02 > 0:26:07and Gell-Mann was getting ready to go to Japan,
0:26:07 > 0:26:10so I told him about these results
0:26:10 > 0:26:17and his reply was, "Would Mount Fuji be the right place to jump off from?"
0:26:17 > 0:26:21And I said, "I can always go back to the Israeli army."
0:26:22 > 0:26:26And then the news came a week later, you know.
0:26:28 > 0:26:31For many of us here at Brookhaven on Long Island in New York,
0:26:31 > 0:26:35the hunt for the omega minus has been one of the most exciting searches
0:26:35 > 0:26:37undertaken in the last ten years.
0:26:37 > 0:26:40I first became interested in the omega minus
0:26:40 > 0:26:43while attending an international conference
0:26:43 > 0:26:46on high-energy physics in Geneva in 1962,
0:26:46 > 0:26:48precisely two years ago.
0:26:49 > 0:26:51This was a most stimulating conference
0:26:51 > 0:26:54in that the discovery of many new particles was presented.
0:26:55 > 0:27:00I myself gave a paper reporting the results from here at Brookhaven
0:27:00 > 0:27:03in which we reported the discovery of a new particle, the cascade star.
0:27:07 > 0:27:09You may recognise this pattern
0:27:09 > 0:27:12as something similar to which Feynman drew.
0:27:12 > 0:27:14This is the cascade star.
0:27:16 > 0:27:20Murray Gell-Mann was also in attendance at this conference
0:27:20 > 0:27:23and he immediately grasped the significance of the discovery
0:27:23 > 0:27:27of the cascade star, namely it had strangeness -2
0:27:27 > 0:27:31and it had a mass which fits very conveniently into the scheme.
0:27:32 > 0:27:36The mass difference between this and this is 147.
0:27:36 > 0:27:39The mass difference between this and this is 145,
0:27:39 > 0:27:42these being very close to the same number.
0:27:42 > 0:27:48These particles also fit into a geometric pattern, a very simple one,
0:27:48 > 0:27:49namely a triangle.
0:27:51 > 0:27:52Unfortunately, there is only...
0:27:52 > 0:27:54There is a missing member.
0:27:54 > 0:27:56Gell-Mann called this the omega minus.
0:27:57 > 0:28:01Since it occurs at the apex of the triangle,
0:28:01 > 0:28:05he was also able to determine its strangeness, -3...
0:28:07 > 0:28:11..and a mass where the mass difference between this
0:28:11 > 0:28:13and this had to be 145,
0:28:13 > 0:28:17giving 1,675.
0:28:20 > 0:28:23I was struck by the beauty and the simplicity of the scheme.
0:28:24 > 0:28:29In fact, this idea was an experimentalist's dream,
0:28:29 > 0:28:32in that if they omega minus were found,
0:28:32 > 0:28:36it would prove that the theory was correct, that the scheme was correct.
0:28:36 > 0:28:41If the omega minus were not found, if it did not exist,
0:28:41 > 0:28:44then it would have the effect of disproving the theory.
0:28:44 > 0:28:46It had a definitive answer,
0:28:46 > 0:28:50there was a definitive result, it had a positive effect.
0:28:50 > 0:28:51But as an experimentalist,
0:28:51 > 0:28:55I knew that this would take a great deal of effort,
0:28:55 > 0:29:00numerous people to work on it, a great deal of money and, above all,
0:29:00 > 0:29:02of the order of a few years to perform.
0:29:02 > 0:29:05Therefore, before embarking upon such an experiment,
0:29:05 > 0:29:07one thinks about it very carefully.
0:29:08 > 0:29:12One aspect that was very comforting was the fact that Mr Gell-Mann
0:29:12 > 0:29:14has been extremely successful in his field.
0:29:14 > 0:29:16His batting average has been very high,
0:29:16 > 0:29:19so that one felt there was probably
0:29:19 > 0:29:21quite a bit of truth in it to begin with.
0:29:22 > 0:29:25Upon returning to Brookhaven, we discussed it with...
0:29:25 > 0:29:28I discussed it with my colleagues
0:29:28 > 0:29:30and we decided that it would probably be worthwhile
0:29:30 > 0:29:32to perform this experiment.
0:29:32 > 0:29:35The question now was to obtain
0:29:35 > 0:29:39the necessary tools to go about performing this task.
0:29:39 > 0:29:44Here at Brookhaven, we have the world's largest proton accelerator.
0:29:44 > 0:29:46It is half a mile in diameter
0:29:46 > 0:29:49and is enclosed in an underground concrete tunnel
0:29:49 > 0:29:54in which there are 240 magnets that guide the protons in a circular path
0:29:54 > 0:29:58while they are accelerated until they virtually reach the speed of light.
0:29:58 > 0:29:59Then they smash into a metal target
0:29:59 > 0:30:03from which there are emitted all sorts of particles.
0:30:03 > 0:30:05You can realise the precision needed
0:30:05 > 0:30:09when I tell you that the K-beam had to pass this small slit,
0:30:09 > 0:30:1281 thousandths of an inch in height.
0:30:12 > 0:30:13The Ks that emerge from this slit
0:30:13 > 0:30:16then enter the 80-inch hydrogen bubble chamber.
0:30:16 > 0:30:18Then they are photographed as they react
0:30:18 > 0:30:20with the protons in the hydrogen atoms.
0:30:22 > 0:30:26MACHINE CLANKS STEADILY
0:30:41 > 0:30:451,000 photographs are taken every hour
0:30:45 > 0:30:49and these can be scanned for various particle patterns.
0:30:49 > 0:30:52Since Gell-Mann had given us
0:30:52 > 0:30:58the strangeness, -3, and the mass, 1,675, of the omega minus,
0:30:58 > 0:31:02we were now in a position to predict the decay patterns
0:31:02 > 0:31:06of the omega minus, the patterns the omega minus track
0:31:06 > 0:31:09would leave in decaying in the hydrogen bubble chamber.
0:31:11 > 0:31:12Here is such a pattern.
0:31:14 > 0:31:18The incoming particle, the K minus, comes in
0:31:18 > 0:31:21and interacts with the proton in the hydrogen atom.
0:31:21 > 0:31:23It makes many prongs,
0:31:23 > 0:31:28among which is the omega minus with strangeness -3.
0:31:29 > 0:31:34The omega minus then decays into a particle
0:31:34 > 0:31:36with strangeness 0
0:31:36 > 0:31:39and a neutral particle with strangeness -2.
0:31:40 > 0:31:43A neutral particle, a particle with zero charge,
0:31:43 > 0:31:47does not leave a bubble track in a bubble chamber.
0:31:47 > 0:31:50This neutral particle could then decay
0:31:50 > 0:31:54into another neutral particle with strangeness 0,
0:31:54 > 0:31:59which could decay into an electron-positron pair...
0:32:00 > 0:32:05..and, in addition, a particle with strangeness -1.
0:32:05 > 0:32:07The lambda.
0:32:08 > 0:32:13And finally, the lambda could decay into two charged particles,
0:32:13 > 0:32:18a proton and a pi meson, both with strangeness 0.
0:32:20 > 0:32:24This is a pattern for the omega minus decay.
0:32:24 > 0:32:29There are variations on this pattern and, in looking for the omega,
0:32:29 > 0:32:32we look for both this pattern and its variations.
0:32:33 > 0:32:36It was one thing the project these patterns.
0:32:36 > 0:32:40It was another thing to perform the experiment, to build the beam,
0:32:40 > 0:32:43to build a chamber, to get the pictures
0:32:43 > 0:32:45in which one would look for patterns,
0:32:45 > 0:32:48patterns which no-one else had ever seen
0:32:48 > 0:32:52and patterns which one didn't even know existed, a region unknown.
0:32:52 > 0:32:55Patterns predicted by particles which had been seen.
0:32:57 > 0:33:03We started to perform the experiment in earnest in November of 1963.
0:33:03 > 0:33:08In fact, we started tuning the beam round the clock, 24 hours a day.
0:33:08 > 0:33:10It certainly wasn't smooth sailing.
0:33:10 > 0:33:13We had many difficulties, technical.
0:33:14 > 0:33:17The line-up of the beam had to be constantly checked,
0:33:17 > 0:33:23magnets constantly tuned, the chamber had minor difficulties, leaks,
0:33:23 > 0:33:28but, finally, we persevered, worked very hard 24 hours round the clock
0:33:28 > 0:33:31until, in January, we were able to
0:33:31 > 0:33:35start taking a few Ks per picture, one to two Ks.
0:33:35 > 0:33:36We worked a little bit harder,
0:33:36 > 0:33:39we finally were able to get to three to four Ks per picture
0:33:39 > 0:33:41and, by late January,
0:33:41 > 0:33:45we were taking 2,000 pictures a roll, a few rolls a day,
0:33:45 > 0:33:48until, finally, we were able to obtain
0:33:48 > 0:33:51something of the order of 100,000 pictures.
0:33:51 > 0:33:54Of course, as soon as we had these pictures, we started scanning them,
0:33:54 > 0:33:57again, looking for these patterns.
0:33:57 > 0:34:00We scanned 10, 20, 30,000.
0:34:00 > 0:34:02Still no omega.
0:34:02 > 0:34:08Finally, we went to roll 53 and picture number 97,025 -
0:34:08 > 0:34:11that number stays in everyone's mind around here -
0:34:11 > 0:34:13and finally we found the omega.
0:34:13 > 0:34:15And here is a photograph of the omega.
0:34:16 > 0:34:21The pattern is very similar to the pattern I had shown you before.
0:34:21 > 0:34:26The strangeness -1, the strangeness -2, and the strangeness 0 particles.
0:34:26 > 0:34:30And this little particle, this little three-centimetre particle,
0:34:30 > 0:34:35this was the omega, the omega we spent months, years looking for.
0:34:35 > 0:34:36We were exuberant.
0:34:36 > 0:34:38I mean, the Friday that it was found,
0:34:38 > 0:34:41we just stood around looking at each other,
0:34:41 > 0:34:43a bit numb at the beginning,
0:34:43 > 0:34:45then finally everyone broke out into smiles
0:34:45 > 0:34:48and someone started to do a dance.
0:34:48 > 0:34:49It was very happy.
0:34:49 > 0:34:51In fact, in our exuberance,
0:34:51 > 0:34:54we just completely neglected to call Murray Gell-Mann in California.
0:34:54 > 0:34:58In fact, he had to call us when he found out about it.
0:34:58 > 0:35:00But it was a very peculiar feeling.
0:35:00 > 0:35:05It seems to make it all worthwhile, this one to two years' effort.
0:35:05 > 0:35:08You sort of stand around, a few of us, and you say,
0:35:08 > 0:35:12"At this moment, we few on the face of the Earth,
0:35:12 > 0:35:15"we are the only ones who know that this particle,
0:35:15 > 0:35:20"this omega that goes this short distance, this particle exists."
0:35:20 > 0:35:21Other people may think they know.
0:35:21 > 0:35:24Gell-Mann probably thought he knew, but he didn't know.
0:35:24 > 0:35:25We knew.
0:35:28 > 0:35:32FEYNMAN: That, then, is the story of the omega minus.
0:35:32 > 0:35:34What does it mean?
0:35:34 > 0:35:39What is the significance of the fact that nature seems to obey this rule?
0:35:41 > 0:35:42I think, today, nobody knows.
0:35:42 > 0:35:46We will only know, really, when we completely understand,
0:35:46 > 0:35:48or more completely understand,
0:35:48 > 0:35:51the fundamental laws of interaction of the nuclear particles
0:35:51 > 0:35:54and this is a vital step forwards to that understanding,
0:35:54 > 0:35:58but it isn't the understanding itself and, until we get that,
0:35:58 > 0:36:02we will not really know the meaning of this...the fact
0:36:02 > 0:36:07that nature seems to obey the rules guessed at by Gell-Mann and Ne'eman.
0:36:08 > 0:36:11It's analogous to the discovery of the periodic table
0:36:11 > 0:36:14by Mendeleev a century ago.
0:36:14 > 0:36:17He discovered at that time that various chemical elements
0:36:17 > 0:36:20came in families and that there were relations among them
0:36:20 > 0:36:23and that the chemistry of sodium and potassium, for example, were similar.
0:36:23 > 0:36:28This was extremely important in the development of science
0:36:28 > 0:36:31and the bringing about the ultimate understanding
0:36:31 > 0:36:33of the behaviour of atoms.
0:36:33 > 0:36:36But the real understanding of the reason why sodium
0:36:36 > 0:36:39and potassium were similar, why the periodicities among the chemistry...
0:36:39 > 0:36:42in the chemistry of the various elements existed,
0:36:42 > 0:36:47could only come 50 years later with the knowledge of atomic physics
0:36:47 > 0:36:49and this knowledge required
0:36:49 > 0:36:52a complete transformation of ideas about nature,
0:36:52 > 0:36:55a complete change of the philosophical position.
0:36:55 > 0:37:00Ideas that were impossible to appreciate at the time of Mendeleev -
0:37:00 > 0:37:04the principle of uncertainty of Heisenberg had to be discovered,
0:37:04 > 0:37:10the whole understanding of the relation of cause and effect
0:37:10 > 0:37:13had to be modified with the principle of indeterminacy.
0:37:13 > 0:37:15And so it is going to be here.
0:37:15 > 0:37:17We will not understand, really, what...
0:37:18 > 0:37:22..what nature, how nature finds... makes this rule
0:37:22 > 0:37:25until we understand the nuclear interactions,
0:37:25 > 0:37:29and we won't understand those, I'm sure, without a deep and profound
0:37:29 > 0:37:32transformation of ideas somewhere along the line.
0:37:34 > 0:37:36We already see some of the difficulties.
0:37:36 > 0:37:40This law of Gell-Mann and Ne'eman, this symmetry law,
0:37:40 > 0:37:42is not a perfect symmetry.
0:37:42 > 0:37:45If it were, the statement would be that the replacement
0:37:45 > 0:37:48of one particle by another would make no change.
0:37:48 > 0:37:50For example, the replacement of a neutron by a lambda
0:37:50 > 0:37:52should make no change.
0:37:52 > 0:37:56And yet, the neutron and lambda differ in mass alone by some 20%,
0:37:56 > 0:37:59so there alone is a change, that when you take neutron
0:37:59 > 0:38:01and replace it by a lambda, the mass is different.
0:38:01 > 0:38:05So, this symmetry is not perfect, it's an imperfect cemetery.
0:38:05 > 0:38:08Physicists are happy with a perfect symmetry.
0:38:08 > 0:38:11To say something is absolutely true and absolutely symmetrical
0:38:11 > 0:38:17seems to be a succinct, simple and elegant statement of a law of nature.
0:38:17 > 0:38:19If a thing were completely unsymmetrical
0:38:19 > 0:38:20then there would be nothing to say.
0:38:20 > 0:38:24But by what kind of a view is a thing
0:38:24 > 0:38:28that is only partly symmetrical natural,
0:38:28 > 0:38:31is a thing that is only partly symmetrical beautiful?
0:38:31 > 0:38:35Well, the artists say that, in this camellia bush here,
0:38:35 > 0:38:37the artists feel that the camellia,
0:38:37 > 0:38:41in its partial but near symmetry, is especially beautiful
0:38:41 > 0:38:44and far more beautiful than a perfect geometrical pattern.
0:38:44 > 0:38:47But physicists feel that a partial symmetry
0:38:47 > 0:38:49is an indication that some deeper
0:38:49 > 0:38:51and more profound description of nature
0:38:51 > 0:38:55is possible, that there is "gold in them thar hills".
0:38:57 > 0:39:01So, we've got a peculiar thought to grapple with, this partial symmetry.
0:39:01 > 0:39:02We're kind of stuck.
0:39:02 > 0:39:04We need a new idea.
0:39:04 > 0:39:07Before we'll really get the nuclear forces understood,
0:39:07 > 0:39:08some great new idea is required.
0:39:08 > 0:39:11Looking for symmetry is an old one.
0:39:11 > 0:39:15Poincare suggested it, Einstein used it,
0:39:15 > 0:39:18it really came into its own when quantum mechanics was developed.
0:39:20 > 0:39:22But the only information that we're accumulating,
0:39:22 > 0:39:25the places where they were really getting stuck,
0:39:25 > 0:39:27understanding the relation of these particles
0:39:27 > 0:39:30is somewhere where we are missing...
0:39:30 > 0:39:35some important great idea, we have some prejudice that's in our way.
0:39:35 > 0:39:38That's the way it always is in these pinnacle discoveries.
0:39:38 > 0:39:42The big pile-up of stuff, all the old things that you've thought of before,
0:39:42 > 0:39:44you try again and again.
0:39:44 > 0:39:46But the great discovery always involves
0:39:46 > 0:39:48a great philosophical surprise.
0:39:50 > 0:39:53The pinnacle discovery isn't so much a fact...
0:39:54 > 0:39:56..as that it's possible to look at nature
0:39:56 > 0:39:58in a thoroughgoingly different idea.
0:39:58 > 0:40:00How strange it is. Listen to this.
0:40:00 > 0:40:02How much is known after 200 years of studying physics?
0:40:02 > 0:40:06How much is known about electrons, light, everything?
0:40:06 > 0:40:09And in order to understand the nuclear forces,
0:40:09 > 0:40:12it's almost certain that we are going to have to take
0:40:12 > 0:40:16a completely different view about everything that we know already,
0:40:16 > 0:40:17philosophically, that is.
0:40:17 > 0:40:21We're going to have to find another way to look at the world
0:40:21 > 0:40:24in which everything that we've already found out about
0:40:24 > 0:40:25is the way it is.
0:40:25 > 0:40:28And yet, that little detail about what goes on in the nucleus
0:40:28 > 0:40:30then falls into place.
0:40:30 > 0:40:31It's a very hard job.
0:40:31 > 0:40:33It's lots of work.
0:40:33 > 0:40:34So, what do we do it for?
0:40:34 > 0:40:36Because of the excitement,
0:40:36 > 0:40:39because of the fact that each time we get one of these things...
0:40:40 > 0:40:44..we have a terrific Eldorado, we have a wonderful...
0:40:46 > 0:40:47..new view of nature.
0:40:47 > 0:40:50We see the ingenuity, if I may put it that way, of nature herself,
0:40:50 > 0:40:53the peculiarity of the way she works.
0:40:53 > 0:40:56It takes a terrible strain on the mind to understand these things
0:40:56 > 0:41:00and the real value of the development of the science in this connection,
0:41:00 > 0:41:02the thing that makes me go on...
0:41:03 > 0:41:07..is this...the difficulty of understanding it.
0:41:07 > 0:41:11That these apes stand around and look at...nature
0:41:11 > 0:41:13and find that to really catch on,
0:41:13 > 0:41:16they have to polish their mind to the very last.
0:41:16 > 0:41:20We live in a heroic age, we live in a moment that will never come again.
0:41:20 > 0:41:22These discoveries cannot be made twice.
0:41:22 > 0:41:26One doesn't discover America two or three times in succession, really.
0:41:26 > 0:41:30And one doesn't discover the laws of nuclear forces or electricity
0:41:30 > 0:41:32more than once.
0:41:32 > 0:41:35People say, some people say, our age is meaningless.
0:41:35 > 0:41:40Those are only people who don't know what we're doing in this age.
0:41:40 > 0:41:43That this age is the age in which mankind is finding out
0:41:43 > 0:41:46about the nature that he lives in.
0:41:47 > 0:41:49And if they don't understand what's already been uncovered,
0:41:49 > 0:41:51they can't appreciate the search.
0:41:53 > 0:41:57What makes us so sure that the new discovery of the interrelationship
0:41:57 > 0:41:59between the nuclear forces is going to be so wonderful?
0:41:59 > 0:42:01How do we know it isn't going to be
0:42:01 > 0:42:03some complicated, dirty or simple thing?
0:42:03 > 0:42:05We don't know. But we keep on trying anyway.
0:42:05 > 0:42:08We're not sure, it's worth the risk,
0:42:08 > 0:42:10because it's very likely it'll be peculiar,
0:42:10 > 0:42:12and if it is, it'll be very interesting.
0:42:12 > 0:42:15How long is it going to take?
0:42:15 > 0:42:16Do we have all the clues?
0:42:18 > 0:42:23Every time there's been a very great discovery, one can look back and say,
0:42:23 > 0:42:24"Why didn't we think of that before?"
0:42:24 > 0:42:26Of course, there's a time so far before that you say,
0:42:26 > 0:42:28"Well, the reason they didn't think of it
0:42:28 > 0:42:30"is they didn't have enough facts from experiments."
0:42:30 > 0:42:31Question.
0:42:31 > 0:42:34Do we have enough facts from experiments so that,
0:42:34 > 0:42:35after this thing is discovered,
0:42:35 > 0:42:38people will look back and say, "Why didn't they think of that before?"
0:42:38 > 0:42:40How far before? In 1964.
0:42:40 > 0:42:44My colleagues don't agree with me, but I think this is the day.
0:42:44 > 0:42:46I think that we now know enough
0:42:46 > 0:42:49that if, with a sufficiently clear reasoning,
0:42:49 > 0:42:50we could come to the answer.
0:42:50 > 0:42:53I'll put it another way, when we do finally find the answer,
0:42:53 > 0:42:57after the experiments have given us too many clues, a lot of extra clues,
0:42:57 > 0:42:58we'll look back and we'll see
0:42:58 > 0:43:01how a perfectly sensible, logical line of reasoning,
0:43:01 > 0:43:02from the present position,
0:43:02 > 0:43:04could have brought us to the present understanding.
0:43:04 > 0:43:07I wouldn't have said that before the discovery of the omega minus.
0:43:07 > 0:43:10That, to me, is the significance of this discovery.