Q&A: David C. Cassidy on history, playwriting, and Heisenberg

Following Germany’s defeat in World War II, British and American forces detained 10 German nuclear physicists at an estate in Britain called Farm Hall. The house’s temporary residents included Nobel Prize winners Otto Hahn, Max von Laue, and Werner Heisenberg. Unbeknownst to the physicists, Allied intelligence officers were recording their conversations, hoping to determine whether the Germans had been working on an atomic bomb—and if so, how close they had gotten.

Historian David C. Cassidy, author of the acclaimed Heisenberg biography Uncertainty: The Life and Science of Werner Heisenberg (1992) and its revised second edition, Beyond Uncertainty: Heisenberg, Quantum Physics, and the Bomb (2009), recently used the declassified Farm Hall transcripts to write a play, Farm Hall (see the Physics Today review of a 2013 script reading). His latest book, Farm Hall and the German Atomic Project of World War II: A Dramatic History, combines the play’s script with a brief historical narrative and some excerpts from the real Farm Hall transcripts. In the March issue of Physics Today, Mark Walker wrote that “Cassidy has made Farm Hall come alive, with all the important contradictions and conflicts it embodies.”

Physics Today caught up with Cassidy to talk about Heisenberg, Farm Hall, and the challenges of bringing historical events to the stage.

PT: How did you become interested in the history of physics, and how did you decide to make Heisenberg the subject of your dissertation?

CASSIDY: Astronomy and physics fascinated me from an early age and still do. At college I majored in physics while dabbling in literature, writing, and news reporting—much to the puzzlement of my classmates. As I progressed through my master’s degree in physics toward the doctorate, I grew increasingly restless. I enjoyed physics, but it did not come as naturally to me as it did to others, and the available research options seemed uninspiring and barely original.

Then I encountered Max Jammer’s pioneering 1966 book, The Conceptual Development of Quantum Mechanics. It opened a whole new world of the history of physics to me, a world of exciting research for which I felt a natural affinity. But I was at Purdue University, which had no program in the history of science. Through the generous support of several Purdue professors and Daniel M. Siegel, a historian of physics at the University of Wisconsin–Madison, the university agreed to accept a dissertation with Siegel as my outside adviser.

During visits with Thomas Kuhn at the Institute for Advanced Study in Princeton, I selected Heisenberg’s route to his 1925 breakthrough to quantum mechanics for my dissertation topic. As I hurried to learn German, I began studying Heisenberg’s papers and obtained copies of his early letters from an archive. Although I still had many lessons to learn, within six months of officially entering the field I was amazed to find myself doing original research on a nearly untouched topic. Nothing in physics could beat that.

PT: The Farm Hall transcripts weren’t declassified until the early 1990s. What was it like to read them for the first time after working on Heisenberg’s life and science for so many years?

CASSIDY: It was like a revelation. For that period, our historical sources had been letters, diaries, classified research reports, bureaucratic memos, and the like, but no actual conversations among the participants. Transcripts of seemingly unguarded conversations between 10 of the leading German fission scientists added an entirely new dimension to a history that encompassed the momentous transition to the atomic age in the period before, during, and after the atomic bombing of Japan. The transcripts brought to life their reactions to these events and enabled new insights into many of the lingering questions and controversies surrounding the German nuclear project, as well as the personal characteristics of these men.

But there were also disappointments. The German originals of most of the English translations are apparently lost, and the 153 pages of transcripts covered only a small fraction of the conversations during those six months of captivity.

PT: What inspired you to put the Farm Hall story on stage?

CASSIDY: As soon as the transcripts were released in 1992, it occurred to me and many others that they could be the basis for a theatrical play. But I was drawn into the controversies raised or revived both by the transcripts and later by Michael Frayn’s popular 1998 play, Copenhagen. So I left it to others to struggle with the dynamics of playwriting.

Then in 2007 I ran into physicist Brian Schwartz during an American Physical Society meeting in Jacksonville, Florida. He pointed out that it had been 15 years since the release of the transcripts, and no one had yet created a successful play. He suggested that I should make the attempt. At the time I knew practically nothing about playwriting. But since I had recently completed my biography of J. Robert Oppenheimer and had not yet settled on a new topic, I decided to give it a try.

It turned into another career phase transition which, like my earlier transition from physics to history, required learning many new methods, goals, rules, and technical details. But I enjoyed playwriting and discovered that I had some talent for it. With a lot of study and the patient help of dramatists and others, especially Break a Leg Productions in New York, the play gradually emerged onto the stage seven years later.

PT: Who was the most challenging historical figure to bring to life in the play?

CASSIDY: In the play I reduced the number of German scientists from 10 to 5 so they could be easily distinguished individually and engage in clearer dramatic conflicts. Each character was difficult, but Heisenberg was the most challenging. He was a man walking a fine line in a very difficult situation for which he was completely unprepared. All of these scientists, but Heisenberg especially, saw themselves as highly successful in fission research. The Hiroshima bomb shattered those illusions and created a crisis for them all.

As the scientists faced their shortcomings in comparison with the Allied effort and grappled with the implications of their fission research under the German regime at war, Heisenberg had to face the additional failures of his initial inability to understand the bomb physics and his meager response to the arrest of physicist Samuel Goudsmit’s Jewish parents in the Netherlands. Presenting all of this while rendering Heisenberg as neither a hero nor a villain, but as the complex human being somewhere in between that he was, became a challenge both in the play and in the biography.

PT: What are you working on right now?

CASSIDY: I’m preparing to submit the final manuscript of a book to MIT Press that I have been coauthoring for several years with Allen Esterson, with a contribution by Ruth Lewin Sime, titled Einstein’s Wife: The Story of Mileva Einstein-Marić. At the same time, I have been working on a parallel play, The Relativity of Love: Albert Einstein and Mileva Marić.

PT: What are you currently reading?

CASSIDY: The Glass Menagerie by Tennessee Williams, a play in which one of the main characters also has a major part as the narrator. I am studying how Williams did this because my dramatist colleagues tell me that my attempts to use a narrator since Farm Hall have not worked as I had hoped. In Farm Hall, Major T. H. Rittner, a British military officer, serves as both a catalyst and the narrator in the main part of the play. I am now thinking of making even greater use of a participant–narrator for a possible future play about Chien-Shiung Wu, the experimentalist who confirmed the nonconservation of parity. A close colleague or her husband, who was also a physicist, could possibly take on this dual role.

For more on Heisenberg and Farm Hall, read the special section in the August 1995 issue of Physics Today, which includes an article by Cassidy and Jeremy Bernstein.