“A Strange New Quantum Physics”Copenhagen. Michael Frayn. 132 pp. Methuen Publishing Ltd., 2000. $10.95.
“Copenhagen Tames Complexity of Science” was the title of a recent review of Michael Frayn’s latest play--meant, no doubt, as a compliment. Audiences in New York, where the play opened in April after a long run in London, do seem dazzled by the heady counterpoint of history, quantum mechanics and postmodern epistemology electrifying the air between the play’s characters--Werner Heisenberg, Niels Bohr and Bohr’s wife Margrethe. The play is quick, clever and artfully plotted. What’s disturbing is that Copenhagen “tames” history, too, altering the facts and rearranging the moral landscape the real Bohr and Heisenberg inhabited.
The subject of the play is Heisenberg’s famous September 1941 visit to Bohr in Nazi-occupied Denmark, an encounter the two men described very differently after the war. Bohr, according to family members, perceived Heisenberg’s visit as decidedly hostile, perhaps an attempt to pick his brain on the subject of fission or a probe for information on Allied research. Heisenberg maintained (to the Swiss-German journalist Robert Jungk) that he came simply to ask whether “as a physicist one had the moral right to work on the practical exploitation of atomic energy” and to offer reassurance that Germany was not building an atomic bomb. But Bohr, he said, misunderstood his good intentions and became alarmed. The two conflicting versions of the meeting encapsulate the 50-year-old controversy over Heisenberg’s wartime work for Germany.
Jungk expanded Heisenberg’s version into a full-blown legend of heroic resistance, Brighter Than a Thousand Suns (1958), which celebrated the supposed fact that “German nuclear physicists, living under a saber-rattling dictatorship, obeyed the voice of conscience and attempted to prevent the construction of atom bombs.” Jungk himself later disavowed this thesis when new information came to light (and Bohr, as Harvard historian Gerald Holton has discovered, composed--but never mailed--a letter to Heisenberg objecting in strong terms to the version of their visit Heisenberg had related to Jungk). But a new version of the resistance myth emerged in 1993 in Thomas Powers’s “shadow history” of the German atomic bomb project, Heisenberg’s War.
The revised edition of the text of Copenhagen that was published recently to coincide with the American production of the play includes an expanded postscript, from which we learn that Powers’s book was the inspiration for Frayn’s play and was effectively its sole source (Frayn’s broad bibliography notwithstanding). The Powers book won little respect from historians, as Frayn acknowledges, but it is not hard to see why a playwright’s professional radar would have responded to the book’s fiction-enhanced intrigue.
In Copenhagen, Heisenberg and Bohr are conceived as returning from beyond death to reenact their tense wartime meeting in a series of encounters, each a different imagining, or “draft,” of Heisenberg’s purpose. Now Heisenberg can try to convince Bohr of his good intentions, and Bohr can question and respond, all in a style that recalls their brilliant collaboration at Bohr’s institute in the 1920s, when together they explored the startling implications of the new quantum laws. Margrethe, throughout, serves as a one-woman chorus, skeptical of each of Heisenberg’s drafts, distrusting his relentless need to impress and to win, trying to puncture the moral pretensions she detects. We see the virtuous version Heisenberg gave to Jungk, and the Powers variation--that Heisenberg had possessed but withheld key knowledge of bomb physics: “I understood very clearly. I simply didn’t tell the others.” Margrethe suggests that his real object had been to obtain information about the Allies’ fission work and to persuade Bohr to discourage them.
The final and longest draft, Frayn’s favored invention, is staged to be the most compelling. More complexly heroic than in the Powers design, this Heisenberg has succeeded in forestalling a Nazi atomic bomb, both by withholding information about plutonium from arms minister Albert Speer and by refusing to interest himself in the most basic physics of atomic explosives--specifically, by not calculating the critical mass for a bomb. Had he but allowed himself to pause and do so, the final scene would have us believe (a nuclear explosion thunders offstage to dramatize the point), he would quickly have seen that a bomb could be built. This pseudoscientific fantasy is the play’s central pivot.
The celebration of uncertainty is a continuous theme in the play. Human life, like atomic physics, follows this quantum law described by Bohr: “that there is no precisely determinable objective universe. That the universe exists only as a series of approximations.” Thus, the play implies, no judgment of Heisenberg is possible, for all we can ever discover are the elusive, multiple refractions of his image in fallible memory. And this might be true in the ambiguous world Frayn has constructed, in which Bohr is unreliable and every disquieting revelation about Heisenberg is canceled by a nimble riposte. But quantum mechanics predicts that objects on a human scale obey classical laws of causality. The real Heisenberg lived in a world of cause and effect and uneasy moral compromise, and--the imperfect observability of the quantum universe notwithstanding--he left a trail of discoverable facts, facts that up-end the interpretation Frayn favors and discredit his portrait of Heisenberg.
Although Frayn’s play insists otherwise, we know that Heisenberg did calculate the critical mass for a bomb; in a 1939 secret report for the German Army Weapons Department, he first derived a formula that yields a mass in the hundreds of tons for the amount of “nearly pure” uranium 235 required for an exploding reactor (Heisenberg’s model for a bomb at that point). In 1940 Karl Wirtz heard him explain a further calculation; the details are known because Heisenberg explained them again on August 6, 7 and 9, 1945, while he was detained in England at Farm Hall, where hidden microphones captured his words. His simplified calculation used the random walk model Einstein had employed to derive mean diffusion distances in Brownian motion. Mistaken but plausible, it yielded a critical mass of tons, an amount still vastly beyond what Germany could hope to produce. That Heisenberg had not formulated the full three-dimensional fission-diffusion equations is hardly the lapse Frayn’s Bohr finds so inexplicable. The real Heisenberg did what working scientists do every day: He made a preliminary calculation, and when it yielded a mass so impracticably large, he saw no reason to spend weeks refining the estimate. That his calculation had hugely overestimated the critical mass he obviously didn’t realize, or he would not have displayed the result to his colleagues and continued trusting it until news of the Hiroshima bomb forced him to rethink. The order of magnitude agreed with published work, and with prevailing assumptions when the war began, so why would Heisenberg have doubted it? But to acknowledge this is to recognize that there is neither mystery nor virtue in his miscalculation, merely embarrassment--for Heisenberg, and for the play.
We also know something about Heisenberg’s handling of the plutonium “secret.” As proof that he had no wish to build weapons, Frayn’s Heisenberg cites his withholding from Speer in June 1942 the possibility that reactor-generated plutonium (element 94) might be used to make bombs. “A striking omission,” Frayn’s Bohr admits. But Heisenberg had made no secret of plutonium in February of that year, when he addressed the Nazi elite at a Berlin conference that Speer, Hermann Göring and Heinrich Himmler had been expected to attend: In the lecture he emphasized that a reactor could be used to generate “a new substance (element 94)... which in all probability is an explosive with the same unimaginable effectiveness as pure uranium 235.”
Also misleading is the play’s representation that as late as June 1942, German scientists were still “slightly ahead of Fermi in Chicago.” In fact, by the time of Heisenberg’s 1941 encounter with Bohr, Allied scientists were much closer to a bomb than were the Germans. At the time Heisenberg set out for Copenhagen in September 1941, the scientist in charge of Germany’s most promising uranium isotope separation project had just declared it a failure. Heisenberg’s reactor experiments had yet to demonstrate any neutron multiplication. Not even microscopic quantities of 235U or plutonium had been isolated, so no experiments to determine the fission properties relevant to a bomb had been done. Within a few months the head of research at the German Army Weapons Department would be contemplating cancellation of the German fission project.
Allied scientists at this time, by contrast, had already measured the fission properties of 235U and plutonium. Vannevar Bush was about to inform President Roosevelt that an atomic bomb could probably be built, with an estimated critical mass of 25 pounds. And Columbia physicists were two months away from demonstrating isotope separation by gaseous diffusion. By distorting the true relative standing of the two countries in this regard, the play suggests that if Heisenberg had succeeded in convincing Bohr that the Allies could safely abandon the pursuit of atomic weapons, all the world would have gained. But based on the facts as Heisenberg knew them, the beneficiary would have been a triumphant Germany, whose tanks, bombers and well-trained soldiers in September 1941 seemed poised to complete the conquest of Europe.
From the opening of the play Heisenberg presents himself as an embattled figure: “I wonder if they suspect for one moment how painful it was to get permission for the trip. The humiliating appeals to the Party, the demeaning efforts to have strings pulled.” Bohr tells how Heisenberg was subjected to “the most terrible attacks” as a “White Jew” for teaching Einstein’s theories, “how the SS brought him in for interrogation,” and how he remains under deep suspicion. “He knows he’s being watched, of course. He has to be careful about what he says.”
In order to keep alive the image of a Heisenberg at odds with the immorality around him, Frayn conceals the true contours of Heisenberg’s accommodation to the Nazi state. The audience is not told how, more than three years before the Copenhagen visit, Heisenberg had resolved his political problems by requesting and receiving an official letter placing him under the personal protection of Himmler, who was a family acquaintance. The fantastic suggestion that Heisenberg, a committed patriot, was involved in anti-Nazi activities squares with nothing in a lifetime of political conformity, including the statement of his wife that he “politely declined” when approached to join an anti-Hitler conspiracy. As for his visit to Copenhagen, the German Office of Cultural Propaganda had requested such a visit by Heisenberg and his colleague Carl Friedrich von Weizsäcker. This trip did require official clearance by the Nazi Party, as the play indicates, but this was easily arranged by Weizsäcker, whose father was State Secretary for Foreign Affairs. The propaganda office was sufficiently pleased with Heisenberg’s performance as an ambassador of Nazi culture to sponsor him on at least 10 such propaganda trips in the course of the war: to Nazi-occupied Budapest that same year, to Holland in 1943 just after its Jewish population had been dispatched to Auschwitz, and to Nazi-occupied Poland (as a guest of his friend the Governor General) not long after the Germans, by murder and siege and starvation, had annihilated the Warsaw Ghetto.
Copenhagen, with its simultaneous, often incompatible readings of Heisenberg’s mind, is designed to confront the audience with the impossibility of true knowledge, of others or of oneself. Yet it deploys every resource of stagecraft to elevate one view as truer than the rest. By the play’s elegiac conclusion, the audience has been led, through artful omission and misrepresentation of the historical record, to accept a thoroughly manipulated version of Heisenberg. This Heisenberg had discouraged pursuit of a bomb, had joined in anti-Nazi resistance that later rescued the Danish Jews, had nobly saved the life of a condemned man, had narrowly escaped death at the hands of the SS on his perilous journey home through Germany’s ruins at war’s end, and had “never managed to contribute to the death of one single solitary person.” Bohr, by contrast, is charged with complicity in the human disaster of Hiroshima and Nagasaki.
“If people are to be measured strictly in terms of observable quantities...,” Bohr begins, only to be interrupted by Heisenberg: “Then we should need a strange new quantum ethics. There’d be a place in heaven for me. And another one for the SS man I met on my way home.” So fast and so far does Frayn take us, this somehow is not meant to shock. Losing sight of the moral horizon can make you feel giddy--or sick.
Jonothan Logan, a physicist, first became acquainted with the records of the German fission project while archiving papers of Samuel Goudsmit, leader of the Allied mission investigating the project in World War II. More on Heisenberg and the atomic bomb can be found in Logan’ article “The Critical Mass” (May-June 1996)