Hedwig Kohn

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Interviewed by
Thomas S. Kuhn
Duke University, Raleigh, North Carolina
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Interview of Hedwig Kohn by Thomas S. Kuhn on 1962 June 7,Niels Bohr Library & Archives, American Institute of Physics,College Park, MD USA,www.aip.org/history-programs/niels-bohr-library/oral-histories/4512

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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: Rudolf Walther Ladenburg, Otto Lummer, Fritz Reiche, Clemens Schaefer, Erwin Schrodinger, and Thomas.



The interview with Professor Hedwig Kohn (department of physics, Duke University, Raleigh, North Carolina) was not very productive because there was very little time and because she did not like the idea of the tape recorder. Since her own connections with the development of quantum mechanics are slight, any consistent line of questioning was very difficult. Besides, she had very little conception of what we might want. She was prepared to show us photographs in her possession arid to disclaim any real knowledge of the history. By the time we got to questions, there was not much left.

However, a few interesting points did emerge. In the first place, Miss Kohn speaks very highly of Eucken as a person of real perception in physics. She also indicates that he, she, Ladenburg, and Reiche formed a group at Breslau which always discussed their problems together. It was through this group that most of her own contact with the development of quantum physics came. In the group she again speaks of Ladenburg as the leader in quantum mechanical intuition. She says that again and again they tried, as did so many other people in the early ‘20’s, to employ the correspondence principle as a key. It is this, she feels, which underlies Ladenburg’s dispersion theory. Asked about other members of the group, she indicates that Lummer did not participate in it but she immediately insisted that Lummer had an immense physical intuition. She is the one person I have so far spoken to who seems really devoted to Lummer and his memory. She was very eager to see that he rather than Rubens got credit for the essential experiments in the development of Planck’s formula. She also speaks of a colloquium at which a paper was presented on some very accurate spectroscopic measurements made in Japan; these included some puzzling multiplicities of lines; and Lummer immediately suggested that these must be due to isotopes. Apparently they were nuclear hyperfine structure and she thinks that is what Lummer’s remark pointed towards. Also, she supposes that this was before the relevant papers by Pauli and Goudsmit. Later, in speaking of the reactions to Schrodinger’s papers, she indicated that Schaefer had not been at all happy about either the Bohr atom or about the Heisenberg formulation of quantum theory. On the other hand, he was immediately quite enthusiastic about the Schrodinger formulation. Apparently, the good familiar mathematics plus his own acquaintance with wave formulations brought him around.

On this score, Miss Kohn made one interesting psychological remark. Schaefer, she said, found that Schrodinger’s wave equation made quantum mechanics concrete for him. She herself, on the other hand, insists that the Heisenberg formulation has always been the more concrete for her. She says that matrix elements are not, to her, items in a mathematical formalism. On the contrary, she sees them as electric moments or something of this sort.

Miss Kohn was also the first person who responded particularly well to my question about the reasons for the concentration of people from Breslau. In this connection, it must be remembered that she is from Breslau and closely associated with the University herself, so that a good deal of pride is involved. In particular, she did not respond well to my suggestion that it had not been a first-rate physics department. She insisted that it had been, and that much of the credit for this must go to Lummer and secondarily to Schaefer. Lummer, she said, insisted that he must have 5 1/2 assistants so that they would all have time to do research. This, she suggests, is why Ladenburg spent so much time at Breslau; he would not have stayed under the circumstances if he had not had so much time for his own work. In addition, she says, that both Lummer and Schaefer insisted that they would not have the department become specialized to one field. There was extraordinary variety she thinks. But, in addition, she did point to some reasons that may have to do with the productivity of Breslau itself. Very probably it has to do with the local population for almost all of the students at Breslau were in fact from the local area. It was, she indicates, an area with a particularly good and famous medical school. There were many, many distinguished doctors in the area and much productive work was done. In addition, she suggests that there were a great many Jews and that they had a particularly literate background. Also, she says that the Breslau opera was quite special. Apparently, aspiring young singers were always delighted with a call to Breslau, because it was a point from which the best of them would regularly be called to the great jobs in Munich, Berlin, and elsewhere. In this respect, she suggests that the situation for opera resembles the situation for young physicists.

Asked about any special problems that may have existed for a woman in physics, Miss Kohn says that she was only the second one in the Breslau department. When she entered school, she was not allowed to matriculate officially, but was instead only a “guest student” and that did not entitle her to get a degree. She did not worry very much because she assumed the situation would change and it did. Again, when Lummer urged her to obtain her “Habilitationschrift” in 1919, she spoke to the dean and discovered that the rules specified “young men”. Again, these were changed in the early ‘30’s though she was not herself habilitiert until appreciably later.

As indicated above, Miss Kohn was part of a group that heard Schrodinger’s early lectures on the wave equation in Berlin. It was this which lead to her remarks about Schaefer’s reactions. The lectures themselves did not, she says, create a great sensation because the papers had already appeared. Pressed further on general resistance to the idea of the wave equation, Kohn insists that there was none, and then immediately adds “at least not from our group, we were prepared for anything.” As I tried to explore the general area of what had been exciting, Miss Kohn immediately volunteered that when she got the first edition of Sommerfeld’s Atombau she could scarcely put it down, but found it as stimulating as a detective story.

One other colloquium which Miss Kohn mentioned — and asked me not to make a record about — was given by Einstein on the Bohr, Kramers, Slater paper. She says that she, Reiche, and Ladenburg had studied this paper carefully and felt they understood it. She then had a chance to hear Einstein give a colloquium on the subject and went eagerly, only to conclude — it was this she did not want on the record — that Einstein really had not understood the paper himself. He had another way of thinking about such problems.

On the subject of the importance of Breslau, she adds the following item which actually fits very closely with something that one of our other subjects has told us. She says that there was a. particularly good teacher at the Konig-Wilhelm Gymnasium in Breslau and that she thinks many of the physicists who came from Breslau may have been deeply influenced and attracted to the science by him. As it worked out, she was once instructed by him herself. She went to school just at a time when arrangements were first made to allow women to take the matriculation examinations for the University. The man brought to her own school to teach science was very bad, unfortunately, because it was very hard to get anyone to go to a girls’ school for this purpose. As a result, the ten girls who took the matriculation examinations with her, all feeling deficient with respect to the science examination, marched themselves over to the well-known teacher from the Konig-Wilhelm Gymnasium and arranged to have special instruction from him. She too found him a considerable source of inspiration.

Again on the subject of Breslau, Miss Kohn brought along a book by one of the medical men who had spent time there and which says a bit about the place. It’s not terribly informative but is some sort of evidence to special character. In particular there is a significant quote on pages 77-78. The book is: Oswald Bumke, Erinnerungen und Betrachtungen: Der Weg Eines Deutschen Psychickers — in any case psychiatrist is what is meant — published by Richard Pflaum, Verlag, Munich. I could not find a date for the book but it’s sometime in the early fifties.

Finally, Miss Kohn said again that the Thomas, who was a pupil of Reiche’s was a man of particular brilliance and promise who unfortunately died young. I told her the story of Caratheodory’s reading of Heisenberg’s first paper. She found this not at all implausible and said that Thomas had reacted the same way although he was just a young student at the time. After reading the paper, she said, he remarked to her, “I should like to know that man.”