Physics and Beyond: Encounters and Conversations
Physics went through a major revolution in the first quarter of this century. It was started by Max Planck and Niels Bohr, whose use of the idea of the quantum of action brought order into a wide range of phenomena concerning the structure of matter and the nature of atoms, but was as yet incomplete, in some parts arbitrary, and even self-contradictory. The final stage of this development, which completed our understanding of atomic physics, owes as much to Werner Heisenberg as to any other single person, although another development, started independently by Schrödinger, turned out to be a different expression of the same basic laws. Many others, of course, made important progress along the path opened up by the pioneers.
Heisenberg’s greatest contribution was to recognize that the contradictions of the old quantum theory were the result of asking questions to which there was no physically meaningful answer. Physics deals with observable phenomena, and in the atomic domain the indivisibility of particles and the existence of quanta put a limit to the accuracy of possible observations, if they are not to disturb unduly the very phenomenon under observation. The lesson was, therefore, to avoid asking questions about atoms to which no experiment could give an answer, and to express the laws of physics by reference to observable quantities. Heisenberg succeeded in carrying out his program, and the set of laws he arrived at form one of the starting points of modern theory.
Physics and Beyond is an account of his thoughts, including the ideas that led him to quantum mechanics; this part will be of absorbing interest to anyone interested in the history of physics. The book is not an autobiography: details of the author’s life are mentioned only where they are needed to provide the background to the thoughts and discussions, which are the real subject of the narrative.
The thoughts described are not, however, limited to physics and to the epistemological problems that were bound up with the beginnings of quantum mechanics, but range widely over philosophy and religion, reactions to life under the Nazis before and during the war, work on atomic energy, and the reorganization of German physics after the war. It seems to be a thesis of the book that attitudes toward the more abstract and the more concrete of these problems are interconnected. This is stressed in the title of the German original “The Part and the Whole” (Der Teil und das Ganze), which in translation has mysteriously, and to me rather disappointingly, become “Physics and Beyond.”
However, the nature of this connection is not spelled out, and the reader is left to find it for himself. Is there a recognizable connection between Heisenberg’s thoughts in very different fields? I find the answer to this question very elusive. Was he better able to see what accepted ideas of physics had to be discarded because he grew up in a postwar world in which young people were questioning accepted social …