Oral History Transcript — Hans A. Bethe
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Interview with Hans A. Bethe
Hans A. Bethe; May 8, 1972
ABSTRACT:Natural radioactivity; ideas of nuclear constitution, size in 1920s; Gamow-Condon-Gurney theory of alpha decay 1928; discovery of neutron 1932; Cambridge as a center of research 1933; early theories of nuclear forces; analysis of short-range nuclear forces 1935-40; reasons for writing Rev. Mod. Phys. review articles 1935-37 and detailed review of articles' contents; beta decay and the neutrino hypothesis; application of group-theoretic methods to nuclear physics 1936-37; compound nucleus model 1936; nuclear models in general (compound nucleus, evaporation, liquid drop, direct interaction, statistical); contemporary knowledge of nuclear physics 1938-39; stellar energy production; energy limit on cyclotron; accelerators and theoreticians; nuclear physics at Los Alamos; post-war conferences; origins and development of the shell model of the nucleus; many-body theory in nuclear physics; current algebras in particle physics; origins and development of the optical model; of the collective model; autobiographical comments on political, social, scientific conditions in Germany and England in early 1930s ; nuclear studies at Cornell after the war; building the H-bomb; the Oppenheimer hearings; work as a consultant 1950-1970; involvement with PSAC 1956; views on disarmament; receipt of 1967 Nobel Prize.
WEINER:Today is the 8th of May, 1972. We are sitting in Professor Bethe's office in the Newman Laboratory at Cornell, and this is Charles Weiner.
BETHE:It is nice to see you here again, and I hope this will be as interesting as the last two times.
WEINER:I am sure it will be. I think we left off just at the period when you had come back from Los Alamos and recruitment was beginning here at Cornell. I know that in this period people like Feynman came back here from Los Alamos, but some of the people who had been here earlier also came back as well — Bob Bacher, for example. I think we had begun to talk about plans developing already at Los Alamos for what one would do at one's own institution in the postwar period. I think we got you back here. The first question I would like to ask about that is — the plans for the electron synchrotron started here reasonably soon after the end of the war — at least on the surface one finds consideration of it in, I think, '47, and I'm curious to know whether this had come about even earlier.
BETHE:It was even earlier than that — I think already back at Los Alamos and certainly as soon as Bacher and I were back here we talked about a machine to go to high energy and to make mesons. I couldn't say the exact date but we certainly wanted to make mesons. We discussed for some time whether we should use an electron machine or a proton machine. We found that lots of other universities were planning proton machines. They were fairly expensive. We decided for the electron machine very largely because we wanted to do something different, and partly because we thought it would be a little less expensive. We were right about the latter. Electron machines were less expensive by factors of two or three, at least at that time. And I think we had more luck than good sense because in the course of time it turned out man and more that electron machines are extremely fruitful. We knew already at the time that with electrons you have one great advantage, namely, the electron's interaction is well-known. It has no nuclear interaction but only electromagnetic interaction. That had proved true for the entire period of now 26 years, and in the meantime, I think most people are convinced that many things are explored better with electrons. We would have been satisfied at the time just saying "just as well as with protons."
WEINER:When you said that it would be cheaper, had you in mind a source of funds for the machine?
BETHE:Not very clearly to start with. We hoped very much that it could be financed by the government somehow. Then, at some time, the Office of Naval Research was established — I forget exactly when, you may know, I think it probably was still in '46 — and that, therefore, was the obvious source to apply to. I think the Office of Naval Research was established before the AEC and therefore that naturally was the organization we applied to.
WEINER:Had they sought you out in terms of deciding on certain institutions where it was logical....
BETHE:I think we sought them out but I am not very sure — with the mechanics, I had nothing to do. I think it was Bob Bacher who did that. He was then the chief experimental physicist here in nuclear physics and he was the director of the Laboratory of Nuclear Studies. I think I probably covered already the point that we proposed to the university that we have a separate Laboratory of Nuclear Studies inside the physics department but with its own budget and that this would be essential in order to have enough freedom of appointment and enough time for research. Our idea at the time was that half the time of each professor in the Laboratory should be devoted to research which was not at all commonly accepted in the university before the war.
WEINER:Had you any model in mind or any other institution where this was going on?
BETHE:No. There were other institutions/founded similar laboratories. There was MIT which had a fairly large enterprise, much larger than ours, with a large number of research associate positions. There was Chicago which instituted the Laboratory of Solid State Physics and of Nuclear Physics at the time. And so I would say it was in the air. I don't think we copied the others, but people talked to each other and this idea was tried out in a number of universities at the same time.
WEINER:I was thinking of perhaps the Berkeley model in the thirties where the Radiation Laboratory grew out of the physics department and had independent funding after a while.
BETHE:Not very consciously.
WEINER:This postwar effort — you say the mechanics of it were mostly handled by Bacher — was he the major proponent of it and had it occurred to several of you simultaneously?
BETHE:Within our group we talked to each other all the time. I think Bacher and I were probably — I don't recall for sure — the only full professors who were specifically interested in nuclear studies. There was a big group of younger people — Feynman in theory, McDaniel, Corson, De Wire, Charles Baker who is now at Brookhaven National Laboratory and maybe two or three others. We discussed all these plans in the whole group and not just one of us.
WEINER:But the initial discussions started already at Los Alamos?
BETHE:Yes. But I think the electron synchrotron idea or the electron accelerator idea probably became formulated only when we were back here.
WEINER:And you would date that about '46, because there was a gradual trickling back of people. Not everyone was back here at that time.
BETHE:Yes. It was fairly substantial in our case. Most people came back for the spring term of '46. Perhaps two only came for the fall term. Morrison I forgot to mention — he was one of the important members. And Feynman came already for the fall of '45.
WEINER:I remember the story of his arrival here.
BETHE:Yes. Now, we had the idea of an electron machine. The question was: became what energy this should have? I became a consultant at the time to the General Electric Research Laboratory who were manufacturing betatrons of an energy of about 100 MeV. They were claiming that they had seen mesons, and my first activity in this connection was to show that they had not produced mesons, but that what they were seeing were some proton tracks which were curved by multiple scattering instead of by deflection in a magnetic field. They never published that.
WEINER:Who was involved on their end? Was Harvey Brooks there at the time?
BETHE:Harvey Brooks was there but he was only negatively involved in it, and I will come to that in a minute. Their chief experimental consultant was Marcel Schein of the University of Cosmic Rays of Chicago. They had quite a number of quite good people of the Research Laboratory involved but I have completely forgotten their names. Maybe me of them was Pollock, but I am not sure. The story was that they had these tracks and were very proud of them and wanted to advertise their betatron with the idea that it could make mesons. This contradicted the measured mass of the mu meson which was a little over 100 MeV. They had only 70 MeV. So I looked at those tracks and looked for ways to show that they were not mesons. They were apparently not electrons because they didn't make showers and so the main idea was that they could be protons. Then I looked at the multiple scattering in the gas — they had a rather high gas pressure and rather low magnetic field and I soon found out they could that very well be protons and/what was measured was just multiple scattering in the gas and not deflection by the magnetic field. There is one paper on that: "Multiple Scattering and the Mass of the Mesons," which is the only paper that was ever published on the subject, because they then did not publish their paper.
WEINER:Did they have a tendency to try to bring in other experts to refute your interpretation?
BETHE:Harvey Brooks was at the discussions and he was very soon convinced by my argument and supported me strongly, and between him and me we persuaded them not to publish.
WEINER:Had they had so-called outside physicists as consultants prior to that time?
BETHE:I don't think so, not in any large number, certainly not in these fields which are rather remote from their real business. They must have had some connection with Don Kerst, now of Wisconsin, because the development of the betatron was done in some collaboration with Kerst. I don't know the details on that. But they began very seriously in early '46 to get themselves outside consultants. They also got some younger consultants. Feynman was eagerly accepted by them on my suggestion. There were three or four others who came just for a short time in the summer of '46. One of the results of that was my book on elementary nuclear theory. They wanted very much to learn nuclear theory. I think they expected much more business from the nucleus than was finally forthcoming. So they asked a large number of their research staff to listen to these lectures. Then three of the young men who were summer consultants were asked to write up the notes and that finally made the book.
WEINER:It was the series of talks you gave there — and the level of the people would be engineers?
BETHE:Yes, engineers and physicists.
WEINER:It is interesting that even before the war that Westinghouse with Condon was looking into the same question, and I just discovered the other day that Bell Labs was too.
BETHE:I didn't know that.
WEINER:They were even discussing whether they should get a cyclotron or a Van de Graaff — this was about 1938.
BETHE:I didn't know that. At that time they were talking about using the betatron for actual experimentation of their own, and that's what they were very interested in.
WEINER:But they also wanted to manufacture them and sell them. And it wasn't a question then of reactors at that time — the only market then would be for the instruments. And the experimentation would be basic research which would perhaps lead to some product? My question is: where they thought the betatron their would lead them in terms of long-range commercial mission, in addition to selling machines (but I don't know if the experimental results have anything to do with selling machines)?
BETHE:I don't really know and I wasn't close enough to the center of decision at any time to find out just what was on their mind. They seemed seriously interested in nuclear experimentation. They did afterwards build a synchrotron, in fact, a synchrotron without iron, and did some experimentation on it. There is one man here, Professor Littauer, who was with the G.E. group when they actually made that so-called air-core synchrotron work and did a couple of experiments with it. But it never got very far. I don't know what they had themselves in mind. I assume that they wanted to establish as competent in the field and perhaps use this as persuasion for people to buy their betatrons.
WEINER:Or of attracting scientists who then could work on some other problems, as they attracted you and others that summer. Now was it during this period that you were already beginning your plans for the machine here?
WEINER:Before I take you on that line, may I ask another question? Was this your first experience as a consultant to industry?
WEINER:And it just came along naturally as a consequence of the war?
BETHE:They approached me just about as I — in fact, I think they still owed me to Los Alamos — would I consider that? And one of the first things I did after coming back to Ithaca was to make a trip to Schenectady to talk to them. It seemed interesting so I signed up.
WEINER:It was just the beginning of another stage. I started to ask about the considerations that were going on here at the same time.
BETHE:Yes, well, we were considering buying a betatron. This would have made it very easy. But then it became clear fairly soon that a betatron of 100 MeV would probably not give us any mesons. This was a somewhat vague feeling that there was something wrong with the mesons in cosmic radiation. There was not yet available the Piccioni experiment but the mesons surely did not behave the way they ought to. And so everybody had the feeling, well, if this observed meson is the real meson, then perhaps it can only produced in pairs. So we wanted to have enough energy to be sure to produce that meson in pairs.
WEINER:Was this the two-meson hypothesis?
BETHE:The two-meson hypothesis was slightly different and came just a little bit later. That was in response to the Conversi-Piccioni experiment. The two- meson hypothesis was proposed by Marshak and he should really get all the credit for it as a way out of the difficulties of that experiment.
WEINER:That was the summer of '47 at Shelter Island.
BETHE:Yes, and I think that was the first time that that hypothesis was advanced, at least to my knowledge, so we did not have that in mind. I think we might have said, well, maybe this isn't the right meson. The one we see may not be the right meson which makes nuclear interactions, and then in any case, we would need higher energy for that. But it was nothing as clear as Marshak's two-meson hypothesis. So, anyway, it did become clear to us that we wanted much more than 100 MeV, in fact, more than 200 MeV, and so that eliminated the betatron as a candidate. The 300 MeV betatron would be extremely complicated. G.E. would ask an awful lot of money for it, and by that time, we were all familiar with McMillan's idea of the synchrotron, so in the group I mentioned before we decided quite early — and surely in '46, I couldn't tell you the month in '46, but I know that it was in '46 because Bacher was involved in this decision, and he left here in January '47 to join the Atomic Energy Commission. So it was sometime in the summer or early fall of '46 that this was decided and that meant that we had to build it ourselves.
WEINER:You had to build it yourself, but was there a granting agency in mind by this time?
BETHE:Oh yes, ONR.
WEINER:Would ONR have been more likely to support it if it was done in-house that way than supplying money to pay G.E.?
BETHE:To pay G.E. that is possible. There is further evidence for that, namely, other people also got the idea of building electron synchrotrons. McMillan himself was already engaged in that. Then Purdue became interested. And in view of that, ONR had at one time exerted some pressure on us to use a synchrotron without iron, just to be different and just to make it more in-house, so to speak. But we were interested in getting a workable machine at the earliest possible time and this didn't seem to be the way. The G.E. Research Laboratory did take a contract from ONR to do just that and got it finished quite a long time after us.
WEINER:I see. Then, when you make a decision of this type and you say you don't know the mechanics so I won't really ask you about that — I would rather ask Bacher and maybe there are some documents — but it would seem that there are certain plans that go along with it, and that is, the staffing of this, the educational role of the instrument itself (since it is at a university, regardless of its semi-autonomous position, it still fits into an educational institution), were there corresponding plans made for staffing, for developing the department itself, for bringing in graduate students and for supporting them and for teaching them?
BETHE:As far as professorial staff was concerned, we got ourselves a charter, so to speak, from the president of the university, Mr. Day, to hire a certain number of people. We proceeded to do so almost entirely from Los Alamos graduates, had to so to speak. Some of them had been here at Cornell as PhD students and got their PhDs just before the war, including McDaniel and Greissen. Others had attracted our notice at Los Alamos, like Morrison and Feynman. And Corson had attracted Bacher's attention very much as a very efficient physicist, so he specifically asked Corson to join our staff. He certainly made quite a career of this here. So we took almost exclusively people we knew quite well from three years association at Los Alamos. That was as many as we could finance. It seemed enough and turned out to be enough to build the machine. And only very gradually was it expanded afterwards. The 300 MeV synchrotron was built with that staff. As far as teaching went, we had discussions, of course, with other members of the physics department and the idea was that about half the members of the department should be in the Laboratory of Nuclear Studies and the other half should not. They should participate in teaching to about equal amounts with the exception of two or three people who were not interested in research and would exclusively do teaching. But that was very amiably decided. And then the graduate students would have some courses from the people already here and some courses from the people in Rockefeller Hall, and would then choose whatever subject they wanted to do their thesis in. There was no difficulty in the early days in getting enough graduate students interested. In fact, there were probably more interested in the synchrotron than could be accommodated.
WEINER:Was there also more support for them on the synchrotron than there would have been in other areas?
BETHE:Yes, in the early days, that was true, but I think their main motive was that this was the interesting thing so that's what they wanted to work on, and this was probably the subject in which the largest number of jobs would be also available afterwards. There was, however, a larger number of research assistant positions. We had a contract from ONR which provided for research assistants, both in experiment and theory, and this was very useful.
WEINER:And they would come in as research assistants, still at the graduate level? They still would be working on their degrees?
BETHE:Yes, they would normally come in maybe in the third year of their graduate study.
WEINER:When did you start getting what other universities called research associates — post-docs who would have no real responsibility except in relating to the research — maybe you call them that here too?
BETHE:Immediately. In fact, one of my requests in the fall of '45 was that the university give me a personal research associate on university money. I had an offer from Columbia University at the time which I turned down) and one of my demands for staying was this. My first research associate was Ernest Courant, who later on went to Brookhaven and discovered the strong focusing. In fact, he worked at the time on the extraction of the electron beam from the synchrotron. It was very premature and it took us years until we experimentally even thought of that. But he thought of ways of how this could be done and the limitations on devices to do so.
WEINER:So he was the first of the personal research associates?
BETHE:Yes. Now as soon as we got the ONR contract, it immediately provided for some research associates. There were some in experiment and some in theory. For instance, De Wire, who is now the Acting Director of the Laboratory, came here as a research associate on the contract. I think he came in the fall of '46.
WEINER:But that was generally a temporary position?
BETHE:That was a temporary position. Many research associates went through these temporary positions. At times we promoted one of those to assistant professor. Two of our more successful research associates were Salpeter and Kinoshita, who then both were appointed to professorships.
WEINER:This approach to building staff and financing at Cornell in particular compares quite favorably with the problems before the war because from what I understand after the initial small cyclotron was built, there was considerable difficulty getting funds from the university for an expansion. This is one of the reasons I gather that Livingston found it more attractive elsewhere where he could be associated with a new larger cyclotron project. From what I can determine, the problem was one of general fund-raising for the university needing to be done and an unwillingness on the part of the administration to have a special campaign within that. I think I have it right...
BETHE:You have it absolutely right, and in fact, at times, we were enjoined not to wage any special campaign because this would detract from the general campaign of the university.
WEINER:But in any case it was outside funds — postwar and prewar — so it wasn't a question of how the existing budget was divided. It was a question of having a little license to hunt for funds which you were denied in the earlier period
BETHE:Right. And, of course, the great change was the entry of the government into the scene, first ONR, then AEC, then NSF and the other two services.
WEINER:In looking over your list of publications in the years since the synchrotron became operative, which is '48 I guess, would you say that the existence of this facility on the campus influenced your work, or would you have pretty much tackled the same kind of questions, relying on data from elsewhere if the machine had not been here?
BETHE:That's a very good question. For some time I think it influenced my work greatly, let's say from '48 to '50 some. At times and especially after that period I felt that I wasn't doing enough about it. I wasn't doing enough theoretical work connected with the synchrotron. Now, there are — let me go through this list — for instance, the paper on the photo capture by nuclei, that is gamma rays producing some photodisintegration — "Neutron Yield from the Nuclear Photo-effect," with Levinger, was in connection with the synchrotron work/here. Then the "Small Angle Scattering of Light by a Coulomb Field" was done specifically in collaboration with Robert Wilson who was interested in observing this on the synchrotron, so we wanted to produce a theory which he could then test. Much of the work on bremsstrahlung and pair production was motivated by the synchrotron because this was a good way to measure accurately the cross-sections for bremsstrahlung and pair production, and, at the same time, these two phenomena were important as the service calculations for the synchrotron. For instance, if you want to measure the number of quanta that came from the synchrotron the best way is to produce electron showers, and so you wanted to know accurately how these showers would work. Robert Wilson also did some shower theory work himself, so that is what connected with it. "Moliere's Theory of Multiple Scattering" also has to do with the synchrotron — a question with the detection of particles. "Bremsstrahlung at High Energies" and "Theory of Bremsstrahlung and Pair Production" and about half the papers, I think, are connected with electromagnetic radiation in connection with the synchrotron. Now, another large number of papers might have been written even without the synchrotron, namely those are the papers directly related to particle physics, to high energy physics — the meson papers. The meson theory clearly was reaping to do. The synchrotron helped in that it gave us direct access to some of the experimental information but much of this we probably would have done anyway, such as "Properties of Pi Mesons."
WEINER:When was that one?
BETHE:That was '52. "Angular Distributions of pi+ Production in n-p Collisions," also in '52. "Meson-Nucleon Scattering..." was a major paper. The senior author really was Dyson. This is '54 — Dyson, Ross, Salpeter, Schweber, etc. There we tried to develop a general theory on the scattering of mesons by nucleons. Good experiments existed, mainly due to Fermi and his school at Chicago, and now the question was to understand it theoretically. We didn't do it very well, and about a year later, Chew and Low did it extremely well and they put us out of business. But this was our contribution to this. Mesons and Fields, the book I wrote with de Hoffmann, was a response to the general interest in meson theory. The Phase Shift Analysis of Meson-Proton Scattering — that was mainly using the Chicago experiments, not our own. Still I think it made a difference that experiments were being done on a closely related subject.
WEINER:Just speculating again about this period, obviously from what you have said, a good proportion, perhaps half of the papers in this period from 1948 to the mid-fifties, were influenced by the needs here, or by opportunities presented. This is in addition to the other half which might have benefited from experimental data but which you could have gotten elsewhere, say the Rochester Conferences. Now, did that one-half that was mostly related to the work here tend to keep you out of certain other interests and fields that you would have pursued more — you had only so much time? Did you feel that you were being pulled away from something else?
BETHE:No, I didn't feel that way. I certainly like to do this kind of work, partly because this was a continuation of things I had done before, and I felt that the old work was incomplete and I ought to complete it with my collaborators. Perhaps then a combination of the old love and the interests here kept me at these questions of electrodynamics when perhaps I would have been more productive if I had concentrated entirely on meson theory, but I somewhat doubt it because what we did in meson theory, the phenomenological part I think was very useful, namely the phase shift analysis in which we established the resonance at 200 MeV pion energy, because it countered Fermi's preconceived ideas. Fermi didn't want to believe anything unless he was absolutely forced by the experiment to come to that conclusion, and, well, the experiments didn't force you. It was only a more natural explanation of what Fermi had observed and the explanation which he had given. So that, I think, was useful. The purely theoretical work was a prodigious effort and certainly it was necessary to do it, but we didn't find the solution. Other people did. And I suspect that Chew and Low would probably have found the correct solution even without us.
WEINER:Where were they working at the time?
WEINER:In this period up to the middle of '55 I guess you were also playing the being a link between role of mediator, in terms of experimental and theoretical work, just as you had in the thirties. I get the feeling from the kinds of things you were publishing that you felt a kind of responsibility, for example, the range energy.
BETHE:I did indeed.
WEINER:I had come across, in Cockcroft's papers I guess or somewhere, in the thirties, the blueprint, the informal thing that you and Livingston had done, which you then sent out a correction to and so forth. Now this was distributed to people who had a need for it throughout the world, it was not a formal publication as such, but it was like a preprint that never got printed.
WEINER:And then I think of this paper ("The Range-Energy Relation for Slow Alpha-Particles and Protons in Air") which I have a copy of — it was 1950 — and there are two interesting things about it. It is certainly bringing every- thing up to date and making some corrections, and also it apparently is the first Reviews of Modern Physics paper since the three articles in the thirties. So it is significant in that double sense. I would like to ask if I am right in my interpretation of this kind of mediating service role, and whether you were conscious about playing that role, and what led up to this 1950 version of it?
BETHE:I was very conscious of it and I think I had become even more conscious at Los Alamos where this was a very essential function to perform, to give something to the experimenters that was really useful and derived from the theory. I have felt that all the time. I felt also the obligation of keeping things somewhat organized in the scientific sense, that when people go off on tangents and do something that obviously is not very closely related to the subject, to reemphasize what is the important point in the subject. I think up to the middle of the fifties I was conscious of that role and to some extent was able to do so. Since then, I know I haven't, certainly not in particle physics.
WEINER:You haven't because it was impossible to keep up with?
BETHE:Yes, it was impossible to keep up with. I think from the time of the Chew-Low theory on, there developed a new group of experts of the next younger generation who were much more expert in handling the theory, in understanding the basic equations of particle physics than I was, and so from then on I felt myself completely outclassed by this younger group — Chew, Low, Goldberger, Gell-Mann and a lot of people of that generation. I had a sabbatic in '55-'56 and went to England. I thought for some time about what I should do and I found that I had two choices. I could either try to study very hard and try to keep up with the young people and keep up in particle theory or else I could try to find a new field. It happened that a new field offered itself, which was really an old field, namely, nuclear matter theory, and I decided for the latter, partly because I wasn't sure whether I would be strong enough even under the best of circumstances to keep up with the bright young men, and partly because I thought that this field of nuclear physics was one in which I had enough background and perhaps I could be more useful and more productive. Since that sabbatic, in the fall of '55, I have completely given up particle theory and gone back to nuclear physics.
WEINER:Would you say that the 1955 publication of your book on mesons and fields - represented what you knew to that point and it almost was a climax of that stage in your career?
WEINER:By coincidence it coincides, but apparently there is a connection as far as a wrapping-up.
BETHE:It was a wrapping-up. When I wrote this book I didn't intend it to be that. I was then quite determined to stay in that field and considered this just as a starting point, like the Reviews of Modern Physics papers had been for nuclear physics. But then I didn't feel strong enough to do so.
WEINER:Was it because of what you had to grapple with when you were trying to put the book together?
BETHE:No, the book was relatively simple, but it now became much more complicated. There came dispersion theory, which developed just in '55, '56 and so on, which was a development of the Chew-Low theory, making it relativistic and more firmly founded. And this is an awfully complicated theory. By now I think I may have understood it. This theory was further expanded by Mandelstam who then introduced double dispersion relations and so on. It seemed a science just by itself. It required a lot of formal knowledge. You had to have things really understood so well that you could work with them and without spending days each time worrying whether your formula was correct. And, at the same time, it involved a great deal of further physical insight.
WEINER:It seems to me that considering the other involvements you had at the time that the amount of time you had left for physics was probably less than ever before and it would make the problem of getting abreast of this new field even more difficult.
BETHE:Exactly, that was exactly it. Now I didn't know in '54 how much involved I would be but the most serious involvement started in the fall of '56 when I came back from my sabbatic and became a member of PSAC, the President's Science Advisory Committee. In view of that, it was absolutely necessary to have made the decision which I had made.
WEINER:Did the new environment, returning to Cambridge — I guess you had been there in '32 — and getting away from this whole very rapid postwar development here, did this help you make the decision? Was there something about that experience that gave you perspective about the American scene, about physics, about your place in it?
BETHE:No, I don't think so. It was only that I had much more time for that year so I really had time to dig into something new, and the something new was the nuclear matter theory. And I'm very glad I did that.
WEINER:A lot of people are. Was Goldstone there because he came with you?
BETHE:He was just a graduate student there. There was Mott, the Cavendish professor, who suggested to Goldstone to work with me. I very soon had a very fruitful collaboration with him and he turned out to be extremely bright, did some things which I couldn't have done, and worked with me on another thing which I could have done but which it was much better to do with him. So it was very fortunate to have this extremely bright graduate student. I don't think I had had such a bright one for a couple of years or several years here at Cornell. Then there also was Thouless who only started his work with me in Cambridge and then came back with me here to Cornell, took his Ph.D. here and now is Professor in Birmingham. He is a very intelligent man and on the formal side, perhaps one of the two greatest experts in nuclear matter theory, in many body theory.
WEINER:Who is the other?
BETHE:Brandow. He will come later.
WEINER:So this was not so much a change of perspective but rather a chance to have the time to assess what was going on in your mind anyway, and then the opportunity, because the subject matter presented itself, students were there, and you had the time.
BETHE:Yes. I had been intrigued by Brueckner's papers before. I hadn't really understood them. My first task was to understand them and that is what I decided I would try to do.
WEINER:Let me backtrack now to the other involvement in addition to physics. We talked of the departmental involvement, and naturally that would take a good deal of your time because of the meetings that one would have on this whole new development.
BETHE:Not as much as you might think. It did take a good deal in the first year. It always takes some time. There was one difficulty in that the chairman of the department and the director of the Laboratory of Nuclear Studies didn't always see eye-to-eye with each other, and I had to mediate in that respect. But you were....
WEINER:The other part of it was that this was a period of involvement too with consulting. You mentioned the G.E. experience and I'd like to know what else followed from that, and then the whole business of government work again, with Los Alamos once again.
BETHE:While my G.E. work was fairly absorbing, as far as I remember I spent something like 40 working days at G.E. each year, which is a fair fraction. Except for the summer of '46, I went every summer for some time to Los Alamos, usually two weeks, sometimes four weeks. This, of course, was work for the government but it wasn't directly with the government. I was not very much involved in that period with direct government committees. I was occasionally — I think there only was one session of some committee which had to do with production of fissionable material for weapons, and I have only the vaguest memory of it except that Mr. Greenawalt of DuPont was the chairman of the committee. That must have been back in '47 or so. Then I got involved in '51 or so with a committee — my memory is very bad on this — to advise the Defense Dept on the production of atomic weapons and the use of atomic weapons. I think it was called the CAE (the committee on atomic energy). Its chairman for many years had been Oppenheimer. When I joined the committee, Oppenheimer was no longer on it. In fact, I was, I think, his replacement. But this happened long before Oppenheimer fell into disgrace. I seem to remember something like '51 when I got on this.
WEINER:This was quite different from the various AEC advisory committees?
BETHE:Yes, quite different. It advised the armed forces — I think it had some relation to the Military Liaison Committee of the Department of Defense. There is one Assistant Secretary or a man of the rank of Assistant Secretary but who isn't an Assistant Secretary who is in charge of atomic energy, who was General Loper at that time. The committee involved some generals from each of the three services and then it involved an equal number of civilians. The chairman at the time was Bacher, and the executive secretary or director was Dave Beckler who is now the executive secretary of PSAC of the Office of Science and Technology. We discussed all sorts of things about atomic energy including the nuclear plane and I don't know what all else.
WEINER:How did you find that role? Was it different than the industrial role?
WEINER:Was it similar to Los Alamos? By Los Alamos, I mean to your wartime experiences there.
BETHE:No, I wouldn't say so. It might have been. During the war, I was, of course, in the administration of Los Alamos, but that was much more a pragmatic administration where we decided what we should do next. This committee was much more a question of mediation between divergent interests, and it was in fact largely mediation between the three services who didn't get along with each other at all. The civilian members very often had to fulfill that function. Another role was to eliminate programs which seemed not to make much sense but would cost a lot of money. We didn't manage to eliminate the nuclear plane although we would have dearly loved to. But there were quite a number of such programs which this committee could express an opinion on and somehow we managed, I think in most cases, to express what seemed to me the right opinion. I don't know how we did it because it was a quite unwieldy committee.
WEINER:How often did you meet?
BETHE:About three times a year, I would think.
WEINER:But this was after some preparation. Would you have been sent materials to think about?
BETHE:Not terribly much. It was a two-day meeting each time. I was somewhat informed by means of the Los Alamos connection, and when the H-bomb development started, this was part of the discussion, and that committee wanted to be briefed, mostly by me, on the Los Alamos developments. I either got on in '51 or '52, certainly not earlier, and I am sure I was on by '52 because in '52 there was a meeting of that committee in Los Alamos while I spent half a year in Los Alamos.
WEINER:So your involvement in the committee began after the H-bomb work was in progress? It wasn't in a formative stage and the committee had nothing to say in advice beforehand or anything like that?
BETHE:I do not know. I wasn't on it. I certainly was not on it before Teller's invention in the spring of '51, and I was on it by the spring of '52. That's as much as I remember, so I don't know what the committee did in the formative stage.
WEINER:Was this your first postwar government committee, other than working at Los Alamos?
BETHE:Direct government committee, it probably was the first one.
WEINER:So that the well known discussions about whether to build an H-bomb which had taken place in the late forties, the involvement that you had in discussions that are known with Oppenheimer and Teller and so forth, was this strictly private or was it through Los Alamos?
WEINER:Are these issues that would have come up though, at Los Alamos?
BETHE:They would, but they didn't come up while I was there. If I may go back to that period of '49, I was on my regular consultations for Los Alamos in the summer of '49, probably spending there two weeks or maybe three weeks. At that time there was some discussions whether one should go on to Super, as it was then called, and I think I expressed myself opposed to it. I don't remember whether it was in the summer of '49 that I proposed that one should go for a very large fission bomb. It seemed possible at the time to design a fission bomb of half a megaton, and I know that I' proposed that. And I know also that Los Alamos carried it out. In fact, it was tested in the spring of '51. Whether I proposed it in '49 or '50, I don't remember, and that is of some interest in this connection, but I just don't remember.
WEINER:So in these discussions then, your response to the thought of a possible Super was negative at that time?
WEINER:But then when people like Teller were active proponents of it, you were asked again apparently?
BETHE:Yes, then I was asked. I heard about the Russian explosion. That was in August of '49, and I wondered just what one should do about it. And somewhat later Teller came to visit me. I think this has been often reported and you probably have that record.
WEINER:You might as well make it consistent with the rest of your story.
BETHE:He came here to ask me to support the project and to go to Los Alamos to more or less lead the theoretical effort. I had very great misgivings, mainly on the question of whether it was desirable to have another escalation. We had a very extensive discussion on this in our living room, which I remember very vividly. My wife was present also, strongly opposing involvement in a further escalation. But I agreed to think it over. And then in that discussion a red herring was dragged across incidentally, namely, this was not at all important in making my decision but incidentally I told Teller that I didn't want to lose any money if I went to Los Alamos. This would require a higher salary than Los Alamos was normally willing to give. And that this was a condition but this was not the decisive point. Well, that afterwards was blown up by Teller and especially by Strauss into being my main condition which it was not at all. So then I stewed about this problem and was essentially undecided. It must have been October that all this happened. Before all this happened I had written to Hafstad who was the director of reactor development AEC, offering that I might devote more time to reactor development if that was considered useful in the present context. So for the week after Teller's visit I just thought about the problem and was entirely undecided. At the end of that week there was a meeting of the Emergency Committee of Atomic Scientists in Princeton. That committee was under the direction of Einstein and probably some time we should talk about that one.
WEINER:Yes, I'd like to. I talked with Marshak about the relations of FAS and that group at the same time. It was very interesting.
BETHE:Yes. So I went to Princeton and Teller went to Princeton at the same time, I think independently. At the meeting of the Emergency Committee Szilard greeted me, saying, "Ah, here is Dr. Bethe from Los Alamos," which I denied. During that meeting, two things happened. One was very much written up — the discussion between Teller, Oppenheimer and myself in Oppenheimer's office in which Teller presented his case and Oppenheimer did not argue against it. I think Teller has presented this as Oppenheimer arguing against it — he did not. But he tried to present some arguments. He mentioned the arguments of other people, in particular, of Conant, who said, "under no circumstances will I vote for the H-bomb." And he read to us a letter from Conant. But he, Oppenheimer, did not take any stand on it, one way or the other. I remember that Oppenheimer and Teller were discussing the arms race which would ensue between Russia and the Unites States and Oppenheimer said, "Well, it's a race between a piece of glass and a piece of onyx — totally transparent and totally obscure." And I think they even discussed semi-facetiously whether one should develop it together with the Russians. I said very little at that conversation. I listened to the two people talk. It didn't help me make up my mind one way or the other, but when we came out Teller said to me which he has often quoted, "Now you will not join the H-bomb project." But that was not so. Certainly that meeting had very little influence on me. What did have a tremendous influence on me was the following evening a very long discussion with Victor Weisskopf, walking around the Princeton campus, in which he discussed very vividly the meaning of a thermonuclear war. That influenced me greatly, and I think decisively, because the next morning I had decided not to go.
WEINER:How long was that discussion with Teller and Oppenheimer?
BETHE:About an hour.
WEINER:Was Teller at the meeting as a participant or had he come to see you?
BETHE:Teller had come to persuade Oppenheimer and it happened that it was the same time as I was there and so he thought it would be useful to do it jointly.
WEINER:Were you able to communicate your decision the next morning to Teller? Was he still there?
BETHE:Yes. Well, I had to catch Teller in New York. He was visiting Strauss in New York and I got him there and told him.
WEINER:Did he try to talk you into it?
BETHE:At that time, not very much anymore. He was very sad. He felt he was very disappointed. He said at that time, "I knew it after the meeting with Oppenheimer." And I tried to tell him that he didn't know it because I didn't know it. But that was the story. One more point. After that meeting with Weisskopf, I drove with both Weisskopf and Placzek to the LaGuardia Airport because I was to go to Oak Ridge for some business. We missed the plane, but Placzek was very much of Weisskopf's opinion and his advice which I valued very greatly also, was important to me to say no. At that time we speculated what Oppenheimer's feelings might be, and I told the other two that I didn't have much idea after that hour-long meeting. Oppenheimer, of course, was the chairman of the G.A.C. and we speculated just what the G.A.C. was likely to do.
WEINER:What was the result of your speculations, do you recall?
BETHE:That we didn't know, that we knew that Conant would vote against it, that we thought possibly Rabi might vote against it, and that was about as far as....
WEINER:How about Fermi?
BETHE:We had no idea.
WEINER:Maybe we should conclude by reminding ourselves what we want to talk about next time. I think we should take this story through to its conclusion of the subsequent developments and your subsequent involvement, and, along the way, talk about the Emergency Committee, the meeting at Princeton, and the other activities of that type, beyond the things discussed in Alice Smith's book which covers it briefly.
BETHE:And I should perhaps discuss a little more the G.E. involvement. There isn't terribly much to be said about the Los Alamos involvement.
WEINER:It's filling in then these elements in the period up to, say, '55.
WEINER:Here we are again. Today is the 9th of May. We are sitting in Professor Bethe's office and it's about 11:30. And we agreed when we left off yesterday afternoon to finish the story that you had started to tell which were the discussions about '49 or so with Teller and Oppenheimer, about the consequences of those discussions, what did happen, then to fill in on the background of other work similar to the public efforts at the time of the May-Johnson Bill, things that were not covered in Alice Smith's book (whatever that might be), and then as you pointed out, the rest of the G.E. involvement, and then you said that there was not much to say on Los Alamos, but whatever there was there — filling in sort of up until this period of 1955 which represented a change of your research interests.
BETHE:OK. About the H-bomb debate, I have talked about my decision not to join the H-bomb project. The next event I remember is the meeting of the General Advisory Committee. I was not a member of the General Advisory Committee to the AEC, but I was asked to testify to that committee. I remember, in the anteroom to the hearings of that committee, I met Robert Serber and George Kennan. George Kennan was, I think, testifying generally about the political problems of Russia and Robert Serber about some of the technical matters. I was asked mainly about the technical problems of making an H-bomb, and I don't remember in much detail what I said. I think I probably said that there were difficulties and particularly there was this problem of how to initiate the H-bomb if one had a fission bomb to start with. But I have only vague recollections of that testimony. Perhaps it was written up, perhaps not. My main concern was just what the GAC would decide. This became known after a while. I had occasion to go to Washington at one later time and to talk to some of the members of the AEC, in particular, Dr. Smyth, and I tried to urge the decision of the commission against the development of the H-bomb. I remember at that time also, Lewis Strauss called me into his office and told me that he would pay whatever difference in salary there might exist and I tried to explain to him that this was really no solution to my problem, but it was impossible to communicate with him. He just was not interested.
WEINER:In your reasons for not going.
BETHE:In my reasons for not going. The opinion of the General Advisory Committee became more or less known, but then in January came the decision of President Truman to go ahead with the development of the H-bomb. I was terribly shocked by that and tried to do something to change the direction, which was of course very difficult by that time. We got together a group of physicists at the meeting of the American Physical Society which happened to take place in New York just at the time of the announcement of Truman's decision. We had a press conference on this and made a statement which, I think, is sufficiently public. The press conference did not go terribly well. It also didn't go terribly badly. But at the same time it became known that Klaus Fuchs had betrayed the secrets of atomic weapons development to the Russians. This, I understand, was one of the reasons why Truman decided to go ahead with the H-bomb development and it certainly overshadowed in the newspapers all effects that our press statement might have had. After that, some of us decided to write some articles, some of us not directly connected with the decision, some articles which the Scientific American agreed to publish and was eager to publish. I wrote an article which was partly technical. It contained some technical statements which I considered quite innocent but which the AEC did not so consider, and so, having been sent an advance copy of the article, the AEC decided to stop publication. The AEC then eliminated some of the technical statements. I don't remember very well what they were concerned with. Anyway, they were made obsolete by the further H-bomb development but that wasn't known at the time, and the article was then published with these parts eliminated.
WEINER:When you say stopped, did they represent themselves directly to the publisher?
BETHE:Directly to the publisher.
WEINER:Was it a request or an official act?
BETHE:I think it was an official order. I don't think they got a court order but they said they were prepared to get a court order. However, Mr. Piel decided on his own to obey the AEC order, so the already set plates were destroyed and new plates made with the objectionable parts eliminated.
WEINER:Did that delay the publication?
BETHE:It delayed it by a few days.
WEINER:In other words it still made that scheduled issue so the timeliness of the article was still...
BETHE:Oh yes, there was no question about that. I think it was a considerable loss for the Scientific American. But on the other hand they got some advertising out of it. Then there was another article by Bacher about the same issue, looking at it more from the general strategic point of view and making the argument that it was rather unnecessary from the standpoint of our military preparedness because we had such great superiority in normal A-bombs and, in addition, had the possibility of making much larger atomic bombs than we already had and this was really sufficient for a very long time to come. And a third article by Ridenouer whose contents I don't remember in detail. Following that, there came the summer of 1950. I went to Los Alamos with the intention not to work on the H-bomb but only on fission weapons. However, at that time, Ulam was doing some calculations with his assistant Everett which seemed to show that the H-bomb, as conceived previously during the Second World War, would not work at all. And this gave me new hope and I was quite interested in the idea of further proof that it wouldn't work. was willing to work on that.
WEINER:The negative H-bomb.
BETHE:Yes, the negative H-bomb. At the same time the Korean War broke out and I was quite impressed and disturbed by that and was more than willing to do more for Los Alamos generally because I considered this a case of direct aggression. I was very much worried that the Russians might attack in Europe at the same time, which they did not do. But my general willingness to cooperate with the Weapon Development was much increased by the Korean War. As a consequence of all that, I got one of my best graduate students to work with me on the proposition of showing in more detail why the H-bomb would not work, and do some of that work here at Ithaca. And we did indeed make some progress in that direction.
WEINER:Who was the student?
BETHE:George Bell. He subsequently went to Los Alamos and has been at Los Alamos all the time. His greatest claim to fame is that he is one of the greatest mountain climbers of the United States. He was on the American K-2 expedition and later on one of the expeditions which climbed Laotse, next to Everest. He is a very remarkable man. In the meantime, his interest has shifted to biological problems, and I believe he does quite interesting things at Los Alamos on theoretical biology.
WEINER:He worked with you here. When would that have been? Was it a summer project?
BETHE:This was in the fall of '50. I had spent two weeks or so at Los Alamos. Now I visited Los Alamos again in January of '51. I had extensive discussions still arguing against the H-bomb at Los Alamos. I found that some of the Los Alamos people themselves were quite sympathetic to that point of view, but that, on the other hand, there was a big project under Teller and Wheeler in trying to go ahead. Teller was in a foul mood because the evidence was accumulating that the H-bomb would not work. The first test was impending in which some minor device, possibly related to initiating an H-bomb, was being tested. That took place Later in the spring and was the so-called Greenhouse Test. In that greenhouse test there was also tested my proposal of a half megaton fission bomb. Subsequently in the spring, first Ulam made a certain invention and then Teller exploited that invention for a completely new design for the H-bomb, which I believe was formulated some time in April '51. Around that time I was told about this and I am not quite sure just how I learned about it. I think somebody came from Los Alamos and I don't remember who it was. It was rather clear that this would work and, in fact, that this was so clearly feasible that the strong danger existed that the Russians could do it too and could do it independently, so that it was now necessary to really go ahead. So upon this complete change of design I had to change my mind and had to agree that this ought to be done. This would work. And if it was to be done, we would better do it quickly and well.
WEINER:Did that change of view take place immediately upon learning this new information?
BETHE:Immediately upon learning the technical details about the new invention. I am not sure whether it still took place while I was here, but it certainly took place in the two weeks which I spent in Los Alamos in early June of that year. So I was quite convinced of this by the time we got together for our meeting at Princeton, which has been much written up, in which the General Advisory Committee got together, and I was sufficiently convinced that I agreed to give one of the talks explaining the technical details of this. The General Advisory Committee and the AEC endorsed the new design at the Princeton meeting without any reluctance that I could see.
WEINER:Which would include Oppenheimer as well?
BETHE:Yes, particularly Oppenheimer. Oppenheimer was almost immediately convinced that this would work and had to be done. There was nevertheless tremendous conflict between Teller and the rest of the Los Alamos Laboratory which was continuing. This conflict was mainly about the way it should be done, namely, the Laboratory was convinced that one should do the best possible calculations, then the best possible design, bringing in people who were experts in engineering rather than theoretical physicists to lead the actual design and manufacture of this very complicated device. Teller thought instead that one should have a dozen different random tests before getting to the final design. The Laboratory would not have that because it would have meant ten times as much work for the people in the Laboratory. I think this is essentially the end of the story as far as I am concerned. I agreed then to come to Los Alamos for a prolonged time, from February through July of 1952 — maybe even August — and to participate in the calculations and the design of the weapon. Even then, I was always happy when there was some indication that it might not work, which happened occasionally, but it was a forlorn hope and I eventually worked with the group in trying to bring it about.
WEINER:Did you try to bring others into the work? Was there a need for that?
BETHE:The one student had joined by that time. I did not try to bring anybody else, and I think it was really in good hands by that time, as the success shows, because in November of '52 it was ready to be tested.
WEINER:When were the tests?
BETHE:Early November '52. There was some attempt in which I participated to postpone the test, and first of all, let the new President Eisenhower, participate in the decision. And second, perhaps making another effort to say, all right, we have a device ready to be tested and let's try once more to come to an agreement with the Russians not to go ahead. I forgot who the main moving force was. I believe it may have been Bush who was in the foreground of this effort.
WEINER:Of the postponement of the test to see if that could be used for reconciliation?
WEINER:Was this made strictly privately?
BETHE:Strictly privately. In fact, it had to be private because it was, of course, secret already, and I made it in a private letter to Mr. Gordon Dean, who was the Chairman of the Atomic Energy Commission.
WEINER:But in this period after the Scientific American article, you had no further public statements on this?
BETHE:No further public statement.
WEINER:Was there any public movement developing on this issue?
BETHE:No, not that I know of. I think lots of people were cheered by the Scientific American articles, but it didn't develop into any public movement.
WEINER:This wasn't something that the FAS took up as a specific issue, whether to build or not to build an H-bomb?
BETHE:I don't remember.
WEINER:But it does occur to me that that was the time when Niels Bohr's open letter to the UN finally saw the light of day after many drafts in 1950. Do you recall any impact of that, any discussion of that?
BETHE:No, I don't.
WEINER:That is probably universally true. There was very little discussion.
BETHE:That was the letter on the open world?
WEINER:Yes, where in general terms, he suggested the world share in technological and technical information, and it was just before the Korean War.
BETHE:I was so absorbed by the H-bomb debate and the anxiety that it might really be possible to do it that I paid little attention to anything else.
WEINER:This was done in a private expert role: You had been asked and involved at certain levels and you were very much the inside adviser on this, and you were also involved....
BETHE:Yes, well, at the time of the decision I was not on the inside in a way but afterwards.
WEINER:But you were already involved at Los Alamos?
WEINER:I have a question to ask about the atmosphere of working in Los Alamos as compared to the atmosphere earlier. You had worked in the intervening years, I guess, on rather a regular schedule and it was not any crash thing, but here when the H-bomb work started it was again a crash program.
BETHE:As soon as the Teller invention was made and accepted, the spirit in Los Alamos changed completely as far as I could observe. I think it wasn't just me. Before that there was strong antagonism between proponents and opponents, and even among the proponents, some didn't like the way Teller operated. By now, there was again a spirit somewhat similar to the World War spirit of having a definite job, of the importance of getting the job done, and everybody cooperated very eagerly and really with all his effort. It was a great time at Los Alamos in terms of the spirit.
WEINER:By that time there was an important difference. Many of these people had a permanent commitment there, many of them were on the staff, and then there were outsiders who had come in just for this. Were you very much in the minority, in terms of the outside visiting expert?
BETHE:There were very few. Wheeler was there early and had brought two of his associates, Toll and Ford. They had done the majority of the work for the greenhouse test, but then Wheeler decided he wanted to have his own project at Princeton, which was called Project Matterhorn. He assembled there a considerable number of physicists. As far as I remember, the. Los Alamos group didn't consider the Princeton work as quite up to standard and there was a slight amount of friction in this respect. So Wheeler was no longer there and came only for visits. Teller had left in a huff. So of outsiders, there were very few in the theoretical division. There were lots of outsiders in the engineering project, first of all, Holloway, the director of the project and manager of the project who did this extremely well. They then brought in a big team of engineers from American Car and Foundry who worked, I think, very effectively on the engineering. Some of them stayed afterwards on the Los Alamos staff. But outside the engineering group, there were not many outsiders.
WEINER:So the involvement took you to the successful testing. Were you involved
BETHE:After the crash period, well, I left again for the fall term here at Cornell. I kept in contact. I heard about the test almost immediately. But after that, I went back to my regular summer schedule and didn't go for a prolonged period.
WEINER:I think that brings that part to a logical conclusion except there was an aftermath when all of this came up again with the Oppenheimer hearings in 1954. Is this the logical time to continue that and then we can fill in more about your own activities?
WEINER:Well, you completed your part of the work on it.
BETHE:Yes, I kept in contact with the work, and in the future I looked at the minor design changes that people had made from liquid deuterium, which was the '52 device, to lithium deuteride which was the active material in all future devices. I looked at the calculations, whether this would work, and so on. But I didn't play a very fundamental role in any of these. These tests were then carried out in '54. In 1953, I should now mention, there was in August a Russian test, in fact, the first Russian test of an alleged hydrogen bomb. When, shortly after this test, I went to Los Alamos, I found everybody very busy analyzing the radioactive debris which had been collected from that test. There now came the very interesting puzzle just what had they done. Fermi got a little involved in this and I got very deeply involved in it, as did several other people. We concluded that it wasn't that it had hydrogen reactions in it, and that it was not an H-bomb of the type that we had developed. In fact, the Russians never again used that design. It seems to me in retrospect, and, in fact, we came to that conclusion very soon that very likely this was only a demonstration to tell us, "we can do it too." But the genuine article they didn't get until 1955. Through this analysis I got involved in another government committee on which I have stayed ever since, namely a joint Air Force and AEC committee to evaluate the foreign tests and make reconstructions of the devices that the Russians, and later on, other countries, might have tested. This has been very interesting work, especially in the early days, and I think it has been quite useful work. In the course of time we taught the people themselves to evaluate it — that is, the people who actually collect the debris — and they are now very expert at it and we are hardly necessary any more, but I have stayed with it ever since.
WEINER:That led up to some interesting involvements in '58 with the test ban thing.
WEINER:This involvement from the start in '54 would mean going to Washington. How much of the work then did you do here, and did it involve others with it?
BETHE:I didn't do much work here on this. Occasionally some of the Washington people would come to visit me and discuss matters with me, but mostly it involved going to Washington. And as far as the technical work was concerned I did that at Los Alamos during my visits there.
WEINER:Did you still keep on with your summer visits?
BETHE:I kept on with summer visits. I have been in Los Alamos every summer except for '46. And for some time, a good fraction of my work there was on the analysis of foreign tests. Some of the Los Alamos people got very interested. in that, including George Bell again, and they kept up their interest in it. There are also some radio-chemists there involved in the analysis. But I did very little of it here in Ithaca.
WEINER:The decision that was taken about building the H-bomb was carried out, but then there were the repercussions that occurred with the Oppenheimer hearings later. Maybe you should recount how you first became aware that anything was brewing, whether there were any indications or observations you saw in Oppenheimer's role or people's response to him that would make one think that something like that was going to occur.
BETHE:The only previous indication I was aware of was a very nasty article in Fortune which may have been '52 or '53 by a man by the name of Murphy, which charged Oppenheimer essentially with a conspiracy with other members being Rabi, Zacharias and Charles Lauritsen —the conspiracy being to weaken the American defense effort. What they had done in fact was to have a number of summer studies, which were partly initiated by these people but involved dozens of other people, summer studies of the role of strategic and tactical air power in the eventuality of a war —the most famous of these studies being the Vista project at Caltech I forget which year, in which they tried to emphasize that it might be more useful to use tactical nuclear weapons to prevent a Russian invasion of Western Europe than to use strategic weapons. This was very much disliked by SAC, the Strategic Air Command. I knew that Oppenheimer had enemies in those quarters, but I think the only indication I really had was that article. Then I got to know about the trouble, possibly first by reading the New York Times. As you will remember, he was given the choice of quietly resigning or of defending himself against these accusations. He decided to defend himself and published the AEC letter and his own response in the New York Times. It is possible that this was the first thing I knew about it. Soon afterwards, and I think this was in December of '53, there was one of the Rochester Conferences —that may have been in February — in which I saw Oppenheimer. I think one of the things I did was to ask him what I could do for him, and he asked whether I would appear as a witness, which I was very glad to agree to. I believe another thing that happened which was somewhat incidental was that Oppenheimer had been slated to give the after-dinner speech at the Conference and felt that he should not do so and asked me to take his place which I did. While Oppy was extremely calm in the face of this, he said already at that time, "it is impossible for the AEC to find me innocent. After what has happened, they just have to convict me. But nevertheless I have to go through with it." There was discussion, I think, with quite a number of people who were trying to help Oppenheimer in this during the Rochester Conference. Then, later on, came the hearings which of course are published. I think what I said was reasonable during the hearings. I had a run-in with the prosecutor, who tried to embarrass me with the fact that Klaus Fuchs had been in my division at Los Alamos. But I think in the end this worked really against him rather than for him that I didn't realize that at the time. Very shortly after — or perhaps before — there was the Washington meeting of the American Physical Society. I happened to be President of the Physical Society at the time and invited Oppenheimer to sit at the speakers' table but not to speak. When I introduced him he got a standing ovation by the Physical Society. There was very strong feeling. I did not know until much much later about the Chevalier affair, and I thought the whole problem was about his role in the H-bomb and in the strategic air force problems. I tried at one time to persuade Edward Teller to testify for Oppenheimer, which of course he would not do. Then at the Washington meeting I talked with Teller for a long time in the evening. In fact, both my wife and I talked to him, and it was a desperate discussion in which he brought all sorts of irrelevant things which we tried to argue against, but he was absolutely set in his opinion.
BETHE:That Oppenheimer must be eliminated from the advisory role in the government. He said that Oppenheimer's actions had always been obscure to him — to Teller — and he could never explain why he acted one way or the other, and he would like the policy of the advisers to be more transparent.
WEINER:This was his public position.
BETHE:This was his public position. So this was a hopeless matter. I tried to give advice to one of the counsels for the defense of what questions to ask Teller. The questions were never asked: at least they are not in the transcript. And I tried in my testimony to make clear the antagonism between Teller and Oppenheimer dating back to the Los Alamos time, and the non-cooperation which Teller had shown at Los Alamos, which I still think is a relevant point in the case. That was my personal involvement.
WEINER:Was it known in the larger physics community who had testified and who had taken what position at the time?
BETHE:I think it was known partly. It was known certainly that Rabi and I had testified for Oppy and Charles Lauritsen and there were others. It was known that Teller and Alvarez had testified against him. It was not known for each individual — not every witness was known.
WEINER:Was there any feeling of support or of hostility expressed, for example, against Alvarez and Teller?
BETHE:I think so. I think people generally supported Oppenheimer very strongly and therefore felt some hostility at that time — far more afterwards when the testimony became known. And as you know, some of the physicists refused to shake hands with Teller afterwards.
WEINER:What about the APS? Wasn't there a public statement made?
BETHE:There was a public statement. When the verdict became known, the APS and I think this was the verdict of the Gray hearing board, the APS Council made a statement and I think the council had already discussed that during the Washington meeting. I guess it was just the officers of the APS and not the whole council. I essentially wrote the statement and I even got some trouble because it had to be done very quickly, I checked only once with the vice-president who was Mr. Birge of Berkeley and he, I think, approved the general idea and the rough statement I had written, but was then very disturbed that I didn't check the final statement.
WEINER:Was it just because you hadn't checked it or because he disagreed with it?
BETHE:Mainly because I hadn't checked it.
WEINER:He is very thorough and tends to detail a great deal — a personal characteristic. So that was during your presidency. How did it come up at the council? You said the statement was from the officers. Was it a point on the agenda? If so, who introduced it?
BETHE:It was. I don't remember the details and I don't even remember to what extent it was discussed. There are no minutes of the meeting as far as I know.
WEINER:We have in the archives the minutes of the council but I have the feeling they are very formal and only record actions taken. Did you see any change in Oppenheimer's attitude toward this during this whole period, because the last Comment you made was that before the hearing started he was convinced that he had to lose but nevertheless, in a fatalistic way, that he had to go through with it. Did you have any other opportunities to either observe or to discuss it with him?
BETHE:I saw him not terribly long afterwards, but I don't remember just how long afterwards, and he was just terribly sad and very beaten down. In my opinion, he really lost his spirit as a consequence of that. He was never the same person again. I saw him quite often afterwards but I don't remember how soon afterwards.
WEINER:Do you recall the play, In the Matter of Robert Oppenheimer?
WEINER:Just from my curiosity, how do you feel it was in terms of the representation of your own role, the characterization of you as an individual?
BETHE:I think it was quite good.
WEINER:You felt there were no major distortions, that it was pretty accurate?
BETHE:It was quite accurate and, in fact, it quoted the more important parts of my testimony.
WEINER:Did they consult with you at all?
BETHE:Not at all.
WEINER:When did you see it?
BETHE:I didn't ever see it. I read it in German and then I read, at least that scene, in English and in French, but only that particular scene that has me in it. In fact, the French version is the best. I have never seen myself on the stage, but my wife has.
WEINER:What was her response?
BETHE:She thought that the actor wasn't very much like me, but that the things he said were all right.
WEINER:This brings us to about '54, but let's backtrack to other kinds of public involvements. We mentioned earlier the Emergency Committee of Atomic Scientists. From what I know, this was a committee with Einstein as a major figure in it which was a smaller group of quite distinguished names, not a large membership group such as the Federation of Atomic Scientists or American Scientists, as it became. It would be interesting to talk about your relative positions in regard to both of them and your involvement in either of them.
BETHE:With the Federation I was in the founding meeting which took place, I think, in November '45 in Washington. This has been proceeded by local groups at Los Alamos, at Chicago and one or two other places. At the founding meeting the main point was that we wanted to have a Federation, that it was important to pursue the political aims of civilian control and international control. There were a few members of the small group in Washington who wanted other things in addition. For instance, some wanted to have also an economic union, and this was also strongly advocated by some of the Los Alamos people. I was very much against this because I thought this would detract from our effectiveness, and also it seemed to me that after the war it was very likely that we didn't need a trade union but there would be ample employment and good employment for physicists. So a trade union was quite unnecessary. One of the advocates of the trade union type wanted to call it the American Federation of Scientists like the American Federation of Labor, and the majority, including me, strongly opposed that and wanted to have a name very obviously different from that. At the same time I was in Washington actually to testify at the McMahon Committee setting up the atomic energy act. I testified to the Committee largely in closed session about the possibility of an H-bomb. That's what Condon and Szilard wanted me to testify on, so that was what I did. At the same time, there was also the initial discussion of the publication, One World or None, in which Fred Seitz and I wrote an article about the time it would take the Russians to get an atomic weapon. We said five years. It was four years, and as Szilard afterwards said, "Well, the one year you can ascribe to Klaus Fuchs."
WEINER:Who issued that publication? Was it the Federation?
BETHE:No, it was independent. It was not Los Alamos. I don't know who published it.
WEINER:Was Marshak involved in this? There is another book which perhaps he was involved with.
BETHE:No, I don't think Marshak was involved. The name that comes to mind is Masters, I think he was the editor but I am not sure. He afterwards wrote about similar problems. I don't know who actually published it. More likely Chicago than Los Alamos, but I am not sure even about that. At the same time lots of laymen's organizations sprang up in various places which were concerned with giving speeches about international control and civilian control. The most important one was at St. Louis. Its successor still exists.
WEINER:The Scientists Institute for Public Information.
BETHE:Right. That organization, as well as several others, had great difficulties with money, and wanted to have a major campaign which involved large amounts of money. So Szilard had the idea that one ought to have a separate organization to collect money and that this separate organization ought to have distinguished scientists on it, so he persuaded Einstein to head that organization, and that was the Emergency Committee. So its first function was to collect money for the activities of other organizations, which was to include the Bulletin of the Atomic Scientists. Quite a bit of that money, I think, went to financing the Bulletin but the majority went to the laymen's organizations. And then the Emergency Committee thought that it might issue some substantive statements which it did from time to time. I don't think the Committee was very good in its substantive statements. They were either very vague or they were very utopian. Einstein was a sweet old man who had a lovely way of putting things extremely simply and by his personality and the simplicity of his statements he impressed a great number of the public and made them give substantial amounts of money, like $5,000 in one piece. But he did not see the problems of the situation at all and the statements which were made were, I think, not very realistic. I was never happy with that organization.
WEINER:Were you a part of it?
BETHE:I was a member of it, but mostly, I was a negative member, trying to restrain Szilard from making extravagant statements. Szilard was the real person running the Committee. Urey was the vice-chairman who also had something to do with the policy of the Committee and had a lot more realism than Einstein. But as time went on, the statements became more and more unrealistic, and I had more and more objections. Finally more members had objections and the organization quietly dissolved.
WEINER:Were the objections on the basis of the assessment of the possibilities of conciliation with the Russians?
WEINER:So it was a question of almost a political position being taken. It wasn't a question of a technical division.
BETHE:That's right. Conciliation with the Russians was the real problem.
WEINER:And you felt that the Committee itself was perhaps too naive in its hopes
BETHE:Exactly. We had a very efficient executive secretary, Mr. Schaffner of Hart, Schaffner and Marks. He was very efficient and I think, as far as the mechanics of running it was concerned, the Committee functioned fabulously. But it didn't make much sense. The Federation made a great deal more sense, and the Bulletin made still more sense. And for some time I was fairly active in the Federation. We had a chapter here at Cornell, of which I was one of the officers. And I think for several years I did a fair amount of work for the Federation.
WEINER:You had Bob Wilson who was President at one time. And then Phil Morrison was involved in these things as well.
BETHE: Indeed, and De Wire. And then we were in close contact with Marshak who was another very active member. I was never as active as Wilson or Marshak. At one time I was to become President and had been elected Vice-President, but at that time, I think it was just when I was made a member of PSAC and I decided this could not be reconciled, so I resigned my office.
WEINER:Talking about reconciling leads to a question — one role, as a scientist, is taking the expert knowledge into the area of public discussion to make a recommendation in terms of what you think is possible and necessary and desirable, not only on the basis of technical knowledge, but of political realities as you see them, and the other is being involved on the inside of the weapons development on issues which could not be discussed publicly but were secret. Did you feel a conflict or restraint or any kinds of difficulties in performing either of those roles because they were both simultaneous?
BETHE:Not really. In my public appearances, some talks which I gave in late '45 and '46, for international control, the only handicap was that I was restricted in the amount of things I could tell, but then I had the Smyth Report as a guide which made it fairly easy. I did not find any conflict of conscience in this. At the time, I considered the political activity for public information as the most important activity, more important than continuing with any defense effort. In fact, I rejoined the Los Alamos Laboratory as a consultant only in 1947, so in 1946 I felt quite free to say whatever I wanted. Then very soon, at the end of '46, it became clear that the Russians would not agree to international control. Therefore, while I still was in favor of international control, I no longer thought it was an important matter to push and on the contrary it was probably necessary to continue to develop our weapons in an arms race — not as a rush job, but at least to keep it going. And this was in general the attitude which the AEC itself took at the time. So I did not find any conflict in my mind between advocating a sane policy — not in the sense of the SANE organization —eon one side, and on the other side, keeping up the development of nuclear weapons. And I didn't find any strong conflict until the H-bomb came along, and that I have discussed in detail.
WEINER:You did discuss it publicly up to a certain point, but then, once you became involved, you couldn't discuss it.
BETHE:I couldn't discuss the technical things that were happening but I could still say publicly that I didn't like H-bombs, and I will say that today just as much.
WEINER:I thought it was an interesting point to explore.
BETHE:I have always felt that in order to be effective in public policy, whether you do it from the inside advising the government or on the outside, namely talking to the public, it is important for a scientist to have the knowledge to do so. It is important to really talk from an intimate knowledge of the technical problem and that I. have kept up on all the time.
WEINER:Getting back to those years after the war, I think the next thing to pick up is the G.E. involvement. You explained about the summer of '46.
BETHE:Yes, the summer of '46 was a lovely and very productive time— everybody devoted to pure nuclear physics. Then very soon however G.E. decided that it wanted reactor development rather than pure nuclear physics, and so it got itself a contract to develop nuclear reactors from the AEC. The contract may even have come before the AEC was founded, but I'm not sure. It was certainly an AEC contract. This seemed fine to me. I was very interested. I was especially interested in one type of reactor, namely the breeder reactor. I stimulated and did calculations on some experiments on the breeder reactor, just how it would work, which were done by G.E. They didn't have very good experimental facilities in those days and the main technical problem was the capture of neutrons by plutonium in contrast to the fission: Plutonium was obviously the element to use as a breeding material because it produces nearly 3 neutrons pe9 fission. You need one of these to make the fission itself, a second to reproduce the plutonium which you have used, and the excess over two can give you breeding. We learned in the course of time by some quite interesting and ingenious experiments that it was much more difficult to make a breeder reactor than we had thought It was not sufficient to keep the neutrons above thermal energy, as we had initially believed, but one had to keep them at -really quite high energy, like hundreds of kilowatts, essentially very close to the energy at which they come out from the fission. That took quite a while to do and there were two very important people at G.E. involved in this. One was Harvey Brooks, who was the head of the physics division of the project, and the other was Henry Hurwitz, who was his deputy — both very ingenious people. At the same time, the basis was laid for the type of calculations which later on were used in reactor calculations everywhere — the so-called group calculations where you divide the neutrons into various groups according to their energy and treat the diffusion of each neutron group separately. That method was invented at G.E. and partly by one of my graduate students. Then the method of making detailed experiments on the critical assembly was also developed at G.E. before any other place. That is finding out much more than the critical mass, finding out energy distribution of the neutrons and properties of the neutrons inside. And third, this matter about the capture of plutonium. So it was a very fruitful research period. It then ended up by our finding out that you could indeed design a very effective breeder if you kept the neutrons at the initial energy — a fast breeder — and that you could construct a reactor with sodium cooling. And that is still the basis of the breeder reactor today. So I was very devoted to this. There was at the same time the alternative project of developing a reactor for propulsion of submarines and this was under the direction of the then Captain Rickover, now Admiral. And there was some competition between these two aims of the Knolls Atomic Power Laboratory. The Russian bomb in '49 made the AEC decide to forget all nonsense, so never mind, those dreams about a breeder reactor, you go ahead and work for Rickover. I didn't like that at all. The General Electric management completely toed the line and set up no resistance against the change in direction and made the entire laboratory work on the navy reactor. Thereupon I reduced my visits very greatly and gradually faded out. I don't remember the exact time when I finally resigned. It was before '54, but not very long before.
WEINER:The first involvement was '46 with the betatron work, and then did the reactor work start right after that?
BETHE:Right after that in '47.
WEINER:So it was a continuous involvement?
BETHE:A continuous involvement, and for some time I went every six or eight weeks for a couple of days at least.
WEINER:You mentioned that in the first year you went a total of 40 working days, but not quite at that pace the rest of the time.
BETHE:I think it probably stayed at something like 40 working days until '48, maybe even '49, and then it declined very strongly
WEINER:The increased Los Alamos involvement would account for that alone. How did all of this affect your non-expert advising role in terms of publishing normal physics papers? Are some of these reflected in your works?
BETHE:Some of the physics papers are on matters of the G.E. work. I mentioned that Elementary Nuclear Theory was based on the lectures there, but the more important ones — Bethe, Tonks and Hurwitz, "Neutron Penetration and Slowing Down at Intermediate Distances through Medium and Heavy Nuclei" was done with two members of the G.E. physics group and was directly relevant to the work there. It concerned the effectiveness of shielding. I also wrote a paper with Hurwitz alone, "Neutron Capture Cross Sections and Level Density." One of the things which were deduced from these critical experiments I described were the capture cross sections of any element for medium energy neutrons, let's say for neutrons of 1 to 100 kilowatts, and we found there were tremendous variations. And so we got out of that a physics result, namely that these variations are strongly related to the question of even and odd nuclei, and also closed shells of nuclei. There were some direct physics consequences from this. Another thing I ought to mention in connection with G.E. — the question came up of the safety of the fast reactor. And I wrote together with an Englishman by the name of Tait, a theory how to calculate the possible major accidents which could occur with a fast nuclear reactor. This has become the basis of all future work. Fortunately it later on turned out that we had been very pessimistic and that the actual maximum accident is considerably less than we predicted at the time, but that was the first paper on the subject.
WEINER:This has become a field of great contention ever since. But your technical results have been revised, you mean, because of new technical information?
BETHE:Yes, it was essentially a more detailed look at the neutron diffusion in the fast reactor, and also at the pressure wave which could be generated in a fast reactor by an explosion, and a more detailed look at the question of how reactivity can be inserted into a fast reactor. It was these matters which have changed. In fact, I published the revised results later on with one of the man of the Detroit Edison Fast Reactor project — I think that will probably come later.
WEINER:We are resuming now after a lunch break. I think you just completed the reactor story. The final point of the reactor story was the safety work, and you said that took you up to about '54 with G.E. Is that right?
BETHE:It was probably a little earlier. I didn't do terribly much after '50.
WEINER:The question I have next is whether there was any other consulting or any other industrial involvement in that same period?
BETHE:No, in that period there was no other industrial consulting. There was the Los Alamos work which I described. I think that is about it.
WEINER:What was your teaching load like from the period 1946 through about '54 or '55?
BETHE:My teaching load was fairly light. It was one course, usually three hours a week each semester and occasionally I had a semester free of teaching, I guess every 5 semesters I had one semester off. And I had graduate students, on the average maybe 3 graduate students at a time. The first group was extremely able. The ablest of them all was Dyson, who is one of the great physicists now, at the Princeton Institute. Another one of this group became a quite well-known biologist, Lennox, who is one of the senior members of the Salk Institute at San Diego. Then later on—there was nobody as outstanding as Dyson ever—but another very good student came much later in 1960. That was Carruthers, who is now professor here. In the litter before that, there was Ronald Peierls, the younger Peierls, who is one of the main theorists in particle theory at Brookhaven. Then I already mentioned Thouless who came from England.
WEINER:Then before the war, Rose. Did Rose come as a NRC fellow?
BETHE:Rose came as an NRC fellow, yes, and Konopinski. Both of these were post-does. I had relatively few graduate students before the war. It really became much more intensive after the war.
WEINER:In terms of the time distribution, if you have three graduate students and one course, that would be the extent of the direct contact that you would have in teaching?
WEINER:And then there was this synchrotron work which somehow involved you.
BETHE:Not terribly much. I listened to the results. We have a regular Journal Club every week. There's the regular colloquium theory seminar, but apart from the reports and occasional discussions with Robert Wilson, I paid much too little attention to the synchrotron.
WEINER:Except when you worked on specific projects which you discussed earlier. I'm just trying to set the stage for the basic function in addition to the G.E., Los Alamos and some portion of your time in more of these public issues, which we agree was pretty busy, in terms of filling your life.
BETHE:It was a very busy time, I think somewhat to the detriment to my family. I did not pay much attention to my children. I did some, but certainly not enough, and it must have been quite difficult, both for my wife and for my children, that I was so busy and also traveled so much in those days.
WEINER:What about the summers? Did they go with you to Los Alamos?
BETHE:They would go with me, not always to Los Alamos, but we always had a vacation for at least three weeks, usually in connection with the Los Alamos trip. We did take some quite extensive trips to Europe. In those days it was a major enterprise. My father was still living in Frankfurt with his second family, a wife and two children. So every three years we went to Europe, in '48, '51 and '54. In '48 also my wife's parents were in Europe, in Northern Ireland, and in between we took some vacations, usually in the mountains. So I was with my family normally for the vacation which would take anything from 3 weeks to 5 weeks.
WEINER:It's what non-academics generally hope for. Unless there is something you feel we have left out, some theme that we haven't explored in the decade from about '45 to '55, if you are ready to move on, we can begin to characterize this next period, which you described in a certain way, in terms of a shift in your decision of what you would focus on.
BETHE:A shift of my research interest is quite appropriate.
WEINER:I was going to characterize it and try to set the stage. In addition to that, it was the completion of at least one stage of the Los Alamos work, the beginning of your involvement in the test evaluation work which had started a little earlier than that and was a whole new phase of your involvement, and then the more direct advisory functions on PSAC. I don't know whether you want to start within that.
BETHE:Why don't I start with the purely scientific work? I explained yesterday that I decided to go back from high-energy particle physics to low-energy nuclear physics. In a way, that was a fulfillment of my work of the 1930s when I had done low-energy nuclear physics. It was now possible with the new methods to do many of the calculations which in the thirties I thought ought to be done but couldn't be done. So the first work I did was in Cambridge trying to put the Brueckner theory of nuclear matter on a more understandable basis, at least more understandable to me. I wrote one long paper about this which was published in the Physical Review. That's the paper in the middle of page 11 (of the bibliography) called "Nuclear Many-Body Problem." A more important paper was that written by Goldstone in which he gave the direct proof of the Brueckner theory. It is the only valid proof of the theory which has stood up and which made the theory now respectable which it had hardly been before. People thought it was very interesting but perhaps not true. Then thirdly there was the paper together with Goldstone on the differential equation which one obtained from the Brueckner theory for the two-body problem. The title is "Effect of a Repulsive Core in the Theory of Complex Nuclei," and this also has been very useful. Now this started me off on a completely new line of research and I have kept at this ever since. There was the thesis of Thouless which clarified some of the points which we previously made. Then I tried to simplify the Brueckner theory from the calculational point of view, and after quite a lot of work we got a theory which has been very useful as a simple calculational device. That is the paper with Brandow and Petschek, "Reference Spectrum Method for Nuclear Matter." That was published in 1963 but I started working on it back in '60, approximately. It was extremely useful. By now it is not so useful any more because computers have now become so good that one doesn't need any simplification any more. At the same time I was trying to understand the physics better. The aims in this period certainly from '55 to '65 or so, was to understand the binding energy of ordinary nuclei. There is the very striking feature of all nuclei that the binding energy per particle is just about the same for all nuclei and so we wanted to explain why that was so and just how big the binding energy is and what the density of this normal nuclear matter would be. We gave a preliminary answer in this paper with Brandow and Petschek, but the binding energy was not enough. The binding energy came out to be some 8MeV or only 6MeV and it should be 16 per particle. This was especially investigated by Gerry Brown and his collaborators. They tried to find faults in our paper and in the papers by Brueckner and his collaborators. He found a fault in each of the papers. They were different mistakes but correcting the mistakes made it even worse and reduced the 8MeV binding to about 4MeV. So it was in a somewhat unsatisfactory state when I had my next sabbatic. The next sabbatic was in the spring term of '64. In that sabbatic I first spent a month in Pasadena and then a long month at CERN in Geneva where Weisskopf was then the Director, then a month of vacation, and then two months in Copenhagen. It was mainly in the Copenhagen time that I found an important solution, namely, up to that time people had always only considered the interaction of two nucleons, but when you have a complex nucleus, then of course very often three nucleons come close together. I had previously tried to prove that this makes very little difference but I then found, looking at it more carefully, that this had all been a mistake, and that the contribution from three nucleons is, in fact, very large. So I invented a new method to treat the three nucleon correlation, using some work by the Russian Fadayev and it was possible to solve this problem fairly accurately. As a consequence the three nucleon correlation which previously was believed to reduce the binding energy now gave either a zero result or a slight additional attraction. So it increased the binding, and thereby we got quite a long way, maybe to 9MeV or 10MeV binding. Then a young Chinese post-doe — he may have even been a graduate student at that time — C. W. Wong, who was the graduate student of Gerry Brown, had the idea after listening to me talk, in Copenhagen, that perhaps another important point was the type of interaction which one assumes between nucleons. Previously people had assumed what is now known as the hard-core interaction, that is they had assumed that up to a certain distance, something like half a Fermi distance, two nucleons have effectively infinite repulsion so that they cannot get closer than half a Fermi at all. Now, between Wong and me, and I'm not sure who was first in coming out with the idea, we concluded that it might make a considerable difference if one took this repulsion to be finite, that is to have a repulsion at small distance but only by a finite potential energy. This is now known as a soft-core potential. That went afterwards through many ups and downs, just how much effect you have from that. In the meantime we can do these calculations accurately, and it is now known that it makes about 4MeV difference. With this and a few other corrections, some of them contributed again by Gerry Brown, the agreement between theory and experiment is now very good. One gets something like 16MeV from the theory. The theory tends to give slightly too high a density for nuclear matter but, well in the course of time, I hope we will cure that too. At the moment that is the situation. So it was really these two months in Copenhagen which solved the main part of the many-body problem and at the same time it got Mr. Wong interested in this. He has been since then one of the most important contributors to the theory.
WEINER:Where is he now?
WEINER:In Copenhagen for those two months, in addition to having Gerry Brown there who was working on this, were the experimental results coming from Copenhagen of any use to you?
WEINER:What was the particular role of Copenhagen other than the individual presence of you or Brown, as an institution? Was it a focal point for this kind of study?
BETHE:It was a focal point for nuclear physics, and it is, I think, the greatest focal point now and has been all in between. The interest of Bohr and Mottelson was in a different direction. They were mostly interested in collective phenomena and they looked at our efforts with some suspicion. They thought that really our nuclear matter theory would never be of any use. It was a nice sport to try and connect nuclear binding energies with the elementary interaction between nucleons, so they looked indulgently upon our work on this. But even in their book, the first volume of Bohr and Mottelson (Nuclear Structure), it says, well, it is very difficult and probably it won't be of any use.
WEINER:It will be interesting to see if in Volume II there is any reconsideration.
BETHE:Volume II is in press. I think they are by now convinced that it could have some useful answers. Anyway, we kept after this. I had another very able student on this, Mr. Kirson, who in the meantime went to Israel to the Weizmann Institute and is carrying on the work there. Brandow stayed here for some time after taking his degree and some further work was done in collaboration with him, and I mentioned previously that he is one of the most learned people in the general theory of nuclear matter. He is now at the Battelle Institute in Columbus, Ohio, working in nuclear physics. They seem to leave him very much his freedom and consider him an ornament to the Institute. So that was the development of '64 and immediately thereafter. As the next step, I thought it would be important to look at the elementary interaction between nucleons in a more detailed way and to produce a good soft-core potential. So the next thesis which I directed here by Reid was devoted to that problem and Reid's potential is now generally used in these calculations. Then the time was ripe to progress to understand the nuclei a little better, and instead of just having the over-all properties of nuclear matter, we now concentrated on trying to discuss the wave functions and charge distribution of finite nuclei. There is no publication of mine involved with that. Well, there is one which is sort of a precursor, namely "Thomas-Fermi Theory of Nuclei" in 1968.
WEINER:This bibliography incomplete.
BETHE:It is not very incomplete. But the real work was then done by another of my very able students, Mr. Negele, who is now at MIT, who succeeded on the basis of nuclear matter theory to calculate the wave functions of individual orbits of individual nucleons in an arbitrary closed shell nucleus. This, I consider the culmination of the work because we have now gone the whole way from experiments with two nucleons exploring the nuclear force to the theory of the real nuclei as they appear in nature. He can calculate the total energy of such a nucleus, he can calculate the energy required to remove a nucleon from the outer shell or from an inner shell. He found for the first time good agreement between such calculations and experiment for the inner shells. And he can also calculate the distribution in space of the charge of the protons, and found that this was in very good agreement with the Stanford experiments on proton charge distribution in nuclei. So I think with that we have convinced Aage Bohr that there might be something in nuclear matter theory.
WEINER:That raises the question about how many other people were working on this. You mentioned your own work and your students and you mentioned the names of people who helped you get into it in the sense of Brueckner's work and working with Goldstone originally. We are assuming that they went on. And you mentioned Gerry Brown and somebody he had working with him. What about other places? For example, is there any other specific institution which seemed to have a cluster of people, or at least a very strong person, working on the same problem?
BETHE:No, I think Gerry Brown and I between us and Brueckner have pretty much distributed our students over many institutions and it is mostly our students who do this. I should mention one additional person, and indeed a very strong person. That is Baranger at MIT. He got very early into the nuclear matter business, I think about in '64 seriously. And he has a whole group of students at MIT and back at Carnegie Mellon where he was before) and at Oak Ridge, all of whom worked with him and have developed a very beautiful sequel to our theory, which puts it much more into the framework of the type of theory that nuclear shell model theorists are used to. So that's a group of at least six people.
WEINER:I want to get a feeling of this as a cluster of people or a sub sub-group. If you had to estimate on the average of the number of papers published in a given year on nuclear matter in the way that we have been describing it, what kind of figure are we talking about?
BETHE:Maybe six a year. It's a small field.
WEINER:Do you mean six significant ones or six that you would want to look at.
BETHE:Six that I would look at. I have a review article which I wrote over the last two years and which I could give you which has a fairly good bibliography in it. I don't think it is quite complete. It runs to approximately 200 numbers.
WEINER:Covering a 15- or 17-year period?
BETHE:Yes, so that average would come out a little higher. Some of these papers are not directly nuclear matter but most of them are. To write that review art: caused a good deal of labor for me. I started doing this on a trip around the world from fall of '69 to summer of '70, which I started in Japan and ended in Copenhagen. Both in Japan and Copenhagen I did quite a bit about it, in the places in between, not so much. And then I spent about a whole year after my return writing most of that article, so this is, so to speak, a supplement to my Review of Modern Physics articles in the thirties.
WEINER:Would you say of the things that you have done since then that this comes closest to being a similar attempt to summarize a field?
WEINER:How about the Mesons and Fields book?
BETHE:I am not very proud of the Mesons and Fields. Even at the time I didn't have a sufficiently deep understanding of the subject. Other people I think had a deeper understanding and as I said yesterday, almost immediately after this came out, there was a paper by Chew and Low which made the whole book obsolete just about the first year after it came out, or even before it came out.
WEINER:That's the chance you take with anything though, isn't it, including your current review article?
BETHE:. No, I don't think so. With my current review article I have the feeling that I am on top of the situation, that I understand the whole field quite well, and also the field is in a much better state of development. We know much more about this than we knew about mesons when I wrote that book. So I don't believe that this will be obsolete very quickly.
WEINER:Looking back at the period from '55 on, you have identified this as the major theme, or at least as the one you think the most important. It wasn't exclusively this. Can you identify some minor themes? I know there is always a paper here and there, but something significant.
BETHE:In pure physics work, this really goes through my entire work of the last 17 years. Many of the papers I wrote take off from nuclear matter theory and develop related subjects like my paper with Siemens, "Shape of Heavy Nuclei." That uses nuclear matter theory, and then there are review articles. The article with Elton, "Charge Distribution in Nuclei," is also a consequence of the nuclear matter theory. Let's go down the list of the other papers which I published. There is one, "Recoil Momentum Distribution in Electron Pair Production," which goes back to the electrodynamics, the Bethe-Heitler theory. Then the "Role of the "Interaction in High-Energy-Nucleon" with Carruthers, who was then a graduate student, goes back to my meson involvement. "Usefulness of Polarized Targets and the Polarization Transfer Tensor in Reconstruction of the Nucleon- Nucleon Scattering Matrix" is related to nuclear matter. Here is something different, "Negative Meson Absorption in Liquid Hydrogen," with Leon, another of my students. This is a different field more like atomic physics. Then I got for a very short time into the modern field of Regge poles and published a paper with Kinoshita, "Behavior of Regge Poles in a Potential at Large Energy," and there is a second paper on this with Read (a different Reid) and Orear ("Exact Form for Scattering Amplitude in Regge Pole Theory"). I published a book, Intermediate Quantum Mechanics, which was putting down the lecture notes of my second year quantum mechanics course. Then here is a paper, "The Fireball in Air," which was an outcome of my work at Los Alamos where I had for years been interested just how the explosion wave from a nuclear explosion propagates in air. "Shadow Scattering by Atoms" is another result of my teaching, namely I found that a certain part of atomic collision theory had been presented in a very clumsy way in the literature. I found I had to look at that in some detail for my quantum mechanics class, and so I found it could be done simpler and published that. The next one, "New Type of Accelerator for Heavy Ions" came out of my work for Avco, about which I have to talk. The whole idea here was due to the first two people, James and Levy, and I only contributed to it my knowledge of nuclear physics concerning the use to which such an accelerator could be put. Then the next ones are all nuclear matter and the final one, "Energy Production in Stars," is my Nobel lecture.
WEINER:As we said, there were probably some papers left out (of the bibliography).
BETHE:I should perhaps mention one more thing, staying with the purely scientific side. The nuclear matter theory led me back to astrophysics in recent years, namely, in the summer of 1969, I was exposed at the Aspen summer conference to some talks about pulsars, neutron stars. It seemed clear that people didn't know very well how the neutrons would behave at the high densities which you would find inside a neutron star and that this was some problem which I could probably solve, using my knowledge of nuclear matter and nuclei in general. So, on my travels, in Japan I was asked by a German post-doc Berener whether I didn't have some good subject for him to work on and so I suggested this to him, and out of this came our joint publication on nuclei inside neutron matter. That was then extended and much improved in a further publication with Baym and Pethick of the University of Illinois who were in Copenhagen when I was there in 1970. Between us, we solved, I think quite satisfactorily, the question of the size of the nuclei which exist swimming in a neutron gas in the outer shell of the neutron star. Then, from there, we went on to the question of the very interior of the neutron star where the densities might be ten or twenty times normal nuclear density, and I found, when I visited the Tata Institute, that there were some people interested in that. Then in Copenhagen again, Aage Bohr was very interested, and so was a young Indian by the name of Pandari Panda. He had already started calculations on this. I advised him, and he invented in the process of doing these calculations, a new method for treating highly condensed systems, like nuclei or like liquid helium. This method is probably better than any previous method. He is now here since the first of January of this year, and the two of us and another post-doc, Mickel Johnson, are trying to investigate the equation of state at these very high densities. This can be done by methods very similar to the nuclear matter problem so that has absorbed most of my interest for the last year and a half.
WEINER:Where do you think it will lead you — whether it will take you back more into the astrophysics realm again, or whether it is just a good way to test something.
BETHE:I think it is just an excursion. I am interested in the problem. It says I am interested in the astrophysics, but the purely astrophysical part I like to leave to others. We have here Salpeter who is extremely good at these matters and we talk together, but I rely on him and on Tom Gold to tell me the facts.
WEINER:If that is an additional point on the so-called purely scientific side, perhaps now is the time to pick up the other threads, which were simultaneous. One is that along the way you began consulting in addition and the other is the more technical involvement on the test evaluation and a more top-level advisory role. I think perhaps chronological order of whichever came first.
BETHE:First came new consultant engagements. In '54 I was approached by the Detroit Edison Company to consult for them on the reactor I was really interested in, the breeder reactor. This I did with quite some intensity for a considerable length of time. Unfortunately the project ran into lots of troubles and I think it may lead us too far afield to go into all these troubles. The reactor took many years to build. It was finally completed in '66 or thereabouts and then very soon after it was completed it had a small accident which didn't do much damage but scared the operator. It was a terribly silly thing, namely that a thin sheet had come loose and had plugged one of the cooling passages. Fortunately, the operators were extremely alert and immediately shut it down so most of the reactor survived and no real damage was done. Then it took many years to fish out that plate and to recover the reactor. In the meantime, the project has completely run out of money so they don't have the money to replace the fissionable material which is now in the reactor. So therefore the reactor is now being run only to demonstrate that it can be run, which they have satisfactorily demonstrated. And then it is demonstrated whenever there are very high-level visiting firemen to show them what people can do, but it was a very disappointing thing. I think one of the troubles was that it was undertaken with insufficient strength in engineering. There is no substitute for having a really strong engineering team such as Westinghouse or G.E. have. To have a reactor which really works and is well engineered costs hundreds of millions of dollars of investment and an equivalent amount of engineering time. And it was a mistake which I did not then realize to embark on such a project with a fairly good, but only fairly good, team of engineers.
WEINER:Was it clear to the Edison people how much would it be involved, in terms of even the investment that they had planned on?
BETHE:I don't think so at all. It cost far more than they thought. It cost well over a hundred million dollars. They thought it would be a producing reactor, producing power, and on the side, producing some plutonium which they might be able to sell. And I think they had thought that after it was built that the operation would pay for itself, but it never got to that point. I think this was lack of experience both on their part and on my part. I should have advised them not to do it on their own, but I wasn't well enough versed in engineering. There were a number of very competent people: one of them was Mr. Nicholson who spent some time here to get a Master's degree in physics with me, and while he was here, he did some interesting further work on the fast reactor accidents, papers which I mentioned before. At that time we had much more information because we could make critical experiments which imitated the actual structure of the reactor very well, so that we could put much better limits on the size of a possible accident. And we finally found to our satisfaction that at least for the Detroit Edison reactor, even the worst possible accident could be contained in the reactor shell itself without ever getting out into the reactor buildings, so there would be no danger even to the container building.
WEINER:It is on these questions of reactor safety that there is a new kind of public concern. Have you found yourself called upon to give some public responses and explanations and warnings, perhaps, on either side, just as you had done earlier on different issues?
BETHE:I have not been approached by anybody. I got very much annoyed by the speeches and the bill of Senator Gravel who wishes to completely stop the construction of nuclear reactors. In this connection I wrote him a letter which, in the meantime, has been inserted in the Congressional Record, not by him but by Representative Holzimer who is on the joint Committee on Atomic Energy and who made the very nice statement, "I don't agree with Professor Bethe when he talks about arms control, but on these matters, I do." I think it is quite irresponsible how much agitation there is against nuclear energy. In normal operation these nuclear reactors are extremely safe, and this is especially so for the thermal reactors which are the majority of the existing reactors. I have been especially impressed by the successful effort to reduce the radioactive effluent to an extremely small amount, so much so that by now there is less radioactivity coming out of a reactor than there is coming out of a coal-fired power plant because coal contains a little bit of radioactive material which is set free and goes up the smokestack when you burn the coal. And so I think, on the whole, it is a very counterproductive matter to oppose them. It is our only good source of energy for the next thirty years. On the other hand, there is one problem and that is the so-called emergency cooling, core cooling. There is an exceedingly unlikely event that suddenly all the coolant pipes might break and develop a major leak —it is very difficult to put a probability on an event that unlikely —and then you don't get a nuclear explosion, but what you do get is some hot material sitting there, namely the fission fragments, which are radioactive, and make a lot of heat. And if you can't provide new coolant after the old coolant is lost, then this whole reactor core will melt down. That still will never lead to a nuclear explosion but it might release enough radioactivity that might slowly get out to the surrounding countryside, which would be a very unfortunate accident. don't think anybody would die because it would go so slowly that you could use all sorts of evacuation techniques and presumably in the end nothing would come out anyway. So it would not really be a hazard to the public but it would be an infernal nuisance. This has to be taken very seriously —just what to do about this emergency cooling — and I think probably not enough has been done by the AEC on this.
WEINER:Are you involved any more in these kinds of things?
BETHE:I am not involved in it. I asked Dr. Weinberg of Oak Ridge to send me the existing book on emergency cooling and I intend to read that. I have made these statements. I may write an article for the Bulletin some time in favor of nuclear power, but before I do that, I ought to read that book.
WEINER:Is this in the realm of a physics solution or of an engineering solution?
WEINER:Now, the work that you did with Detroit Edison spanned what period?
BETHE:The most active work was from '54 to maybe '60. I appeared for them also in defending a court case, so that they could get a construction permit and so on. I think it went approximately to '60. And then it gradually declined, so that last year, I think I spent less than one day on this work.
WEINER:But the majority of your efforts were in the engineering or in the physics realm?
WEINER:I see, up until this emergency cooling.
BETHE:The emergency cooling doesn't affect the Detroit reactor, but there it was a question of neutron diffusion, teaching them how to compute neutron diffusion the same way as we had developed at Knolls Atomic Power Laboratory, and then insisting on good tests of the burned up fuel elements. Then in developing a theory how you could find out about instabilities of the reactor, and there's a paper on that somewhere — "Reactor Safety and Oscillator Tests" — written in 1956. Then the repeated calculations on safety, first safety against explosions, then safety against minor accidents, expelling the plug in the reactor which is on top of the reactor, and matters like that. So it was what you might call engineering physics.
WEINER:I guess it is a field of physics in itself now. Just talking generally about your scientific work again in that same period, what effect did the development of computers, which had made very great progress during this same period, have on the kind of work which you were doing?
BETHE:Quite a lot of effect. I have never learned to program a computer. However, I insist that each of my graduate students become competent in that and indeed they do. And much of the work which we did in connection with nuclear matter required computers to a high degree.
WEINER:You say "required," meaning that you couldn't have done it in the same time period or you wouldn't have dared pose those questions?
BETHE:Not at all. It would have been such a long calculation that we would not even have started it. It is just beyond the capacity. The work that Negele did in his paper would probably take something like a million years upon a hand computer.
WEINER:That was just a point that occurred to me as we were talking about these papers that this must have been a factor. One other thing: in going through your papers in the library — among the newest additions to the collection, there are many folders. Some of them are connected with conferences; some with specific papers like a polarization folder of 1957, approximately. I notice the style here — perhaps your notes and calculations, and letters from others on that subject — but it is not clear to me, other than working directly with your own students or with someone who is physically adjacent, what your most effective means of communicating with this small group in a field was? Would you exchange drafts of papers for comments, or would you sort of develop points in letters? There is not enough in the files for me to make a judgment.
BETHE:I have written rather few letters. The most important communication was directly face to face. This was partly done by my traveling to various places to give lectures and partly, for instance, by Gerry Brown coming here nearly once a year to spend a few days here with me. And then, of course, there was the Copenhagen time. Otherwise, by actual publication and sending oat pre-prints — very few letters.
WEINER:I wondered whether I was just seeing the tip of the iceberg there or seeing the reality.
BETHE:You were seeing pretty much the reality. Although I haven't gone systematically through the correspondence, there were very few letters.
WEINER:I noticed, for example, there were folders on calculations regarding polarization of protons, scattering of nuclei, the fireball problem calculations are there with some letters from '64, then various conferences. There were two in '57: one on neutron interactions with the nucleus at Columbia, and then one that year on nuclear structure at Pittsburgh. I don't know if you recall anything about these conferences —you made some notes at the Pittsburgh conference on the optical model — I wonder if these were very significant to you, if there was any one of them which had the same function, let's say, as the first Shelter Island Conference when the Lamb shift results and the two-meson ideas and these other things began to come out.
BETHE:No, none of them did. The Pittsburgh conference was quite useful as a test ground for my own theories and finding out just what other people were interested in. You say Columbia was the other? That I don't even remember.
WEINER:Well, Rabi was the president, Havens was the secretary, and there was rather a full program on neutron- interactions with the nucleus. The program was published with abstracts beforehand.
BETHE:It had no substantial influence on my work. Some influence much later in '67 came from a conference in Tokyo.
WEINER:In what way?
BETHE:That was a gathering of lots of people on nuclear physics. Mottelson's talk, for instance, impressed me greatly, just how much' you could do with the collective model. And Gerry Brown had lots of news. The Tokyo conference was a very rewarding conference.
WEINER:Also, I think '56 was the Rochester conference where the discussion of parity came up. Do you recall that? It is interesting to get various people's accounts of whether or not they remember how the discussion went.
BETHE:I certainly remember the discussions of parity, but I didn't have any direct reaction to it. It just seemed a very difficult puzzle at the time, and I did not draw any useful conclusions.
WEINER:That was in '56. Was it Martin Bloch who raised the question about the possible non-conservation which he was embarrassed to raise so he asked Feynman to advance for him? He was ridiculed somewhat, or was criticized that this could not possibly be the case by either Yang or Lee at that meeting.
BETHE:I don't recall.
WEINER:I have seen the mimeographed proceedings of this.
BETHE:I see. I remember more vividly the next conference in '57 when Yang and Lee had their theory and talked about it and Feynman reacted to it. Feynman had the strong feeling that this could not yet be the complete answer. He was searching for something better. He said, "All right, they are surely right in what they have said, but they have said only a part of the story," and that later on led to Feynman and Gell-Mann. He was obviously struggling with an idea but it was quite unclear to him at the time.
WEINER:Do you find at such conferences that you take an active role or are you more of a passive participant?
BETHE:That depends on the subject. In '56 and '57 I think I still was an active participant in the Rochester conferences. Then, soon thereafter, think in '62, I found that I could only understand the experimental papers and no longer the theoretical papers, which were presented at these conferences. And from then on I became a very passive participant. I still was the chairman of a session at the Dubna Conference in '64 on Low Energy Pion Scattering. That was still within the framework of my meson book, so I at least understood what was being said at that session. But generally after that I had the feeling that there wasn't much point in my going to the high energy conferences so I have stayed away.
WEINER:You mentioned that around '55 when you went to Cambridge that you had decided after the publication of the book that the nuclear matter was going to interest you rather than high energy physics as it was developing. I noticed in your notes though, in the archives, that you did teach courses on high energy here in '57 through '59, anyway. The notes are from that period.
BETHE:That is correct. I still tried to keep up with it and as I see from the list of papers, there was an occasional paper on it, but I knew that I was no longer on top of the subject.
WEINER:I noticed also in that period that you have a folder on parity, 1957. I didn't get a chance to study it but I was just wondering whether this was stimulated by the discussion at the Rochester conference.
BETHE:I remember it was stimulated by the papers which came out by Yang and Lee and then others. I was trying to understand and reproduce the results which they had obtained. I was trying to reproduce, for instance, the new meson decay spectrum and I wanted to know at least enough so that I could teach it with very little hope of doing any productive work of my own.
WEINER:So you got that far, and what I see in the file is probably all there is on that subject.
WEINER:I am doing this in a way of filling in some background. When we started talking about consulting activities, you mentioned Detroit Edison. Was the Avco a little later in the game?
BETHE:Yes. There were two other major consultancies. One was General Atomic and the other was Avco. Chronologically, General Atomic was earlier. This was first Convair. Convair asked me to consult for them on the matter of missiles. They were engaged in developing the Atlas missile. However, I never got deeply into this problem. They didn't know quite how to use me and I didn't know how to talk to them. There were not enough people in between who could translate. The chief person at Convair at that time was Critchfield who had worked with me on the proton-proton reaction in the stars and also afterwards at Los Alamos. Then, a little later, de Hoffman went to Convair. De Hoffman got there with John J. Hopkins (I don't know if the initials are correct), who was then the president or chairman of the board of General Dynamics. Hopkins was a very enterprising gentleman and said, "I have now made a lot of money with this company. I would now like to do something for science, and perhaps start a laboratory which in ten or twenty years might make money for the company but for the moment would be mostly pure science, applied research and no development." That led to the establishment of the General Atomic division of General Dynamics in La Jolla, which is a good place to be, desirable in both summer and winter. De Hoffman assembled a large number of very good physicists to work at that laboratory. In the first summer session, there were, for instance, Teller, I, and half a dozen other people of renown and several dozen very good people in addition. In this summer session we talked about possible reactors that this division might develop. One of them on Teller's suggestion was to be a reactor which was completely inherently safe, namely, when you made it hotter it would automatically shut itself down. This led in the course of time to the development of the TRIGA reactor which was eminently successful as a research reactor and was sold all over the country and all over the world and is really a very nice gadget. Then, however, the Division had more ambitions and thought they might also be interested in a power reactor. There, I don't know whose suggestion it was — anyway, it was suggested that it might be nice to use — yes, it was Dr. Fortescu from England who came from a tradition of graphite reactors and was very devoted to gas-cooled graphite reactors. They, of course, have the great advantage that you can operate at very high temperature, therefore with very high thermal efficiency, and this is now getting important because of thermal pollution. They may operate at 45% efficiency instead of 25%. So this seemed an excellent idea and I did a lot of calculations, together with some other people on the neutron diffusion and neutron economy of such a reactor. It turned out to be extremely good, namely it is almost self-sustaining, it almost produces as much material as it consumes. And that also is a very useful feature. I think it is the best reactor to develop for this reason and the thermal pollution reason. Unfortunately, the General Atomic does not have as much experience as General Electric and Westinghouse so they haven't sold many of their reactors. I had many happy summer visits at General Atomic subsequently. I think the first visit was probably '57. The consultation for Convair started much earlier but the consultation for General Atomic started only in 1957. Then I went there nearly every summer. The regular routine was either Los Alamos-San Diego or San Diego-Los Alamos.
WEINER:You mean you split the summer between the two of them?
BETHE:I was perhaps two weeks at each place. Sometimes I was four weeks at San Diego, but not longer. And, of course, it was a vacation very much enjoyed by my family, the children in particular, and it was a lovely land for some time. Then, unfortunately, Mr. Hopkins died and his successor had very little adventurous spirit. He wanted the Division to make money, and his successor, Mr. Lewis, wanted the Division to make lots of money. At the same time he began losing money in other divisions like Convair and astronautics and so on. So the dollar became more important. The interesting physics projects were curtailed gradually and it became scientifically less interesting. The graphite gas-cooled reactor did go on and was still quite interesting but it went more from the physics to the engineering stage, and I had much less to contribute there. So that finally the Division was sold to Gulf Oil Co. and Gulf Oil Co. didn't get along very well with de Hoffman so that after a while they fired de Hoffman very suddenly. I did not like that at all and I resigned my commission. Now, the Convair people had been interested in missile development and knew that here at Cornell there was Dr. Kantrowitz who was the great expert on aerodynamics and was a good friend of mine, so they asked me to approach Kantrowitz to see if he would join the Convair group. As I was approaching him, he said, "I just wanted to approach you because I have signed up with Avco and I have some ideas how to solve the reentry problem, namely the way to do it is with shock tubes where one can make high temperature air, and in this high temperature air you can investigate the effect of the heat transfer from high temperature air to whatever material you use — and we would very much like to have you as a consultant to Avco." So I agreed and joined Avco. This has been my most interesting consultant relation in the entire long history, largely due to the personality of Kantrowitz who is very productive and very enthusiastic and exuberant all the time. It started out with the question of heat transfer to a reentry vehicle which was first measured and it was decided that it was possible to solve the problem with a metal reentry vehicle but then the reentry would have to be slow. Very soon it was felt that one should go to an ablating material, that is, to a material which would evaporate and the best such ablating materials were things like quartz, or mixtures of glass and some organic fibres. If you took something like quartz or glass, the trouble arose that these substances become liquid before they evaporate, and the liquid drops could then dribble back over the surface of the reentry vehicle and you would just release droplets at the end. The whole thing would be a rain of droplets, and then you could only use the heat of fusion, of melting, and couldn't use the much greater heat of evaporation. It was known, however, that glassy substances have a very high viscosity and so people were busy trying to solve some boundary layer differential equations just how that would go. I found a method to solve this, just exactly the opposite way of what they had done, and that is one of the papers.
WEINER:It is not a kind of fundamental physics phenomenon. You are dealing here with known physical characteristics, and the idea is how to control them to achieve a particular desired effect.
BETHE:That is correct. And so we found out just what viscosity you could tolerate and then tried to make a mixture of glass and other stuff which would have that viscosity. Then there was also the problem if you took glass or quartz that the radiation which from the hot air would transfer heat just by radiation to the metal backing the heat shield. And so one of my activities was to investigate the radiation of hot air and we developed a whole theory just how one could measure that and what quantities had to be measured, how you then calculate it, and so on. And they became very expert at this. I paid attention not only to the research lab but also to the development lab which was then called "Research and Advanced Development" and is at Wilmington, Mass., and so I got close to engineering in this connection. I found it very interesting, and, in fact, I had much better relations with the engineering lab than the research lab did, so for some time I was considered a mediator between the research and the engineering lab.
WEINER:Where is the research lab located?
BETHE:That is in Everett, Mass., which is the terminal of one of the MTAs and it is right next to a city dump. It is close to Melrose.
WEINER:You would go though to either one of the labs?
BETHE:Yes. And again for some time my consultation might be as much as 60 days a year.
WEINER:What year did you first start with Avco?
BETHE:I started in '55 just before my sabbatic in England, and then, returning from the sabbatic, I got into it with much more vigor. That was the important time of the ICBM development.
WEINER:And the General Atomic preceded that?
BETHE:It went more or less at the same time. General Atomic started earlier by about a year but then continued through this period after '56. During that time I was absent so much from Cornell that I decided I should go on reduced time and I asked them to put me on 2/3s salary, so that I would have the freedom to go away. One of the research associates would then take over my classes when I was away. At Avco it went, I think, up to about 60 days a year. That included a few days here at Ithaca because I could work on that problem here quite effectively. There were many short visits, whereas General Atomic was usually one long visit in the summer at some time, occasionally another visit in the winter but not regularly. My time was pretty much cut up by that time. Let me tell you more about Avco. Once the reentry problem was solved, the next interesting problem was that of antiballistic missiles — how could they work and what would you have to observe in the reentering missile to use an ABM. During that work I came to the conclusion that you couldn't do very much, that the ABM would always be at a disadvantage because there were so many different ways to decoy the incoming missile and to deceive the defense. Then the third interesting problem, just about when the ABM came to a conclusion, was lasers. This indeed was extremely interesting and is going on at the present time. Avco — essentially Kantrowitz — had an idea how to make extremely powerful lasers and they are now the leading firm in this country to make high-powered carbon dioxide lasers, powers of 100 kilowatts and things like that. This goes on and on, and new inventions are made every time. This involves quite a lot of the things I know. I have some idea about the laser business. There were questions about optics. How would you have to arrange the mirrors to get the right amplification? There were lots of questions-on atomic physics which is one of my specialties. And then there were questions of military applications. There were questions — the modern laser gets its power from a very strong electron beam which goes through the gas — and so there were questions about the behavior of these electrons in the gas. That goes back to many of my previous researches. So it always comes back to the same things — energy losses, scattering, and so on. And the interesting thing of the lab is that nearly every time I go there now go there about every two months — they have some new idea which is interesting and which I like to hear about and have some reaction to.
WEINER:Are there any scientific discussions there that you participate in? You're working now on specific problems. Is there any attempt like that lecture series at G.E. in '46?
BETHE:No. I tried to institute that, but there were only three or four lectures and then after that they gave it up. They do have external lecturers, lots of people who come in, for instance, laser experts who come in and give a talk. So they have something like a colloquium in that there are usually two of these each week. Then they have interminable committee meetings, which is really an exchange of technical information.
WEINER:Among the staff there?
BETHE:Yes, and I have participated in these. When I come there, usually the format is that they bring people at the rate of one group an hour to talk to them. Sometimes it takes two hours. It is fortunately rather relaxed, that is, if something interesting develops, we spend two or even three hours, and the other people just have to wait for another time.
WEINER:So it is like a marathon for you. The interesting thing about this to me is that this is all voluntary and yet at times it has taken a majority of your time, and apparently you get some personal satisfaction out of this.
BETHE:I do, yes.
WEINER:Of course, there is some consulting fee involved, but you could forget about that and just concentrate more on some rather isolated scientific problem dictated by some problems in nuclear matter, or accelerator work, or something else. And yet you chose to do this other. What is the particular attraction?
BETHE:I did it partly for the money. In the fifties, university salaries were miserable. I had a mother to support who couldn't live in our house and had to live in a boarding house which was quite expensive. I had a family to bring up. I liked us to have a good summer vacation and I like to eat well, as it says in the play, so I needed a lot of money. I needed more than I could possibly hope to get from a university salary. So it was partly that that got me into it. Then the Avco thing became so interesting that I am now doing it just as much for the interest as for the money. I like to be involved in things which are real and which are really happening. I like to see when some apparatus which was designed in one of these committee meetings really exists and works... And then I like this very stimulating flow of ideas that is happening there.
WEINER:Do you find that the students that you get in recent years also go in this direction or do they focus on the other aspect of your life, the nuclear matter?
BETHE:They focus much more on the other aspect of my life. In recent years, since relevance has become so important, I have made a point to mention whenever feasible some of the applied work that I have done—for instance, last fall I taught mechanics and I mentioned some of the shock wave problems that I encountered in this Avco work. At other times, in talking about atomic physics, I talk again about the Avco work. And I talk about lasers whenever the opportunity arises in talking about radiation and how you see here that's quantum theory but when you have a very strong light beam it is really quite different and you have to do it in such and such a way. So I try to make the connection to some of the work I have done in the lectures. In my research work here at Cornell I have not made any connection with the consultation work.
WEINER:I think because of the remaining time, I would like to get started now on another phase, and that is the PSAC involvement, which starts in '56. I don't know when the test ban work started.
BETHE:That is really connected with PSAC.
WEINER:You were saying that the PSAC work and the evaluation of testing were simultaneous, or that they are part of the same story.
BETHE:They come together at one point. The PSAC was really the most interesting experience. When I came back from the sabbatic in England, Rabi asked me to join PSAC — at that time it was called simply SAC. It was at that time under the Office of Defense Mobilization. It was somewhat in a corner. It had all sorts of prerogatives. It could investigate absolutely anything it wanted. It had access to the most secret parts of the Defense Department. On the other hand, once it had investigated some problem, hardly anybody paid any attention to the results. Occasionally if there was a friendly Defense Secretary, he might pay a little attention to it. The Committee had access to the President occasionally but was not consulted very much by him. Then came Sputnik. Sputnik changed this overnight. Eisenhower asked SAC to convene, which it did. We had a meeting of, I think, a day, and then we decided what we wanted to talk to the President about, and then went to the President for one hour. This was an unforgettable hour, and completely changed my opinion of President Eisenhower. I found that he was extremely quick, understanding almost immediately what we were after, and acting upon it. Rabi, who was the chairman, was on very good terms with Eisenhower, partly because Eisenhower had been president at Columbia. So it was friendly for this reason, and Rabi was our spokesman. He asked for, I think, five major changes in organization, all five of which were immediately granted. And Eisenhower gave his military aide, General Goodpastor, orders to see to it that this would exactly be instrumented as far as the Defense Department was concerned. One of the things we asked for was that there be a special position in the Defense Department for research and engineering, and this was the office of the Director of Defense Research and Engineering which in the meantime has grown to be one of the most important positions.
WEINER:This is now Foster's job.
BETHE:This is now Foster's job. The first person to have it was Herb York, who is of rather different opinion from Foster. Second — I think this was established not immediately but only after a while, and it was only mentioned at the time that it should be ultimately established — the second thing we asked for was the establishment of a special agency for advanced projects, and that was the start of ARPA. I think York first became the head of ARPA and then the DDRE. There were two or three other things.
WEINER:This was a '57 meeting?
BETHE:November '57, maybe a week after Sputnik. One of the things we brought up was that there should be more emphasis on science teaching in the high schools. And another that there should be a special assistant to the President for science and technology. The first man to take that job was Killian of MIT, and Killian had a very good relation with Eisenhower and really made that job into an important one. An office was established for this special assistant, which is now the Office of Science and Technology. Then a little later, we thought it would be good to have a council within the government departments of all the Assistant Secretaries who have something to do with research. There is one such assistant secretary in nearly every government department, and there is the Council — I forget its name — which meets under the chairmanship of the special assistant. So this was an exciting and most interesting time. The PSAC then had lots of meetings subsequently. I think the meeting schedule was much denser then than it ever has been since.
WEINER:How large was the composition at that time?
BETHE:It may have been 12 to 15. So from that time on we were PSAC.
WEINER:That would have been one of the recommendations then that you have a direct link to the President through the OST.
BETHE:Through the special assistant. And for the rest of Eisenhower's administration the influence of PSAC and OST was really very great, even better under Kistiakowsky than it was before under Killian. I think it is another great point in favor of Eisenhower that he could get along with a scientist who is as much of a scientist and as little of an administrator as Kistiakowsky. Now I have to start somewhere else.
WEINER:May I first ask you a question about the Committee itself? Your general advice was on government science policy and priorities, rather than on specific technical issues?
BETHE:On science policy which could be Defense Department problems and would include the ICBM in that case. The ICBM was taken as once of the tasks. Then there was an ABM Committee started almost immediately after PSAC was started. Then Defense Department Research was small and under our protection. The relation between the research and the actual implementation, that is, how was the dew line functioning? There were people going out to the dew line to see whether it was really working. The installation of BMW, the ballistic missile early warning system, was started and essentially fostered by that. There was a sub-committee which was dealing with intelligence matters. This was, of course, super-secret and only a small part of PSAC was cleared for this. I was not, so whenever we got reports on this they were so obscure that none of us really understood what was going on. Then, on the non-secret side, general science policy, we had a committee on accelerators at one time —which major accelerators should be built — this was a joint committee between us and the AEC. This, for instance, approved the Stanford accelerator. And also out of PSAC came the Ramsey committee which then discussed the future accelerator development. Then, education. There was a committee to study the graduate education in science under Bronk of the Rockefeller Institute. Well, it did almost everything.
WEINER:What about health sciences and biological and medical?
BETHE:In the early days, not much. Then after a while it was felt that this should be part of our problem, and the PSAC was enlarged by putting in some biologists, during my tenure, which lasted to the end of '60. I am sorry to say but I think the physicists usually had a more general viewpoint of the problems than any other scientists.
WEINER:Was it a dominant influence, do you think?
BETHE:The physicists were a dominant influence.
WEINER:Was that because of their numbers as well?
BETHE:It was the number and it was prior involvement with government matters, Los Alamos, government committees, and so on.
WEINER:By this time there was almost two decades worth of experience in this. From the early forties, one way or another, up through this period is almost two decades.
BETHE:That's right. And then finally PSAC set up a panel on disarmament. To this panel I proposed at its first session that we look particularly at the possibility of a test ban. This was in the last days of '57. Now I have to go back to the other committee, to the committee on evaluating nuclear tests. There is not much to be said except that this committee had many meetings. We took the results from the Russian tests, in particular, and then later also from the British tests. So we knew pretty well what the Russians had tested, the yield, and enough about the design to make it fairly clear to us at what stage of development they were.
WEINER:This evaluation was under which agency?
BETHE:Joint AEC and Air Force. So I had some expertise on this. One of the results of this work had been that it was fairly easy to detect a Russian test unless it was extremely small in yield. And so on the basis of this, there was set up a committee by Dr. Killian which was inter-agency to study what a test ban would mean, and we were supposed to study what it would mean to our weapons development, to the Russian weapons development, and to the detection problem. It was fairly easy to write down what it would mean to our weapons development and on the whole we got fairly good agreement on the Russian weapons development, except for the two representatives from the Defense Department who seemed to agree but then got cold feet and decided not to sign the report.
WEINER:Because this would have put them in conflict with other people within their own agency?
BETHE:I would imagine so. The director of military applications of the AEC, General Stauberg, was somewhat against the exercise, but he went along all right. He corrected many sentences in our report and was quite hard to negotiate with, but once the report was finished, he signed it and the signature stayed on. So we had these people. Then we had representatives from Livermore and Los Alamos; Los Alamos on the whole favorable to a test ban; Livermore on the whole opposed to it. We had three people, I believe, from PSAC, and one representative of the State Department who was very much for a test ban. And two representatives from this agency which detects the nuclear explosions — we got in some more of them whenever we needed them, but two of them sat on the committee. And then we could call in experts. Now, as far as detection went, we wrote down what could be done for tests in air and that looked very favorable. Then, the Livermore people brought up the underground problem, and that was much more difficult. But we had one underground test from which we could at least say approximately what would happen. Then, underwater did not seem so difficult, because sound travels beautifully underwater. And then since the space age was beginning, of course, the point was brought up: you might test in space — and that was quite a red herring, in that first it was said that it would be easy to conceal it if it were very high altitude. So that stimulated me to do some research and predict some likely results from a high-altitude test, which then was carried out in the summer of '58, and which gave even more enormous phenomena than I had predicted, so it was very easy to observe. In about three months, we came to some conclusions. We wrote a report. We wrote a page and a half summary because we had been told that Eisenhower would never read more than one page. And then we were invited — Killian and I — to present it to the National Security Council, which we did. There was not terribly much reaction — some questions by Dulles, medium friendly. He wanted to have an agreement but he wanted to be sure that it would not involve too much risk. And very soon after that came the Krushchov proposal that we stop all tests. It was very fortunate and totally accidental that we had gone through this exercise.
WEINER:So, in other words, there was no particular policy decision that had been made that you had been assigned to see if it was feasible? It happened the other way around.
BETHE:It was our initiative, but Killian had gone to Eisenhower, and Eisenhower had given a very favorable response and had said, in early January, yes, he wanted very much that we do this investigation. Krushchov's proposal came in April 1958 and because our previous work existed, Eisenhower could respond to this favorably and propose the conference of experts. So then, in the summer of '58, we had the conference of experts in which I participated as a second-line person. The three main representatives were Fisk of Bell Labs, Bacher and Ernest Lawrence. Lawrence didn't participate very much because he very soon became ill. Then there was assembled a large bevy of experts, many from the detection agencies and then people like myself and Richard Latter and Gahard Braun on the physics of detection. I was there only part of the time — in the intervals I went on a vacation to the Swiss mountains. But this experts conference went very well as you know. It came out with a report that indeed it could be done and you could set limits of detectability.
WEINER:How long did the entire conference last from beginning to end?
BETHE:About ten weeks.
WEINER:I understand that during this period you had to do calculations to solve problems which came up, so you were sort of on call for new things which would come up.
BETHE:Yes. The report was rather favorable. It took some persuasion in Washington which was mainly done by Fisk and Bacher to persuade Present Eisenhower to accept it. Finally he proposed the moratorium to start the first of November or the last of October really. In the meantime, the US was feverishly testing. So were the Russians, that is, the Russians resumed testing to get under the deadline. And in late October the political conference came together. I attended the first three weeks of that conference which was very frustrating because there was no meeting of minds. The essential point was that the Russians wanted a very simple treaty: we stop testing. The Americans wanted a terribly complicated treaty, including a two billion dollar system for the detection of tests in various media. Proposals were put on the table, and so on. After three weeks I left and the conference dragged on a year and a half. In November '59 I went once more to Geneva on a supplementary expert conference — the second working group it was called — to talk about underground testing and new evidence from the American tests in the early fall of '58. In the meantime, the opposition had gathered its forces. Teller was feverishly active. Albert Latta invented his big hole. The Livermore group invented all sorts of ways how to hide explosions in space. Teller suggested one could test behind the moon and the most marvelous things. There were all sorts of meetings in Washington in between to assess these problems. I am afraid I was not sufficiently firm at these meetings and was too easily persuaded by the opposition's arguments. I shouldn't have given in on some of these points which later on turned out to be quite false. Well, we wanted another conference on underground explosions to take cognizance of the big hole and of the difficulty of seeing first motion in the underground explosions. That conference essentially ended up with a split report. It didn't look good and the political conference didn't look good at that time at all. And then it became worse when Congress got into the act in the spring of '60, holding a big hearing in which they were trying to demolish the proposed system of detection which had been devised by our delegation. In this again I behaved somewhat foolishly. I thought it would be useful to point out that even with the big hole and with all these difficulties, a system could be devised which would detect all important explosions. This was a great mistake because I came up with the result that this system would require 600 stations, most of them unmanned but still stations, and so this made big headlines and did me far more harm than good. So this looked very hopeless. Then came the U2 incident. The Russians broke off negotiations, and after that, I felt that this was a lost cause. So after that I wrote the article in the Atlantic Monthly, "The Case for Ending Nuclear Tests."
WEINER:Why does that follow from feeling it was a lost cause?
BETHE:I thought it was important to set down at least all the thoughts that we had had. It was no longer useful to argue inside the government. It was lost there. So it was more useful to bring it to the public and possibly it would be revived later on. And so I thought one should at least set down the arguments which had never been done in public.
WEINER:Did (Walter) Lippman play a role in this at all because I noticed that his name figured in it in the correspondence?
BETHE:He did indeed. That is really how it came about, namely, after the very disagreeable hearing of the joint committee of Congress I thought that something should be written and a good man to write about it would be Lippman. So I got myself an introduction to Lippman, who listened to me very kindly and said, yes, that was a very good idea and he would like to write something about this but he needed some material. Would I write down for him just what I knew so that he could use that as background? And that is what I did. I wrote down 20 pages or so of what I knew and sent it to Lippman. Lippman said, well, it's excellent, but it is so good that I don't want to write about it. Why don't you polish it up a little and I will get the Atlantic Monthly to publish it? And that is how it happened.
WEINER:Did you get a measurable response on this? Did it have the kind of impact you wanted?
BETHE:There was measurable correspondence. It was selected by some organization which is called the Headline Series — maybe you found that in there — which writes up public issues for the high schools. In that it was felt that Teller should be given a chance to answer me, which was all right with me, and then I would have a chance to answer him, which was all right with him. So there is one pamphlet of the Headline Series — I think you can probably get that — which is based on the Atlantic article, somewhat abbreviated, and which has this in addition. There was considerable response — quite a number of letters, some friendly, some unfriendly — and a couple of invitations to talk.
WEINER:I noticed a folder, "Test Ban Lectures." Did this taking the issue outside to the public affect your relationship then with people inside the government?
BETHE:Not with PSAC.
WEINER:What about with the various agencies for which you had done work, including Los Alamos?
BETHE:Not with Los Alamos. They were used to me. Not with the evaluations committee who needed me. I think the military side of that group were somewhat miffed, but the civilians considered it all right, although some of them disagreed with me.
WEINER:But it apparently didn't affect any of the relationships that you had.
BETHE:No, it did not.
WEINER:Since we have a little time left let me ask a question that comes out of this: is the story of the ABM public discussion in more recent years — in 1970, I think...
BETHE:'68 and '69.
WEINER:When was the thing at MIT that we talked about yesterday?
BETHE:That was '69, I guess, at the beginning of Nixon's administration. But this had been going on for quite a while. It started late in '67. I had been for all these years on the ABM committee of PSAC, which met quite regularly, maybe every three months or so. And we went through all the motions of the development of ABM and of decoys and penetration aids and so on, which I also did for Avco, so I had some information both ways. In '67 we were very shocked to hear of McNamara's speech in which he said, now, we'll put up ABM. It was a very funny speech in which he mostly argued why we shouldn't and then he said, that's why we'll do it. So that moved me to appear in public again. I agreed to give a talk at a symposium of the AAAS, Christmas '67, where there was a talk by me and by Garwin — both of us were members of that same committee — then one by Fink, who had just resigned from the DDRE office, and took the opposite point of view, and another man who wasn't important. I think this was very successful and I'm not sure whether we initiated it or the Scientific American — anyway Garwin and I wrote a joint article based on this for Scientific American. The most difficult part of the whole exercise was to get clearance from the Defense Department for my talk which I submitted very obediently to the AEC and the Defense Department and they just sat on it. Finally three days before it was to be given, Foster cleared it with some exceptions which I was glad to take out.
WEINER:This reminds me of the earlier story about the Scientific American original articles.
BETHE:That's right, but by the time we wrote the article it had all been cleared.
WEINER:I see. So what you are saying is that that discussion on March 4th was the tail-end of all this. But the basis of your decision to take it publicly was pretty much similar to the decision on the test ban issue and even on the earlier questions because you felt that you couldn't work effectively and get a hearing there and that this information needed to be transmitted.
WEINER:There is a final question but I don't know if we can do justice to it and that is that we promised that we would follow up on our question of 1967, just after you had gotten the Nobel Prize. At the very end of the last transcript it says: What effect would this have on your work at Cornell and your relationship to research and so forth? And you said that you didn't think anything would change, that it would be substantially the same. Let's take a look at it briefly.
BETHE:That was a good prediction. It hasn't changed. I am doing the same research work. I am having the same kind of graduate students that I used to have. I have not yielded to the temptation of doing only important things. I am doing just as unimportant things as before, or vice versa. And it hasn't changed the line of my research or the direction at all. The only slight change is that I find it a little easier to make people listen to me.
WEINER:At what level — here locally or nationally?
BETHE:At any level. Here outside the physics department. Inside the physics department they listen to me anyway. But outside the physics department and nationally it is just a little bit easier to get a hearing. Otherwise it has not changed my life substantially.
WEINER:What about demands on your time?
BETHE:I have reduced the demands on my time. I am no longer on the PSAC committee. I consult a little less for Avco than I used to. I gave up the consultation with General Atomic. I hardly ever consult for Detroit. I continue to consult for Los Alamos just as much as before, but by now my outside engagements are altogether about 40 days a year instead of being 40 days for one thing.
WEINER:Is that a consequence of the Prize?
BETHE:No. It's rather a consequence of age, if anything, plus I like to have a little more time for myself. But mainly it just developed this way. These two consultations ran out and so did the PSAC committee. There's not much to be said any more about foreign nuclear explosions so that committee is pretty much at an end. There's only Avco which goes on merrily, and Los Alamos, which is somewhat intensifying because they built a meson factory which will work on the part of nuclear physics which specially interests me. So I foresee that I will go a little more to Los Alamos than I used to.
WEINER:For reasons of basic physics.
WEINER:There's lots more to say but I think because you have to be somewhere in a couple of minutes we should stop — for the time being.