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Interview of Hans Thirring by Thomas S. Kuhn on 1963 April 4, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4912
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This interview was conducted as part of the Archives for the History of Quantum Physics project, 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 1920s, Also prominently mentioned are: Franz Serafin Exner, Fritz Hasenohrl, Albert Lecher, Erwin Schrodinger, VA Wirtinger; and Universitat Wien.
Would you talk first about the scientific work in Vienna at the time when you and he were students together. About scientific education, about who were the leading figures. I’d like very much to know more about Hasenohrl, to know more about Exner and then include your recollections of Schrödinger in this. What was different about Vienna as a place to be a student of science, of physics?
All right. I shall try to assemble my recollections of that time when I studied here in Vienna together with Erwin Schrodinger. He is a year older in that sense and therefore remembering that I entered the University in October, 1907, it follows that he came to the University in 1906. So he was a year ahead of me. I remember sitting one day in the mathematical seminar before I ever met him — sitting in the seminar before the lecture began and there entered a fair young man and a student who sat beside me just told me, “Oh, this is Schrodinger!” He had an awful respect for him; I liked this man also and I soon became acquainted with him and then it turned out that we joined in preparing for examinations, for instance, for the lectures of Professor Wirtinger, who was one of the most famous mathematicians at that time; and I remember also that Wirtinger’s lectures played some role in the basic mathematic education of Schrödinger. Both Schrodinger and myself were students of Professor Fritz Hasenohrl, who was a rather young man and he was the successor of the very famous old Ludwig Boltzmann. Boltzmann’s successor, therefore, Hasenohrl, was our teacher. Hasenohrl’s art of giving lectures was quite excellent. He was the best lecturer I ever heard, much better, for instance, than Wirtinger’s lectures. Hasenohrl was the cause for me that I turned to theoretical physics. I first started having more interest in experimental physics but when I heard Hasenohrl’s lectures, I was so fascinated by the way he did it that I became a theoretical physicist too.
Unfortunately, Schrodinger did not become Hasenohrl’s assistant because when there was a vacant post for an assistant — there was only one assistant at this small institute for theoretical physics — when there was a vacancy, it was in October, 1910; Schrodinger couldn’t accept the post, although it was first offered to him, because he had to begin his military service. I had the luck that sometime before I had broken my leg, my left leg, and therefore I was not fit for military service. By this chance, I got the post as assistant. Well, it was a misfortune for Vienna because Schrodinger first got a job at an experimental institute with Professor Exner, who was a very good teacher also. Schrodinger stayed there for a few years and then came the war and he had to do his military service during all the war. Afterwards he soon obtained an invitation from a German University in Jena. Since that time he never came back to Austria, though of course as a guest and as a visitor, but not for a job until in the 30’s after he was dismissed and he left Germany.
Let no take you back into the University again. You speak of Hasenohrl as a particularly fine lecturer. What distinguished him as a lecturer?
I think he had a very thoroughly prepared lecture. Of course, he spoke free, without a manuscript but he prepared his lectures very, very thoroughly and he had written them all in a took. He made it very easily understandable and did it very thoroughly and besides he was a genius. He was the man who I think one or two years before Einstein also taught the idea of the connection between energy and mass. That’s his famous work he did, although it as not as general as Einstein’s work. He simply showed that the radiation in an empty ‘Hohlraum’ — I think the expression ‘Hohlraum’ is also used n the English literature. Well, imagine an empty vessel which is evacuated, an evacuated vessel containing just radiations. If, for instance, the walls of the vessels are hot and the interior of this vessel is filled with radiation, and he showed simply the content of radiation in itself without the walls of the vessels would have some kind of energy. That was Hasenohrl’s idea. This idea leading to the equation E=mc2 was derived from much more general ideas from the principle of relativity by Einstein. So this priority does not in the least decrease Einstein’s importance and besides, unfortunately, Einstein who worked at that time in 1905 at the patent office in Berne had not the slightest ideas of Hasenohrl’s work. Hasenohrl’s paper was published in the Akademie Berichte of the Vienna Academy and this doesn’t seem to have been available to Einstein. So Einstein had no idea of Hasenohrl’s work. However it was a very, very important step which Hasenohrl took and it made him famous too. I remember that he was always invited to the very, very famous Solvay conferences. He was one of the members of the Solvay Conference and something much more important might have come out from Hasenohrl too if he had not been killed in World War I. Unfortunately, he was killed in 1915. Well, anything else?
Do you think Hasenohrl had very much influence on Schrodinger?
Yes, certainly. All his, let us say, exactness in talking might have been due to the education by Hasenohrl — not directly what he did afterwards in the wave mechanics; when he conceived the wave mechanics he was influenced in the first line by the Frenchman de Broglie and also by Einstein. These were pioneers in this field.
I meant more in his stamp, in his makeup as a scientist, was there a strong influence here of Hasenohrl?
Yes, certainly. Both Hasenohrl and Exner influenced him. I think Wirtinger influenced him less because Wirtinger, unfortunately, although he has quite an ingenious mathematician, was one of the worst teachers you can imagine. It was very, very difficult to follow Wirtinger’s lectures. So he was not influenced, as you say, in his makeup either as a teacher by Wirtinger. Of course, the contents of Wirtinger’s lectures were very helpful afterwards in a lot of mathematics which he needed in conceiving the wave mechanics.
... It would help me to know his particular style. To what extent has he the mathematician as a physicist? Think of hit as compared with Sommerfeld, as compared with Born. Born, the man who was almost as much a mathematician as a physicist; Sommerfeld as a person who was a strange mixture of the two. Both very different from Bohr, for example, who was very little a mathematician but with deep physical insight.
Well, I might compare him with Sommerfeld, I think. He was similarly politic toward his students as Sommerfeld was. Of course, his career was so much shorter than Sonmerfeld’s. During his very short career from 1906 until 1914 — then the war broke out — it was only seven years — quite a lot of later professors emerged from his school.
Now Exner was quite different, was he?
Yes. Exner was no mathematician at all. He was a purely experimental physicist but he had very, very good ideas as to what they call natural philosophy. He was —. You see, at that time, when the very existence of atoms was still disputed — you remember there were people like Mach, for instance, and Ostwald, particularly Ostwald, who said that they were pure speculation. At that time Exner was one of the defenders of the atomic theory.
When you and Schrodinger were students, were there still in Vienna residues of those debates or was it, by 1906...?
Well, we were brought up in an atmosphere in which neither of us had any doubts about the existence of atoms and I think neither of us felt anything in the direction of Ostwald.
What about the question of the ether?
Well, I learned very soon to emancipate myself from the idea of ether. I became acquainted with Einstein’s ideas by Hasenohrl. This sufficed to make me a defender of the purely mathematical conception of the electromagnetic field without a substance as an ether. That was the same, of course, with Schrodinger. But this idea was not agreed upon by all of the professors. I remember that the head of the other department of experimental physics was Professor Alfred Lecher, also quite a famous man. He was at the end inventor of the so-called Lecher wires — the parallel wires with which one produced the first short-wave. So he was an expert in his field of wireless telegraphy. I remember of having a dispute with Lecher at a time when I was still a snail assistant and he was a professor. Lecher had some arguments in favor of the existence of the ether. I made my counter-arguments and I nearly convinced him that the idea of ether is not necessary.
When you say you learned of Einstein’s ideas from Hasenohrl, did Hasenohrl teach relativity; did he lecture on it?
Yes, you see, at the end of the semester in which he dealt with electricity and electromagnetism — it was a two semester, a whole year course filled with electricity and electronics. He talked about Maxwell theory — it was a very full exposition of Maxwell theory and at the end of the summer semester he explained to us the Theory of Relativity.
He had no doubts about it himself?
No, no, no.
He must have been one of the early people to teach it.
Yes, that must have been about 1912 or so.
What about the quantum?
Well, that was discussed too. I can remember that very soon after the first papers by Bohr in 1912, this was discussed in our theoretical seminar.
Had you heard earlier of it in terms of Planck’s or Einstein’s work on the photo effect?
Yes, of course; he dealt with it I suppose at the end of his lectures on statistical mechanics. Yes, he gave a broad exposition of statistical mechanics, of the work of Boltzmann and Gibbs and as a part of this lecture he spoke also of Planck’s idea. This was earlier, I think in 1911 or so. He had a very large lecture. The whole course for theoretical physics consisted of eight semesters, four years; during four years he had this full course of theoretical physics and therefore I attended his courses already when I was his assistant. I didn’t go there in the first semester. I entered his courses only in the third semester. Well, I was finished when I had attended all his lectures. Therefore, as a doctor and as an assistant I still attended his lectures.
When you speak of the student who pointed and said, “That’s Schrodinger!” did he already have as a student an outstanding reputation?
Well, this particular student was one of his colleagues in the high school. He knew him from the gymnasium and he seems to have had some reputation there also. Oh, I remember this is mentioned also in this book by Mr. Hermann. It’s mentioned there.
I know that he has written it now, but I haven’t had a chance to read that.
Yes, it is mentioned there, yes.
Among the group of yourself and Flamm and Schrodinger, was Schrodinger himself something of a leader in this group? Did you look to him as someone who had still more ability or were you...
I personally looked to him as my superior. Anyhow I was quite convinced. Oh, I remember that soon after we graduated, I said to some of my colleagues, “Now look here, this is Schrödinger and we can expect something very important from him.” That was long before he started his work in the wave mechanics. I saw in him the future Nobel Prize winner.
Did others also have this impression?
I don’t know. I don’t know. Not all of the professors had this impression. I remember one of the professors of chemistry didn’t think much of Schrodinger. But he was absolutely wrong, of course. Just excuse me, Professor Kuhn. I have to give a lecture tonight then I’m off tomorrow to my place at Kitzbuhel. I think I have told everything which might interest you. Perhaps I could give you — if I have it still — a spare copy still of my paper which I wrote for Schrodinger’s 60th birthday.