Oral History Transcript — Dr. Christian Moller
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Charles Moller; August 26, 1971
ABSTRACT: Student years at Niels Bohr Institutet in the late 1920s; influence of Lev Landau and study of Hans Betheís thesis on scattering of fast neutrons and to a lectureship at the Institute in 1929. Bohrís switch to nuclear physics in mid-l930s; the informal conferences at the Institute. Travels to Rome and to Cambridge, 1935-1936, reporting to Bohr on Fermiís work on resonances. Travel to U.S.S.R. in September and October of 1936; gives talk on Bohrís paper on neutron captive and nuclear constitution; collaboration with Leipunski on k-electrons; comments on life at Physical Technical Institute, arrests of Landau, Houtermans, and Weissberg; tension in Russia. Continued work on capture of k-electrons and meson theory work with Leon Rosenfeld. Teaching; students demand course in quantum mechanics. George de Hevesyís association with the Bohr Institute (biology); popular science writing and publication procedures. German occupation of Denmark, 1940-1945, and the Institute, December 1943 to February 1944; comments on the political and social situation prior to World War II. Werner Heisenberg as head of a German committee investigating the Institute.
Weiner:Today is the 26th of August, and weíre resuming. When we left off, I had just asked you details about the various positions after the doctorate and you explained what you did and that you achieved the status of professor in l943. Last night after I talked with you I worked late, I found all the letters regarding it, so youíre right, in case you had doubts about that. I have another question about lecturing. How often did you lecture? Iím talking of the whole period, and perhaps it changed. But how many times a week, for how long?
Moller:Yes. I think it was three lectures a week -- three lectures a week -- and then we had this colloquium with the students, you know, where the staff also was present, once a week. I think thatís all.
Weiner:And then they attended three of your lectures and three of Hansenís.
Weiner:So they had a pretty full schedule. Then they had a laboratory course in addition?
Moller:Yes, and the people who wanted to concentrate on experimental physics of course in the last years practically were doing experimental work all the time. They didnít follow any lectures then. As a matter of fact, for a very very long time we had no lectures on quantum mechanics, and while Bohr always thought that it was his duty to talk about it, but he very seldom got time for it. He was traveling quite a lot and he was really a very very busy man. So finally, the students made a kind of, what we could call now, ungdomsopror -- you know what that means? What we have now. Yes, revolt. And they came to me and said, ďWe want to have some lectures on quantum mechanics.Ē So I started to give them some lectures on quantum mechanics, and this became then part of the regular courses.
Weiner:It started unofficially.
Moller:It started unofficially, yes, but soon became official.
Weiner:To make it official, youíd have to go through the university?
Moller:No. Professors could more or less decide what they wanted their students to have, at that time.
Weiner:Do you remember what year this was that this change came about?
Moller:It was maybe -- must have been in the middle of the 1930s, I think.
Weiner:So it took that long a period of time before there was an official course in quantum mechanics.
Moller:Yes. Well, of course people had to read books. They commenced to read Diracís book.
Weiner:Did you preserve your lecture notes for that course?
Moller:Oh yes. I have them now written down. Do you want to see them?
Weiner:Not at the moment, but I would like that.
Moller:Well, they were of course somewhat extended later, for small volumes like this.
Weiner:I know about the published lectures. So they came from that period then.
Weiner:Oh, I know those, yes -- I didnít realize they stemmed from that period.
Moller:Well, only the first two stem from that period.
Weiner:Then this becomes a text. Was it similar in those days, that your lectures would be written up and distributed?
Moller:No, this is something later. In my student times we just took notes on what the professor said, and this was hard work, but in a way it was not too bad. It was really quite good, because in the evening you had to go home and try to rediscover what the professor had said. This was a very good exercise. It took quite a lot of energy to do it. So from the point of view of pedagogy, it is bad, but from the point of view of giving some stimulus to the best of the students, this was good actually.
Weiner:I say that was one purpose of pedagogy, and the purpose was served. But then what happened when you lectured on quantum mechanics in the 1930s, did you lecture for the entire year on that subject, or just for part of the year?
Moller:I think it was for the entire year. Yes, one lecture a week.
Weiner:Then what was the alternate? What did you do the alternate year, rely on more standard lectures?
Moller:You mean what we call classical physics? Yes. They were given in two lectures a week. But they were not every year. I mean, there was a two year period.
Weiner:But you did that as well.
Moller:At that time, yes.
Weiner:So one year for example in the 30s youíd lecture on quantum mechanics, the next year on some classical subject.
Moller:No, no, every year on some classical subject, and quantum mechanics extra. The classical subjects were mechanics, electrodynamics, thermodynamics and one thing more -- well, yes, theory of elasticity. These four subjects take four semesters. That is, two, in a year period, so after two years we started again.
Weiner:The quantum mechanics was extra?
Moller:That was extra, yes.
Weiner:About how many hours total, on the average, how many would you be involved in teaching?
Moller:Well, at this period, it may be that I did not have completely regularly the quantum mechanics, but letís say that it was regular, then I would have -- well, three lectures a week, and how many weeks do you have in a semester? You want the number for the whole year?
Weiner:No, per week. Iím just trying to see how you used your time.
Moller:Three hours a week, three lectures, yes. Of course, some of these lectures were I mean I made them quite new, so it was quite a lot of work to prepare these. Of course after you had given them once, the preparation work was not so big any more, but still, I felt that each time you teach on a subject you learn something new and you add a little each time. Though also after these things were made, oral lectures are not following exactly these notes, of course. Thatís later, yes.
Weiner:You mentioned that Bohr being busy during this period, during most periods because of his constant work with the Institute development and so forth, did not lecture. Was it possible for a student to go through without having heard Bohr lecture on any subject? He had no duties
Moller:No, he had no duties. Well, certainly the students would have heard Bohr in the colloquia. There were frequent colloquia, and in the discussions. I think perhaps this was the most important influence Bohr had on the young people. There must be somewhere here records of when Bohr gave some lectures. You know, he was very careful in the preparation of these lectures and it took him an enormous time to prepare the lectures. So there must be some of them written down. I remember one of them, I took notes, and Mrs. Schultz prepared them, a kind of account of what he had said. We also tried to use such a thing, but this turned out to be very bad.
Weiner:Well, with him --
Moller:Yes it was nearly impossible to --
Weiner:Ö I saw a transcript of something heíd done. There was more white space than Ö
Weiner:Well, I have seen manuscript notes which said ďlecture at the Institute,Ē and that being different than ďso and so conference.Ē Iím just trying to reconstruct, to see if there are notesÖ
Weiner:You mentioned that the colloquia played an educational role. What about the annual conferences? We know Bohr started it in 1929. I was curious if the students would participate in that in any way?
Moller:Yes. There you will find on some of the pictures downstairs in the lecture room, there is one picture where in the back row, are four students. I was one of them. I think that must have been the first I attended.
Weiner:These were students at what level?
Moller:They would be in the last year of their studies or something like that.
Weiner:They wouldnít be the ones working towards the doctorate necessarily?
Moller:Not necessarily, no.
Weiner:Because itís hard to find those names on the lists. I know who attended the conferences, but those are only people from the Institute who were staffÖ
Moller:Yes, Of course, the subjects and the discussion were rather difficult. I would think that mostly the students in the last year or the staff of the Institute would attend these conferences.
Weiner:Do you know anything about the planning of the conferences, about how the topic was decided or a cluster of topics was decided?
Moller:As little preparation as possible. It was quite improvised, and the topic usually depended on what one of the guests had to tell of new things. So it was not usually a definite subject, but people who hadÖ
Moller:These small conferences -- no, they were mostly improvised. It depended very much on what happened, what they wanted to tell new, what they had been thinking about and so on. So I never -- I donĎt remember that any of these conferences had a name, a title, ďconference on this and this.Ē
Weiner:I know on certain occasions that Bohr had in mind certain subjects that were hot at the time, and he would invite people who were working on that subject.
Moller:That is certainly possible, yes.
Weiner:Iím thinking for example, in 1932, when James Chadwick wrote to him, sent him the proofs of his letter on the neutron (NATURE) and then Bohr wrote to him and said, ďWhy donít you come to our meeting and tell us more about it?Ē He didnít come, but Fowler was here.
Moller:Oh yes, sure, this is clear, that the invitations may have been influenced by what Bohr had in mind at the moment. But it was very flexible certainly and when people came and had something else in their minds, they would be allowed to talk on that.
Weiner:I guess you can fit a lot in under what Bohr called actual atomic problems.
Weiner:This business of ďactualĒ, I guess it comes from the wrong translation of the Danish word ďaktuelĒ of which the English translation would be ďcurrent.Ē Somehow it was always translated as actual.
Moller:No, thatís true, actual is a difficult word. Deteruirkeligt et problem [It is really a problem] Itís like eventual in English. That is a difficult word for Danes, because ďeventueltĒ means something quite different from the English. ďEventuallyĒ means something that will come in full time or something like that, but in Danish it means, something which may come or may not come. So thereís a s1ight difference in the meaning. I think the same is with actual. In Danish that means the real problem. I think it should have been translated as the real problem, not as the actual.
Weiner:So the English translation would not be current. I was suggesting that it meant current problems -- in other words, the real problem of the moment.
Moller:No, itís not current. Itís the real problem in contrast to a fictitious problem. I think that is in Danish the meaning.
Weiner:Maybe in the sense of fundamental basic problems.
Moller:Something like that.
Weiner:That would be more his feeling anyway. Well, I raise it because around 1936 in some of the letters he talked about a conference on nuclear physics. Now, maybe instead of atomic the word nuclear comes in, because the conferences themselves in that period would tend to focus more on nuclei. His own interest had shifted and also everyone elseís. New results were coming in.
Moller:Well, that was the time of course when Bohr discovered his drop model so itís quite natural that he would concentrate on this subject.
Weiner:On these, do you recall the 1932 meeting? That was the meeting in which Dirac and all those people were here, Lise Meitner was here, Fowler -- itís not necessary to run through the list --
Moller:-- yes, Heisenberg, Pauli -- Delbruck would certainly also have been here at that time.
Weiner:I was concerned about the discussion about the neutron, whether there was very much excitement about it, and how Bohr regarded it in terms of his own work. Joan Bromberg who was here has done a very interesting study of this, but I was concerned more with the actual atmosphere of the meeting.
Moller:Well, Iím not sure that I remember it very clearly. It would have been the time when Dirac thought that he had solved the problem of the divergence and self-energy, by introducing the many time formulation of quantum electrodynamics.
Weiner:This is the one that was described in Faust, isnít it, the Faustus thing?
Moller:That may be.
Weiner:If so I think they give considerable attention to it there. But Bohr did give a paper on the structure of the neutron at that time, at that meeting, and I think Crowther, the British science writer was present also.
Moller:Oh yes, he was there, yes.
Weiner:He may have been present later on, a couple of years later, as well. 1936 perhaps, but I know he was there at that meeting.
Moller:Crowther would probably have made an account of what he heard.
Weiner:Well, I found one account in a popular book that he published three years later.
Moller:By the way, where is Crowther now?
Weiner:He is in England. Heís just written his autobiography, which has been published, and I was asked to review it but didnít because I wanted to talk with him historically and didnít want to prejudice the case. And I guess heís in London. Thatís a different Crowther from the one you mentioned.
Moller:Yes, thatís a different Crowther. I know this one very well. He was very helpful when I came to London for the first time after the war, but I have not heard anything from him for quite a number of years, so I wondered.
Weiner:Well, I assume because of the autobiography that heís still alive and I donít know the state of his health. About the neutron itself, from your own point of view, did you regard it as something of special interest?
Moller:We were very surprised about the neutron, of course, but I must say Bohr was perhaps less surprised than we. Bohr was always prepared that something new could happen. I think I believe Ernest Rutherford had already earlier said to Bohr that something like this might exist. Have you met this some place?
Weiner:Oh, Rutherford yes, as early as 1920.
Moller:Well, it was really an important discovery, because it suddenly changed all possibilities of the theory of the nucleus, because it was such a difficult thing to believe that electrons could be together with protons in the nuclei, held together, and there was also something wrong with the spin. So it was certainly a relief when the neutron was discovered.
Weiner:But did it affect your work in any way? It didnít change your interests?
Moller:Not at that time. It was actually only a little later when Yukawa theory came along, Yukawa theory of meson theory. I became very much interested in it. I believe I was the first to notice this paper here.
Weiner:Did you read it or read the abstract of it?
Moller:I read the paper.
Moller:No, no, that one was written in English. Oh yes, it was in the Japanese journal -- a succession of papers, written in English. I found them very fascinating, and then started the collaboration with Rosenfeld. We wrote several papers on meson theory, as it looked at that time, this is I think all obsolete now.
Weiner:Many things have changed now.
Moller:This was a very interesting period, and there of course the neutron is fundamental and Heisenbergís point of view, that the neutron and proton are two different states of the same particle, very important of course for Yukawaís theory. That was later. That was later, oh yes, 1937, 1938, and it was there that we had to find a name for these particles, and Fredrik Belinfante had introduced a word, what was it?
Moller:Oh, mesotron, that is one thing, yes. It wasnít - - particularly the Americans wanted to have the word mesotron. I think it was Enrico Fermi who said, ďMesotron, it sounds better in Italian than meson.Ē But from the linguistic point of view, it was not too good. The ďtronĒ has no meaning there. Also the nucleons -- I think I was the one who used the word nucleon for the first time.
Weiner:Yes, I believe, everything Iíve read indicates that.
Moller:Yes. But it was a reaction to a term that was used by Belinfante. What was it he called it? Well, this one could find out. Anyway it contained also some letters that were superfluous. Well, we came away from the neutron, but the importance of the discovery of the neutron, was that it suddenly gave an impetus to the theoretical ideas about the nucleus. It removed many many difficulties when suddenly one could come forward -- Heisenbergís work -- and Fermiís, and then Bohrís model of the nucleus.
Weiner:I want to ask you questions on that later, but I was curious about the visits you made to Rome and Cambridge. The details of it, first how the whole idea came up, second, what arrangements were necessary on both ends, and third of course, what you did there and what impressions you had as to people, ideas, atmosphere and so forth. From the beginning, how the idea came.
Moller:Well, Bohr had had for many years connection with the Rockefeller Foundation. As a matter of fact, I think he got some money for the building up of the first Institute and so on. Then the Rockefeller Foundation instituted this fellowship business, and Bohr was active in the establishment of this thing, and quite a number of his students and collaborators got the opportunity to get Rockefeller Fellowships. This you will probably find in the archives, a number of letters. I am not sure that Heisenberg was not here for the first year on a Rockefeller Fellowship. I donít know.
Weiner:I think maybe, in his case. Iím not sure. I have the list of Fellows.
Moller:Yes. Well, then when I had finished the doctoral business in 1932, I think Bohr mentioned for the first time in 1933, if I would be interested in getting such a fellowship, and so it was through Bohr that I received this fellowship to go to Rome for half a year and to Cambridge for half a year.
Weiner:Why those places?
Moller:I think it was my idea. I had become interested in Fermiís theory of beta decay. So, it had appeared just in 1933, I think, and so well -- it may also have been attractive to come to Italy for half a year. And to Cambridge, I had been on a visit in Cambridge before, accompanying Bohr in 1929, I think. Yes, in May, 1929. And I liked the atmosphere there, so I thought it would be nice to come there for half a year.
Weiner:With Fowler in mind, as the person --?
Moller:Well, yes, with the whole group and the atmosphere in Cambridge that I found very very nice. Dirac was there also of course, although one didnít see so much of Dirac. He was always a lonely wolf. So I started out with Rome, and this was a very interesting period of course in Rome.
Weiner:What date did you go there?
Moller:Oh, I suppose the 1st of October, 1934, something like that. That was the time when Fermi had just started his experiments on slow neutrons, the effect of slow neutrons, the bombardment of nuclei with slow neutrons, where he found these extraordinary high cross-sections. I must say Fermi at that time had no time for theory. That was the time when he changed over really to experimental physics. Before that time he had been doing mostly theoretical work. But it was very exciting to see how it was organized. Of course, it was very primitive, very few instruments and, so on, but it was really done in a very rational way. There were four or five or six persons working together, trying to measure these cross-sections, through all the elements, you know. Who w as there? There was Emilio Segre and Gian Carlo Wick, and Wick actually was the one I had most contact with when I was there, because he was the only one who was working actively at that moment in theoretical physics, and we shared a room together at the Institute, in the old Institute on Via Panisperna before the University City was built, outside the walls. So it was very cozy. I mean, not very spacious but very nice, a very nice atmosphere. And who else was there? Franco Rasetti yes.
Moller:Yes, DíAgostino was there. He was a chemist, I think, but his work was very important in connection with this research. And I remember that now and then came from Bologna, I suppose, Rossi, now at MIT, and Ugo Fano, and somebody else, yes I donít recall the name now. Later, after the war he went to Israel, and he died.
Moller:Yes, Racah, he was also there in Bologna, I think. They came down to Rome at frequent intervals.
Weiner:They were working as an experimental team in a systematic effort.
Weiner:How does a stranger then relate to that?
Moller:Well, as I said, I worked practically only in close connection with Wick, but of course our room was close to the rooms where the experiments were taking place and we were talking with them of course. In January, 1935, my wife got ill and I had to bring her home, and on that occasion I gave a colloquium here and told the colleagues here about what they were doing in Rome. I remember Bohr became very interested in this strange phenomenon that Fermi had discovered.
Weiner:You mean the high cross-section, the resonances?
Moller:Yes, exactly. I think that was then the beginning of his thinking about how the nucleus could be constructed. He started then in collaboration with Fritz Kalckar. Fritz Kalckar was the present year in California.
Moller:Yes, you know, Jorgen Kalckar who is here now, he is the nephew of Fritz.
Weiner:He died in 1937?
Moller:Thatís right, he died suddenly in 1937. I think he was the one who was working with Bohr, helping Bohr writing up things.
Weiner:He traveled with him to the U.S. in 1937 to Berkeley and so on.
Weiner:How long did you stay when you came for the colloquium?
Moller:Oh, I stayed perhaps for a week or so. My wife had to go to a sanatorium. So I went back to Rome to finish my stay there.
Weiner:During this period, did you have --
Moller:At that time, I just recall this colloquium. Plesset was present and John Wheeler was there at that time.
Weiner:What was the response to this news? Had they heard it?
Moller:Oh yes, they had heard something about it. But well, it was quite natural that I told them what I had seen there quite recently. Many of these things were not published yet. After all, it was nearly like a factory -- I mean, they very quickly went through the whole periodic table.
Weiner:So even though theyíd read about it, the latest news and the emphasis were what you brought.
Moller:Yes, I think so. You had better ask Wheeler, for instance, because he was there at the Institute listening to it.
Weiner:As a matter of fact, I donít recall now his response -- I did talk to him a couple of years ago but didnít know how to ask the right questions. So this chance coming home brought the two institutions into close contact.
Weiner:About Rome, did you come in contact with Fermi really? Did you have an opportunity to discuss theoretical work with him?
Moller:Well, at that time, I had just read the paper by Pauli and Victor Weisskopf on the quantization of the Klein-Gordon equation, and Fermi asked me what I had been doing recently. So I told him this and then he asked me to give a colloquium on it, so I gave a colloquium on this, and this gave rise to some discussions. But as a whole I was working mostly a1one. I was still interested in the possibilities of describing electromagnetic phenomena by a correspondence method. In contrast to the complete quantum electrodynamics, which while it contained the difficulties of the divergences, and which one later learned to live with, I would say, through the renormalization theory, I still donít regard this as a completely satisfactory theory, Itís a very good theory for calculating things, astonishingly good, but in principle I donít regard it as completely satisfactory theory, because -- well, itís just I said, one has to learn how to live with these things, but still itís not very beautiful. If you do this correspondence method, then you never get these difficulties. Of course I learned this method first of all from Oscar Klein, who used such a method for calculating the spontaneous transition probabilities. And then my method for treating the scattering of fast electrons is actually of the same tape. I mean, there also the intermediate electrodynamics field is not treated as a quantum field but as a classical field. So I tried in Rome how far I could go with this, and I found that one could go one step further. One could also calculate the radiation, the radiative condition, and when I later came to Cambridge in the summer, I finished a paper on that. But of course this method has its limitations. Itís quite all right if you want a first approximation, to quickly get to some results. Then it is very nice, much easier to handle than complete quantum electrodynamics. But of course all these things are contained in quantum electrodynamics. By the way, it was Fermi and Bethe who showed rather quickly after my paper on the scattering that you get the same formula from quantum electrodynamics. I think that was also one of the reasons I came to think of Rome. There were quite a number of those I knew who had been in Rome and told me how nice it was there. Delbruck had been there, Felix Bloch and Bethe.
Weiner:How did you know Bethe?
Moller:Bethe I actually didnít -- I had had correspondence with him in connection with my thesis. And I should mention that my work was a relativistic generalization of work he had done in the non-relativistic case, so I wrote him a letter, and told him about a strange thing which I thought, strange difference between the relativistic and the non-relativistic case, and he wrote back to me, and told me that I had neglected some other terms, and if I took them into account, this strangeness could disappear. That was already -- it must have been -- well, about Christmas, 1931, the beginning of 1932.
Weiner:He was in Tubingen, then, was he?
Moller:Yes, I think so. Yes, thatís right. And then he went to Rome, and there he wrote a paper together with Fermi on the scattering of fast electrons, from the point of view of electrodynamics, and found the same formula. Fermi I think also at that time had made his formulation of quantum electrodynamics, which was somewhat different from the one Heisenberg and Pauli produced. So there was good reason to go to Rome, I think.
Weiner:Except you were a little disappointed.
Moller:Well, yes. Well, on the other hand, I could understand that Fermi was more interested in these exciting experiments.
Weiner:Did you get a feeling about the research group itself? Did they seem especially motivated?
Moller:Well, they worked together very very well, I must say. Of course, Fermi was the leading man surely. The others were all a little younger, except Rasetti. Rasetti I think was even older than Fermi. No, I think they worked together very well and it was a very pleasant atmosphere there in the old building. I think was an old ministry building, where they had borrowed a corner. It was on Via Panisperna one of the old streets in Rome, in a big garden. It was, of course a time when from our point of view it was not very nice in Italy. Benedetto Mussolini was at his height, and the Ethiopian War was threatening. I remember this was discussed very much in this small circle. And actually it started then, didnít it, in the summer of 1935. Yes. But at the Institute one didnít feel any of that. I mean, it was only -- there were police everywhere. I was nearly arrested one day when I was taking photographs in Via Nazionale. I didnít know that Mussolini was to pass there half an hour later. So a man in ordinary clothes came up and asked me to follow him, and show my passport. He took me just into an entrance, and there were sitting a number of police people. You see, along the whole street there were police in all the entrances. And unfortunately the day before I had cashed a check in a bank, and shown my passport, and had forgotten to get it back again. So I didnít have any passport. So, they brought me to restritieri, the office where they registered all the foreigners. I told them who I was and so on. So I had to go there, and after some time they let me loose again.
Weiner:Could you speak Italian?
Moller:Not very well. I could understand what they were saying. But this was the atmosphere in Rome.
Weiner:What did the people seem to think about it? Probably there were differences of opinion within the group.
Moller:Well, about the Ethiopian War, I remember, they were quite unhappy about it. But they were not talking too much. It was also not possible to talk too much. Of course I know that most of them were secretly against the regime. They were rather young some of them may not have had a definite opinion. But a number of them had to leave Italy later. Fermi himself and Racah, Bruno Rossi, Rasetti -- I think Amaldi stayed there. He stayed there through the war, yes.
Weiner:How was their position in the university? Did you have a feeling that they were struggling to make a name for themselves because they were under pressure, or was that not a consideration?
Moller:Well, this is very difficult to say. What do you mean by pressure?
Weiner:I mean, to justify their role as basic physicists.
Moller:Yes -- well, I think we all had this feeling.
Weiner:I guess itís always true. I was thinking in terms of nationalism, bringing honor to Italy.
Moller:Ah, I see. No, I donít think that was --
Weiner:Were you there at the time of the supposed discovery, when it was prematurely announced?
Moller:What was that?
Weiner:This was a false discovery.
Moller:Of a new element?
Moller:Oh no, I think that was before.
Weiner:It was some time in 1934. I think it was just before you got there. Giuseppe Occhialini gave me just recently a newspaper clipping from a paper, Orso Corbino made a speech against Fermiís wishes, because Fermi felt it was premature, and it was hailed as a major triumph for Italy.
Moller:Yes, yes, I see. No, I donít think I had any knowledge of that at that time. Later of course these investigations became exciting, because of the discovery of fission, they thought also that they had got trans-uranium, but then it was -- instead it was barium, I think, and others.
Weiner:Did Corbino come into the conversation at all? Did you ever meet him?
Moller:I met him, yes, but I had no contact with him.
Weiner:How about Ettore Majorana? Was he around?
Moller:Majorana was not there at that time. I think I had met him in 1932, I think, here in Copenhagen. He was a very quiet chap, very kind, but rather closed and he was always sitting in the library there brooding about his problems.
Weiner:You mean while he was here?
Moller:Yes. He stayed for a few months. And that was of course at the time of the exchange forces, Majorana forces, you see, among others, but then he -- you know that he disappeared. When was that actually?
Weiner:About 1937, 1938.
Moller:Yes. I may have seen him once in Rome, I think. But otherwise wasnít he at Palermo?
Weiner:No, that was Segre, later -- I think it was Naples, Iím not sure.
Moller:Naples, I see, yes. But he was Sicilian himself.
Weiner:Yes, as was Corbino, actually. Well, I just wanted to get a feeling of the Rome scene. Your work essentially affected by anything going on in your surroundings?
Moller:Actually, not, no.
Weiner:By the way, you mentioned a colloquium you gave. Were there any other occasions for this kind of discussion, when someone gave a paper about his results?
Moller:Yes, let me see. Of course, I was interested in the beta theory which had just come out. But now Fermi was too busy with other things to be interested in his own theory at that moment.
Weiner:Were there any visitors?
Moller:Wick was much interested in it also. So I talked a lot with Wick about it. Well, maybe a result of this, I was in the work together with Bloch. We did some work on the beta theory as it looked at that time. After my stay in Cambridge, which I think we shall come to later, where I met a Russian physicists, from Kharkov -- he was an experimentalist working on the recoil of the neutrino -- at the moment Iíve forgotten his name. I havenít seen him or heard anything about him after the war. Maybe he doesnít exist anymore. Anyhow, he invited me to come to Kharkov in Russia, and I went there in 1936, and there I wrote a paper on the capture of K electrons. I came to think of that now because I think it was influenced by my talks about beta theory. It was an immediate application actually of Fermiís theory. But it was a new phenomenon I think which nobody had thought about before, and it was published in a Russian journal and therefore not very well known in America. So it was rediscovered in America later.
Weiner:Iíd like to talk to you about Kharkov. I hadnít known about that.
Moller:Ok, we can do that a little later. And this paper on the capture of K electrons started some work of Jacobsen here at the Institute when I came back. He did some experimental work. Well, had we come to Cambridge?
Weiner:Yes. I want to know, whether you went directly from Rome to Cambridge, and when you went.
Moller:Yes. Well, I went home to Denmark to see my wife, before I went over to Cambridge, and this was the summer time. It was very quiet in Cambridge, I must say. Dirac I didnít see at all. I saw Fowler. Of course, he was very kind to me. And Max Born was there at that time, gone away from Germany, Pryce, and Homi Bhabha was actually the one I had most contact with during the summer, and we talked about the scattering, my paper on the scattering of fast electrons. I was from the beginning of course aware that it would also give the scattering of positrons. But I thought it was not so interesting because I thought this will never be possible to do any experiments with it. Positrons were a field very new at that time. But Bhabha sat down and calculated it, using this same method as I had used, I mean the correspondence method, and that was during this summer. And now, of course, the Bhabha scattering formula has proved experimentally very well. There one sees again how quickly the development grows
Weiner:Where did you work? In any proximity to the Cavendish lab?
Moller:Yes. I could sit in a room at the Cavendish. But as I said, it was during the summer. Many people were on the holidays.
Weiner:Iím surprised, I thought you had intended to split your year between the two -- but it was actually longer.
Moller:You see, I was in Italy from October till March, and then I came to London before the holidays started, because I came in April. I remember a visit of Brillouin, who gave a talk at the colloquium. I donít know if I should tell you the story of when Fowler fell asleep.
Weiner:Iíd like to hear it.
Moller:Well, Fowler introduced him to us, and told him how happy they were to receive him there and they were looking forward to hearing this interesting lecture. In the beginning, Brillouin was looking at Fowler all the time. Suddenly he discovered that Fowler had fallen asleep. So, he became a little -- he was looking elsewhere. A little later, Fowler started snoring, and Brillouin tried to go on, and -- but then finally Fowler fell off the chair. Then he woke up, and was very bright and cheerful, and after the lecture he went up and thanked Brillouin for his very interesting talk. You know, in England, at least at that time, it was not against good taste to fall asleep at a party, I mean if you felt tired. And Bohr told me that Rutherford was doing that frequently, as soon as there was something that was not so interesting as it could be -- he fell asleep.
Weiner:You mentioned that it was Followerís colloquium. That was regular?
Moller:Yes, I think it was a regular colloquium.
Moller:I think it was a little less regular than that.
Weiner:Who would be participating in it? The Cavendish experimentalists?
Moller:Yes. Actually it was a mixed group of theorists and experimentalists.
Weiner:Was this a continuation of the Kapitza Club?
Moller:No, the Kapitza Club was something else. That was in the evening, and that was actually quite interesting. And this went on during the whole summer, I remember. It was very nice. I gave a talk there also on the thing I had been doing, on this radiative collision. And Bhabha gave a talk on his scattering.
Weiner:This was at the Fowler colloquium?
Moller:No, no at the Kapitza Club. The Kapitza Club was, I think, the most interesting, and more regular than the Fowler colloquium.
Weiner:Where did it meet?
Moller:Where was it? I think it was in a room on the first floor of, I think it was in one of the colleges.
Weiner:Who would be invited to that? Were there regular members?
Moller:Yes. I donít remember how it was organized. I was invited immediately when I came to attend it. I think it was rather informal. I think everybody could come. It was in one of the colleges -- could it have been in Caius College? Bhabha was a fellow of Caius College. But I couldnít say, Iíve forgotten.
Weiner:You say that was more interesting because more informal, rather than a talk and an audience?
Moller:Yes. I remember, yes, Johnny von Neumann gave a talk there in this Kapitza Club, speaking about a subject from his book on quantum mechanics that had just come out, on pure states and mixtures and such, I think it was.
Weiner:We do have the notebook of the Kapitza Club. Probably I think you signed in to each meeting -- I think there are signatures. It would be interesting to check.
Moller:-- Yes. I think also this Russian gave a talk there. What is his name? Alexandr Leipunsky. He made already in Cambridge some experiments on the neutrino recoil in beta decay, and -- well, this renewed my interest also in beta decay theory, and then Felix Bloch came, did a work together there.
Weiner:Yes. Iíve noticed you also had a paper with Subrahmanyan Chandrasekhar and one with Bloch.
Moller:Thatís right, yes. Thatís right. Chandrasekhar was rather unhappy, because Arthur Eddington had got an idea which nobody believed in, that the Dirac equation could not be applied to the electrons in the stars, and he wanted to change the equation, and he got some other formula for the equation of state, for an electron gas in the stars. And so he came to me and told me about it, and finally we wrote a paper which was meant against Eddingtonís view. Eddington was of course not at his highest at that time. He did of course fantastic things before. But he had come into this speculative way of looking at things, and it brought him astray, I think. Although of course, he always was quite interesting to talk to. In 1938, there was a meeting in Warsaw, where a number of theoretical physicists were present. You know that it was organized by, not the United Nations --
Weiner:The group at Geneva, League of Nations, some international cooperation group. Inte1lectuals.
Moller:Thatís right, yes. And there I remember that Eddington was attacked by most of the other scientists, because nobody could understand what he was doing. The only one who really tried, and that was just like him to try to get some connection with Eddington, was Hendrik Kramers. He was just the type of man who wanted to have contact. Much later, -- I donít know if I should say that because -- well, after all, it was told me by himself, Samuel Goudsmit. When I much later met Goudsmit in Brookhaven, we were talking about the last time we had met, and that was in Warsaw at this meeting. And we came to talk about the fight with Eddington. Then he said, ďYou know, one evening, I was then still young and interested, one evening I talked to Kramers and said, ďIs it really so that all physicists become like Eddington when they get old?Ē And then Kramers said, ďNo, most physicists, including you, become dumber and dumber when they get older.Ē So of course, Eddington was a genius, that was clear, so Kramers tried to defend him.
Weiner:At Cambridge Iím curious about the role of Fowler. Would you regard him or anyone as the leader of the theoretical group? Was there a conscious feeling of the theoretical group?
Moller:Not so much actually. Fowler of course was interested in a special type of physics mostly and Dirac was very retiring, and they were the only theoreticians connected with the university, I think, at that time.
Weiner:How about Douglas Hartree, was he there?
Moller:No, Hartree was at that time in Manchester, I think. He came to Cambridge later. Rutherford was still the boss, really the boss. Well, everybody was a little afraid of him, of course because he was very impressive, the way he could talk, when you met him in the corridor to greet him. So, when they built a new lab -- youíve seen that picture -- at the Mond Lab with the crocodile. That was what they called him, the crocodile. In 1938 I think, yes, the summer of 1938, I was in Cambridge to attend a meeting of the Society for the Advancement of Science, had a meeting at Cambridge, and on that occasion I saw the Mond Lab for the first time, and we were shown around it by Rutherford, and then he said, ďThis is supposed to be me. I donít know why.Ē The crocodile.
Weiner:Actually, they had a plaque of him right inside as well, a copy of which is here.
Weiner:Was Rutherford ever at any of these colloquia?
Moller:No. I never saw him there.
Weiner:What about Chadwick? He left shortly after you arrived.
Weiner:Did you get any feel of his role there, and also the circumstances of his leaving; and the response to it.
Moller:No, I cannot tell anything about it, no.
Weiner:Because you know, people expected him to stay on,
Moller:Yes. No, I donít know. I donít think he was a person one could easily come in contact with. He was always a little closed.
Weiner:I know him quite well now, and I can see that he would sort of withdraw.
Weiner:Was there any talk in terms of experimental work, where you had the feeling of trends developing? For example, were they talking about the cyclotron? It was just at this time that they began to make the initial inquiries, also corresponding to what was going on here.
Moller:No, of the experimental work I remember mostly the John Cockcroft and Ernest Walton thing. Of course, in 1929 when I accompanied Bohr to Cambridge, they had started to build this machine, and it was much discussed, if its energy would be high enough to get anything, because according to classical mechanics it would not be possible to go over the barrier. But after the work of Gamow, who was there at that time, it was possible, and was believed that it should have an effect. Jacobsen was in Cambridge the same summer, Ď35, and what was he doing? He was trying I think to construct a new type of Wilson chamber which would be more -- but I think he gave up that work again -- nothing came out of it. Then I remember clearly Leipunskyís work -- Iíve forgotten what else was going on.
Weiner:Actually I guess there was some other high voltage work. Marcus Oliphant was working with Rutherford and they had begun to look into plans for the cyclotron. When did you leave Cambridge?
Moller:I left in September of 1935.
Weiner:Yes, it had barely gotten started.
Moller:I think when I came home they had started here with the cyclotron.
Weiner:Yes, it would be about that time, let me ask you to compare 1929 when you were at Cambridge for a brief visit, though we didnít discuss it but I gather it was a meeting or something.
Moller:No, it was not a meeting actually -- oh yes, Bohr was giving a lecture.
Weiner:So you went as his assistant. Then, comparing that, your brief impression there, with a longer stay as a more mature established person, as it affects your perception of a situation. Anyway, comparing 1929 and 1935, did you see any changes? Were you impressed with anything particularly that differed from your earlier experience?
Moller:I couldnít say.
Moller:Well, it was a very lively place, and very interesting experiments were going on. Who was there among the experimenters? Norman Feather was there.
Weiner:You see, Feather went up with -- at least, Chadwick sent for Feather, I donít know if went up immediately, to Liverpool in 1935. Earlier, there was the year Feather was at Johns Hopkins.
Moller:Well, I canít remember if I met him there, but certainly I met him on some occasions. It may also have been in Ď29.
Weiner:Right. Let me go on to something, skipping back to Copenhagen -- how much time do you think we can spend?
Moller:I think we could have another half hour. Then I should have lunch and then I have to rush off to another meeting.
Weiner:You came back to the Institute. Let me ask the same question -- what did you see in terms of any change of interests? Of course, you had been back for brief periods.
Moller:Yes. I think, when I came back, -- when did they start the building where the first cyclotron was placed?
Weiner:The grant was received early in Ď35, so the building would have started.
Moller:Yes. I think that was -- I think when I came back my first impression was that there was a lot of disorder. They had been digging out something. And Bohr of course had already published, I think, a paper in Nature on the drop model. Yes, he must have. It was at least about that time.
Weiner:Was it clear that his interest had shifted to nuclear questions? Was it partially or --?
Moller:No, I think at that time he had completely changed over to nuclear physics. And I remember when I came to Russia, but that was a year later, they I gave an account of Bohrís paper, so it may be that he was working on it.
Weiner:I think so. In 1935 he was publishing on the Zeeman effect, theory of atomic constitution, quantum mechanics and physical reality, and then, ďCan quantum mechanical Description of Physical Reality be considered complete?Ē
Moller:Yes, thatís right. They were still these more epistemological papers.
Weiner:Then in 1936, ďNeutron Capture and Nuclear Constitution.Ē
Moller:Thatís right. When in 1936 was that?
Weiner:The dateís not here, from the volume number itís hard to say -- yes, an earlier volume.
Moller:Is it the Nature article?
Moller:Yes, so that probably appeared in the summer of 1936. When I came to Kharkov, I gave a colloquium on it in Kharkov. Landau asked me to do that.
Weiner:What about the intended use of the new high tension, high voltage lab and the cyclotron? Was there some plan?
Moller:Well, I donít know.
Weiner:What Iím getting at -- in terms of the biological aspects, was this much emphasized?
Moller:I donít know if it was already from the beginning. Maybe, but I donít know. When did George Hevesy come here? He was here.
Weiner:He was here, I know the origins of it. Money was raised on the basis of biology -- a fascinating story about collaboration between the Institute and several Danish biological institutions -- and the Rockefeller Foundation --
Moller:-- yes, they gave some --
Weiner:Then they paid for the cyclotron too, to supplement the Carlsberg and the Rask Orsted grants.
Moller:I see. You are very well informed.
Weiner:Well, this is a fascinating story. It makes a nice story in itself. But you werenít involved, or were you, at the discussions which led Bohr to his model work?
Moller:Not so much, because letís see, that was the end of 1935, yes, end of 1935. No, he was -- well, he gave quite a number of colloquia, where we met in the small room which is now the lounge. This was the small colloquia room. He would tell about his thoughts, I think his ideas very often came out while he was giving a talk of how he thought things looked at the present moment. One always had the feeling that ideas came up in his mind while he was talking. So I think we had a number of such colloquia in the winter of 1935-1936. And that I think was the period when Kalckar started to become his closest assistant.
Weiner:Who took over your lectures while you were gone?
Moller:How was that? Iíve completely forgotten. Maybe they were just skipped. Students had to read themselves. I think so.
Weiner:As far as the organization of the Institute at that time goes, from what I gather, Rasmussen was Bohrís practical man, administrative and practical.
Weiner:Although Jacobsen was supposed to be in charge at the laboratory, it didnít mean very much because it was his style to work as an individual and pursue his own research.
Moller:-- yes, thatís right. Jacobsen was also a very quiet man. He was even called already in the early days, I think it was Kramers who called him ďthe Quiet Dane.Ē
Weiner:ďThe Silent Dane,Ē I heard.
Moller:ďThe Silent Dane,Ē yes. But he was a very good man and a very good experimentalist, and had ideas also. Rasmussen was as you said a very practical man, marvelous man actually. But he was a little more limited in his interests. I mean, he was a spectroscopist and he stayed with spectroscopy a long time after spectroscopy was not so interesting any more. Of course, there were still the hyperfine structures, things he did in the later years which were still interesting. But Rasmussen was very practical and therefore also used by Bohr. Later he became the inspector of the Institute, as they called it -- inspector. Here, at the Institute.
Weiner:I donít know what that means.
Moller:It meant he had to look after all these practical things.
Weiner:Itís an official title?
Moller:Yes, well, official -- yes. I suppose so, yes.
Weiner:Which would mean administrative?
Moller:Yes, well, itís mostly in the laboratory, you know. Not I mean, not in the money administration.
Weiner:Bohr would still be doing -- by that time, Fru Sophie Hellmann was here.
Moller:Yes, she had arrived on 1935. Yes, I think she was here when I came back from England, thatís right, I think we met her for the first time at a party in -- was it Rasmussenís house or Arthur Von Hippelís? They both lived out in Blihdapark. It may have been in Von Hippelís house. You know, Von Hippel was married to Franckís daughter. By the way, do you know where he is now?
Weiner:Yes, at MIT. Heís just retired. Thereís a special laboratory named after him.
Moller:Yes, I remember he was interested in what George Placzek used to call ďein schmutziger Gebiet.Ē A dirty subject. At that time it was, you know -- it was a real difficult subject. Solid state physics was not in the state that it is now.
Weiner:Von Hippel was an example of many of the new people that were here, that would have been a significant change, I think.
Moller:Yes, thatís true. Victor Weisskopf had come and Placzek, and Otto Robert --
Weiner:And Otto Frisch.
Moller:Yes. He was the one who stayed for the longest time, I think actually. I think he left for England just before the war.
Weiner:Yes. Had Weisskopf and Placzek already been to Kharkov?
Moller:Let me see, was it before or was it after my visit? I think it was after.
Weiner:Placzek came to the U.S. in 1937, so it was pretty close. He was there less than a year.
Moller:Yes, but their visit in Kharkov was very short, wasnít it?
Weiner:Well, it was with the idea of staying for Ė-
Moller:-- yes, but they stayed a very short time.
Weiner:I donít know, I havenít had the opportunity of talking with Placzek but I know Weisskopf told me he was disappointed.
Moller:Yes. I just wanted to get it clear, when it was. In Helsinki, in Finland, there was a meeting of the Scandinavian Naturforskerforening. That was something which had been established over 100 years ago by Orsted, and every five years, Scandinavian natural science research people were meeting at some place, and this was for the last time, in 1936 in Helsinki. The next should have been in Oslo in 1941; then the war was there and after that it has not been renewed, which shows that it had become a little obsolete, these meetings. Well, it was a nice meeting. From Helsinki I went then to Russia.
Weiner:-- how long did you intend to stay, for the summer?
Moller:Well, in fact I stayed for six weeks, all in all, so -- but when I came to Leningrad, I had no money, and Leipunsky had promised to send money from Kharkov for me. There was nothing. So I went to the Danish consul. It was on a Sunday and it was closed, so I knocked on the door and it took a long time, and then an old Russian woman came out, and she couldnít understand what I wanted and I couldnít understand what she said. Finally she understood that I wanted to talk to the Danish consul, and he came out. He was very kind. He lent me some money to go to Kharkov. I sent it back when I came there. Then I stayed one or two days maybe to look at the city, very interesting -- then I came to Moscow and stayed a few days there, because it was a little too early, you know. The term had not yet started in Kharkov. And when I finally went to the station, I think itís called, the station where the trains go for Kharkov, I suddenly met Landau, and he had come back from a holiday in the Mountains, and then he asked me, ďWhere are you going?Ē ďIím going to Kharkov.Ē ďWhich train?Ē And I told him which train. ďOh, Iím going too.Ē So we went down. We had a sleeper. ďWhich car?Ē I said the number. ďOh, thatís the same car.Ē ďWhich bunk?Ē ďItís the same compartment weíre in.Ē It turned out I was in the bunk above him. It was a very nice coincidence. So then I stayed in Kharkov. Well, I think this has completely disappeared -- they were comparatively new buildings, whatís called the Physical Technical Institute, I think it was called, and it was quite nice. A little primitive, I mean, the Russian -- although the houses were rather new, they looked already a little shabby. But the laboratory I think was fine. And the library was quite good, I remember. They were building an enormous Van de Graaff, that was in a -- well, nearly in a cathedral. It was very high. At that time one had not yet invented the pressurized Van de Graaff, So when you wanted to go up with the voltage, you had to have large dimensions. Otherwise you would get sparks. But I think before they really started working with it, the war came and it was completely destroyed. Well, Leipunsky was there, and the German Houtermans was there, yes, and Weissberg. Houtermans and Weissberg both were arrested a month after I had left, well, they all were. Certainly when I left, the big purge started -- I mean, the completely crazy purge started
Weiner:Was there any indication of this when you were there?
Moller:No. I must say, when I talked with Landau he said, ďOh, we are expecting to have a little liberalization of the whole situation, Stalin has now gone in for (agreed to) free elections.Ē Well, that was what they thought,Ē Oh, you should have heardĒ -- and he was very jubilant about it -- ďYou should have heard how impertinent the young people were at the meeting the other day.Ē He liked that. But unfortunately it didnít work out. I mean, probably it was a trick, from the authorities, to get out the opinion of the people and to find out who they should arrest and so on. And then they used the murder of Kirov as an excuse and probably the murder of Kirov was instigated by Stalin himself. So all the physicists at the Institute were arrested shortly, a few months after -- particularly at the beginning of 1937 it became very bad.
Weiner:Who else was there? Among the Russians, the only name you mentioned besides Landau, who was only visiting, was Leipunsky.
Moller:Leipunsky, and Ilya Lifshits -- he was quite young, he as a student of Landauís. I remember him very well, a very lively young man. Well, there was one rather sinister looking fellow, I donít know, I met him later -- Iíve forgotten his name, a Russian. But I came into contact mostly with the immigrants, you know, from outside.
Weiner:You mentioned just two, Houtermans and Weissberg.
Weiner:Houtermans wasnít there, was he?
Moller:Thatís right, oh yes, and his wife and the Houtermans family was there also, of course, his wife and two children. And when the purge started, when Houtermans was arrested, his family managed to get out, and they came here. Well, because he knew, Weisskopf, Placzek and me, we all were here, and Bohr managed to get some money for them, so that could stay until they could go to the United States. And then Houtermans, after a year or two in prison, which has been described by himself in a book, you know -- have you seen this book?
Moller:What was it called? Iíve forgotten now. Weinberg also wrote a book on his experiences.
Weiner:Heís still in England somewhere.
Moller:Heís in England? I havenít seen him since meeting in Hamburg in 1951.
Weiner:Someone in England told me about it.
Moller:I see. Well, he was an engineer basically, so I think he went into industry.
Weiner:I know something about the subsequent history of Houtermans. What about the interests in Kharkov when you were there? What were the dates?
Moller:It must have been September 1936, I stayed in Kharkov, until about the 10th of October. Well, they were much excited of course about this big Van de Graaff, and Leipunsky tried to continue his experiments on the recoil. It was a difficult job at that time. It was actually only after the war that -- in America -- they did very good experiments on that, in Illinois -- yes, in Urbana. Well, as I told you, Landau asked me to give a colloquium on Bohrís papers and I gave another colloquium on the thing I did there, the capture of K electrons as I told you before. But otherwise, well, it was perhaps not the most suitable time I came then, because it was in September I think when the term started -- actually the 1st of October. It was still materially a very difficult time. After all, they had had the big famine in 1932, after the collectivization of the fans, and the food was still very primitive, although as a foreign guest I could choose chicken every day. Otherwise it was mostly Borscht. Of course you get tired of chicken every day. Ah yes, I preferred the Borscht. The Borscht is very nice. But oh, you shouldnít compare the conditions now.
Weiner:I know, I kept thinking of that.
Moller:No, it was really very very difficult materially. Then I went back -- well, together with Houtermans. I flew in a very shaky Soviet plane from Kharkov to Moscow.
Weiner:They had a big conference in Kharkov, but I guess it was later, 1937, the one that Bohr went to, and Peierls.
Moller:Yes, that was later, No, this was outside the season more or less.
Weiner:Iím sorry -- you were talking about the plane to Moscow.
Moller:Yes, we went to Moscow, and there I visited the Igor Tamms Institute, and I met Rumer. You know him? He had been with Born in Gottingen when he was young. He also soon came into difficulties with the regime. Rumer actually disappeared for a year or two and nobody knew where he was. But now he exists again. He is back in Moscow now. Well, at that time, I did not see Kapitza, for good reasons, I think, because it was after -- when was it that Kapitza was kept --?
Weiner:Summer and fall of Ď34 is when -- he went in the summer, then the difficulty in the fall when they kept him.
Moller:So, I see -- so he must have been there when I --
Weiner:-- it was still a difficult period, took him several years before he --
Moller:-- very difficult, yes -- I donít think his institute existed yet, his Institute for Theoretical Problems which Landau later came to. No, that was certainly after I had been there. So I think the theoretical work was mostly done in the Tammís Institute. I gave a colloquium there again on the K capture of electrons.
Weiner:Was Dmitriy Ivanenko around?
Moller:No, I didnít see Ivanenko. No, I didnít see him. I donít know where he was at that time. I think for some time he was also far away, at one of these exiles of his.
Weiner:I donít know about his position at that time.
Moller:I think that was a time when it was difficult for him, later I think his position became much stronger. I donít know. Well, itís very difficult to see through Ivanenko. Heís a very complicated man.
Weiner:Anyway, about that period -- so you ended it up with your talk in Moscow. That was a short stay.
Moller:That was a short stay of one week, and of course I used the opportunity to visit the museums -- I remember in particular, the Museum of Modern Art which was very beautiful. They have one of the biggest collections of Impressionists. Also in Moscow it was very primitive at that time.
Weiner:Who paid for your visit? I understand in those days you paid your way up to the border and then --
Moller:Yes, right. I think Leipunsky paid for most of it, I mean the Institute in Kharkov. I was there for the longest time. I may have received something from Tammís Institute also during this week, I donít know. I donít remember. But at that time, that was in October, in Moscow one had the feeling that the situation became tense, I remember, Rumer was a little jumpy. One morning he came to my room in the hotel and he was walking in big boots, and when he walked down the corridor, he knocked at the door, and I opened it and I said, ďOh gee, I thought it was the OGPU.Ē He looked around and said, ďOne shouldnít talk about that. It was like talking about the devil in the Middle Ages, you know. So I think in Moscow already it was getting a little tense. I also remember, when I went on the train again to Finland, at the border, there was a poor man who was treated terribly by a woman commissar. He was taken off. He was not allowed to go. And suddenly I got very nervous, because if I had all the papers I needed to get out. But she treated me very kindly. Also there was something in his trunk which she objected to. And I had some -- well, I had some weeklies which I bought -- that was stupid, of course some weeklies Iíd taken to Russia, and I was afraid she wouldnít like them. But she was very kind. But one had the impression that there was something coming up. As a matter of fact, it was only a few months later that the whole thing broke down.
Weiner:Was it known to physicists outside of Russia, so when it did happen -- do you recall how you at the Institute heard that things had gone badly?
Moller:I think Bohr got a message about the arrest of Landau, and Houtermans. He was also asked to do something for them. But then of course when Mrs. Houtermans appeared here with the children, we heard the whole story of what happened.
Weiner:Well, the problem is, itís 1 o'clock, Iím an honorable man, so we will stop -- although itís terrible, there are so many things I want to ask.
Well, maybe we can continue the talk.