In response to:

The Charms of a Physicist from the April 11, 1991 issue

To the Editors:

Recently, a review by Jeremy Bernstein [NYR, April 11, 1991] on Victor Weisskopf’s autobiography The Joy of Insight: Passions of a Physicist has been brought to my attention in which Bernstein criticises among other points Weisskopf’s treatment of Werner Heisenberg, my father. While some of Bernstein’s views have already been corrected by Thomas Powers [NYR, June 27, 1991], new accusations are raised in Bernstein’s reply.

First of all, I would like to point out that Weisskopf knew Heisenberg very well. He had worked with him in Leipzig and met him regularly thereafter. Bernstein probably did not know Heisenberg personally but relied either on biased opinions (S. Goudsmit, see last paragraph below) or on opinions of those who hardly ever had met Heisenberg (P.L. Rose, M. Walker). Furthermore, Bernstein seems not to have read many of the relevant documents himself. He certainly neither consulted the Heisenberg Archiv in Munich nor the extensive collection of private documents of the Heisenberg family.1

If Bernstein had been better informed he would have known that the German physicists had a fairly good estimate of the critical mass of a nuclear bomb (see e.g. D. Irving: The German Atomic Bomb: The History of Nuclear Research in Nazi Germany, Simon & Schuster, New York 1968). From the papers of the “Uranverein” Bernstein also would know that they never planned to use a nuclear reactor as an explosive. Bernstein himself qualifies his information about this idea (which he calls facts) as “murky” but he does not hesitate to spread it.

An unbiased evaluation of the available documents (see e.g. McGeorge Bundy: Danger and Survival: Choices about the Bomb in the First Fifty Years, Random House, New York 1988) clearly shows that the Germans did not try to build an atomic bomb. Although some of the German experts (e.g. Bothe, Flügge, Heisenberg, Weizsäcker) in 1941 had a rough estimate of the necessary efforts to build a bomb, they only asked for a budget of less than 1/1000th of that of the Manhattan project. The German physicists tried to build a nuclear reactor. But even that project they pursued with limited eagerness considering for instance, that they had plenty of time to organize seminars and to publish papers about a variety of other scientific and non-scientific subjects.

At the outset of war, in 1939 Weizsäcker and Heisenberg decided to participate in the German uranium project. At that stage it was not clear, as some later have argued, that without Heisenberg, building a bomb would have been impossible in Germany. It was not even sufficiently clear whether a chain reaction could be technically realized. If one wanted to prevent Hitler from getting an atomic bomb it was necessary for any course of action to judge how difficult building a bomb would be. In 1941 Weizsäcker and Heisenberg were convinced that building a bomb would take much longer than the war could possibly last. Early in 1942 the uranium project was released from military supervision. This course of events, as far as I can tell, is indisputable. It does not support Bernstein’s claim that Weizsäcker and Heisenberg were “eager” to build a bomb. Other than that, Bernstein seems to base his opinion on what Heisenberg is reported to have said publicly during that time. However, since Heisenberg wanted to keep control of the German uranium project—he never was working in the direction of a bomb—he had to negotiate and even to cooperate to some extent with Nazi officials. What he said in public during that period had to be phrased carefully not to arouse their suspicion. Bernstein does not acknowledge this basic condition of totalitarian regimes.

I believe that it is valid and even necessary to discuss whether Heisenberg’s decisions were right. Would it have been better to emigrate and to leave the German nuclear energy project to others? What could you say in Nazi Germany if you did not want to jeopardize your own plans? But these are not the questions Bernstein is raising. In contrast to Weisskopf he wants to make the reader believe that unlike the American and exiled scientists who joined the Allied bomb project, Weizsäcker and Heisenberg did not care about the moral issues involved. This is absurd. Niels Bohr, e.g. never questioned Heisenberg’s integrity. After the war their personal relations continued although their friendship remained somewhat strained.

The most surprising statement of Bernstein is his attitude towards the published excerpts of the Farm Hall tapes. He writes: “The closest we can get to what Heisenberg really thought at the time, in my opinion, are the parts of the so-called Farm Hall transcripts that have found their way into books written by some of the few people who had access to them.” It does not seem to occur to him that he is dealing with isolated excerpts of translations of transcripts of hundreds of thousands of hours of tapes. The excerpts were selected for, and used in the memoirs of people (Goudsmit, Groves, Jones) who had been deeply, some of whom even tragically involved in this relevant episode of history. Never has one of the taped persons had the opportunity to listen to the tapes, check the translation and to identify the context of the passages cited. Who says that the British intelligence does not want to offend German sensibilities by not publishing the tapes. It may well be that other reasons prevail.


In his review Bernstein cites Heisenberg from the quotation of transcripts in L.M. Grove’s book. He then admits that the meaning is rather obscure and even concedes that the original German would be helpful. Nevertheless, he does not hesitate to derive from these quotations his accusation that after Hiroshima, Weizsäcker and Heisenberg “started a conscious effort to distance themselves from their war efforts.” No, during the war they had made a conscious effort to conduct the nuclear energy project at the pace and into the direction they wanted it to go.

Bernstein finally also disqualifies himself as a historian by the way he portrays Ernst von Weizsäcker, Carl Friedrich von Weizsäcker’s father, as a Nazi collaborator. He should know that this part of the Nürnberg Trials has since been the most debated and that the original sentence of seven years was soon reduced to five years and E. v. Weizsäcker was released already a few months after the revision. The jury consisted of three US judges, no Europeans. One of them pleaded innocent. Weizsäcker was closely associated with the German resistance and Winston Churchill called his sentence a “deadly error.”

After that, the mistake in the last sentence of Bernstein’s reply in which he makes Richard von Weizsäcker, Ernst von Weizsäcker’s youngest son, President of the German Democratic (sic) Republic may be considered a minor lapse. It seems, however, indicative of the lack of thoroughness which he exerts in dealing with the data. Highhanded moral judgements about people based neither on first hand knowledge of the subject nor on a scrupulous evaluation of the available documents are irresponsible and even dangerous.

What Bernstein does not know is that in 1978 S. Goudsmit a few months before his death approached my brother Jochen at the Annual Meeting of the American Physical Society and apologized about what he had done to Werner Heisenberg and distanced himself from what he had written about him.

Professor Dr. Martin Heisenberg
Reichenberg, Germany

Jeremy Bernstein replies:

Both the tone and the content of Professor Doctor Heisenberg’s letter invite a reply. As for the tone, the simple fact is that, during the war, people like his father and von Weizsäcker made a number of damaging compromises with a despicable regime. What one might have hoped for from such people, after the war, was a simple statement to the effect, “It was wrong. We were wrong. We are sorry.” Instead there has been from them a steady stream of denial, often bordering on a rewriting of history. Dr. Heisenberg’s letter is an excellent example of the genre.

  1. I never said that the Germans planned to use a “nuclear reactor as a bomb.” I was referring to the reaction of the people at Los Alamos when they were shown the drawing Heisenberg gave Bohr at their illfated meeting in Copenhagen in the fall of 1941. Bethe said to me, “Later on, at Los Alamos, this drawing [which, incidentally, seems to have disappeared] was transmitted to us by Bohr. It was clearly a drawing of a reactor, but when we saw it our conclusion was that these Germans were totally crazy—did they want to throw a reactor down on London?”2 I then went on to add, “In retrospect, the German scientists were not crazy at all. They knew perfectly well what to do with a reactor, and this drawing was of the reactor that Heisenberg tried throughout the war to build but was unable to finish.”
  2. My reading of as many of the relevant documents as I have been able to get hold of, as well as talking with a great many of the contemporary physicists, has convinced me that from September 1939, when Heisenberg, von Weizsäcker, and others, were ordered to report to German Army Ordnance, until 1942, when Speer became convinced that a nuclear weapon could not be built quickly enough to influence the outcome of the war, these men worked with enthusiasm to attempt to make a nuclear weapon. They also realized that if they could make a reactor they could extract weapons grade plutonium from it. The statement that “he [Heisenberg] never was working in the direction of a bomb,” is, as far as I am concerned, total nonsense.
  3. The question of what someone in Heisenberg’s position had to do to survive in a totalitarian regime is very troubling. Not having been in his situation, I cannot state with certainty how I would have behaved. Can anyone? German physicists and their families engaged in a wide spectrum of behavior. At one end was Max Planck’s son Erwin, who was executed for having taken part in the July 1944 plot against Hitler; at the other, was the physicist Philipp Lenard, an early Nobel Prize winner in physics and an early and enthusiastic Nazi. Many of Heisenberg’s senior contemporaries such as von Laue. Hilbert, Sommerfeld, and Planck himself, practiced varying kinds of passive resistance and were unwilling to have anything to do with the regime. Heisenberg and von Weizsäcker do not fall into any of these categories. They were never members of the Nazi party, but there is clear evidence, from reliable sources, that during the war, they wanted Germany to win. To keep their positions in German science they made compromise after compromise with the regime. In my view, and I shall give a specific example below, these compromises went well beyond Dr. Heisenberg’s characterization: “What he said in public during that period had to be phrased carefully not to arouse their suspicion.”
  4. I did not take up the question of why Heisenberg did not choose to emigrate since, in fact, he did not choose to do so. Since the matter has been raised I should note that unlike many German scientists who had great difficulty in emigrating, Heisenberg would have had no trouble in doing so. He had offers of jobs from several places, including Columbia University, and he had an uncle who was well-established financially in the US. He also had many former European colleagues here, such as Fermi, who pointed out to him the consequences of choosing to remain in Germany. He gave various reasons for his decision, including his patriotic feelings about Germany. He also told I.I. Rabi, who told me, that he was worried that if he left Germany he would lose his place in the German academic hierarchy. Throughout his career Heisenberg had a very competitive attitude toward his position on the academic ladder. In view of what was then happening to the German universities this may seem almost incredible; but there it was. He also felt that he might be able to protect some of the young physicists from being swallowed up by the military machine. In this he was partially successful and that is to his credit. I do not know what the sentence “What could you say in Nazi Germany if you did not want to jeopardize your own plans?” is supposed to mean. Plans for what?

  5. I am also puzzled by Dr. Heisenberg’s statement that “Niels Bohr, e.g., never questioned Heisenberg’s integrity. After the war their personal relations continued although their friendship remained somewhat strained.” If Bohr never questioned Heisenberg’s integrity why then was their friendship “strained”? In fact, the visit of Heisenberg and von Weizsäcker to Copenhagen in 1941 was a very traumatic experience for Bohr. Bohr apparently suspected that Heisenberg was attempting to probe his knowledge of the Allied attempts to build nuclear weapons. Some sense of Bohr’s reaction to this visit can be inferred from a comment made by his wife, Margrethe, who is quoted as saying, “No matter what anyone says, that was a hostile visit!”3 From that visit on, Bohr’s feelings about Heisenberg changed.


  6. It is quite possible that Groves, and others, used the Farm Hall transcriptions selectively. (One imagines that the originals were not “tapes” but some sort of plastic record. I have no idea whether the original recordings still exist or in what form the transcripts can be found.) For this reason, as well as many others, it is crucial to our understanding of what happened that these transcripts be released. Delaying the release has made it almost impossible for any of the survivors to check their validity. Apart from von Weizsäcker, who has never been enthusiastic about the release of these transcriptions, I am not sure if any of the original detainees are still alive. I would suggest that Dr. Heisenberg join those of us who have been trying to urge the British government to release these documents. He might start by urging the president of Germany, Richard von Weizsäcker (I regret my mistake in identifying him), to speed up this process by contacting his British counterparts. We would then see in what direction Heisenberg, von Weizsäcker, and the others “wanted it [nuclear energy] to go.”

  7. That Ernst von Weizsäcker was convicted as a war criminal at the Nuremberg trials remains a fact, and one that is not affected by Dr. Heisenberg’s comments on the reduction of his sentence. The statement that “Weizsäcker was closely associated with the German resistance” is entirely new to me. I have no idea what resistance Dr. Heisenberg is talking about. If he has documented evidence for this remarkable statement, I would be grateful to see it.

  8. What Sam Goudsmit actually said to Dr. Heisenberg’s brother in 1978 and just what he might have “apologized” for is not clear from his letter. Nor do I know what is meant by the phrase “distanced himself from what he had written about him.” Sam Goudsmit was a very decent man and I doubt that he would want to cause unnecessary injury to anyone. I also doubt that his views on the wartime activities of Heisenberg and von Weizsäcker had changed all that much. As I have stated previously, Goudsmit himself acknowledged that there were flaws in his book Alsos; but the book was important in opening up the question of the behavior of the German scientists during the war. Others have now done more careful historical work, but Goudsmit prepared the way.

One of the important things to emerge from the book, and subsequent ones, is the nature of the compromises that Heisenberg and von Weizsäcker were willing to make to carry on their work under the Nazi regime. I will give one specific illustration. Within Germany, during this period, there were two kinds of physics; crudely speaking, “German physics” and “Jewish physics.” The relativity theory and the quantum theory were included among the latter. However, at the heart of the science of nuclear energy lie both these theories. Nuclear energy is, after all, the canonical illustration of Einstein’s formular E=mc2.

To deal with this, some of the leading German physicists, such as Heisenberg and von Weizsäcker, concocted the strategy of finding suitable Aryan precursors of Einstein to whom they could attribute his theory. Particularly useful for this purpose was an Austrian physicist named Friedrich Hasenhorl. He had been Schrödinger’s teacher and had, conveniently, been killed as a soldier in the First World War. He had had some vague intimations about the connection between mass and energy and this was seized on to make him its inventor and thus legitimate the use of the idea. During the war there was a struggle between physicists like Heisenberg, who wanted to make use of any physics they saw fit, and the more primitive advocates of “German physics.”

This conflict came to a head in November of 1942 at a meeting in Seefeld in the Tyrol. Von Weizsäcker, who was at the meeting, was one of the authors of a report that stated, in part “before Einstein, Aryan scientists like Lorentz, Hasenhorl, Poincaré, etc., had created the foundations of the theory of relativity, and Einstein merely followed up the already existing ideas and added the corner stone.”4 In 1943 Heisenberg who had been at the Seefeld meeting, published an article entitled The Value of Modern Theoretical Physics, which was approved by the SS. In it he again argued that the special theory of relativity would have come about without Einstein; that its history should be forgotten. In later years, after the war when it was safe to do so, Heisenberg acknowledged that it was a conversation with Einstein that led him to formulate his uncertainty principle. One may well ask why did Heisenberg write his 1943 article at all? Was this part of not arousing “suspicion?” Wouldn’t silence have sufficed?

This Issue

January 16, 1992