Brad Roth

May 1, 2020

5 min read

Faust in Copenhagen

Faust in Copenhagen, by Gino Segrè.

My friend and fellow biological physicist Gene Surdutovich loaned me his copy of Faust in Copenhagen: A Struggle for the Soul of Physics, by Gino Segrè. It’s about seven physicists- Niels Bohr, Max Delbrück, Paul Dirac, Paul Ehrenfest, Werner Heisenberg, Lise Meitner, and Wolfgang Pauli-who played a key role in the development of quantum mechanics in the 1920s. Segrè uses a 1932 meeting in Copenhagen as the hinge about which his story revolves.

This is a book about seven physicists, six men and one woman, who attended a small annual gathering in Copenhagen in April 1932. To be honest, only six of them were actually there. The seventh, Wolfgang Pauli, had originally intended to go, as he had in earlier years and would do so again, but he decided that spring instead to take a vacation. He was there in spirit, as you will see.

Of the seven, the one who plays the least significant role in the story is Delbrück. Nevertheless, he is the one most closely related to Intermediate Physics for Medicine and Biology. One topic I have examined in this blog is how scientists make the transition from physics to biology. Below I provide brief excerpts from Faust in Copenhagen, explaining how Delbrück did it. It appears in the book’s epilogue; I will add links and fill in background that you would have known had you read the rest of the book.

While working as the “family-theorist” in Meitner’s laboratory [in Berlin, she was the only experimental physicist of the seven], Delbrück often returned to see Bohr [his former mentor] and the continually changing group at Blegdamsvej [a street in Copenhagen where Bohr’s institute was located]. After the April 1932 meeting he had gone back to Berlin but in August was once again in Copenhagen. Sleepily stepping out of the carriage of the overnight train from Berlin, Delbrück was surprised to see Bohr’s trusted collaborator Leon Rosenfeld waiting for him with a message from Bohr. Delbrück was to go straightaway to the great meeting hall of the Rigsdag, the Danish parliament, where Bohr was about to deliver the opening lecture at the International Congress of Light Therapists… Knowing Delbrück’s interest in biology, Bohr wanted him to attend. This turned out to be the talk that changed Delbrück’s life [my italics].

In 1932 some biologists still clung to the notion that special forces not described by the ordinary laws of physics and chemistry were responsible for the existence of life… [In his talk, Bohr] asked: Could complementarity apply to life itself? [Complementarity was the principle that two opposing properties could both be true, but could not be observed simultaneously.] Perhaps the distinction between living and nonliving was not so easy to understand. Might the act of measurement be a critical step in the assessment [as it is in the Copenhagen interpretation of quantum mechanics]?…

Bohr thought there might be some intangible quality that differentiates living from nonlinving, a quality that could not be precisely quantified. He was not alluding to a divine spark, but rather to something analogous to the impossibility of saying with certainty whether light is a photon or a wave. Bohr’s conjecture was provocative, as it was meant to be, but in the end it turned out to be wrong. DNA and RNA are the answer to life, not complementarity.

But the potential connection between physics and biology had surfaced. Would Delbrück have become a biologist if he had not thought he might find something like complementarity at the root of life’s existence? Would molecular biology have developed as it did without the structure imposed on it by the discipline Delbrück had learned from Bohr? Many who know the field think the answer to both questions is no. When James Watson wrote Delbrück in 1953 that he and Francis Crick had found their double helix model of DNA, Delbrück was struck by the elegance of the structure, but disappointed by its simplicity. Hearing that life did not require any basic new principles, he remarked that if felt to him as if the hydrogen atom had been fully explained in the 1920s without the need for quantum mechanics. [The Bohr model explained the spectrum of hydrogen in 1913, but the more modern theory of quantum mechanics refined and improved that model in the 1920s.]

By then Delbrück had become a Bohr-life figure in the new field of molecular biology [Bohr, one of the senior members of the group of seven along with Ehrenfest and Meitner, was much loved as a mentor and father-figure as well as a scientist]. He had created at Cold Spring Harbor Laboratory on Long Island and at the California Institute of Technology Copenhagen-like atmospheres for young biologists…

[Delbrück], together with Salvador Luria and Alfred Hershey, with whom he shared the 1969 Nobel Prize in Physiology or Medicine, had shown how bacteriophages, the viruses that attack bacteria, were the simplest and most efficient tool for studying genetics… In many ways the importance of these findings were comparable to Bohr’s 1913 discovery of the rules for the hydrogen atom’s radiation…

Perhaps these qualities [of personality that are similar to Bohr’s, of integrity and intellectual openness] are the basis of the deep lifelong link between Pauli and Debrück. Luria, in his memoirs, remembered his first meeting with Delbrück. At the time both were recent refugees from Europe. It was New York City in late December 1941, only a few weeks after Pearl Harbor:

Max took me to dinner with two other scientists, one of them the great physicist Wolfgang Pauli. I was properly intimidated, but Pauli simply asked me “Sprechen Sie Deutsch?” and without waiting for a reply proceeded to eat and speak German so prodigiously fast that I understood not a word [of the seven, only Bohr (Danish) and Dirac (English) did not speak German as their first language]. I would have been even more scared had I known of Pauli’s classic remark “So young and he has already contributed so little.” [Pauli was known and loved for his quick and biting wit.]

Fortunately young Luria soon contributed a great deal.

As for Pauli, his last significant letter, written two months before he died, was a twelve-page one to Max. Beginning with a discussion of the festivities for Lise Meitner’s eightieth birthday, it ends on a more personal note: “I cannot forget the dear manner, which goes back to old times, when you took leave of me. I have the impression that here something has been renewed between us that is important.”

Delbrück would hike and camp with young biologists in the Southern California desert rather than walk with then along the North Sea shore of Denmark [where Bohr had walked with young Heisenberg, discussing quantum mechanics], but the spirit was the same as Bohr’s had been. On the other hand, rather than Bohr’s polite, “I don’t mean to criticize, only to understand,” Max remained famous for his rudeness… Though the spirit was Bohr’s, the style was Pauli’s…

Delbrück died in 1981 in California.

Looking for a good read while cooped up in your house because of the coronavirus? I recommend Faust in Copenhagen. It’s wunderbar.

Originally published at http://hobbieroth.blogspot.com.