Oral History Transcript — Edoardo Amaldi
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Interview with Edoardo Amaldi
by Thomas S. Kuhn in Rome, Italy;
April 8, 1963
Edoardo Amaldi; April 8, 1963
ABSTRACT:Part of the Archives for the History of Quantum Physics collection, which includes tapes and transcripts of oral history interviews conducted with ca. 100 atomic and quantum physicists. Subjects discussed their family backgrounds, how they became interested in physics, their educations, people who influenced them, their careers including social influences on the conditions of research, and the state of atomic, nuclear, and quantum physics during the period in which they worked. Discussions of scientific matters relate to work that was done between approximately 1900 and 1930, with an emphasis on the discovery and interpretations of quantum mechanics in the 1920s. Also prominently mentioned are: O. M. Corbino, Eugene Feenberg, Enrico Fermi, Antonio Garbasso, G. Gentile, Tullio Levi-Cevita, Lo Surdo, Macaluso, Ettore Majorana, Quirino Majorana, Wolfgang Pauli, Enrico Persico, Giuliu Racah, Franco Rasetti, V. Volterra; and Universitat Gottingen.
Kuhn:I did want to ask you one question. There must have been, or at least there may well have been when those papers were collected, not only papers by Fermi although you said, I think, there were very few or perhaps no Fermi letters. How about letters to Fermi?
Amaldi:Not many. I have here the reproduction of a few letters. These are letters by Rutherford. These are reproductions of these letters. About all is lost. This is another letter to Rutherford, but there are very few, very few. Fermi was not writing very much. Well, all the originals are at the Domus Galilaeana because this is the right place to keep these things. There is a rather long list of papers, of manuscripts, that came to the Domus.
Kuhn:Well, you very kindly sent me a copy. The library has been trying to get that, and their first request --. The Berkeley library wanted microfilms. You remember I wrote you that I wanted to get microfilms and you said you would talk to Professor Polvani who said he would be. glad to do it.
Amaldi:And he did not get it?
Kuhn:The first letter -- nothing happened. Now they have written again; I don’t know whether something has happened or not. If it hasn’t happened by the time I get back to the United States, I will then write you.
Amaldi:I’m afraid there has not happened anything. No, they are very nice people but they are rather slow in these things. I’ll write about this You’d like to have --
Kuhn:I’d like to have a negative microfilm of all the papers of Fermi from the Domus. We’d like one copy for Berkeley and if it is agreeable, we will make a second copy ourselves for the American Philosophical Society since the records are supposed to be at both of those places.
Amaldi:I know that one copy of these papers should go to Chicago because in Chicago there are the other manuscripts and the idea was to exchange.
Kuhn:My first concern is to make sure that things like this are already in good hands; after that it does not become vitally important as to when we get the film.
Amaldi:At the Domus they don’t answer, they take their time. I remember there is a very nice man there but he’s slow, And if you see this place, it’s very nice. There are a lot of beautiful things by Galileo and you remember that everything is kept quiet and preserved for the next thousand years. They are there for the next thousand years, not for the next ten or twelve. So they are certainly well-preserved. Well, I will try to get these things made.
Kuhn:I would be very grateful. We wrote, because I did not know who was officially in charge --
Amaldi:Do you want all the theoretical and experimental material, because the is a number on them.
Kuhn:And the letters, yes.
Amaldi:Letters, there are not many.
Kuhn:Whatever you’ve got. We’d really like, I would say, all the Fermi papers that are there.
Kuhn:This period, much more than the Chicago period or the American period, is what concerns us. We are not really getting into nuclear physics...
Amaldi:Because now there is the second volume that is quite fine but that is just mainly pion and neutron physics -- the last development of neutron physics -- the American period of Fermi. This nuclear physics is something else. Well, then, your interests are mainly for the real old things. The one thing I regret very much is that I’ve never tried as I should do, to get in touch with the brother of Majorana and see if they had in the house some letters or something of Majorana. Because I think that Majorana has really been quite an amazing person. May I tell these things since they will perhaps interest you.
Kuhn:Let me say this: we have tried to find out something about Majorana and we can’t find out anything. I cannot find out how old he was, I don’t know when he was born. So you could start at the very beginning as far as I’m concerned.
Amaldi:That I do not know. He was two or three years older than me; he was born between 1905 and 1907, I would say.
In (Catania). The family was Sicilian. He could not have been born in many other places in Sicily. He was really an absolutely exceptional person. Probably we have almost never seen a person like that, Even Fermi used to say that. As you know, he disappeared at a certain moment. He decided to disappear. He wrote a letter saying that he did not like this world and he wanted to disappear. And he disappear He was a very, very, very peculiar person. Each time that he had done something, there was a big fight with Fermi, because Fermi wanted him to publish. Majorana did not want to. And so, for instance, he tried at the same time to use his forces as well as the isomer forces about two years before (???) -- immediately after the discovery of Chadwick. The paper of Chadwick was done in January and I think in April [Majorana] started; he had written down the expression for the exchange forces, (all possible forms). All of it. Then he started to make a shell model; this is not known. 1i started to calculate the shells. Then he arrived to carbon and was not able to do anything. He had started to calculate the helium and he had shown that when you take it was quite clear with the small binding. And when he arrived to carbon, or immediately after carbon, soon, these are very light elements, he had troubles. There is nothing astonishing about that. Then he said that that was Stupid. Everything was completely nonsense, obviously. Fermi had to go to Paris at that time to give lectures at the Poincare Institute and said, “If you don’t mind I will give my lecture on these ideas.” And Majorana was furious; it was one of the times we have seen him really excited. He said, “I forbid you to mention these things that are so stupid. I don’t want that you go around discrediting me. If you want to mention it,” he said, “you should say that it has been done by Giorgi.” That was the Professor who had invented the system of units. You know, the Giorgi system. Well, he was strange. He was very unhappy generally; he felt unhappy. Very nice. He was a great friend of mine. We used every day to spend some time together. But he was (???) over everything. He felt that everybody was stupid, including himself. The only people that were not completely stupid in his mind were Dirac; Heisenberg was stupid, just to mention. Dirac was not stupid, and Weyl. He had great respect for Weyl. Everybody else was stupid. Even himself. He did not say that the others are stupid and I am so intelligent. No, he was convinced that he was stupid. He did not want to publish.
Kuhn:Was Fermi stupid to him?
Amaldi:Well, a bit. Fermi was his friend. With a Sicilian, friends should not be criticized.
Kuhn:How about Pauli?
Amaldi:He was rather stupid. But Majorana was stupid himself, he was convinced. This gave him a sense of (emptiness).
Kuhn:How did he come to Rome, and when?
Amaldi:His family was in Rome. Well, his family is a big Sicilian family, a rich and powerful family, of (Catania).
Kuhn:But he was both in Sicily and also in Rome.
He was living in Rome for many years. He was a student of engineering and he was of the same year as Segré, also a student of engineering. That was at the moment Segré went into physics and he knew Majorana. And he said to him, “You should do physics and not engineering. You are the right man to do that,” said Segré to Majorana. So he went to study physics. He was an absolutely exceptional personality very complicated, but at the same time, extremely nice, extremely friendly, extremely kind. He used to write a full paper on a package of cigarettes. This was typical. He would write very very small, complete and formal as he would fill in. Then when he had finished with the cigarettes he would throw the paper away. He was writing on this as long as he had cigarettes. He had a great human friendship with Feenberg. Maybe Feenberg could give you something because they liked very much each other. Feenberg was in Rome for some time, for one year. Feenberg was very young. I think that maybe he remembers that Majorana was trying to do a shell model because after he had done so much in shell models. But they could not talk to each other because Majorana did not want to talk in a foreign language. He was strange; he would say, “To learn other languages is a deformation of the personality.” He had very strange ideas.
Kuhn:Did he read other languages?
Amaldi:Yes, and he was extremely, incredibly, cultured. He knew philosophy as very few people do. He knew medicine -- was a great expert in medicine. He had read all the big encyclopedias of medicine, right from the beginning to the end. He did not almost sleep; he spent all the nights reading. He was usually not reading physics. Almost never. He read literature. And he knew really well. He was a very strange person. Feenberg and Majorana were for months studying without talking, always smiling from time to time. One close to the other in the library. It was very amusing to see these two people who could not communicate.
Kuhn:What did he do about language when he went to Germany?
Amaldi:I don’t know. Probably he was writing. He had to learn a bit, but he was very (???).
Kuhn:But he read German.
Amaldi:Oh yes, yes. He knew very well also classical languages. He was so quick. He was also a bit of a calculator. You know that.
Kuhn:I’ve heard something about it.
Amaldi:You could write any expression -- complicated. People would fill a blackboard (just to make normal passages, nothing difficult), and then they made maybe an elementary integral, with sum signs and then you had to put in numbers. He was looking one minute and then he would give the number. And it was correct. This was a big game. We had done it so many times just to check the correct calculation, the complicated expression, and then put numbers in and then with a stop watch to measure how long it took him to give the number. He was very good at that. Just look at the blackboard, smoking all the time -- he was smoking all the time -- and then giving the number. Very strange. Quite amazing. But this is a second-class capacity, but he was extremely intelligent.
Kuhn:Did he talk about physics?
Amaldi:Oh yes, very much, very much. He was talking about physics. He was talking about politics, he was talking about everything. He was always talking--starting always with an unhappiness feeling, with a --
Kuhn:How did he feel about the state of physics, about the condition that physics was in? For example did he worry, as Fermi did, about the infinities of electrodynamics?
Amaldi:That’s a good question, and I don’t know. Well, you see, the relations with Fermi and Majorana were so different because they were different persons. Fermi wanted and liked to work in public, so to say. He was glad when three or four people could talk and talk all the time, to go to the blackboard and try to explain and so on -- he was much more extrovert, Majorana was a completely different person, so it would be difficult -- I really don’t know. Probably yes. Fortunately Rasetti may remember something about Majorana. Segré certainly can remember something about Majorana, but nobody else. Persico did not know him because he came a bit later on.
Kuhn:Persico left Rome just as Fermi came. Now, if it is agreeable to you, let’s go back to the beginning. Fermi will obviously come in and out. Instead of directing ourselves to people, let us talk about the situation of physics in Italy, particularly Rome which you know best, but also where you can compare it with other parts of Italy and with other countries. I need, if you don’t mind talking about very elementary things, to know something simply about the structure of education in Italy -- the things I know immediately about America and have learned about Germany and France but don’t know at all about Italy.
I’m quite glad to do that. Well, the situation in Italy I would describe as follows. I don’t know about the period immediately after the First War, when Fermi started to be in a university and then got his degrees. I was still a student in the Liceo and then at the university. I think that one can say the situation in mathematics was rather good. There were mathematicians of a very high level. There was Volterra, a person of very international standing. He was very much bound with French mathematicians -- but he had his own independent development. And there was Levi-Civita. In Padua there had been -- I had been in Padua when I was young -- I remember Ricci-Curbastro, who is the man who started the absolute calculus that was used by Levi-Civita and after that, by Einstein for the general relativity. Thus, in Padua, in Bologna, in Rome, in many other places, there were really first-class schools of the mathematicians. I remember when I was young here in Rome I had as professor Levi-Civita, Volterra; they had been in Pisa. Levi-Civita was in Padua, there was Ricci-Curbastro, they were both there and Ricci-Curbastro died and Levi-Civita went to Rome. And I would say that also in these places after they left, other people -- maybe not as well-recognized...but the standard was extremely high.
Kuhn:Did this mean also that mathematics had considerable prestige in Italy? So good students would --
Amaldi:Good students would go into mathematics. For instance, in Pisa, there have been Dini, Bianchi, who were, certainly, no doubt, very good men. So the first thing that can be said is that the mathematics was always very, very good. This has been a very important factor and the situation in physics was not --
Kuhn:Before we come to physics, I’d also be interested if you’d talk a little bit about engineering and about chemistry, just for comparison. Then we can come to our central interest.
Well, I have the impression, it may be wrong but when I was young, chemistry was not on the same level as mathematics. There had been a very good tradition because for instance here in Rome there had been Cannizzaro [1826-l9l0] but he died, I think, immediately before the war. The man who is still in charge of the institute remembers Cannizzaro. We call him a (Lodovico) Zanchi. He was the child of the technician of the institute a long, long time ago. [The father] was a very peculiar man; the man was preparing the experiments for lectures and so on. The child and his father were living in the institute -- the old institute. The man grew up, has been since then always in the institute, and is the most interesting source of information that we had. Because he is also a very nice person, extremely nice person. For instance, he was the person who had essentially the greatest merit of having saved a lot of things because he was always -- He is a man of modest education -- the institute was the most important thing in the world for him. He is an extremely intelligent person. He has quite often seen something and he has put it away and said, “Maybe this is important. I do not know, but I keep it.” He told me a number of stories. He is now seventy or seventy-one or -two, so he remembers. So Cannizzaro was obviously a good chemist and this was not only in Rome, but also in other places. Then after the war, for a long period it was rather low, not very high.
Kuhn:There was not much chemical industry in Italy, was there?
Amaldi:There was not much chemical industry. In engineering there has always been a rather good tradition. I would say it was probably better at that time than now, relatively speaking with respect to old mechanics. I have the impression that our schools in engineering at that time were probably at that very high scientific level whereas now and in other countries the schools of engineering have stayed too much bound to a certain tradition which has started to be a bit oldish.
Kuhn:Were there then always a lot of students of engineering? It’s impressive how many of Fermi’s early students --
Amaldi:Well, Rasetti was a student of engineering, Segre, Majorana, myself, everybody. This is a tradition in this country -- I don’t know why. People are coming from a certain bourgeois level, an intelligent, good bourgeois level. (They thought very bright of the world during the high school.) The majority has always been going into engineering.
Kuhn:Rather than law or letters?
Amaldi:Oh yes, yes. In country this has always been considered very well. It is just a matter of prestige, I think.
Kuhn:What did the engineers then do? Did Italy then absorb all those people as engineers?
Amaldi:Well, yes. More or less.
Kuhn:What sort of engineering?
Amaldi:Well, everything, any type from construction engineering, transportation engineering, electrical. A great, great fraction goes into electrical engineering, now in electronics.
Amaldi:Oh yes. Now less. In the past it was a very important thing, now much less. And they worked terribly hard. It’s rather difficult to get a degree of engineering of this kind. I don’t think the organization is as good as it should be in the sense that it is a bit too old-fashioned now. It was not this way from the twenties to the thirties. But now they don’t completely keep pace, for instance, with the modern things in solid state physics.
Kuhn:Was it the sort of engineering training that stems ultimately from the old Ecole Polytechnique which puts great emphasis on mathematics and not basic science?
Amaldi:Yes, exactly. Well, the first two years were the same for physicists and engineers. Also now. They are almost the same. Now for reasons of numbers of students, we have separated, but, until two years ago, the class was the same for physics and engineering.
Kuhn:And that’s the prescribed curriculum. There are set courses for the first two years?
Amaldi:Yes. Exactly. For the first two years. Then for the other two years there are some set courses and some that can be chosen.
Kuhn:Is there an examination at the end of the two years that tells whether you go on?
Amaldi:No. (There are area examinations.)
Kuhn:Examinations in the individual subject?
Kuhn:So you must go to a course of lectures and take an examination at the end of it as in America?
Yes, exactly. In Italy it is done this way. Oh, now I suppose it is rather different from the German and also from the French. Here it is a slightly different tradition but it is not completely different. In science we have four years. In engineering -- five. But the first two years were alike for the physicists and engineers until two or three years ago. Now they have been separated because of the number.
Meanwhile when they were separated, there was made a difference in the courses, because for physicists we stress more certain subjects and for engineers there is a stress on other subjects. But basically the mathematics is practically the same, and is at a very high level -- too high. We believe that the teaching of mathematics is now a very big problem of discussion. We believe that the level, of mathematics taught even to the students of physics is too high.
Kuhn:When you say “high”, do you mean too difficult or too abstract?
Amaldi:Well, too abstract and too difficult. For instance, the honor students that have arrived here from the Liceo, the high school, are never taught that y is a function of x, the limit, and derivatives, as I’ve been taught in my time. Now they are taught in Italy with the theory of ensemble, in general and that a point ... in the space of n dimensions is a function of a point in a space of dimensions. And ever thing is taught in that style. Even to engineers. And always, at the end, they say, “Well, there are very special cases where n and m are both equal to one and you get to y equal to f,” And this is just the method. But if one reads the books from which they study, ne finds that they are very good. The standard is extremely good.
Kuhn:Let me ask two questions. First, how much have they had in the Liceo before they come to the university?
Amaldi:Well, in the Liceo they learn a lot of geometry, a certain amount of algebra, and trigonometry; they have not yet learned calculus if they come from the classical Liceo. If they come from what we call scientific Liceo, they will have learned also the elements of differential calculus.
Kuhn:Would they have had some integral calculus also?
Amaldi:Very little, very little. Frankly, we cannot count on that.
Kuhn:But they may come to physics or engineering either from the classical Liceo or the scientific, so you have to start.
Not only. And for the last two years we have a new law that we have made at the sciences also the people at the Dante Technical school, that there are (???). We have a third type of school which is complete in itself. They are, at the end, of the same age. They get a diploma as a technician in electronics. They can have a diploma in nuclear physics and so on. And among these people there is a rather good percentage of very, very bright people, I should say. And now for the last two years this has been a big fight and has been considered almost a revolution in this country. We physicists are very much in favor but many people thought that it was a terrible thing. They are now admitted to the university. These people do not study Latin... that’s the point. They have only studied Latin three years, and this kind is considered as a crime because they have not studied Latin at least eight years. You know this is one of the things for which some parties base their propaganda, just because there is a tendency to reduce, not to abolish, the teaching of Latin. And there are a number of people that consider this as a destruction of tradition and so on. While the result is that everybody studies Latin badly, if there are a few people who study it well.
Kuhn:This description you give of the mathematics courses as they exist now for physicists... this was not true when you were a student?
No, no. Maybe it’s because I’m becoming old, but because of the mathematics, being really very, very good, excellent learning and very reasonable, I find it today very good. And I had courses from Seven, Castelnuovo, Levi-Civita, and Volterra; I have followed the courses of all these people and they were absolutely, I would say, first-class courses. ...Well, for instance, Volterra was mostly classical mathematical physics -- vibration theories, integral equations, very classical. At that time he was rather old when he was a professor of mine; all these people were also very, very dedicated to this school, I’d say. They certainly had -- especially Levi-Civita. The career of Fermi was essentially helped --. There was a lot of opposition, even among physicists in Italy, to Fermi. It was mainly due to Corbino, the head of the department at the University of Rome, and Levi-Civita and Enriques. For instance, Levi-Civita was extremely convinced that Fermi was a representative of the --. He was a mathematician but he understood.
Kuhn:What sort of opposition? What form did it take and what was its basis?
Amaldi:It was that this atomic physics is not a serious thing.
Kuhn:Why? Why wasn’t it serious?
Amaldi:Because they were ignorant.
Kuhn:What would they say about it? It may be still something else, but I have one particular opposition in mind that I have run into talking with other people. In part, it can be that the break, the divergence from classical theory, but there is the other thing about its being too theoretical.
Well, you have just said certainly two of the main things. What people were the physicists of that time? The physicists at that time were rather not very great people. Some of the people were very intelligent and bright. Corbino was certainly very bright and he was an extremely good physicist. He had unfortunately stopped too early to make physics because he started to get involved in politics rather early, not direct politics, but cultural politics. Then he became minister of education and from minister of education on, he was very much interested in the production of energy in the country. So he was involved in planning electrical plants and helping. He was also Sicilian, you know. He was from (Augusta) and he was a completely self-made man. The father of Corbino had a shop of wine and he had various sons. One of the sons, I think the older, was a Caribinieni, and he was already gone up in the society. He had been an (???); that means he is not a pure Caribinieri; this is a slightly higher level. And he wanted his brothers to study because he thought that his brothers were bright. And he aid tremendous things for all these people. (Augusta) is a very small village, a really terrible place. Corbino was in some way sent to Palermo and he started as a boy in the shop of the institute of physics. It was very dramatic and he was extremely intelligent. It was a pleasure to talk with him of physics until the last year when he died. He used to discuss physics with Fermi and with all of us, asking questions because he had not so much time to read the papers but the questions were so intelligent, and objections were raised immediately on any question.
Kuhn:And he did then follow the most recent developments?
Yes, he was reading newspapers and talking, asking too. He was certainly a very extraordinary person. And he had done some very good things in the beginning of this century. He was one working on the Hall effect, he had made various contributions to try to see if the conduction was due to positive or negative carriers and things like that. He has contributed to the effect that is called (Xacaluso-Corbino). The Professor was (Macaluso) who was professor of physics in Palermo. And there they observed almost at the same time, immediately after the Zeeman effect, an anomalous rotation of the plane they were studying the transmission through a gas in the magnetic field and looking for Faraday effects -- and they found an anomalous rotation near the absorption lines and they published that. It was a very nice effect. Well, it was clear that it was just an aspect, so to say, of the Zeeman effect. But when they discovered it, it was recognized as an effect. So he was one of the first people who made quite an important contribution to electrolytic condensors.
Kuhn:How strong a theoretical, mathematical training and ability did he have?
Amaldi:Not very high, but decent. He met Fermi once because Fermi was a friend of Persico. That you should ask Persico, he knows it so much better then I. But he brought him to Corbino and Corbino immediately said, “Well, this is a completely different person.” And he said, “Well, this is the way to start to have real good physicists in this country.” But this you should ask Persico about, because Persico was there, and I heard from Persico and from Fermi, but I was not there, not yet there.
Kuhn:You sort of talked a bit about chemistry, mathematics, and engineering. Now come to physics which we’re doing anyway -- but we’re doing it at the top instead of at the bottom.
In the generation before, Augusto Righi in Bologna was considered a good physicist in short-waves. He had done a lot of very nice work and probably he was a good man, but he was a very bad character. There were some people that were decent physicists, I don’t say very high, but they would be a good standard, a very good standard. But they were usually bad characters in the sense that they did not want to have assistants or did not help the assistants or the young people to -- produce. They wanted to produce themselves and the assistants were just people to be used to help them, and not to have their own personality. So there have been some people like this. Majorana, Quirino Majorana, an uncle of Ettore, who was professor in Bologna too, was a very good experimentalist, but without any theoretical ability, of a very modest theoretical background. He had to take a position against relativity and he has spent the rest of his life making refined experiments against relativity. And it was amazing because he had given some of the best proofs of relativity. He was a very good experimentalist. He made refined experiments and everytime it went wrong and turned out exactly as it should be. Then he said, “No, now I understand why that is,and he started again. Later there was Corbino and he had done some good physics. Another man was in Pisa. The physicist in Padua was a very modest figure. In Bologna there was Majorana Quirino. In Turin there was a very modest person. In Florence there was a very open-minded and nice person but who was rather modest in production -- that was Garbasso. Well, Garbasso had Fermi and Rasetti in Florence because he thought these people were really the right position. In Rome there was Corbino and there was Lo Surdo. You know that Lo Surdo had discovered the Stark effect independently of Stark and in any case his method of observation was better than the Stark effect, the Stark method. I didn’t understand why it is not called Stark-Lo Surdo because actually both papers were published at almost the same time. I think it would be quite correct to call it the Stark-Lo Surdo effect. But certainly in our books it is called the Lo Surdo method because it is a very special method. He was a very intelligent man. He was an experimentalist without mathematical formation. He was against Fermi always.
Kuhn:Did you hear him talk against Fermi? I’m interested in the sort of thing he said.
Amaldi:No, no, I did not. Well, he had been my professor and I knew him. I had been on good relations with him but he knew that I was very much bound to Fermi sq he avoided taking sides. He was a much senior person than me so there was no reason to --. I don’t think he was against Fermi for any good reason. No doubt that while Corbino was certainly a great man Lo Surdo was a very modest person. Well, that’s my impression. Corbino understood physics very well. He had a general view of the right, a view that I should say most of us did not like so much. Almost all of the young generation thought that Corbino was too much a Siclian in a sense and he had a strange idea that we could not share at all.
Kuhn:I don’t know what it means to be “too much a Sicilian.” What sort of things did you not share?
Family relations; for example, the position of the women in society. His wife and daughter had to live in a certain way, in a way that was completely different. This may appear to be minor things and not important but they suggest a certain attitude. There is a full volume of the thoughts, political thoughts. These are four volumes of the work of Levi-Civita. [Mumbling too distant from microphone] These are interesting. These are political organization thoughts. He was in economics. He had a very clear position in economics. He had an influence on the country but he was in some way very classical and liberal but at the same time -- this is typical Sicilian -- he feared to solve problems. He would very seldom try a general, clear, democratic procedure. He was certainly democratic, no doubt. But he would try to get a good result by personal relations. If you had to call some person to a chair, and want to call the best man who exists, then one can follow two ways. One way, which I would follow, would be to say that this is the best man and try to convince people to get him the chair. But Corbino would apply practically the same method that one would apply to get the chair for a bad candidate -- just talking with the people and trying to convince, maybe promising something: “Well, if you vote for that, I will do that for you.” For instance, we liked him so much, but all these things we felt that we could not like. Well, he was really doing all his life the best. He was one of the best citizens that I can imagine but he was coming from Sicily, a little village of Sicily. So there was in him the idea that in order to get something you should use your personal relations. And he was extremely sceptical that there could exist a society where there are general rules that are decently applied. ... He thought that if you wanted to get something, you should have your friend in a certain position and go talk to him and convince him and so on. There is no other way you can do it. I think that’s a very strange attitude.
Kuhn:Yes, and it’s very helpful. When you listed these people who were the physicists at various universities, were there in general simply one man except in Rome?
Amaldi:One man. Except in Rome there were two -- Corbino and Lo Surdo. It was strange. After they came here they did not like each other very much -- they were not on good terms. I don’t know why. They were both Sicilians, because Le Surdo was also from Messina.
Kuhn:Would the professor generally have an assistant?
Amaldi:Yes, a few assistants.
Kuhn:Some of these would be able to teach also.
They were teaching. They were charges of a course. You don’t have this in the United States. Well, it was an assistant professor. For instance, after they had made (law) here, Persico was assistant of Corbino here in Rome. Fermi and Rasetti were both assistants to old Garbasso in Florence. After Pisa Fermi went to Florence. He went for some time to Rome and then he went to Florence. Corbino was much, much more intelligent than Garbasso and he was a better physicist and had a much stronger personality. He has been a very great personality. After 1931, 1932, he was the man who was assigned to United States to deal -- I do not remember the details -- with the United States for this certain agreement about the supply of various machinery for the development of the electrical industry in Italy. And, of course, in these things he was extremely clever. He could deal. He was extremely intelligent; he would do everything in the most clean and best way. But the method was that he did not believe that you could use normal methods. He was a very nice person, but using methods that we did not like.
Kuhn:Well now, why was it that this group, who after all were not great physicists, but respectable physicists, did not succeed in having a tradition like the German -- even the French tradition was not all that strong but in experimental --. Where did the students come from? Were there many students of physics?
Very, very few. Almost no students. In Rome there were almost no students of physics. This was because they were not attracted. That’s obvious. And as you’ve probably read in some place, Corbino was trying to get Fermi to Rome. He was in very good relation with Garbasso; they were talking together about what to do because they thought Fermi and Rasetti were very bright. They were really probably the only people who were conscious that something had to be done to change the situation in Italy. Corbino was certainly interested. I don’t know about Garbasso so much. Maybe that was different. But Corbino was very worried that physics in Italy was not a good matter. And something should be done. When he saw Fermi he said, “This is the man. We will start from this man.” And as you know, there were almost no students in physics at that time. He succeeded to get a chair, a Fermi chair -- that was something incredible -- a chair in theoretical physics in Rome in ‘26. Then he started to make propaganda so that Majorana and also indirectly Segré went over to physics. For instance, in my case, I was Corbino’s student in my second year. He gave a beautiful lecture. He was extremely brilliant, was full of spirit, very effective and full of imagination. He gave an example that made everyone laugh. Then he stopped five minutes before the end and said, “Now some of you should stop your study of engineering and you should go into physics, because now we have a new professor of physics here in Rome.” He was saying, “Fermi, he’s a very young man, but now we will get him. He is an absolutely new opportunity. This man is extremely intelligent. I can assure you that this is a man who can bring physics to a high level in Italy. In this moment the young people should go into physics.” Most of the people were not impressed, but some were attracted. He was extremely cautious of these things. Well, he understood very clearly.
Kuhn:Was any part of the problem of attracting physicists before this the fact that there might not be jobs for them? I take it that a mathematician who did not go to a university went to a lycee.
Amaldi:Yes, yes. Exactly.
Kuhn:Could a physicist not go to a lycee?
Amaldi:Yes, yes. But I know that in Bologna Righi was certainly one of the people who actually discouraged students from going into physics. So the people did not go. Actually Corbino understood this. There’s no doubt, And Garbasso too. Garbasso was a very nice person, but he was not a person with drive. A very, very short man. He was extremely intelligent and extremely quick. In a discussion he immediately understood everything and would just immediately go to the point. He was quite a remarkable person. He was very, very honest and very, very devoted to science and to the development of physics.
Kuhn:What were the relations of this group of Italian physicists with physics in Germany, France, England? I think of one particular story. We have seen a few Fermi letters and there is a very interesting -- just for this story -- letter from Fermi to Kronig, saying: “I hear that Bohr has just published a piece in Naturwissenschaften on the incomplete polarization of fluorescence radiation, but there isn’t a copy of Naturwissenschaften to be found in Italy.” Now, I take it this means Florence or in Rome. He was in Florence, but he’d just been to Rome. “Will you get me a copy, or at least let me know what the point of Bohr’s paper is?” The notion that he should have had trouble getting hold of Naturwissenschaften is pretty shocking and I wonder what --
Amaldi:I did not know that.
Kuhn:Well, you may easily yourself, when you started to study physics, have discovered the journals, or at least back copies of the journals -- all these subscriptions must have started.
Amaldi:I don’t know about the Naturwissenschaften, but the other journals are quite --. Was he in Rome at that time when he wrote to Kronig?
Kuhn:I think the letter was actually written from Rome, although he was still in Florence and I think this was written during a visit to Rome, but I’m not sure. It may have been written from Florence. It didn’t say that he didn’t have it at Florence; he said, I think, that it wasn’t in Italy. But in any case, he certainly had an opportunity to find out about Rome also.
Amaldi:I should say I do not know. When I started, the main journals were there. We never felt any difficulty about that, at least I don’t remember any such difficulty, so I cannot tell you more. I remember because when I finished at the liceo, I went in della (Mars) and I was rather concerned about whether to go into physics or engineering. I wanted to go to physics but I was rather worried because there was no position. My family said, “Well, you should be careful what you do. There is no position at all.” And they went into (san pito). That was about ‘26. Fermi was there with Kronig and I was sixteen and these two boys were 23, both. They used to talk physics from day till night and I could not understand almost anything, but I was so much impressed. I was following them all the time, going behind them like a dog. I have a very nice memory of this.
Kuhn:This is before you even got to the university?
Amaldi:Yes, before. And that gave a great impression to me, you know. And Kronig, of course, was just a hero. Well, I was just sixteen years old, following behind these two people and they represented the best thinkers and it was true. Kronig was an extremely nice person, it’s true now, but when he was 22 or 23, he was an extraordinary person. He was a good friend of Fermi. But I did not know of that letter. I don’t remember that.
Kuhn:Did you all try quite hard to keep up? Did Fermi emphasize keeping up with the journals? Did you read the Zeitschrift fuer Physik?
Amaldi:Oh, regularly, regularly, but later. At that time the most important journal was the Zeitschrift fur Physik, no doubt.
Kuhn:What else would you have kept up with regularly?
Amaldi:Proceedings of the Royal Society, The Physical Review.
Kuhn:Anything from France?
Amaldi:Comptes rendus, but there was not much. I would say the most important were Zeitschrift fur Physik, Physikalishe Zeitschrift, and then also Naturwissenschaften, but later --
Kuhn:How about Annalen der Physik?
Annalen der Physik, yes, too. And then Comptes Rendus, Proceedings of the Royal Society -- always reading that -- Physical Review. Those were the journals. No, I would say when I got my degree, when I went to Leipzig a few years later, I did notice a striking difference. There was Heisenberg, Hund, and Debye. I was working with Debye and I met at that time a number of people like Bethe, Bloch, Teller, Placzek; I met a number of people -- Weisskopf for the first time. Well, there were many more journals in the library. I don’t remember that I noticed that we lacked journals. It was quite clear there in Leipzig that there was a very well-established tradition while in Rome there was, in some way, a new tradition starting -- that had roots in the past. There was not the continuity that was in Germany. There’s no doubt. That made a very clear impression. But not for the journals, I should say. There were more means in the laboratory, but not a tremendous difference.
Kuhn:When you say you had the sense of a long tradition in Germany as compared with a new one --
The number of professors -- is a measurement of the institute; the measurement of the institute was completely different; well, there were Debye, Heisenberg, Hund, Karolus, there was somebody else, these four or five professors. All active, all producing, and all with a number of assistants, a number of students. Heisenberg was doing at that time ferro-magnetism and things like that and Debye was doing diffraction of X-rays in liquids. Well, there were various chapters, very important. While in Rome Corbino was not working anymore; Lo Surdo working closed in his room with an assistant who was chosen from rather modest persons. We did not understand why he chose such a modest young man. The only person that was really doing anything, teaching, working, teaching two or three others to work, was Fermi, For the experimental physicists, Rasetti was the person who was working and teaching.
Kuhn:What was Rasetti’s position then?
Amaldi:At the beginning he was the first assistant of Corbino and then, after two years, Corbino succeeded in forming a chair...a little chair of spectroscopy...one or two years later. So from a certain moment on, there were four professors in physics in Rome. And of these in practice two were really active and the others were not.
Kuhn:This is clearly the beginning of the change with Fermi’s appointment in ‘28, bringing Rasetti... Was there also money to get equipment?
Amaldi:Not much, but I think there was enough money to get equipment.
Kuhn:I know some of the introductions speak of equipment problems.
Amaldi:Yes, I think there were equipment problems but not --
Kuhn:Were they problems of money or the lack of technicians?
Amaldi:Well, there were technicians at the institute. They had been spoiled in a certain sense by the fact that there had been a kind of interruption in the work, so they had not worked very much. So the method was to convince them to work -- very nice people, but not working very much they were not as good as they could have been, So it was not very (brilliant) but it was still possible to go on. And for the money there was not much money but especially through the council of research some money came and it was possible to do some work. There were any amounts of money [noise].
Kuhn:Going back just a bit in your own physics education I have to keep having to remember that it’s a transition period what books were particularly influential? What did you learn your physics --
Amaldi:I remember very well that I studied for instance, Joos, Einfuehrung in die Theoretische Physik. The Planck books.
Kuhn:All of them?
Amaldi:Yes, yes. The Planck books were a kind of Bible for us.
Kuhn:Did Fermi direct you to those?
Amaldi:I think probably so, I don’t remember.
Kuhn:I’m terribly interested in this because the people in Germany have told me repeatedly that although they used Planck’s Thermodynamics, they didn’t like the other ones.
Well, we all studied Planck’s thermodynamics, and we liked even more Einfuehrung in die Theorie der Waerme, the second book. It is shorter, and is better than the Thermodynamics. Then I think that I studied the Optics of Planck, physical optics. Not (here). No, I studied, but not completely, the Theory of Electricity. But certainly we have studied at that time Joos,we studied Planck, we studied all the papers of Schroedinger. Then we studied papers. Essentially, Fermi was not very much in favor of books. You know that Fermi had never a book of physics in his house. He was not impressed. He wanted to consult a book but he did not want to read it. He always thought it was wrong. One should hear what somebody has done and then try to make a gain on it. That was much better than to read on it.
Kuhn:He himself read many books in the earlier days.
Amaldi:Well, it was during the high school. Then essentially we read the journals. We really learned more by reading the journals. Well, for mathematics we had a really very good teacher. There’s no doubt. So we had our courses.
Kuhn:What courses? How much mathematics would you then take?
Amaldi:Well, during the first two years -- and now it is still the same -- we had two years of differential and integral calculus, two years of geometry, and one year of rational mechanics. So we had five courses, essentially in mathematics in the first two years.
Kuhn:How often do they meet?
Amaldi:Three times, sixty lectures per year roughly. So it was quite a good curriculum.
Kuhn:That’s a lot. Tell me what physics you would take?
Amaldi:Two courses at the same time in physics. Only two plus laboratorium. (One here in the first and the second year -- and here we have sixty per sixty.)
Kuhn:And they would combine. You don’t have the separation in Italy between theoretical physics lectures and the experimental physics lectures. There would be one course for two years?
Yes, exactly. Then in the third year we had -- I had a course of mathematical physics that was given by Volterra on elasticity vibration but was essentially a course on partial differential equations. The subject was elasticity and also difficult things. For instance, we spent two or three months integrating the problem. It is a not very well-known thing but very elegant. The problem of the deformation in a sphere can be treated exactly for any kind of forces applied on the surface of this sphere by solving the ‘delta four’, that is, the sum of the three fourth derivatives. And you have a problem of a differential equation of fourth order. And Volterra, for instance, has taught us to solve the partial differential equation of the fourth order. I was used to go With Emilio Segré to this lecture. Segre used to sleep, I remember. I did not like this. He felt it was a bit boring. I found it was rather interesting because I’ve never seen anybody in my life solve exactly a partial differential equation of the fourth order.
Kuhn:Neither have I.
Amaldi:I have notes on that. Volterra was giving this thing, for instance, with a full -- everything was moved in a very -- I was very. So the problem of elasticity was done at a very high level. I should say I’ve never seen this method used by other people. I have never seen it in a book. And it was very interesting because it is a kind of a Laplace equation except with the fourth derivatives of the displacement with respect to x, y and z. Another course in mathematics was mechanics -- theoretical mechanics applied to astronomy problems, things like that.
Kuhn:Did you get then things like Hamilton-Jacobi technique in that?
Amaldi:Oh yes, yes, yes. This was done very well.
Kuhn:I ask you something that you may not know first-hand, but do you think the Hamilton-Jacobi techniques had been part of the Italian curriculum for a very long time?
Amaldi:I think so.
Kuhn:You see, they were not part of the curriculum in Germany until atom mechanics.
Amaldi:Persico maybe can answer you. Because you know that Persico was an assistant for one year. To Levi-Civita. I don’t know if you know that Levi-Civita has published at that time, This was in ‘22, ‘23, (Maybe the best was done by his students.) He has published a book on the absolute calculus. Tensor calculus, we say today. This was written by Persico. It was written on the volume. They were lectures given by Levi-Civita. Persico, I think, was a student of maybe it was just a (piece) of time but Levi-Civita was giving a course on these things. Well, today nobody would call it absolute calculus.
Kuhn:I think the book in its English translation is called the absolute differential calculus.
Amaldi:Well, it was written by Persico. Persico was an honor student and very, very exact. He went to these lectures, collected notes and then he wrote. Then, I think, Levi-Civita read them again but it was written by Persico. So I think you should ask him. When he was in the third year...the year that the first papers by Schrödinger came out -- immediately Fermi taught us the Schroedinger equations. Then we had to study the Jacobi method but I do not know if -- My father was a mathematician and he had written when I was a child, a book on mechanics with Levi-Civita. He was a great friend of Levi-Civita. Then there was a big part of the volume on the Jacobi method and I studied that when I was very young, but I do not know if it is by personal chance, just because it happened to me to be grown up in a certain environment. So I cannot state if it was a general thing. I was too young to judge in these things.
Kuhn:Tell me about reading the Schroedinger papers, having Fermi teach them to you in ‘27. In the first place, was he already altogether convinced.
Amaldi:I do not know. He was impressed, was interested to learn and started immediately also to --. But I do not know if he was really convinced.
Kuhn:When he first talked to you about those, was he using Schrodinger’s own interpretation? Schrodinger thought at first that the wave functions were the real thing. There was no probabilistic element. In fact he thought that the emission was due to an interference between Schrodinger functions for one level and one for the other.
Amaldi:I don’t remember with certainty. You see, I was very young. This was the first thing that I learned. Certain things had made a great impression on me, certain things I did not appreciate or understand enough. Maybe Rasetti knows that better. He had always a much greater maturity when this happened, so he probably could give you a better account. I’ll not dare to say. I remember that he taught us the Schroedinger papers, but he never taught deeply, he taught us the ideas, but always he was doing something different. He never tried to reproduce anything. That was very typical.
Kuhn:Were these in lectures or in seminars?
Amaldi:No, just sitting at a table and we were sitting around. I remember
Kuhn:Did you take notes?
Kuhn:Have you still got those notes?
Maybe. I’m not sure. Probably I have, because I kept all these notes. But I do not remember of this particular -- Then he said, “You should study.” I remember in the evenings, I, and, I remember, all the others were just trying to learn the papers of Schrödinger. So we have spent a lot studying the paper of Schrodinger, then the paper of Heisenberg and immediately we started to study. We were students and he intended that we study these papers. He has talked to us, but he never exactly made the same as in the papers. He was doing it a different way. Always. He would say, “Heisenberg proves this and this. I will try to do it in a slightly different way. And then he was trying. Because he was really -- When he was lecturing about things he had not prepared. He was just trying. I remember Rasetti, Segre, myself, and Majorana were sitting around the table asking questions. And he was saying, “Well, we try to do that. Now we try. ‘ He was going on, and we were just sitting around and asking and making remarks.
Kuhn:He did ask you to study the Heisenberg papers as well as the Schrodinger papers?
Kuhn:But I gather that he himself took the Schrodinger approach much more seriously. But he felt he must learn the other too.
Amaldi:Yes, yes. But I think you would say that he was thinking more seriously about the Schrodinger approach.
Kuhn:How about Dirac?
Well, any paper of Dirac -- as soon as it arrived -- Fermi was immediately looking into it. There was something very different in the mind of Fermi and Dirac. He had probably some difficulty to follow Dirac. He said so. He used to say that. This was one of the reasons that he produced many of his papers. He would immediately say, “Well, I understand that it should be right, but I don’t understand how he does it.” Then he was trying to do it in a different way. For instance, all the electrodynamics was done for this reason. He used to say, “I don’t understand why Dirac does it this way. It seems to me that it is not very natural. I don’t like this way of presentation.” He had the greatest consideration of Dirac but the approach was different. Then he immediately tried a different way.
Kuhn:Did he also follow closely the Jordan papers?
Amaldi:Yes, yes, yes. All these papers were read and studied and discussed. No doubt. All these papers were studied very, very, very seriously. But we were more studying the papers seriously than Fermi. Fermi read the summary, looked here and there and then did not worry. Generally, he wanted to try it himself. In this manuscript at the Domus Galilaeana in Pisa there is a number of things re-made by Fermi. Just the papers that came out and he tried to --.
Kuhn:Get the results himself, Just a little bit on from this when you begin now to get out towards your own work and this really gets to be the very beginning of the nuclear physics period, when does nuclear physics start? When does the transformation to nuclear physics in Rome start? I don’t mean when do the papers on nuclear physics begin to come out, but when is it clear to those of you in the group? I think somebody -- perhaps Segre -- speaks of there having been long arguments and discussions of that.
Amaldi:Yes, yes. Oh, there were long long arguments and discussions. At a certain period we were all working on the Raman effect -- that was more or less Rasetti, Segre and myself; then we were working also with Segre in other spectroscopy work. But --
Kuhn:The statistical model.
Well, no, what we were doing was studying the shifts of lines produced by foreign gas introduced at high pressure for very excited --. With Segré we were studying very excited states. You can have such excited states that you can have an atom with a dielectric gas, with another gas inside. We had studied the absorption spectrum of sodium or potassium -- these so excited states. These excited states had their total quantum number from forty on, and then the dimension is so big that you have a hundred thousand atoms of a foreign gas inside the orbit of the electrons. Then you have an atom with a dielectric constant, and it behaves in a very strange way. It’s a very nice thing. (There were two effects in these things.) There is an electron. The electron is still bound, but if you go to a very excited level you get electrons bound with 1/10 or 1/100 of an electron volt. They are very close to the ionization. So they are very, very soft. They are almost unbound. Then you have two effects. One, the force is decreased by the dielectric constant of the gas. The other is that these electrons, very, very (slow) electrons going around as collision actually with the atoms of the foreign gas. So this changes the energy of the level. And this gives a shift and Segrè and I had found these things -- found experimentally these things and Fermi then had written a paper that I published here in which he gives for the first time -- he introduces the scattering length. That’s a very interesting thing because that was used later for neutrons for slow neutrons, but this was done for slow electrons. The shift gives the measure of the Ramsauer effect cross-section. This was one of our last papers in spectroscopy. By then we felt spectroscopy was no more an exciting thing. We thought that quantum mechanics is being -- I want to show you because there is a famous figure used in all books of nuclear physics. Well, here. You see, this paper, ‘On the displacement by pressure of --.’ We had observed this effect... Now here he gives this figure. The first time it was done -- this figure in which is defined the scattering length as a limit of low velocity when the wave length is infinitely long. And all the materials for slow neutrons contained here long before the neutron was discovered. That’s a very interesting thing. Well, it was done for slow electrons because the situation is exactly the same. This electron with 1/100 of an electron volt of energy, or 1/1000 and then that electron has a wave length that is infinite with respect to the measurement of an atom. And this is a rather interesting paper. Then, as you see also here, this was the last thing that was done and started immediately with the neutrons. But we had a lot of discussion, as you say.
Kuhn:Did everybody agree that the time had come to move?
Amaldi:Yes, more or less, more or less. Because of this decision -- I think it was in 1931 when I came back from Leipzig--it was felt that it was not wrong to go on in X-rays or in other things that were studied in Leipzig -- we discussed this for a long time. ... Everybody was trying to get into the discussion. It was clear that all these things were important, but were not new, were starting to be less exciting. Then neutron physics was the right thing to do. Then Rasetti went to Berlin to Lise Meitner’s place. He said, “I will go there so I will learn some of the new techniques, also chemical techniques.” We needed to learn some chemistry, at that time.
Kuhn:Chemistry was not then part of a physicist’s training?
Yes, we had a general course in chemistry, but not much. Then we started a seminar. Every week we had a meeting. I had started to read, I should say, in Leipzig -- the last part of my stay -- I was for one and one-half year in Leipzig -- at the end, in the evening, I started to read the Rutherford book. Then every week in the seminar I came and said what was in one of the chapters. We were to do all the Rutherford book. I was reading and recommending and Fermi was doing some parts and he was starting to make theories. He started immediately to apply. Of course, we knew the theory of Gamow, but he was trying to compute cross sections and things like that using ideas of quantum mechanics in nuclear physics. But I was reporting every week one chapter from the Rutherford book. Then Fermi -- Then Segre was at that time in Hamburg with Stern. Rasetti was with Meitner and that winter, Fermi and I built together a cloud chamber, but that has never been published because there was nothing to be published. But we had spent most of our time during this winter building a cloud chamber and we started to look for particles. Then Rasetti came back next year and he constructed a much better one. He had learned a lot with Meitner and he started to build a better one.
Kuhn:Were all of these trips, Segre to Stern, you to Leipzig, Rasetti to Meitner, were all of these done deliberately as part of the change, so the decision was made even before you went to Leipzig? The decision to switch to nuclear physics.
No, no, no, no. Well, I went to Leipzig and I don’t remember why. It was an extremely good place. Probably also Segre went to Stern because it was an extremely good place. But these trips -- while I wouldn’t say they were mistakes -- were not planned. Fermi was encouraging us to go to other places. The group in Rome was so small that we needed to go to other places and talk with other people. I remember I asked Fermi and Rasetti about Leipzig and they said, “Well Heisenberg is there, there is Debye and so on.” And I remember that the idea was that since Heisenberg and Debye were there it was a good place to go for a young person. There was a lot of discussion with Segré as to where he should go. They said, “Well, after all, Stern is a great experimenter. You go to Stern and you will learn a lot.” That was true. We were all working something that -- Well, all we got was (maxima; we had to change too.) So we exchanged letters; in summer 1931, I think, we went together to Norway, Rasetti, Segré and myself. We were in different places but we joined and went together. We were discussing a lot about these things and then talking with Fermi. Then we said that it was better that we concentrate our effort in something that is in so primitive a state that there is a lot to be done. That was quite clear. And not resist. In (???) and (???) there was so much done that we were always in some way behind.. That was very clear.
Kuhn:Nobody went to Goettingen to Franck. Fermi had --
Amaldi:Fermi alone. But Fermi had not found himself very well in Goettingen. You know that.
Kuhn:I know that but I’m terribly puzzled still to know why;
Amaldi:Well, maybe Rasetti can tell you better than I because maybe he knows better than I. Fermi did not feel himself well with Born while he felt extremely well with Ehrenfest. He had the impression that the Germans -- this is what I understood, maybe I’m wrong had a certain way of teaching, a certain way of thinking, a certain way of studying and if somebody was coming from a different place with different training he was not considered to belong to the same (Kaffee).
Kuhn:Was this the Germans or was this just Born?
Amaldi:I don’t know that. For instance, when Fermi went to Ehrenfest, he always was speaking of him with the greatest consideration and he spoke of his sympathy with the Dutch group. He found these people were so clever and so open, so to say, to accept people coming from a different tradition. While he said that in Gottingen if you did not belong to a certain tradition, to a certain kind --. Myself, when I went to Germany, I found many things very strange. But that did not happen to me when I went to Great Britain.
Kuhn:What sort of things?
Well, for instance, it was quite common between the young people -- well, I was 22, 23, I went with this young German, mostly this young German. We went, maybe to ski or to swim, so we were talking together. But he frequently said, “Oh, well,” -- this was the same with Heisenberg -- “the system that you use in Italy to ask the student to give an examination for any course is just the system that should be applied when the professor and students are bad.” I was very astonished at this statement. “Because if the people are good there is only one examination.” I found that a bit strange. Think of this time -- it was true that German physics was very, very good, but they were very conscious of the tact that they were the good physicists and the others were bad. Well, this was my personal impression. I did not ask very much about that to Fermi, but I got the impression that he felt that they were very conscious of their capacity, of their preparation, of their ability. All others were just coming there to learn from them. And it was true. But they tried to make a point of this, to stress this point, It was certainly not so in the Ehrenfest surroundings. I met Ehrenfest myself and he was an extremely nice person. Very, very nice. He knew a lot and he was a very good physicist but the attitude was different.
Kuhn:When you talk about this planning in Rome to do nuclear physics, one thing puzzles me. There are a whole group of you now of younger people. There are now four chairs in Rome. Could you plan to stay on? Could you look to yourselves all as members of a long-term group in Rome?
Amaldi:Oh, we did not worry about that. We felt that
Kuhn:What sort of jobs, what sort of appointments did you have?
Amaldi:We were assistants.
Kuhn:Could you live on the assistant’s pay?
Amaldi:Well, I could live on it. My wife was also working and with the two salaries we were living decently, I would say. We were not --. Well, it was very modest.
Kuhn:Because elsewhere people would be assistants for a while but would pretty soon want to be out somewhere else, beginning to get higher pay.
Amaldi:Oh, that I remember very clearly. I am speaking for myself. We were not interested at all in that period to make a quick career. I was not at all interested and this was more or less the general idea. We felt it was so nice what we were doing, so agreeable, so wonderful, that there was no reason to go away to get a better position. I remember this because on this we had very long discussions. One of us said, “Well, after all, what is the reason to get a better position to go in a place where you don’t work! Here it is so nice. This is the thing that we should do. This is where you live and work.”
Kuhn:Did the wives bother about that?
Amaldi:Oh, my wife, very much. Oh, yes. My wife was one of the students studying astronomy. She was one of our students. She was completely in favor. There was no question about it. This was the thing to be done. That was quite clear. Then you know you don’t think so much about the future.
Kuhn:You were very wise because I can’t think of a similar case elsewhere where a group of people, all at a relatively junior level and with no real room at the top where they were, staying together, working together as a group for so long.
Amaldi:Yes, yes. But this was many years. We were so convinced that we were doing nice things. That’s the point. Well, I should go on doing nice things.
Kuhn:I just want to put into the record that Professor Amaldi and I checked the library and the beginning of the Naturwissenschaften subscription at the Instituto de Physica in 1926. It must have been Fermi’s first act upon coming to Rome.
Amaldi:Yes, you should ask Rasetti. Maybe he will remember that. I don’t remember it.
Kuhn:But your impression would be that there were many other journals that have been here all along?
Amaldi:Most of the journals were here, I should say.
Kuhn:Certainly that is a very long and impressive run of Poggendorff.
Amaldi:Oh, but that is the same for all other journals. I didn’t go around because there is another big room. The library is quite adequate, I’d say. We got back Comptes Rendus, Nature, Proceedings of the Society, Physical Review and see that they have been there from the beginning.
Kuhn:You think the same would be true of Zeitschrift fuer Physik and the others?
Amaldi:Oh yes, yes. Well, if you want, we can go in just a moment and see. And I think they’re all --. Maybe Naturwissenschaften was not there.
Kuhn:Obviously it was not. One thing that occurs to me -- you know we were talking about the transition to nuclear physics. [An account of the Domus Galilaeana and the Museum on the History of Science in Florence is here omitted]. When one does get into the period now very much of your own work -- we’re not going to be doing nuclear physics, on the other hand, we can’t quite ignore the neutron, the positron; the neutrino I’m not so sure about. But those are three developments right in the early thirties with which quantum mechanics is still much concerned.
Amaldi:You don’t ignore quantum electrodynamics? And I wonder if you can ignore the theory of beta decay. It is the first example in a certain sense of field theory outside electrodynamics. This is a development of quantum mechanics. That is the point. I wonder because all the present theories of nuclear interaction are extensions and variants of the idea of Fermi. For that, there is a very nice introduction here made by Rasetti.
Kuhn:I’ve read that, with considerable interest -- No, indeed it’s just that series of developments that we cannot ignore and it’s also those which fall very much within your own working experience with Fermi. I wondered what recollections you might have of this. Of course, I will talk with Rasetti also. This is really ‘31 to ‘34 and it’s a period of great activity here, it’s a period also in which certain of these things are coming from outside. I wonder, for example, how the neutron was received here?
Amaldi:Oh, I’ll tell you. When the paper of Joliot arrived in Rome in January with the Comptes Rendus and the paper of Chadwick had not yet appeared, we all very much interested. But Majorana said, ‘How stupid of Joliot! They have not understood that this is the neutron.
Kuhn:Just like that!
Amaldi:Exactly. “How stupid they are! They have not understood. This is obvious. These gamma rays make no sense in a nucleus. This should be the neutral particles.” He thought -- Well, we used the word ‘neutron’ because, you remember maybe, the idea of a neutron was suggested by Rutherford a few years before in order to explain the anomalous scattering of alpha particles. Gentile, another young man of our group, a great friend of Majorana, had done some calculations trying to introduce in quantum mechanics the effect of neutral particles moving around the nucleus. He had taken the idea of Rutherford and he had done some calculations. So the idea of a neutral particle, suggested by Rutherford, was discussed in the institute. But since that time, as I told you, we were studying very carefully the book of Rutherford. We knew it rather well. We discussed, we were just reading everything, and even looking in the table of measurements. [interruption to change tape]
Kuhn:You were talking about the way in which you had read the Rutherford.
Well, that I read very carefully in the sense that we had looked at tables of measurements and said, “Why do they get this (out.)” And we knew that. The comments of Majorana were really quite interesting. He would say, “Well, how stupid they are!” This was not because they were stupid, because they were very intelligent people -- it was just his way of expressing himself. “They don’t understand! This should be a neutral particle. There’s no sense to think of gamma rays of 50 Mev. There is no sense to talk of gamma rays of 50 Mev. This should be neutral.” Then we saw the paper and everybody was very, very much excited and Fermi immediately said, “Well,” -- then came immediately after, the paper of the Joliot with the radioactivity produced by alpha particles -- “that obviously should be done with neutrons. Neutrons should be much better than this.” And then he immediately started to do these experiments. Then at that time when the experiments were made, Segre and I were in Rome and we were helping him to make the counters and to do these things. Rasetti, in this moment, was in Morocco. He was invited to go to Morocco and we wrote to him there and he came back some few weeks later. But in that moment we started immediately. What was rather typical was that we, very much more than the average physicists that we knew, were aware of the necessity that we could succeed to get something interesting only if we were in some way organized. Perhaps because we were so different. We were all of extremely different temperament with different ideas and we were not very much alike. We had in common the idea that we could have done something if we were in some way organized, doing things with some planning. And immediately everything was planned in a rather efficient way. For instance, Corbino was not of this opinion. Corbino was really astonished, and in a certain sense almost, he was very happy about that. He was extremely satisfied, he was so glad that -- He was extremely nice to all of us. For instance, here is one of the points in which we were very different. Corbino felt the important thing was to show that one could produce a few radioactive elements by neutrons. That was all right. There was no sense for him to try to do a systematic study. And we were of the completely opposite opinion. We thought that now one should study each element in detail because the best things will come out, study each element and try to make a kind of a new systematic work of radioactivity. But this was a very great difficulty; on this idea to find something to do a systematic work. I recall when you have a field and the farmer plows -- we used to say we should plow this thing completely not leaving any corner out.
Kuhn:Fermi felt this way also?
Amaldi:Oh yes, yes. But all of us felt this way. The important thing was to plow the field completely and to the limits of our capacity; we should not forget anything. We should try to do this. And [Corbino] would say, “Well, you do what you want. I do not understand. Why do you do that?” He was astonished in that sense. He found that you had to do brilliant things and not try to plow. That we found was strange. And then we started and it was right to try to do as much as possible; it was quite clear that it was a completely big field, a great field, not just a --.
Kuhn:At the very start, did everybody immediately take up the suggestion of Majorana or were there some people who felt that it isn’t a neutral particle?
Amaldi:No, nobody took seriously the suggestion of Majorana. I don’t think we took it seriously. No, no, Majorana said it then, but everybody said, “Ha, ha.” We did not take it seriously.
Kuhn:So it was really only after Chadwick --
Yes, no doubt. After Chadwick we started to take it very seriously, and after Joliot. No, when the paper of Chadwick came out, we were all convinced. And we said, “Look how quick Ettore is -- he has understood before Chadwick.” We were increasing our admiration for Majorana. But we did not, at least myself, maybe Rasetti, but I don’t think the others -- I do not remember if Rasetti was present at that time. I remember quite clearly. But I don’t think we took him seriously. Well, we were saying many things. Well, it was a live place. The people were saying things and joking. This was the great difference between the character of Fermi and probably of the Germans. I certainly noticed it from Rome to Leipzig. I found a tremendous difference. We were so Joking all the time and never taken seriously what we were doing. Now, we thought it was nice, but not saying, “Now, we are doing --.” Well, we found it was a good thing to laugh about, to joke and to make nonsense and we were mixing all that. There was a completely different atmosphere in Leipzig. People were extremely serious and had a certain style. They were conscious that they were scientists in an old tradition and so on. I think this was one of the differences between Fermi and the Germans. The other one was that, in a certain sense, he was much less philosophical and less mathematically minded, even if he knew a lot of mathematics. Fermi had a very high knowledge of mathematics. The philosophical attitude of Fermi was essentially that of a naturalist. He was interested in nature and in phenomena and explaining phenomena and trying to measure. He did not like to discuss philosophical aspects. This was completely different from the Germans, I think.
Kuhn:Yet he did do that early paper on causality?
Amaldi:Yes, but he was not interested. Well, Persico can tell you about that. He was really interested in what happens, how do we explain how we connect this fact and this fact. That was exactly -- he was always like that.
Kuhn:Did he worry before the neutron about the problem of the electron in the nucleus?
I don’t remember. Oh yes. Bohr was in Rome, I remember; I was quite young. He was just discussing the problem of the alpha particles and he mentioned the alpha particles and the electrons inside and so on with four protons and two electrons. This I remember very well and it was discussed but I don’t think that Fermi was devoted especially to that. Maybe you remember that at that time Rasetti had done the experiment on the nitrogen 14 molecule -- the Raman effect -- and he had shown by the alternating intensity of the rotational spectrum that the nitrogen 14 should follow the Bose-Einstein statistics. This was, I think, in ‘28. I have the plates. I have here a number of plates of these things I have put here. [Amaldi goes to find them] I asked Rasetti to --. Actually this has actually been done partly in Pasadena because he went with a Fulbright to Pasadena and partly made in Rome. Last year I asked Rasetti to put in order my papers because I keep them here in a very messy state and this here is an explanation of this --. He has given me also --. Now this was not (intact), you see. This could not be explained this was a great difficulty -- this work was very difficult. You could not explain with electrons because if you had 14 protons and 7 electrons, you have 21 Fermions and they should obey the Fermi-Dirac statistics. Or this paper, Pauli said, “Rasetti is wrong. He has not counted the right lines.” And there was a lot of discussion because Rasetti said, “No, the nucleus of nitrogen 14 is a Boson.” And on the contrary, Pauli, said something similar about spin. You know he was always rather, well, negative. Well, he was a great man but he had this negative attitude.
Kuhn:Where did Pauli say this?
You should ask Rasetti about that. It was very much discussed in Rome. Well, with the neutron, nitrogen 14 has 7 protons and 7 neutrons and you have an even number of Fermions, which should obey the Bose-Einstein statistics. But this was the first time a nucleus was proven to follow the Bose-Einstein statistics and this was the model at that time that he had to follow. I think that either Heitler or Herzberg, one of these people, took very seriously this proof of Rasetti. You ask Rasetti because this does not appear here, of course. But when Majorana said that, I don’t think we took him seriously. After the paper of Chadwick it was taken seriously, and immediately was understood. Now, we see the paper of Chadwick was January, ‘32, I believe. And this was published in 1930 and the problem remained unsolved. Either people had confirmed that the experiment was all right but --.Then it was immediately understood. But when Joliot found the radioactivity by alpha particles, we were ready, in a certain sense, to jump on nuclear physics because we had started two years before to play with cloud chambers, to make counters, to make everything, so we had really the techniques. We had not yet found any problem to work on. Rasetti and Fermi had made a gamma ray spectrometer and they (described) with a crystal and there observed the gamma rays of mesothorium, these gamma rays of 2.6 Mev. But that was the only piece of work that had been done in nuclear physics. Then came out the paper of Joliot and Fermi immediately started to look for the radioactivity. He found it and then everything started. But this was just immediately after Fermi had written the paper on beta decay in December.
Kuhn:The beta decay paper is later.
Amaldi:This is made maybe before. And I will tell you another story. When he wrote it was December ‘31 or something this paper on the beta decay. That’s very interesting. Then he sent it to Nature. Nature refused to publish it.
Kuhn:Do you know anything about what they said?
Amaldi:They said it was too mathematical, too disconnected with actual physics. Something like that.
Kuhn:How did Fermi feel about that?
Kuhn:This was important to him, this rejection?
Amaldi:No, no, it was not important. He said,They are stupid. They were so stupid that they could not understand.” He sent it to Nuovo Cimento and at the same time to Zeitschrift fur Physik.
Kuhn:That paper was published in ‘33.
Yes, and that was December,‘32. [Amaldi looks up “Tentativo di una teoria dell’ emissione del raggi ‘beta’” Rec. Scientifica 4 (Dec. 1933) pp. 1491-95.] Well, it was published in ’33. Between Christmas and the New Year we went to ski in (Bargarvina). That was at the end of ‘33. Well, he had sent this Vorlaeufige Mitteilung to Nature in English. And they said that it was too mathematical abstract and had nothing to do with physics. Well, then he said, “Well, O.K., I’ll publish in the Ricerca Scientifica.” Then he sent it to the Nuovo Cimento and the Zeitschrift Fur Physik. Well, at that time I remember that we were to ski in the Dolomites in (Bargarvina). He knew about the paper but he had not shown what he had done. He said, “I have done the theory of beta decay.” Then I remember that one evening we went in his room and we were all sitting on his bed, I think Segre and myself were there. I don’t think there were others. And I remember he was sitting there with a piece of paper, explaining to us what kind of theory he had tried. I remember that we had a tremendous difficulty to understand how…We were very impressed about the fact that he had introduced the idea that at a certain moment the neutron is transformed into a proton and comes out two other particles. He had described this interaction, as a constant multiplied by the corresponding wave function. This was the first time he had written this type of interaction, of local interaction. And I remember quite well that he was writing on the bed and we were sitting on the two sides. And he was explaining to us and he said, “Well, you see this should be so. The simple thing to do is to take a constant and so.” And we could not understand. “But why?” I remember that very well. Then the paper came out in the beginning of ‘34 but this paper had not yet appeared. That came out after that of Joliot, And Fermi immediately started to do the experiments. So the paper on the theory of beta decay came out after the radioactivity by neutrons was discovered. We should see what month it is. It is more or less after --.
Kuhn:What happened about the positron? That comes very quickly after.
Yes. Well, we were very much impressed; we were, of course, in a connection that was not very tight, because--but some connection with (Occhialini). He was working in Cambridge with Blackett at that time. I don’t know if you know that (Occhialini) left Florence and said, “I go to Cambridge to work with Blackett because the way of using the cloud chamber is by triggering with counters.” This is due to (Occhialini).
He was very clever with the counters. He was in Florence. And there is (Bernardini). He was there with(Occhialini) at that time. At that time (Occhialini) left Florence with the idea to go to Cambridge because he knew counters and said, “I want to play with counters in connection with the cloud chamber and then study cosmic rays and learn about triggering the chamber. The very thing to do is to trigger the chamber with counters.” So this was the start of that. But we knew that and we found that we had so much involved with neutrons, I should say, we---.
Kuhn:Was it bothersome to have another particle? I know in some places people definitely did not want to believe this.
No, no. We believed it. I remember Fermi found that it was nice. Did you see how he finished his lectures on electrodynamics? I want to point out this--take the quantum theory of radiation. This I know very well. I have written also the --. Well, you see, in this last part -- this is from the Physical Review. [Reviews of Modern Physics 4, 1932.] This was the big paper. Because one should be sure --. Here he is worried about the big divergences, because I remember in some place he mentioned the possibility suggested by Dirac, of the existence of the positive electron.
And he mentions, in connection with electrodynamics, that he was worried, but not surprised, so to say. -- Somewhere -- [Amaldi looks through the paper.] he mentions Dirac. Well, here, he quotes the paper from the transition of the electron from positive to negative states and somewhere in connection with electrodynamics, he discusses these negative states and suggested this but he does not express any thinking there. I think they were not against it.
Kuhn:How much were the rest of you worried about them? Those of you who were more inclined to experiment.
We were all very much worried. Majorana was worried about it, much more than anybody else. Majorana, in a certain sense, had a very clear, extraordinary, Mathematical, view. He was one of the few people who knew very well group theory. This is the reason he had rated so high Weyl. And at that time, it was a very early time, he was using group theory constantly. He had a very clear idea that all properties of the atom should be treated from this point of view. This was the reason why he said, “Well, Weyl is the only one who has understood the real point. All the others are just models or schemes but the real way of treating the thing is by group theory. We were much more involved, I should say, in these experimental problems. Well, you should think that Racah was here too. Racah actually came from the group in Florence. The group in Florence was very much created by Persico because Persico had left Rome when Fermi --. Well, they had one and the same competition; you know that we have still now this system of competition, of national competition. Then Fermi had a full professor chair in Rome and Persico had a chair in Florence. And Persico had a great influence on the group there which included Bruno: Rossi, Occhialini, Bernardini and Racah. Racah then spent a great part of his time between Rome and Florence. He used to spend one month here, then go back to Florence, and so on. And he was also starting to study group theory. So I would say that they were so different, these three people. Fermi was really interested in nature. Racah had the features of a mathematician, who would slide the mathematics toward the problems. And Majorana was difficult to classify. But he was very much interested and he was very much conscious of all the bad aspects of quantum mechanics, that he knew everything. All that was wrong. And he would say, “How stupid are these people? They make a theory and it is completely wrong.” This was a bit his inhibition, I would say. He was always conscious of the bad aspects of things in general.
Kuhn:We talked of beta decay a little while ago. You told me of this one experience when you were talking with Fermi. I will talk with Rasetti about this also, but I wondered if there is anything else from the beta decay theory that you think you remember?
Amaldi:Nothing much. Nothing in particular. Not in a very special --
Kuhn:You spoke just now of the competitions, the state competitions, and I’m unclear about those. I take it that those are held when there is one job.
Kuhn:How are they held? How often are they held?
Well, it depends. Now we have more than one per year. It depends on the number of chairs that you have. At that time there was one every few years. If a professor died or went away, there is a chair vacant, then they ask the Ministry of Public (Education) to open a competition. Well, this was not exactly so at the time of the Fascists. But this was before and is now. Then all professors of physics voted for men for composition of the committee. Every year. So then there is a committee made by five physicists and at a certain day the people that want to be considered have to send their curriculum and five copies of each of their papers to the Ministry and the Ministry distributes them to the five people in June or July. Then the committee starts to meet in October and they do a few meetings in which they are discussed. Then they choose three people to make a ‘trio’, No. 1, No. 2, and No. 3. These three have the right to be called to any chair on that subject in Italy. Once your man has been put in the ‘trio’ then he can be called to any university.
Kuhn:But no man can be called until he has placed in this.
Amaldi:Exactly. And the rest are completely free and only whoever is put in No. 1 has another right. Universities that call, if they prefer, can take the second or the third, but that is possible only if the number 1 has been called some other place. (So you cannot be jumped.)
Kuhn:One question about Fermi, I noticed looking here how very much he continues to write in Italian until he leaves. Most important papers get published in another language. But even though there cannot have been very much audience for much of his work, he does continue to publish an awful lot just in Italian. Was that partly a deliberate effort to raise the level of science in Italy? Was it that he felt more comfortable writing in Italian?
All these things. For instance, you just mentioned this paper on the slowing down of neutrons by Fermi and myself, was written in Italian. It was a big work just to write this paper -- it is a very long paper and so we had to work a lot. Then he was invited (???) Then in June he left Italy and he went to teach at Columbia. He was supposed to give a class at Columbia. And I got a scholarship and I went to Washington, D. C. to the Carnegie Institution. That was July of ‘36 to work with the van de Graaf there. And on my way I stopped in Columbia and everybody wanted to know about this paper. This paper was published only in Italian. Many people were interested to know the details. Well, many people were used to read also Italian at that time. Then Fermi would say, “Oh, I will never write again. It was such a terrible thing to write this paper in Italian. If you want, you write it in English. I don’t want to even see the proofs.” So I wrote in English with the help of one of his students, an American student who was my friend. We became friends. Then I said, “Well, I know very little English.” One of the people there was this one who insisted that this paper should be translated. The result was that I translated actually the paper in English. I did this myself with the help of this (Goldsmith). So I stopped for two weeks or three weeks in New York at Columbia. Of course (Goldsmith) was also very glad because he was working on neutrons and he was quite glad so he learned what was contained in the paper. Fermi did not want to write papers; he said, “Too boring.” He liked to do a work and then lecture. He liked to lecture but he did not like to spend time in writing.