Maker of Patterns

by Freeman Dyson

  That was the last year of the Chinese civil war, when the victorious army of Mao Zedong was defeating the disorganized government forces of Chiang Kai-shek. China, ravaged by years of Japanese occupation and years of civil war, was in desperate need of peace. One year later Chiang with the remnants of his army was driven into exile in Taiwan, and Mao was in Beijing proclaiming the birth of the People’s Republic of China. Ning Hu, well aware of the political risks and material hardships that awaited him, decided to return to China. He returned in 1951 and was well treated by the Communist regime. He enjoyed a distinguished career as teacher and researcher until his death in 1997.

  Sheila Power is also a person I am glad to get to know. She is a Catholic like Cécile, but in every other respect as unlike as possible, quiet and unassuming and un-formidable. Cécile now seems to have decided that ordinary buses and trains are much too slow for her; this weekend she is spending at Chicago, flying there and back, and at Christmas she is to fly to Denver, Colorado, for a week’s skiing holiday. Fortunately she always seems to have plenty of money.

  I enjoyed having Cécile as a colleague and companion but had no wish to become involved with her personally. The word that best described her was formidable, either in English or French. We liked to make jokes about her role as a modern version of Joan of Arc, the young girl who put on soldier’s clothes and led the French army to defeat the English at Orléans in 1429. Cécile herself accepted this role and later used her summer school at Les Houches to lead a revolution in the teaching of physics in France.

  DECEMBER 4, 1948

  We are all watching anxiously to see if the Soviet physicists are in for serious trouble. The recent newspaper attacks on them are nothing new and are not necessarily indicating anything more than the idiotic arguments that have been going on for twenty years or more. However, in view of what happened to the biologists, the outlook is pretty black. The issue in physics is curiously parallel to the issue in biology. Mendel’s laws imposed limitations on the possibility of improving stocks by selective breeding; Heisenberg’s uncertainty principle imposed limitations on the predictability of atomic events. Such limitations are contrary to dialectical materialism; hence Mendel and Heisenberg are anathema. Also, Mendel and Heisenberg are easy targets for political attack, Mendel for being a priest, and Heisenberg for being head of Hitler’s atomic energy project.

  In the Russian translation of Dirac’s book Quantum Mechanics, published as long ago as 1935, there is a preface inserted which says, “Although this book contains numerous errors and fallacies which are in contradiction with the well-known principles of dialectical materialism, nevertheless it contains so much that will be of value to the judicious student that the editors have felt themselves justified in publishing it without correction or alteration.” A very fine piece of diplomacy on the part of the editors. With the help of a few sops like this to the rabid Marxists, the physicists up till 1948 have continued to work and publish results, making full use of Heisenberg, Dirac, or anybody else, and their papers are as sensible as anybody else’s.

  Now just as in biology a Lysenko can get good results in practice, whether his theory is sound or not, so in physics it happens that nuclear fission is one phenomenon that can be fully understood and exploited, using only the crudest kind of quantum theory. In fact, fission is almost a “classical” phenomenon, in the sense that it takes less quantum theory to understand it than it does to understand the reaction hydrogen plus oxygen goes to water. Not only fission, but most of nuclear physics as it has so far developed, is likewise independent of highbrow theory. In view of this, it would not be at all surprising if the Russian government, wishing to get ahead as fast as possible with atomic energy, should support physicists who work on practical developments in empirical nuclear physics, and should attack those who work on the deeper theories, which everyone agrees will not be of much help to the experimenters in the foreseeable future. It is greatly to the credit of Soviet physics that so far no Lysenko has arisen among the physicists to lead the first group in attacking the second. Perhaps also the government’s tolerance of the theoreticians is an indication that the Soviet atomic energy project is going ahead smoothly without them. But this is wild speculation.

  Trofim Lysenko was a plant breeder who did tremendous damage to biology in the Soviet Union, using the power of the Communist Party to kill or imprison many leading biologists. He was a fanatical Marxist and believed that modern molecular biology must be suppressed because it was incompatible with orthodox Marxist dogma. As a result of Lysenko’s persecutions, a whole generation of Soviet biology was devastated. Fortunately, the physicists were able to stand firm against Marxist dogma, and no Lysenko arose to devastate Soviet physics.

  On Tuesday I went to have a quiet talk with Oppenheimer reviewing my seminar talks. He was extremely pleasant and said he agreed with all my main contentions. He had no concrete proposals to make for going further with the theory but advised me to follow my destiny and go on thinking about it until I had squeezed all I could out of it. At the end he asked me what I was intending to do after this year, and when I said I would go back to England, he warmly approved, saying I should try hard to resist the temptation to settle permanently in the States. At the end he said, “You know Dirac and Bohr feel that their proper place is in England and Denmark, and I have an arrangement that they can come to the institute one year in three or thereabouts, so as to keep in touch with people over here. Certainly we shall be able to do something of the kind for you too.”

  This kind of talk is vastly satisfying to my ego. But I think it is rather silly. Oppenheimer has absolutely no evidence on which he can place me in the same class with Dirac and Bohr, and it is far from clear to me whether I shall ever achieve their kind of distinction. And in any case it would do England no harm if I stayed here for a few years to learn some physics before going back to teach it there. I think his remarks are chiefly interesting as a key to his own character and an explanation of his previous behaviour. It is just this sudden and exaggerated enthusiasm which he showed when Schwinger first produced his theory, and the sudden and exaggerated lack of enthusiasm with which he viewed Schwinger and Feynman when I began my talks. He is a curious mixture, so cool and accurate in his speech and appearance and so nervous and unstable inside.

  Sheila Power and Ning Hu arranged on Wednesday to make a joint expedition with me to the Princeton Art Museum where there was a special exhibition of Chinese painting. It was Ning Hu’s last day in Princeton. We had with us also Professor Liu, a delightful man, old and round and exactly like the philosophers depicted in some of the paintings; he is a great scholar (in Chinese classics) and is professor of Chinese here. He was for some years a lecturer at Oxford. The collection was extremely good, just three rooms and as much as one could digest in a morning. Professor Liu told us the personal histories of the painters, the things to look for in the paintings, and translated for us the poems which most of the paintings had written beneath or beside them. It was a delightful morning, and I have never before understood and enjoyed Chinese painting so well. Ning Hu maintains that there are only two outstanding artistic achievements, and he places these two on an equal footing. They are, Western music and Eastern painting. You will realise at once what a difference it makes, when you are confronted with twenty paintings from every school and region of China and from eight centuries of time, to be told which is which and why it is different from the others. Just as it is easier to enjoy European painting after you have been told, and grown accustomed to, the difference in time and place between Botticelli and Constable.

  DECEMBER 11, 1948

  Bethe was here again on Wednesday, with great news from Cornell. The three places where big synchrotrons are in an advanced stage of construction are Berkeley, Massachusetts Institute of Technology, and Cornell. Of these places, Berkeley makes the most noise and spends the most money, MIT next, and Cornell least. All three machines are now completely built, and it only remains for difficul
t final adjustments to be made before they will work. A week ago, as a result of some clever tricks on the part of Wilson, who is in charge at Cornell, the Cornell machine produced a beam of electrons. Wilson had the pleasure of ringing up Edwin McMillan (the original inventor of the synchrotron) on the long-distance phone to California, and telling him how to make his machine work. Three days later, the Berkeley machine produced a beam. The beams so far are at low energies. But once you have a beam it is not difficult to increase the energy gradually to its full value, and this should not take more than a few weeks. The bad situation is when you don’t have a beam and don’t know why you don’t have a beam. When they get the beam up to full energy, then we shall begin to learn something about mesons and nuclear forces. I am planning a long visit to Cornell as soon as this begins, and Bethe said he would be glad to see me.

  DECEMBER 24, 1948

  There has been great excitement over a new discovery by Powell at Bristol. Powell always keeps one step ahead of everyone else. A year and a half ago he discovered the so-called pi meson and helped very much the people at Berkeley who subsequently made the animals in their machine. Now he has a new meson which is called a tau meson, three times as heavy as the pi. This is likely to be for several years beyond the capacity of any machines to make, because the larger mass takes a proportionately large energy to create it. Powell found his meson in a photographic plate which he put at the top of a mountain in Switzerland. The main reason for the success was that he was using a new and improved type of photographic plate developed by a man called Berriman at the English Kodak company. The whole research is a joint effort between the Bristol group and the photographic companies.

  • 8 •

  WELL, DOC, YOU’RE IN

  THE SPRING OF 1949 was the high point of my life as a scientist, when I enjoyed for a few dizzy weeks the status of a rock star. I began the year by writing a second long paper, forging out of quantum electrodynamics a practical tool for the accurate calculation of physical processes outside the nucleus. I was confident, with a confidence shared by Oppenheimer, that the new tool could be extended to give us an accurate theory of nuclear processes. I looked forward to a second triumph, when the mysteries of the nucleus would be explained. After 1949 my hopes gradually faded. Accurate high-energy experiments showed that nuclear processes are far more complicated than I had imagined. Fifteen years later Murray Gell-Mann and George Zweig discovered quarks, which gave us a deeper understanding of all aspects of the subatomic world. It turned out that every nuclear particle is a little bag of quarks. This discovery opened the door to beautiful new theories of nuclear interactions, but made the calculation of the consequences of the theories more messy. Without quarks, my theory could never have succeeded.

  JANUARY 22, 1949

  Next week we shall all be in New York at the annual Physical Society meeting. Oppenheimer will give a half-hour talk reviewing the state of physics, which he should do very well if he is up to his usual form. He is particularly good at defining problems and issues when a subject is in a confused state. A good example of his style of presentation occurred the other day at lunch, when I unexpectedly asked him whether he would advise me to choose Birmingham, Bristol, or Cambridge as my next home. He replied without a moment’s hesitation, “Well, Birmingham has much the best theoretical physicist to work with, Peierls. Bristol has much the best experimental physicist, Powell. Cambridge has some excellent architecture. You can take your choice.” I made up my mind for Birmingham and wrote a letter to Peierls accepting his offer of a fellowship.

  This week I began once more to think in a fundamental way, having got the second paper off my mind. The second paper was still concerned with physics outside the nucleus. Now, having got the theory into such a handy and powerful shape, I have decided to sally forth and apply these methods to the nucleus. Almost at once I began to get encouraging results.

  Today Bethe came over from Columbia. In the afternoon we had a conference with various people reporting on what they had been doing. Several people of the younger group talked about their calculations, many of which have been done with Feynman methods and have given sensible results. At the end I got up and told them one of the things I had found in the last three days since I started thinking about the nucleus. I think it really startled them, because one of the oldest and most intractable difficulties of the nuclear theory dissolved under their eyes. Always in the past there has been an unbridgeable gap between two kinds of nuclear theory. There is the so-called phenomenological theory, in which the particles are treated as having a certain size, and their properties can then be described with some degree of resemblance to the facts, although it is known that this theory cannot be right since it does not agree with relativity. The other theory is the field theory, which is the only theory which is properly relativistic, and this theory treats the particles as points without size and always gives forces between the particles which are completely wrong and often infinite. What I did in my talk was to take a simple example of the field theory and treat it with the new methods. In no time at all one could see that the point particles were behaving as if they had a finite size, which is just what one wants them to do, and that the forces between them were sensible. Oppenheimer was extremely pleased with this and produced a paper which he had written in 1941, in which he had written down exactly the same formulae as I had for the nuclear force. In his paper these formulae were guesses, based on physical intuition; and now they can at least roughly be derived from a consistent theory. The whole thing is still in a preliminary stage and may not turn out as well as it promises. If it goes, it will give me plenty to think about and enough material for another big paper before long.

  Roughly speaking, the difference between my view of the world and Oppenheimer’s has been narrowed down to a question of how much can be got out of the nucleus. We are agreed that the existing methods of field theory are not satisfactory and must ultimately be scrapped in favour of a theory which is physically more intelligible and less arbitrary. We also agree that the final theory should explain why there are the various types of particle which we see and no more. However, Oppenheimer believes that the nature of the nuclear forces will itself give us enough information on which to build the new theory. In other words, the nuclear forces will not be describable at all except in terms of a theory which explains the existence of elementary particles. I take a more pessimistic view, that we shall be able to give a complete account of the nucleus on the basis of the present field theory. If I am right, the discovery of a finally satisfactory theory of elementary particles will be a much deeper problem than those we are tackling at present and may very well not be achieved within the framework of microscopic physics. Probably the reason for our disagreement is largely a matter of history. Oppenheimer has spent all his life seeing the field theory fail on one problem after another, whereas I have grown up during one of its brief periods of success.

  Bethe told me he was very glad I had decided to go to Birmingham. He had a rather despondent letter from Peierls, saying that he had nobody at Birmingham who knew anything and was himself getting too old to supply all the imagination for the department. From this it looks as if I shall have it pretty much all to myself, especially as Peierls spends a lot of his time on official business. If it is like this, I shall have a tough time trying to carry on my own research and also teach the other people physics. However, it is amazing how one can adjust oneself to circumstances.

  Oppenheimer told me that when he came back from Europe as a young man about my age, he had the same kind of problem, being offered jobs as professor at Berkeley and also at Pasadena four hundred miles south, two places which were at the time equally lacking in people who knew any theoretical physics. For some time he hesitated, then accepted both jobs and divided his time between them. And he very soon had under him the best school of theoretical physics in the country.

  His students mostly migrated with him north and south each year, spending the fall in Berkeley a
nd the spring at Caltech in Pasadena.

  JANUARY 30, 1949

  I talk some more about the history of Oppenheimer’s relation with the government. At the end of the war, the contact between the government and the scientific people was practically nonexistent; there were a lot of scientists who were clamouring loudly for internationalization of atomic energy, without being very specific about the methods for achieving it; and the government on the whole was not inclined to take them seriously. In this atmosphere, it was largely the personal persistence of Oppenheimer, who walked uninvited into the State Department and pleaded with the officials to do something about it, that resulted in the government accepting the idea of international control. He succeeded in winning and maintaining the confidence of these officials, and avoided on the one hand giving the appearance of being a fanatic and on the other hand accepting any essential compromise on the main issues. It is unfortunately only too easy to think of many scientists who in his position would have made either the one or the other mistake.

  The negotiations aimed at an international control of nuclear energy and nuclear weapons continued for several years at the United Nations. There was probably never any chance that an effective international control would have been acceptable to the Soviet Union. The most that Oppenheimer could achieve was a set of proposals for international control, agreed by both parties in the U.S. government and sincerely offered to the international community. The proposals were rejected by the Soviet Union. They were a serious effort by the United States to change the course of history and put a stop to the nuclear arms race.