Saturday, November 07, 2009

Questions for Dyson

I will be participating in a public Q&A session with Freeman Dyson later this term. Any reader of this blog will know that I'm an admirer of both his work in theoretical physics and his popular writing. (Related posts here.) In preparing for the event, I've been reading and re-reading all sorts of things by and about Dyson. Below is something I found quite striking:

Disturbing the Universe: ... In that spring of 1948 there was another memorable event. Hans [Bethe] received a small package from Japan containing the first two issues of a new physics journal. Progress of Theoretical Physics, published in Kyoto. The two issues were printed in English on brownish paper of poor quality. They contained a total of six short articles. The first article in issue No. 2 was called "On a Relativistically Invariant Formulation of the Quantum Theory of Wave Fields," by S. Tomonaga of Tokyo University. Underneath it was a footnote saying, "Translated from the paper . . . (1943) appeared originally in Japanese." Hans gave me the article to read. It contained, set out simply and lucidly without any mathematical elaboration, the central idea of Julian Schwinger's theory. The implications of this were astonishing. Somehow or other, amid the ruin and turmoil of the war, totally isolated from the rest of the world, Tomonaga had maintained in Japan a school of research in theoretical physics that was in some respects ahead of anything existing anywhere else at that time. He had pushed on alone and laid the foundations of the new quantum electrodynamics, five years before Schwinger and without any help from the Columbia experiments. He had not, in 1943, completed the theory and developed it as a practical tool. To Schwinger rightly belongs the credit for making the theory into a coherent mathematical structure. But Tomonaga had taken the first essential Step. There he was, in the spring of 1948, sitting amid the ashes and rubble of Tokyo and sending us that pathetic little package. It came to us as a voice out of the deep.

A few weeks later, Oppy received a personal letter from Tomonaga describing the more recent work of the Japanese physicists. They had been moving ahead fast in the same direction as Schwinger. Regular communications were soon established. Oppy invited Tomonaga to visit Princeton, and a succession of Tomonaga's students later came to work with us at Princeton and at Cornell. When I met Tomonaga for the first time, a letter to my parents recorded my immediate impression of him "He is more able than either Schwinger or Feynman to talk about ideas other than his own. And he has enough of his own too. He is an exceptionally unselfish person." On his table among the physics journals was a copy of the New Testament.

Ironically, Schweber, in his magisterial book QED and the Men Who Made It, advocates that Dyson deserved a share of the Nobel awarded to Feynman, Schwinger and Tomonaga, and somewhat downplays the role of Tomonaga.

Below are a list of questions I am considering for Dyson (I doubt he'll see it beforehand; does he read my blog? :-). Any suggestions are welcome!

You've written about how depressed you became over your war work analyzing Allied strategic bombing. Yet later you were a Jason, doing top secret military work for the US government. Could you talk about those two experiences, and your opinion about scientists working on weapons and advising the military?


Of the bomb designer turned disarmament activist Ted Taylor, who was the subject of a book called The Curve of Binding Energy, you once said "Very few people have Ted's imagination. ... I think he is perhaps the greatest man that I ever knew well. And he is completely unknown." Could you tell us more about Taylor?


You had a close association with many of the giants of the past -- Feynman, Dirac, Oppenheimer, Bethe. How do you compare them to the best people working today? Would they still be giants?


You advised Francis Crick, while he was still a physicist, that moving into biology might be premature. You thought that biology would eventually be more interesting than physics, but that Crick was too early. What would you be working on today if you were 25 years old?


You wrote that since childhood, some part of you had always known that the “Americans held the future in their hands and that the smart thing for me to do would be to join them.” Do Americans still hold the future in their hands, or will the future be made somewhere else -- for example in Asia or once again in Europe?


You've proposed that genetic engineering might be used for many purposes, from green energy to adapting humans for life in space. What about engineering ourselves for greater intelligence; could that be the next leap forward in human evolution?


You were at Princeton when Everett proposed his "Many Worlds" interpretation of quantum mechanics. Could you describe the reaction to his ideas then (including your own), and your present opinion? Any thoughts on the foundational questions of quantum mechanics?


How well did Feynman understand Second Quantization (or the idea of a quantum field) when he developed his approach to QED? At what point did he really understand the Schwinger / Tomonaga approach?


How much did Dirac understand about the path integral formulation of quantum mechanics before Feynman came along? Feynman was inspired by a formula in one of Dirac's papers, but has claimed that Dirac later acknowledged not knowing whether or how the analogy between amplitude and exponential of action could be made into an equality. Do you have any insight on this?

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