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Interview of Guido Beck by John Heilbron on 1967 April 22,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Involvement in the history of quantum physics and nuclear physics; thoughts on physics institutions in underdeveloped countries. Studies at University of Vienna in the early 1920s; his work at Felix Ehrenhaft's Institute until 1928; subsequent assistantship with Werner Heisenberg at University of Leipzig for four years. Conversations with Heisenberg about electrons in the nucleus; origins of Beck's interest in nuclear physics after hearing Francis W. Ashton's paper on mass defect at the 1927 Volta Conference; conferences at University of Copenhagen including 1932, where, before the positron was discovered, everyone was making fun of Paul A. M. Dirac's "holes." Theory of beta decay, inability to continue work on it due to lack of additional data when going to Kansas in 1934 and Odessa in 1935. Leaves Odessa; internment in France during the war; escape to Portugal and arrives in Argentina. Also prominently mentioned are: M. Besso, Niels Bohr, Albert Einstein, Wolfgang Pauli, Ernest Rutherford, Erwin Schrodinger, Adolf Smekal, Hans Thirring, Joseph J. Thomson, Victor F. Weisskopf, and Hideki Yukawa.
The problem is more general because if you think of countries like European countries or the States where people are convinced that they have to make science, it is one thing; but if you go to new and developing countries, there is still resistance. Then the whole thing needs a different basis because it needs not only knowledge of what the scientist does but also how the environment reacts. And that has become important since they have set up these development plans in the United Nations, in UNESCO, in the International Atomic Energy Agency and so on. This has to be studied, and we are learning it very slowly.
How are things in South America?
The situation in the institutions is this: there is no stability. You know what happened in Buenos Aires lately. There has been lots of trouble in Argentina at the University. It just doesn’t fit together. The government moves, they say, to eliminate politics from the University. It’s of course necessary because the University there is a political institution and not a scientific institution. I think the government was quite sincere about it. Only it turns out in the long run that it has not become depolitized but repolitized in a different sense. The people do not have enough experience and more scientists have resigned in Buenos Aires. That was a political move and nothing has been gained with it, only promising work has been destroyed.
Is Brazil affected at all?
No. It started in Brasilia and in our Institute there in Rio. In the Centro Brasileiro de Pesquisas Fisicas, the Institute was running all right. To form an institute takes tens years of work... You cannot start it in a fortnight. They take away the money and start putting somebody in charge who doesn’t understand anything and everybody on the staff leaves. Now, they have to collect them again... My Brazilian students are around here in the States. They have fine positions, but they are here.
Do any of them stay on down in Brazil?
There are a few. They are still connected with the Institute, but there are only two or three who have stayed. If they want to live and to work, then they have to go abroad.
Could we start at the beginning of your long series of moves? You were born in Bohemia.
Bohemia. Last night I put down some details. That’s about it. [He hands over a sheet of notes].
Thank you. Where did you go to gymnasium?
In Switzerland. My family was living in Switzerland. I didn’t complete it in Switzerland because my family moved in 1920 to Vienna, and so I got my bachelor’s degree in Vienna.
I see. You really didn’t live then in Bohemia for long?
I lived in Bohemia for the first four years of my life; then my family moved to Switzerland.
What called your family there?
Oh, the business of my father.
He was in commerce. He was the director of an English firm in Zürich.
Were you originally intended for that same business?
No, not particularly. The family of my mother was in textile manufacturing for a long time, for a century, and so the family of my mother wanted me to go somehow into industry. Nobody believed in physics at that time. Only my father helped me.
When did you develop an interest in physics?
Oh, it was about in college — the gymnasium period — when I was about 15 years old. I got these small booklets of Einstein. There was lots of talk about relativity.
You began with really a kind of popular version of relativity and then quickly worked up...?
Oh, there was a half popular book of Einstein where he just outlined [the theory] that I got. But I had been interested in mathematics before looking [at it].
So your first paper, this one on the gravitational theory, though that came of course much later, was a development of this first interest?
Well, I came to Vienna, where there was Hans Thirring, and he had been working [on relativity]. So I’d been interested in relativity, and most [of] what I did after I learned the first things was to take the book of Hermann Weyl — my bible at that time was the Hermann Weyl book — and tried to do something myself.
Were there many people there studying relativity with Thirring?
There was not a school in that sense. He had about 120 students in his course. He gave a very fine course, but that included everybody in [baccalaureate physics] studies. There were a few high school teachers that were there; chemists came there who wanted to see a little bit; then there were the experimental physicists. Vienna at that time had an output of about one theoretical physicist per year. So I had only one colleague who was simultaneously with me, who is now in England — H. Peltzer.... There were always two or three around but they did different things. There was no concentration on one subject.
I’ve often wondered how the institutes were arranged — there were two or three physical institutions at the University there?
No, we had lots. At the first institute, there was old Lecher who was their professor for many years. I don’t know whether you know his work — it was about wires and the Maxwell theory. Then they made a second institute. The head of it was Jager, a former assistant of Boltzmann. And then Ehrenhaft managed in 1918 that they set up a third institute, an experimental institute. But Jager, as a matter of fact, though he had experimental work in his institute, was a theoretician. He tried to extend the kinetic theory of gases to liquids, something that didn’t work very well. But they had good people there in the institutes. And then there was the Padium Institute. That has been important because Hevesy had been there and Lise Meitner had started there and Stephan Meyer was there heading it. And he was a very well-considered physicist.
How were the theoreticians organized then?
There was a theoretical institute — that was Hans Thirring — and now his son has taken over. And then there were chairs at the other universities. Vienna had lots of them. For agriculture there was Haschek, who also had come out of the University. He was teaching a physics course at the agricultural school. He was in charge, for instance, of the laboratory work for students at the University. And then there were people of what you would call the engineering school. Technische Hochschule. And that was a very good school; it had its independent physics [group]. There was Mache in experimental physics, and there was Flamm, who was the son-in-law of Boltzmann, who had the chair. In general, the center was the university. That means that it was fashionable for a professor of the Technische Hochschule to be Privatdozent at the University, though by title, he was a full professor. But this gave him the right to teach at the university and make a connection.
If he were a professor elsewhere, he could still be Privatdozent at the University?
It was an independent thing. Everybody could be a Privatdozent. In general, they did it just to show their devotion — to be connected, you see, with the university which was considered to be the center of scientific activity. As a matter of fact, Vienna had a great tradition, but since the death of Hasenohrl, there has been no one outstanding. The first one who has made an international name and set up an institute is Walter Thirring, Hans Thirring’s son. He is now in charge, and in three years he has formed a splendid group. He can’t keep it together because he has sold out, but that remains physicists’ fate [laughter].
Were there then seminars and colloquia at the university to which the people from surrounding schools would come?
Well, we had several regular meetings. For teaching Hans Thirring made a pro-seminar that was just for students. There you had to get your first medals and to give a lecture after the terms. For the work I did for my first pro-seminar, I got the right to use the library. I would not have gotten it otherwise.
What sort of exercise did you have to do there?
Oh, I remember he was lecturing about optics and he showed a Michelson plate grating [Stufengitter]. Well, I calculated the Kirchoff integral and showed that it leads in the limit to the refraction law. A simple problem just to show that I could work with these things.
Did you do that after you had been at the University for a few years?
After two years at the University, that’s all.
And you then had how much physics?
In the first year, I had experimental physics — that was Lecher’s general course — just to see what it is, to see the basic experiments. And then in the second year, I had Thirring’s lecture, but for physicists he had a four year course.
Yes, a cycle. And there you came in where you happened to. I started with electrodynamics and had a hard time, but I managed to come through, and then after the first year, I could already walk around a little bit. Then I went to the library. The result was pretty poor because I took all the books out and then brought them to my house and it was lots of trouble.
What was the journal situation like? Could one get foreign journals?
The library was good.
Without any trouble?
Well, the situation was that there was very much less than now, you see. What we used to read was the Zeitschrift fur Physik and the Physikalische Zeitschrift of Debye, and the Annalen der Physik. These were the three papers. Of course, we had the Proceedings of the Royal Society, the Comptes rendus, the Journal de Physique, and Physical Review. But they were consulted very little; we looked at them occasionally. There were no Italian papers. We didn’t look too much at foreign papers. Let’s say there were the Swedish Archiv, and so on, but we looked at these things if we found some citations or such. The main things were the Zeitschrift fur Physik and the Annalen der Physik and the Physikalische Zeitschrift. So that was fairly easy and in Vienna, there was never any trouble, as the library was good.
Even shortly after the war?
Well, I started in 1921 after the First World War. At the time when I started looking at the Library — they let me do that in 1922 — they had a complete collection of the foreign literature after the First World War, so these things were not difficult at that time.
When in your training would you start reading in the periodical literature?
It must have been when I started to make my thesis around the last year of my studies.
What other seminars were there? There was the one in which you taught, so to speak, and then.....?
In the colloquium, that was all physics together. We did not meet frequently because the young people from the other schools didn’t come there too often on Mondays. But on Tuesdays, there was the Chemisch-Physikalische Gesellschaft which was the weekly meeting and everybody came there. Sometimes there were talks on chemistry and not everybody came, but there was more physics than chemistry. If there was something important to tell, they told it there.
Was it mostly guests or people within the university who gave the talks?
Mostly people from the university, though there were people, for instance, who visited. For example, I spoke there frequently, when I came from Prague and had something new to tell. But now, the situation has become disorganized because there are lots of visitors in Vienna; one just announces two days or so before the seminars, and that makes it had: “The gentleman will be there on that day.” There is no regular colloquium. Once when I spent six months in Vienna, I tried to set the old colloquium up again; while I was there it worked. As soon as I had gone, it became irregular again.
Everybody considered it valuable in the older times, in the 1920s?
We were used to it. On Monday, one went to the colloquium. On Tuesday, you went to the Chemisch-Physikalische Gesellschaft.
Did you take any of Smekal’s courses?
Smekal was teaching one course in Hamiltonian mechanics, and so I tried to go there, but most people went away. His lectures were not very inspiring.
What was the trouble?
At the end, he had just one student. Well, the trouble was his lectures were not very physical, just very intuitive; he showed just mathematics. Of course, he did it because of the Hamiltonian mechanics that Sommerfeld used, so it was necessary. As a matter of fact, during the time I studied in Vienna, at least you knew it existed, but you didn’t know why you should use it.
The Hamilton-Jacoby approach?
The Hamilton-Jacoby equation, the whole Hamilton approach to mechanics. We just looked at it as a mathematical curiosity. It was only after Schrödinger’s paper came out that we saw it was a general thing. Then I started to study Hamiltonian mechanics.
What about Smekal’s other courses — the ones on atom models and so on? No one took those either?
I didn’t — I had no chance to look at them. I don’t think he gave them every year. But I know what Smekal did in those years at the Technische Hochschule; he convinced people to make a course of Technische Physik that didn’t exist before. And that was a tremendous success. There were not many people — may ten or fifteen or twenty or something like that, who went there. But the amazing thing was that, in those days — electronics started to develop, for instance — they needed physicists. And in Vienna we had the maximum of the world crisis, the Depression in the 1930s and even in the worst years it never happened that the school had not been sold out before the people were through. It was the only place in Vienna where one could learn such things which meant many more people came, of course. And so it turned out like that, although I don’t think that it was a very first-class school.
But useful, I would say, even though it was not absolutely up-to-date, and probably people there didn’t learn the last developments of how things were done in the States. In industry, Germany was the center and they may have been more advanced than Austria. But still what they could give them there was enormously useful. There were no technical physicists around since nobody knew that you needed technical physicists. I think that was a great merit of Smekal’s.
It seems surprising from the little one knows of him that he would be the moving force for such an institution, because he was so mathematically inclined. Who else then taught the Bohr theory — the quantum theory — if one didn’t listen to Smekal?
Well, it was in Hans Thirring’s course.
He did that as well in the four-year course?
In the four-year cycle, he took up modern physics, which was essentially the Bohr Model and Sommerfeld’s. But we didn’t get very much out of it. Of course, we had the atom Bible of Sommerfeld which everybody was looking at. We needed something else.
But you yourself attended mainly to relativity theory at that point in 1924 and 1925?
No. I started with electrodynamics at that time because I had no basis of it. The mechanics course I think I never listened to; I just looked at what I needed. And then we came to the modern courses. Within the last two years, I was working mainly on my thesis. In general, people didn’t go to courses any anymore when working on their thesis — you were sitting around in the institute going to seminars and studying by yourself.
And the usual time was what? Would you have your thesis four or five years after you entered the gymnasium?
In Vienna we had a four year requirement and you could get your PhD in the last term. I had written my thesis in the beginning of the fourth year, during the seventh term, and so I turned it in. After three and a half years of studies, I was practically through. Then at the end of the term, I was admitted to my exams and got my PhD.
Was it the paper on relativity?
That was the paper on relativity.
But almost immediately after that, you were writing on the Compton effect?
Yes. There was an assistant of Hans Thirring, Otto Halpern, who has been here in the States. Halpern was working, and I was on close terms with him, on the Compton effect. So I tried to contribute to that work on the Compton effect, and I got interested in the radiation damping, and then later in the photo effect, when the Schrödinger equation came.
I was quite interested in that paper on the Compton effect. I read it yesterday.
The quantization of the old classical movement?
Yes. I not only was interested in that but in your conclusion. I wondered what the status of the light-quantum hypothesis was. How did Thirring represent it, for example? You conclude against it, or you would like to conclude against it, in this paper.
I believed in the classical picture. There was no quantum mechanics at that time or at least I didn’t know it. Halpern had just calculated the acceleration of the electron, the motion of an electron in a periodic field. There is a motion that you have to quantize. Since it is a periodic motion, I put these integrals in. Then I got the velocity, and thought the velocity was the average.
Yes, it fitted very nicely.
But it was wrong.
It was wrong, yes. When you submitted that paper, were you an assistant at Vienna?
I finished in July and then I couldn’t find any job. I got a job at the end of the year for the next year — in January — at the University of Bern just because a friend of mine sent me an advertisement cut from a Swiss newspaper. So I wrote there and I got a job. It was quite hard to get jobs at that time.
Would you submit directly to the Zeitschrift fur Physik?
One sent directly to Scheel.
One didn’t submit through a professor at all?
If you were in an institute, then you were supposed to show it to the head of the department or so for an okay. But in general, people didn’t care very much. They took the responsibility themselves.
Was it refereed at that point?
No. Though, of course, Scheel had the right as the editor, but practically there was no control at that time.
What sort of reaction did you get to that paper — any at all?
No, there was a little bit of quarreling with Halpern. And then I told Heisenberg once, and he told me, “Well, if you put h in, something will come out.”
What kind of a place was Bern after Vienna?
Well, it was very quiet — very much less was happening. Greinacher, a good experimental physicist, was there. What was interesting in Bern was that I met Besso. Then there was a good mathematician Gonseth who was very much interested in these questions. (Later he was a success with Hermann Weyl when he got to the Technische Hochschule, the Polytechnicum in Zürich.) So we made a private seminar. There was Besso, who had letters from Einstein; he was always in touch with Einstein. You know who Besso was? He was the “Resonanzboden” of Einstein in the critical year, 1905; he was in his office.... Einstein quotes him in his famous paper in 1905. Have you ever seen that?
I guess I haven’t.
You take Einstein’s original paper on relativity in 1905 “Zur Elektrodynamik bewegter Körper” in the Annals of Physics. The last sentence is: “At the end I want to stress during all the work, my friend, M. Bess, has been faithfully by my side.” So what happened to Einstein; he had a job at the patent office in Switzerland at that time, and there were two desks in the room. One was Einstein’s. The other was Besso’s. Einstein always came in excited. He didn’t care too much about his patents. He was concerned about Lorentz’ electrodynamics. And the men in the office started talking and Besso was listening and putting questions, so Einstein called him the best “Resonanzboden” that he ever found. And Besso was very proud of that. And from then, he was a personal close friend of Einstein.
When you began to work in quantum theory more than you had, what sort of things did you find you had to read, if anything?
First I tried to understand Heisenberg’s paper — to find out about the famous paper of Heisenberg’s on the uncertainty principle. There was the gamma ray microscope. But really, I got closer to the things only when we got the Schrodinger equation.
You did immediately try those papers of Heisenberg and Born and Jordan before Schrodinger?
Yes, we got them, and there was Lenz from Hamburg who came once and gave a talk in a colloquium, I think it was. And he was talking about the Heisenberg paper, but he couldn’t explain it too well. It was very abstract and we didn’t understand why a coordinate should suddenly be a matrix, we didn’t know very well what it was. Just by working up to it, you could find out what it meant.
Did people think it was an answer, though?
At that time, we didn’t believe it.
You didn’t believe it?
We were lacking many elements, you see, because the Kramers-Heisenberg work was the basis of that. I read that with interest much later. So if I had known this paper, the reasoning of Bohr at that time, I would have been much closer to the questions. The second thing is that I found out later what I was lacking was that I practically did not participate at all in the Zeeman effect, the normal Zeeman effect, and all these difficulties. There was a lot of talk about multiples and the splitting of lines by magnetic fields and so on. But I never studied them or understood them. In that I was lacking. I knew there was all this terminology I had to learn about coupling of orbits and spins and so on.
Was there anyone in Vienna who was up on those things?
I had the impression that nobody was working on these things, unless some visitor came. Pauli came from Hamburg and was talking to people about just what I was interested in. You know when you study you are interested in one point first; you want to understand that and the rest will come later.
That’s quite interesting. So in fact, much of the central stream that ended up with Heisenberg was not studied, probably was not know in Vienna?
We got it when the Schrodinger equation came. So we had a grasp; when we got it, we participated in the synthesis of the work. In Zurich it was very different. Of course, you see, Zurich was much closer. If my family had stayed in Zurich, and I had studied in Zurich, I would have been much closer to the events. Vienna was at that time a relatively large provincial university where things invariably got delayed. That’s no longer so because, since about five years ago, you now get much more of what is going on in Vienna. But when I was more grown up, and had been in Leipzig — I was in Prague afterwards — I practically got the news before they got it in Vienna. My family was living there, and I liked it very much; whenever I had the chance — I had vacations a lot — I went to Vienna. Of course, I went to the institute and I gave many talks there in Vienna at that time, often coming from Leipzig and from Prague. For instance, I came to Vienna when the positron had just come out, and I had just understood the Blackett and Occhialini paper. That was a strange experience because I came to Vienna just at the end of the term when it was practically summer already. I asked Thirring, “Would you like me to say anything about the positron?” “Oh, it’s too late. Now in summer, nobody comes in,” he said, “Well, listen, I have no objection if you want to talk about it, but next Tuesday is taken — there is a gentleman who makes bio-physics. He comes from Copenhagen. You go there and see how many people there are. If you think it’s enough, then announce it for a week later.” So I went. It was a nice talk; there were about 30 people. “If you got 30 people now, next week there will be 20. For 20, is it worthwhile?” I answered, “Yes, it is worthwhile.” So they announced it. And you know how many people came? Three-hundred. It was one of the most thrilling lectures I ever gave. There was interest in Vienna even in summer, though it was already hot! I had the same experience in Vienna a couple of years ago, when I organized these colloquia. I thought there would be only a few people who would come so we were in the small lecturing theater. First I got young people there to talk. And then I wanted one of Walter Thirring’s assistants to talk about the Mossbauer effect. He promised me to look at it. Before his speech, one thing happened: Mossbauer got the Nobel Prize!
I told that boy, “Oh, you have made friends with the Nobel committee to make propaganda for your talk.” There were 250 people.
Smaller than the positron fetched.
Yes, but anyhow it was not the Chemisch-Physikalische Gesellschaft, it was only the colloquium.
When Schrödinger’s paper came, did one recognize immediately that was important at Vienna?
Let’s say there was a toy to play with; you knew what to do with the equation. Now, the interpretation was more difficult. What I did not understand were these discussions about whether it was statistical or casual. If there were photons, there were waves: it had to be statistical. What I never really could understand was how can it not be statistical? The interpretation has to be a probability. There were lots of discussions at that time.... If you have an atom, and a wave with interferences, to me it can mean only a probability.
Did you participate in these arguments at Vienna or was this later now?
That was in Vienna.
You were back in Vienna after Bern?
After Bern, I came back to Vienna, yes.
And that’s where you were when the Schrödinger equation appeared?
I think I learned about Schrodinger in 1926 — already in Bern. I had a talk with Schrodinger, but that was when I was back. He came once in Vienna. I know that Besso came; that Einstein had written to him that the Schrödinger equation he liked much more [than the matrix mechanics] and that it was a very promising thing.
Did they think at first that it was wholly different from the matrix?
Yes. But Heisenberg saw the connection at once, I think, and Schrodinger showed very soon that it was an identity question. And then when that paper came out, well, I didn’t understand it too well. At the time before Schrodinger there was a paper by Lanczos. Lanczos said, basically, that there was a continuous version possible, and he wrote down integral equations. He put it in the form of integral equations. If he had once taken the trouble to show these integral equations could also lead to a differential equation — there was a special case which could also be put — he would also have had the Schrodinger equation. Heisenberg felt pretty bad about that. It would have been nicer if the Schrodinger equation came out from his equations. And though we knew about that, I didn’t understand. I remember the following thing: when the Schrodinger equation came out in the first paper — the theory came afterwards — the first thing was to try to make it relativistic. We were sitting there, Besso and I, in Bern, trying to get it to come out. Of course, the other people knew already that it was just an exercise. And so I sat down and I figured out that the Sommerfeld formula did not come out.... Then there was the question that Pauli had solved, the problem of the non-relativistic hydrogen atom, just by matrix mechanics. I never understood that paper very well.
Terrible. Very difficult.
That was a very disagreeable paper to read and to calculate. And since there was no need — we would have done it, of course — but since we got it so cheaply from the Schrödinger equation, we didn’t have to learn the other way.
Did you continue to try to make a relativistic form?
No, I had no business with that. It didn’t come out, I didn’t know where it came from, and I didn’t try. Pauli delayed very much his publication; he wanted to make it relativistic. But all these developments that came at that time were before the Dirac theory. And all that I had no understanding about. I had no basis to understand. I had been too far away. I saw just one particular aspect which seemed to me the easiest.
You were quite interested in the particle and wave business. You had a paper in 1927.
It was a very bad paper but at least the intention was good — to see the statistical character of the wave.
That was out before Dirac’s thing wasn’t it?
Yes. DeBroglie commented that it was very, very vague and very unclear but the intention was good. My interest got aroused afterwards in 1927 at the Volta Conference. That was one of the events which attracted me because I had a chance just to be a visitor — Ehrenhaft was invited to this Volta Conference. All the big shots were, you know, at the 1927 conference. And there I saw for the first time H.A. Lorentz, James Franck, Ashton, Bohr, Millikan, Planck, Heisenberg. That’s when I first met Heisenberg. Wentzel was there and Pauli. Pauli I already knew from his visits to Vienna. What struck me most was the personality of Rutherford; he made a strong personal impression. He gave a talk on nuclear levels and quantized with quantum numbers 17-1/2 or 18-1/2. Heisenberg made a very good remark, he said 17 was no quantum number. A quantum number was one, two with a maximum of four. So the paper was certainly not very good, but the impression he made was of a man absolutely sure of himself. He was tremendous. Einstein was the man who made the greatest impression on me, once in Bern. But physically [in physics] what struck me most was Ashton’s mass defect. He had just measured it all the way through. That made me think that I had to go into nuclear physics, so that’s when I started to look at isotopes and things like that.
Rutherford’s talk was what really put you onto this?
What made me work was Ashton’s curve.
But this ferocious self-confidence of Rutherford?
Yes, Debye wanted just to tackle him a little bit and asked whether he couldn’t tell a little more about what was in the nucleus. Rutherford said, “I don’t know, I’ve never been there.” [laughter]
Did Rutherford reply to Heisenberg’s remark?
Oh no. Heisenberg brought that up privately. That was much later when I was talking to him afterwards in Leipzig.
Before we get to Leipzig, I want to asked you a little about Ehrenhaft. Was he still with his sub-electron at this stage?
Placzek was there at that time. He was a good friend of mine. He was a little bit younger than I was, and he tried to make experimental physics. Ehrenhaft was very nice in a certain way. He didn’t want to involve us in his things. He knew it was unsettled.
This is Ehrenhaft.
Ehrenhaft, yes. We got along very well.... I got my job at Ehrenhaft’s Institute. He was very generous. As a matter of fact, he told me, “You have enough brains to make your own physics, so I don’t want to put you in my things, but you have to justify your salary. It is the lowest grad you can make at the University, but still you have to justify it. Will you make the administration of my institute?” “Okay.” It took me about half an hour a week. I wrote letters for him. It was a very simple business.....
I see. That was your duty there?
That was my duty. And then I was working there at the photo effect. Of course, we tried to get him away from these ideas of these divisible electrons. I think there were many people who thought it was a business to become popular. But at the beginning, long before I was there, he found the Brownian motion in gases, he found these optical effects, and he determined even the charge of the electron. But then he turned to the small particles, and he simply could not understand that there should be a limit to the charge. He tried to push that through. Then afterwards he became neurotic about it and you couldn’t talk to him. You attacked him, told him it was nonsense and he started screaming.
When was this?
When I was there in 1927, the end of 1926, I had been studying mainly on the fourth floor so I had very little to do with him. So I didn’t know..... And then there was Mattauch, who was sent to Pasadena and who was an assistant of Ehrenhaft. His assistants, those who were working with him, found particles with normal behavior (electron charge) and others with anomalous behavior. The smaller the average size of the particles was chosen, the more anomalous behavior was found. Ehrenhaft was mainly interested in the anomalous particles, because he believed that they were the ones which carried sub-electronic charges. There was always trouble about the weight one had to give the individual measurements and Ehrenhaft was always afraid too little weight was given by his assistants to the anomalously behaving particles. Philipp Frank once made a very nice remark when Ehrenhaft got excited. It was at the house of Ehrenhaft. Frank said: “I always got convinced that the whole question [the argument between Millikan and Ehrenhaft] finally would be resolved by a small claims court.” Ehrenhaft was all right, but you couldn’t talk to him about that.
But he didn’t oblige anybody to believe him?
Oh, no. On the contrary, he said, “There is a controversy and don’t put yourself in it....” His death was very tragic because I met him when I went to Vienna the first time after the war in 1952. He was in the hospital completely paralyzed. It was two months before he died. And since he had played such a ridiculous role here in the States, I was told people made fun of him; his children didn’t want to know anything. He was already dying and his children refused to come—things like that. I also was told that when he came to Vienna after the war, he took over. People didn’t like it too much. But he had the job. He had been dismissed, and they had to give it back to him, according to the law. But when he took over, he did quite a bit—helping young people, picking out young people to get things going again. Walter Thirring told me the first job he got was as an assistant to Ehrenhaft. Then there is the very brilliant mathematician, Hlavka, the leading mathematician in Vienna, who has a good mathematics school. He got his position pretty early, and they told me it was Ehrenhaft who had picked him out. Ehrenhaft went to the faculty and insisted, and he had a certain influence at that time. And he put Hlavka into the chair, and that was a great help to the development of mathematics after the war. It is like in field theory, when you have an infinite self-energy, you have to renormalize....normalize Ehrenhaft! [laughter]
And once you did that, he was perfectly reasonable.
Something positive remains, I would say. No, it may have been a personal vanity. H e wanted to become famous at any price, things like that. But there have been many people with this property.
How did he get along with the other professors and with people like Thirring?
Well, Hans Thirring was an awfully kind person. And I think what Thirring did was just his normalization philosophy. It’s foolish but, then, what to do? You had to do something with the man. And I had to go along with him.... So Thirring was between. But the other ones hated him. There was always lots of trouble between Ehrenhaft and the other professors. He was already on very bad terms with Stephan Meyer, for instance. The first thing that happened to me was that Ehrenhaft sent me with a message to Stephan Meyer. I had just come in completely innocent, Ehrenhaft know it. When I came there, I handed the envelope over. And Stephan Meyer found an old piece of paper. Ehrenhaft had borrowed some radium for ionizing particles, a small metal envelope with radium salt in it. And Stephan Meyer wanted to have it sent back. That was in 1926 or 1927. You see, it was from 1910! [laughter] So we sent me. That’s why — because I couldn’t very well be responsible. Then I had to stand there and hear all the statements of Stephan Meyer for about two hours until he found out, “Well, that can’t be your fault. Excuse me.” That was the truth.
What sorts of things did he say?
Oh, well, there were complaints about the radium: the radio-activity had gone and so on.
How about Smekal at this point? Was he a professor yet?
I think he had got the title of Ausserordentliche Professor. But he didn’t like Smekal very much.
He seems to have been a touchy fellow.
Well, he was ambitious. He wanted to make a success. His father was a great general of the old Army. Feld-Marschall Leutnant, I think. He got married first to the daughter of Wettstein, professor of botanics, possibly for a question of career. He was a good physicist; that must be said. He denounced my friend, Halpern so he had to go away. At that time, there was some trouble, it was very bad, ugly things were heard. A key was lacking, an overcoat had gone away — things like that. And, as a matter of fact, Smekal was rather powerful, so Halpern had to leave because of him. There was already lots of anti-Semitism at that time. I don’t know whether Smekal himself was playing it, but in any case, he made an impression. And like Horowitz before, Halpern didn’t go along with Smekal. He had to leave too. I had no trouble because I was good-natured; I didn’t attack anybody; and I left there by my free will. There I had a job and I had the possibility to go off. So I said: take my job and I go.
What happened to Smekal eventually? He stayed in Vienna until when?
He had been called to Halle and there I still saw him. And there he has been very much a German professor. And he did work, I think. But the other people didn’t like him. He came from time to time to Leipzig but he never was received very cordially. He went to Como too. What he did in Como was to run from one person to another and announce: “Well, what nonsense Ehrenhaft is saying.” He was making propaganda about Ehrenhaft.
Playing the Viennese politics at Como.
Yes, something like that. Then he became a Nazi and I think he adhered to the German Christs at the time of the Nazis. But when I was in Leipzig, he was in Halle. And I got to know Heinz Pose, assistant of Hoffman. He was found the first nuclear resonance. I became good friends with him, since we had common interests and I traveled frequently to Halle, not to see Smekal — I don’t think I’ve ever seen Smekal in Halle — I saw him in Leipzig, but I very often saw Pose there. He also came to Leipzig and we discussed things.
I recently got interested in a bit of Smekal’s earlier work, about 1919, 1920, 1921 when he was arguing against the ring explanation of the x-rays, against people like Vegard and so on — the Debye theory. That was probably something you didn’t take up. The whole tone in which he wrote was quite antagonistic, a different tone than you normally find.
I remember now about Smekal: I listened once to colloquium of Smekal about the mass defect. It was the first time I heard about mass defect, so it was something about the mass determination of helium. It didn’t make much of an impression. It was on one single point that I knew probably before I saw the mass curves of Ashton. And then, of course, there was Smekal on the division of light quanta, the quantum approach to the Raman effect.
You mentioned that anti-Semitism was already strong when you were at Vienna?
In Vienna it was very strong. The first trouble there was in around 1923 and it was very frequent. Hans Thirring in general declined to lecture as long as they didn’t let Jews into his lecture.
Well, he put an announcement outside of the Institute telling that he refused to lecture while a part of his students were not admitted.
That settled the matter then? The students were admitted?
Oh, no. He didn’t lecture on certain days when they couldn’t go in (they were beaten and everything) ..... That was in 1923, the time of the first rise of Nazism in Munich. Well, what happened at that time was that in Austria there was academic freedom, complete University autonomy. The police couldn’t go in without the consent of the rector — only if he called. It was taken very seriously. But according to my view, it was abused from the beginning because the nationalists — we’re not particularly talking about Nazism at that time — they took that as a license. They had the students, they directed the students, and the professors protected them in general. And that was very probably the main reason why they didn’t want to have Jews — it was an old rule that when a Jew should be come elected rector, that he should decline when it became his turn. That was an old agreement, and in Vienna, it was kept. (Tape is turned)
You were saying about the tradition being for a Jew when elected rector to decline.
Yes, and that was always kept, it was some sort of gentlemen’s agreement people had at the university. It was broken for the first time at the Prague German University which, in Austria, was always considered as one of our universities... But what happened in Prague: There was a rector, I think his name was Steinberg. I’m not sure. He became elected and was supposed to resign and he reassigned. He was prepared for that. But the Benes government declared now we will stop that, and they asked him not to resign and they urged him to the point where he accepted.
The government, the Benes government in Prague. So the Prague German University had a Jewish rector. Now he was elected and everything was all right and they could do their work with perhaps a little protest among the scientists. But they took a violent action immediately in Vienna. The rector, the faculty and the students mobilized.
Against the Prague situation?
Against the Prague situation.
What happened then?
Oh well, people were beaten and there were no lectures and the students paraded around with sticks. The government did not intervene in Vienna.
It was just a protest. It was not directed against anything in Vienna?
It was just an occasion?
Yes, it was just to show the strength of them in politics.
Were the students or the professors the main leaders in the University anti-Semitism?
There was a basic situation in which it was relatively easy since there were always bad words against Jews. It was quite common those days, though it was not so badly meant. But the whole thing must have come either from the professors or from outside the University and probably by means of these Studentenverbindungen, the Nationalistische Studentenverbindungen. The Socialists tried to set up their own. They had no power at the University.
Could the professors have reduced the incidence had they tried?
Well, if the faculty had been against anti-Semitism and not have favored it, it wouldn’t have been possible. I would say that was the first stronghold, and there was a certain reason for it because to study was a privilege in the old empire; and after the revolution and after the end of the war, one of the main slogans of the Socialists was that learning should be free to everybody, and they encouraged people. Then there were two factors which made the universities very large: one was that people said, “Now we have the possibility to study,” which they couldn’t have thought of before. And the second thing was that there was unemployment, which meant that a young man who was through school and looking for a job didn’t find one. Normally he would have gone into business or into whatever profession or job he could find, but since there was nothing to do, he would say, “Well, I’d prefer to use these years to study. It may be useful for me.” But studying meant something like studying medicine before the war. In the family, the idea was that this meant a career and a good bourgeois existence. A doctor is well off. There are not so many. He is needed and not everybody has this information. But when academicians got their degrees and found no jobs, they became much more likely to enter political propaganda. So to speak, they were promised something, and didn’t get it. They weren’t offered the standard they expected.
Thirring didn’t participate. What about Ehrenhaft? Was his institute anti-Semitic?
In his institute, no, but there were quite a number of people around in the other institutes who were violently against Ehrenhaft.
And Smekal would be one of the more prominent and influential anti-Semites?
I couldn’t say that he personally made anti-Semitic statements. At least I have never heard him. But he always acted as if there were something. He was always on the other side.
How did you arrange to go to Leipzig?
Oh, that came in the following way: I had written this paper about the photo effect and at that time Wentzel had done about the same thing. Wentzel was quite interested and he wanted to show me his goodwill, so I met him and Pauli. And Pauli, I knew. He had come from time to time to discuss with Halpern, and I took part in the discussions. But then in Como, they introduced me to Heisenberg ... And Heisenberg at that time had a job. He said that he was going to Leipzig and he had this job as an assistant and asked me whether I wanted to accept. Ehrenhaft didn’t want me to go, but I finally did.
You were Heisenberg’s assistant for —
Four years with one semester off for Cambridge?
Before we talk about the Leipzig situation, do you recall other things about the Como conference? For example, what about Bohr’s paper?
Well, they had arranged for an afternoon for quantum theory. And Bohr was making the introductory talk. As I remember, he was talking about wave packets and the role of measurement. But they were things that were familiar to me at that time.
What about his complementarity? Did that raise troubles?
I personally only heard Bohr about complementarity when I was in Copenhagen. That was 6 years later. First he said reciprocity, I think, and then he changed it to complementarity after the uncertainty relation.
It’s said that he wasn’t very happy about Heisenberg’s uncertainty paper.
He told me once that he had to correct it. But what he said about Heisenberg’s first derivation was that it was completely could because it was the first attempt — it was not formulated perhaps with all the refinements. But Bohr showed him at once that he could do that only with free waves, not for bound electrons, and Heisenberg calculated afterwards how much would be the uncertainty in the hydrogen atom for the nth orbit and different values came out. And then much later I sat d own just once with one of my pupils because there were articles in the Russian literature about how you could make the ?y very small and the ?p, would still be finite and these questions. So we looked at it once. We had solutions for the diffraction problems, rigorous solutions. What Heisenberg did at that time was that he took the ?y here, at the opening, but he calculated, so to speak the ?p, at infinity. And for a wide slit, this is completely admissible; but for a narrow slit it is not true mathematically. The uncertainty principle of course holds. So if one goes to this limit and makes the reasoning just as Heisenberg did, one runs into trouble, but there is no real trouble. I don’t know whether Bohr had this point in mind, too — possible, yes. But I think there were other details.
These details you speak of came up — at least so far as you know — in the early 1930s?
As far as Bohr is concerned, it came about immediately after Heisenberg’s paper. I wasn’t present. I know that only from what was told me afterwards — that Bohr tried to formulate, I would say, Heisenberg’s concept of uncertainties in a more precise way, and he wanted to say it in a way that it applied as a general principle. And he felt the way it was stated by Heisenberg was not sufficiently general. I think that was the origin of complementarity, but I could not affirm today that I understood everything that Bohr said about it.
At Como — or even later?
I don’t think there are many who can.
But I see there is a complementarity between the Fourier components. Of course, it’s quite easy to see. But how far did it go, whether Bohr had much more in mind that that — that I couldn’t affirm
What were your duties as Heisenberg’s assistant?
Official duties? I had only to correct the exercises of the students. By the way, Von Weizsäcker was one of my students and I had to correct his exercises. Otherwise, I could do what I wanted. I participated in the seminar. I also wanted to organize the ping-pong, over Heisenberg’s big objections. Afterwards, he came and said he liked it and I should go on. So, after the seminar one night a week, he allowed us ping-pong. And, of course, discussing.
Who was the champion?
Heisenberg was very ambitious. The absolute champion was a Chinese.
Yes, they’re often very good.
And later on a trip to Japan, Heisenberg learned it and then he became champion.
What were the interesting subjects immediately on your arrival there?
Heisenberg had just completed his work on ferromagnetism, and then he wanted to look more closely into the theory of conductivity. The main goal of Heisenberg as far as I understood was the he would have liked that superconductivity comes out, too. He wanted to show that — or wanted to look at least whether superconductivity came out. And then he was working with Block on different types of weakly bound electrons or strongly bound electrons to get expressions for the temperature dependence of resistance. I didn’t want to participate in that. I didn’t feel too sure about the model. The trouble was I wanted more Auschaulichkeit. These things were hard enough the way Heisenberg handled it. That’s why I didn’t go along with it very well.
So long as the mathematics produced results, he wasn’t too disturbed about the model?
I never understood very clearly what that was. I couldn’t follow Heisenberg’s reasoning. And I found out only the reasoning behind it when I went to Copenhagen. So I think to a certain extent Heisenberg had been influenced by Bohr’s reasoning. That could be followed though it was hard to understand. Bohr spoke very unclearly, and you had trouble to find out what he really meant. But afterwards, thinking about it, it looked quite natural. So I understand what was going on in Leipzig only after I had been in Copenhagen.
That’s very curious. Was there a sort of vagueness about Heisenberg’s procedures?
Well, Heisenberg calculated and applied his formulas, and he went twice a year to Copenhagen already in those years. Then Bohr compared it with his reasoning and corrected it, if it was necessary. That happened quite frequently. There were two things I didn’t understand in Leipzig just as a person: one was the way Heisenberg was reasoning, and saying that it had to be made like that without explaining why; and the second thing was the tremendous respect for Bohr he had. Because I thought that Bohr was an old man — he had made once a circuli, put the quantum conditions in and a model came out. But Heisenberg was really the man who had found the laws. And how could he think so highly of a man who made such primitive things. That was my idea, which was corrected very thoroughly afterwards! [Laughter]
Do you remember what kinds of things Heisenberg was corrected on when he went to Copenhagen?
I know that it struck me several times but the details I couldn’t tell you now.
So, in fact, you really did not work with Heisenberg?
You went your own way. You were beginning with isotopes already, were you not?
That I had already done in Vienna after Ashton’s curve. And in Leipzig what influenced me was the Gamow paper at that time about alpha decay. I learned about the passage through a barrier and then applied these things to scattering, anomalous scattering of alpha particles. I wanted to try to see what I could say about nuclear reactions. And then Pose had found these resonances, so I tried to see whether I could find any resonances with just these potential models. And this I continued much later in Kansas. I did a paper about anomalous scattering and I wanted always to verify the levels in wells of varying depths, varying the atomic number one should get at different levels — that can be registered by anomalous scattering. These effects exist, but afterwards they became overshadowed when Fermi showed the narrow levels and Bohr’s compound nucleus came. Now we know that both of us were right because the general levels trend exists, and the narrow levels exist, too. It’s a super-position of both things. But that I understood very late. I always felt very disappointed. Nobody wanted to believe me, that I’d found resonances. They were known. They saw them already in 1931 [W. Rietzler’s work] at the Cavendish, but they became recognized as that only after the war.
Heisenberg was already worrying about things like the electron in the nucleus and so on, wasn’t he, in those days?
Well, that was only when Dirac’s theory came out that one say that one was not permitted to localize the electron in the nucleus. And this point was very much stressed. That was, as a matter of fact, a signal to Bohr’s group to attack nuclear problems in 1931 in Rome — you couldn’t assume electrons to exist in nuclei, that electrons were produced as photons are produced by the atom.
That made the problem all that more attractive to him?
Heisenberg told us that he remembered some conversations with you about the electron in the nucleus.
Yes, I tried to put electrons in the nucleus making the systematics. And then I found regularities. I couldn’t explain them. Now it’s called magic numbers.
But this was before 1931 — these discussion to which Heisenberg referred when you were sure there was an electron in the nucleus and he was sure there wasn’t?
That must have been before.
Did people at Leipzig begin to study the Dirac papers immediately?
Well, the Dirac paper came out and I had to tell about it in the seminar. I didn’t understand it very well. The way Dirac’s theory became known to us was a very strange thing. We were in Berlin. Houtermans had a letter from Gamow saying that Dirac had found a new equation. He didn’t understand very well how they worked, about the non-commutative alphas and so on, and Houtermans didn’t understand it very well. Then von Neumann came and looked at the letter that even the author had not understood. Then he took a pencil, wrote the equations down, the commutation relations for the alphas down, put the properties of the alphas down, and wrote out Dirac’s equations. I understood it later. I didn’t understand it then. It was so quick and so immediate. It was fascinating.
This was the first thing he’d seen of it?
You must have lectured on it shortly thereafter. That was after the paper was published?
Yes. We still had trouble there in that seminar. I could write down the equation. It was how to handle the alphas that led to trouble.
How soon was it before those things were worked out before people had mastered it?
Well, I would say the theory wasn’t mastered until after Gordon’s work. When was this conference in Hamburg? Wasn’t that 1929?
The paper was in 1928, wasn’t it?
Yes, Dirac’s paper was in 1928, a short time after I came to Leipzig. I came to Leipzig in February 1928 so it must have been March, April or something like that. And then Dirac came to one of these Debye weeks, where he lectured about the internal degrees of freedom of the electron and then he had a discussion with Heisenberg which I remember because Heisenberg insisted that the whole previous theory should come out, that means that the spin was an integral of motion in the nonrelativistic approximation. He figured it out for Dirac and Dirac hadn’t thought about that. What you ask me about Heisenberg’s interest: he started very early about the radiation theory, and one day he told me what was the correct way to follow, where to go on, and that was when he started with Pauli to make quantum electrodynamics. He started very early. That he did alone. He had no collaborators. He was writing very frequent letter to Pauli and meeting him frequently.
Did he talk much about it?
He came from time to time: “This morning I have discovered the electromagnetic potentials...” But that was going on for quite a time because it was quite a job to put down quantum electrodynamics.
What about these negative energy states in the Dirac picture?
The negative energy states came immediately after the — well, I think they already are mentioned in Dirac’s first paper but “they never have been observed,” he put there. What intrigued me most while I was in Vienna was this dualism of the particles. And what intrigued us at that time was how the negative energy problem could be solved. We had many discussions with Landau, with Teller, and with others on what does this negative energy state mean? And nobody believed in the holes. I learned about it very late.
Do you remember what was said during these discussions at all?
We didn’t see any way out. One of the most important things would be how to solve this negative energy difficulty. How can negative energy exist?
But what did that mean for your attitude toward the Dirac theory in general? On the one hand, one took it and tried to work with it. On the other, one couldn’t quite make out what it meant.
It gave the spin. It gave the Sommerfeld formula.
It did everything but it had these negative states.
We just had to believe that it was not correct. We said, “There is a doubtful point in it. Maybe it has to be changed.” We did not believe in the holes. We got news about the holes. I don’t know whether you know this story so I will tell you about it. One day Gamow wrote that Dirac had announced in a talk at the British Association that he could solve the difficulties. Then Gamow had to go to Copenhagen and Landau wanted to go too. But Landau also wanted to stay because he wanted to listen to Dirac, and then he made an arrangement that he should send Gamow a cable to Copenhagen. Since the cable was very expensive, it should be as short as possible. It should say only one word — either “wonderful” or “quasch”. And at that time I arrived in Copenhagen, what happened was this. There came a cable and it said, “Herr Professor Dr. Niels Bohr,” and it had one word, “quasch.” Nothing more. [Laughter]
When the positron came, did one think immediately that these were the holes?
Oh, yes. That was immediate. There I do have personal experiences that I know, because of two things. When I was in Copenhagen in 1932, there was one of the last peacetime conferences and everything was fine — we called them the “Goldene Jahre”, the Golden Years. So the whole week all were discussing the problems: There were Heitler’s problems about the radiation theory, how to make radiative processes, calculate radiative processes with quantum electrodynamics — the general Heitler method and questions of that kind. And it was full of discussions, but whenever there was an opportunity to make a joke about Dirac’s holes, it was never missed. And Dirac was sitting there all week without saying a word. Then we wrote the famous Faust, the quantum-theoretical version. You may have heard of it. It was full of jokes too. The main point was always Dirac’s holes and things that became annihilated. And then the conference was over and Dirac hadn’t said a single word. He was just sitting there and just looking. And then at the last meeting before they went away, Bohr became quite impatient and asked, “Tell us, Dirac, do you really believe in that stuff?” And after one week of silence, Dirac rose — he was sitting beside me — and said: “I don’t think anybody has put forward any conclusive argument against it.” And then he sat down. And Pauli insulting him, saying, “How could a young man with talent do things like that?” Then I was at Copenhagen six months later at the next conference. Pauli went to the south of France. He didn’t want to be present w hen Dirac came with the triumph of the positron. Then something very strange happened and that was the reaction of Bohr. He had never believed. His first reaction was something that I never saw him do before. He called the Danish Physical Association. Now at that time Denmark had three or four physicists. One was Bohr; one was Moller; Aage [Bohr] was too little. Then there was Kalckar and Jacobsen. They were all at the Institute, so there was no need to call a general meeting. The members of the Danish Physical Society were high school teachers. So the first reaction I have to tell people about was that Bohr called the Physical Association — he was President — and he told them about the holes and the positron. And one could quite clearly see that while he was speaking he still could not understand how you make a particle out of the sign of the square root. But in spite of that, it was true.
This as the Blackett-Occhialini stuff?
Well, I didn’t know Carl Anderson’s work. I knew about Anderson later when, of course, one learned about it. But I saw it first in the Blackett and Occhialini paper where, you see, they say it could be understood. Then for somebody who was in the matter, it was a small thing to figure out what it was and everybody started writing down these equations and looking at just the negative energy states.
What happened at the meeting Pauli didn’t attend? Did Dirac go to that meeting?
He appeared for his triumph?
Well, he didn’t appear very excited. He had known before “It must be like that,” but he came and was quite pleased.
Did one try to make amends? Did Bohr then enthusiastically try to make amends?
I don’t remember what happened because I was not present. I think Dirac was living either at Carlsberg or close by. If there was something I was not present, and it was out at Carlsberg, not in the Institute.
You were in Cambridge in 1930-1931?
In 1930-1931 yes.
And those experiments of Blackett were underway then.
I didn’t know about them. But I was looking at experiments, I was mainly connected with Ellis and his spectra. Then I was quite interested in the gamma-ray work that had been done in Berlin, by Meitner and Hupfeld before these absorptions and then Gray and Tarrant were working on that. And then, of course, this scattering, a problem always connected with the Cavendish.
How was the Cavendish then?
Did one see much of Rutherford?
He came in the morning. They were very crowded, very little space; they put an Australian student to make measurements in the entrance. Chadwick couldn’t lock his laboratory, so he put a red lamp when he wanted to start measurements, so nobody came in. So this Australian student thought he should do the same thing. When Rutherford showed up the light was flashing: “Damn you, shut up.” He was disturbing the measurements with his loud voice. And Rutherford was to be seen at the Cavendish running around and speaking bad about theoreticians in general, about people who wanted to have an idea once in their life and then to become state-supported, and talking around in the laboratory instead of letting people work. But he was very friendly. Once he took me to his office and told me: “It’s lots of work...., I have to think about many things and about the future [of the laboratory] also.” He made quite an impression on me.
Was Thomson around at all?
Only at official occasions. Rutherford was never invited, say, for a Cavendish dinner or any official meeting without J.J. Thomson also being present. And all the talks were not about Rutherford and so on, but about J.J. Thomson and Rutherford to tell them how proud they were of them. The British are very — they put J.J. Thomson out because they wanted Rutherford in 1918. J.J. Thomson felt pretty bad about it.
Actually, I think that’s not quite true. There are letters exchanged between Rutherford and Thomson about the circumstances of the succession, and they’re all very warm.
I think they personally may have been very warm, but the English what they did — of course they didn’t tell a make like J.J. Thomson, “Now you go home.” But they proposed him as ...?
Right, he became Master of Trinity.
Master of Trinity College. He could have declined if it was Caius College or whatever. But Master of Trinity is the representative of His Majesty, the King, and one cannot say in England to the King, “Listen, I don’t want to be your representative,” so he had to accept. That was the way it was.
I had the feeling that had he wanted to stay, he could have. And Rutherford, you know, for some time had been happy at Manchester.
He had his laboratory and he could go on of course. But the general feeling of the young people, in any case, was “Now we wanted Rutherford.”
I think that’s true. So all the official announcements were in the name of Thomson and Rutherford?
And I liked that very much. That was a splendid form. Oh, Cambridge was wonderful. As a matter of fact, the atmosphere at the University that year — maybe it has changed afterward - but in those years, I was much more impressed, let’s say, with the atmosphere of the Cavendish than in Copenhagen. That was my personal impression.
With what — the camaraderie, the organization?
With just the atmosphere of work and the man who was directing the work — a strong man who knew exactly what he wanted — Bohr was very soft, you see, and Bohr was growing but Rutherford was no longer growing. Rutherford was already developed. I came to Copenhagen in 1932. Well, I would say that Bohr was a great man, but Bohr was not yet up there [pointing]. He was down here [pointing again].
Rutherford was all grown up by the time he started. It’s amazing how even when he was very young in McGill, he seems to have known always what he was about.
For 30 years, he was directing his research and developing three different types of methods. First he was a chemist; then he was shooting alpha particles; then he was developing techniques. He knew exactly what he wanted and why he did it. He was always in command of things. He had tremendous insight. At McGill there’s a booklet where it’s very nicely told. It says, “The 30 year old professor was like an alpha particle in his concentration of energy, capable of making enthusiasm in anything short of a cow or a Cabinet Minister.” Have you read this small book about Rutherford?
Which one is it?
It’s a small book. Somebody lent it to me. It’s just called Rutherford.
It’s not the one by Andrade?
I can’t remember who wrote it.
You were in Copenhagen for how long? A year’s time?
I have never been there very long. I stayed four months and went to Prague afterwards. But then I was connected with Copenhagen for two reasons: first, I was always informed when there was a meeting and I went to the meetings. And second, I got engaged in Copenhagen. I went to see my bride at that time. So I was quite frequently in Copenhagen but only for short periods — I never stayed long.
You went to Prague from Leipzig then?
Yes. And there I had to start my own program, first to develop and then start some independent work. They had an extraordinary professorship but the government had not granted them the money; it was not very sure, not a stable situation.
And how did it happen you then moved to Odessa? To Russia?
Well, in 1933, trouble in Germany started and it became clear that in Czechoslovakia there was no future so I had to look for a job. Then I got an invitation to Kansas, but they wrote to me in the first letter that it would only be for one year and that it couldn’t be extended. So I got afraid. And since I had been in Russia in 1933, I knew the people there — with James F Franck in Copenhagen, we had talked about Russia and the Russians. He had asked whether the Russians could do something, and Frenkel was quite enthusiastic about the job. I didn’t want to go along, but Marcel Schein who was in Zurich was in trouble and wanted to get out. So I combined with Marcel Schein that we would to Odessa. The initiative was taken by Frenkel. He wanted something to be d one there. So Schein went to Odessa and I went for a year to Kansas. And then there was the problem that since I didn’t know the situation in the States, I didn’t know what would happen afterwards. So I went back to Odessa and was with Schein — no, that was before Schein was there. And I settled with them I would come in 1935. And from the States I came to Japan and went directly to Russia. I stayed there for two years until the situation was so tense that I wanted to get out again.
You didn’t manage to get much done there did you?
What I remember about the two years: I was completely worn out. I had been working for 18 hours a day because I had all the lecturing to do. I couldn’t do much work of my own. I had no time for it. I had about four or five boys to take care of, and I make them work. And then I had to take over Kiev — ell, that was in part also due to Frenkel, because the question was this: They wanted to have somebody for Kiev, so they wanted me to take over traveling to Kiev, and to keep the situation open and clear until they found somebody. It was not intended that I should stay. They wanted Weisskopf.
Well, the people in Leningrad. And I got some money in Odessa to invite people. I had lots of trouble to get it. Finally they gave me three thousand rubles so I could bring some people, so I invited G. Placzek and Weisskopf. They tried to convince Weisskopf, but he had a job with Bohr and he was thinking of going to the States. He didn’t seem very sure about the future either. In any case, it helped him, and he came to Odessa and I went with him to Kiev then to show him the place, but he declined. That was the story. It was told differently in Jungk’s book for instance. Bohr hadn’t sent Weisshopf. The initiative essentially... Well of course, Frenkel had the support of the people in Leningrad, of the old guard — Joffe, Mandelstam and Tamm and all these people were very favorable to get in people, to help people by getting them jobs. But the main initiative was from Frenkel.
Did you master Russian?
My origin is Czech, you see. The first language I learned was Czech so it wasn’t so hard for me. For six months I tried and after one year, I spoke and lectured in Russian without any trouble. I think if I go back for a few weeks, I would learn it again.
You must have learned languages with no trouble.
I hadn’t too much trouble. It’s easy for Czechs, though. People say that they never get the correct accent in Russian. But for lecturing, it was enough. The students were wonderful.
Were they well prepared by the time they got to the University?
No, but they were tremendously enthusiastic, something I find lacking in South America. The spirit there is still in the period of frustration. They have just come out of a situation where everybody said, “Don’t you know that a thing like that you can make in France or in England but never in the South American countries?” This period is over now, but when I came to South America it was still the case. If you wanted to show that you were a well educated person, you said, “This cannot be done here.” They still are looking for all the reasons the job cannot be done. That had also been the case in Russia in the late 1980s, a spirit of nihilism. You don’t know what to do. We are not satisfied. Then people started saying, “We can do it and we can get the conditions to do it and it’s necessary and we want to have it.” Of course, there was the political propaganda. “The old regime couldn’t provide the possibilities but now we can.” But the enthusiasm of young people was not political. The students were not political.
The good students in Russia. It was a very amazing experience. All these boys from bourgeois families in Russia had just recovered their liberty to study, and they had some basis at lease from home, some home education. And once they knew me better, these boys started complaining about the philosophy and the dialectical materialism they were taught at the university. They were afraid of telling it to anybody, but since they had confidence in me — once they knew me better — they started talking like that. Even Landau did: “Yes, now they teach military training in the university. That’s a good thing. It can help you defend the country if it is attacked. What dialectical materialism is god for, I don’t know.” That was about the spirit among the young people. They wanted to learn and they didn’t want to have cheap [easy] exams. Schein tried to cheat a little bit since there was lots of pressure in order to get statistics higher. And when I came to Odessa, I told them, “In two years you can have a bad university.” And after two years we had a wonderful point among all the faculties in Soviet Russia — a single point far below the general curve. [Laughter] And they started making noise, and the whole thing made lots of trouble though nothing happened to me. What happened was that one of the chemistry students was with one of our boys — I had about 150 students — and my student said to the chemist, “You have already made your exams?” “Yes.” “What did you get?” “Otlichno,” that means the highest grad, exceptional. “Have you made your exams?” then the chemist asked our student. “Yes.” “What did you get?” “I got ‘sufficient’, but an honest one.” The party handled it, I learned afterwards. There was lots of trouble and discussion. Finally they decided they wouldn’t do anything, better not to do anything, so they just let go of it. That was the situation. Russia was a typical under-developed country. It had tremendous enthusiasm — very different from South America. I learned a lot there about the way to handle students. But there was one thing the Communist government didn’t want: they didn’t want to destroy work by not caring. They wanted these things to be developed. The South Americans don’t care. They make politics and whatever goes to hell goes to hell. It was not pleasant from the personal point of view, but it was extremely interesting. There I met Landau, Tamm and Cherenkoff. Now they are older people. Then, they were the young people. In Moscow and Leningrad they were pretty well-informed. You see, when I came from Pasadena, there were no mesons there, and I met Yukawa in Kyoto. He was quite a young chap and he told me about his quanta. I didn’t understand very much about it. Then I came to Moscow on a ten days’ trip, and in Moscow they had already the news that in Pasadena they had found Yukawa’s meson, the first heavy particles.
From Kansas you went via...?
From Kansas I went through Pasadena, stopped at Pasadena. Dirac happened to be there that day. Oppenheimer was there and Millikan. I think I gave a talk there in Pasadena. Then I took the boat to Honolulu and Japan, and Dirac came at the same time. We were lecturing at Tokyo. Then I went to Osaka and Kyota and Yukawa took me around. He was quite young at that time. I knew Nishina from Europe. He talked quite openly. I didn’t know very much about the situation. For me it was quite important for the following reasons: He told me that he had spent eight years in Copenhagen and he didn’t want to come back but they pressured him to come back. He was picked out after having done outstanding work abroad as the Japanese wanted to make a university at that time. He told me that the situation was different from Europe because there were different political factors — about the Army he didn’t speak very openly but the Army was, of course, reactionary. They didn’t care too much about science and they were more important, let’s say, than Parliament or the government. Buy my impression was that if there was once a man picked out like Nishina — later Yukawa came spontaneously — the thing is safe. The whole thing will develop from him alone. You have just to put one good physicist in, and the thing has its own inertia. Others will listen to that man if he is able to tell what they should do and how to do it, and then he will attract other people, because physics is a beautiful thing. That was true in Italy with Fermi, and that was true with Landau in Russia; and that was even true in a thing as strange as Japan, so it must be general. [Laughter] Then I came to South American where I found a man who has done outstanding work... That was Gaviola, fighting 20 years of his life against resistances — he may have been a little bit too violent, that’s a personal temperament — but the whole milieu was against it, the whole environment.
But things are beginning to look better?
Well, I would say they are among the young people. Just manage to get in touch with the young people and they get as enthusiastic as the average boys of every nation. About the Brazilian-Portuguese — I would say only one thing, they are very intelligent — they are individualists comparable to the French. You see, the government doesn’t know; the universities are against it; the old people — that’s a general thing — the old people would always be against it. There are no full-time jobs. With any institute — they can take the money away without keeping it running, or they can put somebody in charge who is there just to make politics or any army officer who want to make physics at eight in the morning. In Argentina we are closer to a solution, but it is not yet safe. Being more general, science in South America has been at certain times persecuted. I don’t think there is any persecution now. It is tolerated. It is not really helped. It grows very slowly.
How about mathematics? Is that stronger?
It’s less violable. You can’t violate it so much. You need only a sheet of paper and so mathematics starts. But the first thing they start is biology. First, they want good doctors, and then the people who are involved in the research can always make a living as a doctor. So they start first. Then come the mathematicians. But physics is harder. Theoretical physics is easier than experimental physics, but it is not well connected. It needs more literature.
And more machines.
More machines to do experimental physics. The question about machines is not so critical because you can make some sort of experimental physics with relatively small ones. You can’t make a small cyclotron.
Not in this country.
I know what else I wanted to ask you about: the neutrino theory.
Well, I didn’t believe in the neutrino because I knew there were these experiments of Ellis and Wooster, and Meitner and Orthmann. They got the heat of the electrons but not the heat of the neutrinos in the beta decay. And Bohr thought at one time that there was a violation of energy conservation.
He was always willing to admit that, wasn’t he?
The first time he was in trouble with quantum mechanics he thought the energy came out statistically. Then energy conservation worked once more. Then Bohr got afraid again. But the question was: when the Dirac theory came out, my first idea was that I could use it for the beta decay; there is a lost particle. So I made a bet in 1933 and started to make an inspection. And then we wrote curves down with K. Sitte. That wasn’t so bad, but we didn’t put the mass of the second particle as neutrino, we put the electron mass. We showed there was an upper limit and a lower limit of the B-spectrum. We wanted to figure out where did these constants, these empirical coupling constants, come from? How much would be the lifetime of the neutron? It worked out at about a quarter of an hour, and it was measured for 12 minutes. But that was 20 years later! So about these things we knew, but about the neutrino, that it was a neutrino, I didn’t believe in it because I calculated the cross-section of a neutrino, it was the correct value, 10-44 cm2 or 10-43, or something like that. Doleck worked it out with me in Kansas at that time. So I didn’t believe a thing like that could be measured. Afterwards it has been measured. But it had something to do with particle creation, as in pair production, that we had to deal with.
Did you get much interest in your theory about the beta decay?
For two years about. Then afterwards came Fermi’s theory with the neutrino. What stopped me from the question was this: Well, Bohr wanted me at that time to go on, but where there constants came from was not explained up to now. I told him I didn’t believe that this can be found out at the present stage. But what stopped me afterwards from working on beta decay — When I went to Russia I wanted still to work on beta decay, but afterwards the thing became so troubled, I had no access to experimental data. They were looking at the different types of couplings. I couldn’t participate in this, so I tried the things that I could do.
No literature at all was available in Odessa?
In the early days there was very little literature on B-decay but when the main measurements came out, there were lots of difficulties to remain in contact. There were two things I have been lacking. I couldn’t get any — In these times the important things were not to be found. There were data about beta decay. And t here were data about magnetic moments, spins and nuclear magnetic moments. That I didn’t have...I couldn’t get any further in 1935 with Horsley and Dolecek in Kansas. So these things I couldn’t keep up. It made no sense to try to work just without the data.
You came to Paris before you went to Lyon?
What happened was this: When we came out from Russia, I didn’t want to leave. I thought there was going to be lots of trouble ahead. But Schein didn’t want to stay. It was quite fortunate. I don’t think staying there in Odessa I would have come out living. But after Schein went away, he went to Prague and then with A.H. Compton’s help to Chicago. My wife was in Copenhagen so I went to Copenhagen and I looked at the situation there. There was a meeting in 1937. It was the last I have attended when Bohr was there. And I saw that the situation was very stressed and if I had asked Bohr to stay in Copenhagen, it would have meant trouble to him. I knew Solomon, the son-in-law of Langevin, quite well. Once I saw it would make trouble for Bohr to keep me in Copenhagen, I wrote to Solomon that I would go — I thought afterwards I could come back to the States. So Solomon or Langevin wrote me they could get me some fellowship to stay in France. And I came to Paris, and while I was in Paris, the Anschluss came. So my problem was that I had my mother in Vienna. She happened just to be in the house of my grandfather in Czechoslovakia. She was caught in Czechoslovakia.
I was caught in France. I lost my traveling documents, so I couldn’t move. I had to look for a job in France, and in Paris there were so many refugees at that time that it was hard to get something. I went to Copenhagen once for a visit and I asked Bohr to write to Thibaud. Rosenblum advised me to do that. “Thibaud needs people. He’s quite alone there in Lyon.” Bohr was willing. Thibaud got me a job at the Centre National de la Recherche Scientifique. So I came to Lyon and there I was caught by the war. Then in Lyon there was a rather strange situation for the following reasons: First, there were already some refugees. Peter Havas, who is here [in Philadelphia] was there. He came to Lyon and he was working with me on fission products, and then the war broke out and I went to a concentration camp under the French. So I wrote around. Finally Peter came out and I stayed in. I felt quite happy there. I was working there in the administration of the camp. It was some sort of an intellectual vacation for me. And then we be came mobilized. There were also some funny kind of enterprise because they wanted to pick out the scientists and put us in the University of Montpelier. They made some luxury concentration camp in a castle for us, about 30 people.
We were supposed to do auxiliary work at Montpelier, translating papers and things like that. It was not very exciting. Auger was there, he had the idea. While we were there, the German attack came and France broke down and we were taken to the Pyrenees, again in a camp. I managed working there. I ran away fro the camp. I had just got my last pay, so I had a little bit of money. I rented a room. I got a mathematician assistant out of the camp and we were calculating formulae in the Pyrenees. Then we were taken to Albi, and there I had trouble with my eye. I got a leave. I came back to Lyon. There I got Thibaud to write a letter to the general and then I stayed again in Lyon. In the meantime, I had been already for a year in Lyon when the whole of France came down, the Belgium army and all that. There were a lot of scientific refugees around. I was at home, so I had to organize the work. I had a big seminar there in Lyon in the midst of the whole trouble. Twenty-thirty people came quite regularly. And we had nice meetings because Hadamard was there and Jean Perrin. Lyon had been an empty university and then it was suddenly quite full with Paris people from the Ecole Polytechnique, etc. And since I knew the people at the Prefecture, I was running around helping to get the documents for the people who wanted to leave — French people and foreign people. Then I got Jean Pireene from the Belgian Army. He was working on his thesis about positronium there with me in Lyon; it was the first theory about positronium. He published it much later. There was no possibility to publish at that time. It came out in Geneva in 1947. Then I got the documents for the people and I mobilized my students when there were no taxis to take the luggage to the train for the people who were leaving. I was the last and proud to be the last that left. Magat left from Casablanca on the 20th of December. The others were not in danger. They told me to stay. They could hide me. I said, “Well, what’s the good of running around like that? Better you do your work and I work abroad.” I had by chance gotten a visa to Coimbra. It was by no means easy, but I just got it. From the camp I once wrote a letter to Coimbra and asked if there was a job for me. I was sitting there quite desperately in Lyon — Havas had already left for the States — and then I got a postcard from the Portuguese consulate. People were paying up to 100,000 francs for a visa. I couldn’t afford that. They made me pay 50.50 francs and I had a visa to Portugal quite unexpectedly. I knew then Pirenne wanted to stay, and nothing could happen to him. He was a rich man, and there were all sorts of possibilities.
The French people could go along. Those who wanted to leave, the Jews among them, had gone from Lyon. Rosenblum had left and Francis Perrin had left. Auger had gone, and I was the last one about. The only one who didn’t want to go out and managed to stay there was Haissinsky. He was there with us. There was Goldstein and Rogozinsky; there all went to the States. I had no money so I wrote a letter to Germany seemingly addressed from Switzerland. They had still a few marks from a book in German and I asked them to send it to Paris. I sent that to a sister of a friend of mine who sent it to Germany and I got a rather short letter. I had first to apply for a permit. They sent me the marks, about 300 marks, which was a fortune at that time. They sent it to Paris, 20 francs a mark was the official exchange. And people brought it to me illegally to Lyon. Then I went to Vichy with my “ordre de mission”, which I had written myself, and had it signed by people at the university. Then I went to the Vichy man. I said I couldn’t go to Portugal without money, and finally they gave me about $1 for a mark. So I came with $300 to Portugal. I was a rich man. I got immediately sick from the food I ate there. I couldn’t stand it anymore. Then I lectured there for about three months. What happened in between was that the States went to war, and I had to stay on. My mother and other relatives were already in Theresienstadt. My problem was whether I could get them out. So I tried to find a neutral country where I could get a visa for them. I couldn’t get a permit from the Germans for my relatives to leave Czechoslovakia and then everybody perished. I lost all my family there. My wife was in Copenhagen. So that was the way I came to Argentina.
Yes. I wrote to Argentina. They had a job. I got the job, I got the visa, and then I came over in the “Zwischendeck”. When I came over there, I was already a state employee in Argentina and I met some friends and I jumped from the boat directly to a big dinner in the Jockey Club at Buenos Aires. That was the most fashionable place. It was one of these transitions I have experienced. Then other problems came, but that is not the subject of this conversation.
Added after the interview: I think that what you call the central stream was little known during the years I studied, not only in Vienna but in most universities. In order to learn about it, one had to go to places like Copenhagen, Munich, Gottingen, Tubingen, Zürich and Leiden. What was more generally known were the puzzles deriving from the photon concept.