Copenhagen: On the verge of the nuclear age
An introduction to the play Copenhagen (1998) by Michael Frayn
March 20, 2018

Nicola Cufaro Petroni
USPID (Unione degli Scienziati per il Disarmo, Bari)
CIRP-UniBa "Giuseppe Nardulli" (Centro Interdipartimentale di Ricerche sulla Pace, Bari)

In September 1941 a meeting occurred in the occupied Copenhagen between Niels Bohr and Werner Heisenberg: their exchange, however, quickly turned sour and the two physicists abruptly parted. Nobody knows what exactly was said that night, but everybody agrees that the talk was about the (allied and German) nuclear weapons projects prompted by the recent (decembre 1938) discovery of the nuclear fission. Much of the initial controversy stemmed from a 1956 letter Heisenberg sent to the journalist Robert Jungk where he mantains that he had come to Copenhagen to discuss with Bohr his moral objetions toward scientists working on nuclear weapons, but also that he had failed to say this clearly before the conversation came to a halt. Bohr was outraged after reading these staments feeling that they were false and that instead the 1941 meeting had proved to him that Heisenberg was quite happy to produce nuclear weapons for Germany. Heisenberg historians remain divided over their own interpretations of the event, and Michael Frayn's 1998 play Copenhagen brought more public attention to a topic that had previously been confined
just to a scholarly discussion

On March 19-20, 2018 the Teatro Pubblico Pugliese staged in the Teatro Petruzzelli (Bari, Italy) a reprise in italian of Frayn's play performed by the Compagnia Umberto Orsini. The occasion was not lost to organize two public discussions (March 14 for university students, and March 20 for the general public in the Foyer of the Teatro Petruzzelli) about the moral, political, historical and technical issues popping up all along the dramatic action. One of the two introductory talks was entrusted to this author: following are a few documents, either assembled or surveyed to prepare the presentation, which are listed here in cronological order to the advantage of people interested in these topics. The bibliography of the papers and books quoted is, however, far from complete


Hans Bethe:
Energy production in stars
, Phys. Rev. 55 (1939) p. 103, Letter to the Editor
Energy production in stars, Phys. Rev. 55 (1939) p. 434
The possibility of extracting energy from a fusion chain reaction was recognized in these two papers written in the spring of 1938, namely before the fission experiments by
O. Hahn and F. Strassman in December 1938. For this discovery of the reactions which supply the energy in the stars Bethe was awarded the 1967 Nobel Prize in Physics 

Lise Meitner and Otto R. Frisch
Disintegration of Uranium by Neutrons: A New Type of Nuclear Reaction, Nature 143 (1939) p. 239
This is the celebrated Letter to the Editor of February 11, 1939 where Meitner and Frish first announced their interpretation of the empyrical results - December 1938 - of O. Hahn and F. Strassman as a fission (this term is here adopted for the first time) of the Uranium nucleus

Niels Bohr and John A. Wheeler:
The Mechanism of Nuclear Fission, Phys. Rev. 56 (1939) p. 426
On the basis of the liquid drop model of atomic nuclei, an account is given of the mechanism of nuclear fission: it is the first fully worked out theory of this newly discovered phenomenon and it laid the groundwork for atomic and hydrogen bombs. These results were still published at that time, and the reported publication date is the fateful September 1, 1939: the start of World War II with the german invasion of Poland

Otto R. Frisch and Rudolf Peierls:
Memorandum (unpublished, March 1940)
The Frisch–Peierls Memorandum was the first technical exposition of a practical nuclear weapon. It was written by expatriate German physicists Otto Frisch and Rudolf Peierls in March 1940 while they were both working for Mark Oliphant at the University of Birmingham in England during World War II. The memorandum contained the first (rather underestimated) calculations about the size of the critical mass of fissile material needed for an atomic bomb. It revealed for the first time that the amount required might be small enough to incorporate into a bomb that could be delivered by air. It also anticipated the strategic and moral implications of nuclear weapons. It helped send both Britain and America down a path which led to the MAUD Committee, the Tube Alloys project, the Manhattan Project, and ultimately the atomic bombings of Hiroshima and Nagasaki.

Robert Serber and Edward U. Condon:
The Los Alamos
Primer (unpublished, April 1943); original typed version
The Los Alamos Primer was a printed version of the first five lectures on the principles of nuclear weapons given to new arrivals at the top-secret Los Alamos laboratory during the Manhattan Project. They were originally given by the physicist Robert Serber after being delivered in person on April 5–14, 1943, based on conclusions reached at a conference held in July and September 1942 at the University of California, Berkeley by Robert Oppenheimer. The notes from the lecture which became the Primer were written by Edward Condon. The Primer contained the basic physical principles of nuclear fission, as they were known at the time, and their implications for nuclear weapon design. It suggested a number of possible ways to assemble a critical mass of uranium-235 or plutonium. Though its information about the physics of fission and weapon design was soon rendered obsolete, the Primer  is still considered a fundamental historical document in the history of nuclear weapons. Its contents would be of little use today to someone attempting to build a nuclear weapon, a fact acknowledged by its complete declassification in 1965. In 1992, an edited version of the Primer with many annotations and explanations by Serber was published with an introduction by Richard Rhodes.

The Franck Report (unpublished, June 1945); transcribed version
The Franck Report was a document signed by several prominent nuclear physicists recommending that the United States not use the atomic bomb as a weapon to prompt the surrender of Japan in World War II. The report was signed by James Franck (Chairman), Donald J. Hughes, James J. Nickson, Eugene Rabinowitch, Glenn T. Seaborg, Joyce C. Stearns, and Leó Szilárd, it spoke about the impossibility to keep the United States atomic discoveries secret indefinitely, and finally it predicted a nuclear arms race. As a consequence it recommended that the nuclear bomb not be used, and proposed that either a demonstration of the "new weapon" be madeon a barren island or desert, or to try to keep the existence of the nuclear bomb secret for as long as possible. However the Interim Committee, appointed by President Truman to advise him on use of the atomic bomb, met on June 21 to reexamine its earlier conclusions and it reaffirmed that there was no alternative to the use of the bomb

Samuel A. Goudsmit:
 Alsos (1947; American Institute of Physics, 1996)
The Alsos Mission was created following the September 1943 Allied invasion of Italy with a twofold assignment: search for personnel, records, material, and sites to evaluate the German programs and prevent their capture by the Soviet Union. It was established as part of the Manhattan Project's mission to coordinate foreign intelligence related to enemy nuclear activity. The mission, terminated on October 15 1945, was commanded by Colonel Boris Pash, a former Manhattan Project security officer, with Samuel Goudsmit as chief scientific advisor.  Alsos teams took most of the senior German research personnel into custody, including the ten leading german physicists that ended up in Farm Hall (see later). The book is a lively account of these operations by one of its protagonists.

David Irving:
The Virus House
(W. Kimber&co, 1967; published in the USA as The German Atomic Bomb, Simon and Schuster, 1967)
A complete history of the German atomic bomb project written by the controversial british historian of the holocaust. It is maybe not techically very accurate, but it presents a comprehensive and reliable narrative of the project from the unusual standpoint of the nazi Germany. The account of the heavy water battle and of the Hydro factory sabotage in Norway reads as a spy novel. The book has been written before the publication of the Farm Hall transcripts, but the author is aware of their existence and partially of its contents. In his opinion the German scientists had a rather precise idea of a reactor functioning, and even of the critical mass of a uranium weapon: their failure is credited to the fateful error of relying on heavy water as moderator (instead of graphite), and primarily to the political, economical and social environment prevalent in Germany

Otto R. Frisch and John A. Wheeler
The discovery of fission
, Physics Today 20 (1967) p. 43
An account of this scientific breakthrough by two of its protagonisgts: especially relevant for us are the lines where the role of N. Bohr is elucidated in figuring out the importance of the isotope U-235 and in discussing the possibility of  making a bomb out of it

Stanley Goldberg and Thomas Powers:
Declassified Files Reopen "Nazi Bomb" Debate, Bulletin of the Atomic Scientists 48 (1992) p. 32
An early discussion of the newly declassified (in February 1992) Transcripts of Farm Hall which are the starting point of a number of subsequent studies, books and dramatizations, including the play Copenhagen by M. Frayn (1998). In particular the paper already points out the nowadays common dilemma about the Heisenberg's claims of a moral explanation for the humiliating German failure to produce the bomb.

Jeremy Bernstein:
The Farm Hall Transcripts: The German Scientists and the Bomb
, New York Review of Books, August 13, 1992
Another paper quoting and discussing notable excerpts from the declassified transcripts. At variance with S. Goldberg and T. Powers, J. Bernstein is a physicist and is consequently more accurate (here and specially in his subsequent book - see later - on the same argument) in discussing the technical points regarding, for instance, the critical mass calculations of Heisenberg and his possible mistakes.

Hitler's Uranium Club, The Secret Recordings at Farm Hall (Springer, 2001; first published by Woodbury, New York 1996)
Edited and annotated by Jeremy Bernstein, with an Introducrtion by David Cassidy
This is a complete edition of the Farm Hall Transcripts declassified in 1992 with an Introduction by Cassidy, and a rather comprehensive Prologue (more than fifty pages, an essay in its own right) about the German bomb project by Bernstein. The other interesting feature of the book are the extensive and careful annotations to the dialogues of the transcripts added by Bernstein to elucidate every detail and their relevance. Being Bernstein himself a physicist, a few of his remarks are also rather more thechnical (albeit far from demanding) of what one could expect in a publication for a general public. All of this book makes a very interesting reading and looks quite sober abouth these otherwise rather rancorous and quarrelsome topics.

Paul L. Rose:
Heisenberg and the Nazi Atomic Bomb Project, 1939-1945: A Study in German Culture
(University of California Press, 1998)
A substantial book which is rather disparaging about the role of Heisenberg and his compromises with the nazi regime. His positions about the moral pretensions ascribed to the German physicist by a few analysts (and constituting the core of Copenhagen, the Frayn play) are also well summarized in the exchange with T. Powers on the New York Review of Books referred later on. 

Michael Frayn:
Copenhagen, a play (1998)
A fashionable dramatization of the enigmatic meeting of Bohr and Heisenberg in the occupied Copenhagen on September 16, 1941, at a time when the German Uranverein already existed, albeit with a few hurdles of its own, and the Manhattan Project was just on the verge of starting. The meeting ended abruptly in disagreement, but the two protagonists were never subsequently able to concur in what exactly was said that night. The play ends with a postscript by the author himself elucidating the historical, politcal and moral background of his work.

Thomas Powers:
The Unanswered Question
, New York Review of Books, May 25, 2000
and his subsequent exchange with
Paul L. Rose:
Heisenberg in Copenhagen
, New York review of Books, October 19, 2000
The Powers paper is a review of the Frayn's play american reprise which opened on April 11, 2000 in New York. The author looks indeed fairly sympathetic to the Heisenberg moral arguments that could be synthesized in a question that the German physicist asks twice on the stage: "Does one as a physicist have the moral right to work on the practical exploitation of atomic energy?" This is a still embarrassing question that could well suit several today burgeoning research fields: cloning, artificial intelligence, genetic manipulations, big data management ... A question, on the other hand, which is the source of the subsequent polemical exchange with Rose (see also his book earlier in the present list) which is instead a representative of another group of scholars rather un-sympathetic toward Heisenberg. Rose credits indeed the Copenhagen meeting of more sinister intentions (intelligence on the nazi behalf), while at the same time discrediting the German physicists for not achieving their own aims just because of sheer incompetence.

N.P. (Klaas) Landsman:
Getting even with Heisenberg
, Studies in History and Philosophy of Modern Physics 33 (2002) 297
This is a long and careful critical review of the previously referred book by P.L. Rose, with many details and remarks of his own that give to the author the opportunity of "getting even" with Heisenberg. His opinions look consequently rather fair and well balanced, and hence are not partisan or clearcut as that of many other scholars discussing these topics. 

Nicola Cufaro Petroni:
(March 2018; in italian)
In this file the chronologies of the main events of  World War II and both the (allied and german) nuclear programs are placed side by side up to the end of 1941 in order to elucidate the events predating the Bohr-Heisenberg meeting of September 16, 1941. Af few subsequent watershad dates are added to put the events in perspective. For the time being no pretense either of completeness or of total accuracy is made

Annex: Fake news?

Occasionally (and especially in our age of social news) journalists and historians bring to the fore sensationalistic details about the German bomb project to the effect of exposing, for instance, either that the German physicists were indeed far more advanced of what is generally believed, or that somehow their results were instrumental to complete the rival Manhattan Project. In our opinion all these new disclosures challenging the accepted narrative should be taken with a healthy measure of cautious skepticism, as argumented in the following few examples

1) On May 14, 1945, just after the end of the war in Europe, the German submarine U-234 surrendered to the USA in the Portsmouth Navy Yard. The fact that the submarine carried also about 540 Kg of Uranium oxide remained classified until the end of the Cold War and gave rise to speculations about the use of this material in the framework of a supposed shortage in the Manhattan Project. All this is said in particular in the DVD U-234 l'ultimo sommergibile produced by the Italian RAI for the series La storia siamo noi. As a matter of fact the precise characteristic of  the said Uranium remain unknown, it looks however unbelievable that the Germans could possess - without using - such a huge quantity (enough for ten Hiroshima bombs) of weapons grade Uranium: as we know, to separate a few Kg's of U-235 factories of industrial size are needed, and there is no known hint of that in the Nazi Germany. If on the other hand it was just not-enriched Uranium, half a ton is surely a valuable item, but again there was no real shortage of (not-enriched) Uranium for the Manhattan Project. We should remember indeed that there were four known major deposits of uranium in 1940: in Colorado, in northern Canada, in Joachimsthal in Czechoslovakia, and in the Belgian Congo. All but Joachimsthal were in allied hands. A November 1942 survey determined that sufficient quantities of uranium were available to satisfy the project's requirements. In particular a purchase of 1,200 tons (not just half a ton!) of uranium ore was negotiated from the Belgian Congo: it was being stored in a warehouse on Staten Island while the remaining stocks of mined ore were
stored in the Congo (see Wikipedia: Manhattan project, and references quoted therein).

2) In the same vein the Italian magazine L'Espresso published on October 27, 2016 a reportage by R. Brunelli: Hitler e il mistero della bomba di Hiroshima, mantaining that at the end of the war in Europe the nazi general Hans Kammler handed over to an American agent about 70 Kg of Uranium (again without qualification), that are finally hinted to be linked to the Hiroshima bomb just because of the supposed approximate coincidence of the two weights. The same remarks of the previous point apply even here, with the additional one that a supposed (slightly more than) critical mass of U-235 can not be simply tossed around in a suitcase because it would just ... explode: even if the German physicists had their calculations wrong!

3) A rather more reliable case is finally made in the book Hitlers bombe (Deutsche Verlags-Anstalt, 2005) by Rainer Karlsch: a summary can be found in
Rainer Karlsch and Martin Walker: New light on Hitler's bomb
The author mantains, on the basis of recently available russian archives, that the German physicists (in particular the group of Kurt Diebner) were much more advanced of what is usually believed, and that they developed and tested some kind of nuclear weapon: not, however, a standard nuclear weapon powered by nuclear fission, but something closer to either a radiological weapon (dirty bomb) or some hybrid nuclear fusion weapon (whatever that may mean). The alleged test was performed in Thuringia, eastern Germany, in March 1945: according to alleged eyewitness accounts given at the end of that month and two decades later, the test killed several hundred prisoners of war and concentration-camp inmates. However scrupulous in the details, even these revelations seem not really convincing: we read for instance on the Global Security web page

the following questioning lines:
The historian has no real proof to back up his spectacular theories. His witnesses either lack credibility or have no first-hand knowledge of the events described in the book. What Karlsch insists are key documents can, in truth, be interpreted in various ways, some of which contradict his theory. Finally, the soil sample readings taken thus far at the detonation sites provide "no indication of the explosion of an atomic bomb," says Gerald Kirchner of Germany's Federal Office for Radiation Protection. Joachim Schulze, a nuclear weapons expert at Germany's Fraunhofer Institute, took a look at Karlsch's design for such a weapon and said it would be "incapable of functioning."