At the same time, I was continuing my own work. After Fermi's death Pasta and I decided to continue exploratory heuristic experimental work on electronic computers in mathematical and physical problems. We felt that the combination of classical mechanics and astronomy problems lent itself to two kinds of studies: one, the behavior of large numbers of particles — call them stars — in a cluster or galaxy; the other, the history of a single mass of gas as it developed from initial conditions by contraction at first, perhaps giving rise to a double or multiple star, then generating more and more nuclear reactions, exhausting its nuclear material, and finally perhaps collapsing. Many calculations have been done since on this latter problem over the last twenty years, changing the whole understanding of astrophysics and of the development of the universe as far as individual stars are concerned.
The problem of clusters of stars was I think the first study of this nature using computers. We took a great number of mass points representing stars in a cluster. The idea was to see what would happen in the long-range time scale of thousands of years to the spherical-looking cluster whose initial conditions imitated the actual motions of such stars. This was a really pioneering calculation showing that this sort of investigation was possible. It gave very curious and unexpected observations in classical mechanics, formation of subgroups, and contractions. We made a film of these motions on an accelerated scale which showed these interesting phenomena. This work gave rise to other studies of this sort at Berkeley, in France, and elsewhere.
Another problem which I attacked but which is still not solved is an attempt to see what will happen when a mass of gas of very large dimensions, say of the whole solar system, at very low density and having initially a mild amount of turbulence starts to contract. How would it contract, and how would it finally form a star? What is interesting and the actual purpose of the problem was to see whether and how often it would form a double, triple, or multiple star. The reason for this curiosity is that many stars, in our neighborhood at least, are double. According to recent studies, at least one star out of three is multiple. It would be nice to see by brute-force calculations how a contraction of an irregularly shaped mass of gas develops. Beyond all this is the problem of the formation and development of galaxies — that is, the assemblies of billions of stars. On this, too, astrophysicists have accomplished much with the aid of computers.
While such astrophysical calculations were going on, I began in an amateurish way to work on some questions of biology. After reading about the new discoveries in molecular biology which were coming fast, I became curious about a conceptual role which mathematical ideas could play in biology. If I may paraphrase one of President Kennedy's famous statements, I was interested in "not what mathematics can do for biology but what biology can do for mathematics." I believe that new mathematical schemata, new systems of axioms, certainly new systems of mathematical structures will be suggested by the study of the living world. Its combinatorial arrangements may lead us in the future to a logic and mathematics of a different nature from what we know now. The reader is referred to one of my papers on mathematical biology. Too technical to be included here, it is listed in the bibliography at the end of this volume.
My interest in biology took a more tangible form when I engaged in discussions with James Tuck, and we talked to the biologists in the laboratory. Los Alamos had always had a division for the studies of biological effects of radiation. Radioactive damage was, of course, one of the first things to worry about from the beginning of the nuclear age. With Tuck, and Gordon Gould and Donald Peterson from the Health Division, we organized a seminar devoted to current problems of cellular biology and the new results in molecular biology. I really learned a lot about the elementary facts of biology there, the role of cells, their structure, and so on. The seminars, which had about twenty participants, have had important consequences, although they lasted only two years. Two of the participants, Los Alamos physicists Walter Goad and George Bell, both extremely brilliant and talented, and among the best young brains in these fields in the country, are doing a lot of biology research now. Goad is working in the field of biological mathematics, while Bell has some new ideas on immunology. Ted Puck from Colorado visited the seminar and gave some lectures.
I met Puck shortly after the war and found him to be full of new ideas, suggesting interesting experiments and methods for the study of the behavior of cells and problems in molecular biology in general. I think it was Ted Puck's group which first succeeded in keeping mammalian cells alive and even multiplying in vitro. I always look forward to discussions with him; it was he who arranged for me to give seminars for the faculty and young researchers in the biophysics department and even succeeded in having me appointed a member of the professorial staff at the University of Colorado's Medical School. I told him that, being a beginner and a layman in this field, I might be arrested for impersonating a doctor.
Almost every month there are fascinating new facts discovered in biology. It is now widely recognized that the discoveries of Crick and Watson have opened up a new era in the psychological attitudes in biology as well. Years ago at Harvard, when I talked to biologists and tried to ask about or propose even a mildly general statement, there would always be the retort: "It isn't so because there is an exception in such and such an insect" or "such and such a fish is different." There was a general distrust or at least a hesitation to formulate anything of even a slightly general nature. This attitude has drastically changed since the discovery of the role of DNA and the mechanism of replication of the cell and of the code which seem so universal.
During all these years I did not live continuously in Los Alamos. I spent periods of time as a visiting professor at Harvard, MIT, the University of California in La Jolla, the University of Colorado, plus innumerable visits to various universities, scientific meetings, and government or industrial laboratories, where I gave lectures and consultations. These latter were called business trips. If one adds our almost yearly vacations in Europe since 1950 (mainly in France where Françoise still has relatives and I have many scientific friends), it seems to me that about twenty-five percent of my time was spent away from Los Alamos.
It was in those periods that my friendship with Victor Weisskopf developed. I had met him in Los Alamos during the war when he was Bethe's alternate as leader of the theoretical division. He left at the war's end to become professor at MIT and our relationship deepened during my visits to Cambridge, Harvard and MIT.
Viki, as he is universally called, is a theoretical physicist. He made a name for himself as a young man with his important work on problems of radiation in quantum theory. He was for a time assistant to Pauli and also worked in Copenhagen at the famous Niels Bohr Institute. Viki was born in Vienna, a fact I take note of because he exhibits the best side of the Viennese temperament. This is contained in the following saying: In post-World-War-I Berlin people used to say, "The situation is desperate but not hopeless"; in Vienna they said, "The situation is hopeless but not serious." This certain insouciance combined with the highest intelligence has enabled Viki to navigate not only through the usual difficulties of administrative and academic affairs — he has been, among other things, director-general of CERN (the European Center for Nuclear Research) near Geneva and chairman of the large physics department at MIT — but also in the more abstract realm of the intellectual and scientific difficulties of theoretical physics. I would say his intellectual stability is based on a real knowledge of and feeling for the spirit of the history of physics. This he has achieved through perspective and comprehension, sifting and evaluation of the quickly changing scene in the physical theories which concern the very foundations of this science. I should add here for the benefit of the reader who is not a professional physicist that the last thirty years or so have been a period of kaleidoscopically changing explanations of the increasingly strange world of elementary particles and of fields of force. A number of extremely talented theorists vie with each other in learned and clever attempts to explain and order the constant flow of experimental results which, or so it seems to me, almost perversely cast doubts about the just completed theoretical formulations. Through all this turmoil in the overly mathematical theoretical physics research, constant good progress has been made, but it takes a person like Viki (and really there are no more such than one can count on the fingers of one hand) to stabilize this flow and extract the gist of the new elaborations of the ideas of quantum theory and to be able to explain and describe it both to the physicists themselves and to the more general public.