Time, Quantum and Information, a paean to Professor Carl Friedrich von Weizsäcker, commemorates his 90th birthday. The range of Professor Weizsäcker's endeavours is an exhilarating example of what can be accomplished by one freely-soaring human spirit, who is at the same time a physicist, a philosopher, and a humanitarian.
The editors, Lutz Castell and Otfried Ischebeck, have assembled an admirable collection of essays and articles written by Weizsäcker's past students, collaborators, colleagues and acquaintances. Time, Quantum and Information offers the reader a panoply of unique insights into twentieth century science and history. Entangled with the stories about Weizsäcker's influence on the lives of some of the contributors are discussions of the activities of German scientists during and following World War II, emphasizing their reluctance to work on atomic weapons following the war. By outlining Weizsäcker's role in the early development of numerous tributaries of physical science, the book gives us a new glimpse into the origins of some of its disparate domains, such as nuclear physics, the physics of stellar nucleosynthesis, cosmic ray physics, fluid turbulence, and the formation of the solar system.
We physicists have all studied Weizsäcker's semi-empirical mass formula describing the binding energy of nuclei. We are aware too that both he and Hans Bethe independently discovered the nuclear cycles that provide stars with their enduring energy output. We have studied the Weizsäcker–Williams technique of calculating the bremsstrahlung of relativistic electrons. But how many of us know of Weizsäcker's work in fluid turbulence that he, like Werner Heisenberg under whom he had earned his doctorate, pursued while holed up in Farm Hall? And how many of us are aware of his introduction of turbulent viscosity to account for the origin of planetary orbits, involving the migration of mass inwards and angular momentum outwards? Moreover, before finally turning his attention to philosophy in 1957, Weizsäcker became interested in nuclear fusion research and educated a generation of postwar German physicists in both plasma physics and astrophysics.
Michael Frayn's play `Copenhagen' has ignited worldwide interest in the mysterious meeting of Niels Bohr with Werner Heisenberg in September 1941. However, an article by R Lüst indicates that in 1951 Bohr enjoyed a friendly visit with Heisenberg in Göttingen. This 1941 meeting of Heisenberg and Bohr is discussed further in an article by Götz Neuneck, who also details the World War II and post-war research and interests of the Uranium Club, a group of 70–100 German physicists and chemists. Neuneck also discusses the resistance of individual scientists, such as Hahn, Heisenberg, and Bothe, to the Nazi regime. We learn that, unlike Wernher von Braun, no member of the Uranium Club was ever granted an audience with Hitler. After the war, German scientists renounced any role for German development of nuclear weapons in various manifestos, such as the Mainau and G\"ottingen Declarations that were both influenced by Weizsäcker.
Time, Quantum and Information contains much anecdotal material. Examples include a touching quotation in a letter from Edward Teller to Weizsäcker: `If I could share your religious belief, I would wish that you will one day come from a higher heaven and visit me in purgatory.' Another example, less complimentary, is a comment from Pauli after hearing from Weisskopf that Weizsäcker had made numerous errors in his habilitation thesis and realizing that Weizsäcker had accepted an offer from Peter Debye at Berlin: `The measure of sloppiness in Weizsäcker's work exceeds altogether and by far the tolerable measure, and my pain of not having had him as an assistant has been alleviated by this.'
Two-thirds of this compendium also explores the philosophical interests of Weizsäcker. This portion discusses his attempt to reconstruct quantum mechanics and build up a `theory of everything' based on his `ur' hypothesis. As stated by the mathematician G G Emch in this book, `Philosophers and physicists often fail to understand each other because they are speaking different languages which often happen to have the same words.' These articles will have value to readers interested in these areas.
The inclusion of an index would have made the book much more useful. There are numerous minor typographical errors, the most amusing of which is the sign of the Coulomb energy of a uniform density sphere in the article by K v Meyenn. (The expression stated is -6(Ze)2/5R rather than the correct expression, 3(Ze)2/5R.) Another example is in the same article: when one looks for a reference to Jackson, #66, one finds instead a 1928 reference to Fermi!
Despite such inconvenient quirks, this book is essential reading for anyone interested in Weizsäcker and his research, in twentieth-century physics and physicists, and in unique insights into German science during and immediately following World War II.