Volume 29, Number 4, October 2000


Copenhagen in New York

Harry Lustig and Brian B. Schwartz

Near the beginning of his unreservedly enthusiastic review on April 12, 2000 of Michael Frayn’s play Copenhagen, the New York Times’ critic Ben Brantley asks: "…who would have ever thought it, that three dead, long-winded people talking about atomic physics would be such electrifying companions?"

The play reenacts the 1941 visit of Werner Heisenberg, who was then in charge of the Nazi nuclear power program, to Niels Bohr, his mentor, and collaborator in creating quantum mechanics, complementarity, and the uncertainty principle, in German - occupied Denmark. The third "long-winded" character is Bohr’s wife Margrethe. "Reenacts" is not really the right word, for no one now alive appears to know what actually took place during the visit and Frayn does not pretend to solve the mystery.

We do know that something terrible happened between the two friends, which all but destroyed their relationship for the rest of their lives. Speculation about the intent of Heisenberg’s call has been rife among physicists and historians ever since the visit became known. Did Heisenberg want to warn Bohr and through him the Allies that the Germans were working on an atomic bomb and if so to what end? Was it to convey the impression that he was about to succeed and that the Allies should therefore make peace with Hitler, or was it say that he had given up on an impossible task and that therefore the other side shouldn’t try either? Did Heisenberg want to find out whether the Allies were actually working on an A - bomb? Or did he hope to convince Bohr to issue a joint declaration with him denouncing efforts to build a bomb and pledging not to work on it?

And inevitably historians and scientists have debated the corollary question: why did the Germans not achieve an atomic bomb and, indeed, why, as became known as a result of Samuel Goudsmit’s Alsos mission at the end of the War, were they, under Heisenberg, not even trying, but were working instead to build a nuclear reactor for the production of energy? Was it because of incompetence, or was Heisenberg dragging his feet or denying the feasibility because he didn’t want Hitler to have the bomb?

By replaying parts of the Copenhagen encounter three times with different variations, after the protagonists’ deaths (we aren’t told whether they met in heaven or hell), Frayn illuminates the questions, but does not resolve them. But he does much more: he delivers a mini-course in Quantum Mechanics for Poets, including fair explanations of the uncertainty principle and of complementarity, which he then - most physicists and philosophers of science would agree, gratuitously - applies to human behavior: we must always be uncertain what is in a person’s mind, and we all have complementary motives for our actions. Inevitably, the play raises important and difficult moral questions. One - which, it turned out, would understandably provoke some in the audience at our symposium - was who had more on his conscience: Heisenberg, whose work in nuclear physics during the War did not result in the death of a single human being, or Bohr, who at Los Alamos contributed to building the atomic bomb, which did kill thousands of people.

Both of us had read the play Copenhagen [1] with considerable interest, even excitement, and pleasure, and had heard from Eugen Merzbacher, who had seen the well-received production in London, that it worked. Nevertheless, we must admit to doubts, similar to those later enunciated by Mr. Brantley, that many people in the Broadway audience, other than a few academics, would come to or sit through what could be perceived as a seminar on physics, philosophy, and history. But one of us (B.B.S. ) was a reader for the Ensemble Studio Theater - an of-off Broadway group -which had been given a grant by the Sloan Foundation to promote plays and other artistic works with scientific and technological themes. Having learned that the Ensemble Studio Theatre was planning to invite Michael Frayn to speak about the play in New York before its official opening, Schwartz offered the facilities of the CUNY Graduate Center for the event and suggested that it be expanded into a symposium with additional participants. The other author of this article (H.L. ) would find himself in New York City in January and February and together we planned the program of the symposium and selected and obtained the speakers. Schwartz acted as the overall, busy producer of the day-long event, while Lustig compiled the biographical sketches of the speakers and of the protagonists and most of the forty-three physicists, from Born to von Weizsaecker, whose names are - not at all inappropriately - dropped in the play. The symposium was to, and did take place, on Monday, March 27, at the Graduate Center’s newly occupied, but not yet officially opened or completely ready building on New York’s Fifth Avenue (in the former home of the B. Altman’s department store). We also arranged that a preview performance of Copenhagen on the day before would be attended by most of the speakers and by physicists and other attendees at the symposium who had been invited by the American Physical Society and the American Institute of Physics.

The symposium was to consist of three sessions. The evening session on Theatrical Perspectives, which we thought would attract the largest audience because of its popular appeal and the participation of Michael Frayn and the equally renowned director of the play, Michael Blakemore, would be the responsibility of the Ensemble Studio Theatre. We would organize a session on Science and one on History. In choosing the speakers, we aimed high, and our aim was good: all but one of those on our "A list" accepted with grace, even alacrity, including the ninety-three years old Hans Bethe, whom we had to track down at Cal Tech where he was a visiting professor from his home institution, Cornell. The merely eighty-nine years old John Wheeler had to travel only from Princeton. Both Bethe and Wheeler had of course known Bohr and Heisenberg before and after World War II

The Science Session, chaired by Jerome Friedman of MIT and Daniel Greenberger (CCNY), began with a talk which was intended to provide the audience with a basic understanding of some fundamentals of nuclear physics in general and fission in particular, and in the twenty minutes available to her, Fay Ajzenberg-Selove (University of Pennsylvania) discharged this assignment admirably. This was followed by an impeccable and exciting presentation by Eugen Merzbacher (University of North Carolina) of the fundamentals of quantum mechanics and of the consequences for entangled states of the Copenhagen interpretation. Anton Zeilinger (University of Vienna) described some of his group’s elegant experiments on entangled states, which shore up the Copenhagen interpretation. And Brian Greene(Columbia), claiming unconvincingly that his presentation was mainly to provide comic relief, presented contemporary alternatives (including that of parallel universes) to the Bohr interpretation.

The session on History was, for some, the highlight of the event, for it provided rather convincing answers to some of the questions that figure in the play and that are asked at the beginning of this report. Hans Bethe asserted unequivocally and convincingly, on the basis of his experience at Los Alamos, his interaction with the protagonists, and his study of the recently released tapes of conversations between Heisenberg, Otto Hahn and other German scientists who were interned in England , at the conclusion of World War II, that Heisenberg and his team did not work on the Atomic Bomb, because they were sure that it could not be built. Heisenberg reached this conclusion, because, unlike in the United States, there were no people with training or interest in chemical engineering in Germany to tell him that graphite would be a suitable moderator in the chain reaction if it could be made boron-free, and because he failed to calculate the critical mass in the belief that it required tons of enriched uranium [2].

Complementing this account, the physicist, science historian, and Heisenberg biographer David Cassidy (Hofstra University) argued effectively that Heisenberg’s actions and inactions should not be attributed primarily to moral motives [3]. His justification for staying on in Nazi Germany and heading up the atomic energy effort, that he only wanted to preserve German science for the time after the expected and hoped for downfall of Hitler, was not convincing to Cassidy. Even though Heisenberg was offered positions in the United States, and although some other German scholars, including his brother-in-law, the economist E. F. (Fritz) Schumacher [4] had emigrated out of disgust with Nazism, he had no intention of giving up his prestigious chair at the University of Leipzig.

Also in keeping with the view of a morally vulnerable Heisenberg, Gerald Holton (Harvard) presented the results of his research on the once close but, after 1933, deteriorating scientific and personal relationship between Heisenberg and Einstein [5]. Tantalizingly, Holton also reported on the existence of a letter from Bohr to Heisenberg, that was shown to him in 1985 by one of Bohr's sons, Erik. The letter resides in the Copenhagen archives. The release of the content in 2012 (fifty year's after Bohr's death) may finally answer the question "what happened in Copenhagen in 1941?"

In a departure from the other speakers, John Wheeler treated the audience to his personal impressions of the play’s protagonists, Niels Bohr and Werner Heisenberg. While declaring his admiration for both of them, he admitted his discomfort, shared by many other American physicists, when Heisenberg reappeared in the United States after the War. At a party for Heisenberg, Wheeler made sure always to hold a drink in one hand and a notebook in the other, so as to be visibly unable to shake his hand. When Wheeler started to recount a visit to Auschwitz soon after the end of the War (perhaps to explain his antipathy to Heisenberg), he broke down and was unable to continue his talk. The history session was chaired by Frederick Seitz (Rockefeller University) , who also contributed remarks about the contribution, after his release from the Soviet Union, of the chemist Nikolaus Riehl, to the German effort to produce reactor-grade uranium [6], and by Spencer Weart of the AIP Center for History of Physics.

After the History Session, the speakers, organizers and sponsors of the symposium were treated by the Royal Danish Consulate to a dinner as might have been tendered by the Bohrs to their guests in the "House of Honor" they occupied on the grounds of the Carlsberg brewery in Copenhagen. One of us was surprised to discover that the young Danish journalist at his table knew as little about Bohr as his American contemporaries.


A bonus event on the morning of the symposium, for members of the APS, was the opening of the New York showing of the exhibit "To Advance & Diffuse the Knowledge of Physics: 100 Years of the American Physical Society". This historical exhibit was conceived and constructed for the APS’ centennial celebration, and had been shown, to much acclaim, in Atlanta and in the Washington area. After opening remarks by Jerry Friedman, APS’ President during the centennial year, the exhibit’s curator, Sara Schechner, conducted a guided tour of the exhibit. Although it covered the entire history of the APS and therefore, inevitably, much of physics in the 20th century, the connection with Copenhagen was much in evidence: one of the exhibits in the "journals section" was the authoritative 1939 paper by Bohr and Wheeler explaining fission, and both the contributions to the Second World War by physics and the War’s effect on physics were well documented

The Theatre Session, in the evening - for which the entire day’s events had been given the name Creating Copenhagen - lived up to its billing. Michael Frayn showed convincingly that he had steeped himself in the history of the period and had assimilated much of the physics. He also pointed out what in the play was dramatic invention and why it was introduced. (One of the inventions, the personality of Margrethe Bohr, clearly disturbed some members of the audience who had known her. Regal [she was known in Denmark as "Queen Margrethe"], highly competent, polite and the perfect hostess, her role in the play was that of an skeptical and even aggressive antagonist of Heisenberg. ) An even more impressive presentation of Frayn’s approach to writing the play can be found in his Postscript to Copenhagen, an essay originally prepared for the London production’s playscript edition and expanded for the New York production [1].

Michael Blakemore’s literate and incisive presentation of how he saw the play went a long way to explain why he recently won the year 2000 Tony Award for best director of a drama (our sense of honesty, or perhaps wonderment compels us to disclose that Blakemore won a second Tony for his direction of the musical Kiss Me, Kate), and why Copenhagen itself was designated as the best play. Blair Brown, the actress who plays Margrethe Bohr, was given the "best supporting actress" award. Many viewers felt that Philip Bosco (Niels Bohr) and especially Michael Crumpsty who portrays Werner Heisenberg also deserve major awards. Blair and Crumpsty attended part of the Science and all of the History Session of the symposium, and we would like to think that this helped them to give even more insightful performances than they would otherwise have done.

For pictures of the play, click here

For pictures of the symposium, click here for the science part of the symposium, herefor Hans Bethe being excorted on stage for the history part of the symposium, or here for the history part of the symposium.

All of the many reviews of Copenhagen we saw, except two, including those in all the New York papers, the (unusual) reviews in out-of-town papers such as the Washington Post and the Baltimore Sun, and an essay by Thomas Powers (who has been the leading proponent of the theory that Heisenberg deliberately dragged his feet on building a bomb, because he didn’t want Hitler to get one ) in the New York Review of Books [7], were unreservedly enthusiastic. In addition to praising the performance and production, they take a highly favorable view of the content of the play and consider it the most important intellectual theatrical event in many decades. One critic, John Lahr in the New Yorker, found and deplored that Copenhagen lacks entertainment value, and we have to admit that it isn’t The Wizard of Oz. And Paul Lawrence Rose, Professor of Jewish Studies and European History at Pennsylvania State University, in The Chronicle of Higher Education condemned Copenhagen generally for its postmodernist sin of asserting that physics and history have "no more underlying truth than alchemy", and specifically for whitewashing Heisenberg and for coming close to asserting that there was no moral difference in the Second World War between Germany and the Allies [8].

Not only the play, but also the symposium received favorable reviews from the audience and from the press. And it was not only science publications such as Physics Today, APS News, and Chemical and Engineering News that gave it coverage. The physicist-turned- science -journalist, James Glanz, not only reviewed the event in the New York Times, but he and others gave it and with it the play considerable advance publicity. Thus the symposium may have made a contribution to the attentiveness, even eagerness with which Copenhagen was awaited and received. There was also television coverage, including interviews by CNN and Japanese Television with Hans Bethe and John Wheeler.

The effect on the large audience at the symposium was palpably more direct and significant. We had expected that the potential audience for the evening session with Frayn and Blakemore would exceed the 400 seat capacity of the auditorium and had therefore limited admission to those who had obtained (the free) tickets in advance. But as it turned out, the auditorium was also full for the Science session, and several hundred people had to be turned away from the History session, in spite of the fact that an overflow hall which showed the program on closed circuit television had been made available; it was quickly filled. All these people were exposed to and - we hope - learned a good deal of physics, its history, and its important role in human affairs, an enterprise which the APS, the AIP, and much of the physics community see as essential to pursue, if physics is to prosper, and in the pursuit of which they expended a great deal of effort and money. Not that the symposium came free; indeed its expenses were, in large measure, defrayed by APS, AIP, the CUNY Graduate Center, and by a generous New York based foundation.

The symposium [9] was a great day for physics. But it wouldn’t have been held had there been no Copenhagen, and Michael Frayn’s play is manifestly the more important and lasting event. As a recognition of his contributions to physics will the APS make Frayn a Fellow of the Society?


[1] Michael Frayn, Copenhagen, Methuen, London (1998). In the American edition, published by Anchor Books, New York (2000), the author made minor changes in the text of the play and expanded the Postscript on the basis of communications to him by physicists and historians and of further reading.

[2] Hans A. Bethe, The German Uranium Project, Physics Today 53, 34 - 36 (July 2000).

[3] David C. Cassidy, A Historical Perspective on Copenhagen, Physics Today 53, 28 - 32 (July 2000). See also Casssidy's biography of Heisenberg, Uncertainty: The Life and Times of Werner Heisenberg, W. H. Freeman, New York (1992). An excellent biography of Bohr, particularly for physicists, is Abraham Pais, Niels Bohr's Times, Oxford University Press (1991).

[4] Schumacher (1911 - 1977) had a distinguished career in England in economics. Among other positions he was head of planning at the British Coal Board. At the same time he was an ardent environmentalist and achieved world-wide popular fame for his book Small is Beautiful.

[5] Gerald Holton, Werner Heisenberg and Albert Einstein, Physics Today 53, 38 - 42 (July 2000).

[6] Nikolaus Riehl and Frederick Seitz, Stalin's Captive: Nikolaus Riehl and the Soviet Race for the Bomb, American Chemical Society and the Chemical Heritage Foundation (1996).

[7] Thomas Powers, The Unanswered Question, The New York Review of Books (May 25, 2000). Powers' earlier views on why Heisenberg did not build an atomic bomb are given in his book Heisenberg's War: The Secret History of the German Atomic Bomb, A. A. Knopf, New York (1993)

[8] Paul Lawrence Rose, Frayn's "Copenhagen" Plays Well at History's Expense, The Chronicle of Higher Education, B 4 -6 (May 5, 2000). Rose's views on Heisenberg's role and behavior are expressed in more detail in his book Heisenberg and the Nazi Atomic Bomb Project: A Study in German Culture, University of California Press (1998).

[9] The Creating Copenhagen Symposium was video-recorded. The set of three tapes, in VCR format - one for each of the sessions - will be mailed to individuals who send a check for $30, made out to

The Graduate Center, to

Creating Copenhagen Tapes

The Graduate Center of the City University of New York, Room 8 309

365 Fifth Avenue

New York, NY 10016.

The program of the Symposium and the biographical sketches of the speakers and of scientists mentioned in the play, can be found at http://web.gsuc.cuny.edu/ashp/nml/copenhagen


Harry Lustig has worked in theoretical nuclear physics. He is professor of physics emeritus and provost emeritus at the City College of the City University of New York, Treasurer Emeritus of the American Physical Society, and Adjunct Professor of Physics and Astronomy at the University of New Mexico. :

304 Chula Vista Street, Santa Fe, NM 87501.


Brian Schwartz, a condensed matter physicist, has been a member of the faculty at MIT and served as Deputy Executive Secretary and as Education Officer of the American Physical Society. He is one of the founders of APS’ Forum on Physics and Society and is Vice President for Research and Sponsored Programs

Graduate Center of the City University of New York

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