Christian Moller - Session III

Weiner:

When we left off last time, I just checked the transcript to determine what we had covered, and it was just in October, 1936, when you had come back from Russia. You described the trip and the circumstances. That’s fortunate as a breaking point, because it seems to me that the Institute was in a new stage from about the mid-1930s on. You already described one difference. That was the large number of visitors, people from Germany and elsewhere who were here. The other one was Bohr’s own interests shifting to nuclear physics. There are a number of questions. I’d like to go into that period with these questions in mind and then talk about your own work and a number of other things. I’m very curious about Bohr’s interests. The fact is that in the earlier period his own interests didn’t seem to influence other people at the Institute very much. Then in the later period, he got into nuclear physics as other people were doing all over the world, and if you look for evidence of Institute attention to that subject, you’ll find a great deal of it, in the building of the cyclotron and in the research papers that were coming out on the part of a number of people. I’m curious about whether that was due to Bohr’s own influence or whether it was a combination of that and a reflection of what was going on throughout the world. I really want to contrast his lack of influence in the earlier period to the possible influence he might have had during this period.

Moller:

Well, this is a little difficult to say, but I think it is more the last thing you said. Also the point that of course this new idea of Bohr was a complete breakthrough, in our description of the nuclei, and for a number of the young people who came here, Victor Weisskopf and Hans Bethe and many others, Otto Frisch also — they were so much interested in this new way of looking at the nuclei. Before one had tried to go along with it a little like one had done in the outer reaches of t atom, and Bohr’s — of course, these views came back unexpectedly later with the shell structure, which was something which came much later. But surely Bohr’s idea of this compound nucleus, and the idea that the nucleus was like a liquid drop which — anything which comes from outside immediately communicates with all the particles or very quickly communicates with all the particles, so that the energy is distributed, not on one particle again but on the whole collective thing, and this was a very important step forward. You know also that Fritz Kalckar was working very closely together with him in these years. And then he unfortunately died in 1937. So, I don’t know if this is an answer to your question. It became very natural that — well, also after Hitler came in Germany, we got many refugees coming here, and the number of people here increased, and so —

Weiner:

Many of them didn’t bring these ideas with them. They got interested in the subject when they got here.

Moller:

No, that’s right. That right, yes.

Weiner:

I was thinking of a remark you made to Thomas Kuhn, when he was talking with you about the earlier quantum physics period. You have commented that it was hard for a young person to take up the kinds of problems that Bohr was interested in, which were rather philosophical, not definite.

Moller:

At that time, yes. That was the end of the 1920s where he was struggling with the new ideas of complementarily and these things. But in the 1930s when he started to think about the nucleus, this was more of a physicist, you know, it was not philosophy at all. It came out of an attempt to describe what we saw in the experiments, the behavior of the neutrons, when the nuclei were bombarded with neutrons, and then Bohr’s interest in the philosophical side of quantum mechanics decreased somewhat in these years.

Weiner:

It was easier for other people to relate to the nuclear questions.

Moller:

Yes.

Weiner:

This is a question about the experimental aspects. To be interested in nuclear problems at that stage was also to work very closely with experimental people. Did you perceive any change at the Institute itself in the relations between people who were generally described as theorists and their relationship to the people who were experimentalists, in this stage? In the earlier stage, I may be wrong, but relations may have been completely different because the interests didn’t necessarily diverge but they didn’t converge either.

Moller:

Well, I think like this, that spectroscopy, which is what was mostly done in the early days in the Institute, was perhaps already a little outdated when quantum mechanics was finished. But when the interest came up in the nuclei, it was more connected with the experiments. That was certainly true, especially when the fission problem came up. Also, the question of stopping of fast particles, an old interest of Bohr’s, which he took up at the end of the ‘30s again, and gave rise to a number of experiments here by Jorgen Boggild and some other people. And of course, for the interpretation also of the fission process the idea of the liquid drop model was also very fruitful of course. And Frisch came here to work for several years, and he was very deeply in this problem of fission of course together with Lise Meitner.

Weiner:

I’d like a little later to get onto certain aspects of that. I was thinking about this period in 1936, 1937, 1938, prior to fission, the concern of the publications is I’d say to characterize it as slow neutrons there were people doing work on that. There was a lot of isotope work, some of it related to biology, a great deal of it, as the time increased — some radioactivity still going on. And the interesting thing is, for example, in your work and concerns, you seem still to be on the same thing, positrons, electrons, neutrons, and you do relate, in 1936, positron emission and beta rays, for example, and the capture of orbital electrons by nuclei was 1937 but then by 1938 you’re on mesons, nuclear forces, field theory, that whole type of interest. I have a number of questions about how you see any evolution in your own work, and what relationship your own work has to either work that was going on here or to things that people were thinking about elsewhere, that period from about 1936 to 1939.

Moller:

Yes. Well, it’s quite right that I was mostly in the field of the positron production and problems of that kind. By the way, the paper on the capture of K electrons, that was done when I was in Russia in 1936. When I came back, and I talked about it, Jacobsen started to make some experiments on this. You have also some papers of his on this. Of course, it was a difficult thing at that time to do experimentally, but he had some indications that this process took place, and soon after in America they did a number of experiments which were in rather good accordance with the theory.

Weiner:

Is this the Luis Alvarez work?

Moller:

Yes, the group over there.

Weiner:

Wasn’t there any connection prior to the work by Alvarez with you in a formal way — no correspondence?

Moller:

No, nothing at all. No, I think I came into it — well, it was a continuation of something I started in Cambridge together with Felix Bloch on the beta theory, and also Leipunsky who was in Cambridge tried to measure the recoil, to find the recoil of the neutrino. Well, that was the reason that I came to think about these problems. Also of course, when I was in Rome I had thought — I heard from Enrico Fermi also about his beta theory and so on. But why I Just started in Russia, I really don’t know.

Weiner:

No stimulation there?

Moller:

No

Weiner:

You said Alexandr Leipunsky was there.

Moller:

Oh, Leipunsky was there, and so it was natural to go on thinking about. And later I learned that the Japanese had already thought about this problem of the capture. I got just today … That is an article which Sakata has written in one of the Japanese newspapers on the occasion of the first international conference on physics in Japan in 1953. And there he speaks about — well, he speaks very nicely about the Bohr Institute.

Weiner:

He must have come here — wasn’t it at Berkeley, then came here?

Moller:

Shoichi Sakata? Well, he was here, for a whole year, after I had been in Japan. He says here, “In one of our earliest works, Hideki Yukawa and I pointed out that there are nuclear transitions used by the orbital capture. This also has been found independently.” So they already had worked on that.

Weiner:

I would very much like a copy of this.

Moller:

You can have a copy of that.

Weiner:

I’m interested in Japan and its relationship to places like Copenhagen and Berkeley. The connections are very tight.

Moller:

He just speaks about it here.

Weiner:

Good. This was the work that you had picked up in Russia on your visit, and then followed through here, and in this case Jacobsen, this was a case of Jacobsen reacting to something you were doing.

Moller:

That’s right, yes.

Weiner:

Were there other instances that you can think of prior to that time where theoretical work of your own led to experimental work at the Institute? Also the other way round, whether you picked up theoretical problems based on experimental work that was already going on at the Institute?

Moller:

I can’t think of anything Just now, because the electron scattering experiments were done elsewhere. I don’t think so.

Weiner:

The reason I ask, I was thinking about, when Wendell Furry was here I was talking with him about what he was doing with J. Robert Oppenheimer and others in Berkeley, and they picked up many of their theoretical ideas from experimental results not at Berkeley but at Cal Tech, and the stuff that was going on with Lawrence and the cyclotron for a long time didn’t relate to the theoretical interests.

Moller:

I remember clearly how I started work on the k mesons. That was, I can say accidentally picked up the paper by Yukawa. You know, it was not in the Journal which was the regular Journal you always looked through. And I became very interested in it, because it certainly seemed so natural, and it was just what we needed in order to get a little understanding of the character of the nuclear forces. And I started to think about how I should describe the neutral mesons, if they existed. I think in Yukawa’s paper he talked only about charged mesons, and I found that it was natural to describe the neutral mesons by means of real fields, not complex fields. I wrote a little paper about it in Nature. And then at that time, well, that was in 1938. There was this international conference in Warsaw organized by the, what do you call, not United Nations but League of Nations.

Weiner:

Committee for Intellectual Cooperation, something like that.

Moller:

That’s right. And I traveled together with Rosenfeld down there and we discussed all the way just the question of neutral mesons and this started our collaboration in, from the summer of 1938 until l940 we worked together on the meson theory. We tried to make the theory as analogous as possible to electrodynamics, which probably was not the right thing to do because we see now that the meson fields are so different from electromagnetic fields. Still, that was reasonable to try to start in this way, and this work went on until Rosenfeld had to leave in l940, after, or was it just before, the occupation of Denmark. It was certainly during the war.

Weiner:

I think he left before. I’m not sure but I have that down somewhere.

Moller:

But we had a further paper in progress, and we could finish it by correspondence. I remember one letter I got from him, when it started to become bad. I think he had come to Holland already and it started — that was probably half a year after Holland had been occupied, and he wrote a letter saying that life becomes less and less complicated for us because there are so many things which are not allowed, so many things we cannot get, and so on. And that was — well, then I made a jump into a five dimensional formulation which seemed quite natural at that time, which was actually a failure, didn’t lead to anything. Only it became natural to assume that we didn’t have one type of mesons, but quite a number of them. Later we have found a number of them.

Weiner:

When did you come to that conclusion that you’d need more than one anyway?

Moller:

That was in 1941. But this whole theory was very formal and has not really brought anything very useful.

Weiner:

What was your reaction to Anderson’s and Neddermeyer’s work and Stevenson, I don’t know who else it was, about the discovery of what was then called the meson, 1937-38?

Moller:

Well, actually we believed that the meson which was found then was Yukawa’s meson, and it was actually after the war that it became clear that it could not be the same. It was then only when Powell found the Pi meson that one could see that the type of meson which we had believed was a Yukawa meson was not the Yukawa meson but a decay particle of a Pi meson. It is a question of the lifetime, which was wrong.

Weiner:

Two questions, one is, did the discovery of this particle by Carl Anderson stimulate your interest in the subject, because it seems to me you said in 1938 you were doing something and it was just about the time that this was announced?

Moller:

Well, certainly it was regarded as support of the idea of Yukawa. Of course this was a little false, but it had the effect that all people could believe in it.

Weiner:

In your case you had known Yukawa’s work beforehand. Mo1ler: Oh yes! 1936, I think.

Weiner:

It wasn’t a question of the experimental discovery calling your attention to the —

Moller:

No, no. It was simply that I found the theory so beautiful and gave in such a natural way an explanation of the short range character of the nuclear forces. I think actually Oppenheimer even earlier had suggested the idea that there might be what they called heavy quanta which could give rise, in contrast to the protons, which have no proper mass, proper mass zero, and one would need — consequently you have a long range force. You need quanta of some kind to account for the short range character of the nuclear forces. But this was just an idea, and Yukawa gave a formula which was very beautiful. Of course we know now that things are much more complicated than one thought then.

Weiner:

The indication that Anderson’s discovery was in fact not the Yukawa meson, it’s quite clear that during the postwar period that enough new evidence kept coming in to indicate that that wasn’t the case, but when did it really become clear to you?

Moller:

That was shortly after the war.

Weiner:

Not earlier? In other words, the whole question of lifetimes and everything else —

Moller:

Well, it was not so clear. It was not so clear. I remember Bohr thought that it could be that the meson took a long time to be captured by the nucleus in an orbit, and then the disintegration would take a long time, but it was at a meeting, a visit of Feretti, I think, Feretti who talked about the Italian experiments.

Weiner:

Conversi, Piccioni —

Moller:

You know what these three people were called in the United States? Well, the real title is, Piccioni, Conversi — it ended with Conversi, there were two first. Well, this was of course too difficult to remember.

Weiner:

Obviously.

Moller:

So it was called “Puccini, Puccini, and Conversely.”

Weiner:

And you first learned of it when Feretti came here. This was one of the early postwar meetings. Do you remember when it was, 1946, 1947?

Moller:

I think it must have been 1947.

Weiner:

The first meeting was more of a reunion of people, and Pais came, for example. He was here at that time.

Moller:

Oh yes. Well, Abraham Pais and ter Haar, they came simultaneously. They were very young. They were students of Hendrik Kramers. And Kramers was on a visit here and told me about these two young people. “Oh, they are very bright,” he said, “I would not like to say which of them is the brighter.” Of course, Pais was very quick in learning and so on, had a very quick mind. A fortnight after he had arrived here, we met him in a streetcar, and a tram, and started to speak English to him and he said, “From now on I only speak Danish.” He had already — I think he had cheated a little bit, he had probably studied a little beforehand, but he was very quick arid spoke Danish very quickly. When was that, when did they come?

Weiner:

That was early 1946.

Moller:

Early 1946. Yes. Then it could be in 1946 also that we had a visit from Feretti.

Weiner:

The results were certainly known by then.

Moller:

Yes, I think it must have been 1946.

Weiner:

What was the reaction then?

Moller:

Well, one started, one tried to find all kinds of ways out of this dilemma. But finally one had to accept. But the real solution came only after Cecil Powell had found the Pi meson. That was in 1947, yes, because I met him for the first time in Dublin. I was in Dublin to give a few lectures on a different subject, on the notion of the center of gravity or center of mass in nuclear theory, and Powell was there simultaneously. We were together there for a whole week and he talked about his discovery. So it was quite fresh then. It was quite new.

Weiner:

Do you remember what month that was?

Moller:

In Dublin? That was in June, I think.

Weiner:

That’s interesting. See, the first Shelter Island conference was held June or July of 1947. That’s where Robert Marshak proposed his two meson theory. And he had not yet seen the results, heard the results which were about in print. The timing was just about right. Did Powell subsequently come here to give a talk?

Moller:

Yes.

Weiner:

It seems to me someone told me he gave a beautiful lecture about it. I think it must have been here.

Moller:

Yes. Well, I invited him to come here, when I heard him there. I told Bohr about it and he immediately agreed that we should try to get him to come. He came now and then in these years over here. Not every year but every second year he was here.

Weiner:

Let me go back now. It was quite logical to do this. It’s a separate subject which I think we can get onto also, what happened once you have — once you had the Powell results, what kind of a new game this is. But that’s another story for the moment. A couple of questions — if you follow Bohr’s work from 1936, he has papers on neutron capture and nuclear constitution, 1937, on nuclear transmutations, 1938, nuclear photo effects and resonances, and then there’s some general talks on biology. Would you say that in this period from about 1936 on that the main focus of the Institute was on nuclear problems? If you look at publications it seems that way but sometimes those are misleading because some subjects lend themselves to lots of publications.

Moller:

No, I think that is true. It was mostly on nuclear problems. Oh yes.

Weiner:

Does this reflect itself in the teaching at all?

Moller:

No. No, I don’t think so. The teaching of the students was always quite a lot behind what was going on in the laboratory and in the scientific circles. I don’t think really we had any teaching of the students in nuclear physics before after the war.

Weiner:

If they wanted to learn something?

Moller:

Oh, they had to read. They had to read. After all, there were no real textbooks in this subject. There were reports. There was what we call, PHYSICAL REVIEWS OF MODERN PHYSICS, had articles. The Bethe article for instance, yes. But otherwise a student had to read the original papers which are also very good actually for the students to do.

Weiner:

There were some things that were just coming out, like Franco Rasetti had a book in 1936, 1937, Schilling had a book about that time, anywhere from 1935 on, you start seeing here and there a book, and George Gamow’s earlier book was available.

Moller:

Yes. Well, but Gamow’s earlier book was of course somewhat obsolete, wasn’t it, at that time.

Weiner:

It was obsolete when it was written because everything began to change with his little marks for the electrons. In other words, the student then, to get nuclear physics, would do reading on his own and perhaps he would benefit from the colloquia?

Moller:

The colloquia, oh yes. Yes.

Weiner:

But the lectures, the ones that you were giving, for instance, were pretty much on the same kinds of subjects that you treated when you started?

Moller:

Yes. That was general quantum mechanics. General quantum mechanics was the closest you came to nuclear physics. Of course, well, a student had to know quantum mechanics before he could read papers on nuclear physics.

Weiner:

What about the biological interests at the Institute? It seems that a good deal of the attention during this same period was on these problems.

Moller:

That was mostly George de Hevesy’s department, you know. While he had a number of younger people working with him, and they were doing a very intensive research on all kinds of applications of isotopes for tracing. And he had also collaboration with the Krogh Institute. And finally when Hevesy left, had to leave, during the war, his collaborators went over there (to Sweden).

Weiner:

They didn’t really work with him because Hilde Levi worked elsewhere for example.

Moller:

Oh yes, that’s true, but I was thinking of Seran(?) and some other people. They went over to Krogh Institute I think. It’s true that Hilde Levi had to leave also simultaneously with Hevesy.

Weiner:

Do you remember any discussions leading to the cyclotron? I’m very curious to track down where it started.

Moller:

I know very little about that, because I think that that was when I was still in Cambridge. When I came back, all the plans had been worked out, and I think they had started already, or it was just after I came back that the foundations for the new house…

Weiner:

— yes, remember you mentioned the building. But they were building for the High Tension Laboratory in general, which would include a cyclotron. So you don’t know anything about that?

Moller:

Yes — no, I don’t know.

Weiner:

In this case I have it the other way around. I have a great deal of documentation, written things, but I have nothing that tells me a little bit about private personal discussions.

Moller:

That’s a pity — Ebbe Rasmussen would have been able to tell you a lot, and Jacobsen, of course, Jacobsen first of all.

Weiner:

But the subsequent development in the later period, did you get the feeling that biology was a separate isolated department, or did people in the Institute think that biology was corning to be biology in the sense of physicists doing it, coming to be a relatively major function?

Moller:

I don’t think anybody could foresee this fantastic development we have had in biology in the later years. But certainly this idea of following the atoms in biological processes by means of this trace technique was very fascinating and very useful.

Weiner:

You didn’t get the feeling at the time that the Institute was really beginning to specialize in that subject?

Moller:

No. No, no, I don’t think so. No, it was more the personality of Hevesy which — I think without Hevesy being here; it would probably have been no biological research in this Institute.

Weiner:

There may not have been a cyclotron either.

Moller:

Well, I don’t know. The cyclotron was very useful for making neutron transmutations and such things.

Weiner:

I was thinking of the support for it—it came in the same package as the collaboration with the Krogh Institute.

Moller:

Yes, that’s true of course, but I think that was more exploiting the situation.

Weiner:

No, the results that were promised were delivered in terms of producing the isotopes and so forth.

Moller:

Oh yes.

Weiner:

I have another type of question that relates to publications that — about procedures at the Institute. There were a number of people working here. There were permanent staff, students and guests — and guests for long term or short term. Was there any kind of a protocol within the Institute regarding work to be written up and to be submitted elsewhere? Some kind of formal or informal procedure?

Moller:

I think everybody would, before one sent a paper for publication, one would ask Bohr if he would have a look at it. He very often then proposed changes and I think no paper came out from this Institute without Bohr’s approval.

Weiner:

Including the biological ones?

Moller:

This I don’t know. I would think not. No, no, I would think Hevesy would take over from Bohr on that. Although I don’t know — I mean, Hevesy was of course completely opposite Bohr in this respect, because Hevesy was writing very quickly, and certainly not so careful as Bohr in what he was writing. Has Mrs. Hellmann told you the story? Have you talked with her?

Weiner:

Only preliminary, we’re going to —

Moller:

— she was Hevesy’s secretary for a long time, and there is one very nice story which shows how quick Hevesy was in writing letters and answering letters. He was in Stockholm, it was after the war, and Mrs. Hellmann had come back and Hevesy was still in Stockholm, but she still helped him. So he wrote her a letter, “Please get me tickets” — better Mrs. Hellmann tell the story, it may not be completely correct, “Please reserve some tickets for me for this and this train on this and this day.” No, “Please reserve a ticket on an airplane for Paris or were it was.” Then he wrote about the kind of tickets he wanted and so on and then he said — “No, cancel this, don’t reserve any tickets at all for me.” But the letter was sent you know.

Weiner:

So there would be this screening procedure. Considering how busy Bohr was and how careful he was, was that a considerable delay?

Moller:

Well, you see, in these days one was not so quick in publishing, and sometimes one has the feeling that it would be good if nowadays people didn’t publish so quickly. There may have been some delay, but it worked. It worked all right. And it had all the advantage that if a young man, if Bohr wrote a letter to the editor, then the paper was immediately accepted.

Weiner:

He sent a personal letter accompanying the manuscript.

Moller:

Yes, he usually sent a personal letter — yes.

Weiner:

So that was the editor’s way of knowing that Bohr had pre-refereed this.

Moller:

Yes. And then it was published without any delay.

Weiner:

Were there any instances where there was a feeling of a need for rapid publication, where Bohr would request that?

Moller:

Well, yes. There was for instance, when Bohr was in America in the spring of 1939 or something like that, Rosenfeld was there also. And Lise Meitner and Frisch I think had done this work with the — where they saw directly things come out from the fission. And Bohr knew that in Princeton they were doing similar things, and then he was very angry with us, because while he wrote to the Institute and didn’t get any answer, he wanted to know how far they had come and so on, so the telegram was sent and so on. Well, in such situations he would act quickly, I’m sure.

Weiner:

I’ve looked at some of the telegrams and talked with Rosenfeld and talked with Frisch. It’s understandable because this was a discovery that as immediately being followed up, and before Frisch and Meitner had a chance to do their initial publication, much less their follow-up.

Moller:

Yes.

Weiner:

But I gather from materials I saw here, Bohr had personal concern for them, but he was also I think wanting credit for the Institute. This is my interpretation of it, the way he worded it — that his Institute at Copenhagen, which had really into this kind of work, it was beginning to pay off, and I think in the atmosphere of the US he might have been reacting to this business of upholding his own institution.

Moller:

Yes. Yes. I think that is true. But usually when he was here, he was not quite so — I think you are right, that it was the atmosphere in Princeton which —

Weiner:

— oh, it was more than Princeton. He was just rushing all over, Columbia people, yes — it must have been very difficult. That’s what I said before as soon as you walk into the US you get a different kind of frame of mind.

Moller:

Yes.

Weiner:

Another thing about publications, about the choice of journals — was there some kind of a pecking order in terms of which journal was felt to be most significant for publication of results?

Moller:

Well, in the ‘20s, up to Hitler, very popular was the Zeitschrift fur Physik. It was quick and careful and was widespread, and then the PROCEEDINGS of the Royal Society. These two were the main journals at that time. The Philosophical Magazine had already become old. It was not so much used any more.

Weiner:

What happened after 1933?

Moller:

Well, after 1933 we didn’t want to write in German. So we always tried to publish in English. At that time also the Danish Academy was used very much. And in my case, I continued more or less with the communications of the Danish Academy, because it was so convenient. And they were also very quick and still are quick, except in the summer months when we usually don’t have any money any more. There is month during the summer when they cannot go on. But usually it is quite quick and also they are quite careful.

Weiner:

What about the distribution though?

Moller:

Well, you can have it everywhere. It’s quite well distributed. And then we usually also, we sent reprints out, quite a number of reprints.

Weiner:

What if something was really important in terms of more than routine work, especially significant where you feel it’s going to change a lot of things and you want many people to know about it.

Moller:

Then one would send a letter to Physics Review or Nature.

Weiner:

That would be true now. Was it true then?

Moller:

Well, at that time a letter to NATURE would be the natural thing, or Naturwissenschaften.

Weiner:

Except after 1933.

Moller:

Except after 1933, yes.

Weiner:

When you look through the publications, well, in 1939 you’re finding everything in English pretty much. You find Danish and English and you find Physical Review and Nature, Apparently as the two major publications.

Moller:

Yes.

Weiner:

Bohr’s papers also in Nature. Then you find a number of the Danish journals, not only the Academy but the Fysisk Tidsskrift. Now, was that more popular?

Moller:

That was more popular, although it was very often articles on recent discoveries, written in a popular way so that the physics teachers of the gymnasia also could read it and keep a little track of what was going on. I think I wrote a paper on beta theory and on positron theory and — well then I had a foolish discussion with a man who could not understand about the inertia of all energy, and I wrote a popular article on it.

Weiner:

Mass and energy.

Moller:

Mass and energy, yes. Bohr also from time to time write an article in Fysisk Tidsskrift to tell in a more popular way about what was going on in physics.

Weiner:

In some cases it seems an article that would be published in a regular scientific journal then would be done in a popular version for them.

Moller:

Yes.

Weiner:

Was there a feeling that one wants to do this or that it was good public relations?

Moller:

No, I think one felt a little that it was one’s duty to do it. To try to popularize a little what was going on in physics. Also of course the editor of Fysisk Tidsskrift depended — much on the editor, if he came and said, “We need an article on this or this,” then it was — well, one felt the obligation to do it, and it is also sometimes quite nice to write a popular article.

Weiner:

In this case do you recall who the editor was, in the ‘30s?

Moller:

H.M. Hansen and together with Helge Holst. He was a librarian at the Technical High School, at the library of the Technical High School, and he was much interested in fundamental physics also. He has not really done anything original, I think. He wrote some articles on relativity theory which were not — well, were a little not completely, I mean he understood quite a lot, but some of the things he did not accept. But anyhow he was much interested in physics and fundamental physics and very good as an editor. I think he did most of the work in the editing of Fysisk Tidsskrift at that time. He died shortly after the war, I think.

Weiner:

Was the magazine widely read?

Moller:

Well, it was read by — inside this country, yes, read by the physics teachers, oh yes.

Weiner:

Did this feeling of responsibility to write things in Danish in a more popular way relate at all to the idea of public relations — that is, that since a great deal of the funds and support were coming from Danish sources, not necessarily scientific, that this might be a way of communicating with them?

Moller:

Well, I don’t think really that this played a big role. I think it was more. First of all, it’s very interesting sometimes to write a popular article.

Weiner:

It’s difficult.

Moller:

It’s difficult but it is also fascinating, to try to do it as simply as possible. And we had the feeling that it was much appreciated by the physics teachers. Many of them had been our pupils when they studied at the university, and we knew them. There were not so many students then. So I don’t think that the only consideration of public relations paid such a big role. After all, science was very cheap at that time. I mean, it was much more in order to get money. It was much more important to Bohr that he knew the Carlsberg people personally, and — because the state did not — well the state was paying for the university and so on, but did not give very much to pure research, particular research. That was only after the war that the situation changed completely. Before that, it was really the Carlsberg Foundation that made It possible at all for Bohr to get money for new buildings and for new apparatus and so on.

Weiner:

Rockefeller too.

Moller:

Oh, Rockefeller, oh yes, surely. Rockefeller gave, especially in the beginning, a lot of money.

Weiner:

And Carlsberg gave 150 thousand toward the High Tension Laboratory.

Moller:

And then the idea of that leading to the collaboration with the Biological Institute resulted in a large gift from Rockefeller, including a supplementary gift for the cyclotron. Somehow recently it’s been lost track of but it was very significant. This leads to a question, regarding the popular accounts, to the book that you did with Rasmussen. I guess the original was published in Danish in 1938, then there was a subsequent second edition in 1939, then the English translation in 1940 and I thought I came across a Dutch translation.

Moller:

There was a Dutch translation and after the war a Czech translation also.

Weiner:

Maybe we can start from the beginning on that.

Moller:

The funny thing was that it started actually by a Swedish publisher, Bonnier, I think, whose — who invited young scientists to write a popular book, and I had not seen this. Rasmussen had seen it and he came to me, “Should we sit down and write such a book and try to get the first prize?”

Weiner:

Did they offer a prize?

Moller:

Yes, he offered a prize. Oh yes. Well, actually several prizes. So we started to talk about it; how we should go about such a book, what would be important and so on. We knew of course it had to be very popular because otherwise we would not get a prize. But then we became more and more seriously interested in it, and so finally it was a rather comprehensive description of the situation in physics at that time. I don’t think we left out anything significant. Except that the description of quantum mechanics was very rough because it was so difficult to do it without mathematics. We worked on that for a year, I think, in our spare time, and we had a very jolly time together while we were doing it. Then it was sent to Stockholm. We did not get the first prize. We got a second prize. That was something. Then the permission, of course, to let it be — all this, of course, the Swedish edition — and to publish it in Danish. Or rather it was one of the publishers here, Hirschsprung, which does not exist anymore, they had seen about this and they arranged it all, to have the commission to publish it in Danish. That was in, when was it? ‘38.

Weiner:

1938, the first Danish edition. In the foreword to the book, Bohr wrote it and mentioned that the significant thing about the book is that it was written by collaboration between a theorist and an experimentalist that this is the nature of science and particular important in nuclear science, Did you find that it was difficult to collaborate?

Moller:

No. On the contrary, I think that is completely right, what Bohr says, that it would not have — if I had written the book alone, it would not have been as successful. Rasmussen was very good in explaining the experiments and so on, and I think that was — I mean his contribution was really very important. He used to say, “Well, now I shall write this chapter and you criticize it, “and this was more or less what we did. Often we sat together also and wrote together, but very often we talked about it and then he would write down a sketch of it, and I would read it and we would go over it together. It worked very well.

Weiner:

Your own research interests weren’t in this direction.

Moller:

No, no, but it was — it gave us something to try to get such a survey of what was going on at the moment, and also how it had developed since the end of the last century.

Weiner:

I know of another popular book that was not written by scientists but close to the source and that was Eduardo Amaldi’s wife wrote a book in Italian on the nature of matter and it’s been republished and updated in English now, just recently. She wrote that about…

Weiner:

In the second edition which was 1939, I have no way of knowing the date in 1939. Was there any significant change in the book from the first edition?

Moller:

In 1939 there could not have been very much change. No, I don’t think so.

Weiner:

Fission had come about in the interim.

Moller:

But don’t remember if we had already in 1939 — I really don’t remember.

Weiner:

I’ll have to check that edition and see. That would be a significant difference.

Moller:

Yes. Maybe there was. I knew of course that we had in the first edition, we had a long discussion about atomic energy, where we explained how unlikely it was that one could get out this energy which we knew was there, and even could calculate how much there was. But before the fission process came along, where you put one neutron in and get two or three out in the process, then it was impossible to have any chain reaction. So — well, that was a thing people were interested in so there we wanted to tell them how unlikely it was that it could be used. This we had of course to change completely in the later editions. I mean the postwar editions.

Weiner:

Come to think of it, the English translation was l940. That’s in the library. We can check that, because it seems to me that by that time there should have been some mention of fission,

Moller:

But we had no connection with the British when it came out.

Weiner:

They did say it was translated from the second Danish edition.

Moller:

Yes. Then I think the second Danish edition did not contain anything about this. After all, up to the war it was still not very — it didn’t look very hopeful, to have, to get out the atomic energy. Of course, Bohr gave a talk in Selskabet for Naturlerons Uabredelse in late 1939, I think it was, and it was published also in Fysisk Tidsskrift I think, where he discusses the situation. And he — it was clear to him that it was only the uranium 235 that was active, and if one could make a separation of these isotopes, then one could get out the energy, and even make bombs. But this was such a formidable job, at that time it looked, oh, it would take years and years before one could do it. And maybe if the war had not come it would have taken years and years. Maybe. Well, at one time, it was shortly before the war and I think it was when Bohr was in America, there was a round table talk in the Danish radio where Frisch and Rasmussen and I took part, and Paul Bergse was a — an industrial man who was very much interested in physics and chemistry. He was the head of a firm that made metals. And he was a popularizer of physics and chemistry on the radio and he had arranged this, where we talked about the fission, and during this discussion, I happened to say, “Well, if we get more neutrons out than we have put in, then we have that possibility of having a chain reaction.” But still there was a long way, because the neutrons coming out were still fast and it was necessary to slow them down in order that they could make new fission. Otherwise they would be captured without making fission. But in this article of Bohr’s, he mentioned this, that in principle it looks as if it is possible, but it is technically so terribly difficult that it will take a long long time before it can happen.

Weiner:

When was the radio discussion, do you recall?

Moller:

Well, Bohr was away. Maybe it was the same — yes, I think it was the same time when he was with Rosenfeld in Princeton.

Weiner:

He was away twice in 1939. Once was the US, once was Cambridge. Aage Bohr went with him to Cambridge.

Moller:

Yes, But I don’t think he was in Cambridge. I think he was in America at that time. This, if you want to have the date, we could probably get to know it from the radio.

Weiner:

Also in the archives there are some records of what Danish radio has on —

Moller:

I think also Frisch wrote in his book on Bohr, he writes also about this radio discussion.

Weiner:

In the Rozental volume?

Moller:

Yes. That’s right.

Weiner:

In your book Atoms and Other Small Things in English, there is a point made by Bohr in the preface, I guess, and then one by the authors in the conclusion about the relation of physics to technology. This was more than PR for support of basic research, yet at the same time pointing out how physics can be applied to technology. During this entire period of the 1930s when there was depression, in some countries there was criticism of technology. Did you experience anything like that in Denmark, where there was sort of an anti-science feeling, because sometimes science was identified with technology?

Moller:

No. We didn’t have anything of that, no. We have it a little now. I mean, now the youth is corrupted, you know. I was in Germany now and I was horrified by — well, this confusion, this anti-natural science attitude, this mixture of humanistic viewpoints with, in an unfruitful way, mixed with objective physics, and this subjective kind of science is a dangerous thing, I think.

Weiner:

Well, it occurred in several countries in the 1930s. That’s why I asked. I’ll give you a copy of an article I wrote about a year ago in Physics Today which talks about this in the US in the 1930s, and which I’ve found since was very strong in Britain as well — really an anti-science feeling calling for a research holiday in science. I was just curious, because you had given specific attention to that, whether that was in response to something you heard?

Moller:

No, something we felt we would like to express, I think. That was our viewpoint and it’s still my viewpoint, I must say.

Weiner:

It’s the traditional argument for support of science. The next question relates to that. Was the book popular? It was intended to be popular in the sense of the style of writing, but how were the sales? Was there interest?

Moller:

Oh, it was very good. Well, of course, I mean, small numbers, but I think it was, particularly among the teachers and also among the pupils in the schools, it was quite popular, much more than now the new edition, which has sold very poorly. That is a sign that the interest has gone to other things. Well, I’m a little pessimistic about that development. It doesn’t matter so much if we hurry down — if we break a little bit, it doesn’t matter. But we are going back to obscurantism and believe in all kinds of this parapsychology and all kinds of —

Weiner:

Astrology?

Moller:

Astrology and that is a dangerous thing and this emphasis of faith, in contrast to knowledge and so on. I mean, faith without intellect is an extremely dangerous thing, particularly in Germany.

Weiner:

This is East Germany you’re reacting to?

Moller:

That was in East Germany. But there were a lot of West Germans there and they were the worst.

Weiner:

These are young scientists?

Moller:

There were a number of young scientists. There was one scientist there, or — well, I cannot mention his name — but he was a fellow with whom I had many many violent discussions during the ‘30s when he was on a visit here, and he is now regarded as a big hero. When he appeared on the podium, young people were making, applauded him, like in the Nazi times, especially the ladies were completely crazy. It reminded me of the first and only Nazi meeting I attended in Germany in 1931, in a small place, Rothenburg where I had the first impression of what this — it was before Hitler was in power, but was really frightening. And I didn’t like all this applause of this man, who, I feel, is corrupting. Maybe this should not be —

Weiner:

Well, we have time later. That’s a separate discussion I’d like to get into. Let me get back now.

Moller:

I’m sorry to digress.

Weiner:

No, we could go on for hours on that and some time we should. This is a completely different line of questions or perhaps a single question, about, what else was going on in Scandinavia, other than the Bohr Institute? I tend in my own work to focus on the Institute, but ZI want to know if there was very much physics going on. I have the impression from what you told me about the Scandinavian meeting that was held periodically that it was already obsolete. The last meeting was about 1941.

Moller:

1936 — well, the Skandinavisk Naturforskermodi, that was the last one in 1936, and then the next one should have been in 1941 but was not held because of the war.

Weiner:

That’s right. The point you made was anyway it was obsolete. Was it rather a slow quiet time for physics in other places, Stockholm?

Moller:

Well, I think in Sweden, Stockholm in particular, they were very good in experimental physics. There was not so much theoretical physics. They had actually, they had Oskar Klein and Balla, they had excellent people, but one had the impression that they were a little isolated. But there were of course good experiments going on in Manne Sieghbahn’s Institute, and there were several very good experimental physicists. There was Erik Hulthen and there was in Lund the spectroscopist Ealen, who found the aurora lines in the laboratory, very highly ionized things, the spectra from very highly ionized atoms. And then there was Alfven who was just coming up. He was about my age. He got the Nobel Prize last year.

Weiner:

Who’ll get it this year?

Moller:

I don’t know. I have no idea. Sometimes I have an idea, but I don’t really know. I don’t really know.

Weiner:

It’s due, just about in the future. Miller: Oh yes, it must come very soon. It was very nice today, Willy Brandt, did you see that? He got the Peace Prize. I think that is very good because it can also be of importance.

Weiner:

I haven’t seen the papers.

Moller:

No, it was a surprise also to me completely.

Weiner:

What I’m getting at, the other Scandinavian developments — there was no other single center that really emerges, other than Copenhagen as a strong place.

Moller:

Well, in Stockholm I would say that experimentally it was quite strong, in Uppsala also. I don’t know when they got their cyclotron.

Weiner:

Tomorrow I’m seeing Sten von Friesen. He’s the one who worked on the cyclotron. He spent some time in Berkeley. I was lucky to find him.

Moller:

He will know much more about it. But then a little earlier we had of course Rydberg in Lund, whose work was very important. But of course, these were the tines when it was not a big center. He was rather alone there. Then they had good mathematicians in Stockholm also, at that time. Karlaman and Riess, Marcel Riess and the famous one — well, Fredholm, of course, with the integral equations, he started this whole business, with the integral equations.

Weiner:

What about Thorsten Gustafson in terms of theoretical work?

Moller:

Thorsten Gustafson, yes, he was a theoretical man, and he was very good in organizing things, especially after the war. He has actually done enormously much. Had good connections with the prime minister and in this way he had great influence.

Weiner:

I gather that in Sweden it’s important that there are feuds going on or different kinds of divisions within science which might account for certain people being isolated, other people not.

Moller:

Well, in Sweden they had — now it is not any more like this, but in Sweden there was a time when this particular way of choosing the professors which they had, which was very democratic, caused somewhat disasters sometimes. You know, they were — usually not called, but they could apply, and a number of people were applying, and then there was a committee which had to look into their papers and finally write a report, recommending this, putting them on a priority list. And then people were allowed to read what had been written and they could object to it. And this very often got into the papers, and it caused very bitter bitter fights sometimes between the different applicants, which could cause animosity for life, and they wouldn’t even speak to each other. This was not very lucky. Now it’s much easier. Well, first of all, there are more positions and it is not — well, seemingly it was a very just procedure, but it was very slow. It took years and years often, and resulted really in lifelong animosity, yes.

Weiner:

Was there any examination connected with this kind of choice? When you say submitted papers to this committee was there some kind of uniform examination that one would take?

Moller:

Well, no. They would have to give lectures, test lectures. Prove lectures. Well, it usually took a very long time. I have also been called sagkundskab (expert) in some cases. I mean, there were members of this board. And several times — the last time, was in the succession of 0skar Klein, and this committee was unanimous in appointing. But then some political things came in between and he was not appointed and they took another one. After that I wrote to them, “Now please don’t ask me in the future,” because I didn’t like that.

Weiner:

In Italy they had and may still have the Concorso, which — with similar procedure but based on an examination.

Moller:

I see. No, there was no examination.

Weiner:

They would take an examination for a particular chair.

Moller:

Even for professorships?

Weiner:

Yes. That’s how Enrico Fermi got his chair from Rome. That’s how Segre got his in Palermo and so forth. That’s the way they did it constantly. Then the committee took into consideration the published papers and everything else, but it was on the basis, the examination made a very large difference.

Moller:

I see. No, there was no examination in Sweden, but there were these prove lectures, test lectures.

Weiner:

Well, that might be better. That gives me some background and I’ll fill it in when I talk with people over there. I’d like to get on to another —

Moller:

We have not of course had that in this country. We do not have that system. Either a man is called to fill the chair, he is asked if he wants to have it.

Weiner:

By whom?

Moller:

By the faculty. If the faculty agrees that he is so much better than any other one, one can think of, then he is called. Otherwise, it is made perfectly clear — the position is free, you can apply for it. Usually there are several applicants and then there is a committee — special committee appointed to read their papers and look into the matter. And if they agree on one person, it goes back to the faculty, and if nobody in the faculty has any objections, he would immediately be appointed. It has to go to the Minister of Education but he would always follow the suggestions of the university. Only in cases where there are two which are apparently equally good, then one also has these test lectures, and then the papers come in. But the people are not allowed in the papers to write polemic articles against the other applicants, like in Sweden.

Weiner:

You mean the newspapers.

Moller:

The newspapers. Yes.

Weiner:

Was this the same procedure that was in effect in the l930s?

Moller:

Yes.

Weiner:

For example, in your case, you had been an assistant and a lecturer. Then how do you work up this succession?

Moller:

Well, I was not a successor of anybody. My professorship was personal or extraordinary, as we call it, and still is, by the way. It’s not a chair, as such. I know that my colleagues have tried in later years to change it into an ordinary chair because that would make it easier for them to get a new person when I retire. Otherwise it will be abolished. People can apply — I don’t know how they do it. I don’t think this has gone through. Well, anyhow, in my case, it was, I became a docent first in l940, and it was of course Bohr who suggested that, and this was then changed into a professorship in mathematical physics in l943. So there was — well, in these cases, there are some of them, in these cases there is no question of competition with others.

Weiner:

In other words, this went through the faculty.

Moller:

Oh yes, it’s the faculty, oh yes.

Weiner:

But this wasn’t an open thing. You existed arid the position was created for you.

Moller:

Yes. That’s right, yes.

Weiner:

I think I’ve seen some background on this. Well, now, let me get to a couple of other issues here. We were talking about social and political issues, contemporary things. I wanted to ask about that period in the 1ate 1930s whether such concerns were neglected or not talked about in the Institute, social and political issues which would focus then on war crises, role of science, anything else. Let me put all these questions of mine into one package. For example, when it was clear that there might be problems for Denmark specifically, with Germany, whether there had been some consideration about what would happen to the Institute, what its role should be, whether these were individual decisions or whether there were any kind of informal policy discussions?

Moller:

Well, you see, during the 1930s, personally, since the occupation of the Rhineland, when Hitler occupied again the Rhineland that was in 1936, something like that — from that time on I was convinced that we would have a war in Europe again inside the next ten years. But I am afraid that this view was a rather isolated view, because people didn’t want to believe that. The population as a whole was not at all prepared for this situation, and the newspapers were very careful in writing too openly about what happened in Germany. Many of them didn’t even know, or if they knew the editors of the papers would not be very keen on writing too much about it. The policy of our country was — well, we had a very small army, and we had survived the First World War as a neutral country, arid we thought why couldn’t we do that again? Actually I also believed that we could do that again, because I could not see what could be the interest of Hitler in occupying our country. It’s much more useful to have a neutral country lying there. In the First World War, well, we had supplied Germany with foodstuff and also England as long as we could, until 1917 when the U-boat submarine war started, you know, the absolute war where they shot everything which they saw, whether it was a neutral boat or not. Then of course the food supply from Denmark to England became very very difficult. But with Germany of course there was no difficulty in getting the foodstuff down to Germany. I always thought that it would be so much more advantageous for Hitler to have a neutral Scandinavia lying there. Well, it came in another way. The situation was different. The Finnish war with Russia started something which we could not foresee, and then the plans of the French, Daladier, particularly the French who wanted to send an army through Norway to Finland and so on, which was by the way made in such a dilittantic way, it was horrible to think of. Then Hitler decided to occupy Norway and then he had of course to occupy Denmark also. So I think we were ally stunned when it happened, and nobody rea1ly believed that it should happen, because we would think that it would be much easier for Germany to fight alone on the West Front, and Poland they occupied at once, arid they had an agreement with Russia that nothing should happen there. But everything came in a different way. So we woke up one morning and the country was occupied and — there it was. We hadn’t had any preparation at all for this situation, and of course the Danish government managed to keep the Germans out of the daily life of the Danes for a long time, until they started the Jew persecutions — well, at least in October, 1943. Then of course — well, it’s not quite true. The break, the reassignment of the Danish government was already in August of 1943, and then came the persecution of Jews and this Institute was occupied in December. Until February, yes — was it until February?

Weiner:

Well, maybe January.

Moller:

I think it was in January. I think it was six weeks in all, and I think the occupation took place the 6th of December. Beethoven’s birthday, nearly. Well, politically, you know of course, all the younger physicists at that time were quite radical in their views, because we had had in the 1930s enormous unemployment, and the trade going down completely. Each country closed its frontiers and so on. It was a terrible thing. And a terrible situation for many many people, and we young students believed that something radical had to be changed, just as the people say now, but I think it was not quite so stupid as they’re saying now.

Weiner:

That’s because you’re older.

Moller:

Well, maybe. But still, one has the feeling now — well, at least we believed in some system. We thought that actually what Communism stood for was good, and that was the on1y way to get out of these constant crises which went on for seven or eight years, and nobody seemed to do anything with it, and it was terrible for many people. Then, of course, also under the influence of our friends coming from Hitler Germany and telling us what was happening there, and we had the feeling that the only real opponents to the Hitler barbarism was Communism, and we believed in that — until 1937, When I had come back from Russia, we heard about the arrest of all our colleagues in Kharkov, Landau and Leipunsky and all, and I think I already mentioned that last time. Houtermans’ wife came here, and she could tell us of the horrible things there. So after that time — and then came the Russian invasion of Finland, which of course made us see what it really was — I mean, that it was Just another type and very effective type of militarism that was going on there in Russia. But still, when I think about this period we — I also took part in some of the organization to help the refugees, and many of them were Communists, not only the physicists here. Most of them also were Communists in heart, although — well, I can say for my own, it was of course a little theoretical. We couldn’t quite see how it could work out. But on the other hand, I must say, when I took part in the elections, I never voted Communist, because I always felt that Danish Communists, they’re no good.

Weiner:

It was a general orientation toward the left.

Moller:

Yes. And also the war in Spain and the horrible things there, that we felt there was something completely wrong. But of course — well, maybe we were not so much better than these anarchists now who just throw bombs and so on. We never threw bombs, I must say. But still, well, maybe as you say, one gets older, and one has seen so much you see.

Weiner:

And the issues are different too. The issues change constantly. So it’s not just a question of a general position, because it depends what your position is on specifics, arid they’re very complex.

Moller:

Well, when I later learned about the J. Robert Oppenheimer trials and these things, then I always felt that — Oppenheimer also had sympathies with the very left, surely, when he was young, and the idea that something he had said, the views he had expressed 20 years earlier, should be of importance in a trial of today — that seems to me horrible, absolutely horrible. One should see how the man is now. Of course, he was also — it was unlucky that in one situation he lied. And for reasons which are quite, can be approved, I think, because he wanted not to bring a friend into trouble. But it was very very unlucky.

Weiner:

He ended up bringing a friend into trouble.

Moller:

Yes, he did. But he could just as well have done it at once, I think. And — well, anyhow, what I feel is that to bring up in a trial of today something a man has said 20 years ago, that is bad.

Weiner:

At that time, you give me a feeling of the general political orientation, yourself and other people. At the same time as Danes you felt Germany is not really going to do this, and even though you understood that Germany was and what Hitler stood for and were opposed to it — nevertheless it occurred. Now, getting back to the Institute, what was the thought, besides your reaction as a Dane, what about your reaction as part of the Institute, how this would affect the Institute? Was there any kind of immediate discussion that took place, official or otherwise, at the Institute regarding its fate it’s possible role?

Moller:

Well, again one felt that after all, it cannot be very important for the Germans, because after all, I mean, nothing secret has been done here, everything which has been done has been published. So again it came as a surprise when the Institute was occupied in December, 1943.

Weiner:

I mean prior to that, from 1940 to 1943?

Moller:

No. What could we do? After all, we felt completely innocent.

Weiner:

You were innocent.

Moller:

Yes. Well, in 1943 when the Institute was occupied, we were not innocent from the point of view of the Gestapo. I mean, the students made already illegal newspapers and distributed them during lectures. We knew all about that, and as a matter of fact when the Institute was occupied, there was a whole stack of illegal papers which Hans Seuss took away. I don’t know if I told you that already. Seuss was — shall we talk about this?

Weiner:

Yes, I think we’re into it right now.

Moller:

The Institute was occupied one morning, and I got a telephone call that the Institute has been occupied; you’d better stay at home. Then at that time, accidentally Seuss was on a visit — Seuss is now in America, in California, I think, a physical chemist, arid I think he was on the way to Norway. He and Hans Jensen, they sometimes traveled to Norway. What they were doing there, I don’t know, but they had some business there, and Seuss was here, and he went into the Institute. I think that was before I went into it. And as a German he could go on. And he saw a stack of these things lying there, and he took them and brought them to me and said, “I think you’d better destroy them.” Then I knew that this was not what they were interested in, because this you had all over the university and there was no reason for it. No, the instigation to this occupation came from a man who was a member of the Gestapo who had been a teacher at the German school here, even before the war, and he had become a member. He was an informer, you know, to the Germans.

Weiner:

A member of the Danish Nazi Party?

Moller:

No, he was not a member, he was a German. He was a German who was a teacher at the German school here, and that is in itself legal, but all these Germans who were there in the 1930s, they were spies. They had to write reports back to Germany. This we didn’t know then, but it’s clear that they had to do that. And he had said, “Bohr’s gone away and that is because there has been something important going on in the Institute, and so we’d better occupy it.” So the Gestapo instigated this. It was German Army troops made this occupation. Well, I stayed home a day and then I decided to go in and see what was going on here. I also had something in this desk. This is the room I had at that time.

Weiner:

This one? You’re back in the same room?

Moller:

Yes. This is the same desk. And I thought, Hans Jensen had, earlier, told me, “If you come into trouble, then you can get into contact with us, by using an Army line, and just tell this and this. You go over there and say you have an important communication to us, and in this way — There was a code to it. I thought I had this in this desk, so I thought I’d better go in and get hold of it. Also I had some precious cigars there which I wanted. Well, I went into Bohr’s office. The man in command was sitting there before I went in and asked me in a German way, in my best German, (??????). They were standing to attention. Then he mentioned the name and then I was brought in and then I said, “I am this and this and I need some of the books and some of the papers, manuscripts, for my work. Can I have it?” “Oh yes, sure, sure you can.” So he sent three so1ders with me over here to get these things. The first thing I noticed of course was they had tried to open this with the wrong key. There was a key for this, which was open, and a key for this, and this one I had in my pocket. So they had tried to open this with the other key and had not succeeded. So while they were here and they were occupied, they were much interested in some foreign stamps on letters I had, and while I was talking with them, I pulled out this and tried to look for this code. I couldn’t find it. Probably I must have taken it to another place or destroyed it; maybe I had found it was too dangerous to have it lying around. Anyhow, it was not there. But then fortunately Seuss was here, so I told him that he should tell Hans Jensen — they were both in Hamburg at that time — and that they had to do something for us, because the Institute was occupied and so and so. Well, while we were here, one of the men saw my stamps and said, “Oh, would you mind if I take this stamp?” Then I said, “Well, look here, now you have occupied the country, you have occupied the Institute, and now you ask for permission to take a stamp? Go ahead.” I talked very openly with them, and I said, “You are foolish, what are you doing here? It’s absolutely crazy to do such a thing.” Even in these days some students had been executed, and I said, “Why are you doing this? This is foolish. Can’t you see that you will get ten other students joining the resistance movement?” “Ja, Ja, das hab Ich immer gesagt, das ist nicht richtig”

Weiner:

Someone else.

Moller:

Yes. Well, anyhow, Werner Heisenberg, Jensen telephoned Heisenberg and said, “You have to go to Copenhagen.” Heisenberg first said, “I can’t do that. I can’t go up here as a member of an investigation committee into Bohr’s Institute” and so on, but Jensen convinced him that he had to do it, and he did it, and that was very good. For instance, when they came here, I was asked to come in also while they went through the whole thing. Jacobsen and I were called to go with them, and they had to look through Bohr’s correspondence and then Heisenberg said, “Oh well, Bohr’s correspondence I know. It is Just correspondence with colleagues and friends and soon.” For instance — well, they took out something, and the headship (?) took out a letter from Heisenberg. You see, here, for instance, accidentally I get a letter from me, for instance.” But some of them, there were four in the committee —

Weiner:

Were they all civilian scientists?

Moller:

There was one experimental physicist, I have forgotten his name I must admit, and there was an engineer, then there was Heisenberg and then another engineer. The most disagreeable was this engineer. He said, when he saw an instrument that was marked it was made in Leipzig or somewhere, “You see, these are coming from Germany. What are they doing here? These things are so scarce with us,” and so on, and he wanted to take the whole thing away, and he was also supposed to take the cyclotron away. Then Heisenberg said, “Well, it’s easy enough to move the cyclotron but we don’t have the people to work with it” and so on, so that was given up. Finally we got back the Institute without any conditions at all. First they wanted to place some Germans here in the Institute, and I told them at once, “Don’t do that. This will not work. Nobody of the Danes will work together with the Germans.” So finally, the final agreement, it was only said, our only obligation was to publish everything we found out during the war. Well, this we could sign because this was what we were doing anyhow. I mean we were always publishing things. So it was given back to us.

Weiner:

How long was the committee here?

Moller:

Oh, only a few days, two days, I think.

Weiner:

Did Heisenberg talk in any personal sense during that time?

Moller:

Yes. Oh yes. You know, Boggild, he was arrested when the Institute was, because he lived here, and one more — Schultz? No, the man in the workshop Olsen, I think. Or was it only Boggild? Well anyhow, Boggild was released then, and the same day — it was before Heisenberg left — we had a small party in our home to celebrate Boggild’s coming out from prison, and Heisenberg was there also. Well, you see, with Heisenberg during the war it was difficult because he probably also would have to say some things which he didn’t mean. I don’t know. Anyhow…

Weiner:

— difficult problem, that can be solved, I was just curious about the way he talked physics, for example, was concerned with that sort of thing. The last time you saw Heisenberg was on a physics basis, not on an official position, and of course it was difficult. I was curious whether you managed to talk some physics anyway.

Moller:

No, not at this time. He came — he had been here after Bohr had left, it must have been in the fall of 1943, before the occupation, and he had given a talk in the German Institute. That was something the Germans had erected after the occupation and we of course were invited to go and hear the talk of Heisenberg, and we of course did not go, and always told him — not that we didn’t want to go, but that we were not able to come. I remember clearly this last time, this happened before the war that we had been invited to this German Institute, and we were always “occupied (busy).” They wrote letters and we wrote back, “Cannot come.” But this time, they had tried to take people by surprise and called them up, and there was a girl from the German Institute who called me up and said, if we would like to come to this lecture by Professor Heisenberg? “No, thank you, I am occupied.” It came immediately. Then she said, “Oh, you are also occupied (busy)? You are also optaget (engaged)? So I got the impression that she had had many disappointments already. So we didn’t go to his lecture, but he came here and gave a small colloquium for us, for a few people.

Weiner:

At the Institute.

Moller:

Yes. Not very official. We didn’t tell to the students, so, and we were only I think six or seven people, and he was talking about the S matrix theory, and I was very much interested in that. I had just read his paper on that. That was the origin of that I started to work on the S matrix theory.

Weiner:

You were getting German journals, naturally. Did you get English journals?

Moller:

Yes. We got, for a long time at least, THE PHYSICAL REVIEW also. This I can’t remember. I think we got it all through the war.

Weiner:

Maybe there’s a way of checking to see if the library copies were stamped in on a certain date, I don’t know.

Moller:

Yes, I think it must be possible to find out.

Weiner:

It would be interesting to see if you were getting it.

Moller:

I think it came over via Sweden or somewhere, somehow.

Weiner:

Maybe Stefan Rozental would know.

Moller:

No, Rozental was not here in the last years. No, Fru Schultz would not remember, I’m afraid.

Weiner:

Let’s leave that for a point of inquiry. But I’m curious, what you said about Jensen. It meant that he had had — he was here before, during the occupation. What was he doing here?

Moller:

He was on his way to Norway always.

Weiner:

He’d come in as a scientist. Did he come in an official capacity?

Moller:

No. Well, of course, there was this — it was 1942, before Bohr went away. Here we need Rozental because his memory is better, but I only know that Bohr was very afraid of him. Bohr was very afraid of Jensen. He thought that he was a spy. Now, I knew Jensen very well from the old days and I said no, I knew that he had been a Communist before Hitler and I visited him in Hamburg in 1937 on the way to Paris, where he told me about how difficult it was for them to manage. Well, they all had to be a member of the party and so on. Can you imagine, he is a member of the Nazi Party?

Weiner:

Well, he had to if he was going to maintain his university position.

Moller:

Oh yes. Quite. Quite. And I said, “Well, I know this and I understand this.” Even at that time he was very outspoken to me. So I was convinced that he cannot in these few years have changed so completely and become a German spy. This I cannot believe. So I told Bohr this and he finally also became convinced that he was innocent. He told me little about what they had been doing in Leipzig in building up, just trying to make piles and such things, and but they had not had very much success with it. But the interesting story about Heisenberg’s visit here, you have to get Rozental to tell about that, because I’ve forgotten.

Weiner:

Well, give me the outline so I know what to ask him. I don’t know if I’ll see him on this trip.

Moller:

Heisenberg himself believes that his point of view was that he wanted to get to hear Bohr’s opinion of whether this would be a bad thing to do, or how dangerous it was, how close are we, how near are we to solving this problem of the atomic energy? And Bohr became very much afraid. He (Heisenberg) started to talk about it, and Bohr got the impression that they had been working hard on it. Now, as a matter of fact they had not. They had really not come very far at that time at least. But I’m afraid I cannot really, I don’t know how the situation was really. Rozental knows more about this.

Weiner:

Yes — well, it was very informal, we’ll get back to it, let me reserve it till then, because I think he put it in a footnote in a volume. One thing that interests me is the problem of cyclotrons in Germany. Gentner, whom I’m writing to because I’d like to see him in Heidelberg, was very much interested in cyclotrons, spent some time in Berkeley, and I think he made a trip here for the same purpose and he was in England. At least he was in Cambridge and Berkeley to learn about cyclotrons with the idea of trying to get one established in Germany. He’ll fill me in on the story. But I was really very much interested in what did happen. I don’t know how far they got, but apparently there was not a functioning cyclotron in Germany until they started a real project after the war.

Moller:

I think that’s true. Wolfgang Gentner was with Walther Bothe, yes?

Weiner:

Yes. They were in Heidelberg.

Moller:

They were in Heidelberg, yes. By the way, I saw Gentner here now in East Germany. He was at this meeting also. He is a very nice person and a very reliable man, I think, and also during the war he had contact with the French.

Weiner:

He was in Paris, yes. I’m writing to him first — I’m taking a chance, my schedule’s very tight, and I think I’ll send a letter tomorrow and telephone him next week.

Moller:

Yes. When do you plan to be there? I know he has to be in Geneva the 9th of November.

Weiner:

But you don’t have any feeling about this whole cyclotron business?

Moller:

No. I don’t know, I don’t know.

Weiner:

How much more time do you have now? Let me tell you what I have in mind. I’d like to explore the war period some more, to talk about the actual work at the Institute and how the occupation affected the work, talk about your own interests as well, and then the postwar period, whether in fact there were any discussions about the future role of the Institute in the postwar period regarding… (off tape) We talked quite a bit about the immediate circumstances of occupation and the fact that the agreement was that the Institute function in the same way except that everything be published, which is no different from what had been going on. By that time, even after — by that time the German occupation of Denmark was three years old or more, and the war had spread very widely. What effect did all this have on the ability to work, budgets and that kind of thing?

Moller:

Well, the budget went on as usual. As long as we had the Danish government, the Germans really did not interfere with these things, the university and so on. After that, when we did not have the Danish government any more, we didn’t have a government at all. But all the business, administrative business, was carried on by the civil servants in the ministries. So the money for the Institute came along as it had. There was no increase of course, but everything worked smoothly in this way, and strangely enough, this feeling of being closed in made you concentrate on your work. I mean, you were not disturbed by any administrative things and so on. Well, if you had the ability to look away from everything that happened in the world and also what happened in the later years in this country, in the last years of the war, then you could work all right. I wrote a paper on general relativity, and the clock paradox, which foolishly enough takes up so much paper still in the journals. I mean, it’s a rather trivial problem, but it seems that every generation has to tackle this problem anew. And then I came into this S matrix thing and worked on that for the last two years of the war. So of course, for Bohr, he knew more than I did, and I could feel that he was, the last year he was here he grew restless and worried, and more and more worried.

Weiner:

He knew more of what, the world situation?

Moller:

Well, I think he had a feeling that this could not go on with the Institute, and with this atomic energy business coming up, and also the conversations with Heisenberg and so on I think made him feel that there was something, a danger pending. At least, I know one day he came in and I was sitting working and he said, “Oh, it must be beautifu1 to sit down quietly as you do now.” I mean, he was restless the last year, the last half year.

Weiner:

You get the impression that this started in the ‘30s, that already there was a kind of a preoccupation with world affairs.

Moller:

Well, yes, maybe, but still it did not have any influence on his work.

Weiner:

Not at all, no. I gathered from Margrethe Bohr and from Aage Bohr that his interests — well, the refugees, he was into that actively, but also, his 1939 trip to Cambridge, that this was the thing that seemed to concern him more than anything else, the whole war. To me it seems a natural consequence of his philosophical outlook.

Moller:

Oh yes. Yes.

Weiner:

I notice these publications were published in the Academy Journal and I don’t know what this Journal Videnskaben Idag — what is that?

Moller:

Oh yes, that is a popular, that was a popular series for scientific articles on many subjects, many different subjects, not only physics but biology and so on, and was written by a number of scientists during the war. Yes, that was written after.

Weiner:

That’s the first time I’ve seen that publication listed. I’ve seen the others but not that.

Moller:

This was written after Bohr had left, and actually, while the Institute was occupied and we were in the Polytecknisk Lareanstat while — for six weeks while the Institute was occupied. We had some rooms over in the old Technical High School.

Weiner:

Even that didn’t interrupt your work. You continued there.

Moller:

Yes.

Weiner:

But there weren’t many publications in the period and they were all, I noticed in Danish — the few publications, yours were in the Danish Academy. Were you able to distribute reprints of those to other people?

Moller:

No. No, we couldn’t

Weiner:

Could you have sent something to, would it have been possible or sensible to send something to an English or American journal?

Moller:

No, I don’t think so. I don’t think it would have been possible, no. No, in the last years of the war — well, I was in Sweden two times during the war, but from 1942 on, it was not possible any more. Then you could only go illegally to Sweden. But I didn’t do that. I often had contact with people who went to Sweden and back again as couriers, and I also had, once, must have been in 1944, a man appeared in our house. I had not yet come home from the Institute and my wife was alone with our children, and it was a time when it was not advisable to let any strange people in so she said, “My husband is not at home. If you want to talk to him, you have to come again.” And she was about to close the door and then he said, “Well, I can give you my card and show you my identity card, but I must tell you that it is false, and I do not look like I do now, so you wouldn’t recognize me, but my real name is Professor Husfeldt.” He was a member of the resistance board even. This we did not know of course, until, after the war, and he had just been in Sweden and he had got a letter for me, microfilmed letter, and — well, he went on talking with my wife and finally she got so much confidence in him that she accepted the thing he brought. It was a cigarette case. “And if something should happen before your husband comes home, you just have to open it and tear off the back side of it. There is a film in there which will be destroyed as soon as it comes to light.” Well, I came home then after he had left and she told me about this, and I went immediately to the Institute and asked Boggild to help me to develop this film, so we could see what it was, and it was clearly a letter from Bohr although it was not signed by Bohr, but we could recognize the style very easily.

Weiner:

Typewritten or handwritten?

Moller:

Typewritten. He asked about, if we knew where our German friends were at the moment, in which place they were. We didn’t know that so we couldn’t give much information. Only after our answer had been sent off —

Weiner:

— how did the answer go?

Moller:

Well, this man had said to my wife, “I will call tomorrow, at a particular time, if your husband will be there.” So I waited for this call, and then he told me that if I had seen the letter — yes — and if there was any answer. I said yes, and then he said, “I will walk along Osterbrogade at this time and if you walk along, I will get the letter. When we pass I can get the letter.” So we made this answer, telling that we didn’t know anything, and — but he also had said, that if we needed to come into contact with him at a later time, we could call this and this place. It was not his place. It was another person. In the meantime, Jensen had been here and he had told us where they were, that they were now in Hechinger and they had — were — the Kaiser Wilhelm Gesellschaft had been bombed completely, so they were in Hechinger, in the south of Germany, and so I called up this man again and said, “I have now a little more information,” so at that time he asked me to meet him Osterport Station, to go down to this and this train, and so it was exchanged in the same way, just passed each other. Of course, before I did anything, before I answered anything — it could have been a provocation somehow you know, so I tried to find out that, if it was likely that Professor Husfeldt was doing these things. I didn’t know him before. As he said, I wouldn’t recognize him. His identity card was Architect Jensen” and his hair was red, and he had a red moustache. So I went to Chievitz, who was also a member of the resistance board, which we did not know either, but we knew that he was — he had been, well, he had actually been arrested by the Germans, this we knew. So I knew that he had something to do with these things. So I went to Chievitz and asked him if he knew where Husfeldt was. He said, “No, we never know where we are.” I asked him if it was likely that he had been in Sweden this and this day. As a matter of fact, he told us that he had come by a fishing boat. He had been lying the whole day in the bottom of the fishing boat in the harbor of — the nearest point to our home, the waterfront. And Chievitz said, “Yes, I seem to remember, it can be possible.” One had to be very careful of course. It could just be a provocation, the letter. Well, Chievitz, sometimes I met him in the street. Then he walked past me, just like that, never talked to each other.

Weiner:

Where was Bohr when this letter was sent?

Moller:

I never found out. I think he was still in England.

Weiner:

This was still 1944.

Moller:

1944, I think — could it be the spring of 1944? We did not know, of course, but he had left Sweden rather early after he came to Sweden, and came to England, and I had the impression it was through the British Secret Service that this letter had been. Oh yes, there was one thing more, oh yes. Husfeldt contacted me and told me at one time that the first letter had never arrived, so please write the same again. I said, “Well, it’s not very useful, because now I know more.”

Weiner:

Did you ever find out if it was received?

Moller:

Well, you see, it was so strange. When I saw Bohr for the first time after the war, I asked him about it, and he was so afraid of saying anything, so he said, “Well, we shall talk about that later.” But I had the impression that he had got this letter. But I never found out really if he received it or not.

Weiner:

There’s an interesting book written now on the German bomb project by David Irving I think who extended what Goudsmit did quite a bit, using official records in the German and US archives. I might refer to that, maybe there’s something in there. During the period after Bohr left, was there any — anyone with the specific responsibility for the entire Institute?

Moller:

Well, Jacobsen and I, we signed all the papers, contact with the ministry, I mean for the budget and such things.

Weiner:

There was no title to go with it. That would be admitting that Bohr wasn’t —

Moller:

— no, no, it was simply done.

Weiner:

What official explanation did the Institute give for Bohr’s absence?

Moller:

No explanation. Nobody asked. He wasn’t here. I mean, it was rather obvious. After all, he was half Jewish. His mother was Jewish. So it would have been — well, although, maybe nothing would have happened to him, because for instance even Erik Warburg, who was a professor here, he was completely Jewish. His wife was English, not Jewish. And he was not touched. But Dr. Werner Best, the rigsbefulamagtigelde, as he was called, he had once consulted him, and Warburg, a very outspoken man, had certainly not hidden his — I mean, he had not tried to hide that he was Jewish. It was also rather obvious when you saw him. But nothing happened to him, strangely enough.

Weiner:

In Bohr’s case, I haven’t seen the documents, it was stated that there was an order f or his arrest, or a rumor of an order.

Moller:

Probably not for Aryan reasons.

Weiner:

No, to bring him to Germany, and that the time to do this was at the time of the arrest of the Jews so it would be unnoticed in Denmark in general.

Moller:

Yes, that is quite possible.

Weiner:

Well, as to the work at the Institute during the period, you pointed out that contacts were limited. The budget, I know, you said it went on, but Rockefeller money was paid by the Carlsberg I know till the end of the war, then paid back. What about the buying of things, equipment and things needed in experimental work? I imagine this would be in short supply, that’s the point.

Moller:

Well, at the beginning of the war in 1941 the university sent out to the Institute a request to look into what instruments we needed and would need in the near future, because there had been an agreement with the Germans that some of the money which they owed to the National Bank— I mean, all the foodstuff which was exported to Germany was never paid, it was simply reckoned as a debt in the National Bank, and some of this money we could get back in this way, and we bought a lot of instruments, smaller things but still things that were very useful to have. And by the way, that was one of the — the store of this, we had bought more than we actually used — the store of this was one of the things that this German engineer, he saw this — “Oh, it’s coming from Germany,” so he wanted to take the whole thing back.

Weiner:

Wasn’t there a requirement in that case that could be German goods that were purchased — in other words, to make sense of this, any equipment would have to be German made in order to get the financial transaction taken care of.

Moller:

Oh yes. German goods.

Weiner:

They were still making scientific equipment.

Moller:

Yes — at that time, at least. It was in 1941, rather early in the war. They probably had more than they could use themselves. But in 1943 already it obviously had changed because this engineer wanted to take it back.

Weiner:

Yes. Also they might have been involved in this specific project. It seems to me that the whole war period resulted in certain changes here in experimental facilities being increased. The Van de Graaff was built, wasn’t it, during the war?

Moller:

When was the first Van de Graaff built?

Weiner:

I thought that there were a couple of things completed here.

Moller:

Yes yes, oh yes, that’s right, because, oh yes, yes, yes. During the period when we were out from the Institute, when we were exiled and had some rooms over in the old Technical High School, Brostrom, who was building the Van de Graaff he built a small one, a model of the thing, which gave very nice sparks. It was exactly the same principle, you know.

Weiner:

Robert Van de Graaff’s first one was not more than that.

Moller:

Right. I think he just did that to have something to do while he was there. We didn’t know when we would come back. Now, probably you are right, that it was finished during the war.

Weiner:

Rozental mentioned, that one result of the war was a real tooling up in terms of completing some data and instruments.

Moller:

Yes.

Weiner:

Well, I noticed in the publication list during the war, it was much reduced of course because the staff for one thing was reduced. In the preceding years the large output was the biological output, and Hevesy’s gone, and I can understand there would be limited amounts of staff and students. What about teaching, did that continue as before?

Moller:

The teaching more or less continued. There were very few students at that time. During the 1930s, during the depression, the number of students had been decreasing; because there was so much unemployment, also the schools, for teachers it was difficult to get jobs and so on. As soon as something stops, if you do not have continuous expansion, then the counter-flow sets in. It’s a process which is self-accelerating. So — but when the resistance movement started to become more effective, many of the students took part of course first of all in writing legal papers, getting the news and to write papers. There were many many papers.

Weiner:

I saw them at the Resistance Museum, a proliferation.

Moller:

Yes. And these were mostly students who did this. Some of them also went actively into sabotage and so on. Then there were, from the German side, reprisals of course with the students. Studenterforeningen’s hus was bombed and sometimes it was recommended the students should not appear at the lectures and so on, because it was too dangerous, because then the Germans could get hold of them and so on. And at one time, I went to a school, the Osterborgerdyd School which is close to the station, and talked to the rector, and said if it should be impossible for our students to come here, if we could use some of the classrooms here. I had an agreement with him. But it never became necessary actually. After the Institute had been occupied, we always said, “This is the safest place in Copenhagen, because they will not make this mistake once more, to come here.” Because it had been a fiasco, and we even heard that this man, Dr. (???) — the man I mentioned who had been a teacher in the German school — that he had got a reprimand from his boss, that he had started this thing without any reason, because they really didn’t get anything out of it. So we really always had this Institute as a very safe place, and we never had any trouble after that. So the students came here, and continued their work of distributing illegal papers and so on. Then, only at the end of the war in 1945, when a hundred thousand or perhaps two hundred thousand German refugees from the Eastern provinces, when the Russians swept over the eastern part of Germany, they were transported to Copenhagen and put into camps here. Then they took a lot of schools and they also took again — they took the school in Ryesgade for the refugees so that they could have a place to sleep, and then the children had to have another place to go to school, so they went to school in the building where the offices are now, what they usually called the Villa.

Weiner:

Where the Arkiver kept.

Moller:

Exactly. It was transformed into school classrooms. That was at the end of the war, in the spring of 1945. Well, you know, these refugees, it took a long time before we got rid of them, a year or two because in Germany they had no place. They had already so many in Western Germany.

Weiner:

Getting back to these classes, the number of students for all of the various reasons would be less.

Moller:

Yes.

Weiner:

But basically the routines at the Institute were the same?

Moller:

They were the same.

Weiner:

I can understand that in lectures, but how about colloquia, seminars?

Moller:

Well, we also tried to have colloquia but not so often.

Weiner:

Well, you didn’t get many foreign journals.

Moller:

No. As a whole — I mean, also the things which were published were rather few, even in your country. Most of it was secret work and so on.

Weiner:

Sure. Well, there was censorship on anything that could be related to war work, and then a lot of people were doing war work so they weren’t publishing in physics.

Moller:

Yes, quite. We kept up — certainly — a colloquium for the students. That was a part of their education. This we did, and well, when Jensen came or Heisenberg came, we had small colloquia. But it’s true, the activity was very reduced, that’s true. But if you loved to sit at a desk and think, it was not such a bad time, strangely enough.

Weiner:

No, I can understand that. It’s true even with experimental people, in the Rome group, in its most productive period for neutron work, the outside pressures of society — you know, they were getting away from that. They were able to develop themselves night and day, and they called it “work as soma” in the Huxley sense of the word, soma, as escape, a drug and so forth.

Moller:

Yes, sure, there was very much of that. I mean, that was the only way you really could stand the pressure. The last year was a very difficult year because when the sabotage went on — I mean, it was the last year that we had every night sabotage, 7 o’clock. During the winter of 1944-1945 you could put your clock by it. It was always a definite time after the workers had left the factories. Then we would hear, Bang! Then the reprisals started, of course, where they obviously just took a telephone book and chose people who should be shot. And then they went to the door and pushed the first bell, and simply shot the first man who appeared. There were many reprisals which were completely un-understandable, people who had done nothing. They were completely innocent. And this creates of course a very uncertain atmosphere, but also a kind of fatalism, you know, because when it is so accidental, well, you cannot do anything against it. You just have to live through it.

Weiner:

When liberation occurred — was it May 5th?

Moller:

May 4th. Officially it was actually the 5th, but on the 4th we got the radio news from the BBC.

Weiner:

I don’t know what effect that has. How long was it before Bohr got back to the Institute?

Moller:

Oh, that was — he came in the fall of 1945. Was it September?

Weiner:

There are accounts of a little bit of this, but I’m concerned, as probably our final point of discussion (otherwise we’re off into a new period and it’s getting late), whether there were any discussions now about what happens in the Institute, what do we do?

Moller:

Well, I think, first of all, the financial situation was bad in the country, and Bohr had the impression that we could not take part in atomic energy development and such things for some future. It was not something we should concentrate on now, it was too expensive and so on. So the first years, we — well, what happened, the buildings over there were built, but that was not before — you probably have the dates better, the big building over there was in — not before, I think it was not before I came back from United States. I was in Lafayette, Purdue University, ‘48, ‘49, the fall of ‘48, and I came back in the spring of ‘49, and I think it was just after that, that this building came up.

Weiner:

They started trying to raise money as soon as 1946.

Moller:

That may be, but I think it took a long time before it became effective, yes. Well, maybe Bohr had it in his mind as soon as he came back, that he wanted to enlarge the Institute, but I know that he was — the Riso business came much later, at least, because he thought it was not something we could concentrate on, because we didn’t have the manpower.

Weiner:

Did he identify a specific role of the Institute? Was it pretty much the same orientation as the pre-war period?

Moller:

I had the impression that we should just try to go on. And again, of course, endeavor to get foreign visitors and so on and it should be the place where international cooperation — and it started rather early that we had a lot of foreign visitors. Not so many as now. Then of course over the period — well, you mentioned the CERN thing, the theoretical division of CERN, which started in 1952, I think, and lasted until 1957. This of course — well, this was, you know that it was organized in this way, that each CERN member country sent some young people up to take part in the theoretical work and we had quite a number of very bright young men here at that time, who later got big positions. We had Kallen here. He was a genius, really very bright. We had van Hove and Waldhausen and from Germany we had Luders and — well, these are the ones I remember at the moment who have done very good work later.

Weiner:

That’s a separate story I’d like to get another time.

Moller:

Yes, when you come again we can continue that.

Weiner:

I’d really like to talk about that and the origins of Nordita. As a matter of fact, this is a good time for you to review the past development of Nordita, and even if it doesn’t go into my immediate project, if you’re willing I’d like to explore that. You can get it on the record while it’s still fresh in your mind.

Moller:

Surely, I can do that.

Weiner:

I think this takes me to — 1946 I guess was the 25th anniversary of the opening of the Institute. Maybe that’s the meeting that Pais and others referred to, where collaborators were invited, and there is an account I think in the Rozental volume of something about that meeting.

Moller:

Yes, there is.

Weiner:

But we might as well leave all of that for the future because I don’t have any documents which would give me an idea. Maybe I should start looking for those, my next time around.

Moller:

Yes. Yes.

Weiner:

For now — one thing, just to ask, to give me an idea for the future, when was the first time you went abroad after the war?

Moller:

After the war, that was in the fall of 1945, my wife and I went to Stockholm. That was really the first time we came out, which was marvelous journey because everything looked so rosy, you see, after the dark years, and we met old friends in Stockholm. We had a marvelous time, could buy a lot of things which we had not had for a long time, particularly cigars and such things. No, it was very nice to meet Klein again, and the weather was so wonderful. Stockholm looked at its best. We had a beautiful concert in the concert hall. It was a really marvelous trip. It was more — it was not so much professional, just to see old friends and so on. I may also have given a talk. I think I gave a talk in Stockholm. Then, the next time I went to Bristol in February 1946. I gave some lectures on the S matrix theory.

Weiner:

Was Rozental in Bristol?

Moller:

No, he was in Manchester that year. Mott was at the Cavendish Laboratory then.

Weiner:

He just retired from his position too, at the Cavendish.

Moller:

He did? Well, there, I met again — I met Cecil Powell there for the first time, of course, not in Dublin.

Weiner:

Giuseppe Occhialini must have been there.

Moller:

Occhialini was there, yes. He always tried to persuade me to go caving with him. I always refused.

Weiner:

That’s a passion with him.

Moller:

Yes. But he had an excellent — at one time, I think he has stopped now caving.

Weiner:

He still goes mountain climbing.

Moller:

Mountain climbing, yes, that is the other way — the same type of madness, of course, mountain climbing is also. And I saw Jim Hamilton for the first time, who now came to us some years ago. And I went to — on the way back, I gave a talk in the Royal Society also, one of these open meetings, and then I went to visit Rudolf Peierls in Manchester.

Weiner:

Peierls you had known from here?

Moller:

Yes Peierls I had known from very early, when I was a student here, 1929, I think he was here. I met him at a party at Bohr’s house, over at “the Villa” where Bohrs lived then.

Weiner:

He would still have been in Munich.

Moller:

Berlin, I think.

Weiner:

Well, he was a Sommerfeld student in Munich and then he — I think so — went on a fellowship.

Moller:

He was born in Berlin, I think. Well, anyhow, I always had the impression he came from Berlin, but maybe —

Weiner:

He and Bethe were at Munich together essentially. Both did exactly the same thing as you did. They took a fe1lowship and went to Rome and Cambridge. He did it in 1930 and I think Bethe did it in 1931, 1932, something like that. So you were right on the same circuit. Anyway, about this immediate postwar period, I think that’s another subject but I would like to get into it because I’m going to talk again with Occhialini for example about the whole Bristol period and have discussions with him up to that point, and I talked with Peierls about that whole period. I’m not prepared now to even think through the proper things that I really want to know, so maybe we can defer that. Well, I think that really does it for now.

Moller:

Good.

Weiner:

And thank you!