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In footnotes or endnotes please cite AIP interviews like this:
Interview of Edmond Bauer by Thomas S. Kuhn and Theo Kahan on 1963 January 8,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Part of the Archives for the History of Quantum Physics oral history collection, which includes tapes and transcripts of oral history interviews conducted with ca. 100 atomic and quantum physicists. Subjects discuss 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 l920s. Also prominently mentioned are: Bouasse, Leon Brillouin, Louis de Broglie, Maurice de Broglie, Victor Henri, Paul Langevin, Walther Nernst, Jean Perrin, Regnault, Erwin Schrodinger, Pierre Weiss; Academie des Sciences, Universite de Paris, Societe Francaise de Physique, and Universite de Strasbourg.
Perhaps you would simply like to start. I would say to you that we often find it useful, if you are willing to do so, if you would simply as background tell us something about how you yourself got interested and came into the sciences. Often this helps establish the scientific situation in a country, and I think the personal way is really the only way to do it. Generalizations on this score we may all make, but the concrete details — how a particular individual comes to science and what problems and encouragement that gives him — can be very helpful.
I felt when I was a boy that I was interested in sciences. You don’t mind the faults I make in English?
No, no, no. But if you feel more at ease talking in French, we can also have French.
No, no; sometimes I will say some French words. When I was a boy — a very small boy of about seven years — I thought I would be an engineer. And I was first interested in sciences at school. We had little lessons, what they called “lecons de choses,” where they spoke of very simple natural phenomena. Those lessons, I think, principally, had the purpose of showing the peasants how to take care of the ground and how to recognize chalk from silicate and things like that. I remember the first experiments they did consisted of taking a little bit of chalk and putting some vinegar on it, and I saw the bubbles corning out, and it was quite marvelous for me. I remember I was not a very good boy at school, but that I liked very much. Then the next step was when I was about 13 years old. When I was 13 years, a friend of my father gave me L’Astronomie Populaire, a big book published by Flammarion. That was quite nice. It was a mixture of poetry and pleasantries and science. I liked it so much. I remember when I went to my piano lesson with a girl — we were friends; we took our lesson together — I always spoke to her of this Astronomie Populaire and she didn’t like it. But I was quite fascinated by the big numbers, that light could go 300,000 kilometers in a second, and the big distances of the stars, and that we knew something about stars. Of this Astronomie Populaire (Langin) published a new edition some years ago.
This schoo1ing was all in Paris?
In Paris, only in Paris. It was at the Lycee; the first classes in the Lycee were very good at that time. We had very good teachers of small boys; I came to this school when I was seven years old, and I went there until I came to the University.
Which Lycee was that?
Condorcet; that’s near the Gare Saint-Lazare.
You were at the Lycee Condorcet the entire time until you went to the University?
No. Then I came to another Lycee when I was fourteen years old, the Lycee Janson-de-Sailly, because we took another apartment. But my best remembrance of my school days was of the Lycee Condorcet where I knew every boy of my class, and I would play together with them.
Was there much encouragement of scientific interest at the Lycee or was —.
No, no. We had those lecons de choses till we were eleven, and after that we learned only mathematics, Latin, Greek, and French (and then German).
How much mathematics was then taught in the Lycee?
Oh, until the age of thirteen — from eleven to thirteen. They called it “calcul”; it was only the elementary things. Oh, we had about two hours a week. Then later on they began geometry when I was thirteen; it was very abstract — postulates and axioms and demonstrations. I was not bad, but I didn’t understand very well. There was algebra, and we began physics only at the age of seventeen — physics and chemistry.
’ How much physics and chemistry was there then?
There were about two hours of physics and one hour of chemistry. But, you see, when the boys there were seventeen, they could do two different things. They could go in what we call “mathematiques elementaires” or go into the class called “philosophie.” I had an interest in philosophy and also good friends who were in that class so I entered the class of philosophy where we had only two hours of physics and one hour of chemistry. In mathematiques elementaires it was much more scientific. I did my mathematiques elementaires alone by reading books. Then I entered the University.
When you made this decision, you already felt you were going to be a scientist?
My father wanted me to be a chemist — to go into industry. Then I profited by the circumstance that it was necessary to do only one year of military service, if you had some University grades. Then I told my father, “I must first work for my license, and when I have my license I’ll do only one year of military service, and then we’ll see.” And when I made my license, then I told my father, “I don’t like to go into industry; I’m more interested in theoretical (science).” My father made some resistance, but he let me. Then I worked for what we call aggregation — that’s for (becoming) a teacher in secondary school. You see, it was very important first, because in the French Universities after license we had no courses. We had to work all by ourselves. The only way to go a little further was to prepare what is called the aggregation. And secondly, when you were aggregate, you were sure always to get enough money to live. If the research would not be a success, then you could go into the Lycee, prepare as a teacher, and get a good salary.
When you say that your father resisted you’re changing from chemical engineering to the more abstract, was this largely on practical grounds?
It was on practical grounds, yes. I had (a chance) because my father was not rich, but worth some money; he lost very much of his money during the first war, but he was worth some money, so it was easier for me than for other young men.
What was the source of his own money, if I may ask? Where did the money come from?
Well, my father had a business in San Francisco. He had a business with his brothers. He went to America, I think, in 1856, or something like that, and he stayed there for some years, founded a business, and called his brothers there. His brothers came and stayed there, and he went back to France. And he still made the business; it was an (import) business from Europe to America. Then he was the European part and the brothers were the (selling) part; he was buying. He was more practical, but he didn’t make so much resistance as I thought (he would) at first. Then, you see the teaching of physics and chemistry was very bad in our Lycee. In some classes they had a good professor; I had a very bad one. He gave us some exercises and he was quite astonished that I made them, and he said always, “Your father knows something.” But I did it by myself. [General laughter] Then after passing my philosophy examination, what we call the baccalaureate, I went directly into the University.
Why is it that you picked the University at this point rather than considering one of the Grandes Ecoles?
Because my father was resisting my doing some theoretical [studies]. Then I went first to the University first, sous le pretexte du service militaire. Then I went to the University knowing very little mathematics. I had to learn it during the first years — to learn something. But I passed my examination in physics. Our professors were not good; it was very, very old-fashioned. You don’t know anymore the names of them. We had only one good –-
Well, I’d be interested in having you tell me a little bit of who they were and what the level of instruction was, and what books were used. This whole recreation of the educational system is of importance for us.
Our main professors were Bouty and Pellat. And Bouty had made a book with (Germain) (???). Bouty was a son-in-law of (Germain); he made a book with Bouty, and this book was not very bad, but it was physics about in the l860’s, before Maxwell, between Lord Kelvin and Maxwell. He was not a bad experimentator, but when he had some theoretical calculations to do on the board, he always made mistakes, and he couldn’t find his way out of the calculations. Pellat had some ideas, but he was also very old-fashioned. We had only one good teacher; that was Lippman; he was the man of the electro-capillarity and color photography. He was a better teacher, and he was much more interesting; he made splendid experiments. He was a very intelligent man, but he was also a little old-fashioned. You know, his thesis was, I think, 1876, or something like that, and I began my studies in ‘98. Then I passed my physics examination, I passed also my chemistry examination. I studied calculus, but didn’t take the examination; I studied mechanics, and then I took also my examination on mechanics. I had mineralogy also. We had to have four, what we called certificates; physics, chemistry, mineralogy, and mechanics. Then I went into military service when I had my license, and after that I began to prepare for the aggregation. It took me two years, and there also I said always I have a great gratitude to my teachers because they taught so badly that I learned to work by myself.
Were there standard books that you worked from?
About the books I must tell you two things. We had a very good book when I prepared for the aggregation. That was the report of the Physics Congress. We had a big Physics Congress in Paris in 1900, [and from that] we had three books; and it was really a revelation for us. We had an article of J. J. Thomson on, I think, the electron theory of metals, the first article of Poincare on relativity principle in 1900, and, I remember, an old-fashioned article of Lord Kelvin on the movement of a solid body in a solid. He thought (???). (These were some articles) which interested me very much; that’s very important in my own history. There was an article of Lummer on radiation where he described all the experiments on the Planck curve. But in this article Planck’s formula was an empirical formula and not a theoretical one. [There was also] an article of Pringsheim on radiation of gases, and an article of — who was it — I think it was Rydberg on spectra. I remember I made a lesson for the aggregation after my (???) (on spectral laws, Balmer series, I think I had.) It was a revelation for us; it was very important.
It was not just you yourself who read this; you think many students of your generation were —.
Not many, but a few of them, a few of them. Most of them were contented with the lecturers of the University who were very old-fashioned, but some of them, and particularly those who prepared for the aggregation, read those books. It was really a sort of Bible for us at that time. And another very important thing before I passed the aggregation was the first course of Langevin. Langevin was very young at that time. The Professor of the College de France was Mascart, who made some work on relativity — inference of the movement of the earth, from optical phenomena. And he was not a good teacher, but he was a good physicist, and he made a very good book on electricity and magnetism. It was a sort of vulgarization of Maxwell’s idea. I read this book, and it was also very important for me. When Mascart thought he was old enough, he asked Langevin to be his (super) at the College de France; I think this was in 1902. Langevin made his first course on ions and electrons, and they were beautiful lectures where he made all the experiments on electrons and ions. I remember he made measurements of the mobility of ions. In the lecture room itself he made the experiment of Townsend on the diffusion coefficient. And I remember that when an experiment didn’t give good results the first day, he made it the next week. It was very beautiful. And we saw the deflections of cathode rays. Oh, I must tell you another thing. All these things I vaguely remember. At the exhibition of l900, J’ai raconte ca au Palais de la Decouverte, I went into the scientific part of the English section. And I saw the apparatus of J.J. Thomson for measuring the (ratio) e/m of the electrons and the velocity of the electrons. I read it and saw the apparatus and I didn’t believe at that time that atoms were so real; I thought it’s marvelous, if it’s true. And then Langevin taught us that it was really true; on that we had quite a lot of experiments.
These lectures of Langevin were at the College de France?
Yes. They were at the College de France.
How large a group would have attended those lectures, do you think?
We were about twenty people — I think fifteen to twenty people.
And were all of you people with some professional interest in science as you yourself?
The most important group as I remember, were the students of the Ecole Normale Superieure, and some were outside [students] like myself. I must tell you also something I remember. When I was in the class of philosophy in the Lycee, I knew I was interested in physics. I read a book of an American writer — I don’t know if you know his name — Stallo. [I read Stallo] on atom theory; it was a very interesting critique of atom theory, and I read it with very much interest. It also had an influence on my life.
Was it widely read and discussed in French scientific circles? Was that book well-known in France?
It was translated in French; I read it in French. I found it in the bibliotheque of our school. Then I read it, and it took me one month or more to read it. I read it very thoroughly. Then I passed my aggregation; then I went —. I must tell you another thing I had forgotten; it’s very important in my life. The first year I went to the University in Paris, I was very —. I felt that those lectures were very old-fashioned and rather dull. And I went accidentally to the first lecture of Perrin. It was in a very little [lecture] room, amphitheatre, and I was quite enthusiastic of the Perrin lectures, before Langevin began to lecture. Perrin read about physical chemistry like it was at that time — van’t Hoff, Arrhenius, ion theory, and also kinetic theory of gases, and van der Waals, and all that. And I was quite enthusiastic and began to speak with Perrin. We began there a kind of friendship. It was something like a friendship; I was the only student of Perrin. At the first lecture they were all his friends, and after that we were two, de Bierne and myself. De Bierne was a scientist at that time, and he knew many things. Then he came two or three times a month; I was the only student who came every day, every aggregate lecture, and that was for two years.
Where did he lecture?
At the Sorbonne. He was charge de cours; he was not professor. And I must tell you that because when I passed the aggregation, I went to see Langevin and Perrin to know what to do. My father, who I knew still, had the idea of my becoming a practical chemist, wanted me to go to a foreign country to learn something. Then I asked Langevin, and Langevin told me, “There are two things you can do; you can go to J.J. Thomson, or you can go to Nernst.” Langevin knew Nernst because when Langevin passed his thesis, I think it was in 1902, he sent it to Nernst. Nernst was very interested by the thesis of Langevin, and Nernst invited him to Gottingen where he was professor, and Langevin was there about two, weeks discussing with Nernst. He was very much impressed by the intelligence of Nernst. Then I told my father, “You can send me to Nernst or to Thomson.” (Nernst was not [sic) a chemist, so I went to Nernst, you see.) I passed one year with Nernst. There was first the winter in Gottingen and the summer in Berlin. In Gottingen Nernst gave me some little work which failed. I had to make some measurements (of the conductivity coefficient of gases) (???) couldn’t work. At the end of the semester I could only tell him, “It can’t work.” The errors were too big. Then in the summer semester I went to Berlin; there I began making a little work on the dissociation coefficient of (nitro cite). It was not very interesting, but I learned how to work. Then I heard the lectures of Planck.
Which year was that?
It was in the beginning of 1905. Fortunately, it was very interesting. It was on the structure of the white light. You know those things of Wien; Wien, I think, first made the colors not in the light, but they have come from the apparatus And Poincare, Lorentz and Planck made some work on this. Planck was a very brilliant lecturer. There I remember there was something very funny. I heard the lectures in German, which I understood very well, and then I took my notes in French. That was because I was used to making French abbreviations; I don’t know how to make abbreviations in German. But I lost that; I lost my —
When you were in Berlin, or for that matter, when you were with Nernst in Gottingen, was there already then important talk about the quantum?
No, not at all.
Not at all? Not even from Nernst himself?
Not at all; Nernst didn’t know what it was.
But just a little bit later Nernst begins to be one of the —
It was later. I can only tell you Nernst thought about the third principle. He spoke to me about the third principle; he didn’t have it at that time, but he was looking for this. People didn’t believe [it]. I think they only began to believe quanta even in Germany after Einstein’s papers.
Which paper of Einstein’s? The one on specific heats?
No, no — the one on the photo-electric effect.
Do you think that made a big impression on people initially?
I think so. Yes, because I think the one on specific heats was two years later. I think it began to make an impression. I don’t remember when I first began to —. You see, I made after that my thesis in Paris on flames, on emission radiation by flames. And at that time everybody admitted the theory. The theory which everybody believed was the theory of Pringsheim that gases couldn’t send light by thermal emissivity. Then I began this work, and I demonstrated that it was a thermal emission. Then during all those years I was interested in radiation theory. I remember I made the record of Einstein’s papers on specific heats for the Journal de Radium. Then I bought the book of Planck on radiation theory; I think he made his lectures the year after I was in Berlin. But I think I was the man who spoke of it first to Langevin. I was for a long time the only man who knew something about it in France.
Langevin was initially himself not interested?
You see, we discussed it. Langevin was a very brilliant man, but I must say he was a little dumb, I think. What he learned when he was young — he was still young at that time — was Lorentz’ theory. And Lorentz’ theory was something so beautiful, a classical theory completed after that by relativity theory. It was his ideal. Then we thought in France, Langevin and I, for I thought about the same as he, that the first calculations of Planck were not rigorous at all. You see, Planck first calculated the radiation of a dipole with the theory from Maxwell-Hertz. And after that he introduced his quantum, and it was a contradiction. Now we know that it is the Correspondence Principle, but we didn’t know it at that time. And we were not —. I say “we” because I spoke also of that with Langevin —. I made the acquaintance of Ehrenfest during the summer vacations, and then we spoke of that. Ehrenfest was at that time working on his article for the Encyclopedia of Mathematical Science on statistical —, and Ehrenfest told me — how did he tell it in German, “nicht sauber.” He didn’t like it either. I must say that one thing which convinced me, only it was later that it convinced me of the necessity of quanta was the work of Ehrenfest. I don’t know if you remember it; [that was the work] of Ehrenfest which showed that the distribution of probability must be discontinuous if formulae like Planck’s formula [are] valid.
This was 1910 or 1911?
Yes, that’s it; that’s it. Then –-
You, however, did follow this line of work, even though you were not perhaps entirely convinced about it. Did Langevin even follow it in its early period?
He didn’t follow it as closely as myself because he was more interested in relativity theory. Then I remember — to show you what (I have seen); it’s stupid to tell you that, but I must tell you because it’s important in my history. I had remarked that the problem of the black body radiation and the problem of spectra of atoms had some connection together because we had a limitation on the high frequencies. There I tried — I was stupid — I tried to make the theory of black radiation by (admitting) resonators which obeyed the Balmer law. It was taking the problem “a l’envers” as we call it — on the back side, and I didn’t succeed. That was before Rutherford and Bohr. You see, at that time we were very isolated in France. We worked all individually, but for ourselves. Even Langevin had so much to do that it was very difficult to get access to him and discuss with him.
What aspects of the situation in France account for this isolation? You speak of being much more isolated and working much more individually in France; why was this?
I think because our laboratories were not organized. You see, we had no seminars. The professors gave the lectures, and the professors gave you sometimes, but not always, a theme for a doctor’s thesis. It worked or it didn’t work. But we were quite [left] to ourselves. I remember at that time I made a comparison between Germany and France. In Germany you were not free, you were like a wheel in a complicated mechanism, but it worked. In France you were quite free, but you were in the mud, and at each step you had to take your feet out of the mud. You see, it was much more difficult for us because we were quite isolated, and when you were not a genius —. I must say — people don’t know it, but I must say — I came back from Germany knowing what a seminar was, I told it to Langevin, and we organized, two together, the Seminar Langevin, which was the only one in France for years and years.
We didn’t know what it was; I learned it in [Germany]. In Gottingen it was very bad, but in Berlin it was a splendid seminar with Drude and Planck [a physics seminar] and Nernst came there also. It was very interesting.
And. it was as a result of that that Langevin’s seminar in Paris started?
Well, that is terribly interesting.
It was that indeed, and we were very few who did the research; the theses in physics in Paris, I think, were about ten a year. Now we have ten a week, or more. Then in my thesis I had two parts. I worked too much for my thesis; it was too much for a thesis; I ought to have written a book. The first part of my thesis was the exposition of quantum theory — how it was at that [time]. My thesis was written in 1911, and I passed it in the beginning of 1912. It was on quantum theory, and I must say I remember Lorentz wrote to me and told me it was the best book at that time. It was not a book; it was an article in the Annales de Chimie et de Physique. And the second part was on the radiation of flames where I showed it was a thermal radiation in emission. Sometimes had a case of chemical luminescence, but most of the times we had thermal radiation. After that we made some other work. I made some work with a friend of mine; we put a balloon in the sky to measure Avogadro’s number. We went to the Mont Blanc for the purpose of this work. We stood one week up there in the observatory; it was very nice. And this friend was killed in the war of ‘14.
You yourself spent a year in Germany.
Were there many other people studying science in France who went to Germany, or who went to England?
No; I was the only Frenchman in Gottingen, and in Berlin it was the same: I was the only one. You know Langevin began his thesis at J.J. Thomson’s laboratory, but I think he is the only one I know who made some work in a foreign country.
Was that due to a lack of money, or was there simply no desire to go outside of France?
I think it was both of them. I came to Germany because my father gave me the money to do it. He wanted me to learn something. I must tell you something. Then we were interrupted by the war — the war of ‘14. I was very lazy in doing my thesis during the war. I made work on radiation of mercury vapor, but I didn’t publish it because the war came.
Well, now before the war — You did your thesis with the first half as an essay on the state of quantum theory.
How was that received in France?
I think that was then rather well received. And I made also — I could have brought you the book — a series of lectures at the Physical Society. Perrin made a lecture on his work on atoms and molecules; Langevin made a very interesting lecture on what he called “The Physical Discontinuity.” But it was more on the theory of atoms; there was no continuity. But his ideas were — Leon Bloch made a lecture on kinetic theory of gases, and I made the lecture on quantum theory — radiation in quantum theory. Cotton made a lecture; I don’t remember on what. You see, it was well received; because I was a very young man and [yet] the Physical Society asked me to make the lecture on quantum theory. This course of lectures was in 1912.
Well, from then on from 1911, 1912 on — was there real interest in the quantum in physics?
No; it began only after the war. I remember I read Bohr’s paper before the war when it —. I think I didn’t [make any record] of it, but I read Bohr’s paper, and I had to make a lecture on it just after the war.
Just after the war?
Was there any notice taken of the Bohr atom in France before the war?
Not before the war, only after the war. I remember there was some resistance.
Still after the war there was?
Still after the war, because it wasn’t classical enough, you see.
Do you remember particular episodes about resistance?
No. I remember it was much later — I was at that time professor in Strasbourg — and we had a little congress among ourselves in Nancy. There was Cotton, and there were other people of Nancy. Weiss was there —. I was in the group of Weiss in Strasbourg. Then I spoke about quanta; I don’t remember what I told. And they were not interested. That was about 1923 or ‘24.
How much of that resistance there, do you suppose, grew out of the conflict between the theory and the Weiss magneton?
I must tell you the story about the Weiss magneton because I was just stupid at that time. I don’t know. I remember Weiss talked —. You don’t remember? That was a little later when I came away from Strasbourg. Forrer made some sort of theory of contacts [between electronic orbits in neighboring atoms determining magnetic moments. Comptes Rendus, 1932]. It was something very, very nebulous. And then Weiss told me, “All you think about is quanta. There is classical physics, quantum physics, and the physics of Forrer. And quantum theory is not very interesting, but the physics of Forrer — that’s a very interesting thing.” I never believed in what Forrer said, and nothing is left of it.
That’s quite remarkable.
I must tell you during the war I was made a prisoner by the Germans. Just at the beginning of the war I was wounded in Charleroi, and I couldn’t go back with the French troops. My comrades put me in a house in a bed, and then the Germans came and took me. I was three years a prisoner, and before the end of the war I was exchanged through Switzerland; I passed one year in Switzerland from June 1917 to August 1918. There I worked with Weiss, a professor in Zurich. Then he gave me [the task] to measure the magnetic coefficient of oxygen and acidic oxides; I don’t know what you call it in English. Picard had made some measurement of it before and found Weiss magnetons and Weiss told me, “His measurements were not quite precise; I think you will find better Weiss magnetons.” Then I made the measurements. I found some errors in Picard’s [measurements] and I invented two new methods. One was quite concordant, and I said that I found that there were no Weiss magnetons, and that instead, oxygen had two Bohr magnetons. I wrote it; I gave the paper to Weiss, and that was very stupid. I wrote, I remember, very well, but I said the theory of the Weiss magneton must be considered again, “doit etre revisee et reconsideree.” And then Weiss put it out and said, “(I fully realize it), but the theory of the Weiss magnetons is founded at so many other experiments that we must not abandon it.” And I thought my experiments were so sure that people would understand what I said, but they didn’t understand. It was only [realized] some years later. I think an Englishman — I don’t remember his name who (brought) my experiments in in saying that the magneton theory of Weiss was false. I knew it very well, but I was too feeble with my own master, Weiss. That was also the reason when I found Bohr magnetons in oxygen — I didn’t know that in nitric oxide there were no Weiss magnetons and no Bohr magnetons. We didn’t know at that time that the curve was not a Weiss curve. I’ll just tell you the things you like if I think of anything.
That’s fine. You have a remarkable memory.
I have a very bad memory on numbers and of precise [things], but of what I lived I can remember it very well.
This is immensely useful to us, and this sort of story is very much to the point.
You see, de Broglie will tell you how he found his mecanique ondulatoire. I remember the year before I went to Strasbourg as a professor, Langevin began again his seminar. There I remember somebody brought up the work of Einstein some work where he [talked of] the quantum condition of Sommerfeld as if there were some periodicity in space. I don’t know if you remember this work. That was the beginning of de Broglie’s work on [wave] mechanics.
You said that it was really only at the end of the war that people in France began to find out about the Bohr atom, and that there was still some resistance to it then. Do you remember in what form did they then hear about it, because in Germany a lot of work had been done during the war. Was it already the Bohr-Sommerfeld —?
In France during the war no scientific work at all was done. Most of the young physicists were soldiers; a good part of them were killed. I was wounded in Germany; two of my best friends were killed. Nobody worked. Even Perrin and Langevin did some work on war physics. Langevin made his work on (acoustics), and Perrin made some work on many things. The most interesting work was on the location of planes by sound. The only man who made some work was Weiss because the French government told him it would be better if he went back to Zurich as a Frenchman than it would be to stay in France and make his scientific work and give his lectures. Then after that I have not much to tell you. But I remember when I was professor of theoretical physics in Strasbourg from the end of 1919 to 1927, I think, ‘27 or ‘28, I made lectures first on the Lorentz theory, then quantum theory, the theory of Bohr’s atom, and on relativity theory. But most of my lectures were on the theory of the atom and also on statistical mechanics. At those lectures I had one, two or three students — not more. [That was] because people said it was a fantasy, even at that time. I had no support at all, only for relativity theory because it was a la mode. Then I had all the engineers of the town who came all the year for hearing my lectures on relativity theory, but on quantum theory they didn’t attend. I had about ten to fifteen people for relativity theory and one or two for quantum theory. That’s remarkable. Real interest for new modern physics began here only after de Broglie’s work was well-known. Now, I must tell you something else perhaps de Broglie will not tell you about. It’s not about myself, but about de Broglie. Victor Henri was a very good friend of mine; he was at that time also professor in Zurich at the University. Weiss was at the Polytechnique. Victor Henri told me this story. He went to Paris from Zurich and Langevin told him, “Oh, we [had] the very remarkable thesis of de Broglie and I will give it to you.” And Victor Henri came back to Zurich and began to read the thesis of Louis de Broglie. He did not understand very well what it was about; then he gave it to Schrodinger, who was professor of theoretical physics in Zurich. Schrodinger after two weeks gave it back to him, and told him, “that’s rubbish!”
Would this have been the printed version of the thesis before it came out in the Annals de Physique probably?
Yes, [this was the printed thesis] before it came out in Annals de Physique.
It was in the shape of the thesis, not a reprint of the Annals?
Ca, je ne me rappelle plus. Je ne peux pas dire. I’ll tell you what Victor Henri told me. It’s not my —-. Schrodinger told him, “that’s rubbish!” And Victor Henri came back to Paris, saw Langevin, and told him what Schrodinger [had said]. And Langevin told him, “I think Schrodinger is wrong; he must look at it again.” Then Victor Henri came back to Zurich and told Schrodinger, “You ought to read again the thesis of de Broglie; Langevin thinks this is a very good work.” Then Schrodinger read it again and began his work.
It’s very interesting. It’s not my own memory, but I remember very well when Victor Henri told me that. Schrodinger didn’t understand it at first and it was only because Langevin thought it was very good that he [read it again].
When do you suppose you actually heard the story?
Oh, two or three years after the papers of Schrodinger. It was not a very long time.
That’s a fascinating story. Did you travel to Paris while you were at Strasbourg?
Yes, because my family and the family of my wife lived here. We came not very the first year my family (stood) because I had no apartment; then I went every week to Paris, and after that, I came to Paris three or four times a year.
Did you have then any impression as to the extent to which people were paying more attention to quantum mechanics — to quantum physics in Paris?
That I can’t tell you; I don’t remember. I must tell you — another man who had a big importance in quantum theory in France was Brillouin. Brillouin did it quite [independently]. Brillouin is, I think, about ten years younger than I am. Brillouin came to Sommerfeld, and there he learned quantum theory and made his first work on the theory of waves in solids. Then I must tell you of another story. I saw him, and he was enthusiastic about the theory of matrices, before –-
Before the Schrodinger equation.
No; it was not before, but it was about the same time. And I didn’t understand at all. We discussed it together, and I said, “It’s too abstract; I don’t understand.” And I understood rather better after de Broglie’s work, and when Schrodinger showed that de Broglie’s work and Schrodinger’s equation and matrix theory were the same thing. But again the interest was —. People began to be very interested about after 1928 and 1930, something like that. I made some lectures on group theory. I don’t know if you know the book.
I’ve never really read it, but I know of it.
Yes; it’s just been completed in English now in America. And they asked me at the Institut Henri Poincare to give those lectures in ‘32; then people were very interested here. I can tell you another story. When was that? It was about the same time, about ‘32. We have here every year a week of lectures [that] we call semaine de synthese. There are mostly philosophers and historians, but they are interested also in scientific questions. Langevin had to make the lectures on the philosophical side of quantum theory, and one morning Langevin [called me on the] telephone and said, “Come and see me. I have a lecture to give tomorrow afternoon on the philosophy of quantum theory, and I’m too tired and can’t do it. You see here I have some notes and a paper written by Planck.” Langevin was always like Planck and de Broglie [not like Bohr] — his philosophy was always classical. Then I made this lecture [as best] I could, but when I had to write it, I saw that all what I had told was not what I believed. Then I wrote something more like Bohr’s [philosophy]. But at that time Langevin was quite (???) (in) those things.
How late was that?
That was about ‘32, I think. And always until he died, Langevin (did) believe in de Broglie’s theory of double solution — he didn’t believe in —.
What do you think it was that changed the nature and extent of French influence? You say that by the 30’s there was real interest in France in [quantum theory]. Now, that is already so late.
Yes, it’s very late.
One wonders why it happened even then, if it was not going to happen sooner. Was there a decisive event?
I think the decisive event was the theory of de Broglie; I think so. No, the decisive event was the Bohr theory of the atom.
But that was after all 1913.
But people knew it only — We had the war, and during the war it was absolutely a black-out. Then interest began again but it took some years.
The Bohr atom is surely decisive for the development of quantum mechanics, but it seems to me it cannot have been decisive for the development of French interest in quantum mechanics.
Yes; because it was more complete, and, I think, more tangible than even Planck’s theory.
But I remember my thesis was experimental, but I was always interested in theory. When I was young, people told me, “Oh, you are a fool, you are interested in theory.” Theorists were quite an offense; on se moquait des theoristes, they laughed at us. This is my personal opinion, but I think the scientific people in France lived under the influence of the theory of Auguste Comte’s positivism where all theory which was not phenomenological was thought to be not sure and not interesting. I think people thought theories were something like modes; people spoke of a fashion, a “theorie a la mode.” And they thought they are interesting for some years and after that nothing exists. I think this positivist spirit of the French nation had a very bad influence because it was not a constructive positivism; it was a negative one. For all physicists who were not philosophers, I think in the background, it was the reason for this.
Did it effect even the extent to which one learned thoroughly classical theory? Did this positivistic spirit keep one from even taking classical theoretical physics seriously?
No; it was contradictory because [there was] perhaps some nationalism. The optical theories of Fresnel were (studied). At the beginning the University liked something quite real and certain —. And our professors taught us of the movements of the aether. You must ask de Broglie; he can tell you other things that I can’t. But it was very long before interest came. Langevin did very much for this because his lectures were always splendid; he was the best teacher I ever saw. He made much about this, but he had a part of dogmatic spirit. He was always “resistant” of quantum theory. But I remember discussions about relativity theory when Einstein came to Paris. It was about 1920 or ‘21, just after the war, and there was still great opposition from the old men — the old professors. Painleve, for instance, who was a splendid mathematician, I remember, had quite stupid objections to Einstein. I think I have spoken enough now.
You speak of this opposition, of people saying to you, “You’re crazy to think of doing theoretical physics. Leon Brillouin said very much the same thing; that people (had again) said that to him. And —
His father was a good theoretician.
Yes, yes. That’s the question, you see, that I wanted to ask you because in a sense it is strange to me to think — I wonder how old that attitude against theoretical physics was. After all, Leon Brillouin’s father was a good theoretical physicist.
Yes, he was a good [theoretical physicist].
And there is Poincare from mathematics who was a great theoretical physicist. And the 19th century French tradition is a tradition of great theoretical physics.
Yes. I think we had a sort of eclipse beginning in the 60’s and going until 1900 and later.
But, you see, it isn’t that French physics goes entirely into eclipse because you do have great experimental physicists. Somehow or other the attitude — the ideology — toward [this] seems to become one in which physics means experimental physics. I wonder whether you have more that you can tell us about how that happened, what it was that made physics which had been a predominantly theoretical subject in France now look like a predominantly [experimental one] and why the idea of physics in France in 1900 is so much like the older British idea of physics.
A man, who had a big influence, because we learned his work when we were at school, was Regnault. Regnault made splendid work, but very precise on gases. And Regnault and his successors, Amagat and those people had a big influence. Perhaps [it was because] Regnault was not a theoretical physicist. In school I was in mathematiques speciales — Le cours de mathematiques speciales, c’etait de Regnault. Vous parlez toujours des eleves de mathematiques speciales de Regnault. On vous embete avec les robinets de Regnault. I don’t know the real reason, but it’s a fact.
The real reason we may hope to learn in the long run, but I’m much interested in what you say about this.
Lippmann was also a good theorist, but very classical, and he didn’t understand Maxwel1 theory very well, I think. At that time it was difficult; I read an old paper of Lorentz and he said, “I read Maxwe1l; it’s very difficult.” He was about twenty-two years old.
After the war when Langevin resumed his lectures at the College de France, let’s say from 1919 up to ‘25 about what was he lecturing?
Then I don’t know because I was not in Paris at that time. But he made splendid [lectures]. I saw the notes taken by (Picard); he made a splendid lecture on acoustics and hydrodynamics — [about which] his work on (azdic). It was really splendid, and it’s a pity it didn’t appear because when Langevin did some work, it was —
Have those notes been collected?
(Picard) collected them, but never published them.
But I mean, are they deposited somewhere now?
(Picard) has the manuscript; I think he is the only man who has [the manuscript]. And [Langevin] lectured on relativity, I remember, and he made the lecture on the quantum statistics with the Fermi-Dirac and the Bose-Einstein. It was after those lectures that Brillouin made his book on statistics.
You said before that your teachers had taught you of the reality of the aether.
What did they teach you about atoms?
Atoms; that was a new process. And I remember very well when I was at school I had a book on chemistry where they had to speak about atoms. I couldn’t understand what [they said], because Berthelot had a very bad influence (the chemist) Berthelot because he was also a positivist, and he didn’t believe about atoms. You couldn’t understand what the difference was between an atomic weight and a molecular weight — I couldn’t understand. And there is another thing I remember. I was an assistant to Perrin, but I had, not much to do with him. No, it was before I was assistant to Perrin — the first year when I came back from Germany, I was a teacher in a Lycee in Paris, the Lycee Janson-de-Sailly where I had been a scholar before. Then I made lectures on atom theory, and I remember I presented it as a hypothesis, very vraisemblable, but a hypothesis. I told that to Langevin, and Langevin said to me, “You’re wrong; it’s a fact.” I remember it very well.
But I take it he was one of the very few people in France who would go that far.
Yes, yes, yes. It was before Perrin’s experiments.
What could you tell us about the effect of de Broglie’s thesis? — of the opinions of the members of his committee. What was Langevin’s own opinion?
He was quite enthusiastic; that’s sure because he told it to Victor Henri. He was very enthusiastic because it was a wave theory; then he hoped it would be again classical. I think so. And de Broglie thought also that it could be classical again. About the other members I don’t know. But I think it was a reason — there was also that the thesis was a very beautiful thing, but it was also one reason because it was a work of art. For me it was also something not so abstract. [Although] I was very disappointed when I saw that the waves were in a (space of three dimensions).